Method Of Controlling Industrial Robot, Control System And Robot System

Abstract

A method of controlling an industrial robot, the method including visualizing a nominal path of the industrial robot, the nominal path being associated with a nominal trajectory of the industrial robot; visualizing indications of values of at least one parameter of the industrial robot as when executing the nominal trajectory, for evaluating a risk potential of a physical contact between the industrial robot and a human; receiving a user input related to the nominal trajectory; modifying the nominal trajectory based on the user input to provide a modified trajectory; and executing the modified trajectory by the industrial robot. A control system and an industrial robot are also provided.

Claims

1. A method of controlling an industrial robot, the method comprising: visualizing a nominal path of the industrial robot, the nominal path being associated with a nominal trajectory of the industrial robot; visualizing indications of values of at least one parameter of the industrial robot as when executing the nominal trajectory, for evaluating a risk potential of a physical contact between the industrial robot and a human; receiving a user input related to the nominal trajectory; modifying the nominal trajectory based on the user input to provide a modified trajectory; and executing the modified trajectory by the industrial robot.

2. The method according to claim 1, wherein the at least one parameter comprises acceleration, force, torque, pressure and/or kinetic energy.

3. The method according to claim 1, further comprising estimating an effective mass of the industrial robot, and determining values of the at least one parameter based on the effective mass.

4. The method according to claim 1, wherein the indications comprise a direction associated with a respective value of the at least one parameter.

5. The method according to claim 1, wherein the indications comprise indications of values of the at least one parameter in relation to a specific body part of the human.

6. The method according to claim 1, wherein the indications comprise indications of values of the at least one parameter in relation to a type of contact event between the industrial robot and the human.

7. The method according to claim 1, further comprising visualizing the industrial robot.

8. The method according to claim 7, wherein the indications comprise indications of values of at least one parameter of a part of the industrial robot.

9. The method according to claim 1, wherein the indications comprise indications visualized along the nominal path.

10. The method according to claim 1, wherein the indications are color indications.

11. The method according to claim 1, wherein the indications show whether the values are below or above a threshold value.

12. The method according to claim 1, further comprising: visualizing a modified path associated with the modified trajectory; and visualizing indications of values of the at least one parameter of the industrial robot as when executing the modified trajectory.

13. The method according to claim 1, further comprising automatically modifying the nominal trajectory to provide the modified trajectory in response to the user input.

14. The method according to claim 13, wherein the automatic modification comprises optimizing the nominal trajectory with a condition to provide a modified trajectory with values of the at least one parameter below a threshold value at least partly along a modified path associated with the modified trajectory.

15. The method according to claim 13, wherein the automatic modification comprises optimizing the nominal trajectory to minimize a time of a movement between two target points along the nominal path.

16. The method according to claim 1, wherein the industrial robot is designed to interact with a human in a shared collaborative workspace.

17. A control system for controlling an industrial robot the control system comprising at least one data processing device and at least one memory having a computer program stored thereon, the computer program comprising program code which, when executed by the at least one data processing device causes the at least one data processing device, to perform the steps of: commanding visualization of a nominal path of the industrial robot, the nominal path being associated with a nominal trajectory, of the industrial robot commanding visualization of indications of values of at least one parameter of the industrial robot as when executing the nominal trajectory, for evaluating a risk potential of a physical contact between the industrial robot and a human; receiving a user input related to the nominal trajectory; modifying the nominal trajectory based on the user input to provide a modified trajectory; and commanding execution of the modified trajectory by the industrial robot.

18. A robot system comprising: an industrial robot; and a control system for controlling the industrial robot, the control system Includes at least one data processing device and at least one memory having a computer program stored thereon, the computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform the steps of: commanding visualization of a nominal path of the industrial robot, the nominal path being associated with a nominal trajectory of the industrial robot: commanding visualization of Indications of values of at least one parameter of the industrial robot as when executing the nominal trajectory, for evaluating a risk potential of a physical contact between the Industrial robot and a human: receiving a user input related to the nominal trajectory; modifying the nominal trajectory based on the user input to provide a modified trajectory; and commanding execution of the modified trajectory by the industrial robot.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0049] FIG. 1: schematically represents a robot system comprising an industrial robot;

[0050] FIG. 2: schematically represents a teach pendant unit of the robot system visualizing a nominal path and indications on a display;

[0051] FIG. 3: schematically represents the teach pendant unit visualizing the nominal path and further indications on the display;

[0052] FIG. 4: schematically represents the teach pendant unit visualizing a modified path and further indications on the display;

[0053] FIG. 5: schematically represents the teach pendant unit visualizing a modified trajectory and further indications on the display; and

[0054] FIG. 6: schematically represents the teach pendant unit visualizing a nominal path and further indications on the display.

DETAILED DESCRIPTION

[0055] In the following, a method of controlling an industrial robot, a control system for controlling an industrial robot, and a robot system comprising an industrial robot and a control system, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0056] FIG. 1 schematically represents a robot system 10. The robot system 10 comprises an industrial robot 12 and a control system 14. The robot system 10 of this example further comprises a teach pendant unit 16 having a display 18. The display 18 does however not necessarily need to be provided on a teach pendant unit 16. The display 18 may for example alternatively be provided on a personal computer.

[0057] FIG. 1 further shows a human 20 and a collaborative workspace 22. The industrial robot 12 and the human 20 can perform tasks in the collaborative workspace 22 concurrently during a production operation.

[0058] The industrial robot 12 of this specific example comprises a first link 24a, a second link 24b rotatable relative to the first link 24a at a first joint, a third link 24c rotatable relative to the second link 24b at a second joint, a fourth link 24d rotatable relative to the third link 24c at a third joint, a fifth link 24e rotatable relative to the fourth link 24d at a fourth joint, a sixth link 24f rotatable relative to the fifth link 24e at a fifth joint, and a seventh link 24g rotatable relative to the sixth link 24f at a sixth joint. One, several or all of the links 24a-24g may also be referred to with reference numeral “24”. The industrial robot 12 further comprises an end effector 26. The end effector 26 is rigidly connected to the seventh link 24g.

[0059] The industrial robot 12 in FIG. 1 is however only one of many examples. The industrial robot 12 may for example also comprise one or more translational joints.

[0060] The control system 14 of this example comprises a data processing device 28 and a memory 30. The memory 30 contains program code, which when executed by the data processing device 28, causes the data processing device 28 to execute, or command execution of, various steps as described herein.

[0061] The control system 14 may be partly or entirely integrated in the teach pendant unit 16. In this case, the control system 14 may communicate with a controller (not shown) of the industrial robot 12.

[0062] The human 20 can work in close proximity to the industrial robot 12 while power to motors of the industrial robot 12 is available. Physical contact between the human 20 and the industrial robot 12 can thus occur within the collaborative workspace 22. The collaborative workspace 22 may be smaller than an operating space of the industrial robot 12. Thus, a part of the operating space of the industrial robot 12 may not be used for collaborative work.

[0063] FIG. 2 schematically represents the teach pendant unit 16. In FIG. 2, the teach pendant unit 16 visualizes the industrial robot 12 and a nominal path 32 of the industrial robot 12 on the display 18. The nominal path 32 is associated with a nominal trajectory 34 of the industrial robot 12. The nominal trajectory 34 is a speed profile of the industrial robot 12 along the nominal path 32.

[0064] In this example, a plurality of target points of the nominal path 32 are also shown on the display 18. In FIG. 2, a first target point 36a, a second target point 36b and a third target point 36c are denoted. One, several or all of the target points may also be referred to with reference numeral “36”. A movement segment is defined between each pair of adjacent target points 36. Each movement segment may be an interpolation, for example a linear interpolation, between two target points 36.

[0065] The teach pendant unit 16 of this example further comprises a plurality of buttons 38. By means of the buttons 38, the user can provide a user input.

[0066] The user input may be related to a modification of the nominal trajectory 34. Various other user inputs as described herein can also be provided by means of the buttons 38.

[0067] As shown in FIG. 2, a plurality of indications 40 are also visualized on the display 18. Each indication 40 represents a value of a parameter of the industrial robot 12 as when executing the nominal trajectory 34. In this example, the indications 40 are arrows indicating a direction and magnitude of a kinetic energy of some of the links 24. The longer the arrow, the higher the kinetic energy. In FIG. 2, the indications 40 show the direction and the magnitude of the respective kinetic energy as when the industrial robot 12 moves between the first target point 36a and the second target point 36b.

[0068] FIG. 3 schematically represents the teach pendant unit 16 visualizing the nominal path 32 and further indications 40 on the display 18. In FIG. 3, the indications 40 show the direction and the magnitude of the respective kinetic energy as when the industrial robot 12 moves between the second target point 36b and the third target point 36c.

[0069] Due to the visualization of the indications 40 of the values of the kinetic energies according to FIGS. 2 and 3, the user can easily perceive a risk potential of a physical contact between the industrial robot 12 and the human 20. For example, in order to fulfill ISO/TS 15066: 2016, a high number of considerations regarding operations of the industrial robot 12 needs to be made. The method of visualizing the nominal path 32 and the indications 40 greatly assists the user in these considerations. The user can thereby see the kinetic energies of one or more links 24 along the nominal path 32. The kinetic energies are associated with the energy transfer in a collision with the human 20. The user can thereby easily assess the severity of a potential collision between the industrial robot 12 and the human 20 in order to make a risk assessment. The aim of such risk assessment is to ensure that a possible physical contact between the industrial robot 12 and the human 20 does not result in harm to the human 20. By means of the method, a risk potential for such contacts can be quickly and intuitively evaluated.

[0070] For example, the user can easily see that the kinetic energy of the seventh link 24g and the end effector 26 is substantially higher when the industrial robot 12 moves from the first target point 36a to the second target point 36b (FIG. 2) than from the second target point 36b to the third target point 36c (FIG. 3).

[0071] Based upon the information obtained from the indications 40, the user may then provide a user input to modify the nominal trajectory 34 in order to reduce the kinetic energy of the seventh link 24g and the end effector 26 between the first target point 36a and the second target point 36c.

[0072] According to one example, the user modifies the nominal trajectory 34 by moving the first target point 36a and by adding an additional target point. In this way, both the nominal path 32 and the nominal trajectory 34 are modified.

[0073] FIG. 4 schematically represents the teach pendant unit 16 visualizing a modified path 42 and a modified trajectory 44. In comparison with the nominal path 32 and the nominal trajectory 34 in FIGS. 2 and 3, the modified path 42 and the modified trajectory 44 in FIG. 4 comprise a moved first target point 36a and an additional target point 36n.

[0074] The teach pendant unit 16 now visualizes the modified path 42. As shown in FIG. 4, the indication 40 illustrates that the kinetic energy of the seventh link 24g and the end effector 26 is now lower between the first target point 36a and the second target point 36b. The user may now save the modified trajectory 44. The modified trajectory 44 is then executed by the industrial robot 12. The nominal trajectory 34 may alternatively be automatically modified to provide the modified trajectory 44, for example by means of optimization.

[0075] FIG. 5 schematically represents the teach pendant unit 16 visualizing a modified trajectory 44, a modified path 42 associated with the modified trajectory 44 and further indications 40 on the display 18. Also in FIG. 5, each indication 40 is illustrative of a direction and a magnitude of a kinetic energy of several links 24 of the industrial robot 12. FIG. 5 differs from FIG. 4 in that instead of modifying the nominal path 32, only the nominal trajectory 34 is modified. In FIG. 5, the nominal trajectory 34 in FIGS. 2 and 3 has been modified by lowering the speed of the industrial robot 12 from the first target point 36a to the second target point 36b. The teach pendant unit 16 now visualizes the modified path 42 (which in this example is the same as the nominal path 32) associated with the modified trajectory 44. As shown in FIG. 5, one of the indications 40 illustrates that the kinetic energy of the seventh link 24g and the end effector 26 is now lower between the first target point 36a and the second target point 36b. The user may now save the modified trajectory 44 according to FIG. 5 for execution by the industrial robot 12.

[0076] FIG. 6 schematically represents the teach pendant unit 16 visualizing a nominal path 32 and further indications 40 on the display 18. In FIG. 6, a workpiece 46 held by the end effector 26 is also shown. In FIG. 6, the movement segments between the target points 36 are illustrated with different line types. The different line types may be substituted for different colors. The line types of the movement segments of the nominal path 32 each constitutes an indication 40 of a magnitude of kinetic energy of the workpiece 46 when being moved along the respective movement segment. In FIG. 6, also kinetic energies of the third link 24c and of the fifth link 24e are visualized by indications 40 of the same type. The line type between the first target point 36a and the second target point 36b may be used to visualize that the kinetic energy of the industrial robot 12 for this movement segment exceeds a threshold value.

[0077] The indications 40 of values of kinetic energies according to FIGS. 2-6 are merely some of numerous possible visualizations for evaluating a risk potential of a physical contact between the industrial robot 12 and the human 20.

[0078] A type of contact may also be displayed and/or considered. The display 18 may for example visualize the indications 40 for either a quasi-static contact or for a transient contact with the human 20. The teach pendant unit 16 may thus be configured to receive a user input indicative of a type of contact.

[0079] A quasi-static contact includes clamping or crushing situations in which the human's 20 body part is trapped between a moving part of the industrial robot 12 and another fixed or moving part of the robot system 10. In such a situation, the industrial robot 12 would apply a pressure or force to the trapped body part for an extended time interval until the condition can be alleviated.

[0080] A transient contact, also referred to as a dynamic impact, describes a situation in which the human's 20 body part is impacted by a moving part of the industrial robot 12 and thus can recoil or retract from the industrial robot 12 without clamping or trapping the contacted body area, thus making for a short duration of the actual contact. The transient contact is dependent on the combination of the inertia of the industrial robot 12, the inertia of the human's 20 body part and the relative speed between the two.

[0081] The relevant inertia of the industrial robot 12 may be computed anywhere along the length of the kinematic chain of the industrial robot 12. An estimation of the inertia may make use of the pose of the industrial robot 12, speeds of the links 24, mass distribution, moving mass and/or contact location.

[0082] Also the effective mass of the industrial robot 12 may be displayed and/or used as a basis for determining a value of the at least one parameter. The effective mass m.sub.R of the industrial robot 12 may be conservatively estimated as a function of the payload capacity of the industrial robot 12 and the mass M of the moving parts of the industrial robot 12. The effective mass m.sub.R of the industrial robot 12 may for example (according to ISO/TS 15066: 2016) be calculated as:

[00001]$\frac{M}{2}+m_L$

[0083] where m.sub.L is the effective payload of the industrial robot 12 and M is the total mass of the moving parts of the industrial robot 12. For example, the kinetic energy may be determined based on the effective mass.

[0084] For each body part, a maximum permissible energy transfer E can be calculated as:

[00002]$E=\frac{F_{\max }^2}{2k}=\frac{A^2{p}_{\max }^2}{2k}$

[0085] where F.sub.max is the maximum contact force for a specific body part, p.sub.max is the maximum contact pressure for a specific body area, k is the effective spring constant for the specific body part, and A is the area of contact between the industrial robot 12 and the human 20. The indications 40 may thus show whether the maximum permissible energy transfer E for a specific body part of the human 20 is exceeded. For example, the indications 40 may be of red color when the energy transfer is higher than the maximum permissible energy transfer E for a particular body part and may be of green color when the energy transfer is lower than the maximum permissible energy transfer E for the particular body part.

[0086] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.