Actuator system

Abstract

An actuator system may include a first actuator for being operated by a user, a second actuator for performing a movement of the user, and a transmission channel between the first actuator and the second actuator for transmitting the velocity and the force of the first actuator to the second actuator and vice versa. The actuator system may also include a controller, wherein the controller is configured such that, with the aid of the controller, the energy of the first actuator is adapted to be measured as a desired energy, wherein the transmission channel is configured for transmitting the desired energy to the second actuator and the controller is configured for controlling the damping of the second actuator as a function of the desired energy.

Claims

1. An actuator system comprising a first actuator for being operated by a user, a second actuator for performing a movement of the user, a transmission channel between the first actuator and the second actuator for transmitting a velocity and a force of the first actuator to the second actuator and vice versa, and a controller, wherein the controller is configured such that, with the aid of the controller, the energy of the first actuator is adapted to be measured as a desired energy, wherein the transmission channel is configured for transmitting the desired energy to the second actuator, and the controller is configured for controlling a damping of the second actuator as a function of the desired energy, wherein power P.sub.i is obtained according to P.sub.i(k)=v.sub.i(k)F.sub.i(k), for a sampling step k with a velocity v.sub.i(k) of the actuator and a force F.sub.i(k) of the controller, wherein energies E.sub.i are calculated as $E_i^{L2R}\left(k\right)=T_s\underset{j=0}{\overset{k}{.Math.}}{P}_i^{L2R}\left(j\right),\mathrm{and}$ $E_i^{R2L}\left(k\right)=T_s\underset{j=0}{\overset{k}{.Math.}}{P}_i^{R2L}\left(j\right),$ wherein L2R denotes a power and an energy from the first actuator to the second actuator, R2L denotes a power and an energy from the second actuator to the first actuator and T.sub.s denotes a sampling time.

2. The actuator system according to claim 1, wherein the controller is configured such that, with the aid of the controller, the energy of the second actuator is adapted to be measured as a desired energy, the desired energy is transmitted to the first actuator via the transmission channel, and the controller is configured for controlling a damping of the first actuator as a function of the transmitted desired energy.

3. The actuator system according to claim 1, wherein the transmission channel has a time lag.

4. The actuator system according to claim 1, wherein the transmission channel is a data link.

5. The actuator system according to claim 1, wherein the first actuator or the second actuator have one or more than one degree of freedom, wherein the velocity and the force for each of the degrees of freedom are transmitted to the respective other actuator via the transmission channel.

6. The actuator system according to claim 1, wherein the first actuator and the second actuator have identical degrees of freedom.

7. The actuator system according to claim 1, wherein the force is damped such that
E.sub.1.sup.L2R(k)+E.sub.5.sup.R2L(k)≥E.sub.1.sup.R2L(k)+E.sub.5.sup.L2R(k) is always fulfilled.

8. The actuator system according to claim 1, wherein the controller comprises an energy monitoring means which monitors energy flows of E.sub.2.sup.L2R(k) and E.sub.4.sup.R2L(k), wherein an energy E.sub.St stored in the energy monitoring means is
E.sub.St(k)=E.sub.St(k−1)+P.sub.2.sup.L2R(k−T.sub.1)T.sub.s+P.sub.4.sup.R2L(k)T.sub.s wherein T.sub.1 denotes a transmission time from the first actuator to the second actuator via the transmission channel.

9. The actuator system according to claim 8, wherein, due to the damping, energy W.sup.PC1 is dissipated, wherein the energy W.sup.PC1 to be dissipated is $W^{\mathrm{PC}1}\left(k\right)=\underset{j=0}{\overset{k-T_2}{.Math.}}{P}^{R2L,\mathrm{des}}\left(j\right)T_s-\underset{j=0}{\overset{k}{.Math.}}{P}_2^{R2L}\left(j\right)T_s-W_{\mathrm{diss}}^{\mathrm{PC}1}\left(k-1\right)$ with T.sub.2 as a transmission time from the second actuator to the first actuator via the transmission channel, wherein P.sup.R2L,des(k) is
P.sup.R2L,des(k)=P.sub.3.sup.R2L(k)+P.sub.exc.sup.R2L(k), with P.sub.3.sup.R2L as a power adapted to be sensed by the energy monitoring means as an input power into the transmission channel towards the first actuator and P.sub.exc.sup.R2L(k) is $P_{\mathrm{exc}}^{R2L}\left(k\right)=\{\begin{array}{cc}{P}_{\mathrm{exc}}\left(k\right)\frac{P_3^{R2L}\left(k\right)}{P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)},& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)<P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\\ 0,& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)>P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\end{array}$ with
P.sub.exc(k)=E.sub.St(k)/T.sub.s−P.sub.out.sup.act(k)
and
P.sub.out.sup.act(k)=P.sub.3.sup.R2L(k)+P.sub.4.sup.L2R(k), wherein P.sub.4.sup.L2R(k) denotes a power transmitted by the energy monitoring means to the second actuator.

10. The actuator system according to claim 8, wherein due to the damping, energy W.sup.PC2 is dissipated, wherein the dissipated energy W.sup.PC2 is $W^{\mathrm{PC}2}\left(k\right)=\underset{j=0}{\overset{k}{.Math.}}\left(P^{L2R,\mathrm{des}}\left(j\right)-P_4^{L2R}\left(j\right)\right)T_s-W_{\mathrm{diss}}^{\mathrm{PC}2}\left(k-1\right).$ with
P.sup.L2R,des(k)=P.sub.4.sup.L2R(k)+P.sub.exc.sup.L2R(k), wherein P.sub.4.sup.L2R(k) denotes a power transmitted by the energy monitoring means to the second actuator and P.sub.exc.sup.L2R(k) is $P_{\mathrm{exc}}^{L2R}\left(k\right)=\{\begin{array}{cc}{P}_{\mathrm{exc}}\left(k\right)\frac{P_4^{\mathrm{L2R}}\left(k\right)}{P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)},& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)<P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\\ 0,& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)>P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\end{array},$ with
P.sub.exc(k)=E.sub.St(k)/T.sub.s−P.sub.out.sup.act(k)
and
P.sub.out.sup.act(k)=P.sub.3.sup.R2L(k)+P.sub.4.sup.L2R(k), wherein P.sub.3.sup.R2L denotes a power adapted to be sensed by the energy monitoring means as the input power into the transmission channel towards the first actuator.

11. The actuator system according to claim 4, wherein the data link is the internet.

12. The actuator system according to claim 6, wherein the identical degrees of freedom of the first actuator and the second actuator are identically designed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic diagram of the actuator system in the form of a 2-port network.

DESCRIPTION OF THE INVENTION

(2) The actuator system according to the invention comprises a first actuator 10 as well as a second actuator 12. The first actuator 10 and the second actuator 12 are connected to each other via a transmission channel 14. The transmission channel 14 has a time lag indicated by the dashed line 16. Thus, T.sub.1 is the transmission time from the first actuator to the second actuator and T.sub.2 is the transmission time from the second actuator to the first actuator. In particular, T.sub.1 and T.sub.2 can be the same but can also differ from each other. The transmission channel 14 can be a wired data link or a wireless data link. In particular, the transmission from the first actuator 10 to the second actuator 12 and vice versa can be carried out via the internet or another communication link.

(3) A movement of the first actuator (A1) 10 applied by a user to the first actuator 10, for example, is transmitted to the second actuator (A2) 12 via the transmission channel (CC) 14, the second actuator being intended for performing the same movement with the same force and velocity and a high position accuracy. In particular, the first actuator 10 and the second actuator 12 can be provided in a master-slave configuration. However, forces and movement acting on the second actuator 12 are also to be transmitted to the first actuator 10 via the transmission channel 14, in particular within the framework of a force-feedback system. Thereby, a high system transparency is created such that a user connected with the first actuator experiences forces acting on the second actuator 12, for example as a haptic feedback, a visual feedback or the like.

(4) The time lag 16 of the transmission channel 14 could make the actuator system instable. For ensuring the stability or passivity of the actuator system, a controller is provided. The controller comprises a first passivity controller (PC) 18 which damps the first actuator 10. In addition, a second passivity controller (PC) 20 is provided which damps the second actuator 12. In addition, a position controller 22 is provided which controls a position coupling between the first actuator and the second actuator. The position controller 22 has connected thereto an energy monitoring means 23 for monitoring the energies. The energy monitoring means (E) 23 comprises an energy storage. In the FIGURE, the energy monitoring means 23 is configured as a separate element. However, the energy monitoring means 23 can be an integral part of the position controller 22.

(5) By the controller and in particular the energy monitoring means 23 the power is obtained as
P.sub.i(k)=v.sub.i(k)F.sub.i(k)
for the sampling step k with the velocity v.sub.i(k) of the actuator and the force F.sub.i(k) of the controller. Thereby, the energies E.sub.i are obtained as

(6) $E_i^{L2R}\left(k\right)=T_s\underset{j=0}{\overset{k}{.Math.}}{P}_{i|}^{L2R}\left(j\right),\mathrm{and}$$E_i^{R2L}\left(k\right)=T_s\underset{j=0}{\overset{k}{.Math.}}{P}_i^{R2L}\left(j\right),$

(7) Here, “L2R” denotes the power P.sub.i or the energy E.sub.i from the first actuator towards the second actuator, and “R2L” denotes the power with the energy of the second actuator to the first actuator according to arrows 24. T.sub.s denotes the sampling time. i denotes the respective port between the individual elements of the actuator system such that i=1, . . . , 5.

(8) Here, the force of the first actuator 10 and the second actuator 12 is damped by the passivity controllers 18, 20 such that
E.sub.1.sup.L2R(k)+E.sub.5.sup.R2L(k)≥E.sub.1.sup.R2L(k)+E.sub.5.sup.L2R(k).
is always fulfilled. Thereby, the stability of the actuator system is guaranteed.

(9) In the energy storage of the energy monitoring means 23 the energy
E.sub.St(k)=E.sub.St(k−1)+P.sub.2.sup.L2R(k−T.sub.1)T.sub.s+P.sub.4.sup.R2L(k)T.sub.s
is stored, with T.sub.1 as the transmission time from the first actuator to the second actuator. The stored energy E.sub.St is a potential energy of the system. The stored energy thus results from the stored energy of the previous sampling step of the power at port 2 which is transmitted from the first actuator 10 to the second actuator 12 as well as the power at port 4 which is transmitted from the second actuator 12 to the first actuator 10. This is indicated by arrows 26 in the FIGURE.

(10) The force of the first actuator 10 and the second actuator 12 is then damped by the passivity controllers (PC) 18, 20. The energy to be dissipated by the passivity controller 18 is

(11) $W^{\mathrm{PC}1}\left(k\right)=\underset{j=0}{\overset{k-T_2}{.Math.}}{P}^{R2L,\mathrm{des}}\left(j\right)T_s-\underset{j=0}{\overset{k}{.Math.}}{P}_2^{R2L}\left(j\right)T_s-W_{\mathrm{diss}}^{\mathrm{PC}1}\left(k-1\right)$
with T.sub.2 as the transmission time from the second actuator 12 to the first actuator 10 via the transmission channel 14. This results in P.sup.R2L,des(k) as
P.sup.R2L,des(k)=P.sub.3.sup.R2L(k)+P.sub.exc.sup.R2L(k)
with P.sub.3.sup.R2L as the power at port 3 transmitted from the second actuator 12 to the first actuator 10 and thus denotes the power adapted to be sensed by the energy monitoring means 23 as the input power into transmission channel 14 towards the first actuator 10. P.sub.exc.sup.L2R(k) is dependent on the energy stored in the energy storage and is

(12) $P_{\mathrm{exc}}^{R2L}\left(k\right)=\{\begin{array}{cc}{P}_{\mathrm{exc}}\left(k\right)\frac{P_3^{R2L}\left(k\right)}{P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)},& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)<P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\\ 0,& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)>P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\end{array}$
with
P.sub.exc(k)=E.sub.St(k)/T.sub.s−P.sub.out.sup.act(k)
and
P.sub.out.sup.act(k)=P.sub.3.sup.R2L(k)+P.sub.4.sup.L2R(k).

(13) This results in the energy to be dissipated by the passivity controller 18 as a function of the energy stored in the energy storage. Here, merely the force is reduced. In addition, in any case, the force is reduced after the measurement of the transmitted energy so that energy is always only dissipated to such an amount that the stability of the actuator system is ensured. Thereby, an energy-efficient system is ensured.

(14) Analogously, the energy to be dissipated by the second passivity controller 20 is

(15) 0$W^{\mathrm{PC}2}\left(k\right)=\underset{j=0}{\overset{k}{.Math.}}\left(P^{L2R,\mathrm{des}}\left(j\right)-P_4^{L2R}\left(j\right)\right)T_s-W_{\mathrm{diss}}^{\mathrm{PC}2}\left(k-1\right).$
with
P.sup.L2R,des(k)=P.sub.4.sup.L2R(k)+P.sub.exc.sup.L2R(k),
wherein P.sub.4.sup.L2R(k) denotes the power transmitted from the energy monitoring means 23 to the second actuator and P.sub.exc.sup.L2R(k) is

(16) $P_{\mathrm{exc}}^{L2R}\left(k\right)=\{\begin{array}{cc}{P}_{\mathrm{exc}}\left(k\right)\frac{P_4^{L2R}\left(k\right)}{P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)},& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)<P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\\ 0,& \mathrm{if}{E}_{\mathrm{St}}\left(k\right)>P_{\mathrm{out}}^{\mathrm{act}}\left(k\right)T_s\end{array},$
with
P.sub.exc(k)=E.sub.St(k)/T.sub.s−P.sub.out.sup.act(k)
and
P.sub.out.sup.act(k)=P.sub.3.sup.R2L(k)+P.sub.4.sup.L2R(k).

(17) Thus, a new actuator system is created which is always stable and where the passivity controllers 18, 20 are controlled such that merely a required energy dissipation or reduction of the force is carried out. Thereby, the system becomes energy-efficient. At the same time, only minor corrections for attaining the passivity are required such that the user connected with the first actuator experiences no or merely small force surges within the framework of the force-feedback system, whereby the system transparency is increased. This is attained by the damping of the passivity controllers 18, 20 merely acting upon the force of the first actuator or the second actuator 12. This is also attained by performing the damping only after the measurement of the relevant energies, whereby, as described above, merely such energy is dissipated which would lead to an instability of the system.

(18) The embodiments illustrated herein are mere examples of the present invention and should therefore not be construed as being limiting. Alternatives provided by a skilled person in consideration of the embodiments are likewise encompassed by the scope of protection of the present invention. Accordingly, the foregoing description is intended to be illustrative rather than restrictive. The invention described hereinabove is defined by the appended claims and all changes to the invention that fall within the meaning and range of equivalency of the claims are to be embraced within their scope.