JPH0778030A - Compliance controller - Google Patents

Abstract

PURPOSE:To apply no excessive force to a work and to enable high-speed operation even when compliance is made large by moving a robot arm according to the sum of speed command values calculated from position deviations of plural paths. CONSTITUTION:A position command value variation quantity 32 for compliance operation is obtained from the position deviation 12 obtained by adding a position command variation quantity 26 for compensating the relative displacement between the robot arm and a robot hand to a position command value 11 and a speed command value 102 is obtained by inputting the obtained position deviation 13 to a proportional compensator 101. Further, the force 28 calculated by a force calculation part 27 is subtracted from the force command value 34 obtained by inputting the position deviation 12 to a proportional compensator 33 and the obtained force deviation 35 is inputted to a proportional compensation 103 to obtain a speed command value 104. The composite speed command value 105 which is the sum of those speed command values 102 and 104 is inputted to a speed control system 17 and the speed 18 of the robot arm is passed through an integrator 19 to obtain the position 20 of the robot arm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for performing compliance control on a robot arm and a robot hand connected by a compliance mechanism section.

[0002]

2. Description of the Related Art FIG. 3 schematically shows a compliance mechanism section. Robot arm 1 and robot
The compliance mechanism section 3 between the hand 2 and the hand 2 is provided to prevent the control system from becoming unstable even when the robot hand 2 is brought into contact with a rigid body during force control or compliance control. This enables stable force control and compliance control.

The compliance mechanism 3 includes a spring element 4
And a damper element 5 and a displacement sensor 6.
The displacement sensor 6 is for detecting the relative displacement between the robot arm 1 and the robot hand 2, that is, the amount of expansion and contraction of the spring element 4, and the signal is a signal for the robot arm 1 and the robot during position control. It is used as a position displacement signal with the hand 2 as a force signal applied to the robot hand 2 during force control or compliance control.

When performing a fitting operation or a deburring operation using compliance control, it is desired to increase the compliance. Therefore, conventionally, a compliance control device as shown in FIG. 4 has been used. Hereinafter, a conventional compliance control device will be described with reference to FIG.

FIG. 4 is a block diagram of a conventional position-based compliance control device. In the position-based compliance control device, the compliance operation is realized by calculating the change amount of the position command value from the detected force and the set compliance, and feeding this back to the position command value.

From the position command value 11, the position 20 of the robot arm and the position command value change amount (output 26) for compensating the relative displacement (output 24) between the robot arm and the robot hand are added and subtracted. , The position deviation is 12,
Further, the position command value change amount (output 32) for the compliance operation is subtracted to obtain the position deviation 13. The position deviation 13 is input to the proportional compensator 14, and the speed command value 15
And is input to the speed control system 17 to obtain the speed 18 of the robot arm. The robot arm velocity 18 passes through an integrator 19 to obtain the robot arm position 20.

The relative displacement between the robot arm and the robot hand, that is, the output 24 of the displacement sensor 23 is input to the low-pass filter 25 and the force calculator 27.
The output 26 of the low pass filter 25 is the position command value 1
Positive feedback is given to 1. The force 28 calculated by the force calculator 27 is input to the low-pass filter 29, and its output 30 is input to the proportional compensator 31. Then, the output 32 of the proportional compensator 31 is negatively fed back to the position deviation 12. The proportional compensator 31 is an element (compliance constant) that determines the magnitude of compliance, and the greater the gain, the greater the compliance.

The low pass filter 25 is a filter having an effect of removing the resonance frequency component of the compliance mechanism section, and is provided to prevent the oscillation of the control system due to the feedback of the resonance frequency component. Low in the frequency band below the cutoff frequency of the filter
Since the pass filter 25 can be regarded as "1", the relative displacement (output 24) between the robot arm and the robot hand is directly fed back to the position command value 11 in this frequency band. Thus, the low pass filter 25 realizes both the prevention of the oscillation of the control system due to the resonance and the position compensation of the robot hand.

The low-pass filter 29 is a filter which has an effect of increasing the gain margin when the object is in contact with the object, and in order to increase the gain of the proportional compensator 31, that is, a large compliance. It is provided in order to realize.

On the other hand, in addition to the position-based compliance control device as described above, FIG. 5 is taken into consideration in consideration of overshoot when a robot hand or a work held by the robot hand comes into contact with an object. A force-based compliance control device as shown has also been proposed. FIG. 5 is a block diagram of a conventional force-based compliance control device, in which a force command value is calculated from a position deviation and a set compliance, and force control is performed using the command value as a command value to perform compliance operation. Has been realized.

From the position command value 11, the position 20 of the robot arm and the position command value change amount (output 26) for compensating the relative displacement (output 24) between the robot arm and the robot hand are added and subtracted. , Position deviation 12 is obtained.
The position deviation 12 is input to the proportional compensator 33 and becomes a force command value 34, and the force 28 calculated by the force calculator 27 is subtracted from the force command value 34 to obtain a force deviation 35. The force deviation 35 is input to the proportional compensator 36, becomes a speed command value 37, and is input to the speed control system 17 to obtain the speed 18 of the robot arm. The robot arm velocity 18 passes through an integrator 19 to obtain the robot arm position 20. The proportional compensator 33 is an element that determines the magnitude of compliance (the reciprocal of the compliance constant), and the smaller the gain, the greater the compliance.

The relative displacement between the robot arm and the robot hand, that is, the output 24 of the displacement sensor 23 is input to the low-pass filter 25 and the force calculator 27.
The output 26 of the low pass filter 25 is the position command value 1
Positive feedback is given to 1. The force 28 calculated by the force calculator 27 is negatively fed back to the force command value 34.

The low pass filter 25 is a filter having an effect of removing the resonance frequency component of the compliance mechanism section, and is provided to prevent oscillation of the control system due to feedback of the resonance frequency component. Low in the frequency band below the cutoff frequency of the filter
Since the pass filter 25 can be regarded as "1", the relative displacement (output 24) between the robot arm and the robot hand is directly fed back to the position command value 11 in this frequency band. Thus, the low pass filter 25 realizes both the prevention of the oscillation of the control system due to the resonance and the position compensation of the robot hand.

[0014]

In the conventional position-based compliance control device, it is necessary to provide a low pass filter in the force feedback loop, which causes a delay in the feedback of the force signal. Therefore, even if the object is contacted and the force is detected, the position command value for the compliance operation is not immediately changed. For this reason, there is a problem that the robot goes over the position where it should be stopped and gives an excessive force to the work or the target.

Further, in the conventional force-based compliance control device, unlike the position-based type, there is no delay in force signal feedback, so that the robot hand or the work held by the robot hand comes into contact with the object. It does not give an excessive force to the work or object when doing, but since the speed when moving in space is inversely proportional to the size of compliance, the speed when moving in space is slow when compliance is large. However, there is a problem that it cannot be put to practical use.

The present invention has been made in view of the above problems, and an object of the present invention is to perform a compliance control which does not apply an excessive force to a work or an object at the time of collision and can operate at high speed even when the compliance is increased. To propose a device.

[0017]

In order to solve the above problems, the present invention uses the following means. The robot arm and the robot hand are connected by a compliance mechanism section having at least a spring element, and a displacement sensor that detects the relative displacement between the robot arm and the robot hand, and the output of the displacement sensor to the robot hand In a compliance control device, comprising a force calculation means for calculating a force being applied, and performing compliance control of a robot hand based on the force calculated by the force calculation means, a position command value is changed from the force calculated by the force calculation means. Position command value change amount calculating means for calculating the amount, and a first speed command value for calculating the first speed command value using a value obtained by subtracting the position of the robot hand and the position command value change amount from the position command value. A force command value calculation hand that calculates a force command value using a value calculation means and a value obtained by subtracting the position of the robot hand from the position command value. And a second speed command value calculating means for calculating the second speed command value using a value obtained by subtracting the force calculated by the force calculating means from the force command value calculated by the force command value calculating means, and the first speed command value calculating means. A combined speed command value calculating means for calculating a combined speed command value that is the sum of the speed command value and the second speed command value, and based on the combined speed command value calculated by the combined speed command value calculating means. Move the robot arm.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a compliance control device of the present invention. The compliance control device of the present invention has a configuration in which a position-based compliance control device and a force-based compliance control device are combined, and calculates the amount of change in the position command value from the detected force and the set compliance, The force command value is calculated from the first speed command value obtained by feeding back the change amount of the position command value to the position command value, the position deviation and the set compliance, and this force command value is used as the command value. The compliance operation is realized by setting the combined speed command value, which is the sum of the second speed command value obtained by performing the force control, as the final speed command value.

At the same time that the position 20 of the robot arm is subtracted from the position command value 11, the position command value change amount (output 26) for compensating the relative displacement (output 24) between the robot arm and the robot hand is output. It is added to the position command value to obtain the position deviation 12, and the position command value change amount (output 32) for the compliance operation is subtracted from the position deviation 12 to obtain the position deviation 13. The position deviation 13 is input to the proportional compensator 101 and becomes the first speed command value 102. The proportional compensator 101 has the same function as the proportional compensator 14 of FIG. 4 described in the related art, but the gain of the proportional compensator 101 is the same as that of the proportional compensator 1 shown in FIG.
It is smaller than the gain of 4. Therefore, the low pass filter 29 shown in FIG. 4 is unnecessary in the present invention.

Further, the position deviation 12 is input to the proportional compensator 33 and becomes a force command value 34, from which the force 28 calculated by the force calculator 27 is subtracted,
The force deviation 35 is obtained. The force deviation 35 is input to the proportional compensator 103 and becomes the second speed command value 104. The proportional compensator 33 is an element that determines the magnitude of compliance (the reciprocal of the compliance constant), and the smaller the gain, the greater the compliance. The proportional compensator 103 is the proportional compensator 36 of FIG.
Has the same function as that of the proportional compensator 103
Is smaller than the gain of the proportional compensator 36 shown in FIG.

The combined speed command value 105, which is the sum of the first speed command value 102 and the second speed command value 104, is input to the speed control system 17, and the speed 18 of the robot arm is
Go through the integrator 19 to get the position 20 of the robot arm.

The relative displacement between the robot arm and the robot hand, that is, the output 24 of the displacement sensor 23 is input to the low pass filter 25 and the force calculator 27.
The output 26 of the low pass filter 25 is the position command value 1
Positive feedback is given to 1. The force 28 calculated by the force calculator 27 is negatively fed back to the force command value 34, and the proportional compensator 3
Input to 1. Then, the output 32 of the proportional compensator 31
Is negatively fed back to the position deviation 12. The proportional compensator 31 is an element (compliance constant) that determines the magnitude of compliance, and the greater the gain, the greater the compliance.

The low-pass filter 25 is a filter having an effect of removing the resonance frequency component of the compliance mechanism section, and is provided to prevent oscillation of the control system due to feedback of the resonance frequency component. Low in the frequency band below the cutoff frequency of the filter
Since the pass filter 25 can be regarded as "1", the relative displacement (output 24) between the robot arm and the robot hand is directly fed back to the position command value 11 in this frequency band. Thus, the low pass filter 25 realizes both the prevention of the oscillation of the control system due to the resonance and the position compensation of the robot hand.

In the compliance control device of the present invention,
The gain of the proportional compensator 101 is set to the proportional compensator 1 in FIG.
By making the gain smaller than 4, the low-pass filter of the force feedback loop 201, which is required in the conventional position-based compliance control device, becomes unnecessary, and the delay of the force signal feedback is prevented. There is.

Further, as a route for calculating the speed command value from the position deviation 12, the route 2 in which the gain is a constant value during this period
02 and a route 203 having a value inversely proportional to the set compliance are provided, the velocity command values from the two routes are synthesized, and the synthesized velocity command value 1 obtained by synthesizing
By using 05 as the speed command value, a certain speed command value can be obtained not only when the compliance is small but also when the compliance is large. That is, as shown in FIG. 2, the compliance is large, that is, the gain of the path 203 is small, and the path 2
Even if the speed command value 104 (curve 302) calculated at 03 becomes too small to be practically used, the existence of the speed command value 102 (straight line 301) calculated at the route 202 causes the synthetic speed command value 105 ( The curve 303) can be obtained.

[0026]

As described above, according to the compliance control device of the present invention, the low-pass filter of the force feedback loop, which is required in the conventional position-based compliance control device, becomes unnecessary, and the force signal Since there is no delay in feedback, when the robot hand or the workpiece held by the robot hand contacts the target object and the displacement sensor detects a force, the position command value for compliance operation The change is made immediately, and there is an effect that an excessive force is not applied to the work or the object at the time of collision. Further, as the route for calculating the speed command value from the position deviation, two routes, that is, a route where the gain between them is a constant value and a route where the gain is a value inversely proportional to the set compliance are moved in parallel, and By making the combined speed command value that is the sum the final speed command value, not only when the compliance is small,
Even when the compliance is large, the speed command value can be obtained to some extent, and the working time can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram of a compliance control device of the present invention.

FIG. 2 is a graph showing the relationship between the magnitude of compliance and the calculated speed command value when the compliance control device of the present invention is used.

FIG. 3 is a schematic view of a compliance mechanism section.

FIG. 4 is a block diagram of a conventional position-based compliance control device.

FIG. 5 is a block diagram of a conventional force-based compliance control device.

[Explanation of symbols]

 1 Robot Arm 2 Robot Hand 3 Compliance Mechanism 4 Spring Element 5 Damper Element 6 Displacement Sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B25J 17/02 G G05D 15/01

Claims (1)

[Claims] 1. A displacement sensor for connecting a robot arm and a robot hand with a compliance mechanism section having at least a spring element to detect a relative displacement between the robot arm and the robot hand, and an output of the displacement sensor. The force calculated by the force calculation means in a compliance control device that includes force calculation means for calculating the force applied to the robot hand from the force calculation means, and performs compliance control of the robot hand based on the force calculated by the force calculation means. Position command value change amount calculation means for calculating the position command value change amount from the position command value, and the first speed command value is calculated using a value obtained by subtracting the position of the robot hand and the position command value change amount from the position command value. Force for calculating the force command value using the first speed command value calculating means and the value obtained by subtracting the position of the robot hand from the position command value. Command value calculation means, and second speed command value calculation means for calculating the second speed command value using a value obtained by subtracting the force calculated by the force calculation means from the force command value calculated by the force command value calculation means. , A combined speed command value calculation means for calculating a combined speed command value that is the sum of the first speed command value and the second speed command value, and the combined speed command value calculated by the combined speed command value calculation means A compliance control device that operates a robot arm based on the above.