JPS5829529B2 - Constant velocity control device for multi-axis moving objects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for numerically controlling the simultaneous movement of a moving object in multiple axes, and more particularly to an apparatus for controlling the moving speed of the object to a predetermined set value.

When moving a moving object such as a processing head or a workpiece in an industrial robot using an FTP (POINT TOPOINT) method, the trajectory and linear velocity during the movement are not controlled.

In addition, in NC machines that numerically control the simultaneous movement of a moving object in multiple axes, a pulse distribution method such as the MIT method, DDA method, or algebraic calculation method is used to linearly approximate the movement trajectory between two points. However, in any of these methods, the speed of movement varies greatly depending on the direction of movement.

(As is well known to those skilled in the art, in the MIT and DDA methods, the speed is 1 to v''2 times in two dimensions, and 1 to 1 times in three dimensions.
In the algebraic calculation method, the speed is 1 to 1/V/'2 times in two dimensions, and 1 to 1/v in three dimensions.
' varies between 3 times.

) Therefore, for example, when machining an object with a three-dimensional shape, if the tool is a machine tool that performs cutting, etc., such changes in speed will not only cause problems such as shortened tool life and roughness on the cutting surface. However, if the NC machine is a welding machine that performs arc welding, it is necessary to keep the welding speed spatially constant in order to keep the energy supplied by the arc constant, and as mentioned above, it is necessary to keep the welding speed constant spatially. There is a problem in that it is difficult to maintain constant welding quality when the speed changes by a factor of 70.

Conventionally, in order to keep the moving speed of a moving object such as a processing head or a workpiece constant in an NC machine, a binary rate multiplier (BRM), as proposed by Penn Ickes, has been used.
) to create a combined speed pulse train proportional to the speed number, add this pulse train to another BRM, and set this BRM so that it is controlled by the register for each axis direction (the value of the direction cosine of each direction). and numerically control the movement of the moving object in each axis direction using its output pulses.
Alternatively, since the feed rate is obtained by squaring the distributed pulse rate of each axis and taking the square root, a circuit that performs such calculations can be installed after the pulse distributor, and its output can be set. A method has been proposed in which the rate of clock pulses is adjusted to match the feed rate.

However, such a method requires vector calculations and calculations to obtain the direction cosine for each point along the travel route, and therefore requires a high-speed computer, and its practical use has not been promoted from an economical point of view.

The present invention solves the above-mentioned problems in a device for numerically controlling the simultaneous movement of a moving object in multiple axes, and provides a device that can perform constant speed control of a moving object with a simple and inexpensive configuration. It is intended to.

According to the present invention, in an apparatus for numerically controlling the simultaneous movement of a moving object in multiple axes, the positional increment digital value for each axis between two positions of the moving object is converted into an analog value. a D-A converter, a differential amplifier having a substantially infinite gain, a multiplier for multiplying the output of the differential amplifier and the output of each of the D-A converters, and each of the multipliers. and an arithmetic unit that calculates a vector sum of outputs, the set speed of the moving object and the output of the vector sum arithmetic unit are input to the differential amplifier, and the output of each multiplier is used to calculate each axis of the moving object. The directional drive is closely related by a device configured to control the directional drive.

FIG. 1 of the accompanying drawings is a schematic diagram showing the configuration of a constant velocity control device for a multi-axis moving object according to the present invention.

In the figure, 1a, 1b, and lc are the positional increments in the X-axis, Y-axis, and Z-axis directions between a certain point Pn and the next Pn+1 in the three-dimensional space in which the moving object moves, respectively. Digital Valuer JX1±JY,±l? This is a DA converter that converts into IZ and analog values.

Analog outputs of these D-A converters ±EX, ±EY,
±EZ are input to multipliers 2a, 2b, and 2c, respectively.

The output (1) of the differential amplifier 3 is simultaneously input to these multipliers, and each multiplier calculates and outputs.

The outputs of these multipliers are input to the vector sum calculator 4,
Here, the vector sum is calculated.

The two-differential amplifier 3 receives the output (8) of the composite speed setting potentiometer 5 for setting the required composite speed of the moving object, and at the same time inputs the vector sum (2).

is entered. The differential amplifier 3 is assumed to have a substantially infinite gain.

FIG. 1 (The operation of the device shown in FIG. 1 is explained below using a formula.

If the gain of differential amplifier 3 is G, It is.

However, since G is substantially infinite, and the following are the cosines of the directions opposite to the X, Y, and Z axes t in the moving direction of the moving object, ■X, ■7. 2 represents the velocity component in each axis direction for obtaining the set speed s.

Therefore, if the outputs from the multipliers 2a, 2b, and 2c actuate an appropriate actuating mechanism and simultaneously drive the moving object in each axis direction, the moving object will be driven in a predetermined three-dimensional direction at the combined speed 8. It will be done.

FIG. 2 is a diagram showing an example of an operating mechanism for driving a pulse motor using a speed component signal of X (or V, V7.).

In the figure, 6 is a V-F converter, which generates a frequency output proportional to Vx.

This frequency is applied to the pulse motor drive unit 7), which drives the pulse motor 8.

A polarity signal obtained by determining the polarity of Vx by a polarity circuit 9 is simultaneously input to the pulse motor drive unit 7, and the driving direction of the pulse motor is switched in accordance with the polarity.

FIG. 3 is a diagram showing a servo mechanism in which the speed component signal (XI) passes through the speed control circuit and drives the τ servo motor at a speed proportional to (2).

In any case, when constant speed control is performed continuously, when a certain point (Bn) is reached, that point and the next point (Bn
+1), calculate the speed, specify the speed for each axis, and (
A matching circuit is added to determine whether or not the next point (target position) has been reached during operation, that is, a circuit that compares the target position and the current position and outputs an output signal when they match. It is preferable to use this method, which allows constant speed linear motion to be performed continuously in any direction without accumulating errors due to analog calculation errors.

In configuration 1 as shown in Figure 1, if the differences AX, lY, lZ in the coordinate values of each axis between two points of the moving object are directly input to the D-A converter, these values are too small. This increases the error caused by analog calculation.

FIG. 4 is a diagram illustrating a shift circuit for dealing with such a case.

In this case, JX. The values of lY and lZ are transferred to a D-A converter and a shift register 12 of the number of bits (excluding the sign bit).
a.

12b and 12c, and simultaneously shift these values (digital values) one digit at a time toward the largest digit until 1 is in the largest digit for at least one of (X, lY#Z). , the value when the maximum digit is 1 is input to the DA converters 1a, 1b, and 1c.

In this way, analog calculation errors can be reduced by appropriately shifting the values of (X, JY, and JZ).

Thus, it is understood that according to the present invention, the moving speed of a moving object can be controlled to a predetermined constant speed when the simultaneous movement of a moving object in multiple axes directions is numerically controlled by a control circuit device having a simple configuration. It will be.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of a constant speed control device for a multi-axis moving object according to the present invention, and FIG. 2 is a diagram showing an example of a drive configuration connected to the device shown in FIG. 1 to drive a pulse motor. Fig. 3 is a diagram showing a configuration connected to the device shown in Fig. 1 to drive a servo motor, and Fig. 4 is a diagram showing a configuration in which the device shown in Fig. 1 is connected to drive a servo motor.
FIG. 3 is a diagram showing a configuration added to the device shown in the figure. 1 a, 1 b, 1 c・”-D-A converter,
2a. 2b, 2c... Multiplier, 3... Differential amplifier, 4... Vector sum operator, 5...
・Potentiometer for setting the composite speed, 6...V
-F converter, 7... Pulse motor drive unit, 8... Pulse motor, 9... Polarity circuit, 10... Speed control circuit, 11...・・・・・・
Servo motor, 12a, 12b, 12cm shift register.

Claims (1)

[Claims] 1. In a device for numerically controlling the simultaneous movement of a moving object in multiple axes, a D-A converter that converts a position increment idicle value for each axis between two positions of the moving object into an analog value; a differential amplifier having an infinitely large gain; a multiplier that multiplies the output of the differential amplifier by the output of each of the DA converters; and an operation that calculates a vector sum of the outputs of each of the multipliers. The set speed of the moving object and the output of the vector sum calculator are input to the differential amplifier, and the drive of the moving object in each axis direction is controlled by the output t of each multiplier. A device comprising: