JPH04281384A - Servo motor controller - Google Patents

Abstract

PURPOSE:To accelerate by performing an A/D conversion of a current value and a parallel process of a software so as to effectively operate a time required for the A/D conversion of the current value in a servo motor controller. CONSTITUTION:A PWM circuit 3 which outputs a triangular wave sync signal (a) to be output at a predetermined timing of a triangular wave signal, an A/D converter 4 with sample holding for sample holding current values of phases of a servo motor with the signal (a) as a trigger, sequentially ADD-converting them to latch data and generating an A/D conversion complete signal (b) when the conversion is completed, and a CPU 1 which inputs the signal (b) at an INT terminal and operates with a software with start signals of a current control loop and a speed control loop, are provided. The A/D conversion of a current value and the software can be processed in parallel.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device used in high-precision NC devices and robots.

0002

2. Description of the Related Art The structure of a conventional servo motor control device is shown in FIGS. 3, 4, 5 and 6, and its operation will be explained.

In FIG. 3, 1 is a CP that can perform high-speed calculations.
U is a digital signal processor (hereinafter abbreviated as DSP), 2 is a pulse counter that counts the pulse signal of the encoder, 3 is a PWM circuit, 4 is an A/D converter with sample and hold (hereinafter abbreviated as S/H), 5 6 is a driver circuit, 6 is a servo motor, and 7 is an encoder directly connected to the servo motor 6.

FIG. 4 shows a specific example of the PWM circuit 3, where 8 is a triangular wave generating circuit, 9 is a digital comparator, a is a triangular wave synchronizing signal synchronized with the peak of the triangular wave signal d which is the output of the triangular wave generating circuit 8, and c is a PWM circuit. is the output signal. Returning to FIG. 3, Iu is the U-phase current detection value of the servo motor 6, and I
v is the V-phase current detection value of the servo motor 6. DSP
1, the triangular wave synchronizing signal a is connected to the INT terminal, the current loop for calculating current control is processed using the triangular wave synchronizing signal a as a trigger, and the speed loop for calculating speed control is divided and processed. In the speed loop, a current command signal is calculated from the speed command from the host CPU and the speed feedback signal calculated by the pulse counter 2. In the current loop, a PWM command signal is calculated from the current command signal and current values Iu and Iv read from the A/D converter 4 with S/H. The PWM circuit 3 converts this PWM command signal into a PWM pulse signal c. In driver circuit 5, this PW
A PWM voltage is applied to the servo motor 6 using the M pulse signal c as input. Further, the A/D converter 4 with S/H samples and holds the current value of each phase of the servo motor 6 to detect it, and latches the sequentially A/D converted data.

[0005] The operation of the servo motor control device configured as described above will be explained below with reference to FIGS. 5 and 6. As shown in FIG. 5, the PWM circuit 3 outputs a triangular wave synchronization signal a synchronized with the peak of the triangular wave signal d. When this triangular wave synchronization signal a is input to the INT terminal of the DSP1, the DSP1 starts current loop processing. In this current loop processing, first output the S/H signal and
/H A/D converter 4 is instructed to perform S/H and A/D conversion. Next, after the A/D conversion is completed after T1 time has elapsed, the current feedback values of each phase are read, subsequent calculations are continued, and a PWM command signal is output to control the servo motor 6.

[0006]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, it is difficult to divide and process other loops during T1 during current loop processing after outputting the S/H signal and detecting the current. Unless some measures are taken to make the DSP work effectively, the disadvantage is that the calculation time will be long. One way to solve this problem is to use a high-speed A/D converter with S/H, but this method has the drawback of increasing costs.

The present invention has been made to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a servo motor control device that can continue calculations effectively even during the current conversion time T1 with a simple circuit configuration.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the servo motor control device of the present invention provides
A PWM circuit that compares a WM command signal and a triangular wave signal and outputs a triangular wave synchronization signal at a fixed timing of the PWM pulse signal and the triangular wave signal, and a driver circuit that drives a servo motor using the PWM pulse signal as input; A sample/hold A/D converter that samples and holds the current value of each phase of the servo motor using the triangular wave synchronization signal as a trigger, latches each successive A/D converted data, and generates an A/D conversion completion signal when the conversion is completed. It consists of a D converter and the CPU that operates with software that uses the A/D conversion completion signal as an input to the INT terminal as a start signal for the current control loop and speed control loop, and performs A/D conversion of the current value and the software. This allows for parallel processing.

[0009]

[Operation] According to the above configuration, the current value of the servo motor can be sampled by hardware at the optimal timing of the triangular wave signal, and the A/D conversion completion signal can be used as the start signal of the current control loop and speed control loop. By using it, software can be processed without being restricted by A/D conversion time.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a is a triangular wave synchronization signal, and b is an A/D conversion completion signal. 4 uses the triangular wave synchronization signal a of the PWM circuit 3 as a sample-hold trigger input, samples and holds the current values Iu and Iv of each phase of the servo motor 6, sequentially A/D converts and latches, and A/D converts. A/D with S/H outputs A/D conversion completion signal when completed.
The converter 1 inputs the A/D conversion completion signal b.
This is the DSP connected to the terminal. The other symbols are those of the conventional example.

The operation of the servo motor control circuit configured as described above will be explained below using the operating waveforms shown in FIG.

First, the PWM circuit 3 generates a triangular wave synchronizing signal a synchronized with the peak value of the triangular wave signal. Next, the triangular wave synchronous signal a is input to the A/D converter 4 with S/H, the current value of each phase of the servo motor 6 is sampled and held, and the A/D converter 4 with S/H is sampled and held.
D conversion is performed and each is latched, and when the conversion is completed, an A/D conversion completion signal b is output. Also, in DSP1, A/D
The conversion completion signal b is input to the INT terminal, and when an interrupt occurs, the calculations of the current control loop and speed control loop are started. In addition, the A/D converter 4 with S/H is connected to the A/D converter 4 via the DSP bus at any timing in the current control loop.
Read the current values Iu and Iv from . With this configuration, the timing of the triangular wave signal and the detected current value can be made constant, and moreover, the processing of the current control loop and the A/D conversion of the current value can be processed in parallel.

[0014]

Effects of the Invention As is clear from the above description, according to the present invention, software processing and current value A/
D conversion can be processed in parallel, simplifying and speeding up the software.

[Brief explanation of the drawing]

[Fig. 1] Circuit diagram of a servo motor control device in an embodiment of the present invention.

[Figure 2] Operation timing diagram of the servo motor control device

[
Figure 3: Circuit diagram of conventional servo motor control device

[Figure 4] Block diagram of the PWM circuit of the servo motor control device

[Figure 5] Operation timing diagram of the servo motor control device

[
Figure 6: Flow diagram of the current loop of the servo motor control device

[Explanation of symbols]

1 Digital signal processor (CPU) 3P
WM circuit 4 A/D converter with sample hold 5 Driver circuit 6 Servo motor

Claims (1)

[Claims] [Claim 1] A servo motor control device that controls a servo motor by controlling speed and current;
PWM command signal and triangular wave signal are compared.
a PWM circuit that outputs a triangular wave synchronization signal that is output at a constant timing of the pulse signal and the triangular wave signal;
A driver circuit that drives the servo motor by inputting the M pulse signal, samples and holds the current value of each phase of the servo motor using the triangular wave synchronization signal as a trigger, and sequentially A
A with sample hold that latches each D-converted data and generates an A/D conversion completion signal when the conversion is completed.
A/D converter, and a CPU operated by software that uses the A/D conversion completion signal as an input to the INT terminal as a start signal for the current control loop and speed control loop, and performs A/D conversion of the current value and the software. A servo motor control device characterized by being capable of parallel processing.