US-12623345-B2 - Path generation method of generating path of robot using command from external apparatus and robot control system

US12623345B2US 12623345 B2US12623345 B2US 12623345B2US-12623345-B2

Abstract

A method of the present disclosure is a path generation method of generating a path of a robot using a command from an external apparatus, including (a) sequentially receiving command information including a control command from the external apparatus, and (b) determining a path position with interpolation between a first target position and a second target position. The step (b) includes (b1) obtaining the path position by performing linear interpolation between the first target position and the second target position, (b2) determining whether or not path speed at the second target position is no lower than lower limit speed, and (b3) correcting the path speed between the first target position and the second target position so as to become no lower than the lower limit speed when it is determined that the path speed at the second target position fails to be no lower than the lower limit speed.

Inventors

Daichi KAWAKAMI
Yuki KIYOSAWA

Assignees

SEIKO EPSON CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230419
Priority Date: 20220420

Claims (4)

1 . A path generation method of generating a path of a robot using a command from an external apparatus, the method comprising: (a) sequentially receiving command information including a plurality of control commands from the external apparatus with a second control period longer than a first control period as a control period of a path related to a plurality of target sub-path positions of a joint of the robot, the first control period corresponding to an interpolation period being defined between a first target position and a second target position next to the first target position; and (b) determining, by a robot controller, the plurality of target sub-path positions in the interpolation period with interpolation using the plurality of control commands representing positions of the joint of the robot on the path between the first and second target positions, wherein the step (b) includes: (b1) obtaining, by the robot controller, each of the plurality of target sub-path positions in each of the first control periods by performing linear interpolation between the first target position and the second target position; (b2) determining, by the robot controller, for each of the plurality of target sub-path positions, whether path acceleration obtained from an interpolation result of the linear interpolation at one of the plurality of target sub-path positions is higher than an acceleration limit; (b3) correcting, by the robot controller, the one of the plurality of sub-path positions to a corrected target sub-path position; (b4) determining, by the robot controller, whether or not path speed at the second target position is no lower than lower limit speed at which a third target position next to the second target position is reached at an estimated arrival time at the third target position when assuming that the path speed at the second target position is accelerated at the acceleration limit to the third target position using a third control command of the plurality of control commands representing the third target position; and (b5) correcting, by the robot controller, the path speed between the first target position and the second target position so that the path speed at the second target position becomes no lower than the lower limit speed when it is determined that the path speed at the second target position fails to be no lower than the lower limit speed, wherein the robot is configured to perform an operation along either the plurality of target sub-path positions without the corrected sub-path position or the plurality of target sub-path positions including the corrected sub-path position.
2 . The path generation method according to claim 1 , wherein the lower limit speed is obtained by subtracting a positional variation due to a speed variation when accelerated at the acceleration limit from the second target position until the third target position is reached from a difference between the third target position and the second target position, and then dividing a value obtained by the subtraction by a value corresponding to a length of the second control period.
3 . The path generation method according to claim 1 , wherein after the step (b5), the step (b) includes: (b6) determining, by the robot controller, whether or not the path speed at the second target position is no higher than upper limit speed at which the third target position is not exceeded at the estimated arrival time at the third target position when assuming that path speed at the second target position is decelerated at a deceleration limit to the third target position, and; and (b7) correcting, by the robot controller, the path speed between the first target position and the second target position so that the path speed at the second target position becomes no higher than the upper limit speed when it is determined that the path speed at the second target position fails to be no higher than the upper limit speed.
4 . A robot control system comprising: a robot having a servo controller; a robot controller configured to transmit a servo control command to the servo controller; and an external apparatus configured to sequentially transmit command information including a plurality of control commands to the robot controller with a second control period longer than a first control period as a control period of a path related to a plurality of target sub-path positions of a joint of the robot, the first control period corresponding to an interpolation period being defined between a first target position and a second target position next to the first target position, wherein the robot controller is configured to execute; (a) processing of sequentially receiving the command information from the external apparatus with the second control period; and (b) processing of determining the plurality of target sub-path positions in the interpolation period with interpolation using the plurality of control commands representing positions of the joint of the robot on the path between the first and second target positions, the processing (b) includes: (b1) processing of obtaining each of the plurality of target sub-path positions in each of the first control periods by performing linear interpolation between the first target position and the second target position; (b2) processing of determining, for each of the plurality of target sub-path positions, whether path acceleration obtained from an interpolation result of the linear interpolation at one of the plurality of target sub-path positions is higher than an acceleration limit; (b3) processing of correcting the one of the plurality of target sub-path positions to a corrected target sub-path position; (b4) processing of determining whether or not path speed at the second target position is no lower than lower limit speed at which a third target position next to the second target position is reached at an estimated arrival time at the third target position when assuming that the path speed at the second target position is accelerated at the acceleration limit to the third target position using a third control command of the plurality of control commands representing the third target position; and (b5) processing of correcting the path speed between the first target position and the second target position so that the path speed at the second target position becomes no lower than the lower limit speed when it is determined that the path speed at the second target position fails to be no lower than the lower limit speed, wherein the robot is configured to perform an operation along either the plurality of target sub-path positions without the corrected sub-path position or the plurality of target sub-path positions including the corrected sub-path position.

Description

The present application is based on, and claims priority from JP Application Serial Number 2022-069465, filed Apr. 20, 2022, the disclosure of which is hereby incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The present disclosure relates to a path generation method of generating a path of a robot using a command from an external apparatus, and a robot control system. 2. Related Art In the past, there has been known a system in which a robot control device controls a robot with a control command from an external apparatus. In JP-A-2020-4364, there is disclosed a motion control method which realizes path control by performing interpolation between command positions when a period between the control commands from the external apparatus is longer than a motion control cycle of the robot. As an interpolation method, in general, it is possible to use quintic spline interpolation or linear interpolation. In a high-order interpolation method such as the quintic spline interpolation, there is performed the interpolation based on a number of pieces of position information, and therefore, there is a problem that it is difficult to change a motion of a controlled object during an operation, and the linear interpolation is preferable as the interpolation method. However, in the simple linear interpolation, there can arise the case in which the path control cannot appropriately be performed. For example, there can arise the case in which the speed becomes insufficient at an end point of an interpolation zone, and it is unachievable to reach a target position at an endpoint of the next interpolation zone. Alternatively, there can also occur the case in which the acceleration in the path exceeds the acceleration limit. SUMMARY According to a first aspect of the present disclosure, there is provided a path generation method of generating a path of a robot using a command from an external apparatus. This path generation method includes (a) sequentially receiving command information including a control command from the external apparatus with a second control period longer than a first control period as a control period of a path related to a target position of a joint of the robot, and (b) determining a path position in each of the first control periods with interpolation between a first target position and a second target position next to the first target position using a first control command representing the first target position and a second control command representing the second target position. The step (b) includes (b1) obtaining the path position in each of the first control periods by performing linear interpolation between the first target position and the second target position, (b2) determining whether or not path speed at the second target position is no lower than lower limit speed at which a third target position next to the second target position is reached at an estimated arrival time at the third target position when assuming that the path speed at the second target position is accelerated at an acceleration limit to the third target position using a third control command representing the third target position, and (b3) correcting the path speed between the first target position and the second target position so that the path speed at the second target position becomes no lower than the lower limit speed when it is determined that the path speed at the second target position fails to be no lower than the lower limit speed. According to a second aspect of the present disclosure, there is provided a robot control system. The robot control system is provided with a robot having a servo controller, a robot controller configured to transmit a control command to the servo controller, and an external apparatus configured to sequentially transmit command information including a control command to the robot controller with a second control period longer than a first control period as a control period of a path related to a target position of a joint of the robot. The robot controller is configured to execute (a) processing of sequentially receiving the command information from the external apparatus with the second control period, and (b) processing of determining a path position in each of the first control periods with interpolation between a first target position and a second target position next to the first target position using a first control command representing the first target position and a second control command representing the second target position. The processing (b) includes (b1) processing of obtaining the path position in each of the first control periods by performing linear interpolation between the first target position and the second target position, and (b2) processing of correcting the path position so that path acceleration obtained from an interpolation result of the linear interpolation becomes no higher than acceleration limit when the path acceleration e