MECHANISM-PARAMETER-CALIBRATION METHOD FOR ROBOTIC ARM SYSTEM

Abstract

A mechanism-parametric-calibration method for a robotic arm system is provided. The method includes controlling the robotic arm to perform a plurality of actions so that one end of the robotic arm moves toward corresponding predictive positioning-points; determining a predictive relative-displacement between each two of the predictive positioning-points; after the robotic arm performs each of the actions, sensing three-dimensional positioning information of the end of the robotic arm; determining, according to the three-dimensional positioning information, a measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the actions; deriving an equation corresponding to the robotic arm from the predictive relative-displacements and the measured relative-displacements; and utilizing a feasible algorithm to find the solution of the equation.

Claims

1. A mechanism-parametric-calibration method for a robotic arm system, wherein the robotic arm system comprises a robotic arm and a measuring instrument, and the mechanism-parametric-calibration method comprises: controlling, according to n mechanism parameter sets, the robotic arm performing n actions so that an end of the robotic arm moves toward n corresponding predictive positioning-points; determining a predictive relative-displacement equation of each two of the n predictive positioning-points; sensing, using the measuring instrument, three-dimensional measured positioning-points corresponding to the end of the robotic arm after the robotic arm performs each of the n actions; determining, according to the n three-dimensional measured positioning-points, a measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the n actions; deriving an optimization equation corresponding to the robotic arm from the predictive relative-displacement equations and the measured relative-displacements; obtaining, by the optimization equation, a set of mechanism parametric deviations of the robotic arm; and calibrating, by the set of mechanism parametric deviations, the n mechanism parameter sets of the robotic arm.

2. The mechanism-parametric-calibration method as claimed in claim 1, wherein the optimization equation is $\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\underset{i=1}{\overset{n-1}{.Math.}}.Math.\underset{j=i+1}{\overset{n}{.Math.}}.Math.{\left(\Delta .Math..Math.M_{i,j}-G\left(S_i,S_j,\Delta .Math..Math.S\right)\right)}^2;$ and wherein ΔM.sub.i,j is the measured relative-displacement, G(S.sub.i, S.sub.j, ΔS) is the predictive relative-displacement equation, S.sub.i and S.sub.j are the mechanism parameter sets, and ΔS is the set of mechanism parametric deviations.

3. A mechanism-parametric-calibration method for a robotic arm system, the robotic arm system comprising a robotic arm, a calibration block and a measuring instrument, wherein the mechanism-parametric-calibration method comprises: controlling, according to nx mechanism parameter sets corresponding to nx first-direction predictive positioning-points, the robotic arm performing nx actions such that an end of the robotic arm moves toward the nx first-direction predictive positioning-points which are in front of a first precision plane of the calibration block, wherein the first precision plane is perpendicular to a first direction; sensing, using the measuring instrument, a first-direction measured displacement between the first precision plane and the end of the robotic arm when the robotic arm performs each of the nx actions; determining, according to the nx first-direction measured displacement, a first-direction measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the nx actions; determining a first-direction predictive relative-displacement equation of each two of the nx first-direction predictive positioning-points; deriving an optimization equation corresponding to the robotic arm from the first-direction predictive relative-displacement equations and the first-direction measured relative-displacements; obtaining, by the optimization equation, a set of mechanism parametric deviations of the robotic arm; and calibrating, by the set of mechanism parametric deviations, the nx mechanism parameter sets corresponding to the nx first-direction predictive positioning-points of the robotic arm.

4. The mechanism-parametric-calibration method as claimed in claim 3, further comprising: when a first-direction pitch between an out-of-range first-direction predictive positioning-point and the first precision plane exceeds a maximum sensing distance of the measuring instrument in the first direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range first-direction predictive positioning-point which is in front of a second precision plane of the calibration block to sense the first-direction measured displacement between the end of the robotic arm and the second precision plane, wherein the second precision plane is perpendicular to the first direction; and determining the first-direction measured relative-displacements according to a first-direction displacement parameter and the first-direction measured displacements, wherein the first precision plane and the second precision plane are the first-direction displacement parameter apart.

5. The mechanism-parametric-calibration method as claimed in claim 3, wherein the optimization equation is $\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2;$ and wherein ΔxMx.sub.i,j is the first-direction measured relative-displacement, g.sub.x(xS.sub.i, xS.sub.j, ΔS) is the first-direction predictive relative-displacement equation, xS.sub.i, and xS.sub.j are the mechanism parameter sets corresponding to the first-direction predictive positioning-points, and ΔS is the set of mechanism parametric deviations.

6. The mechanism-parametric-calibration method as claimed in claim 3, further comprising: controlling, according to ny mechanism parameter sets corresponding to ny second-direction predictive positioning-points, the robotic arm performing ny actions so that the end of the robotic arm moves toward the ny second-direction predictive positioning-points which are in front of a third precision plane of the calibration block, wherein the third precision plane is perpendicular to a second direction; sensing, using the measuring instrument, a second-direction measured displacement between the third precision plane and the end of the robotic arm when the robotic arm performs each of the ny actions; determining, according to the ny second-direction measured displacement, a second-direction measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the ny actions; determining a second-direction predictive relative-displacement equation of each two of the ny second-direction predictive positioning-points; and deriving the optimization equation corresponding to the robotic arm from the first-direction predictive relative-displacement equations, the first-direction measured relative-displacements, the second-direction predictive relative-displacement equations and the second-direction measured relative-displacements.

7. The mechanism-parametric-calibration method as claimed in claim 6, wherein the optimization equation is $\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\left\{\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{ny}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{ny}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{yMy}}_{i,j}-g_x\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\right)}^2\right\};$ and wherein ΔxMx.sub.i,j, is the first-direction measured relative-displacement, g.sub.x(xS.sub.i, xS.sub.j, ΔS) is the first-direction predictive relative-displacement equation, xS.sub.i and xS.sub.jare the mechanism parameter sets corresponding to the first-direction predictive positioning-points, ΔyMy.sub.i,j is the second-direction measured relative-displacement, g.sub.y(yS.sub.i, yS.sub.j, ΔS) is the second-direction predictive relative-displacement equation, yS.sub.i and yS .sub.jare the mechanism parameter sets corresponding to the second-direction predictive positioning-points, and ΔS is the set of mechanism parametric deviations.

8. The mechanism-parametric-calibration method as claimed in claim 6, further comprising: when a first-direction pitch between an out-of-range first-direction predictive positioning-point and the first precision plane exceeds the maximum sensing distance of the measuring instrument in the first direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range first-direction predictive positioning-point which is in front of a second precision plane of the calibration block to sense the first-direction measured displacement between the end of the robotic arm and the second precision plane, wherein the second precision plane is perpendicular to the first direction; when a second-direction pitch between an out-of-range second-direction predictive positioning-point and the third precision plane exceeds the maximum sensing distance of the measuring instrument in the second direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range second-direction predictive positioning-point which is in front of a fourth precision plane of the calibration block to sense the second-direction measured displacement between the end of the robotic arm and the fourth precision plane, wherein the fourth precision plane is perpendicular to the second direction; determining the first-direction measured relative-displacements according to a first-direction displacement parameter and the first-direction measured displacements; and determining the second-direction measured relative-displacements according to a second-direction displacement parameter and the second-direction measured displacements, wherein the first precision plane and the second precision plane are the first-direction displacement parameter apart; and wherein the third precision plane and the fourth precision plane are the second-direction displacement parameter apart.

9. The mechanism-parametric-calibration method as claimed in claim 3, further comprising: controlling, according to ny mechanism parameter sets corresponding to ny second-direction predictive positioning-points, the robotic arm performing ny actions so the end of the robotic arm moves toward the ny second-direction predictive positioning-points which are in front of a third precision plane of the calibration block, wherein the third precision plane is perpendicular to the second direction; controlling, according to nz mechanism parameter sets corresponding to nz third-direction predictive positioning-points, the robotic arm performing nz actions so the end of the robotic arm moves toward the nz third-direction predictive positioning-points which are in front of a fifth precision plane of the calibration block, wherein the fifth precision plane is perpendicular to a third direction; sensing, using the measuring instrument, a second-direction measured displacement between the third precision plane and the end of the robotic arm when the robotic arm performs each of the ny actions; determining, according to the ny second-direction measured displacements, a second-direction measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the ny actions; sensing, using the measuring instrument, a third-direction measured displacement between the fifth precision plane and the end of the robotic arm when the robotic arm performs each of the nz actions; determining, according to the nz third-direction measured displacement, a third-direction measured relative-displacement moved by the end of the robotic arm when the robotic arm performs each two of the nz actions; determining a second-direction predictive relative-displacement equation of each two of the ny second-direction predictive positioning-points and determining a third-direction predictive relative-displacement equation of each two of the nz third-direction predictive positioning-points; and deriving the optimization equation corresponding to the robotic arm from the first-direction predictive relative-displacement equations, the first-direction measured relative-displacements, the second-direction predictive relative-displacement equations, the second-direction measured relative-displacements, the third-direction predictive relative-displacement equations and the third-direction measured relative-displacements.

10. The mechanism-parametric-calibration method as claimed in claim 9, wherein the optimization equation is $\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\left\{\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{ny}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{ny}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{yMy}}_{i,j}-g_y\left(y.Math..Math.S_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{nz}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nz}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{zMz}}_{i,j}-g_z\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)\right)}^2\right\};$ and wherein ΔxMx.sub.i,j is the first-direction measured relative-displacement, g.sub.x(xS.sub.i, xS.sub.j, ΔS) is the first-direction predictive relative-displacement equation, xS.sub.i and xS.sub.j are the mechanism parameter sets corresponding to the first-direction predictive positioning-points, ΔyMy.sub.i,j is the second-direction measured relative-displacement, g.sub.y(yS.sub.i, yS.sub.j, ΔS) is the second-direction predictive relative-displacement equation, yS.sub.i and yS.sub.j are the mechanism parameter sets corresponding to the second-direction predictive positioning-points, ΔzMz.sub.i,j is the third-direction measured relative-displacement, g.sub.z(zS.sub.i, zS.sub.j, ΔS) is the third-direction predictive relative-displacement equation, zS.sub.i and zS.sub.j are the mechanism parameter sets corresponding to the third-direction predictive positioning-points, and ΔS is the set of mechanism parametric deviations.

11. The mechanism-parametric-calibration method as claimed in claim 9, further comprising: when a first-direction pitch between an out-of-range first-direction predictive positioning-point and the first precision plane exceeds the maximum sensing distance of the measuring instrument in the first direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range first-direction predictive positioning-point which is in front of a second precision plane of the calibration block to sense the first-direction measured displacement between the end of the robotic arm and the second precision plane, wherein the second precision plane is perpendicular to the first direction; when a second-direction pitch between an out-of-range second-direction predictive positioning-point and the third precision plane exceeds the maximum sensing distance of the measuring instrument in the second direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range second-direction predictive positioning-point which is in front of a fourth precision plane of the calibration block to sense the second-direction measured displacement between the end of the robotic arm and the fourth precision plane, wherein the fourth precision plane is perpendicular to the second direction; when a third-direction pitch between an out-of-range third-direction predictive positioning-point and the fifth precision plane exceeds the maximum sensing distance of the measuring instrument in the third direction, controlling the robotic arm so that the end of the robotic arm moves toward the out-of-range third-direction predictive positioning-point which is in front of a sixth precision plane of the calibration block to sense the third-direction measured displacement between the end of the robotic arm and the sixth precision plane, wherein the sixth precision plane is perpendicular to the third direction; determining the first-direction measured relative-displacements according to a first-direction displacement parameter and the first-direction measured displacements; and determining the second-direction measured relative-displacements according to a second-direction displacement parameter and the second-direction measured displacements; and determining the third-direction measured relative-displacements according to a third-direction displacement parameter and the third-direction measured displacements, wherein the first precision plane and the second precision plane are the first-direction displacement parameter apart; wherein the third precision plane and the fourth precision plane are the second-direction displacement parameter apart; and wherein the fifth precision plane and the sixth precision plane are the third-direction displacement parameter apart.

12. The mechanism-parametric-calibration method as claimed in claim 3, wherein the measuring instrument comprises a measuring instrument used for sensing one-dimensional displacements, a measuring instrument used for sensing two-dimensional displacements, or a measuring instrument used for sensing three-dimensional displacements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present disclosure can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

[0022] FIG. 1 is a schematic diagram of the robotic arm system 10.

[0023] FIG. 2 is a system configuration diagram of a robotic arm system 20 according to an embodiment of the present disclosure.

[0024] FIG. 3 shows a flow diagram illustrating a mechanism-parametric-calibration method for the robotic arm system 20.

[0025] FIG. 4 is a system configuration diagram of a robotic arm system 40 according to an embodiment of the present disclosure.

[0026] FIG. 5 illustrates that how a robotic arm system 50 measures first-direction measured relative-displacements ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx corresponding to the first-direction predictive positioning-points, second-direction measured relative-displacements ΔyMy.sub.i,j, i=1, . . . , ny−1,j=i+1, . . . , ny corresponding to the second-direction predictive positioning-points, and third-direction measured relative-displacements ΔzMz.sub.i,j, i=1, . . . , ny−1,j=i+1, . . . , nz corresponding to the third-direction predictive positioning-points according to an embodiment of the present disclosure.

[0027] FIG. 6 illustrates how the robotic system 50 measures the first-direction measured relative-displacements ΔxMx.sub.i,1, i=1, . . . , 4,j=i+1, . . . , 5 corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.5 according to an embodiment of the present disclosure.

[0028] FIG. 7 illustrates how the robotic system 50 measures the second-direction measured relative-displacements ΔyMy.sub.i,ji=, . . . , 3,j=i+1, . . . , 4 corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.4 according to an embodiment of the present disclosure.

[0029] FIGS. 8A-8E show a flow diagram illustrating a mechanism-parametric-calibration method for the robotic arm system 40.

DETAILED DESCRIPTION

[0030] The following description is of the best-contemplated mode of carrying out the present disclosure. This description is made for the purpose of illustrating the general principles of the present disclosure and should not be taken in a limiting sense. The scope of the present disclosure is best determined by reference to the appended claims

[0031] Terms used in this disclosure:

[0032] P˜predictive positioning-point of the mathematical model

[0033] S˜mechanism parameter set

[0034] N˜absolute measured positioning-point

[0035] ΔP˜position deviation

[0036] ΔS˜set of mechanism parametric deviations

[0037] P.sub.k, k=1, . . . , n˜predictive positioning-points

[0038] S.sub.k, k=1, . . . , n˜mechanism parameter sets corresponding to the predictive positioning-points

[0039] ΔP.sub.i,j, i=1, . . . , n−1, j=i+1, . . . , n˜predictive relative-displacement

[0040] M.sub.k, k=1, . . . , n ˜three-dimensional measured positioning-point

[0041] ΔM.sub.i,j, i=1, . . . , n−1,j=i+1, . . . , n˜measured relative-displacement

[0042] G(S.sub.i, S.sub.j, ΔS)˜predictive relative-displacement equation

[0043] g.sub.x(S.sub.i, S.sub.j, ΔS)˜first-direction predictive relative-displacement equation

[0044] g.sub.y(S.sub.i, S.sub.j, ΔS)˜second-direction predictive relative-displacement equation

[0045] g.sub.z(S.sub.i, S.sub.j, ΔS)˜third-direction predictive relative-displacement

[0046] xS.sub.k, k=1, . . . , nx˜mechanism parameter sets corresponding to the first-direction predictive positioning-points

[0047] yS.sub.k, k=1, . . . , ny˜mechanism parameter sets corresponding to the second-direction predictive positioning-points

[0048] zS.sub.k, k=1, . . . , nz˜mechanism parameter sets corresponding to the third-direction predictive positioning-points

[0049] xP.sub.k, k=1, . . . , nx˜first-direction predictive positioning-points

[0050] yP.sub.k, k=1, . . . , ny˜second-direction predictive positioning-points

[0051] zP.sub.k, k=1, . . . , nz˜third-direction predictive positioning-points

[0052] ΔxP.sub.i,j, i=1, . . . , nx−1, j=i+1, . . . , nx˜first-direction predictive relative-displacement

[0053] ΔyP.sub.i,j, i=1, . . . , ny−1, j=i+1, y−1,˜second-direction predictive relative-displacement

[0054] ΔzP.sub.i,j, i=1, . . . , nz−1, j=i+1, z−1,˜third-direction predictive relative-displacement

[0055] G(xS.sub.i, xS.sub.j, ΔS)˜three-dimensional predictive relative displacement equation corresponding to the first-direction predictive positioning-points

[0056] g.sub.x(xS.sub.i, xS.sub.j, ΔS)˜first-direction predictive relative-displacement equations corresponding to the first-direction predictive positioning-points

[0057] g.sub.y(xS.sub.i, xS.sub.j, ΔS)˜second direction predictive relative-displacement equations corresponding to the first-direction predictive positioning-points

[0058] g.sub.z(xS.sub.i, xS.sub.j, ΔS)˜third direction predictive relative-displacement equations corresponding to the first-direction predictive positioning-points

[0059] G(yS.sub.i, yS.sub.j, ΔS)˜three-dimensional predictive relative-displacement equation corresponding to the second-direction predictive positioning-points

[0060] g.sub.x(yS.sub.i, yS.sub.j, ΔS)˜first-direction predictive relative-displacement equations corresponding to the second-direction predictive positioning-points

[0061] g.sub.y(yS.sub.i, yS .sub.j, ΔS)˜second-direction predictive relative-displacement equations corresponding to the second-direction predictive positioning-points

[0062] g.sub.z(yS.sub.i, yS.sub.j, ΔS)˜third-direction predictive relative-displacement equations corresponding to the second-direction predictive positioning-points

[0063] G(zS.sub.i, zS.sub.j, ΔS)˜three-dimensional predictive relative-displacement equation corresponding to the third-direction predictive positioning-points

[0064] g.sub.x(zS.sub.i,zS.sub.j, ΔS)˜first-direction predictive relative-displacement equations corresponding to the third-direction predictive positioning-points

[0065] g.sub.y(zS.sub.i, zS.sub.j, ΔS)˜second-direction predictive relative-displacement equations corresponding to the third-direction predictive positioning-points

[0066] g.sub.z(zS.sub.i, zS.sub.j, ΔS)˜third-direction predictive relative-displacement equations corresponding to the third-direction predictive positioning-points

[0067] ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx˜first-direction measured relative-displacement corresponding to the first-direction predictive positioning-points xP.sub.i and xP.sub.j

[0068] ΔyMy.sub.i,j, i=1, . . . , ny−1, j=i+1, . . . , ny˜second-direction measured relative-displacements corresponding to the second-direction predictive positioning-points yP.sub.i and yP.sub.j

[0069] AzMz.sub.i,j, i=1, . . . , nz−1, j=i+1, . . . , nz˜third-direction measured relative-displacements corresponding to the second-direction predictive positioning-points zP.sub.i and zP.sub.j

[0070] xMx.sub.k, k=1, . . . , nx˜first-direction measured displacement

[0071] yMy.sub.k, k=1, . . . , ny˜second-direction measured displacement

[0072] zMz.sub.k, k=1, . . . , nz˜third-direction measured displacement

[0073] Dx,Dy,Dz˜first-direction displacement parameter, second-direction displacement parameter, third-direction displacement parameter

[0074] FIG. 2 is a system configuration diagram of a robotic arm system 20 according to an embodiment of the present disclosure. In FIG. 2, the robotic arm system 20 comprises a robotic arm 21, a base 22, a storage unit 23, a processing unit 24 and a measuring instrument 25. The robotic arm 21 is disposed on the base 22 and electrically connected to the processing unit 24.

[0075] In FIG. 2, assuming a calibrated mathematical model of the robotic arm 21 is represented below:

P≡F(S+ΔS)

[0076] Wherein the mechanism parameter set S is, but not limited thereto, a set of the size (arm length) of mechanical links, the connection orientations and angles between joint axes, the amount of joint variables, and other geometric variables of the robotic arm 21, and the set of mechanism parametric deviations ΔS is prepared for compensating for the mechanism parameter set S after calibration.

[0077] In FIG. 2, the storage unit 23 is used to store a plurality of mechanism parameter sets S.sub.k, k=1, . . . , n (S.sub.1˜S.sub.n). Corresponding predictive positioning-points P.sub.k, k=1, . . . , n (P.sub.1˜P.sub.n) are obtained by substituting the mechanism parameter set S.sub.k into the calibrated mathematical model F(S+ΔS) of the robotic arm 21 and can be represented below:

P.sub.k≡F(S.sub.k+ΔS), k=1, . . . , n

[0078] Wherein the mechanism parameter sets S.sub.1˜S.sub.n comprise the size (arm length) of mechanical links, the connection orientations and angles between joint axes, the amount of joint variables, and other geometric variables.

[0079] In FIG. 2, the processing unit 24 comprises a calibrating calculation unit 241 and a control unit 242. The processing unit 24 is electrically connected to the storage unit 23. The control unit 242 of the processing unit 24 controls the robotic arm 21 performing a plurality of actions so that an end of the robotic arm 21 moves toward corresponding predictive positioning-points P.sub.1˜P.sub.n. E.g. the control unit 242 of the processing unit 24 performs an action according to a specific mechanism parameter set S.sub.k so the end of the robotic arm 21 moves toward a specific corresponding predictive positioning-point P.sub.k. In FIG. 2, the calibrating calculation unit 241 of the processing unit 24 further determines a predictive relative-displacement ΔP.sub.i,j which is between each two of the predictive positioning-points P.sub.1˜P.sub.n.

[0080] In FIG. 2, the two predictive positioning-points P.sub.i and P.sub.j are respectively represented as P.sub.i≡F(S.sub.i+ΔS) and P.sub.j≡F(S.sub.i+ΔS) , and a predictive relative-displacement equation G(S.sub.i, S.sub.j, ΔS) between the two predictive positioning-points P.sub.i and P.sub.j is represented below:

[00003]$\begin{array}{cc}\begin{array}{c}\Delta .Math..Math.P_{i,j}=.Math.P_j-P_i\\ =.Math.F\left(S_j+\Delta .Math..Math.S\right)-F\left(S_i+\Delta .Math..Math.S\right)\\ =.Math.G\left(S_i,S_j,\Delta .Math..Math.S\right),\end{array}& \\ i=1,\mathrm{.Math.}.Math.,n-1,j=i+1,\mathrm{.Math.}.Math.,n& \end{array}$

[0081] In FIG. 2, the measuring instrument 25 is electrically connected to the processing unit 24. The measuring instrument 25 is used to measure three-dimensional positioning information corresponding to the end of the robotic arm 21 while the robotic arm 21 performing each of the actions. The calibrating calculation unit 241 of the processing unit 24 determines, according to the three-dimensional positioning information, a measured relative-displacement ΔM.sub.i,j moved by the end of the robotic arm 21 while performing each two of the actions. Then the calibrating calculation unit 241 of the processing unit 24 obtains an optimization equation Φ corresponding to the robotic arm 21 according to the predictive relative-displacement equations G(S.sub.i, S.sub.j, ΔS) and the measured relative-displacements ΔM.sub.i,j.

[0082] In FIG. 2, the measuring instrument 25 measures three-dimensional measured positioning-points M.sub.k, k=1, . . . , n (M.sub.1˜M.sub.n) corresponding to the end of the robotic arm 21 while the robotic arm 21 performing each of the actions. The calibrating calculation unit 241 of the processing unit 24 determines the measured relative-displacement ΔM.sub.i,j between each two of the three-dimensional measured positioning-points M.sub.1˜M.sub.n. In FIG. 2, the measured relative-displacement ΔM.sub.i,j corresponding to two predictive positioning-points P.sub.i and P.sub.j is represented below:

ΔM.sub.i,j=M.sub.j−M.sub.i, i=1,j=i+1, . . . , n

[0083] That is, the three-dimensional positioning information includes the three-dimensional measured positioning-points M.sub.1˜M.sub.n and the measured relative-displacements ΔM.sub.i,j.

[0084] In FIG. 2, the measuring instrument 25 can be a coordinate-measuring machine or a laser tracker which performs spatial positioning measurement. Because the processing unit 24 only requires the measured relative-displacement ΔM.sub.i,j corresponding to two predictive positioning-points P.sub.i and P.sub.j, the choices of the measuring instrument 25 are not limited to an absolute positioning measuring instrument. The measuring instrument 25 can also be a contact instrument or a non-contact instrument which performs spatial positioning measurements.

[0085] Then the calibrating calculation unit 241 of the processing unit 24 calculates the optimization equation Φ corresponding to the robotic arm 21 according to the predictive relative-displacement equations G(S.sub.i, S.sub.j, ΔS) and the measured relative-displacements ΔM.sub.i,j and the optimization equation Φ is represented below:

[00004]$\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\underset{i=1}{\overset{n-1}{.Math.}}.Math.\underset{j=i+1}{\overset{n}{.Math.}}.Math.{\left(\Delta .Math..Math.M_{i,j}-G\left(S_i,S_j,\Delta .Math..Math.S\right)\right)}^2$

[0086] Then the processing unit 24 of the robotic arm system 20 utilizes an optimization algorithm and the optimization equation Φ to obtain a set of mechanism parametric deviations ΔS. Finally, the processing unit 24 of the robotic arm system 20 uses the set of mechanism parametric deviations ΔS to calibrate the mechanism parameter sets S.sub.1˜S.sub.n of the robotic arm 21.

[0087] It should be noted that, among the choices of the optimization algorithm of the robotic arm system 20, the processing unit 24 can be adopted an optimization algorithm with a non-linear equation. Because the predictive relative-displacement equation G(S.sub.i, S.sub.j, ΔS) used for calculating the predictive relative-displacement ΔP.sub.i,j, of the robotic arm 21 is almost equivalent to the robot non-linear mathematical model, the approximation error of the predictive relative-displacement equation G(S.sub.i, S.sub.j, ΔS) is extremely small. Accordingly, the optimization convergence effect of the set of mechanism parametric deviations ΔS obtained by the optimization equation Φ of the robotic arm system 20 is greater than the optimization convergence effect of the set of mechanism parametric deviations ΔS obtained by the optimization equation Φ of the robotic arm system 10.

[0088] FIG. 3 shows a flow diagram illustrating a mechanism-parametric-calibration method for the robotic arm system 20. In step S301, the processing unit 24 of the robotic arm system 20 controls, according to a plurality of mechanism parameter sets S.sub.k, k=1, . . . , n (S.sub.1˜S.sub.n), the robotic arm 21 to perform a plurality of actions so that the end of the robotic arm 21 moves toward a plurality of corresponding predictive positioning-points P.sub.1˜P.sub.n. In step S302, the processing unit 24 of the robotic arm system 20 determines a predictive relative-displacement ΔP.sub.i,j=G(S.sub.i, S.sub.j, ΔS) between each two of the predictive positioning-points P.sub.1˜P.sub.n. In step S303, the measuring instrument 25 measures three-dimensional measured positioning-points M.sub.k, k=1, . . . , n (M.sub.1˜M.sub.n) corresponding to the end of the robotic arm 21 while the robotic arm 21 performing each of the actions. In step S304, the processing unit 24 of the robotic arm system 20 determines, according to the three-dimensional measured positioning-points M.sub.1˜M.sub.n, a measured relative-displacement ΔM.sub.i,j moved by the end of the robotic arm 21 while the robotic arm 21 performing each two of the actions. In step S305, the processing unit 24 of the robotic arm system 20 obtains an optimization equation Φ corresponding to the robotic arm 21 according to the predictive relative-displacement equations G(S.sub.i, S.sub.j, ΔS) and the measured relative-displacements ΔM.sub.i,j. In step S306, the processing unit 24 of the robotic arm system 20 utilizes an optimization algorithm and the optimization equation Φ to obtain a set of mechanism parametric deviations ΔS. In step S307, the processing unit 24 of the robotic arm system 20 uses the set of mechanism parametric deviations ΔS to calibrate the mechanism parameter sets S.sub.1˜S.sub.nof the robotic arm 21.

[0089] FIG. 4 is a system configuration diagram of a robotic arm system 40 according to an embodiment of the present disclosure. In FIG. 4, the robotic arm system 40 comprises a robotic arm 41, a base 42, a storage unit 43, a processing unit 44 and a measuring instrument 45. The robotic arm 41 is disposed on the base 42 and electrically connected to the processing unit 44. The processing unit 44 is electrically connected to the storage unit 43 and the measuring instrument 45. The storage unit 43 is used to store nx mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.k, k=1, . . . , nx, ny mechanism parameter sets yS.sub.1˜yS.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.k, k=1, . . . , ny, and nz mechanism parameter sets zS.sub.1˜zS.sub.nz corresponding to the third-direction predictive positioning-points zP.sub.k, k=1, . . . , nz of the robotic arm 41. The processing unit 44 comprises a calibrating calculation unit 441 and a control unit 442.

[0090] In FIG. 4, the nx mechanism parameter sets xS.sub.1˜xS.sub.nx, the ny mechanism parameter sets yS.sub.1˜yS.sub.ny and the nz mechanism parameter sets zS.sub.1˜zS.sub.nz also comprise the size (arm length) of mechanical links, the connection orientations and angles between joint axes, the amount of joint variables, and other geometric variables.

[0091] In FIG. 4, the robotic arm system 40 obtains a set of mechanism parametric deviations ΔS through multiple calibration boundary planes. As shown in FIG. 4, the multiple calibration boundary planes comprise an X-direction first boundary plane, an X-direction second boundary plane, a Y-direction first boundary plane, a Y-direction second boundary plane, a Z-direction first boundary plane and a Z-direction second boundary plane.

[0092] In FIG. 4, the measuring instrument 45 is disposed on one end of the robotic arm 41, and the measuring instrument 45 can be a probe, a dial gauge, or a laser displacement meter which performs one-dimensional displacement measurement, or it can be a contact instrument or a non-contact instrument which performs displacement measurement. The present disclosure is not limited thereto. In another embodiment of the present disclosure, the measuring instrument 45 is not disposed on the end of the robotic arm 41, but is disposed in the configuration of the measuring instrument 25 shown in FIG. 2. At this moment, the measuring instrument 45 can be a coordinate-measuring machine or a laser tracker which performs spatial positioning measurement.

[0093] In FIG. 4, the measuring instrument 45 of the robotic arm system 40 utilizes the X-direction first boundary plane and the X-direction second boundary plane to measure first-direction measured relative-displacements ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx corresponding to the first-direction predictive positioning-points xP.sub.k, k=1, . . . , nx. The processing unit 44 of the robotic arm system 40 calculates a three-dimensional predictive relative-displacement equation G(xS.sub.i, xS.sub.j, ΔS)corresponding to two first-direction predictive positioning-points xP.sub.i and xP.sub.j. The three-dimensional predictive relative-displacement equation G(xS.sub.i, xS.sub.j, ΔS) is shown below:

[00005]$\Delta .Math..Math.{\mathrm{xP}}_{i,j}\equiv G\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)=\left[\begin{array}{c}{g}_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\\ g_y\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\\ g_z\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\end{array}\right],.Math.i=1,\mathrm{.Math.}.Math.,\mathrm{nx}-1,j=i+1,\mathrm{.Math.}.Math.,\mathrm{nx}$

Wherein g.sub.x(xS.sub.i, xS.sub.j, ΔS), g.sub.y(xS.sub.i, xS.sub.j, ΔS) and g.sub.z(xS.sub.i, xS.sub.j, ΔS) are respectively a first-direction predictive relative-displacement equation, a second-direction predictive relative-displacement equation, and a third-direction predictive relative-displacement equation corresponding to the two first-direction predictive positioning-points xP.sub.i and xP.sub.j.

[0094] In FIG. 4, the measuring instrument 45 of the robotic arm system 40 utilizes the Y-direction first boundary plane and the Y-direction second boundary plane to measure second-direction measured relative-displacements ΔyMy.sub.i,j, i=1, . . . , ny−1, j=i+1, . . . , ny corresponding to the second-direction predictive positioning-points xP.sub.k, k=1, . . . , nx. The processing unit 44 of the robotic arm system 40 calculates a three-dimensional predictive relative-displacement equation G(yS.sub.i, yS.sub.j, ΔS) corresponding to two second-direction predictive positioning-points yP.sub.i and yp.sub.j. The three-dimensional predictive relative-displacement equation G(yS.sub.i, yS.sub.j, ΔS) is shown below:

[00006]$\Delta .Math..Math.{\mathrm{yP}}_{i,j}\equiv G\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)=\left[\begin{array}{c}{g}_x\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\\ g_y\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\\ g_z\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\end{array}\right],.Math.i=1,\mathrm{.Math.}.Math.,\mathrm{ny}-1,j=i+1,\mathrm{.Math.}.Math.,\mathrm{ny}$

Wherein g.sub.x(yS.sub.i, xS.sub.j, ΔS), g.sub.y(yS.sub.i, yS.sub.j, ΔS) and g.sub.z(yS.sub.i, yS.sub.j, ΔS) are respectively a first-direction predictive relative-displacement equation, a second-direction predictive relative-displacement equation, and a third-direction predictive relative-displacement equation corresponding to the two second-direction predictive positioning-points yP.sub.i and yP.sub.j.

[0095] In FIG. 4, the measuring instrument 45 of the robotic arm system 40 utilizes the Z-direction first boundary plane and the Z-direction second boundary plane to measure third-direction measured relative-displacements ΔzMz.sub.i,j, i=1, . . . , ny−1,j=i+1, . . . , nz corresponding to the third-direction predictive positioning-points zP.sub.k, k=1, . . . , nz. The processing unit 44 of the robotic arm system 40 calculates a three-dimensional predictive relative-displacement equation G(zS.sub.i, zS.sub.j, ΔS) corresponding to two third-direction predictive positioning-points zP.sub.i and zP.sub.j. The three-dimensional predictive relative-displacement equation G(zS.sub.i, zS.sub.j, ΔS) is shown below:

[00007]$\Delta .Math..Math.{\mathrm{zP}}_{i,j}\equiv G\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)=\left[\begin{array}{c}{g}_x\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)\\ g_y\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)\\ g_z\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)\end{array}\right],.Math.i=1,\mathrm{.Math.}.Math.,\mathrm{nz}-1,j=i+1,\mathrm{.Math.}.Math.,\mathrm{nz}$

Wherein g.sub.x(zS.sub.i, zS.sub.j, ΔS), g.sub.y(zS.sub.i, zS.sub.j, ΔS) and g.sub.z(zS.sub.i, zS.sub.j, ΔS) are respectively a first-direction predictive relative-displacement equation, a second-direction predictive relative-displacement equation, and a third-direction predictive relative-displacement equation corresponding to the two third-direction predictive positioning-points zP.sub.i and zP.sub.j.

[0096] In FIG. 4, the calibrating calculation unit 441 of the processing unit 44 calculates an optimization equation Φ of the robotic arm 41 according to the first-direction predictive relative-displacement equations g.sub.x(xS.sub.i, xS.sub.j, ΔS) and the first-direction measured relative-displacements ΔxMx.sub.i,jcorresponding to the first-direction predictive positioning-points, the second-direction predictive relative-displacement equation g.sub.y(yS.sub.i, yS.sub.j, ΔS) and the second-direction measured relative-displacements ΔyMy.sub.i,j corresponding to the second-direction predictive positioning-points, and the third-direction predictive relative-displacement equation g.sub.z(zS.sub.i, zS.sub.j, ΔS) and the third-direction measured relative-displacements ΔzMz.sub.i,j corresponding to the third-direction predictive positioning-points. The optimization equation Φ is represented below:

[00008]$\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\left\{\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{ny}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{ny}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{yMy}}_{i,j}-g_y\left(y.Math..Math.S_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{nz}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nz}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{zMz}}_{i,j}-g_z\left({\mathrm{zS}}_i,{\mathrm{zS}}_j,\Delta .Math..Math.S\right)\right)}^2\right\}$

[0097] Then the processing unit 44 of the robotic arm system 40 utilizes an optimization algorithm and the optimization equation Φ to obtain a set of optimal mechanism parametric deviations ΔS. Finally, the processing unit 44 of the robotic arm system 40 uses the set of optimal mechanism parametric deviations ΔS to calibrate the mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx, the mechanism parameter sets yS.sub.1˜yS.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.ny and the mechanism parameter sets zS.sub.1˜z.sub.nz, corresponding to the third-direction predictive positioning-points zP.sub.1 ˜zP.sub.nz of the robotic arm 41.

[0098] In another embodiment of the present disclosure, the robotic arm system 40 performs only one-dimensional measurement and calculation and obtains a corresponding optimization equation Φ. The one dimension comprises the X-direction, Y-direction or Z-direction. E.g. the robotic arm system 40 only performs X-direction measurement and calculation. In this case, the calibrating calculation unit 441 of the processing unit 44 calculates the optimization equation Φ of the robotic arm 41 according to the first-direction predictive relative-displacement equations g.sub.x(xS.sub.i,xS.sub.j, ΔS) and the first-direction measured relative-displacements ΔxMx.sub.i,j corresponding to the first-direction predictive positioning-points. The optimization equation Φ is represented below:

[00009]$\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\left\{\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2\right\}$

[0099] In this case, the processing unit 44 of the robotic arm system 40 also utilizes an optimization algorithm and the optimization equation Φ of X-direction to obtain a set of optimal mechanism parametric deviations ΔS. Finally, the processing unit 44 of the robotic arm system 40 uses the set of optimal mechanism parametric deviations ΔS to calibrate the mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx of the robotic arm 41.

[0100] In another embodiment of the present disclosure, the robotic arm system 40 performs measurement and calculation in only two dimensions and obtains a corresponding optimization equation Φ. The two dimensions may comprise the X-direction and Y-direction, the Y-direction and Z-direction, or the X-direction and Z-direction. E.g. the robotic arm system 40 performs measurement and calculation in only first and second directions (the X-direction and Y-direction). In this case, the calibrating calculation unit 441 of the processing unit 44 calculates an optimization equation Φ of the robotic arm 41 according to the first-direction predictive relative-displacement equations g.sub.x(xS.sub.i, xS.sub.j, ΔS) and the first-direction measured relative-displacements ΔxMx.sub.i,j corresponding to the first-direction predictive positioning-points and the second-direction predictive relative-displacement equation g.sub.y(yS.sub.i, yS.sub.j, ΔS) and the second-direction measured relative-displacements ΔyMy.sub.i,j corresponding to the second-direction predictive positioning-points. The optimization equation Φ is represented below:

[00010]$\Phi =\underset{\Delta .Math..Math.S}{\min }.Math.\left\{\underset{i=1}{\overset{\mathrm{nx}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{nx}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{xMx}}_{i,j}-g_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\right)}^2+\underset{i=1}{\overset{\mathrm{ny}-1}{.Math.}}.Math.\underset{j=i+1}{\overset{\mathrm{ny}}{.Math.}}.Math.{\left(\Delta .Math..Math.{\mathrm{yMy}}_{i,j}-g_x\left({\mathrm{yS}}_i,{\mathrm{yS}}_j,\Delta .Math..Math.S\right)\right)}^2\right\}$

[0101] In this case, the processing unit 44 of the robotic arm system 40 also utilizes an optimization algorithm and the optimization equation Φ of X-direction and Y-direction to obtain a set of optimal mechanism parametric deviations ΔS. Finally, the processing unit 44 of the robotic arm system 40 uses the set of optimal mechanism parametric deviationsΔS to calibrate the mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx and the mechanism parameter sets yS.sub.1˜yS.sub.ny S.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.ny of the robotic arm 41.

[0102] It should be noted that, in the choices of the optimization algorithm of the robotic arm system 40, the processing unit 44 adopts the optimization algorithm with a non-linear equation. Because the first-direction predictive relative-displacement equations g.sub.x(xS.sub.i, xS.sub.j, ΔS) , the second-direction predictive relative-displacement equation g.sub.y(yS.sub.i, yS.sub.j, ΔS) and the third-direction predictive relative-displacement equation g.sub.z(zS.sub.i, zS.sub.j, ΔS) used for calculating the robotic arm 41 are almost equivalent to the robot non-linear mathematical model, approximation errors of g.sub.x(xS.sub.i, xS.sub.j, ΔS), g.sub.y(yS.sub.i, yS.sub.j, ΔS) and g.sub.z(zS.sub.i, zS.sub.j, ΔS) are extremely small. Accordingly, the optimization convergence effect of the set of mechanism parametric deviations ΔS obtained by the optimization equation Φ of the robotic arm system 40 is greater than the optimization convergence effect of the set of mechanism parametric deviations ΔS obtained by the optimization equation Φ of the robotic arm system 10.

[0103] Finally, it should be noted that the optimization algorithm utilized in the robotic arm system 20 and the robotic arm system 40 comprises the Least-Squares method, Gradient-Descent method, Gauss-Newton method or Levenberg-Marquardt method, but the present disclosure is not limited thereto.

[0104] FIG. 5 illustrates that how a robotic arm system 50 measures first-direction measured relative-displacements ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx corresponding to the first-direction predictive positioning-points, second-direction measured relative-displacements ΔyMy.sub.i,j, i=1, . . . , ny−1,j=i+1, . . . , ny corresponding to the second-direction predictive positioning-points, and third-direction measured relative-displacements ΔzMz.sub.i,j, i=1, . . . , nz−1,j=i+1, . . . , nz corresponding to the third-direction predictive positioning-points according to an embodiment of the present disclosure. Similar to the robotic arm system 40 shown in FIG. 4, the robotic arm system 50 shown in FIG. 5 comprises a robotic arm 51, a base 52, a storage unit 53, a processing unit 54, a measuring instrument 55 and a calibration (fixture) block 56. The robotic arm 51 is disposed on the base 52 and is electrically connected to the processing unit 54. The processing unit 54 is electrically connected to the storage unit 53 and the measuring instrument 55. The storage unit 53 is used to store the mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx the mechanism parameter sets yS.sub.1˜yS.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.ny and the mechanism parameter sets zS.sub.1˜zS.sub.nz corresponding to the third-direction predictive positioning-points zP.sub.1˜zP.sub.nz of the robotic arm 51. The processing unit 54 comprises a calibrating calculation unit 541 and a control unit 542. The calibration block 56 comprises a first precision plane C1, a second precision plane C2, a third precision plane C3, a fourth precision plane C4, a fifth precision plane C5 (not shown) and a sixth precision plane C6(not shown).

[0105] In FIG. 5, when the robotic arm system 50 proceeds with the measurement, the X-direction first boundary plane and the X-direction second boundary plane are implemented by the first precision plane C1 and the second precision plane C2 respectively, the Y-direction first boundary plane and the Y-direction second boundary plane are implemented by the third precision plane C3 and the fourth precision plane C4 respectively, and the Z-direction first boundary plane and the Z-direction second boundary plane are implemented by the fifth precision plane C5 and the sixth precision plane C6 respectively. The first precision plane C1 and the second precision plane C2 are the first-direction displacement parameter Dx apart, and the first precision plane C1 and the second precision plane C2 are both perpendicular to the first direction. The third precision plane C3 and the fourth precision plane C4 are the second-direction displacement parameter Dy apart, and the third precision plane C3 and the fourth precision plane C4 are both perpendicular to the second direction. The fifth precision plane C5 and the sixth precision plane C6 are the third-direction displacement parameter Dz apart, and the fifth precision plane C5 and the sixth precision plane C6 are both perpendicular to the third direction. The present disclosure is not limited thereto. E.g. the robotic arm system 50 can directly move the calibration block 56 in the first direction so that the first precision plane C1 is equivalent to the second precision plane C2. In FIG. 5, the calibration block 56 can be a straight edge, a processing machinery fixture block or other hardware structures which have at least one high precision plane for measured displacement.

[0106] In FIG. 5, the first-direction predictive positioning-points xP.sub.k, k=1, . . . , nx are described as a set of functions F(xS.sub.k+ΔS), k=1, . . . , nx corresponding to the mechanism parameter sets xS.sub.k, k=1, . . . , nx. The calibration calculation unit 541 of the processing unit 54 determines a first-direction predictive relative-displacement ΔxP.sub.i,j=xP.sub.j−xP.sub.i, between each two of the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx. The three-dimensional predictive relative-displacement equation G(xS.sub.i, xS.sub.j, ΔS) between two of the first-direction predictive positioning-points xP.sub.i and xP.sub.j is represented below:

[00011]$\begin{array}{cc}\begin{array}{c}\Delta .Math..Math.{\mathrm{xP}}_{i,j}=.Math.{\mathrm{xP}}_j-{\mathrm{xP}}_i\\ \equiv .Math.F\left({\mathrm{xS}}_j+\Delta .Math..Math.S\right)-F\left({\mathrm{xS}}_i+\Delta .Math..Math.S\right)\\ \equiv .Math.G\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\\ =.Math.\left[\begin{array}{c}{g}_x\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\\ g_y\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\\ g_z\left({\mathrm{xS}}_i,{\mathrm{xS}}_j,\Delta .Math..Math.S\right)\end{array}\right],\end{array}& \\ i=1,\mathrm{.Math.}.Math.,\mathrm{nx}-1,j=i+1,\mathrm{.Math.}.Math.,\mathrm{nx}& \end{array}$

[0107] Accordingly, the calibration calculation unit 541 of the processing unit 54 calculates the first-direction predictive relative-displacement equations g.sub.x(xS.sub.i, xS.sub.j, ΔS) corresponding to the first-direction predictive positioning-points.

[0108] In FIG. 5, the measuring instrument 55 measures a first-direction measured displacement xMx.sub.k between the end of the robotic arm 51 and the first precision plane C1 while performing each of the actions.

[0109] The calibration calculation unit 541 determines, according to the first-direction measured displacements xMx.sub.k, a first-direction measured relative-displacement ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx moved by the end of the robotic arm 51 while performing each two of the actions.

[0110] In FIG. 5, the processing unit 54 controls the posture of the robotic arm 51 so that the measuring direction of the measuring instrument 55 is forward, toward the first precision plane C1 of the calibration block 56. Then the processing unit 54 controls the robotic arm 51 so that the end of the robotic arm 51 moves toward the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx which are located within sensing range of the measuring instrument 55. At this moment, the measuring instrument 55 measures the first-direction measured displacement ΔxMx.sub.k, k=1, . . . , nx (xMx.sub.1˜xMx.sub.nx) between the end of the robotic arm 51 and the first precision plane C1. The processing unit 54 determines the first-direction measured relative-displacement ΔxMx.sub.i,j, i=1, . . . , nx−1,j=i+1, . . . , nx corresponding to the first-direction predictive relative-displacement ΔxP.sub.i,j according to the first-direction measured displacements xMx.sub.1˜xMx.sub.nx. The first-direction measured relative-displacement ΔxMx.sub.i,j is a relative displacement measured by one-dimensional measurement by the measuring instrument 55.

[0111] In FIG. 5, the first-direction measured relative-displacement ΔxMx.sub.i,j corresponding to the first-direction predictive positioning-points xP.sub.i and xP.sub.j is represented below:

ΔxMx.sub.i,jxMx.sub.j−xMx.sub.i+Dx, i=1nx−1,j=i+1, . . . , nx

Wherein if the first-direction measured displacements xMx.sub.i and xMx.sub.j are measured by the same precision plane (e.g. both measured by the first precision plane C1), then the value of Dx is 0. If the first-direction measured displacements xMx.sub.i and xMx.sub.j are measured by two parallel precision planes (e.g. measured by the first precision plane C1 and the second precision plane C2), then Dx is a first-direction relative displacement between the two parallel precision planes.

[0112] In FIG. 5, the distance between the measuring instrument 55 and the first precision plane C1 is required to be smaller than the sensing range of the measuring instrument 55. Because the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx are not all located within sensing range of the measuring instrument 55, it is required to increase the sensing displacement measured by the measuring instrument 55. Accordingly, the robotic arm system 50 uses the second precision plane C2 which is the first-direction displacement Dx away from the first precision plane C1 to solve the inadequate sensing range of the measuring instrument 55. In addition, if the first-direction predictive positioning-points xP.sub.i˜xP.sub.nx are all located within sensing range of the measuring instrument 55, the robotic arm system 50 only requires the first precision C1 to measure the first-direction measured relative-displacement ΔxMx.sub.i,j.

[0113] When a first-direction pitch between an out-of-range first-direction predictive positioning-point xP.sub.k and the first precision plane C1 exceeds the maximum sensing range of the measuring instrument 55 in the first direction, the processing unit 54 controls the robotic arm 51 so that the end of the robotic arm 51 moves toward the out-of-range first-direction predictive positioning-point xP.sub.k which is in front of the second precision plane C2 of the calibration block 56 to sense the first-direction measured displacement ΔxMx.sub.i,j between the end of the robotic arm 51 and the first precision plane C1. Through the method of adding a boundary plane, the first-direction measured relative-displacement ΔxMx.sub.i,j corresponding to the first-direction predictive positioning-points xP.sub.i and xP.sub.j is not limited to the sensing range of the measuring instrument 55.

[0114] Unlike the measuring instrument 25 illustrated in FIG. 2, the measuring instrument 55 of the robotic arm system 50 in FIG. 5 is disposed on the end of the robotic arm 51. Therefore the measuring instrument 55 can be a probe, a dial gauge, or a laser displacement meter, which performs one-dimensional displacement measurement, or it can be a contact instrument or a non-contact instrument which performs displacement measurement. The displacement meter adopted by the measuring instrument 55 costs less and can be used to obtain practical measurements more easily than either the measuring instrument 25 illustrated in FIG. 2 or the measuring instrument 15 in FIG. 1.

[0115] In the same manner, the measuring instrument 55 of the robotic arm system 50 measures, through the third precision plane C3 and the fourth precision plane C4, the second-direction predictive positioning-points yP.sub.k, k=1, . . . , ny (yP.sub.1˜yP.sub.ny) to obtain the second-direction measured relative-displacements ΔyMy.sub.i,j, i=1, . . . , ny−1, j=i+1, . . . , ny corresponding to the second-direction predictive positioning-points yP.sub.i and yp.sub.j. The processing unit 54 obtains the second-direction predictive relative-displacement equation g.sub.y(yS.sub.i, yS .sub.j, ΔS) according to the mechanism parameter sets yS.sub.1˜yS.sub.ny.

[0116] Similarly, the processing unit 54 obtains the third-direction predictive relative-displacement equation g.sub.z(zS.sub.i,zS.sub.j, ΔS) according to the mechanism parameter sets zS.sub.1˜zS.sub.nz. The measuring instrument 55 also measures, through the fifth precision plane C5 and the sixth precision plane C6, the third-direction predictive positioning-points zP.sub.k, k=1, . . . , nz (zP.sub.1˜zP.sub.nz) to obtain the third-direction measured relative-displacements ΔzMz.sub.i,j, i=1, . . . , nz−1,j=i+1, . . . , nz corresponding to the third-direction predictive positioning-points zP.sub.i and zP.sub.j.

[0117] Then the calibration calculation unit 541 of the processing unit 54 calculates an optimization equation Φ according to g.sub.x(xS.sub.i, xS.sub.j, ΔS), ΔxMx.sub.i,j, g.sub.y(yS.sub.i, yS.sub.j, ΔS), AΔyMy.sub.i,j, g.sub.z(zS.sub.i, zS.sub.j, ΔS) and ΔzMz.sub.i,j.

[0118] Then the processing unit 54 of the robotic arm system 50 also utilizes an optimization algorithm and the optimization equation Φ to obtain a set of optimal mechanism parametric deviations ΔS. Finally, the processing unit 54 of the robotic arm system 50 uses the set of optimal mechanism parametric deviations ΔS to calibrate the mechanism parameter sets xS.sub.1˜xS.sub.nx corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.nx, the mechanism parameter sets yS.sub.1˜yS.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.ny and the mechanism parameter sets zS.sub.1˜zS.sub.nz corresponding to the third-direction predictive positioning-points zP.sub.1˜zP.sub.nzof the robotic arm 51.

[0119] FIG. 6 illustrates how the robotic system 50 measures the first-direction measured relative-displacement ΔxMx.sub.i,j, i=1, . . . , 4,j=i+1, . . . , 5 corresponding to the first-direction predictive positioning-points xP.sub.1˜xP.sub.5 according to an embodiment of the present disclosure. In FIG. 6, the processing unit 54 of the robotic system 50 controls, according to a plurality of mechanism parameter sets xS.sub.1˜xS.sub.5, the robotic arm 51 to perform a plurality of actions so that the end of the robotic arm 51 moves toward the corresponding plurality of first-direction predictive positioning-points xP.sub.1˜xP.sub.5.

[0120] In FIG. 6, the processing unit 54 of the robotic system 50 controls the posture of the robotic arm 51 so that the measuring direction of the measuring instrument 55 towards the first precision plane C1 of the calibration block 56. Then the processing unit 54 controls, according to a plurality of mechanism parameter sets xS.sub.1˜xS.sub.3, the robotic arm 51 so that the end of the robotic arm 51 moves toward the first-direction predictive positioning-points xP.sub.1˜xP.sub.3 which are located within sensing range of the measuring instrument 55. At this moment, the measuring instrument 55 measures the first-direction measured displacements xMx.sub.1, xMx.sub.2, xMx.sub.3 between the end of the robotic arm 51 and the first precision plane C1. The processing unit 54 respectively determines the first-direction measured relative-displacements ΔxMx.sub.1,2, (i.e. xMx.sub.2−xMx.sub.1), ΔxMx.sub.1,3(i.e. xMx.sub.3−xMx.sub.1), ΔxMx.sub.2,3(i.e. xMx.sub.3−xMx.sub.21) corresponding to the first-direction predictive relative-displacement ΔxP.sub.1,2, ΔxP.sub.1,3, ΔxP.sub.2,3according to the first-direction measured displacements xMx.sub.1˜xMx.sub.3.

[0121] Because the first-direction predictive positioning-points xP.sub.4 and xP.sub.5 with respect to the first precision plane C1 are located out of sensing range of the measuring instrument 55, the measuring instrument 55 measures the first-direction measured displacements xMx.sub.4, xMx.sub.5 between the end of the robotic arm 51 and the second precision plane C2. The processing unit 54 respectively determines the first-direction measured relative-displacement ΔxMx.sub.5,4(i.e. xMx.sub.5−xMx.sub.41) corresponding to the first-direction predictive relative-displacement ΔxP.sub.4,5 according to the first-direction measured displacements xMx.sub.4 and xMx.sub.5.

[0122] In FIG. 6, when the processing unit 54 of the robotic system 50 calculates the first-direction measured relative-displacement ΔxMx.sub.i,j (e.g. ΔxMx.sub.1,4) measured from two different sensing ranges, the first-direction relative displacement Dx between the two parallel precision planes is taken into consideration. Therefore the first-direction measured relative-displacements ΔxMx.sub.i,j are represented below:

ΔxMx.sub.i,j=xMx.sub.j−xMx.sub.i+Dx, i=1, 2, 3,j=4, 5

[0123] FIG. 7 illustrates how the robotic system 50 measures the second-direction measured relative-displacement ΔyMy.sub.i,j, i=1, . . . , 3,j=i+1, . . . , 4 corresponding to the second-direction predictive positioning-points y1.sup.3.sub.1yP.sub.4 according to an embodiment of the present disclosure. In FIG. 7, the processing unit 54 of the robotic system 50 controls, according to a plurality of mechanism parameter sets yS.sub.1˜yS.sub.4, the robotic arm 51 to perform a plurality of actions so that the end of the robotic arm 51 moves toward the corresponding plurality of second-direction predictive positioning-points yP.sub.1˜yP.sub.4.

[0124] In FIG. 7, the second-direction predictive positioning-points yP.sub.1˜yP.sub.2 are located within sensing range of the measuring instrument 55 with respect to the third precision plane C3, and the second-direction predictive positioning-points yP.sub.3 ˜yP.sub.4 are located within sensing range of the measuring instrument 55 with respect to the fourth precision plane C4. The measuring instrument 55 measures the second-direction measured displacements yMy.sub.1 and yMy.sub.2 between the end of the robotic arm 51 and the third precision plane C3. Then the measuring instrument 55 measures the second-direction measured displacements yMy.sub.3 and yMy.sub.4 between the end of the robotic arm 51 and the fourth precision plane C4. The processing unit 54 respectively determines the second-direction measured relative-displacements ΔyMy.sub.1,2(i.e. yMy.sub.2−yMy.sub.1) and ΔyMy.sub.3,4(i.e.yMy.sub.4−yMy.sub.3) corresponding to the second-direction predictive relative-displacements ΔyP.sub.1,2 and ΔyP.sub.3,4. Similarly, in consideration of a second-direction relative displacement Dy between the third precision plane C3 and the fourth precision plane C4, the processing unit 54 obtains second-direction measured relative-displacements ΔyMy.sub.i,j=yMy.sub.g−yMy.sub.i+Dy, i=1, 2,j=3,4.

[0125] Similarly, using the same measuring method used in FIG. 6 and FIG. 7, the robotic system 50 may also obtain third-direction measured relative-displacements ΔzMz.sub.i,j, i=1, . . . , nz−1, j=i+1, . . . , nz corresponding to the third-direction predictive positioning-points according to the mechanism parameter sets zS.sub.1˜zS.sub.nz.

[0126] FIGS. 8A-8E show a flow diagram illustrating a mechanism-parametric-calibration method for the robotic arm system 40. In step S801, boundary planes of each of the directions (X-direction, Y-direction and Z-direction) are installed, and displacements parameters Dx, Dy, Dz among different boundaries with respect to the same direction are obtained. In step S802, the robotic arm system 40 or a manipulator of the robotic arm system 40 determines whether to perform an X-direction measurement or not. If yes, the method proceeds to step S803. Otherwise, the method proceeds to step S807. In step S803, the processing unit 44 of the robotic system 40 controls the posture of the robotic arm 41 so that the measuring instrument 45 is facing the X-direction boundary planes.

[0127] In step S804, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct first-direction predictive positioning-points xP.sub.k in front of the X-direction first boundary plane. At this moment, the measuring instrument 45 measures the first-direction predictive positioning-points xP.sub.k in front of the X-direction first boundary plane to obtain corresponding X-direction measured displacements xMx.sub.k, and the mechanism parameter sets xS.sub.k corresponding to the first-direction predictive positioning-points xP.sub.k are stored.

[0128] In step S805, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct first-direction predictive positioning-points xP.sub.k in front of the X-direction second boundary plane. At this moment, the measuring instrument 45 measures the first-direction predictive positioning-points xP.sub.k in front of the X-direction second boundary plane to obtain corresponding X-direction measured displacements xMx.sub.k, and the mechanism parameter sets xS.sub.k corresponding to the first-direction predictive positioning-points xP.sub.k are stored. In step S806, the processing unit 44 of the robotic arm system 40 obtains first-direction predictive relative-displacement equations g.sub.x(xS.sub.i, xS.sub.j, ΔS) corresponding to the first-direction predictive positioning-points and determines X-direction measured relative-displacement ΔxMx.sub.i,j according to the X-direction measured displacements xMx.sub.1˜xMx.sub.nx. Then the method proceeds to step S807.

[0129] In step S807, the robotic arm system 40 or the manipulator of the robotic arm system 40 determines whether to perform a Y-direction measurement or not. If yes, the method proceeds to step S808. Otherwise, the method proceeds to step S8012. In step S808, the processing unit 44 of the robotic system 40 controls the posture of the robotic arm 41 so that the measuring instrument 45 is facing the Y-direction boundary planes.

[0130] In step S809, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct second-direction predictive positioning-points yP.sub.k in front of the Y-direction first boundary plane. At this moment, the measuring instrument 45 measures the second-direction predictive positioning-points yP.sub.k in front of the Y-direction first boundary plane to obtain corresponding Y-direction measured displacements yMy.sub.k, and the mechanism parameter sets yS.sub.k corresponding to the second-direction predictive positioning-points yP.sub.k are stored.

[0131] In step S810, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct second-direction predictive positioning-points yP.sub.k in front of the Y-direction second boundary plane. At this moment, the measuring instrument 45 measures the second-direction predictive positioning-points yP.sub.k in front of the Y-direction second boundary plane to obtain corresponding Y-direction measured displacements yMy.sub.k, and the mechanism parameter sets yS.sub.k corresponding to the second-direction predictive positioning-points yP.sub.k are stored. In step S811, the processing unit 44 of the robotic arm system 40 obtains second-direction predictive relative-displacement equations g.sub.y(yS.sub.i, yS .sub.j, ΔS) corresponding to the second-direction predictive positioning-points and determines Y-direction measured relative-displacement ΔyMy.sub.i,j according to the Y-direction measured displacements yMy.sub.1˜yMy.sub.ny. Then the method proceeds to step S812.

[0132] In step S812, the robotic arm system 40 or the manipulator of the robotic arm system 40 determines whether to perform a Z-direction measurement or not. If yes, the method proceeds to step S813. Otherwise, the method proceeds to step S8017. In step S813, the processing unit 44 of the robotic system 40 controls the posture of the robotic arm 41 so that the measuring instrument 45 faces the Z-direction boundary planes.

[0133] In step S814, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct third-direction predictive positioning-points zP.sub.k in front of the Z-direction first boundary plane. At this moment, the measuring instrument 45 measures the third-direction predictive positioning-points zP.sub.k in front of the Z-direction first boundary plane to obtain corresponding Z-direction measured displacements zMz.sub.k, and the mechanism parameter sets zS.sub.k corresponding to the third-direction predictive positioning-points zP.sub.k are stored.

[0134] In step S815, the processing unit 44 of the robotic arm system 40 controls the robotic arm 41 so that the robotic arm 41 moves toward random distinct second-direction predictive positioning-points zP.sub.k in front of the Z-direction second boundary plane. At this moment, the measuring instrument 45 measures the third-direction predictive positioning-points zP.sub.k in front of the Z-direction second boundary plane to obtain corresponding Z-direction measured displacements yMy.sub.k, and the mechanism parameter sets zS.sub.k corresponding to the third-direction predictive positioning-points zP.sub.k are stored. In step S816, the processing unit 44 of the robotic arm system 40 obtains third-direction predictive relative-displacement equations g.sub.z(zS.sub.i, zS.sub.3, ΔS) corresponding to the third-direction predictive positioning-points and determines Z-direction measured relative-displacement ΔzMz.sub.i,j according to the Z-direction measured displacements zMz.sub.1˜zMz.sub.nz. Then the method proceeds to step S817.

[0135] In step S817, the processing unit 44 of the robotic arm system 40 calculates an optimization equation Φ of the robotic arm 41 according to ΔxMx.sub.i,j, ΔyMy.sub.i,j, ΔzMz.sub.i,j, ΔzMz.sub.i,j, g.sub.x(xS.sub.i,xS.sub.j, ΔS), g.sub.y(yS.sub.i, yS.sub.j, ΔS), g.sub.z(zS.sub.i, zS.sub.j, ΔS). In step S818, the processing unit 44 of the robotic arm system 40 utilizes an optimization algorithm and the optimization equation Φ to obtain a set of optimal mechanism parametric deviations ΔS.

[0136] Finally, in step S819, the processing unit 44 of the robotic arm system 40 uses the set of optimal mechanism parametric deviations ΔS to calibrate the mechanism parameter sets xS.sub.1˜xS.sub.nz corresponding to the first-direction predictive positioning-points xP.sub.i˜xP.sub.nx, the mechanism parameter sets yS.sub.1˜yS.sub.ny corresponding to the second-direction predictive positioning-points yP.sub.1˜yP.sub.ny and the mechanism parameter sets zS.sub.1˜zS.sub.nz corresponding to the third-direction predictive positioning-points zP.sub.1˜zP.sub.nz of the robotic arm 41.

[0137] While the present disclosure has been described by way of example and in terms of preferred embodiment, it is to be understood that the present disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to a person skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.