JP2740691B2 - Control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control method for controlling operations of a plurality of control targets of a robot.

[Conventional technology]

Conventionally, when each operation of a plurality of control targets of a robot is controlled and the robot performs a desired operation by synthesizing the respective operations, a plurality of operation command patterns for causing the robot to execute the desired operation are provided for each control target. , And the plurality of servo systems respectively control a plurality of control targets in accordance with the input. For example, as shown in FIG. 10, when performing a high-speed composite operation of the horizontal motion a in the X / Y-axis direction and the insertion motion b in the Z-axis direction, the robot is moved along the path C. For this purpose, the timing d at which the insertion operation b is started is determined by the moving distance of the horizontal operation a of the robot. In this case, the robot is to ensure insertion of the component is necessary to ensure the linearity of the operation Z _E in the Z-axis direction during insertion of the robot, the linearity of the Z-axis direction of the operation Z _E To secure
The timing d was determined by trial and error.

Also, the case of executing the earth Mi motion as shown in FIG. 4 to the robot, ensuring that the Z-axis direction of the linear portion Z _S is relatively easy, in the servo system, and the speed instruction pulse for the Z axis By managing the feedback pulse for the Z axis, the operation start timing of the control target in the X / Y axis direction can be determined. That is,
As shown in FIG. 4, the feedback pulse for the Z axis is sampled from the controlled object and the robot moves from point S
A timing S ′ at which the robot has moved by Z _S may be obtained, and the operation in the X / Y-axis direction of the robot may be started at this timing S ′.

[Problem to solve the invention]

Straight in the Z axis direction of the operation Z _E when conventionally to perform the combined operation of the insertion operation b of the horizontal operating a and Z-axis direction of the X / Y-axis direction of the robot shown in FIG. 10 as described above at high speed In order to ensure the performance, the timing d is determined by trial and error. Therefore, when there are many such complex operations, the number of times of trial and error increases significantly, and it is almost impossible to execute. Also, guaranteeing the linearity of the motion Z _{E in} the Z-axis direction is a problem of predicting the near-field of the actual trajectory of the robot, and it is impossible to completely guarantee the linearity of the motion Z _{E in} the Z-axis direction. is there.

The present invention solves the above-mentioned drawbacks, and makes it possible to precisely and easily set the generation timing of each operation of a plurality of control targets in order to cause a robot to perform a desired operation by synthesizing each operation of a plurality of control targets. It is an object of the present invention to provide a control method capable of performing the following.

[Means for solving the problem]

In order to achieve the above object, the present invention provides an operation command pattern for causing a robot having a plurality of controlled objects to execute a combined operation of a horizontal operation and a vertical operation to a plurality of servo systems for each of the controlled objects. In the control method of controlling each of the plurality of control targets by following an input in the servo system, the transfer functions of the plurality of servo systems are approximated to a primary transfer function as shown in FIG. Calculate the operation start timing for causing the robot to execute the composite operation based on each of the obtained operation patterns and the delay time due to the primary transfer function by obtaining the actual operation patterns of the control target with respect to the pattern, Each operation of the control target is executed by the servo system in accordance with the operation start timing, and the robot combines the operations with the robot to perform the composite operation. Execute the operation.

〔Example〕

FIG. 3 shows an example of a horizontal turning arm robot controlled by the present invention.

This robot is provided so as to be rotatable about a first arm 2 that is provided to be able to turn in the horizontal direction with respect to a robot main body 1 and a vertical axis joint that is attached to the distal end of the first arm 2. A second arm 3 and a Z-axis 4 movably provided at the tip of the second arm 3 so as to be movable up and down. The first arm 2 and the second arm 3 are centered on a vertical axis joint. It is supported so as to be pivotable in the horizontal direction. The first arm 2 and the second arm 3 are driven by direct drive type driving sources 5 and 6 composed of motors on the joint axes, respectively. The first arm 2 and the second arm 3 are turned. The drive unit 7 is driven by a drive source 7 composed of a motor mounted in parallel with a transmission means 8 such as a pulley, a belt, and a feed screw to move in the vertical direction. The motors 5, 6, 7 are controlled by the control device 9.

 FIG. 2 shows the configuration of the control device 9.

The control device 9 includes servo systems 10, 11, 1 corresponding to the motors 5, 6, 7.
2 and a controller 13, and the servo systems 10, 11, 12
The control target composed of 6, 7 and the mechanical units 2, 3, 4 is controlled.

The servo system 10 includes a position control unit 14, a speed control unit 15, a driver 16, a speed conversion unit 17, and a position conversion unit 18. The servo systems 11, 12 are configured in the same manner as the servo system 10. Pulse generators 19, 20, and 21 are mounted on the axes of the motors 5, 6, and 7, respectively.
19, 20, and 21 are the current positions (rotation angles) of motors 5, 6, and 7, respectively.
Is detected. Note that the pulse generators 19, 20, and 21 may use magnetic sensors or the like that detect the current positions of the motors 5, 6, and 7.

In the servo system 10, the position conversion means 14 converts the pulse signal from the pulse generator 19 into a pulse signal proportional to the current position of the motor 5 and feeds it back to the comparison unit 22. The position control means 14 compares the command signal from the controller 13 with the pulse signal from the position conversion means 18 in the comparison section 22 and outputs the difference to the speed control means 15, and finally moves the motor 5 to the target position. Play a role. When the controlled objects 2 and 5 reach the target position, the comparison result of the comparing unit 22 becomes 0, but the controlled objects 2 and 5 pass over the target position by inertia, and the more the controlled objects 2 and 5 deviate from the target position. The amount of feedback from the position conversion means 18 increases and the
The force acting to return the target to the target position increases, thereby acting like a spring.

The speed control means 15 subtracts a signal proportional to the speed of the control target 2, 5 from the signal of the spring force from the position control means 14. Specifically, the pulse signal from the pulse generator 19 is subjected to F / V conversion (pulse frequency / voltage conversion) by the speed conversion unit 17 and fed back to the comparison unit 23, and the speed control unit 15 receives the spring force from the position control unit 14. The comparison unit 22 subtracts the output signal of the speed conversion unit 17 from the above signal and outputs the result to the driver 16. This is for suppressing vibration such as spring force by the position control means 15 and 19, and makes the motor 5 reach the target position at high speed and with high accuracy. When the shaft position of the motor 5 reaches the target position, the comparison result of the comparison unit 23 becomes 0. However, when the feedback from the speed conversion unit 17 is applied, the higher the speed of the control target 2, 5 at that time, the higher the speed. In addition, a large force acting to rotate the motor 5 in the reverse direction acts greatly to apply a braking to the inertial force, thereby acting as a damper.

 The servo systems 11 and 12 operate similarly to the servo system 10.

Here, the servo systems 10, 11, and 12 are higher-order systems (systems having a large number of integral elements inside), but include a position control unit 14, a motor 5, a pulse generator 19, and a position conversion unit 18. Speed control means 1 compared to loop gain Kp of control loop
5, the loop cane K of the speed control loop A including the driver 16, the motor 5, the pulse generator 19, and the speed conversion means 17 is Kp
If ≪K, the speed control loop A can be approximated to a mere gain 1 (K = 1) element without an integral element. Therefore, the whole of the servo systems 10, 11, 12 can be regarded as a primary system having no oscillation, respectively, and becomes a primary filter as shown in FIG. 8 in terms of a transfer function. The servo system 10,1
As the loop gains Kp of the position control loops become larger, the servo systems 1 and 12 each have a high-performance servo system with good tracking performance. However, the control systems 2, 3, and 4 are more likely to vibrate as an unstable system. Further, Kp is limited by the characteristics of the entire system (the control device 9, the system including the motor and the machine). here,
The transfer functions of the servo systems 10, 11, 12 are regarded as primary transfer functions, and this transfer function is not an inverse transfer function.

 Next, the operation of the control device 9 will be described.

The swing motion of the horizontal swing arm robot is the first arm 2,
Each of the second arm 3 and the transmission means 8 is controlled by a command signal from the controller 13. The controller 13 calculates the operation pattern and operation timing of each of the servo systems 10, 11, and 12 based on data such as the moving distance, speed, acceleration, and linear distance of the control target input from a keyboard or the like as shown in FIG. Then, an operation pattern is output to each of the servo systems 10, 11, 12 at the operation timing to position the control target at the target value.

Now, the controller 13 sends a position command signal (pulse number signal) corresponding to a predetermined rotation angle to the first arm 2 in the servo system 10.
, This position command signal in the servo system 10,
It is converted into a speed command signal by the position control means 14, and further converted into a torque command signal by the speed control means 15. The driver 16 receives the torque command signal from the speed control means 15, generates a current corresponding to the torque command signal, and rotates the motor 5 to drive the first arm 2 with the current. The pulse generator 19 detects the current position of the motor 5 and outputs a pulse number signal proportional to the current position of the motor 5. The pulse signal from the pulse generator 19 is converted into a position signal by the position conversion means 18 and input to the comparison unit 22, where the deviation between the position command signal from the controller 13 and the position signal from the position exchange means 18 is obtained. The position control means 14 outputs a signal corresponding to the deviation, that is,
A signal that makes the deviation amount zero is output.

Further, the pulse number signal from the pulse generator 19 is converted into a speed signal by the speed conversion means 17 and input to the comparison unit 23, and a deviation between the output signal of the position control means 14 and the speed signal from the speed conversion means 17 is obtained. Can be The speed control means 15 outputs a signal to the driver 16 so that the deviation becomes zero.

By such an operation, the servo system 10 is connected to the motor 5 and the first
The control without any response delay is performed by the command signal from the controller 13 for the arm.

Servo systems 11 and 12 are the same as servo system 10 with controller 13
Motors 6, 7 and second arms 3, 3, Z according to command signals from
The axis 4 is controlled.

For example, when the robot 9 executes an arch motion as shown in FIG.
By calculating the start timing d of the Z-axis 4 by approximating 1, 1 and 12 respectively to a primary filter as shown in FIG.
It guarantees the linearity of the Z-axis direction of the operation Z _E of the robot with high accuracy and probability.

When the control device 9 causes the robot to execute an arch motion as shown in FIG. 4, the motion of the robot in the X / Y-axis direction (the motion of the first arm 2 and the second arm 3) starts from the starting point S '. Robot Z at timing d from the start
Time t _S until axial movement (movement of Z axis 4) starts
Is a problem of finding a, the t _S is t _c as shown in FIG. 6, t _f, is decomposed to _{t e t S = (t c} + t f) -t e ...... (1) Can be represented. Here, t _c until instruction completion point for X / Y-axis direction operation from the robot in X / Y-axis direction operation start point S '(point command signal from the controller 13 to the servo system 10, 12 is completed both) This can be known before the controller 13 starts the X / Y axis direction operation. t _f is a delay time from the command end point for the X / Y-axis direction operation to the actual end of the X / Y-axis direction operation of the controlled objects 2 and 3, and is a part predicted by the controller 13.
The t _f can be calculated from the output signal of the primary filter 10 and 11 with respect to the command signal to the servo system 10, 11 from the controller 13. For example, when a primary filter having a time constant of 1 / Kp sec is applied to a command signal having a trapezoidal velocity pattern as shown in FIG. 9, the remaining pulses output from the primary filter from the end of the command signal pattern are Pe. the time t _f until a given by the following equation (2).

It is. Also, t _e is the time to the point of leaving the Z _E from operation end point E of the robot from the Z axis 4 is activated, the seventh
As shown in the figure, it can be decomposed into _tec and _tq . t _ec is the time from the start of the Z-axis 4 in the command signal pattern to the point at which _ZE is left from the robot operation end point E, and can be calculated before the controller 13 outputs the command signal pattern. It is. t _q is a delay time of the actual operation of the control target with respect to t _ec , and is a time predicted by the controller 13. This _tq can be calculated by the equation (2) from the output signal of the primary filter 12 with respect to the command signal from the controller 13 to the servo system 12, but in practice, the inverse operation using time as a solution cannot be performed. Is calculated by preparing a table indicating the relationship between the speed command pattern and _tq in advance and interpolating the data of this table.

Therefore, the control device 9 _calculates t _S = (t _c + t _f ) in the above equation (1)
Seek t _S by the -t _e. In this case, the control unit 9 calculates from the command signal pattern t _c, is calculated by the command signal pattern t _f (2) expression. Furthermore, the control device 9 a t _ec is calculated from the command signal patterns by decomposing the t _e to a t _ec and t _q as described above, is calculated using the table t _q as described above. Then, the control unit 9 outputs a command signal patterns to the servo system 12 to insert operation b is started at the timing d in accordance with t _S.

Since predetermining the start timing d of the insertion operation b at the stage of generating a command signal to the controller 9, the robot, by writing the information of the partial Z _E you want to keep the linearity as well as the operation described in the robot program In addition, the generation timing d can be set accurately and easily without trial and error, and the combined operation of the robot at high speed and high trajectory accuracy can be performed.

Although the above-mentioned robot is a direct drive type horizontal articulated robot, the present invention is similarly applied to a robot having a horizontally turning arm such as a horizontal articulated robot of a deceleration drive type and a robot of a cylindrical coordinate system. Can be applied. Further, the motor 7 is not limited to the Z-axis 4 in the vertical direction,
It may be a rotary drive source for driving other rotating parts, for example, a rotating part other than the arm such as a chuck. The command signal from the controller 13 and the response signal of the servo system are pulses, that is, digital signals, but may be analog signals.

〔The invention's effect〕

As described above, according to the present invention, an operation command pattern for causing a robot having a plurality of controlled objects to execute a combined operation of a horizontal operation and a vertical operation is input to a plurality of servo systems for each of the controlled objects, and the plurality of In a control method of controlling each of the plurality of control targets by following an input in a servo system, each transfer function of the plurality of servo systems is approximated to a primary transfer function, and an actual transfer target of the control target with respect to the operation command pattern is obtained. An operation start timing for causing the robot to execute the composite operation is calculated based on each obtained operation pattern and the obtained operation pattern and a delay time due to the primary transfer function, and each operation of the controlled object is Since the servo system causes the robot to execute the composite operation by synthesizing each of the operations according to the operation start timing, The occurrence timing of each operation of a plurality of controlled objects can be accurately and easily set without performing line-by-line errors, and a combined operation of the robot with high speed and high trajectory accuracy can be performed.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the present invention, FIG. 2 is a block diagram showing an example of an apparatus used for carrying out the present invention, FIG. 3 is a schematic diagram showing an example of a horizontal turning arm robot controlled by the present invention, FIG. 4 is a diagram showing an operation example of the robot, FIGS. 5 to 7 are diagrams showing a command pattern and an actual operation of a controlled object in the above example, and FIG. 8 is an equivalent circuit of a servo system in the above example. FIG. 9, FIG. 9 is a diagram showing a command pattern and Kp, FIG. 10 is a diagram showing an operation example of the robot, and FIG. 11 is a flowchart showing a processing flow of the controller in the above example. 10,11,12 ... servo system, 13 ... controller.

Claims (1)

(57) [Claims] An operation command pattern for causing a robot having a plurality of controlled objects to execute a combined operation of a horizontal operation and a vertical operation is input to a plurality of servo systems for each of the controlled objects, and the plurality of servo systems input the command. In the control method of controlling the plurality of control targets according to each of the following, each transfer function of the plurality of servo systems is approximated to a primary transfer function, and an actual operation pattern of the control target with respect to the operation command pattern is obtained. An operation start timing for causing the robot to execute the composite operation is calculated based on each of the obtained operation patterns and a delay time caused by the primary transfer function, and each operation of the control target is performed by the servo system. A control method characterized by causing the robot to execute the composite operation by executing the operations in accordance with a start timing and combining the operations. .