JPH04267409A - Method and device for compliance control - Google Patents

Abstract

PURPOSE:To provide method and device for compliance control which permits the flexible movement of the drive part of a robot to be freely changed during the operation of the robot and the robot to be used for a wider range of application. CONSTITUTION:Virtual mass parameters, virtual damper parameters and virtual spring parameters used for the operation of generating a compliance track can be changed at least for each period of the track generation operation, respectively. A controller is provided with a common memory 5 storing at least the virtual mass parameters, virtual damper parameters and virtual spring parameters required for the operation of the compliance track generation, these parameters are read at least for each period of the operation of the compliance track generation and updated by a CPU1 which serves as a parameter reading and updating means.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compliance control method and a compliance control device for changing compliance parameters necessary for compliance trajectory generation calculations in compliance control at least every cycle of compliance trajectory generation calculations.

0002

[Prior Art] General industrial robots have high positional rigidity, so they are unsuitable for work in which workpieces come into contact with each other, such as fitting work. Conventionally, they have been used exclusively for picking up or placing parts. ing. To solve these problems, compliance control has been developed as a method to improve the flexibility of the drive parts of industrial robots, such as robot hands. This compliance control uses feedback control to create a tracing mechanism that escapes in the direction in which the external force acts in response to an external force acting on the robot's drive unit, similar to when a spring, damper, etc. is connected to the robot's drive unit. It is something. A typical six-degree-of-freedom compliance mechanism is shown in Figure 3, and a block diagram of a typical compliance control system for realizing such a compliance mechanism using force feedback control without using mechanical springs or dampers is shown. Shown in Figure 4. In FIG. 4, K is a virtual spring coefficient matrix, A is a function using a virtual mass matrix as a variable, Γ is a function using a virtual mass matrix and a virtual damper coefficient matrix as variables, and I is an identity matrix. Also, JP-A-2-212
Publication No. 086 also discloses a control method that performs compliance control using three parameters, a virtual spring, a virtual damper, and a virtual mass, as compliance parameters.

0003

[Problem to be Solved by the Invention] However, in the technology disclosed in the above publication, the compliance parameters are constant during one operation, and it is impossible to change these parameters continuously or at any time. There are limits to the ability to realize the subtle, soft movements of human hands.

The present invention was made in order to effectively solve the problems of the prior art described above, and it is possible to freely change the softness of the movement of the drive part during the operation of the robot. The purpose of the present invention is to provide a compliance control method and a control device that make it possible to use robots for applications.

[0005]

[Means for Solving the Problems] In order to achieve such an objective, the compliance control method according to the present invention has the following features:
The present invention is characterized in that the virtual mass parameter, virtual damper parameter, and virtual spring parameter used in the compliance trajectory generation calculation can be changed at least every cycle of the trajectory generation calculation. Further, the compliance control device according to the present invention includes a shared memory that stores the values of a virtual mass parameter, a virtual damper parameter, and a virtual spring parameter necessary for the compliance trajectory generation calculation, and the above-mentioned parameters stored in this shared memory. a compliance trajectory calculation means that performs a compliance trajectory generation calculation based on the compliance trajectory calculation means, and reads each parameter stored in the shared memory at least every cycle of the compliance trajectory generation calculation, and the content of each parameter used by the compliance trajectory calculation means. The present invention is characterized in that it includes at least a parameter reading/updating means that can update the parameter, and a parameter changing means that changes the value of the parameter read from the shared memory.

[0006]

[Operation] The compliance control method according to the present invention uses three types of parameters as compliance parameters: a virtual mass parameter, a virtual damper parameter, and a virtual spring parameter. Moreover, these parameters can be changed at least every cycle of the compliance trajectory generation calculation. Therefore, in the present invention, for example, in an extremely short period of several milliseconds or less,
At least the above three types of parameters can be updated,
It is possible to achieve soft movements similar to those of a human hand, which cannot be expressed using the vibration equation of a simple spring-mass-damper system.

Further, in the compliance control device according to the present invention, each parameter stored in the shared memory is read by the parameter reading/updating means at least every cycle of the compliance trajectory generation calculation, and each parameter used by the compliance trajectory calculation means is read. The contents of the parameters are updated and the compliance trajectory is calculated based on the updated parameters. Therefore, by having the parameter changing means change the value of the parameter read from the shared memory, it becomes possible to change the value of each parameter used in the compliance trajectory generation calculation in an extremely short period. Note that the means for changing parameters can be a setting device that manually sets parameter change values from the outside, software that rewrites parameters stored in the shared memory using a certain algorithm, or software that rewrites parameters stored in the shared memory using a certain algorithm. Software that controls reading of a large number of parameters stored in the computer can be considered, but is not limited to this.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A compliance control method and control device according to an embodiment of the present invention will be explained in detail below with reference to the drawings. FIG. 1 is a schematic block diagram showing the entirety of a compliance control device according to an embodiment of the present invention, and FIG. 2 is a graph showing a comparison of behavior of a robot drive unit according to compliance parameters.

First, a compliance control device according to an embodiment of the present invention will be explained. As shown in Figure 1,
A compliance control device 2 according to an embodiment of the present invention employs a multi-CPU system connected by a bus 4, preferably a VME bus, and performs control processing necessary for robot control using eight microcomputers, each consisting of a microcomputer. The central processing units (CPU1 to CPU8) share the responsibility.

[0010] The CPU 1 has a function as a parameter reading/updating means, and reads the compliance parameters stored in the shared memory 6 connected by the bus 4 at least every cycle of the compliance trajectory generation calculation, and generates the compliance trajectory. The contents of each compliance parameter used by the calculation means 8 are updated. Also, CPU
1, in this embodiment, normal trajectory generation calculation processing that is not a compliance trajectory is also performed. CPU2
is in charge of joint servo control in the robot and processing control of the interface 10. The CPUs 3 to 8 work together to function as a compliance trajectory calculation means 8, and are configured to perform compliance trajectory generation calculation processing based on the values of the virtual mass parameter, virtual damper parameter, and virtual spring parameter. . Since the compliance trajectory generation calculation requires high-speed calculation, it is preferable that the compliance trajectory calculation means 8 has a processing capacity of, for example, about 2 MFLOPS. On the other hand, since the CPUs 1 and 2 do not require much processing power, they only need to have a processing power of, for example, 4 to 5 MIPS. However, the CPU 1 reads each parameter stored in the shared memory 6 at least every cycle of the compliance trajectory generation calculation.
Sufficient processing power is required for writing into the compliance trajectory calculation means 8.

A servo motor amplifier 12 is also connected to the bus 4 via an interface 10. The servo motor amplifier 12 drives the drive section of the robot body 14 based on the signal from the compliance control device 2. For example, a six-axis force sensor 16 is attached to the drive section of the robot body 14, so that compliance control of the drive section of the robot body 14 can be performed in six degrees of freedom. The external force detected by the six-axis force sensor 16 is input to the compliance control device 2 via the interface 10, used as a variable in compliance trajectory generation calculations, and compliance control is performed. The shared memory 6 stores at least the values of virtual mass parameters, virtual damper parameters, and virtual spring parameters necessary for compliance trajectory generation calculations. A parameter changing means 18 is connected to this shared memory 6. The parameter changing means 18 may be a setting device that manually sets parameter change values from the outside, software that rewrites parameters stored in the shared memory 6 using a certain algorithm, or software that rewrites parameters stored in the shared memory 6 using a certain algorithm. Software that controls the reading of a large number of parameters stored in a computer can be considered, but is not limited to this. If parameter changes are implemented using software, the functions that implement this software are implemented in the CP.
It may be made to be held by U1. In this embodiment, the drive section of the robot body 16 includes X, Y,
Three parallel forces, each parallel to the Z axis, and three forces around each axis.
It is assumed that a total of six external forces including the rotational force act. This control mechanism is conceptually shown in FIG. 3. In compliance control, for example, calculation of the compliance trajectory for a parallel force in the X-axis direction can be obtained by solving the following equation for x. mX(dx2/dt2)+cX(dx/dt-dx'/
dt) + kX (x-x') = sX (fX-f'X), where mX: virtual mass for parallel force in the X-axis direction cX:
Virtual damper kX for parallel force in the axial direction: Virtual spring sX for parallel force in the X-axis direction: Selection coefficient x for parallel force in the X-axis direction: Position on the compliance trajectory in the X-axis direction x': Target trajectory in the X-axis direction Upper position fX: Actual value of parallel force in the X-axis direction f' The basic equations for compliance trajectory generation calculations for parallel forces on the y- and z-axes and rotational forces on the x, y, and z-axes are also similar. In the above formula, mX, cX, kX, sX (mY, cY, kY, s
Similarly, Y, mZ, cZ, kZ, and sZ) are compliance parameters. In this embodiment, these parameters are stored in the shared memory 6, and can be changed by the parameter changing means 18. Next, a compliance control method according to an embodiment of the present invention using such a compliance control device 2 will be described. The CPU 1 performs normal trajectory generation calculations, moves the drive section of the robot body 14, and performs compliance control when the drive section comes into contact with an object. During compliance control, the CPU 1 as a parameter reading/updating means reads each compliance parameter as described above from the shared memory 6.
It is read at least every cycle of the compliance trajectory generation calculation by the compliance trajectory calculation means 8, and the contents of each parameter used by the compliance trajectory calculation means 8 are updated. In the compliance trajectory calculation means 8,
Based on the above-mentioned basic compliance calculation formula, calculations are performed to generate a compliance trajectory, and the robot body 14 is controlled in compliance. During compliance control, the compliance parameters are updated and changed every cycle of the compliance trajectory generation calculation by the cooperation of the CPU 1 and the parameter changing means 18, so it is possible to respond to almost continuous changes in the compliance parameters. become.

In this way, the virtual mass m, the virtual damper c,
By performing the compliance control operation while changing the virtual spring k, the response to external force is as shown in Fig. 2.
Basically, four types of behavior are possible. In Figure 2,
The vertical axis is the position of the robot drive unit, and the horizontal axis is the elapsed time. In the figure, curves A1 and A2 represent virtual mass m,
This is the behavior when the virtual damper c and the virtual spring k are not 0, A1 is a case where 2 (km) 0.5>c, and A2 is a case where 2 (km) 0.5<c. In addition, in curve B, the virtual mass m is 0, and the virtual damper c and the virtual spring k are 0.
This is the behavior when it is not. Moreover, the curve C has a virtual mass m
This is the behavior when the virtual damper c is 0 and the virtual spring k is not 0. Further, in the present invention, since the parameters can be set to arbitrary values, the form of change in behavior in response to external force can take various forms.

[0013]

Effects of the Invention As explained above, according to the compliance control method and control device according to the present invention, three types of parameters, virtual mass parameter, virtual damper parameter, and virtual spring parameter, are used as compliance parameters. can be changed at least every cycle of the compliance trajectory generation calculation, so it is possible to freely change the softness of the movement of the drive part during the robot's operation, which allows for more complex human hand movements. It becomes possible to realize flexible movements similar to those of . Therefore, it is now possible to effectively apply a robot controlled by such a control method and control device to work in which workpieces come into contact with each other, such as precision fitting work or assembly work. This contributes to the automation and labor saving of tasks that previously relied on.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing the entire compliance control device according to an embodiment of the present invention.

FIG. 2 is a graph showing a comparison of behavior of a robot drive unit according to compliance parameters.

FIG. 3 is a schematic diagram showing a typical six-degree-of-freedom compliance mechanism.

FIG. 4 is a block diagram of a typical compliance control.

[Explanation of symbols]

2 Compliance control device 4 Bus 6 Shared memory 8 Compliance trajectory calculation means 14 Robot body 18 Parameter changing means CPU1 Central processing unit (parameter reading and updating means)

Claims (2)

[Claims] Claim 1: In a compliance control method that uses feedback control to realize a tracing mechanism that escapes in the direction in which the external force acts in response to an external force acting on the drive unit of the robot, a virtual mass parameter and a virtual damper used in compliance trajectory generation calculations are provided. A compliance control method characterized in that parameters and virtual spring parameters can be changed at least every cycle of trajectory generation calculation. [Claim 2] A compliance control device that uses feedback control to realize a tracing mechanism that escapes in the direction in which the external force acts in response to an external force acting on the drive unit of the robot, wherein the virtual mass parameter necessary for the compliance trajectory generation calculation is , a shared memory that stores values of a virtual damper parameter and a virtual spring parameter, and compliance trajectory calculation means that performs a compliance trajectory generation calculation based on the parameters stored in the shared memory; a parameter reading/updating means capable of reading each of the parameters at least every cycle of the compliance trajectory generation calculation and updating the contents of each parameter used in the compliance trajectory calculation means; A compliance control device having a parameter changing means for changing.