JPH01175611A - Controller with force control function - Google Patents

Abstract

PURPOSE:To attain the stable and precise chamfering of an NC processed material by controlling the absolute value of force which extends to a force sensor, for an increased quantity at the time of a force control mode so that it coincides with a force instruction value. CONSTITUTION:A switch 17 changes over a position control mode and the force control mode by an external control signal. In the case of the position control mode, a motor 2 is controlled so that the command value Xc of the position coincides with the feedback value Xf of the position. In the case of the force control mode, the motor 2 is controlled so that the output Ff of an operation part 19 coincides with the command value Fc of force, and a uniaxial module 1 is positioned and controlled. The operation part 19 of force calculates the absolute value of the force of a signal F from the force sensor 3 for the increased quantity from the position control mode. Thus, the absolute value for the increased quantity of force extending to the NC processor becomes constant event if an end mill presses the NC processed material in the direction different from that of an Z axis, and stable chamfering is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to force control, and in particular to a control device having a force control function for controlling the absolute value of an increase in force.

BACKGROUND OF THE INVENTION In recent years, a lot of research has been carried out on control devices having a force control function, along with the trend toward higher functionality of robots.

An example of a conventional control device having a force control function will be described below with reference to FIGS. 3 and 4.

In Fig. 3, 1 is a 1-axis module that operates in one direction, 2 is a motor that drives 1 @ module l, 3 is a force sensor that detects the force applied to the 1-axis module 1, and 4 is a signal from the force sensor 3. 5 is the motor 2
6 is a motor control unit that controls the speed of the motor 2; 7 is an external control signal generation unit; D
O is an external control signal generated from the external in signal generator 7;
8 is a position detector.

In FIG. 4, 9 is a current control unit that controls the torque of the motor 2, 10 Kb is a speed error amplification gain, 11 is a differentiator, 12 is a first subtractor, 13 is Ka a position error amplification gain, 14 is a second subtractor, 15 Kf is a compliance constant that converts the force error value ΔF into a position error value A switch 18 for switching the control mode is a calculation unit that extracts the Z-axis direction component of the force F detected by the force sensor 3. In addition, Fc is the force command value, Ff
is the feedback value of the returned force, Xc is the position command value, Xs is the position command value determined by the switch 17, Xf is the position feedback value, Vc is the speed command value, Vf is the speed feedback value, △V is the speed error value , Fz is the feedback value of the force in the Z-axis direction.

In FIG. 3, when the external III control signal Do, which is the output of the external control signal generator 7, is 0, the control system is in the position control mode, and when the external control signal Do is 1, the control system is in the force control mode. In the position control mode, the position command value Xc of the positioning control section 5 and the position feedback value X from the position detector 8
A calculation is performed from f and the command value of the calculation result is sent to the motor control unit 6.
send to

The motor control unit 6 moves the motor 2 so as to match the speed command from the positioning control unit 5, and positions the single-axis module 1 when the speed command matches the position command value Xc. Next, in the case of force control mode, a calculation is performed from the force command value Fc of the force control calculation unit 4 and the force feedback value Ff, and the position command value
s is sent to the positioning control section 5 as a position command value. The following is the same as in the position control mode, 1-axis module 1
moves until the force sensor 3 detects a force that matches the force command value Fc.

A detailed explanation will be given using FIG. 4.

In the position control mode, the position command value Xc is equal to the output Xs of the switch 17, and the second subtracter 14 calculates the difference between the position command value Xs and the position feedback value Xf and outputs it as a position error value ΔX. However, the position error value ΔX is multiplied by the position error amplification gain Ka by 13 to become the speed command value Vc. The first subtracter 12 takes the difference between the speed command value Vc and the speed feedback value Vf, calculates a speed error value ΔV, multiplies it by a speed error amplification gain Kb by 10, and sends it to the current controller 9 as a command. .

The current control unit 9 applies current to the motor 2 to drive the motor in accordance with the command.

The position detector 8 detects a position feedback value Xf. Further, the differentiator 11 differentiates the position feedback value Xf to generate a velocity feedback value Vf. As described above, in the positioning mode, the motor is positioned to match the position command value Xc.

Next, in the force control mode, the force command value Fc and the force feedback value Ff
is input to the third subtractor 16 and the difference is taken to obtain the force error value Δ
Calculate F and apply the compliance constant Kf to that value in 15.
Multiply by to create the position command value Xs. The following operations are the same as in position control mode. The calculation unit 18 calculates the force feedback value F.
Calculate the force Fz in the Z-axis direction. The first formula is the calculation method.

Fz=Fzn-Fzo (1) However, Fzn is the force in the Z-axis direction of the current force feedback value F, and Fzo is the force before the external control signal Do changes from 0 to 1, that is, in the position control mode. This is the force in the Z-axis direction of the feedback value F of the force at the time.

Therefore, in the force control mode, a force that matches the force command value Fc acts in the Z-axis direction of the force sensor 3 (like 1
Controls the axis module 1.

What is shown in FIG. 2 is an application example of a control device having a force control function, where 23 is a force control device. An end mill 22 is installed at the tip of the robot 21 to chamfer the NC workpiece 20.
is attached. The force control device 23 switches from the position control mode to the force control mode in response to the external control signal Do.
The uniaxial module 1 is controlled so that the force applied to the end mill 22 is constant.

Problems to be Solved by the Invention However, in the above configuration, when the force applied to the NC workpiece is kept constant, it is sufficient that the direction of the force F coincides with the Z-axis direction, but the direction of the force F applied to the NC workpiece is If the direction of force F is different from the Z-axis direction, the force in the Z-axis direction can be kept constant, but N
This method has the disadvantage that the force applied to the C-processed workpiece cannot be made constant, and it is not possible to chamfer the NC-processed workpiece stably and with high precision.

In view of the above problems, the present invention provides, in force control mode,
An object of the present invention is to provide a control device having a force control function that takes the absolute value of an increase in force as a force feedback value and controls the force applied to a force sensor. The functional control device includes a one-axis module that operates in one direction, a motor that drives the one-axis module, a force sensor that detects the force applied to the one-axis module, and a signal from the force sensor. A force control unit that includes a force control calculation unit that performs processing, a positioning control unit that performs positioning based on commands from the force control calculation unit, and a motor control unit that controls the motor based on commands from the positioning control unit. In the control device having this function, the force control calculation section switches between a position control mode and a force control mode based on an external signal, and when in the force control mode, the absolute value of the increase in the force applied to the force sensor matches the force command value. A control device having a force control function is characterized in that the control device is configured to perform control so as to cause the force to be controlled.

Effect: With the above-described configuration, the present invention switches between position control and force control based on an external signal, and during force control, controls so that the absolute value of the increase in force applied to the force sensor matches the force command value. By doing this, it is possible to control the force applied to the single-axis module in the Z-axis direction, which solves the drawback that conventional control devices with force control functions cannot consistently control forces in directions that do not match the Z-axis direction. be able to.

EXAMPLE Hereinafter, a control device having a force control function according to an example of the present invention will be described with reference to FIGS. 1 and 2. Note that the overall configuration is the same as the configuration diagram of a conventional control device (FIG. 3) having a force control function. This embodiment is different from the conventional one as shown in FIG. 1, as shown in FIG.
It is important to have the following.

The operation of this embodiment is almost the same as that of the conventional example, and is divided into a position control mode and a force control mode by an external control signal DO, and a switch 17 switches between the position control mode and force control mode. When the external control signal DO is O, it is the position control mode, and the position command value Xc
The motor is controlled so that the feedback value Xf of the position coincides with the positional feedback value Xf. When the external control signal Do is 1, it is the force control mode, and control is performed so that the output Ff of the calculation unit 19 matches the force command value Fc. The force calculation section 19 calculates the absolute value of the increase in force of the signal F from the force sensor 3 from the time of position control, as shown in the calculation of the second equation.

Ff =lFn-Fol (2) However, Fn
is the current value of the force feedback value, and FO is the external control signal Do
This is the feedback value of the force before it changes from 0 to 1, that is, in the position control mode. Therefore, the force calculation unit 1 is calculated as the force command value Fc.
The motor 2 is controlled so that the outputs Ff of the motors 9 and 9 coincide with each other. That is, when the force control mode is entered by the external control signal Do, the current force Fn is calculated from the force feedback value FO during the position control mode.
The motor 2 is controlled so that the increase in the absolute value of Fc matches the force command value Fc, and the one-axis module 1 is positioned.

Now, in the application example shown in FIG. 2, as explained in the conventional example, when the external control signal DO is 1, it is the force control mode, and the current force feedback value is calculated from the force feedback value Fo in the positioning mode. The increase in the absolute value of Fn is the force command value Fc
The motor is controlled to match the 1-axis module 1, and the 1-axis module 1 is moved. As a result, even if the end mill 22 pushes the NC workpiece 20 in a direction different from the Z-axis direction, the NC workpiece 2
The absolute value of the increase in force applied to zero becomes constant, allowing stable chamfering.

As described above, according to this embodiment, by providing a calculation unit that calculates the feedback value of force during the force control mode, it is possible to control the absolute value of the increase in force, which is different from the conventional control device. Stable and high-precision NC occurs when the direction of pressing the NC workpiece with an end mill is different from the Z-axis direction.
This can compensate for the drawback of not being able to chamfer the workpiece.

In this embodiment, an external control signal is used.

When Do is 0, it is the position control mode, and when it is 1, it is the force control mode, but when Do is O, it is the force control mode, and when Do is 1, it is the position control mode.

Effects of the Invention As described above, the present invention is capable of performing control so that the absolute value of the increase in force applied to the force sensor matches the force command value in the force control mode, and therefore has advantages that conventional control devices do not have. The pressing of the NC workpiece by the end mill is based on the direction and Z.
This method can compensate for the drawback that stable and highly accurate chamfering of NC workpieces cannot be performed when the axial directions are different, and the effect is significant.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of a specific application example, Fig. 3 is a block diagram of a conventional control device having a force control function, and Fig. 4 is a specific diagram of the control device. This is a typical configuration diagram. 1...1 axis module, 2...motor, 3...force sensor, 4...force control calculation section, 5...positioning Control unit, 6...Motor control unit, 17...Switcher, 19...
...Force absolute value calculation section.

Claims (1)

[Claims] a 1-axis module that operates in one direction; a motor that drives the 1-axis module; a force sensor that detects the force applied to the 1-axis module; and a force control calculation unit that processes signals from the force sensor. , a control device having a force control function, including a positioning control unit that performs positioning based on a command from the force control calculation unit, and a motor control unit that controls the motor based on a command from the positioning control unit, The force control calculation section switches between a position control mode and a force control mode in response to an external signal, and in the force control mode performs control so that the absolute value of the increase in the force applied to the force sensor matches the force command value. 1. A control device having a force control function, characterized in that the control device is configured to have a force control function.