JPH01303508A - Digital servo system - Google Patents

Abstract

PURPOSE:To observe even the high-speed fluctuation of the control state with high accuracy by using a measuring memory which stores the time series data on the digital state value showing the control state of a digital servo system. CONSTITUTION:A measuring memory MMEM110 is connected to a microcomputer 104 via a bus. The MMEM110 serves as a RAM which holds the time series data on the digital state value showing the control state of a digital servo system. Thus it is possible to hold the high-speed change of the state value of a control subject in the MMEM110 by storing at a high speed said time series data into the MMEM110 under the control of the microcomputer of the servo system. Then the contents of the MMEM110 ate read out as necessary. As a result, the high-speed change of the state value stored in the MMEM110 can be observed despite a high reading speed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a digital servo system that is used in a numerical control device or a robot controller and controls a controlled object such as a motor by software, and particularly relates to a digital servo system that is used in a numerical control device or a robot controller and controls a controlled object such as a motor by software. This paper relates to a digital servo system that makes it possible to observe significant state quantities.

[Background Art] In recent years, with the development of high-speed and high-precision microcomputers, digital servo systems that control objects to be controlled by software using microcomputers have been commercialized.

A digital servo system, for example, controls the rotational position and speed of a motor, and the current flowing through the motor in real time using software. can be performed extremely quickly. In fact, when controlling the motor current, good performance cannot be obtained unless numerical calculation processing is performed at a cycle of several hundred microseconds.

FIG. 3 is a block diagram when a conventional digital servo system is applied to a system such as a numerical control device.

In FIG. 3, 100 is a conventional digital servo system, and 200 is a microcomputer at the center of a system such as a numerical control device that uses this digital servo system 100.

First, a conventional digital servo system 100 will be explained. 101 is a motor (M) as a controlled object;
102 is an inverter (I) that supplies power to the motor 101.
NV), 103 is an encoder (EC) directly connected to the motor 101. Further, 104 is a microcomputer that executes digital servo software, a position detection unit (PD) 105, an A/D converter (A/D
) 106, PWM control controller (PWMC) 107
, a data memory (DMEM) 108 , and a program memory (PMEM) 109 .

The position detection unit 105 counts the output pulses of the encoder 103 and detects the rotational position of the motor 101. The microcomputer 104 includes the position detection unit 10
5, the rotational position of the motor 101 is input, and the rotational speed is calculated by calculating the amount of change in the rotational position per unit time. The AD converter 106 converts the current flowing through the motor 101 into a digital value and inputs it to the microcomputer 104. Microcomputer 1
04 inputs the rotational position, rotational speed, and current flowing through the motor as feedback data, calculates a control voltage command to be applied to the motor 101, and outputs it to the PWM controller 107. The calculation process is performed at high speed with a period of several hundred microseconds. The PWM controller 107 inputs the control voltage command calculated by the microcomputer 104 and outputs a switching signal according to the control voltage command to the inverter 102.

In this way, the motor 101 is controlled by applying a control voltage from the inverter 102. The data memory 108 is
The program memory 109, which is a RAM that stores parameters and momentary state quantities necessary for control, is a ROM in which a control algorithm for the microcomputer 104 is stored.

Next, the host microcomputer 200, such as a numerical control device to which a digital servo system is applied, will be explained. The host microcomputer 200 performs comprehensive data information processing regarding the entire numerical control device, and as a link thereof, the digital servo system 100
It gives motor rotational position commands to the microcomputer 104 and monitors whether there are any abnormalities in the control state of the motor. In addition, the microcomputer 200 processes data input from a keyboard of a numerical control device, etc., and displays the operating status on a CRT. Compared to the microcomputer 104 of the digital servo system 100, which processes limited data related to motor control at high speed in a cycle of several hundred microseconds, the host microcomputer 200 processes large-capacity data related to the entire numerical control device. It performs information processing of data, and the individual processing speed is usually not very high.

[Problems to be Solved by the Invention] In general, in order to obtain the best control performance in servo systems used in numerical control devices and robot controllers, evaluation and adjustment work is essential.

For this reason, it is necessary to be able to observe with high precision, for example, state variables that directly indicate the control state of the servo system, such as the amount of deviation between the motor rotational position command and the actual motor rotational position, as well as the motor rotational speed and current. .

However, in the conventional digital servo system described above, the state quantity indicating the control state of the servo system is stored in the data memory 108 as a digital value.
Unlike analog servo systems, it cannot be easily observed with a waveform observation device such as a synchroscope.

Therefore, as a first method, the microcomputer 104 sequentially outputs the digital state quantity of the data memory 108 each time it is updated, and this is converted into an analog value by a DA converter circuit, so that the control state of the servo system can be expressed as a waveform on a synchroscope, etc. It was observed with an observation device. However, it is extremely difficult to realize a DA converter circuit that converts a digital value of approximately 16 bits into an analog value at high speed with high precision, and even if it were realized, it would be expensive.

Next, as a second method, a method can be considered in which the state quantity of the digital value stored in the data memory 108 is treated as a digital value and displayed on a CRT. That is, the microcomputer 200 on the host samples the digital values in the data memory 108 and outputs them to a CRT such as a numerical control device. According to this method, the state can be observed in various forms by using the graphic processing software of the host microcomputer 200, and in addition, expensive waveform observation devices such as A conversion circuits and synchroscopes are not required. It has the effect of becoming However, as mentioned above, the data memory 108
The digital state quantity of is rewritten at high speed by the microcomputer 104 at a cycle of several hundred microseconds, whereas
The sampling process of the host microcomputer 200 can normally only be executed at a processing cycle of several tens to hundreds of milliseconds, which poses a problem in that high-speed changes in state quantities cannot be observed.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a digital servo system that can observe high-speed changes in state quantities without using a high-speed DA conversion circuit.

[Means for Solving the Problems] A digital servo system according to the present invention includes a measurement memory that sequentially stores time-series data of digital state quantities representing the control state of the digital servo system based on control of a microcomputer, A feature is that this measurement memory can be read out from the outside (for example, from a host microcomputer) as appropriate.

[Operation] According to the present invention, by storing time-series data of digital state quantities representing the control state of the servo system in the measurement memory at high speed under the control of the microcomputer of the servo system, high-speed control of the controlled object is performed. It is possible to hold the state quantity change in the measurement memory. By reading the contents of this measurement memory as necessary, even if the readout speed is slow, it is possible to observe high-speed state quantity changes held in the measurement memory.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment in which the digital servo system of the present invention is applied to a system such as a numerical control device.

In FIG. 1, 300 is a digital servo system according to an embodiment of the present invention, and 200 is an upper-level microcomputer of a system such as a numerical control device to which this digital servo system 300 is applied.

101 is a motor, 102 is an inverter that supplies power to the motor 101, and 103 is an encoder directly connected to the motor 101. A microcomputer 104 executes digital servo software, and the microcomputer 104 is connected to a position detection section 105, an AD converter 106, a PWM:2 controller 107, a data memory 108, and a program memory 109 via a bus. These operations are as described in the prior art.

This digital servo system 300 differs from the conventional digital servo system 100 in that a measurement memory (MMEM) 110 is newly provided and this is connected to the microcomputer 104 via a bus. This measurement memory 110 is an R
It is AM.

Each time the microcomputer 104 executes a digital servo program, it rewrites the digital state quantity stored in the data memory 108, but at the same time, it additionally stores the digital state quantity at a specific address in the measurement memory 110 and stores it as time series data. save.

FIG. 2 is a flowchart showing an example of a program for additionally storing the digital state quantity at a specific address of the data memory 108 in the measurement memory 110 and saving it as time series data. From there, the address on the data memory 108 of the digital B quantity to be measured and the timing for starting the measurement are input. When the microcomputer 104 receives this and starts measuring the specified state quantity (Sl), the measurement memory 1 is written every time the state quantity is written to the data memory 108.
While increasing the storage address of 10 by 1 (S5)
, reads the state quantity from the data memory 108 (S3), and writes it to the measurement memory 110 (S4). The microcomputer 104 stores this as the measurement memory 11.
Starting from address 0 and repeating to address 999 (S2), a total of 10007-words of time-series data is stored in the measurement memory 110.

This program is executed at high speed by the microcomputer 104 at a cycle of several hundred microseconds in parallel with the execution of the digital servo program.

Since this program is a simple program, it has almost no effect on the execution of the digital servo program, and if the execution cycle is 500 μs, the measurement memory capacity of 4k x 16 bits is sufficient. Yes, it is possible to measure for up to 2 seconds, and there is no problem in practical use.

RAMs of this capacity are available at low cost today.

When the microcomputer 104 finishes storing the digital state quantity of the i ooo word, the microcomputer 200 of the upper silkworm reads out the time series data stored in the measurement memory 110. At this time, the speed of the reading process is high. There is no need to be.

As a result, the host microcomputer 200 can capture the control state of the servo system up to high-speed fluctuations with a cycle of several hundred microseconds in a normal sampling cycle, and can display the control state of the servo system with high precision on a CRT such as a numerical control device. It is possible to output with .

Although the present invention has been described above using motor control as an example, the present invention is applicable not only to motors but also to all other controlled objects.

[Effects of the Invention] As explained above, the digital servo system according to the present invention is equipped with a measurement memory that stores time-series data of digital state quantities representing the control state of the digital servo system, and also allows the digital servo system to be numerically controlled. When applied to systems such as equipment and outputting the control status of a servo system to the CRT of a numerical control device for observation, it has the excellent effect of being able to observe extremely high-speed fluctuations in the control status with high precision. play.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the process of saving the state quantities of the digital servo system according to the present invention as time series data in the measurement memory, and FIG. It is a block diagram. 100, 300, digital servo system, 10
1; Motor, 102; Inverter, 103; Encoder, 104, Microcomputer, 105; Position detection unit, 106; AD converter, 107. PWM controller, 108; data memory, 109; program memory, 110; measurement memory, 200. upper microcomputer

Claims (1)

[Claims] (1) In a digital servo system in which a controlled object is controlled at high speed by software using a microcomputer, measurement that sequentially stores time-series data of digital state quantities representing the control state of the digital servo system based on the control of the microcomputer. 1. A digital servo system characterized by having a memory for measurement, the memory for measurement being readable from the outside as appropriate.