KR930004186B1 - Four shaft simultaneous potential control device by servo method - Google Patents

Abstract

The apparatus simultaneously controls four axes of the system using DC servo motor by using software servo replacing hardwave position loop to reduce the quantity of hardware and expand the flexibility of the system. It includes four encoders (EN) for detecting the current position of a servo motor (M), a microprocessor (CPU) for generating speed control command calculated from the position difference of the motor (M), a frequency/voltage converter (F/V) for converting the output pulse of the encoder (EN) to DC voltage corresponding to the speed of the motor (M), and a D/A converter (D/A) for converting the speed control command to voltage control command.

Description

4-axis simultaneous position controller using software servo method

1 is a schematic block diagram of a conventional hardware servo device.

2 is another schematic block diagram of a conventional hardware servo device.

3 is a block diagram showing a software processing unit of the present invention.

4 is a block diagram showing the hardware of this invention.

5 is a block diagram showing software position control of the present invention.

6 is a detailed view of part (3) of FIG.

7 is a detail of part (2) of FIG.

FIG. 8 is a detail of part (4) of FIG.

9 is a flowchart of an algorithm for processing the count of this invention by software.

The present invention relates to a four-axis simultaneous position control device using a software servo method. In particular, a DC servo controller used in robot controllers, numerically controlled machine tools, etc., that is, a four-axis simultaneous position control device for all systems using a DC motor. It is about.

In the conventional hardware servo system, it is generally composed of an operating part, a current feedback part, a speed feedback part, and a position feedback part. An encoder or a deviation counter is used as a position detector, and when the deviation counter is used, The clock can be used as it is. Therefore, the amount of position command must be transmitted in the form of a clock. In addition, when using the encoder as an analog value passed through the FVC (frequency-to-voltage converter) using the encoder, the speed feedback unit could be configured without using a tacho generator (TG). However, the hardware servo system has a circuit for generating a clock and a hardware position loop, which causes an increase in hardware. In addition, there is a problem that it is difficult to compensate for the difference between the number of clocks and the absolute position. Since the number of outputs generally corresponds to the position and the frequency of the command clock corresponds to the speed, the speed loop also depends on the encoder value, so the speed loop also varies in position and characteristics depending on the operation of the current loop. This lack of intelligence makes it difficult to make up for these drawbacks.

In order to overcome this conventional disadvantage, the present invention reduces the amount of hardware by replacing the hardware position loop with a software position loop, and the error counter of the deviation counter due to the failure of the feedback clock to follow the input of the command clock. The software has the advantage that it can be processed flexibly depending on the situation by developing the software algorithm so that the CPU can judge and process the location by controlling the location of the flow in the software way.

The object of the present invention is to replace the hardware position loop with software by adopting the software servo method, so the amount of hardware is reduced, and because the software is flexible, it is used in robot controllers and numerical control machine tools that can overcome hardware problems. It is to provide a 4-axis simultaneous position control system for a system using a DC servo motor.

In order to achieve the above object, the present invention provides a four-axis simultaneous position control apparatus using a software servo method of a servo motor, wherein four encoders are provided, one on four axes, for detecting a current position of the servo motor. (EN), a four multiplication circuit section for performing four multiplications for four frequency multiplications by receiving the outputs of the respective encoders, two programmable interval timers for each axis for counting the four multiplied encoder pulses, A frequency multiplication and counting means comprising a counter for generating an interrupt required to operate the timer as a counter, a target position, a speed for each of the four axes based on the acceleration / deceleration pattern, and a speed value for each axis. Obtain the position deviation from the absolute position value of the motor inputted from the counting means, and issue the speed command giving the position gain to this value. A microprocessor (CPU), a digital / analog converter (D / A) for converting a speed command output from the microprocessor into a voltage control command, and an encoder multiplied by four times from the frequency multiplication and counting means. A frequency / voltage converter (F / V) for converting an output pulse to a DC voltage corresponding to a motor speed value, and a driver for driving the motor according to the outputs from the D / A and F / V. The programmable interval timer consists of three RAMs, each of which is allocated to a plurality of regions having a total count value (TCNT), a most recently read value (LCNT), and a newly read value (NCNT). It provides a four-axis simultaneous position control device using a software servo method, characterized in that the counting pulse from the.

Hereinafter, the apparatus of the present invention will be described in detail according to the accompanying drawings.

1 and 2 are block diagrams of a conventional hardware servo device, in which a microprocessor (CPU), a PWM controller, and an operation unit connected with a DC motor are generally used to control a DC servo motor. A loop for feedback control of each position, speed, and current is formed, and an encoder (EN) or a deviation counter is used as the position sensor. 2 is a block diagram of a servo device when a deviation counter is used as a position sensor. In this case, the speed feedback uses the encoder value passed through the FVC by using the encoder (EN) without using the speed TG. I could construct a loop.

3 is a block diagram of the present invention that transmits a command such as position, speed, voltage, and pulse from a microprocessor (CPU). The software servo application level is limited to position control only. It is supposed to be.

4 is a hardware block diagram of the present invention, wherein reference numeral (1) of the figure is a servo hardware part.

5 is a software block diagram for processing the position control during the hardware servo control of the present invention by software.

Calculate the target position from the CPU, calculate the pulse for each of 4 axes according to the acceleration / deceleration pattern, calculate the position deviation from these values and the absolute position value of the motor from the counter, and give the appropriate gain to the motor. The voltage command corresponding to the speed of is sent out through D / A (2), and the current position value calculated through the counter is fed back to the next position command.

The implementation of the actual circuit corresponding to the digital / analog converter (D / A) 2 of FIG. 4 is shown in FIG. 7, and the frequency / voltage converter (F / V) 3 is shown in FIG. (4) is shown in FIG.

6, 7 and 8 illustrate the minimum hardware required for the software servo scheme that this invention is intended to implement.

6 is an F / V circuit, in which the encoder pulses generated through the multiplying circuit of frequency (4) in which (2) of FIG. 8 (A) is implemented as PAL are different in phases A and B as aa and bb in (1) of FIG. Is entered. The analog software of (1) enters the input of (2) by switching the A phase to 0- + 15V and the B phase to 0--15V, and is integrated first through the RC circuit of (3) and The frequency is converted to a DC voltage by performing second integration by an operational amplifier. According to the F / V input voltage request of the driver, the variable resistor of (4) is adjusted to adjust the F / V output voltage.

FIG. 7 is a circuit corresponding to the D / A (2) of FIG. 4 and converts the position command calculated by the CPU into the speed command of the motor, and makes this value a voltage control command. In FIG. 7, (1) converts the digital value into a voltage, and the voltage inverted through the operational amplifier of (2) is replaced by the sample and hold of (3) and input to the driver. do.

6 and 7 are general control circuits and FIG. 8 is a circuit for controlling software position by substituting a counter instead of a position control board in this invention.

(2) of FIG. 8 (a) shows that the pulses inputted from the four motor encoders in (1) can be prevented through a photo coupler, and the frequency can be multiplied by 4 times and direction discriminated. The logic program is entered. (3), (4), (5) is a programmable interval timer that counts four multiplied encoder pulses together with software, and a total of eight, two for each axis. Since these counters are all 16-bit decrement counters, they are calculated by software using a special algorithm shown in FIG. (6) is a counter for generating an interrupt required for software position control, for a software position loop and for making a sampling.

The present invention is in hardware the same as shown in Figs. 6, 7, and 8, and only allows the position loop to be processed by software.

As shown in FIG. 8 (a), eight timers are composed of three RAMs (3, 4, and 5), and each RAM includes a plurality of memory areas necessary for processing counting by software as shown in FIG. 8 (b). Divided into In FIG. 8 (b), the maximum count is $ 0000 and the minimum is $ 0001. In Fig. 8 (b), TCNT is the total count value, LCNT is the most recently read value, and NCNT is the newly read value.

In FIG. 8, two counters, CW (clockwise) and CCW (counterclockwise), are assigned to the RAM.

The counting method using the above-described RAM will be described with reference to FIG. The CNT1 is read in ninth (1). In (9) of FIG. 9, the previous count value LCNT1 is compared with the current read value NCNT, and when the newly read value NCNT is large (3), the difference is calculated as the complement of these differences. Add to counter value TCNT1. If it is large, add to the total counter value TCNT1 for the difference in (5) and (6). If it is the same, the pulse does not come in, so go to the next step. When (4) and (6) is completed, the newly read value (NCNT) is stored in RAM. This allows you to store the most recently read value for the next counting as a criterion.

After step (8), steps (1) to (7) are performed in the same manner, and in step 10, steps (1) to (9) are repeated for two, three, and four axes. This algorithm calculates the number of clocks for CW and CCW for each axis, so the absolute position of the current motor can be found by subtracting the total count value TCNT2 of CCW from TCNT1, the total count value of CW, when rotating the position loop. Therefore, the deviation of the target position can be compensated in software by the position command calculated by the CPU and the number of pulses calculated by feedback.

As described above, due to the presence of the command clock generation circuit, which is a problem of the hardware servo system, and the hardware position loop, the amount of hardware increases and the position characteristic varies depending on the performance of the speed loop and the current loop. Although the performance of the software servo method of the present invention replaces the hardware position loop with software, the amount of hardware is reduced, and the hardware is not intelligent, while the software is fluid, so it can overcome the hardware problem. There is. Therefore, the development of only the software algorithm has the advantage that can be processed quite flexibly depending on the situation.

Claims (2)

A four-axis simultaneous position control apparatus using a software servo method of a servo motor, comprising four encoders (EN) installed on each of four axes to detect a current position of the servo motor, and the respective encoders. Four multiplier circuit section that receives four outputs and performs four times the frequency, two programmable interval timers for each axis to count the four multiplied encoder pulses, and a counter for generating an interrupt required to operate the timer as a counter. Compute the frequency multiplication and counting means, the target position and the speed for each of the four axes by the acceleration and deceleration pattern, and then the position from the speed value for each axis and the absolute position value of the motor input from the counting means A microprocessor (CPU) for calculating a deviation and outputting a speed command giving a position gain to this value, and the microprocessor A digital / analog converting unit (D / A) for converting the speed command outputted from the control unit into a voltage control command, and an encoder output pulse multiplied by four times from the frequency multiplication and counting means to a DC voltage corresponding to the motor speed value. A frequency / voltage conversion unit (F / V) for conversion and a driver for driving the motor according to the outputs from the D / A and F / V, and the programmable interval timer is composed of three RAMs. Each RAM is assigned a plurality of regions having a total count value (TCNT), a most recently read value (LCNT), and a newly read value (NCNT) to count pulses from the encoder. 4-axis simultaneous position controller using software servo method. The device of claim 1, wherein said counting means constitutes a position loop.

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