JPS6097413A - Digital positioning servo system - Google Patents

Abstract

PURPOSE:To perform digital processing for both a position loop and a speed loop by processing a speed signal digitally by a program started synchronously with feedback pulses from an encoder. CONSTITUTION:The servo processing program is started synchronously with encoder pulses e and the number of encoder pulses e is read out of a counter 12 to calculate the output (= current counted value-last counted value) of a differentiator 14. Then, a speed feedback signal v (= f X constant Kv) is calculated, the output d (= speed command value c + last integrator output - f) of an integrator 16 is updated, and a buffer 17 is cleared. Then, a speed error epsilon (=d-V) is calculated and outputted to a digital/analog converter 4. The value off the speed feedback signal v is set to zero a specific time tau and the output d is outputted to the digital/analog converter 4.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a tachogeneless positioning servo system using a pulse encoder, and more specifically to a digital positioning servo system in which a velocity feedback signal is also generated by digital processing. .

[Prior art]

A block diagram of a conventional positioning servo system is shown in FIG. In Figure 1, (1) is a position command pulse, (2a)
, (2b) is a subtracter, (3) is a counter, (4) is a digital/analog converter (hereinafter referred to as DAC), (5) is an amplifier, (6) is a motor, and (7) is an encoder (hereinafter referred to as DAC). , ENC), (8) is the pulse/
This is an analog conversion circuit that converts the detected pulse frequency of the encoder (7) into an analog signal and generates a speed signal.

Since this conventional method converts the speed signal from a pulse signal to an analog signal, it has the following problems.

(1) The hardware was large. , (large number of circuit components).

(2) Loop drift is large and accuracy is poor.

(3) Poor reliability and maintainability, with large variations in characteristics.

(4) Position error signal is not analog, high resolution DA
C is required.

[Summary of the invention]

This invention was made to solve these problems.The speed signal is also generated by digital processing by a program started in synchronization with the feedback pulse from the encoder, and the digital processing is performed up to the speed loop. The purpose of this research is to introduce a digital positioning servo system.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Fig. 2 is a block diagram showing the concept of this invention, Fig. 3 is a block diagram showing an embodiment of this invention, Fig. 4 is a time chart for explaining the operation of one embodiment of this invention, and Fig. 5 is a block diagram showing the concept of this invention. 6 is a flowchart showing the first processing procedure of an embodiment of the invention, and FIG. 7 is a graph showing the relationship between the error signal and the DAC output. be.

In Figure 2, (3) is the counter, (4) is the DAC1
(5) is the amplifier C or below), (6) is the motor, (7) is the ENC, (9) is the speed feedback signal generator, α1 is the read-only memory (hereinafter referred to as ROM),
It has a conversion table that performs nonlinear compensation of gain.

In this invention, multi-signal processing is performed by a program using an arithmetic processing unit such as a microcomputer in the part to the left of the dashed line in FIG. It is characterized in that it generates a speed feedback signal.

A detailed explanation will be given below using FIGS. 3 to 7.

In FIGS. 3 to 7, (b) is a counter that counts ENC pulses, (b) is an interrupt control section, α◆ is a difference device,
(b) is a multiplier (constant: Kv), αQ is an integrator, and al is a buffer, which has the function of accumulating command data generated at a constant cycle. e is an encoder pulse, f is a differentiator output, C is a speed command, d is an integrator output, and V is a speed feedback signal.

Note that the side indicated by the arrow (C) is composed of hardware;
The 2) side shows the processing part using a glogram using a microcomputer.

Next, the operation will be explained using the flowcharts shown in FIGS. 5 and 6.

The servo processing program is started in synchronization with the encoder pulse a Ic. The number of encoder pulses e is read by the counter (2) (step 51).

The output f of the differentiator Q4 is calculated.

f = current current counter and previous counter value. At low speeds, f = 1, but when the speed exceeds a certain speed (when the processing capacity is exceeded, that is, after point A in Figure 4), f
=2.3. ...becomes... Even if the state of f=1 continues, the synchronization of the encoder pulse e changes, so the number of pulses apparently increases (decreases), and f is speed information (step 52). .

A speed feedback signal V is calculated.

υ=fXKv Kv is a constant, and the setting of this constant changes the response characteristics of the shield loop (step 53).

The output d of the integrator αQ is updated.

d=speed command value C 10th previous integrator output -fd represents the position error (step 54).

A processing report of the speed command value C is performed and the buffer al is cleared. Let tb, e=0. In this operation, a servo processing program is started in synchronization with the encoder pulse @lc, whereas commands are generated by a program that is started at regular intervals. tb, command data is created at regular time intervals. In this way, since servo processing and command data creation operate asynchronously, this is done to determine how much of the created command data has been processed by the servo processing program. This operation is particularly effective during transient times. That is, normally the cycle for generating command C is faster than the cycle for servo processing, but during transient times (especially at extremely low speeds) the cycle for generating command C may be faster. In this case, the servo processing side has a buffer a'! It is necessary to import all the command data accumulated in 5. On the command side, the servo processing side must clear the buffer.
This indicates that the command data has been processed (
Stemp 55).

Calculate the speed error.

ε=av (step 56).

Output e to DAC (4). Tsumari DA
The value of C(4) is updated (step 57).

After a certain period of time τ, the value of Kll is made zero. If this value is held until the next process, the value will not be proportional to the speed because the process is not performed within a certain period of time. Therefore, the software C (hereinafter abbreviated as S/W) makes the value of V zero after a certain period of time τ, as shown in FIG. (Software Onezocott). (Stella 7'58
).

d to DAC (4) (step 59).

With the above steps, the operation of the keyboard processing is completed.

Figure 6 is a flowchart showing the first operation.When the servo system is stopped, no matter how many commands are issued,
Since the ENC (7) is not rotating, there is no servo processing interrupt. Therefore, the number of commands increases and the motor (6)
If it does not try to turn in the - direction, seven inconveniences will occur.

For this reason, the first step is to create the directive,
) is checked to see if the command C is zero (step 61), and if C is not zero, the servo processing program is forcibly started. The flow shown in FIG. 6 shows the above operation. Once it starts operating, it operates according to the flow shown in FIG. 5 above.

Note that the interrupt control section α field interrupts every encoder pulse e at low speeds, and since the minimum interval of the servo processing cycle is regulated depending on the processing capacity, for example, A in FIG.
After this point, control is performed by referring to a counter and performing an operation of interrupting several pulses at once.

As described above, the error signal a (=d-v) is output as a signal obtained by feeding back the position signal and the speed signal, and can be digitally processed including the position loop and the speed loop.

The ROMQO shown in Figure 2 has an error signal (-) output and a DAC.
It has a conversion table (part of the S/W table) for obtaining the characteristics shown in FIG. 7 in relation to the output. In the conventional method, this was not possible because the bit width was large, and the insertion position was inappropriate at the command, but in the present invention, it is not possible to insert it at the error signal.
Since the bit width is small, the capacitance is small, making it possible to achieve non-linear output easily compared to the conventional amplifier (5), which has a circuit that generates non-linear output. It is. If there is no need for nonlinear output, the 8/W table may be omitted.

〔Effect of the invention〕

As described above, according to the present invention, the velocity feedback signal is also processed by 8/WK using an arithmetic processing device such as a microcomputer, and both the position loop and the velocity loop are digitally processed, so the digital signal has the following effects. A positioning servo system can be obtained.

(Re-loop drift is small and high accuracy.

(2) Good reliability and maintainability, and small variations in characteristics.

(3) Since the error signal is converted from digital to analog,
It is inexpensive because it does not require the highest resolution of the DAC.

(4) Since the speed feedback signal is generated in synchronization with the encoder pulse, the response is particularly good at low speeds.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the conventional positioning servo system, Figure 2
5 is a block diagram showing the concept of this invention, FIG. 5 is a block diagram showing one embodiment of this invention, FIG. 4 is a time chart for explaining the operation of one embodiment of this invention, and FIG. FIG. 6 is a flowchart showing the first processing procedure of an embodiment of the invention, and FIG. 7 is a graph showing the relationship between the error signal and the DAC output. In the figure, (1) is a position command, (2a) and (2b) are adders, (3) is a counter, (4) is a pAC, (5) is an amplifier, (6) is a motor, and (7) is ENC, (8)
is the pulse/analog conversion circuit, (9) is the speed generator, α
0 is ROM, (2) is counter, α field is interrupt control section, α
◆ is a difference device, (G) is a multiplier, and αQ is a basin device. Book,? , the same reference numerals in the drawings indicate the corresponding parts. Agent Masu Oiwa Figure 5 Figure 7

Claims (1)

[Claims] In a positioning servo system that uses a Hals encoder to perform control by generating a position feedback signal and a speed feedback signal based on feedback pulses from the encoder, a program that is activated in synchronization with feedback pulses from the encoder is used. A digital positioning servo system characterized in that a signal is generated that maintains a constant value for a certain period of time after the R return pulse is generated, and this signal is fed back as a speed signal.