SU1509826A1 - System for positional control of electric drive - Google Patents

Abstract

The invention relates to machine tools and robotics, and can be used, for example, in controlling electric robots of industrial robots or precision CNC machine tools, which work out monotonically varying metered positive (or negative) tasks for moving the working member. The aim of the invention is to increase the speed of the system by narrowing its area to working only on monotonically increasing or only monotonously decreasing negative positioning signals. The goal is achieved as follows. The reference signal is compared with the current value of the position of the motor shaft and the module of the received error signal is extracted. The resulting signal is converted to the PI controller and the resulting signal is compared with the current value of the rotation speed of the motor shaft. The result of the comparison is converted into a PI speed controller and enters the first information input of the switch, the remaining three inputs of which receive the output signals of the corresponding constant signal sources. The output signal of the switch through the first and second keys, the state of which is determined by the sign of the driver, is fed to the corresponding input of the current controller, in which it is compared with the motor current. The result of the comparison through the power amplifier affects the motor, changes the position and speed of rotation of its shaft. In addition, with the help of an arithmetic unit, five Schmitt triggers and two elements And, the system analyzes the values of the output signals of the setpoint sensor, the speed sensor, and the position and speed controllers. Depending on these values, one of the signals arriving at its four information inputs is sent to the switch input. 2 ill., 2 tab.

Description

The invention relates to machine tool building and robotics and can be used, for example, in controlling electric drives of industrial robots or precision CNC machine tools, which work out monotonically varying dosage tasks for moving the working member.

The aim of the invention is to increase the speed of the system by reducing its application to the development of only monotonically increasing positive or only monotone decreasing negative positioning signals.

Figure 1 shows the block diagram of the system; Fig. 2 shows a phase trajectory of a system with a proportional-integral speed regulator when a signal is triggered according to a triangular tachogram. I

Position control system

the electric drive contains the error meter 1, the first detector 2, the first amplifier 3, the first adder 4, the second amplifier 5, the switch 6, the first 7, the second 8 and the third 9 sources of constant signals, the first 10 and the second 11 keys, the current regulator 12, power amplifier 13, electric motor 14, current sensor 15, speed sensor 16, position sensor 17, logical-arithmetic computing unit 18, first 19 and second 20 Ammitt triggers, threshold unit with memory 21, third 22 and fourth 23 Schmitt triggers , the first 24 and second 25 elements And, the second detector 26, relay th block 27, master 28, first 29 and second 30 integrators, second adder 31, first 32, second 33, third 34 and fourth 35 inputs of switch 6, first 36, second 37, third 38 and fourth 39 information inputs of switch 6, regul L 40 position, speed controller 41, stopping distance detection device 42,

In Figure 2, the DC is the error signal of truth, CO is the speed of rotation of the shaft of the electric motor 14.

In parallel, the first amplifier 3 and the first integrator 29 perform in this system the functions of the position regulator 40, and the second amplifier 5 and the second integrator 30 connected in parallel are the regulator

15

g 10

torus 41 speeds. Depending on the technological requirements for this system, the position controllers 40 and speed 41 can be either proportional-integral with transfer functions such as Wp K +

+ rr. or proportional with trans-CH

with sufficient functions such as W.K, where K, K (J is the transfer coefficients of the proportional and integral component of the law of regulation; T is the integration time constant. The transition from one type of position controllers 40 and speed 41 to another can be easily accomplished by zeroing transfer coefficient K (j, i.e. zeroing of transfer factors of integrators 29 and 30.

The current regulator 12 is typically proportional-integral.

Trigger

The system works as follows.

In the initial state, the position mismatch is zero and the signal at the output of the second adder 31, i.e. at the output of the speed controller 41, is absent. In this case, the output of the first Schmitt trigger 19, operating in the field of negative voltages, to the first control input 36 of the switch 6 receives a logical signal 1.

The trigger thresholds for triggers 19–23 of Schmitt are given in Table 1, where the maximum allowable current;

Trigger

TO

TO

TO,

AT And giving sensors

- the coefficient of flow, speed and poloTrigger

wives; maximum speed allowed; b.Uf- rational way of braking.

Table 1

T

Threshold

Due to the presence on the first control input 36 of the switch 6 logical signal 1 to its output

its first information input 32 is connected.

Table 2 shows the state of the information inputs of the switch 6, depending on the presence of signals at its control inputs.

Table 2

36

37 38 39

32

33 34 35

The movement task signal is simultaneously fed to the second input of the arithmetic unit 18 and the second input of the error meter 1. The position mismatch from the output of meter 1 is mismatched to the input of the first detector 2 and then to the input of the first amplifier 3 and the first integrator 29, which form the position regulator 40, and then from their outputs through the first adder 4 - the second amplifier 5 and the second integrator 30, forming together with the second adder 31 speed controller 41

If the motion task is so small that it does not saturate the speed controller 41 and triggers the second trigger, 20 Imitt, then the state of the switch 6 of the positioning end will not change. The output of the second adder 31, i.e. the output signal of the speed controller 41, through the switch 6, is fed to the information inputs of the keys 10 and 11. Relay unit 27, made for example on the basis of an amplifier with a large gain, opens one of the keys (with a positive polarity of the driving signal, the key 11, the negative is the key 10), whereby the signal for the current to be supplied to the corresponding input of the current regulator 12 and the electric motor 14 rotates at a given angle. The reverse of the current task with negative, nom. the assignment is moving

0

five

0

50

The signal is applied to the inverting input of current regulator 12.

If the motion task causes the speed controller 41 to pinch, then when its output voltage reaches the saturation voltage value, the second Schmitt trigger 20 is triggered by supplying the logical signal 1 to the second control input of the switch 6, leading to switching of the switch 6 output the first information input 32 to the second 33; The second information input 33 of the switch 6 is supplied with a constant positive voltage from the output of the first source 7 of the constant signal, equal to the reference for the maximum permissible current. Due to this, a constant signal arrives at the input of current regulator 12, ensuring the current of electric motor 14 throughout its acceleration, regardless of the state of speed controller 41.

When a target signal arrives at a position at the input of the braking distance determination device 42, it calculates the braking distance values and the required system speed with an idealized triangular tachogram in accordance with the expression;

. c. S | -

(one)

 Sl)

Where

with

R

if CROSS CO

Max

Sl)

e

WITH

Max

if COMPLETE j max

0 if Soffr j j

1, if CO ,, e;

BOS ,. tr

braking distance of the system; required system speed;

Ep is the permissible system acceleration during acceleration;

To allowable deceleration

system when braking; Move the maximum system speed.

The values of e, are given in the form of constant coefficients D to the device 42 for determining the stopping distance in the process of pre-launch system settings.

In one of the possible ways of performing the system, the device for determining the braking distance can be implemented using logical-arithmetic unit 18 and the threshold block with memory 21. In this case, when a reference signal is received, the input of the device 42 for determining the braking distance is immediately fed to the first input logical-arithmetic computing unit 18. The latter, in accordance with expression (1), calculates the value of the required speed. The signal proportional to the required speed comes from its first output to the input of the cost unit with memory 21, the response level of which is proportional to the saturation level of the position controller 40 and, therefore, the maximum allowable speed CO max system. Due to this, the logic signal 1 at the output of the threshold block with memory 21 appears only for large tasks, the displacements that need to be worked on the trapezoidal tachogram,

From the second output of the logical-arithmetic computing unit 18 to the analog output of the device 42 for determining the stopping distance and then to the control input of the fourth trigger j Gera 23 Ymitta a signal is received at which it is necessary to begin braking in the system.

If, COT-p i max logical. The skip signal 0 at the output of the threshold block with memory 21 and at the second input of the logical-arithmetic computing block 18 is equal to 0. In this case, when calculating the AHtor, COT COT-p is taken. If Sztr and. CO max then the logical signal 0 - at the output of the threshold block with memory 21 and at the second input of logical-arithmetic unit 18 is equal to 1. In this case, when calculating. is accepted

. W CPU tJ Mq COP

one. .

The second term in expression (1)

for ASRT-oro, it provides an earlier onset of braking, thereby compensating for the inertia of the current control loop in the system and

0

0

five

0

overshoot is eliminated.

The fourth Schmitt trigger 23 is triggered upon reaching;, the signal at its information input is set by the signal at the control input, i.e. upon reaching a mismatch on the position of the magnitude,

As soon as the start signal of the first detector 2 reaches the value of the fourth Schmitt trigger 23 is triggered, the logical signal 1 from its output through the first element 24 goes to the third control E- input 38 of switch 6, which leads to connecting the output of switch 6 to its third information input 34, reverse the current motor 14, and the start of deceleration (the third information input 34 of the switch 6 is supplied with a constant negative voltage from the output of the second constant source 8, equal in value to the reference signal and the maximum allowable current), the presence of the first element AND 24 prevents the forced reversal of the current demand for small displacement tasks when saturation of the speed controller 41 does not occur.

As the discrepancy in position decreases, the signal at the output of the second adder 31, i.e. at the input of the speed controller 41, it becomes negative, oversaturated the latter. As soon as the oversaturation of the speed controller 41 ends, the first Schmitt trigger 19 operating in the negative voltage region triggers and sends a logical signal 1 to the first control input 36 5 of the switch 6, connecting the output of the switch 6 to its first information input 32 and most to the output of the second adder 31, i.e. to the output of the speed controller 41.

The forced reversal of the current demand and its maintenance up to the supersaturation of the speed controller 41 ensures the invariance of this system to the magnitude of the gain of the amplifier 5 of the speed controller 41.

Thanks to an earlier start of braking the exit from the regulation

0

0

five

The speed of the A1 torus occurs when the speed is positive, close to zero and misaligned in position, which is the reason for the absence of position overshoot in this system at maximum speed.

If the task to move to

so much 60 then cx

Max.

and when working off the average displacements, with the only difference that at the very beginning of acceleration from the logic output of the stopping distance block 42, the first input of the second element AND 25 receives a logical signal 1. In this case, the value is calculated in accordance with the expression (1) provided that 0) When the speed 14 of the motor 14 reaches the value mj, the signal of the speed sensor 18 causes the output of the third Schmitt trigger 22 of the logic signal 1, which through the second element AND 25 goes to the fourth control input 39 of the switch 6, due to which the stroke of the latter switches to its fourth information input 35, which is supplied with a constant positive voltage from the output of the source 9 of the constant signal, equal to the reference for static current. Thus, the reference to the input of current regulator 12 is set to static current and acceleration is terminated. In this case, due to the opening of the speed loop, the process of current reduction is accelerated, the speed controller 41 is prevented from being repeated again when the speed oscillates around the set value and the static speed error is eliminated if the speed controller 41 is proportional. Upon reaching the mismatch on the position of the value from the output of the fourth Schmitt trigger 23, through the first element 24, the third control input 38 of the switch 6 receives a logical signal 1, which causes the switching of the output of the switch 6 to its third information input 34. In the future, the system works similarly to its operation. when working out the average displacements.

This system due to the compensation of the inertia effect of the current control loop and the final lead

0 5 o 5

five

0

five

0

The amplification factor of the speed controller amplifier 5 ensures maximum performance and no overshoot in position when working out medium and large displacements. In addition, since in the proposed electric drive the moment of transition to braking does not depend on the gain of the amplifier 3 of the position controller, the latter can have a linear characteristic and be tuned to test the small discrepancies.

Claims (1)

Invention Formula An electric drive position control system containing a relay unit, first, second and third sources of permanent signals, first and second AND elements, the first integrator, the first adder and the second integrator, and the first and second switches connected to the first, respectively, are connected in series and the second inputs of the current regulator, connected by the third input to the code of the current sensor, and the output to the input of the power amplifier connected to the first output of the first winding terminal of the electric motor and the second output through the current sensor - with the second output of the motor core winding, the shaft of which is kinematically connected to the shafts of the speed sensor and the position sensor connected by the output to the first input of the meter, matching, connected by the second input to the output of the first detector, characterized in that, in order to achieve a fast operation of the system, a second detector, a braking distance detection device, four Schmitt triggers, are introduced into it. the switch, the first and second amplifiers and the second adder connected by inputs to the outputs of the second amplifier and integrator, and the output to the inputs of the first and second Schmitt triggers and to the first information input of the switch connected to the information inputs of both keys, the second, third and the fourth information inputs - with the outputs of the corresponding sources of constant signals, the first control input - with the output of the first trigger Schmitt, the second lane input - with the output of the second Schmitt trigger and with the first input of the first element And, the third control input - with the output of the first element And, and the fourth control input - with the output of the second element And connected by the first input to the logical output the device for determining the braking distance, and the second input to the output of the third trigger 1, connected by input with the code of the second detector connected by the input to the output of the speed sensor and the second input of the first adder, is connected the output of the second amplifier, and the third input of the first amplifier connected to the output of the first detector, the input of the first integrator and the information input of the fourth Schmitt trigger connected to the second input of the first element I, and control; - with an analog output of a braking distance detection device connected by an input to an output of a setting device and an input of a relay unit connected by an output with control inputs of both keys. 0 .05 , o.c. 0.1 0.15 0.2 phil, z