Control method for a robot

Abstract

The invention relates to a control method for a robot (1) having a plurality of movable robot axes (2, 4, 6), in particular for a painting robot (1) or a manipulating robot, comprising the following steps: (a) predetermining a robot path by means of a plurality of path points through which a reference point of the robot (1) is intended to travel; (b) controlling drive motors of the individual robot axes (2, 4, 6) according to the predetermined robot path, such that the reference point of the robot (1) travels through the predetermined robot path; (c) precalculating the mechanical loading (My1, Mx1, Fx1, Fy1, Fz1, Fx2, Fy2, Fz2, Mx2, My2, Mz2) that occurs within at least one of the robot axes (2, 4, 6) between two joints when travelling through the robot path ahead; and also (d) adjusting the control of the drive motors of the robot axes (2, 4, 6) on the basis of the precalculated mechanical loading (My1, Mx1, Fx1, Fy1, Fz1, Fx2, Fy2, Fz2, Mx2, My2, Mz2), such that a mechanical overload is avoided.

Claims

1. A method for controlling a robot having several movable robot axes, wherein the robot axes are each pivotable, the method comprising: specifying a robot path through a plurality of path points, to be traversed by a reference point of the robot; controlling drive motors of respective individual robot axes in accordance with the robot path, so that the reference point of the robot traverses the path points, precalculating at least one tilting moment within at least one robot axis that is predicted to occur when traversing the upcoming robot path, the controlling of the drive motors being adapted depending on the at least one precalculated tilting moment.

2. The method according to claim 1, wherein the at least one tilting moment occurs between two joints.

3. The method according to claim 1, further comprising: comparing the at least one tilting moment with at least a limit value for detection of an upcoming mechanical overload; and braking movement of the reference point on the robot path when an upcoming mechanical overload is detected.

4. The method according to claim 1, wherein the drive motors of the robot axes are each controlled by respective position controllers, the position controllers receive target values from a central robot control, the central robot control outputs the target values clocked with an interpolator clock-pulse to the position controllers, and pre-calculation of the at least one tilting moment is clocked in the interpolator clock-pulse.

5. The method according to claim 1, wherein the at least one tilting moment is pre-calculated multi-dimensionally; and during the pre-calculation of the at least one tilting moment, each of torques and forces are calculated.

6. The method according to claim 1, further comprising: specifying a coordinate system having a coordinate origin that is within one of the robot axes and fixed relative to the one of the robot axes, whereby the coordinate system moves along with the robot axis; selecting at least one of forces and torques that arise in the coordinate system during the movement of the robot; and determining the at least one tilting moment from the selected forces and/or torques.

7. A robot control for controlling a robot having several movable robot axes, wherein the robot control is configured to carry out the method according to claim 1.

8. A robot system, comprising: at least one multi-axis robot, in particular a painting robot or a handling robot, and a robot control according to claim 7.

Description

(1) Other advantageous developments are characterized in sub-claims or are explained in more detail below together with the description of the preferred exemplary embodiment of the invention on the basis of the figures. The figures show as follows:

(2) FIG. 1: a perspective view of a painting robot, which is controlled in accordance with a control method; and

(3) FIG. 2: a flow diagram illustrating an exemplary control method.

(4) FIG. 1 shows a painting robot 1 that can be used, for example, for painting motor vehicle body parts in a painting installation.

(5) In this exemplary embodiment, the painting robot 1 has a robot base 2, which is rotatable about a vertical rotation axis 3. Other painting robots, the robot base of which is arranged stationary or linearly moveable along a guide rail, could be used in the context of the present disclosure.

(6) A proximal robot arm 4 is pivotably mounted on the robot base 2, wherein the robot arm 4 is pivotable about a horizontal pivot axis relative to the robot base 2.

(7) A distal robot arm 6 is pivotably mounted on the distal end of the proximal robot arm 4, wherein the distal robot arm 4 is pivotable about a horizontal pivot axis 7 relative to the proximal robot arm 4.

(8) A multi-axis robot wrist 8, which is known for guiding a conventional rotary atomizer 9 in a highly mobile manner, is attached to the distal end of the robot arms 6.

(9) The painting robot 1 is controlled by a robot control 10, which is known. The robot control 10, however, carries out a novel control method to avoid a mechanical overload of the painting robot 1 during the operation of the painting robot 1. The robot control 10 calculates mechanical loads, which occur within the robot base 2, within the robot arm 4, or within the robot arm 6.

(10) For example, a coordinate system 11 can be set, having its coordinate origin within the proximal robot arm 4. During pre-calculation of the mechanical load, forces Fx2, Fy2, Fz2, and torques Mx2, My2, Mz2, can then be pre-calculated in the coordinate system 11 during the operation of the painting robot 1.

(11) In addition, FIG. 1 shows a further coordinate system 12, having its coordinate origin in the swivel joint between the robot base 2 and a floor. In the coordinate system 12, mechanical loads likewise occur in the form of forces Fx1, Fy1, Fz1, and torques Mx1, My1, Mz1, which are also taken into account within the context of the present control method. In this exemplary embodiment, for example, the tilting moments Mx1, My1, and the forces Fx1, Fy2, which are oriented at a right angle to the rotation axis of the swivel joint, are monitored.

(12) In the following, the present control method will now be described with reference to the flow chart shown in FIG. 2.

(13) In a first step S1, a coordinate system is predefined, having its coordinate origin within one of the robot axes and being spatially fixed on the robot axis, so that the coordinate system moves along with the robot axis. For example, the pre-defined coordinate system of this step S1 can be the coordinate system 11 represented in FIG. 1.

(14) In a further step S2, forces and/or torques to be monitored in the coordinate system are then defined. For example, the torque My2 and the force Fx2 could be defined in the coordinate system 11, and the torques Mx1 and My1 could be defined in the coordinate system 12.

(15) In a further step S3, a trajectory of the Tool Center Point (TCP) is then specified as a sequence of path points, wherein each path point is defined by Cartesian space coordinates.

(16) During the actual operation of the painting robot 1, the individual position controllers of the robot axes are then controlled by the central robot control for the robot 1 to traverse the predetermined trajectory, which corresponds to step S4 and is known.

(17) When traversing the predefined trajectory, the forces to be monitored (e.g., the torques Mx1, My1, My2, and the force Fx2) are then pre-calculated in a step S5 in order to detect any upcoming mechanical overload in time to respond thereto.

(18) In a step S6, the pre-calculated forces and moments are then compared with permissible limit values.

(19) In a step S7, checks are made to see whether the mechanical load is about to be exceeded.

(20) If the mechanical load is about to be exceeded, counter-measures are initiated in a step S8, which counter-measures can include slowing the robot movement via braking.

(21) In a step S9, checks are then made to see whether the end of path is reached or whether the robot 1 movement has been stopped for any other reasons. Otherwise, the steps S4-S9 are repeated in a loop.

(22) The invention is not limited to the previously described preferred exemplary embodiment. Instead, many variants and modifications are possible, which also make use of the concept of the invention and thus fall within the scope of protection. Furthermore, the invention also claims protection for the subject-matter and the features of the subclaims independently of the claims to which they refer.