JPS5858689B2 - Positioning method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a positioning method for robots, etc.

Conventionally, positioning of robots and the like has been performed using a method as shown in FIG.

This method is a feedback control method in which a speed command is given to the drive device according to the deviation between the current position and the target position.

In this figure, the position detector 9 is, for example, a pulse encoder, which detects the current position digitally.

The subtracter 1 inputs the detection signal from the position detector 9 and the signal corresponding to the target position, and outputs their deviation.

The deviation signal output from the subtracter 1 is applied to a digital-to-analog conversion circuit 2 and converted into an analog signal.

FIG. 2a shows the output of this digital-to-analog conversion circuit 2.

That is, the magnitude of this output voltage is proportional to the distance from the target position, is maximum at the positioning control start point, becomes smaller as it approaches the target position, and becomes zero when the target position is reached.

The output of the digital-to-analog conversion circuit is divided into two directions, one being input to the i-junction multiplexer 3, and the other being input to the multiplexer 3 via a resistor R and a capacitor C.

The output of the multiplexer 3 is switched by a switching command signal, and at the start of a positioning operation, it selects and outputs a signal with a slow rise that has passed through a resistor R and a capacitor C, and switches to the other signal after a predetermined time has elapsed.

The reason why the deviation signal rises slowly at the start of positioning control is because the deviation signal is steep at the start of control, as shown in Fig. 2a, so this method of speed control based on the deviation signal This is because, in this type of system, if the deviation signal is not made gentle, a large voltage will be suddenly applied to the actuator 1 from a stopped state, causing a sudden acceleration of the controlled object 19 and having an adverse effect.

The output of multiplexer 3 is routed to limit 4.

The limiter 4 limits the magnitude of the signal applied from the multiplexer 3 in accordance with the maximum speed designation signal Vm applied from the outside, and its output signal is as shown in FIG.

That is, when positioning control is started, the output of the multiplexer 3 appears as is at the output of the mink 4, and the voltage of the limiter 4 gradually increases.

The output voltage of the multiplexer 3 is the maximum speed designation signal V.
When the voltage exceeds the voltage specified by m, the limiter 4 maintains and outputs the specified voltage.

When the controlled object 19 approaches the target position and the output voltage of the multiplexer 3 decreases to below the specified voltage, the output voltage of the multiplexer 3 appears as it is at the output of the limiter 4, and the output of the limiter 4 The voltage gradually decreases and reaches O when the target position is reached.

Here, the rate of decrease, that is, the deceleration, changes depending on the loop gain of the circuit shown in FIG. 1, and the time required to reach the target position changes accordingly.

For example, if the loop gain is large, the time to start deceleration will be delayed as shown by the dotted line in FIG. 2, but since the deceleration will be large, the time required to reach the target position will be shortened.

Furthermore, if the loop gain is small, the time to start deceleration will be earlier as shown by the dashed line in the figure, but since the deceleration will be smaller, the time until the target position will be reached will be longer.

The output signal (speed command signal) of the □ vine 4 above is the addition point 5
added to.

The tacho generator 8 detects the actual speed of the controlled object 19 and adds the detection signal to the addition point 5.

The summing point 5 calculates the deviation between the two input signals, applies the deviation signal to the actuator 7 via the amplifier 6, and drives the actuator 7 so that the deviation signal becomes zero.

By the way, in the feedback control method as described above, in order to perform accurate positioning, the loop gain must be increased, which results in an increase in deceleration.

Furthermore, since the loop gain is determined from the viewpoint of system stability, there is a drawback that the deceleration rate is not always optimal.

The present invention has been made in view of the above-mentioned points, and aims to provide a positioning method that is highly accurate and operates quickly (it does not take much time to reach the target position).

According to this invention, a speed pattern (change in speed with respect to time) during acceleration and deceleration is determined in advance according to the capacity of the actuator, etc., and the speed is controlled according to this speed pattern until it approaches the target position. When approaching the position, the speed control is switched to a feedback control method according to the deviation between the target position and the current position.

In speed control using the feedback control method in the second half, even if the loop gain is made small (deceleration is made small) and the deceleration of the speed pattern used in the first half is made large, it is possible to correct errors caused by this. I'm trying to make it possible.

The present invention will be described in detail below based on an embodiment of the accompanying drawings.

In the embodiment shown in FIG.
From 0, a speed command signal cp that changes according to the time from the start of positioning control is output, and a deviation signal generator 2
From 1, a speed command signal (deviation signal) Ep changes in proportion to the deviation between the target position (this is Se) and the current position.
is output.

When positioning, from the first half (control start position (this is referred to as Sa)) to just before the target position Se (this position is referred to as S
The signal Cp from the speed pattern generation section 20 is used as the speed command signal for the second half (from the position Sd to the target point Se), and the signal Ep from the deviation signal generation section 21 is used for the second half (from the position Sd to the target point Se). .

First, the deviation signal generating section 21 will be explained.

The position detector 9 detects the current position using a pulse encoder or digital method, for example, and applies a detection signal to the subtracter 1 of the deviation signal generator 21.

A signal indicating the target position Se is given to the subtracter 1 from the other side, and the subtracter 1 finds the deviation between this signal and the detection signal.

The deviation signal output from the subtracter 1 is divided after passing through the digital-to-analog converter 2, one of which is led to the multiplexer 16 as a speed command signal Ep via the amplifier 3, and the other to the absolute value converter 4. .

The absolute value converter 4 converts the input deviation signal into an absolute value (removes the sign), and sends the signal 1Epl to the comparator 1.
0 and the comparator 12 of the speed pattern generating section 20.

The speed pattern generator 20 receives a signal V specifying the maximum speed.
m is input.

This signal Vm is applied to the acceleration/deceleration function generating circuit 13.

The acceleration/deceleration function generating circuit 13 stores acceleration and deceleration patterns (changes in speed with respect to time), and when a signal instructing acceleration or deceleration is given from the comparator 12, each pattern is read out according to time. It will be done.

Moreover, when the magnitude of the signal reaches the maximum speed designation signal Vm while the acceleration pattern is being read out, that value is maintained and output.

Therefore, the signal output from the acceleration/deceleration function generating circuit 13 has a trapezoidal shape as shown in FIG. 4a, for example.

By the way, in this embodiment, the speed is always constant at a predetermined position Se before the target position Se (that is, the value of the speed command signal output from the acceleration/deceleration function generation circuit 13 based on the deceleration pattern remains). 9 so that the voltage reaches e.

For this reason, the position at which the deceleration command signal is applied from the comparator 12 to the acceleration/deceleration function generation circuit 13 (tying →) is changed depending on the deceleration pattern and the maximum speed designation signal Vm.

That is, in the function shown in FIG. 4 (a function obtained by converting the time axis (horizontal axis) of the deceleration pattern to the distance axis), when the maximum speed designation signal is Vml, the position at which the deceleration command signal is applied is Sb, Also, when Vm22 and Vm3, S
b2. Sb3, and always at the above predetermined position Sc.
The deceleration ends at , and a constant speed is maintained from then on.

The deceleration region function generating circuit 11 stores the function shown in FIG. A signal Dp is output.

The comparator 12 receives the signal IE from the absolute value converter 4.
pl and the signal Dp indicating the deceleration region, and 1
The acceleration/deceleration function generating circuit 13 outputs an acceleration command signal when Epl>Dp (that is, when the deceleration starting point has not been reached), and a deceleration command signal when 1Ep1<Dp (that is, when the deceleration starting point has been exceeded). In addition, as described above, the speed command signal is outputted from the circuit 13 based on the acceleration or deceleration pattern.

This speed command signal is then split into two directions, one being directly input to the multiplexer 15 and the other being input to the multiplexer 15 via the inverter 14, respectively.

The multiplexer 15 selects and outputs one of the above-mentioned two-person forces in accordance with the sine signal (a signal indicating positive and negative polarities, which corresponds to the positioning direction) applied from the subtracter 1.

The output of multiplexer 15 is input to multiplexer 16.

During deceleration, the multiplexer 16 switches from speed control based on a speed pattern (i.e., control based on signal Cp) at a predetermined position (hereinafter referred to as control switching point Sd) to speed control based on a feedback control method according to the deviation between the target position Se and the current position. Control (i.e. control by signal Ep)
This is for switching to .

Further, the comparator 10 is for providing this switching signal to the multiplexer 16.

That is, the comparator 10 compares the absolute value deviation signal IEpl from the absolute value converter 4 and the signal Pe indicating the position servo area (distance between the target position Se and the control switching point Sd), and determines the relationship between them. When Epl>Ps (when the control switching point Sd has not been reached), the output of the multiplexer 16 is used as the signal from the multiplexer 15, and when IEpl<PS (when the control switching point Sd has not been reached), the deviation from the amplifier 3 is (The output signal of this multiplexer 16 is shown in FIG. 4C.

) At this time, the value of the speed command signal and the residual voltage e at the predetermined position SC output from the acceleration/deceleration function generating circuit 13 can be set from the outside, and generally the value of the signal CP and the signal EP at the control switching point Sd can be set externally. Set the value to be equal to the value of .

The output signal of multiplexer 16 is input to multiplexer 11.

This multiplexer 17 is for switching between manual speed setting and automatic speed setting, and selectively outputs one of the signal applied from multiplexer 16 and the manual speed setting signal as a manual-automatic switching signal.

The output of multiplexer 11 is added to summing point 18.

Additionally, the tachogenerator 8 detects the actual speed of the controlled object 19 and adds a detection signal to the addition point 18 .

The addition point 18 calculates the deviation of the above two input signals,
applying the deviation signal to the actuator 7 via the amplifier 6;
The actuator 7 is driven so that the deviation signal becomes zero.

Now, the change in speed when positioning is performed based on the speed designation signal shown in FIG. 4C is shown in FIG. 4D.

In this figure, the dotted line indicates that the time axis (horizontal axis) of the graph in FIG. 4C has been replaced with a distance axis.

Since there is a large change in the command value (dotted line) from the deceleration opening position sb, the actual speed is slightly later than that.

When the command value becomes constant at position Sc, the actual speed also becomes constant with a slight delay.

When the control is switched at the position Sd, the slope of the command value becomes gentle, so the actual speed becomes almost the same, and the motor stops at the target position Se.

As explained above, according to the present invention, the positioning control is performed in two stages, and the deceleration in the second stage is made small.
Even if the step deceleration is large, positioning can be performed quickly and with little error, and the acceleration and deceleration (first step) can be set arbitrarily according to the actuator's capabilities. effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a conventional positioning method, FIG. 2 is a graph explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a block diagram showing an embodiment of the present invention. FIG. 4 is a graph showing the operation of the embodiment shown in FIG. 1... Subtractor, 4... Absolute value converter,
1...Actuator, 11...Deceleration region function generator, 13...Acceleration/deceleration function generator.

Claims (1)

[Claims] 1. Means for determining the positional deviation between the current position and target position of the positioning object, a first circuit that outputs a speed command signal according to this positional deviation, and maximum speed specifying means for specifying the maximum moving speed of the positioning object. and deceleration area function generating means for outputting a signal indicating a braking distance required for the positioning target to stop from that speed for each speed specified by the maximum speed specifying means, and a deceleration area function generating means that is a distance shorter than the braking distance. , a position servo area distance setting means that outputs a signal indicating the distance of the area to which the position servo is applied, compares the determined position deviation with the braking distance, and starts deceleration at the point when the position deviation becomes smaller than the braking distance. a first comparator that detects a point in time, and a second comparator that compares the determined position deviation with the position servo area distance and detects a control switching point from a point in time when the position deviation becomes smaller than the position servo area distance. outputs a speed command signal that has predetermined acceleration/deceleration characteristics and accelerates according to the time from the positioning start point,
When the speed of the speed command signal reaches the speed designated by the maximum speed designation means, the speed command signal is maintained and outputted, and when the first comparator detects the time point at which deceleration starts, the time from the time of detection acceleration/deceleration function generating means for outputting a speed command signal that decelerates the speed of the maintained speed command signal in accordance with the speed of the maintained speed command signal; A positioning system comprising: control means for controlling a positioning target based on a command signal; and controlling the positioning target based on a speed command signal from the first circuit after the second comparator detects a control switching point. .