JPH01281884A - Power control device - Google Patents

Abstract

PURPOSE:To enable a control system to follow up for the abrupt variation of an environmental face stably at a high speed by performing the operation of a power control arithmetic part by such a control constant that the operation of a robot becomes a high speed in the case that the absolute value of a power error value becomes at >= the 2nd set value larger than a 1st set value and in the case of becoming up to the 1st set value. CONSTITUTION:The power control operation of a power control arithmetic part 2 is performed by such a control constant that a control system is stabilized in case of the absolute value of the power error value F which is the deviation of the power command value Fc of the power generated at the robot tip and the power feedback value Ff which is the output of a power sensor processing part 8 being within a 1st set value and in case of this absolute value being up to the 2nd set value larger than the 1st set value from this state. Also, the operation of the power control arithmetic part 2 is performed by such a control constant that the operation of a robot 6 becomes at high speed in case of this absolute value becoming more than the 2nd set value and in case of the absolute value being up to the 1st set value from this state.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a force control device for an industrial robot.

Conventional technological power control devices have been incorporated into robots in recent years, and robots are now able to perform tasks as sophisticated and flexible as humans.

An example of the above-mentioned conventional force control device will be described below with reference to FIGS. 1 and 2.

In FIG. 1, 1 is a force command section which outputs a force command value Fc. 6 is a robot, 11 is a force sensor attached to the tip of the robot, 5 is a motor that drives the robot, and 7 is a position detector attached to the motor 5 for detecting the positioning of the robot.

Reference numeral 8 denotes a force sensor processing unit that processes the force F signal detected by the force sensor 11, which amplifies the minute signal detected by the force sensor 11 and generates a force feedback value Ff corresponding to the force command value Fc.
Output. Reference numeral 2 denotes a force control calculating section which receives the force command value Fc and the force feedback value Ff as input, and is composed of a subtractor 310 and a compliance constant calculating section 9. The subtracter 10 inputs the force command value Fc and the force feedback value Ff, outputs a force error value ΔF which is a subtracted value between the two, and outputs a force error value ΔF, which is a subtracted value between the two.
and converts the force error value ΔF into a position command value Xc (R) in the joint angle coordinate system. However, (R) indicates a value in the joint angle coordinate system. 3 is a position control unit which inputs the position command value Xc (R) and the position feedback value Xf (R> which is the output of the position detector 7), calculates the current command value 1c (
R) is the output. 4 is a motor drive unit that drives the motor 5. FIG. 2 shows the configuration of the force control calculation section 2. 12
is a multiplier that multiplies the force error value ΔF by the compliance constant Kf; 13 is an integrator that integrates the position error command value ΔXc;
14 is a coordinate converter that converts the position command value Xc from the absolute coordinate system W to the position command value Xc (R) in the joint angle coordinate system R.

The operation of the force control device configured as described above will be explained below.

The force command unit 1 outputs a force command value Fc in one direction of a specific coordinate system to the tip of the robot 6.

The force applied to the tip of the robot 6 is detected from the force sensor 11. The detected force F is input to the force sensor processing section 8, which outputs a force Ff in a specific axial direction of the coordinate system designated by the force command section 1, and inputs it to the subtracter 10. The subtracter 10 takes the difference ΔF between the force command value Fc and the force feedback value Ff and sends it to the compliance constant calculation section 9. The compliance constant calculation unit 9 calculates equations (1) and (2).

△Xc=Kf・ΔF ---(1)Xc=Σ△X
c...(2) Compliance calculation section 9
The position command value Xc (R) converted in is sent to the position control section 3. The position command unit 3 calculates the position error value X(R) using the position command value Xc (R) and the feedback value Xf (R) from the position detector 7, and creates the speed command value Vc (R).

Next, speed command value Vc (R) and position feedback value Xf (R>
The speed feedback value Vf(R) calculated from the current command value re(R) is sent to the motor drive unit 4, which generates the current command value re(R).

The motor drive unit 4 controls the current of the motor 5 so that the current value If flowing through the motor 5 matches the current command value 1c (R). The motor 5 drives the robot 6 so that the force error value ΔF becomes zero. When force control is performed as described above, each joint angle Ii is adjusted so that the force feedback MFf matches the force command value Fc in one direction of a specific coordinate system at the tip of the robot 6.
q is controlled.

Problems to be Solved by the Invention However, with the above configuration, when the tip of the robot is moved along an environmental surface as shown in FIG. 8, if the surface changes suddenly, the compliance constant Kf is increased to It is necessary to move the tip at high speed. However, when the tip of the robot is moved along a surface with a high compliance constant, the stability of the control system worsens, and the tip of the arm vibrates at points where the environmental surface suddenly changes, as shown in Figure 8 (a). There was a problem. In addition, when operating with a low compliance constant Kf in consideration of the stability of the force control system, the tip of the robot does not follow changes in the environmental surface and moves away from the environmental surface, as shown in Figure 8 (b). Therefore, there was a problem that the robot's tip would not be able to move the force according to the command.

In addition, as shown in Fig. 9, in order to improve the force control response, when the force feedback value FffJ is smaller than Fc-a, the force is controlled with a high compliance constant Kf, and when it is larger than Fc-a, the force is controlled with a low compliance constant Kf. When control is performed, even if the force feedback value Ff matches the force command value Fc, the integrated position command value Xc is large in the operation mode with a high compliance constant Kf, and the force feedback value Ff further increases. , which had the problem of large overshoot. Furthermore, there is a problem in that when the force feedback value Ff becomes Fc-a, shooting occurs between the high compliance constant mode and the low compliance constant mode.

In view of the above problems, the present invention provides a force control device that allows the tip of the robot to quickly and stably follow sudden changes in the environmental surface when the tip of the robot moves along the environmental surface while controlling the force. The purpose is to

Means for Solving the Problems The invention of claim 1 solves the above problems by providing a robot having N degrees of freedom, a motor for driving the robot, a position detector attached to the motor, and the robot. a force sensor attached to the tip of the robot; a force sensor signal processing unit that processes the signal from the force sensor; a force command unit that outputs a force command value for the force generated at the tip of the robot; a force control calculation unit that receives as input a force command value that is the output of the unit and a force feedback value that is the output of the force sensor processing unit; a position command value that is the output of the force control calculation unit; and a position command value that is the output of the force control calculation unit; and a motor drive section that receives the output from the position control section and drives the motor, and the absolute value of the force error value, which is the deviation between the force command value and the force feedback value, is the force When the command value is within the first set value and when the absolute value of the force error value is within the second set value larger than the first set value from the above state, the force control calculation unit The force control calculation is performed using control constants that make the control system stable, and the absolute value of the force error value from the control mode becomes equal to or larger than the second set value, which is larger than the first set value. If the absolute value of the force error value is within a first set value from the state of It is characterized by a robot with N degrees of freedom, a motor that drives the robot, a position detector attached to the motor, a force sensor attached to the tip of the robot, and a force that processes signals from the force sensor. A sensor signal processing section, a force command section that outputs a force command value generated at the tip of the robot, and a force command value that is the output of the force command section and a force feedback value that is the output of the force sensor processing section are input. a position command value which is the output of the force control calculation part; a position control part which receives the position command value as input; and a motor drive part which receives the output from the position control part as input and drives the motor. A configured force control device.

In order to solve the above-mentioned problem, the invention of claim 2 is configured to control the operation state in which the absolute value of the force deviation value is between the first setting value and the operating state in which the absolute value of the force error value is equal to or higher than the second setting value. The robot is configured to change the position command value calculated by the force control calculation unit to the position command value obtained from the current value of the robot when the absolute value of the force error value switches to within a first set value. It is characterized by

According to the invention of claim 1, the force command value Fc and the force feedback value Ff
If the absolute value of the force error value ΔF, which is the deviation from the force command value Fc, is within the first set value with respect to the force command value If it is within the set value of 2, the force is 1! I Perform the force control calculation of the I calculation section using a control constant that stabilizes the control system, and from the control mode, the absolute value of the force deviation value becomes equal to or greater than the second set value, which is larger than the first set value. If the absolute value of the force error value is within the first set value, the force control calculation section can perform calculations using control constants that increase the speed of the robot's motion. Even if the environmental surface that the robot's tip is in contact with changes suddenly, it can follow the robot at high speed and stably.

Further, according to the invention of claim 2, the absolute value of the force error value, which is the deviation between the force command value and the force feedback value, is the first with respect to the force command value.
If the absolute value of the force error value is within a set value of When the absolute value of the direction difference value is greater than or equal to the second set value which is larger than the first set value from the control mode, and from the above state, the direction difference value is When the absolute value of the direction difference value is up to the first set value, when the force control calculation unit calculates with a control constant that makes the robot move faster, the absolute value of the path difference value is equal to or less than the second set value. When the operating state of the direction difference value is greater than or equal to the set value changes to a state where the absolute value of the direction difference value is between the first set value and the absolute value of the direction difference value switches to within the first set value, the force control calculation unit Since the position command value calculated in can be changed to the position command value obtained from the current value of the robot, overshoot of the force feedback value caused by changing the control mode can be suppressed, and stable force control can be achieved. can.

EXAMPLE Below, a force control device according to an example of the present invention will be described with reference to FIGS. 1 to 4. 1 and 2 show the configuration of a force control device according to a first embodiment of the present invention, which includes a robot 6 having N degrees of freedom, a motor 5 that drives the robot 6, and a motor 5 attached to the motor 5. position detector 7
, a force sensor 11 attached to the tip of the robot 6, a force sensor signal processing unit 8 that processes the signal from the force sensor 11, and a force command value Fc of the force generated at the tip of the robot 6.
A force command unit 1 generates a force command value Fc which is the output of the force command unit 1 and a force feedback value Ff which is the output of the force sensor processing unit 8.
a force control calculation unit 2 which receives as input the position command value Xc which is the output of the force control calculation unit 2; a position control unit 3 which receives the position command value Xc as input; and the output from the position control unit 3 which inputs and a motor drive unit 4 that drives a motor 5.

FIG. 3 shows each control mode of the compliance constant calculation unit 9 for the force feedback value Ff of the force control device of the present invention. Mode A is a mode with a large compliance constant,
Mode B is a mode when the compliance constant is small. In mode A, the responsiveness to the force command value Ff is good, but there is a problem in terms of stability of the force control system, and in mode B, there is no problem in terms of stability, but the responsiveness to the force command value Ff is poor. .

The operation of the force control device configured as described above will be explained.

The force command value Fc is divided into control modes as follows depending on the value of the force feedback value Ff. It operates in mode A until the absolute value of the route difference value ΔF is greater than b or the absolute value of the route difference value ΔF becomes smaller than a from the above state, and the route difference value Δ
It operates in mode B until the absolute value of F becomes smaller than a (or from the above state until the absolute value of ΔF becomes larger than b. In mode 8, the compliance constant K f takes a large value and the same direction With respect to the road difference value ΔF, the position error command value ΔXc becomes larger and the responsiveness of the control system becomes better.

(△Xc=Kf・ΔF... (1> Formula) In mode B, the compliance constant Kf takes a small value, and the response of the force control system deteriorates, but the stability of the control system improves.As can be seen from Figure 3. When moving from mode A to mode B and from mode B to mode A, the force feedback value at the point where the mode changes has a hysteresis of b-a.This hysteresis causes the mode to change. This can suppress the oscillations that sometimes occur in the force control system.

As described above, according to this embodiment, when the tip of the robot performs force control along the environmental surface as shown in FIG. 4, the control system can stably follow sudden changes in the environmental surface. Moreover, there is no oscillation even when transitioning from mode A with a high compliance constant to mode B with a low compliance constant (stable force control is possible).

A second embodiment of the present invention will be described below with reference to FIGS. 5 to 7. This embodiment is different from the first embodiment in that a compliance constant calculating section 9 (see FIG. 1) has a multiplier 12 (see FIG. 2) that multiplies the compliance constant of the first embodiment, as shown in FIG. ) is used instead of the position error command calculator 15 that calculates the position error command value ΔXc from the path difference value ΔF.The calculation performed in the position error command value calculator 15 shown in FIG. From mode A to mode B (see Figure 3) based on the flowchart.
We will explain the operation at the point where we moved to .

■Determine whether it is mode A or not.

■If not in mode A, move to mode B operation.

(2) In mode A, the position error command value ΔXc is calculated using equation (1) (see the first embodiment) based on the path difference value ΔF and the compliance constant.

0th order position command value Xc is calculated.

(Xc=Σ△Xe...Equation (2)) ■ Compare the absolute value of the direction difference value ΔF with a, and if it is larger than a, go to ■, and if it is smaller than a, clear the position command value Xc. , change the position feedback value Xf to the position command value Xc, and shift to mode B. However, the position feedback value XI' is obtained by positive conversion to the absolute coordinate system from the position feedback value Xf(R) of each joint.According to this embodiment, when the position command value Xc is obtained from the direction difference value ΔF, As shown in Fig. 6, this method solves the problem of overshooting of the force feedback value Ff when moving from mode A with a high compliance constant to mode B with a low compliance constant, which occurred in the case of the conventional example, and provides stable force control. becomes possible.

Effects of the Invention According to the invention of claim 1, when the tip of the robot performs force control along the environmental surface, the control system can stably follow sudden changes in the environmental surface at high speed, Moreover, even when the state of mode A with a high compliance constant is transferred to mode B with a low compliance constant, stable force control is possible without oscillation, which has a great effect.

Further, according to the invention of claim 2, it is possible to solve the problem that the force feedback value overshoots when moving from mode A with a high compliance constant to mode B with a low compliance constant, which occurred in the conventional example. Stable force control is possible.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a force control device in an embodiment of the present invention,
FIG. 2 is a configuration diagram of the compliance constant calculation section, FIG. 3 is a graph of the operation mode, FIG. 4 is a schematic diagram showing the operation, and FIG. 5 is a configuration diagram of the compliance constant calculation section of the second embodiment of the present invention. , FIG. 6 is a schematic diagram showing the operation, and FIG. 9 is a graph showing the operation. I: Force command unit, 2: Force control calculation unit, 3: Position control unit, 4: Motor drive unit, 5: ... Motor, 6 ... Robot, 7 ... Position detector, 8 ... Force sensor processing section, 9 ... Compliance constant calculation section, 10. ...Subtractor, 11...Force sensor, ]-3...Integrator, 14...Coordinate converter, 15...... Place I? f error command calculator. Name of agent Patent attorney Toshio Nakagawa
1 Hecon 7' Lianos 1 (Fig. 4 Fig. 5 13-ellipse +4-/!Kurosensacho-ku ku-to ■ faction
Law district - 【≧ ” G'1 faction

Claims (2)

[Claims] (1) A robot with N degrees of freedom, a motor that drives the robot, a position detector attached to the motor, a force sensor attached to the tip of the robot, and processes signals from the force sensor. a force sensor signal processing unit that generates a force command value for the force generated at the tip of the robot; and a force command value that is the output of the force command unit and a force feedback that is the output of the force sensor processing unit. a position command value that is an output of the force control calculation unit, and a position control unit that receives the position command value as input;
a motor drive unit that receives the output from the position control unit as input and drives the motor, and the absolute value of the force error value, which is the deviation between the force command value and the force feedback value, has a first setting with respect to the force command value. The control system stabilizes the force control calculation of the force control calculation unit when the absolute value of the force error value is within the second set value from the above state and is greater than the first set value. When the absolute value of the force error value is greater than or equal to the second set value which is larger than the first set value from the control mode, and from the above state, the absolute value of the force error value is determined. A force control device, characterized in that the force control calculation section performs calculations using a control constant that increases the speed of the robot when the robot is up to a first set value. (2) The operating state in which the absolute value of the force error value is equal to or higher than the second set value changes to the state in which the absolute value of the force deviation value is between the first set value and the absolute value of the force error value becomes the first set value. 2. The force control device according to claim 1, wherein the position command value calculated by the force control calculation unit is changed to the position command value calculated from the current value of the robot when the position command value is changed to within a set value of the robot.