JPH08339221A - Robot track control method - Google Patents

Abstract

PURPOSE: To smoothly move a robot with no extreme variance of its moving speed by adapting the average one of those target positions set in a prescribed period and controlling the robot so as to move on a track that is decided by the average target position. CONSTITUTION: When the passing points are set between the start and end points, the distances are calculated among these set points. Then each of these calculated distances is divided by a set speed, so that every inter-section moving time is calculated. Thus an acceleration time ta is calculated, and a static period of the time ta is set before the movement start time ts and after the movement end time tf respectively. Then the area of the time ta is successively moved up to a state where the right edge of the area is coincident with the time tf from a state where the left edge of the area is coincident with time 0, and the target position is calculated at every time point as the average value of those coordinates which are set on a polygonal line corresponding to the area of the time ta. Based on the calculated target position, a robot moving plan is produced and the robot locus control is carried out. Therefore, the target position can be smoothly changed regardless of the length of every path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trajectory control method for a robot, and more specifically, it is a trajectory control for smoothing the motion of each path of a robot when moving on a plurality of routes. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, as a trajectory control method for a robot, when moving on a plurality of routes, as shown in FIG. 4, a movement plan is individually created corresponding to each route and created. A method of controlling a robot by synthesizing a plurality of movement plans to create a movement plan for a plurality of routes as a whole has been proposed as the simplest method.

In this method, since a movement plan is created for each route and simply synthesized, the control is simple and the movement target point can be reliably passed. Because acceleration and deceleration are performed,
Stop points corresponding to the number of paths occur, and smooth movement of the robot cannot be achieved. As a trajectory control method aimed at eliminating such inconvenience, a method described in Japanese Patent Laid-Open No. 64-26911 has been proposed.

According to this method, the time required for acceleration / deceleration on each route is made equal to each other, and the deceleration period of each route and the acceleration period of the next route are overlapped (see FIG. 5) to achieve the purpose of each route. Without stopping the robot at a point (or a starting point), it is possible to control the robot by creating a movement plan from the start point to the end point of the movement route including all the routes. Further, in this case, since the deceleration of the previous route and the acceleration of the next route are performed at the same time, there is a high possibility that the target point cannot be passed, but the deviation from the target point is not so large, It is not particularly inconvenient.

[0005]

[Problems to be Solved by the Invention] Japanese Patent Laid-Open No. 64-2691
Even when the method described in Japanese Patent No. 1 is adopted,
If the length of one of the routes is extremely short, deceleration will start before the end of acceleration in this route, and the time required for acceleration / deceleration on the previous route and the next route will be increased. It becomes impossible to make them equal. Also, it is possible to set the time required for acceleration / deceleration to be equal by reducing the acceleration, but in this case,
In the movement plan obtained as a result of the superposition, there is an inconvenience that the movement speeds of the robots greatly differ between a path having a significantly short length and a path having a sufficiently long length (see FIG. 6).

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in controlling a robot so as to move on a moving route consisting of a plurality of routes, there is a route having a remarkably short length. It is an object of the present invention to provide a trajectory control method that can achieve smooth movement of the robot even if it is moving, without causing the movement speed of the robot to vary too much.

[0007]

According to a first aspect of the present invention, there is provided a robot trajectory control method, wherein a plurality of routes, which sequentially combine two routes sharing a target point of a previous route and a starting point of a next route, are used. In performing a trajectory of a moving robot, a straight line is interpolated between a starting point and / or a target point, and a stationary period equal to an acceleration time is set before the first route and after the last route, As a target position of the robot at each time, an average position of the target positions for a predetermined period including the time is adopted, and the robot is controlled so as to move on a locus determined based on the adopted target position.

In the robot trajectory control method according to a second aspect of the present invention, the average position of the target positions for a predetermined period including the time is adopted as the target position of the robot at each time,
This is a method of obtaining an average position in a state where a predetermined weight is given to a target position for a predetermined period. Here, as the weighting,
A triangular pattern and a sine wave pattern can be exemplified.

[0009]

According to the robot trajectory control method of claim 1,
In performing a trajectory of a robot that moves on a plurality of routes that are a combination of two routes that share a target point of the previous route and a departure point of the next route, While interpolating with a straight line, set a stationary period of time equal to the acceleration time before the first route and after the last route, and as the target position of the robot at each time, average the target positions for a predetermined period including that time. Since the position is adopted and the robot is controlled so as to move on the trajectory determined based on the adopted target position, the target position can be changed smoothly regardless of the length of each route. It is possible to achieve a smooth motion of the robot on the locus determined based on. Of course, when this trajectory control method is adopted, since the average position of the target positions for the predetermined period is adopted as the target position, it does not pass the target position, but the deviation from the target position is not so large, which is particularly inconvenient. Does not mean
Also, by limiting the application, this deviation does not pose any problem.

According to the locus control method of the robot of claim 2, when the average position of the target positions of the predetermined period including the time is adopted as the target position of the robot at each time, the target position of the predetermined period is set. Since the average position is obtained in the state where the predetermined weighting is given, the acceleration / deceleration pattern of the robot can be obtained in correspondence with the weighting, and the robot can be moved in the optimum acceleration / deceleration pattern according to the application.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings showing embodiments. FIG. 1 is a flow chart for explaining an embodiment of a robot trajectory control method of the present invention. Note that the following description is premised on that the robot is moved at a constant speed. Further, the movement of the robot means, for example, movement of the arm hands of the robot.

When a point to be passed between the start and end points is set, in step SP1, the set points are connected by a straight line and the distance between the set points is calculated.
The required travel time of each section (section defined by the set points) is obtained by dividing each distance by the set speed. In step SP2, the acceleration time ta (for example, a value obtained by dividing the set speed by the previous acceleration) is obtained, and the movement start time t
Before s and after the movement end time tf, the stationary period of time ta is set (see FIG. 2). After that, step SP
3, the area at time ta is sequentially moved from the state where the left end thereof coincides with time 0 to the state where the right end thereof coincides with time tf, and the target position at each time point is changed to time ta.
It is calculated as the average value of the coordinate values on the polygonal line corresponding to the area. Then, in step SP4, a movement plan for moving the robot is created based on the calculated target position, and the trajectory control of the robot is performed.

By performing the above trajectory control, the target position of the robot becomes as shown in FIG. Note that FIG.
FIG. 3 shows only the time change of the X coordinate value, and the velocity in the X coordinate direction is not constant velocity, but by considering the velocity in the Y coordinate direction (not shown), constant velocity movement between the start and end points is achieved. Has been done. Further, the generated route does not pass through the set waypoints, but since this deviation is not so large, there is no inconvenience. Further, by limiting the use, this deviation does not pose any problem.

In particular, if the speed of the robot is increased, when the method described in Japanese Patent Laid-Open No. 64-26911 is adopted, the number of routes in which deceleration is started before acceleration is completed increases. In addition, since the robot has a strong tendency to speed up, by adopting this method, it is possible to achieve trajectory control with considerably high accuracy without impairing the high speed movement of the robot.

In the above embodiment, when calculating the target position, the simple average value of the coordinate values on the polygonal line corresponding to the area of the time ta is calculated. However, instead of the simple average value, a triangle is used. You may make it calculate an average value in the state where the weighting of the shape was given. In this case, the acceleration pattern has a triangular shape, and it is possible to prevent residual vibration at rest and suppress damage to the robot. Further, the average value may be calculated in a state where the sine wave weighting is applied, and in this case, the high-frequency nonlinear vibration component can be significantly reduced. Of course, other weighting patterns can be adopted.

[0016]

According to the first aspect of the present invention, the target position can be changed smoothly regardless of the length of each path, and the smooth motion of the robot on the locus determined based on the target position can be achieved. It has the unique effect of being able to do it. The invention of claim 2 has a unique effect that the acceleration / deceleration pattern of the robot can be obtained corresponding to the weighting, and the robot can be moved in the optimum acceleration / deceleration pattern according to the application.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an embodiment of a robot trajectory control method according to the present invention.

FIG. 2 is a diagram showing a state in which a plan to move each section at a constant speed is made, and a stationary period is set before and after the plan.

FIG. 3 is a diagram showing a target position when the trajectory control of FIG. 1 is performed.

FIG. 4 is a diagram showing a movement plan according to a conventional method.

FIG. 5 is a diagram showing a movement plan according to another conventional method.

FIG. 6 is a diagram for explaining an inconvenience caused by another conventional method.

Claims (2)

[Claims] 1. A trajectory control method for a robot that moves on a plurality of routes, which is formed by sequentially combining two routes that share a target point of the previous route and a departure point of the next route, the starting point and / or Alternatively, a straight line is interpolated between the target points, and a stationary period with a time equal to the acceleration time is set before the first route and after the last route, and as a target position of the robot at each time, a predetermined period including that time is set. The locus control method for a robot, characterized in that the average position of the target positions is adopted and the robot is controlled so as to move on a locus determined based on the adopted target position. 2. When the average position of the target positions of a predetermined period including the time is adopted as the target position of the robot at each time, the average position is set with a predetermined weight given to the target position of the predetermined period. The trajectory control method for a robot according to claim 1, which is obtained.