Robot control method and robot control apparatus

Abstract

To enable limitation of acceleration and motor torque without causing resonance due to the speed of a robot when controlling the robot.SOLUTION: A control method includes: creating a speed plan for a normal operation for moving a robot from a start point to an end point on the basis of positions of the start point and the end point, and a speed and acceleration allowed for the robot when controlling the robot so that the robot starts moving from the start point, accelerates, then decelerates, and stops at the end point; and creating a speed plan for an acceleration-limited operation for moving the robot from the start point to the end point by limiting the acceleration in the speed plan for the normal operation according to an acceleration limit value within the allowable speed range. The control method uses the speed plan for the acceleration-limited operation when limiting acceleration or motor torque.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control method for controlling the operation of an industrial robot (hereinafter simply referred to as a "robot"), and a robot control device for implementing such a control method. [Background technology]

[0002] Robots used for workpiece transport and processing generally have multiple arms (also called links) connected in series to a base, each arm equipped with an end effector such as a hand at its tip. The end effector is controlled to move to a specified position. When a target position for the end effector is specified and the robot is operated, it is preferable for the robot to reach the target position in the shortest possible time. To reach the target position as quickly as possible, each axis of the robot is controlled to start moving from a starting point, accelerate at a constant acceleration, maintain a certain speed upon reaching a certain velocity, then decelerate at a constant acceleration until stopping at an end point. The sections where acceleration and deceleration occur are called the acceleration section and the deceleration section, respectively, and the durations of the acceleration and deceleration sections are called the acceleration time and the deceleration time, respectively. The section where a constant velocity is maintained after acceleration ends and before deceleration begins is called the constant velocity section. In this case, a graph with time on the horizontal axis and velocity on the vertical axis, i.e., a velocity graph, will result in a trapezoid, and the area of ​​this trapezoid corresponds to the travel distance. The speed reaches its maximum value in the constant velocity section, and this maximum value is the highest possible speed for movement from a given start point to an end point (this speed is called the maximum operating speed) within the range of the rated maximum speed determined by the robot's mechanism, motor ratings, etc. If the start point and end point are not far enough apart, the robot may switch to deceleration during acceleration without a constant velocity section in between. If there is no constant velocity section in between, a speed graph will form a triangle, and the area of ​​this triangle corresponds to the distance traveled. Normally, these accelerations are set so that the absolute value of the acceleration used for acceleration and the absolute value of the acceleration used for deceleration are equal.

[0003] As described above, a robot has a structure in which multiple arms are connected in series, with one end of each arm connected to a base, and therefore resonance can occur in the robot as it operates. Resonance is likely to occur when the robot is at a specific speed, i.e., a resonant speed. While it is permissible for the robot's speed to cross the resonant speed as it accelerates and decelerates, it is not desirable for the robot's speed in a constant-speed range to match or approach the resonant speed, as this would cause the robot to vibrate significantly. If we call the operation of a robot when it is intended to move as fast as possible and there are no intentional restrictions on speed or acceleration normal operation, the robot is adjusted in advance so that its maximum speed in a constant-speed range during normal operation, i.e., its maximum operating speed, does not match the resonant speed or a speed close to it.

[0004] As a technique for preventing resonance in a robot, Patent Document 1 discloses a technique for calculating an acceleration time when controlling the robot, and when the calculated acceleration time is within a predetermined time range, reducing the acceleration so that the acceleration time reaches the upper limit value (maximum time) of that time range. Patent Document 2 discloses a technique for controlling a robot that supports and transports an object in a cantilevered manner, when the object is moved linearly, such that the sum of the jerk time and the constant acceleration time in the linear movement is a natural number multiple of the resonance period. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-260636 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-21555 Summary of the Invention [Problem to be solved by the invention]

[0006] When operating a robot at a low speed for purposes such as teaching, it is common to use the same acceleration and deceleration times as in normal operation and limit the speed in the constant-velocity section to a desired value compared to normal operation. This type of operation is referred to as speed-limited operation. Because the speed in the constant-velocity section is limited without changing the acceleration and deceleration times, the acceleration during acceleration and deceleration is also smaller than in normal operation, and the generated motor torque is also smaller than in normal operation. Therefore, if for some reason it is necessary to limit the acceleration or motor torque of a robot compared to normal operation, speed-limited operation can be performed. However, when speed-limited operation is performed to limit acceleration or motor torque, the speed after the limit in the constant-velocity section may match or approach the resonant speed, causing the robot to resonate. This resonance cannot be prevented by the techniques described in Patent Documents 1 and 2. This is because, whereas the technologies in Patent Documents 1 and 2 are technologies that prevent vibrations that occur while the robot is accelerating from resonating with the natural vibrations of the robot's mechanism, resonance when the robot is operating at a specific speed is caused by vibrations of the motors on each axis and vibrations based on the angular transmission error of the reducers connected to the motors, and occurs regardless of the robot's acceleration. In order to prevent resonance when the robot's speed is reduced to limit the acceleration or motor torque, it is necessary to further reduce the robot's speed, which results in the desired acceleration or motor torque not being achieved.

[0007] An object of the present invention is to provide a control method that can limit acceleration and motor torque when controlling a robot without causing resonance due to the robot's speed, and a robot control device that can realize such control. [Means for solving the problem]

[0008] According to one aspect of the present invention, a control method for controlling a robot so that the robot starts moving from a starting point, accelerates, then decelerates and stops at an end point includes a first creation step of creating a speed plan for normal operation to move the robot from the starting point to the end point based on the positions of the starting point and the end point and the speed and acceleration allowable for the robot, and a second creation step of creating a speed plan for acceleration-limited operation to move the robot from the starting point to the end point by limiting the acceleration in the speed plan for normal operation by an acceleration limit value within the allowable speed range.

[0009] According to one aspect of the present invention, a robot control device that controls a robot so that the robot starts moving from a starting point, accelerates, then decelerates and stops at an end point creates a speed plan for normal operation to move the robot from the starting point to the end point based on the positions of the starting point and end point and the speed and acceleration allowable for the robot, and when an acceleration limit value is input, creates a speed plan for acceleration-limited operation that moves the robot from the starting point to the end point by limiting the acceleration in the speed plan for normal operation by the acceleration limit value within the allowable speed range. [Effects of the Invention]

[0010] According to one aspect of the present invention, when controlling a robot, it is possible to limit the acceleration and motor torque without causing resonance due to the speed of the robot. [Brief explanation of the drawings]

[0011] [Figure 1] 1A and 1B are a plan view and a front view, respectively, showing an example of a robot to which a control method of an embodiment is applied. [Figure 2] Graphs (a) and (b) show examples of speed planning. [Figure 3] 10(a) and 10(b) are graphs showing another example of a speed plan. [Figure 4] 10(a) and 10(b) are graphs showing yet another example of a speed plan. [Figure 5]10(a) and 10(b) are flowcharts showing a method for controlling a robot. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, an embodiment of the present invention will be described. Fig. 1 shows an example of the configuration of a robot to which a control method of one embodiment is applied, with (a) being a plan view and (b) being a front view. Here, the robot to be controlled is described as a horizontal articulated robot that transports workpieces, but robots to which the control method based on the present invention can be applied are not limited to horizontal articulated robots for transport, and there is no limit to the number of axes in the robot.

[0013] The robot shown in FIG. 1 is used to transport a workpiece, such as a substantially rectangular glass substrate, between multiple processing chambers (not shown) arranged around the robot. Film deposition and etching are performed on the workpiece in each processing chamber. The robot includes a base 11, a first arm 12 attached to the base 11, a second arm 13 attached to the tip of the first arm 12, and a hand 14 attached to the tip of the second arm 13. The hand 14 holds the workpiece and is formed in a fork shape. The first arm 12 is rotatable around axis A relative to the base 11, the second arm 13 is rotatable around axis B relative to the first arm 12, and the hand 14 is rotatable around axis C relative to the second arm 13. To enable rotation around axes A to C, which are the joint axes of the robot, the robot is provided with a motor (not shown) for each axis. The robot also has a mechanism mounted on base 11 that raises and lowers first arm 12 in the Z direction shown in the figure, i.e., the vertical direction, and this raising and lowering mechanism is also driven by a lifting motor. Axes A to C are all parallel to the Z direction. Although the movement in the lifting direction is not a rotational movement, the lifting motor is sometimes called the motor that drives the Z axis.

[0014] As shown in Figure 1(b), a robot controller 30 that controls this robot is connected to the robot. A pendant 32 can be connected to the robot controller 30 via a cable 31 for teaching the robot. The robot controller 30 can drive and control the motors of each axis within the robot based on operation commands input from outside or commands given by teaching using the pendant 32.

[0015] Next, the control of the robot in this embodiment will be described. Because the robot is used to transport workpieces, the operation commands input to the robot controller 30 to operate the robot are commands that specify the position of the robot, particularly the position of the hand 14, and cause the robot to operate. The robot controller 30 has a function for performing speed planning, which generates a speed plan that specifically indicates how each axis should be moved based on the robot positions before and after movement indicated in the operation commands. Because it is better for the workpiece transport time to be short, the robot controller 30 creates a speed plan for normal operation that moves the robot as quickly as possible.

[0016] In this embodiment, the robot control device 30 creates a plan to operate the robot through PTP (point-to-point) motion in order to move the workpiece as quickly as possible. PTP motion generally involves specifying only the start and end points of the trajectory to be taken by the tip of a tool or hand attached to the robot, and then moving the tool or hand. In PTP motion, the start and end points are specified, but the robot's path between the start and end points is not. In particular, for robots with two or more axes, after determining the distance each axis should move between the start and end points, each axis is moved independently according to its own travel distance. In this case, a velocity plan is created so that each axis simultaneously starts and accelerates at the start point, simultaneously ends acceleration, simultaneously begins deceleration, and simultaneously stops at the end point. The period between the end of acceleration and the start of deceleration is a constant velocity section.

[0017] For robots, the maximum operational speed is determined for each axis based on the start and end points. In a speed plan for normal operation, the speed of one axis reaches its maximum operational speed in the constant-velocity section, while the speeds of the remaining axes are below their respective maximum operational speeds. Similarly, for robots, the allowable acceleration is specified for each axis, taking into account factors such as the impact on the workpiece. Acceleration and deceleration times are predetermined based on the maximum operational speed and allowable acceleration. The robot's speed can be defined as 100% when an axis moves at its maximum operational speed in the constant-velocity section. Even if a speed plan does not have a constant-velocity section, the ratio of the speed when switching from the acceleration section to the deceleration section to the maximum operational speed of that axis can be calculated for each axis, and the maximum operational speed of the axis with the largest ratio can be set as 100%.

[0018] When checking the robot's movement path after teaching it, for example, it is necessary to operate the robot at a slower speed than during normal operation. In such cases, a speed limit value is input to the robot control device 30. The robot control device 30 generates a speed plan for speed-limited operation based on the input speed limit value. In the speed plan for speed-limited operation, the acceleration time and deceleration time are the same as those in the speed plan for normal operation, and the speed in the constant-speed section is limited compared to normal operation. For example, when limiting the speed to 40%, the speed in the constant-speed section is set to 40% of that in normal operation. The acceleration time and deceleration time remain unchanged, but the speed in the constant-speed section, i.e., the speed at the end of acceleration, is limited, so the acceleration in the acceleration section and deceleration section is also limited. When limiting the speed to 40%, the acceleration is also set to 40% of that in normal operation.

[0019] It is sometimes desirable to limit the acceleration or motor torque when operating a robot. Because speed-limited operation limits both acceleration and motor torque, conventionally, robots have been operated using speed-limited operation to limit acceleration and motor torque. When speed is limited, an operating speed that deviates from the resonant speed is selected. However, when acceleration or motor torque is limited, speed is not taken into consideration, so there is a risk that the robot's speed in a constant-speed zone will coincide with or approach the robot's resonant speed, causing mechanical vibrations in the robot. In the following explanation, the speed range in which vibrations due to resonance may occur is referred to as the resonant speed range. Using speed-limited operation to limit acceleration and attempting to prevent resonance in the robot may result in the acceleration and motor torque not being able to be set to the desired values.

[0020] Therefore, in this embodiment, when an acceleration limit value is input, the robot control device 30 has a function of creating a speed plan for acceleration-limited operation, i.e., operation in which acceleration is limited by the limit value. In acceleration-limited operation, compared to normal operation, only the acceleration in the acceleration section and deceleration section is limited, and the speed is not limited as long as it is within the range of the maximum speed in normal operation. Because the speed is allowed to reach the maximum speed in normal operation, the acceleration time and deceleration time are longer than in normal operation, and therefore than in speed-limited operation. Even in acceleration-limited operation, if a constant speed section where the speed is 100% is sandwiched between the acceleration section and the deceleration section, the acceleration time and deceleration time are longer than in normal operation in inverse proportion to the amount of acceleration limit.

[0021] 2(a) and 2(b) show examples of speed plans created by the robot control device 30 based on motion commands. FIG. 2(a) shows a speed graph during normal operation when moving the robot from a starting point P to an end point Q1, and a speed graph when the speed is limited to 50% by speed-limited operation. During normal operation, the robot starts moving from the starting point P, accelerates at an acceleration rate of α in an acceleration section with acceleration time Ta, and reaches a speed of 100%. The robot then maintains a speed of 100% in a constant-velocity section with a time length of Tc, decelerates at an acceleration rate of -α in a deceleration section with deceleration time Td, and stops at position Q1. The acceleration time Ta and deceleration time Td are equal. On the other hand, during speed-limited operation, the acceleration time Ta and deceleration time Td remain the same as during normal operation, and the accelerations in the acceleration section and deceleration section are α / 2 and -α / 2, respectively, which are limited to 50% of the acceleration during normal operation. The speed in the constant-velocity section is 50%. By limiting the speed, the time required to reach the end point Q1 in the speed-limited operation is longer than in the normal operation, and the length of the constant speed section is also extended from Tc to Tc1.

[0022] Figure 2(b) shows a speed graph when the acceleration is limited to 50% using acceleration-limited operation when the robot moves from the starting point P to the end point Q1. For reference, the speed graph for normal operation and the speed graph for speed-limited operation shown in Figure 2(a) are both indicated by dashed lines. In acceleration-limited operation, acceleration in the acceleration section is limited to α / 2, and acceleration in the deceleration section is also limited to -α / 2, but speed is not limited. As a result, the robot reaches 100% speed, and the acceleration time Ta2 at that point is twice the acceleration time Ta during normal operation. After the acceleration period, a constant-velocity section (length Tc2) shorter than the constant-velocity section in normal operation is sandwiched, followed by a deceleration section with an acceleration of -α / 2. The deceleration time Td2 is also twice the deceleration time Td during normal operation. At the end of the deceleration section, the robot stops at the end point Q1, but the time required from the starting point P to the end point Q1 is shorter with acceleration-limited operation than with speed-limited operation. This is because a speed-limited operation limits both speed and acceleration, whereas an acceleration-limited operation limits only acceleration and not speed.

[0023] 3(a) and 3(b) also show examples of speed plans created by the robot control device 30, similar to the cases shown in FIGS. 2(a) and 2(b). However, in this example, the robot is moved from the starting point P to the ending point Q2, which is closer to the starting point P than the ending point Q1. FIG. 3(a) shows a speed graph during normal operation and a speed graph when the speed is limited to 25% by a speed-limited operation. FIG. 3(b) shows a speed graph when an acceleration-limited operation is performed, limiting the acceleration to 25%. As shown in FIG. 3(a), the speed graph during normal operation has a shorter constant-velocity section length Tc than that shown in FIG. 2(a), but the acceleration time Ta and deceleration time Td are the same as those shown in FIG. 2(a). In the speed-limited operation, the speed is limited to 25%, and the acceleration and deceleration times are the same as those during normal operation. Therefore, the acceleration in the acceleration and deceleration sections is also limited to 25% of that during normal operation. That is, the acceleration in the acceleration section is limited to α / 4, and the acceleration in the deceleration section is limited to -α / 4.

[0024] On the other hand, as shown in Figure 3(b), in acceleration-limited operation, the acceleration in the acceleration and deceleration sections is limited to 25% of that in normal operation, but the speed is not limited. However, in the example shown here, if the acceleration is set to α / 4 and the robot continues to accelerate to 100%, even if it subsequently decelerates, the robot will pass the end point Q2. Therefore, in this case, a speed plan is created so that the robot transitions from the acceleration section to the deceleration section without a constant speed section in between, and stops at the end point Q2 at the end of the deceleration section. As a result, the speed graph in acceleration-limited operation is triangular rather than trapezoidal.

[0025] 4(a) and 4(b) also show examples of speed plans created by the robot control device 30, similar to the cases shown in FIGS. 3(a) and 3(b). However, in this example, the robot is moved from the starting point P to the ending point Q3, which is closer to the starting point P than the ending point Q2. FIG. 4(a) shows a speed graph during normal operation and a speed graph when the speed is limited to 25% by a speed limiting operation, while FIG. 4(b) shows a speed graph when an acceleration limiting operation is performed to limit the acceleration to 25%. In this example, since the distance between the starting point P and the ending point Q3 is short, the speed graph during normal operation is triangular, with no constant-speed sections. In this example, when the allowable speed of the robot is 100%, the speed during normal operation is a maximum of 75%. However, the theoretical acceleration time Ta and deceleration time Td are defined as the time it takes for the speed to go from 0% to 100% (or from 100% to 0%), so the acceleration time Ta0 during normal operation is 75% of the theoretical acceleration time Ta, and the deceleration time Td0 is also 75% of the theoretical deceleration time Td.

[0026] As shown in Figure 4(a), in speed-limited operation, the robot accelerates at an acceleration rate of α / 4 over acceleration time Ta until it reaches 25% speed, after which it maintains that speed for a constant-velocity period Tc1. After the constant-velocity period ends, it decelerates at an acceleration rate of -α / 4 over deceleration time Td, and stops at end point Q3. As shown in Figure 4(b), in acceleration-limited operation, the acceleration rate is α / 4 but the speed is not limited. As in the case shown in Figure 3(b), the robot transitions from the acceleration period to the deceleration period without a constant-velocity period, and at the end of the deceleration period, the robot stops at end point Q3. The speed graph in acceleration-limited operation is triangular rather than trapezoidal.

[0027] The acceleration-limited operation has been described above. The acceleration-limited operation described above can also be uniformly executed when an acceleration limit is commanded. For example, when no acceleration limit value is input to the robot control device 30, the robot can be moved according to a speed plan for normal operation, and when an acceleration limit value is input, the robot can be moved according to a speed plan for acceleration-limited operation. However, it is also possible to configure the system so that when an acceleration limit is commanded, a speed plan for speed-limited operation is first created, and only when the speed in the constant speed section of that speed plan falls within the robot's resonance speed range is a speed plan for acceleration-limited operation created. In this case, if the speed in the constant speed section of the speed plan for speed-limited operation falls outside the robot's resonance speed range, the robot is controlled by the speed plan for speed-limited operation even if the purpose is to limit acceleration.

[0028] FIG. 5 is a flowchart showing the operation of the robot controller 30 when creating a speed plan for acceleration-limited operation for the first time when the speed plan for speed-limited operation is within the resonance speed range. First, in step 101, the robot controller 30 creates a speed plan for normal operation based on the commanded start and end points. Since the speed plan for normal operation is a commonly used speed plan, it may be created and stored in the robot controller 30 in advance. When a command to actually move the robot is input, the created speed plan for normal operation is called up and the robot is controlled based on this speed plan. Next, in step 102, the robot controller 30 determines whether a command to limit the robot's speed or acceleration has been input. If no such command has been input, the robot controller 30 actually moves the robot according to the speed plan for normal operation in step 103, and then ends the process.

[0029] On the other hand, if it is determined in step 102 that a command to limit the speed or acceleration has been input, then in step 104 the robot controller 30 creates a speed plan for speed-limited operation in which the acceleration time and deceleration time remain the same as in normal operation and the speed is limited as described above. If an acceleration limit value has been input, the speed plan for speed-limited operation is created, assuming that the speed is limited at a rate that corresponds to the rate at which the limit value reduces the acceleration in the speed plan for normal operation. Next, in step 105, the robot controller 30 determines whether or not a command to limit acceleration has been input. If the command is not a limit on acceleration, then the command is a limit on speed. Therefore, in step 106, the robot controller 30 actually moves the robot using the created speed plan for speed-limited operation, and then ends the process. On the other hand, if it is determined in step 105 that an acceleration limit has been specified, the robot control device 30 determines in step 107 whether the speed in the constant speed section in the speed plan for speed-limited operation that has already been created is within the resonance speed range of the robot, and if the speed in the constant speed section is not within the resonance speed range, proceeds to step 106 and actually moves the robot using the speed plan for speed-limited operation, and then terminates the processing.

[0030] If it is determined in step 107 that the speed in the constant speed section is within the resonant speed range, then in step 108 the robot control device 30 creates a speed plan for acceleration-limited operation in which only the acceleration is limited based on the acceleration limit value, as described above, and in step 109 actually moves the robot using the created speed plan for acceleration-limited operation, after which the processing ends.

[0031] As shown in Figure 1, robots generally have a structure in which multiple arms are connected and hands are attached to the ends of the arms, resulting in multiple vibration modes and multiple resonant frequencies, which can result in multiple resonant velocities. When a robot moves, the speed in the constant-velocity section of each axis often differs. Therefore, when the speed in the constant-velocity section of one axis is controlled so that it is outside the resonant speed range corresponding to a certain resonant frequency, the speed in the constant-velocity section of another axis may fall within the resonant speed range corresponding to a different resonant frequency. Therefore, by considering the resonant speed range corresponding to the most significant vibration that can occur in the robot (e.g., the vibration that can have the largest amplitude), and controlling the speed in the constant-velocity section of the axis that is most likely to excite that vibration so that it is outside that resonant speed range, it is possible to suppress the occurrence of resonance in the robot while making control easier.

[0032] According to the control method of this embodiment described above, when it is desired to limit the acceleration or motor torque compared to that during normal operation, it is possible to suppress vibration of the robot by making the robot speed coincident with or approach the resonant speed.

[0033] The configuration for carrying out the present invention has been described above, but the above technology can be configured as follows.

[0034] (1) A control method for controlling a robot so that the robot starts moving from a starting point, accelerates, then decelerates, and stops at an end point, comprising the steps of: a first creation step of creating a speed plan for a normal operation of moving the robot from the start point to the end point based on the positions of the start point and the end point and a speed and acceleration allowed for the robot; a second creation step of creating a velocity plan for acceleration-limited operation in which the acceleration in the velocity plan for normal operation is limited by an acceleration limit value within the range of the allowable velocity, and the robot is moved from the start point to the end point; A control method comprising:

[0035] (2) moving the robot based on the speed plan for normal operation when the limit value of the acceleration is not input; The control method according to (1), wherein when the limit value of the acceleration is input, the robot is moved based on a speed plan for the acceleration-limited operation.

[0036] (3) A control method described in (1) or (2), further comprising a third creation step of creating a speed plan for speed-limited operation in which the speed in the speed plan for normal operation is limited by a speed limit value while maintaining the acceleration time and deceleration time in the speed plan for normal operation, and which moves the robot from the starting point to the end point.

[0037] (4) The limit value of the acceleration is expressed as a ratio to the acceleration in the speed plan for normal operation, and the limit value of the speed is expressed as a ratio to the speed in the speed plan for normal operation, A control method according to (3), in which the third creation process is carried out by regarding the ratio of the acceleration limit values ​​as the speed limit value, and when the speed of the constant speed section in the speed plan for speed-limited operation obtained is not within the resonant speed range of the robot, the robot is moved based on the speed plan for speed-limited operation, and when the speed of the constant speed section in the speed plan for speed-limited operation is within the resonant speed range of the robot, the robot is moved based on the speed plan for acceleration-limited operation obtained by carrying out the second creation process.

[0038] (5) A control method described in any of (1) to (4), wherein the robot has multiple axes and the velocity plan for normal operation is a velocity plan for moving the robot by point-to-point operation from the starting point to the end point.

[0039] (6) A robot control device that controls a robot so that the robot starts moving from a starting point, accelerates, then decelerates, and stops at an end point, creating a speed plan for normal operation of moving the robot from the start point to the end point based on the positions of the start point and the end point and a speed and acceleration allowed for the robot; a robot control device that, when an acceleration limit value is input, creates a speed plan for acceleration-limited operation in which the acceleration in the speed plan for normal operation is limited by the acceleration limit value within the range of the allowable speed, and moves the robot from the start point to the end point.

[0040] (7) A robot control device as described in (6), which controls the robot so that the robot moves based on the speed plan for normal operation when the acceleration limit value is not input, and controls the robot so that the robot moves based on the speed plan for acceleration-limited operation when the acceleration limit value is input.

[0041] (8) A robot control device described in (6) or (7), which creates a speed plan for speed-limited operation in which the speed in the speed plan for normal operation is limited by a speed limit value while maintaining the acceleration time and deceleration time in the speed plan for normal operation, and moves the robot from the starting point to the end point.

[0042] (9) The limit value of the acceleration is expressed as a ratio to the acceleration in the speed plan for the normal operation, and the limit value of the speed is expressed as a ratio to the speed in the speed plan for the normal operation, creating a speed plan for the speed-limited operation by regarding the ratio of the acceleration limit values ​​as the speed limit value; A robot control device according to (8), which controls the robot so that the robot moves based on the speed plan for speed-limited operation when the speed of the constant speed section in the speed plan for speed-limited operation is not within the resonant speed range of the robot, and controls the robot so that the robot moves based on the speed plan for acceleration-limited operation when the speed of the constant speed section in the speed plan for speed-limited operation is within the resonant speed range of the robot.

[0043] (10) The robot has a plurality of axes; A robot control device according to any one of (6) to (8), which creates a velocity plan for the normal operation so that the robot moves from the starting point to the end point by point-to-point operation.

[0044] According to the configurations (1) and (6), the speed plan for acceleration-limited operation limits acceleration but not speed. Therefore, if there is a constant-speed section, the speed there will match the speed in the constant-speed section of the speed plan for normal operation, which is designed to prevent resonance. Therefore, by using the speed plan for acceleration-limited operation, the robot's resonant speed is prevented from matching in the constant-speed section, and resonance due to the robot's speed is also suppressed. In this case, as specified in (2) and (7), by configuring the robot to move based on the speed plan for normal operation when no acceleration limit value is input, and to move based on the speed plan for acceleration-limited operation when an acceleration limit value is input, resonance due to the robot's speed can be prevented throughout the entire operation of the robot when it is actually operated.

[0045] According to the configurations shown in (3) and (8), a speed plan for speed-limited operation is created based on the speed limit value, making it possible to operate the robot at a low speed to check the results of teaching, etc. In this case, by first creating a speed plan for speed-limited operation when limiting acceleration as specified in (4) and (9), it is possible to reduce the sense of incongruity felt by users who are accustomed to conventional operations in which acceleration is also limited by speed-limited operation, and to suppress the occurrence of resonance due to speed.

[0046] According to the configurations (5) and (10), it is possible to suppress the occurrence of resonance due to speed even when controlling a robot having multiple axes with PTP operation. [Explanation of symbols]

[0047] 11...base; 12, 13...arm; 14...hand; 30...robot control device; 31...cable; 32...teaching pendant.

Claims

1. A control method for controlling a robot so that the robot starts moving from a starting point, accelerates, then decelerates, and stops at an end point, comprising: a first creation step of creating a speed plan for a normal operation of moving the robot from the start point to the end point based on the positions of the start point and the end point and a speed and acceleration allowed for the robot; a second creation step of creating a speed plan for acceleration-limited operation in which the acceleration in the speed plan for normal operation is limited by an acceleration limit value within the range of the allowable speed, and the robot is moved from the start point to the end point; A control method comprising:

2. moving the robot based on the speed plan for normal operation when the limit value of the acceleration is not input; 2. The control method according to claim 1, wherein when the limit value of the acceleration is input, the robot is moved based on the speed plan for the acceleration-limited operation.

3. 3. The control method according to claim 1, further comprising a third creation step of creating a speed plan for speed-limited operation in which the speed in the speed plan for normal operation is limited by a speed limit value while maintaining the acceleration time and deceleration time in the speed plan for normal operation, and which moves the robot from the start point to the end point.

4. the acceleration limit value is expressed as a ratio to the acceleration in the speed plan for normal operation, and the speed limit value is expressed as a ratio to the speed in the speed plan for normal operation; 4. The control method according to claim 3, wherein the third creation step is carried out by regarding the ratio of the acceleration limit values ​​as the speed limit value, and when the speed of the constant speed section in the obtained speed plan for speed-limited operation is not within the resonance speed range of the robot, the robot is moved based on the speed plan for speed-limited operation, and when the speed of the constant speed section in the speed plan for speed-limited operation is within the resonance speed range of the robot, the robot is moved based on the speed plan for acceleration-limited operation obtained by carrying out the second creation step.

5. 3. The control method according to claim 1, wherein the robot has a plurality of axes, and the velocity plan for normal operation is a velocity plan for moving the robot from the start point to the end point by point-to-point operation.

6. A robot control device that controls a robot so that the robot starts moving from a starting point, accelerates, then decelerates, and stops at an end point, creating a speed plan for normal operation of moving the robot from the start point to the end point based on the positions of the start point and the end point and a speed and acceleration allowed for the robot; a robot control device that, when an acceleration limit value is input, creates a speed plan for acceleration-limited operation in which the acceleration in the speed plan for normal operation is limited by the acceleration limit value within the range of the allowable speed, and moves the robot from the start point to the end point.

7. 7. A robot control device according to claim 6, wherein when the acceleration limit value is not input, the robot is controlled so that it moves based on the speed plan for normal operation, and when the acceleration limit value is input, the robot is controlled so that it moves based on the speed plan for acceleration-limited operation.

8. 8. The robot control device according to claim 6 or 7, wherein a speed plan for speed-limited operation is created in which the speed in the speed plan for normal operation is limited by a speed limit value while maintaining the acceleration time and deceleration time in the speed plan for normal operation, and which moves the robot from the start point to the end point.

9. the acceleration limit value is expressed as a ratio to the acceleration in the speed plan for normal operation, and the speed limit value is expressed as a ratio to the speed in the speed plan for normal operation; creating a speed plan for the speed-limited operation by regarding the ratio of the acceleration limit values ​​as the speed limit value; 9. A robot control device according to claim 8, wherein the robot is controlled so that it moves based on the speed plan for speed-limited operation when the speed of the constant speed section in the speed plan for speed-limited operation is not within the resonant speed range of the robot, and the robot is controlled so that it moves based on the speed plan for acceleration-limited operation when the speed of the constant speed section in the speed plan for speed-limited operation is within the resonant speed range of the robot.

10. The robot has multiple axes, The robot control device according to claim 6 or 7, wherein a velocity plan for the normal operation is created so that the robot moves from the start point to the end point by point-to-point operation.

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