JPS63237103A - Robot controller - Google Patents

Abstract

PURPOSE:To improve the precision of control by lowering the gain of a closed loop control system so as to stably increase an area and at the same time combining an opened loop control system. CONSTITUTION:A hybrid control type robot controller of a position and a force is constituted of compliance selection matrixes 14 and 21 which decide a coordinate axis for executing a force control, matrixes 13 and 16 which decide the coordinate axis for executing the position control, a matrix 15 which converts the error command value of the position from the hand coordinate system to the joint coordinate system of a robot, a matrix 18 which converts the error command value of the force from the hand coordinate system to the joint coordinate system of the robot and a matrix 25 which converts the advanced speed of the robot from the hand coordinate system to the joint coordinate system. And by providing a control system which adds the command of the opened loop with the command of the closed loop at the time of controlling the force of the robot so as to convert the outputted value into the joint coordinate system and sets the signal as the speed command signal of a servo amplification part 2, the stable area of the loop can made wider.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a robot control device that can provide flexibility to the tip of a robot when the robot is applied to assembly work or the like.

In order to apply conventional technological robots to assembly work, it is necessary to solve various problems. One way to do this is to add a force control function to the tip of the robot, allowing it to move flexibly. However, in conventional force control, there are several problems that need to be solved before it can be put into practical use.

An example of the conventional robot control device having the above-described force control function will be described below with reference to the drawings.

FIG. 2 is a configuration diagram of a conventional robot control device having a force control function. In Fig. 2, 1 is a control calculation section, 2 is a servo amplifier section, 3 is a motor, 4 is a robot arm, and 5 is a servo amplifier section.
is a force sensor attached to the tip of the robot arm, 6
Reference numeral denotes a force calculation unit that processes the output of the force sensor 6, 7 a sensor that detects the position and speed of the motor, and 8 a position/speed calculation unit that calculates the position and speed of the tip of the robot. Also,
Xd" is the command position signal, Fd" is the command force signal, where is the position of the robot's tip, and g is the speed of the robot's tip, F9''
is the reaction force generated at the tip of the robot, and lVa is the speed command value to the servo amplifier unit 2. FIG. 3 shows a block diagram of the force control function section in FIG. In FIG. 3, reference numeral 9 denotes a calculation unit that converts the force error command value ΔF from the robot's hand coordinate system (C) to the joint coordinate system (q);
o is the gain and ξ11 is the stiffness K of the environment that the robot comes into contact with.
e, 12 is a force sensor attached to the tip of the robot.

Xs" is the position of the environment where the tip of the robot comes into contact, the door is the force generated by the contact between the position of the robot's tip and the environment position Xs, and T is the sampling time of the control system. Figure 4 shows the stability in the force control system and the system gain Kf,
The relationship between environmental stiffness Ke and sampling time T is shown.

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

First, the control calculation unit 1 of the robot control device calculates the position command value
d", force command value Fd", position of the robot's tip X", speed of the robot's tip, or force yg of the robot's tip" to generate a speed command value JVc, output it to the servo amplifier section 2, and output it to the servo amplifier section 2. The unit 2 drives the motor 3 attached to each arm of the robot to an environment where a position command value Xd" and a force command value Fd" can be obtained. Each motor 3 drives a robot arm 4, and the tip of the robot arm 4 generates a reaction force F when it comes into contact with the environment. It detects the force F" generated by the nine-piece f5 attached to the tip of the arm, and uses the force calculation section to calculate the robot's...
) is converted into a force Ftg''2 and fed back to the control calculation unit 1.A sensor 7 is attached to each motor 3 to detect the position and speed, and the output of the sensor is sent to the position/speed calculation unit 8. Input 17, and the position of the robot's tip in the robot's hand coordinate system CC) are calculated and fed back to the control calculation unit 1.

If we pay attention to the force control system in the above configuration, we get the block diagram shown in FIG. As shown in Figure 4, the stable region of the control system is defined by the system sampling time T and the system gain Kf.
and the stiffness of the environment Ke. The shorter the sampling time T of the control system or the lower the gain of the system, the greater the stable region of the control system. Furthermore, the environmental rigidity Ke is determined by the environment with which the tip of the robot comes into contact, and the smaller the environmental rigidity Ke, the greater the stable region of the control system.

However, in the configuration as described above, the stability of the control system depends on the stiffness of the environment Ke, so if the stiffness of the environment is fixed as shown at point A in FIG. Even if the sampling time T and system gain Kf are determined so that the control system becomes stable, if the stiffness of the environment changes and Ke becomes larger, the conditions will move to point B and the control system will enter the unstable region. It had the problem of being stored away.

In view of the above problems, the present invention provides a robot control device that combines an open-loop control system and a closed-loop control system, and is more practical than ever, expanding Annaka's ode to force control systems.

Means for Solving the Problems In order to solve the above problems, the robot control device of the present invention includes a first detection means for detecting the force applied to the tip of the robot arm, and a predetermined force command. a first calculation means for calculating the difference between the command force signal and the first force signal, which is the force detected by the first detection means; and a second calculation means for amplifying the output of the first calculation means. calculation means, a command force signal serving as the predetermined force command, and the second
a third calculation means for calculating the sum of the output of the calculation means;
and fourth calculation means for converting a force error command signal output from the third calculation means into a joint coordinate system of the robot arm, and converting the output of the fourth calculation means to each joint of the robot arm. It is composed of a control device that has a control system that issues speed commands to a servo amplifier section that drives a motor installed in the motor.

The present invention solves the problem of the narrow stability region of conventional robot control devices having a force control function by lowering the gain of the closed-loop control system and increasing the stability region, and at the same time solves the problem of the narrow stability region of the conventional robot control device having a force control function. This problem can be solved by combining loop control systems to improve control accuracy.

Embodiment Below, a robot control device having a force control function according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a position-force hybrid control type robot control device according to an embodiment of the present invention.

In Figure 1, S in 14.21 is a compliance selection matrix that determines the coordinate axis for force control, and I in 13.16
-8 is a matrix that determines the coordinate axes for position control, 1 of 16
1-1 converts the position error command value into the robot hand coordinate system (
C) to the joint coordinate system (q), 17 is the position loop gain, 26.28 is the subtraction a27 is the adder, 22
is an adder/subtractor, 18-1 yellow 1 is a matrix that converts the force error command value from the robot's hand coordinate system [C] to the joint coordinate system (q), 190Kf is the force loop gain, and 2° Kq is the force error command value. The gain of the closed loop system, 11-1 of 26, is the velocity of the tip of the pot... from the joint coordinate system ICE to the joint coordinate system [q
], the matrix to be converted into 24 is the velocity loop gain, 2
is the servo amplifier section, 3 is the motor, 4 is the robot arm,
110Ke is the stiffness of the environment, 12 is a force sensor, and 1 nail 23 is a matrix for converting the force reaction force F'' from the hand coordinate system (C) to the joint angle coordinate system (q). Error command value, ΔF is the force error command value in the closed loop, ΔF2 is the sum of the force command value in the open loop and the force error command value in the closed loop, 1Vax is the position command signal, IV a f is the force command signal, iVl is the speed feedback value, lVa
is the speed command value to the servo amplifier section, Xd" is the command position signal, Fd" is the command force signal, x+, i" is the position and speed of the tip of the robot arm, and y+ is generated when the robot arm contacts the environment. The force, yg'', is determined by the output from the force sensor.

Regarding the robot control device configured as above,
The operation will be explained below using FIG.

The position of the tip of the robot arm 4 is displaced (X'' - Xe'') due to contact with the position Xs'' of the environment, and a reaction force F'' is generated in proportion to the magnitude of the rigidity Ke of the environment. The generated reaction force F'' becomes a reaction force to each joint through a distribution matrix T''23 to each joint axis. In addition, the reaction force F'' generated at the tip of the arm is detected as Fq through the force sensor 2 attached to the tip of the arm, and is detected as the hand coordinate system (C) through the compliance selection S that determines the coordinate axis for force control.
Force is returned only to the axis where force control is performed. In Fig. 1, the force error command value ΔF in the closed loop is (1) Equation 0 % The gain in the force closed loop is 9 and Kf,
As shown in FIG. 4, in order to widen the stability region of the control system and practically maintain a stable state even against changes in the environmental stiffness Ke, it is necessary to increase the gain Kq and! needs to be made smaller.

However, there is a problem in that when the gain and Kf are made small, a large error occurs between the command forces S and Fd and the actually generated force 5sF-.

Now, as an open loop, the command force Fd"・S is
Calube gain Kf19 is directly input to servo amplifier section 2 and is used to make the unit of speed command signal IVa to the servo amplifier unit 2 and the unit of command force Fd"・S the same.The torque of each motor 3 is When T is assumed, the relationship with the command signal IVa to the servo amplifier section 2 is expressed as follows, considering that the speed of the motor is very slow.

T=f-lVa...
...(Also, if we consider that there is no reduction gear between the motor and the arm between the force F'' generated at the tip of the arm and the torque T generated by the motor, then equation '4 holds true. .

Door = (1 arm) - 1T ...... (Therefore, by controlling the command signal to the servo amplifier section 2, it is possible to obtain a value close to the command force S - Fd" at the tip of the arm. However, since it is an open loop, it is not possible to obtain accurate values compared to a closed loop.

The force command value ΔF2 output from the adder 27 of the force control loop in FIG. 1 is obtained by adding the open loop and closed loop command calculations (K as shown in equation 4).

ΔF −9@Fd”+Kg −(Fd” −F9”)
S-...←) Furthermore, the force command signal IVai to the servo amplifier section 2 is (
It can be written like the 549 formula.

JVa f = Kf ・1” ・ΔF2 ・・
・The position command signal IVax to the axis that performs position control in the music/reflection or hand coordinate system [0 is as shown in the @ expression.

1jVax=Kp*1←1, (I-8), (
xdtx%)-(0 Therefore, the command signal IVo to the servo amplifier section 2 is expressed by equation (7) using the force command signal !1'Vaf, the position command signal IVax, and the velocity feedback amount Δvf.

lVo = 1Vcx + 1Vai -IVi
``''(7) Now, a comparison will be made between the conventional example and the embodiment of the present invention. As shown in the conventional example, with only closed-loop force control, it was not possible to increase the gain of the force control loop in order to widen the stable region of the control system.

In the conventional example, the loop gain K to obtain a wide stable region
Assuming that f has been determined, the error between the command force 8-Fd1'' and the generated force 9'*Fql'' and the command force 5-Fch
” is set as α.

Next, by open-loop force control, the error between the generated force S -Fg2'' and the command force S -Fd2'' and the command force S
-The ratio to Fd2 is defined as β.

Using the above, command force in the implementation sequence of the present invention! 3-Fd
The ratio r between the error between 3" and the generated force E3-Fgs" and the command force S-Fd3" is (1, (using the c4 formula, (10
) is as follows.

・・・・・・・・・・・・・・・・・・・・・・・・(
1o) Here, if 4=0.5 and β=0.9, T is 0
．． 95, which results in less error with respect to the command force, and in terms of stability, since the gain of the closed loop of the control system is low, the robot control device has a wide stable region and has a practical force control function.

As described above, according to this embodiment, in order to control the force of the robot, open-loop commands and closed-loop commands are added,
By providing a control system that converts the output value into the joint coordinate system and uses that signal as the speed command signal for the servo amplifier section, the stable region of the force control loop can be widened, and it can be adjusted to changes in the stiffness of the environment. Therefore, it is possible to construct a practical robot control device that is not influenced by the robot's influence and also has excellent control performance.

In the embodiment, a directed drive system in which a reduction gear is not used between the arm and the motor has been described, but the present invention can also be applied to a robot having a reduction gear.

Further, in the embodiments, the force signal has been described as a force return signal, but the present invention can also be applied to a moment signal or both force and moment signals.

Effects of the Invention As described above, the present invention includes a first detection means for detecting a force applied to the tip of a robot arm, a command force signal serving as a predetermined force command, and a first detection means. a first force signal that calculates the difference between the detected force and the first force signal;
a second calculation means for amplifying the output of the first calculation means; and a calculation means for calculating the sum of a command 1 signal serving as a command for a predetermined force and the output of the second calculation means. comprising a third calculation means and a fourth calculation means for converting a force error command signal output from the third calculation means into a joint coordinate system of the robot arm;
By providing a control system that uses the output of the fourth calculation means as a speed command to the servo amplifier section that drives the motors attached to each joint of the robot arm, the conventional robot control device with a force control function has the ability to The object of the present invention is to provide a robot control device having a practical force control function that can solve the drawback of not having a wide stable region, and can also provide excellent performance in terms of accuracy and controllability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a hybrid position/force control type robot control device according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional robot control device having a conventional force control function, and FIG. FIG. 4 is a block diagram of a force control function section of a conventional robot control device, and is a diagram showing the relationship between stability and various constants in a force control system. 2... Servo amplifier section, 3... Motor, 4... Robot arm, 12... Force sensor, 18... Force error Conversion matrix for command signal from node coordinate system to joint coordinate system, 20...
Gain, 27... Adder, 28... Decelerator.

Claims (1)

[Claims] a first detection means that detects a force applied to the tip of the robot arm; a command force signal that is a predetermined force command; and a first detection means that is a force detected by the first detection means;
a first calculation means for calculating a difference between the force signal and the first calculation means;
a second calculation means for amplifying the output of the calculation means; and a third calculation means for calculating the sum of the command force signal serving as the predetermined force command and the output of the second calculation means; and fourth calculation means for converting a force error command signal output from the third calculation means into a joint coordinate system of the robot arm, and converting the output of the fourth calculation means to each joint of the robot arm. 1. A robot control device comprising: a control system that issues a speed command to a servo amplifier unit that drives a motor attached to the robot controller.