JPH06230818A - Servo controller - Google Patents

Abstract

PURPOSE:To provide a servo controller allowing a controlled object to quickly and highly accurately follow up an optional objective route within the restriction of allowable acceleration and allowable speed. CONSTITUTION:An objective speed generating part 2 generates the objective speed values vi (t) of respective driving shafts of a controlled object from objective route data DT and objective speed data DV applied from an input device 1. Acceleration detectors 3-i prepared at every shaft detect an objective acceleration value from its corresponding objective speed value vi (t) and comparators 4-i generate the rate of the objective acceleration value to the allowable value of prescribed acceleration and the rate of the objective speed value to the allowabvle value of prescribed speed respectively as 1st and 2nd signals. Each of inter-shaft coordinating parts 5-i compares the size of the 1st signal with that of the 2nd signal and calculates a time directional variation common to respective motors so that all the motors satisfy the allowable values of the acceleration and the speed. Each of speed conversion parts 6-i changes the objective speed value in accordance with the time directional variation to convert the objective value into a speed signal to be followed by a driving shaft motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device for a machine tool or a robot, and more particularly to a servo control device capable of following a target route at high speed and with high accuracy.

[0002]

2. Description of the Related Art When a curved surface is machined in a machine tool or a robot or the path of a multi-degree-of-freedom robot hand is controlled, it is important to precisely control the moving path of the controlled object. Here, the control that causes the movement path of the controlled object to follow the target spatial path is referred to as path tracking control.

Conventionally, it is effective to increase the system gain of the control system in order to realize high-speed and highly accurate path following control, but in reality, due to mechanical system restrictions, the target speed is set to a point where the allowable accuracy is satisfied. It is necessary to lower and follow the route, which prevents high speed.

On the other hand, there is a servo control device that artificially raises the system gain by feedforward control to secure high speed. However, this increases the responsiveness to the target route while maintaining the high speed, and attempts to strictly follow the rapid change in the corner portion of the target route at the high speed. As a result, a large acceleration exceeding the capability of the mechanical system, especially the motor is required, and shock or vibration is generated. On the other hand, there is also a servo control device that prevents a rapid speed change by passing a target speed value for each axis to be controlled through a linear filter. However, since the low-pass filter is connected to the control system, the high-frequency component of the target path is lost, resulting in an error in the tracked path.

Further, there is a servo control device that detects a change in the moving direction of a corner portion by recognizing the shape of a target route, reduces the speed at a portion requiring a large acceleration, and suppresses the acceleration to a small level to improve the tracking accuracy. is there. However, in order to detect the acceleration, complicated processing such as shape recognition and detection of the moving direction is required, and high arithmetic processing capability is required, which is difficult to realize.

As another servo control device, Japanese Patent Laid-Open No. 4-33012 discloses a method of setting a speed target value so as to satisfy a predetermined constraint of allowable speed or allowable acceleration. FIG. 16 is a block diagram showing this servo control device. In the figure, the speed calculator 10
Reference numeral 2 compares the speed target value given from the input unit 101 with preset speed allowable values for the X and Y axes, and outputs the smaller one as a new speed target value. Further, the acceleration calculation unit 105 generates an allowable acceleration from the preset allowable acceleration value for each axis and the amount of change in the velocity target value supplied from the input unit 101, and outputs it to the acceleration processing unit 104 as an acceleration set value. . The speed signal generation unit 103 generates a step-shaped speed signal from the calculation result of the speed calculation unit 102, and the acceleration / deceleration processing unit 104 adjusts the rising and falling of the step-shaped speed signal to the output value of the acceleration calculation unit 105. And shape the waveform smoothly. The velocity distribution unit 106 obtains each axis component of the velocity waveform subjected to the acceleration / deceleration processing.

[0007]

According to the prior art shown in FIG. 16, the rapid rising and falling of the stepped speed target value changes depending on the allowable value of the acceleration, so that high-speed and highly accurate path tracking is possible. Can be realized.

However, in this servo control device, since the acceleration processing section performs the acceleration / deceleration processing only on the stepped speed signal, it is impossible to perform follow-up control on an arbitrary free-form curve path in which the speed signal changes moment by moment. There was a problem.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a servo control device which makes a controlled object follow a target path of various shapes including a curve at high speed and with high accuracy.

Another object of the present invention is to provide a servo control device which follows a controlled object at high speed and with high accuracy without recognizing the shape of the target path.

The servo control device according to the present invention uses a plurality of motors connected to a plurality of axes for driving an object to be controlled,
The target speed generation unit generates a speed target value that is a target value of the drive speed of each motor for each axis based on the target path. Then, the acceleration detector provided for each axis detects the acceleration target value from the speed target value from the target speed generator. Next, the comparator or the arithmetic unit indicates the ratio of the acceleration target value detected by the acceleration detection unit to the allowable value of the predetermined acceleration.
Signal and a second signal indicating the ratio of the speed target value to the allowable value of the predetermined speed are generated and output to the inter-axis cooperation unit. The inter-axis coordinating unit compares the magnitudes of the first signal and the second signal, and calculates a time-direction change amount common to each motor so that the plurality of motors satisfy the acceleration allowable value and the speed allowable value. To do. Finally, the speed conversion unit changes the speed target value according to the amount of change in the time direction so as to move the same distance as the distance that the controlled object moves when driving the motor at the speed target value, and at the same time generates the speed signal. The time at which the speed signal is generated is also changed. The speed signal is a signal for rotating the motor.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, an input device 1 is an NC operating on the basis of a host computer or an NC program.
The apparatus generates target route data DT representing the shape or position coordinates of the target route and target velocity data DV representing the following velocity of the target route. The controlled object that follows the target path is, for example, the first axis, the second axis, ...
A robot hand that moves in each axial direction by 1, 11-2, ..., 11-n. The target route data DT is data of center coordinates and radius of the circle when the target route is a circle, and position coordinate data of start and end points of the straight line when the target route is a straight line. Further, when the target route is a free curve, it is position coordinate data obtained by sampling the route at predetermined intervals.

The target speed generator 2 is based on the target route data DT and the target speed data DV from the input device 1,
Axis target value v _i (τ) (i =
1, 2, 3, ..., N; τ is a time parameter). This velocity target value is an angular velocity signal of a motor for moving the robot hand in each axial direction according to the target route, and is sequentially generated at a predetermined sample time dτ. That is, the velocity target value v _i (τ) is an angular velocity signal that rotates the motor 11-i during the minute time dτ. dτ is, for example, 1 ms.

Acceleration detector 3-i (i = 1, 2, 3 ...
, N), the comparator 4-i, the inter-axis cooperation section 5-i, the speed conversion section 6-i, the buffer 7-i, and the stop signal generator 8,
This is a device that changes the speed target value v _i (τ) into a converted speed signal v _i (t) in order to realize high-speed and highly accurate path following control. However, the subscript i of each reference numeral represents the first to n-th axes that drive the controlled object.

The acceleration detector 3-i has a velocity target value v
_An acceleration target value is generated from the difference between _i (τ) and the converted speed signal v _i (t) with respect to the speed target value one sample before the speed target value. The comparator 4-i detects whether or not the acceleration target value and the velocity target value exceed the preset acceleration allowable value and the speed allowable value, respectively, and further shows the first and second ratios indicating respective exceeding ratios. The signal of is output. Inter-axis cooperation section 5
-I obtains the maximum value from the first and second signals from each comparator 4-i, and determines the maximum value as the time direction change amount S (τ).
Output as. The speed conversion unit 6-i converts the time τ into a new time t by extending the time axis of the time τ by the amount of change S (τ) in the time direction, and accordingly the speed target value v _i (τ) of each axis. ) Is reduced to the reciprocal of the change amount S (τ) in the time direction to convert into a velocity signal v _i (t) at time t. The buffer 7-i includes an acceleration detection unit 3-i and a comparison unit 4.
-I and the inter-axis coordinating unit 5-i are storage means for temporarily storing the speed target value v _i (τ) for the processing time. Further, the interlock signal generator 8 changes the time direction change amount S (τ).
A stop signal ST is generated to stop the generation of the target velocity value v _i (τ) for the time lengthened by.

Next, the configuration and operation of each part of the servo controller of FIG. 1 will be described in more detail.

FIG. 2 is a block diagram of the target speed generator 2. The target speed generator 2 has an interface 21 with the input device 1, a target route data DT, and a target speed data DV.
A microprocessor 22 that calculates a velocity target value v _i (τ) of each axis based on the above, a read-only memory (ROM) 23 that stores a program for the calculation of the microprocessor 22, and a work that is used during the calculation. A random access memory (RAM) 24 having an area.
The microprocessor 22 continuously generates the speed target value v _i (τ) at every sampling time dτ, but suspends the output of the speed target value while the stop signal ST is supplied from the stop signal generator 8.

FIG. 3 is a flowchart showing the operation from the generation of the speed target value v _i (τ) to the generation of the converted speed command v _i (t).

The target speed generator 2 uses the target route data DT.
A speed target value for each axis of the n-axis from the first axis v _i (τ) for generating in accordance with the target speed data DV (step 1,
2). The acceleration detector 3-i has its velocity target value v
_The acceleration target value a _i (τ) is generated from the difference between _i (τ) and the converted speed signal v _i (t) for the speed target value one sample before (step 3). Here, the acceleration target value a
_i (tau) is given by: _{a i (τ) = {v} i (τ + dτ) -v i (t)} / dτ (1). That is, the acceleration target value a _i (τ) is
The velocity signal v _i (t) obtained by actually moving the motor 11-i one sample before is used as the velocity target value v _i (τ) at the next sample.
It corresponds to the amount of acceleration required to

The comparator 4-i converts the target acceleration value a _i (τ) into a predetermined allowable acceleration value A _{i, max} (i = 1, 2, 3, ...).
, N), and the speed target value vi (τ) is set to a predetermined speed allowable value Vi _{, max} (i = 1, 2, 3, ..., N).
Compare with. Further, the comparator 4-i includes the acceleration detection unit 3
When the acceleration target value a _i (τ) detected by −i exceeds the acceleration allowable value A _{i, max} (step 5),
The information is sent to the inter-axis coordinating unit 5-i by inputting the excess acceleration signal _{Sa, i.}
Report as (τ) (step 6). At this time, the excess acceleration signal S _{a, i} (τ) is obtained by the following equation. S _{a, i} (τ) = | a _i (τ) | / A _{i, max} (2) However, when the allowable value is not exceeded, S
_{Let a, i} (τ) = 1 (step 7). The over-acceleration signal S _{a, i} (τ) represents the degree to which the acceleration exceeds the allowable value. Similarly, when the speed target value v _i (τ) exceeds the predetermined speed allowable value V _{i, max} (step 9), the comparator 4-i informs the inter-axis coordinating section 5-i. The information is transmitted as an overspeed signal S _{v, i} (τ) (step 10). At this time, the overspeed signal S _{v, i} (τ) is obtained by the following equation. S _{v, i} (τ) = | v _i (τ) | / V _{i, max} (3) However, when the allowable value is not exceeded, S
_{Set v, i} (τ) = 1 (step 11). The overspeed signal S _{v, i} (τ) represents the degree to which the speed exceeds the allowable value.

FIG. 4 is a detailed block diagram of the comparator 4-i. In the figure, a comparator 4-i includes circuits 40 to 43 for executing steps 4 to 7 of FIG.
And circuits 44 to 47 for executing. Circuits 40-43
And the circuits 44 to 47 have the same configuration and operate simultaneously. That is, the comparator 4-i includes absolute value circuits 40 and 44, a comparison circuit 41 that detects whether the acceleration target value | a _i (τ) | exceeds the acceleration allowable value A _{i, max} , and a speed target value. ｜
A comparison circuit 45 for detecting whether or not v _i (τ) | exceeds the speed allowable value V _{i, max} , a division circuit 42 for calculating the expression (2), and a division circuit 46 for calculating the expression (3). , A selection circuit 43 that selects the output of the comparator 41 as "1" data or the output of the division circuit 42 as the acceleration excess signal S _{a, i} (τ), and the output of the comparator 45 is "1" data or the division A selection circuit 47 for selecting the output of the circuit 46 as the overspeed signal S _{v, i} (τ).

Returning to FIG. 2, the inter-axis coordinating section 5-i receives the acceleration excess signal S _{a, i} (τ) and the speed excess signal S _{v, i} (τ) from the comparator 4-i, When a drive axis that exceeds the constraint condition is searched and there is an axis that exceeds the constraint condition, that is, when S _{a, i} (τ)> 1 or S _{v, i} (τ)> 1, all drive axes are accelerated. The amount of change in the time direction (time parameter τ so that the constraints of the allowable value and the speed allowable value are satisfied)
(Actual rate of change of the time t with respect to) is transmitted to the velocity conversion unit 6-i for each axis. At this time, the change amount S (τ) in the time direction is obtained by the following equation (step 12). S (τ) = max {S _{a, i} (τ), S _{v, i} (τ)} (4) That is, S (τ) is the acceleration excess signal and the speed excess signal from the first axis to the nth axis. Is the largest signal in. The inter-axis coordinating units 5-1 to 5-n simultaneously output the time direction change amount S (τ) obtained from the equation (4). As a result, the inter-axis coordinating section issues an instruction to extend the time axis according to the time direction change amount S (τ) in all the axes, and controls the speed converting section 6-i to coordinate the movement of each axis. . When all the axes satisfy the constraint condition, S (τ) = 1, so that the time axis is not expanded during that period.

FIG. 5 is a block diagram of the inter-axis cooperation units 5-1 to 5-n. Each inter-axis cooperation unit 5-i has a maximum value selection circuit 50-i that compares the magnitudes of input signals and selects the maximum input signal as an output signal, and these are controlled by the control circuit 51. First, the maximum value selection circuit 50-1 compares the acceleration excess signal S _{a, 1} (τ) with the speed excess signal S _{v, 1} (τ) by the control signal c ₁ and selects the larger signal. Next, the maximum value selection circuit 50-2 outputs the output signal of the maximum value selection circuit 50-1, the acceleration excess signal S _{a, 2} (τ) and the speed excess signal S according to the control signal c ₂ .
Select the largest signal from _{v, 2} (τ) and output it. By sequentially performing this operation up to the inter-axis coordinating unit 5-n, the time-direction variation S (τ) satisfying the expression (4) is obtained.

The speed conversion unit 6-i uses the time parameter τ as the time-direction change amount S (τ) determined by the inter-axis cooperation unit 5-i.
Converted speed signal v of each axis to keep the moving distance constant by expanding the speed twice and decreasing the speed at the same time.
_i (t) is generated and output (steps 13 and 14).
At this time, the conversion speed signal v _i (t) of each axis is obtained by the following equation.

V _i (t) = S (τ) / v _i (τ) (5) Therefore, the speed conversion unit 6-i determines whether the acceleration or speed of each axis corresponds to the maximum value of the ratio to the allowable value. By lowering the velocity target value, it is possible to drive each axis while always satisfying the acceleration and velocity allowable values. Also, the actual time t after conversion
And the time parameter τ before conversion is as follows.

[0028]

[Equation 1]

When all the axes satisfy the constraint conditions (S (τ) = 1), the velocity target value v _i (τ) is output as it is as the velocity signal v _i (t), and the constraint condition is obtained even for one axis. If it exceeds, the time target is extended and the speed target value is lowered only during that time. by this,
The velocity target value v _i (τ) is converted into a smooth velocity signal v _i (t) that the drive system can follow.

The above operations from step 2 to step 14 are repeatedly executed every time a sample value of the velocity target value v _i (τ) is generated.

Velocity signal v from velocity conversion unit 6-i
_i (t) is supplied to the subtractor 9-i, and the motor 11-i
The difference from the detection signal of the rotational angular velocity is calculated. Compensator 1
0-i is composed of a control circuit (for example, a PID control circuit) that controls driving of the motor 11-i so that the difference is minimized. The motor 11-i is stably rotated by PID control.

Next, as shown in FIG. 6, regarding the operation of the servo control device of FIG. 1 when the controlled object is moved along a circular orbit on a plane including the first axis and the second axis, the X of NC machine tool will be described.
A description will be given taking the -Y table as an example.

The input device 1 generates target path data DT indicating a radius of a circular orbit and an axis to be driven and target velocity data DV indicating a following velocity on the circular orbit. Target speed generator 2
Is the target velocity data v ₁ (τ) and v for the first and second axes based on the target route data DT and the target velocity data DV.
₂ Calculate (τ) and output. FIG. 7 is a diagram showing time changes of velocity target values v ₁ (τ) and v ₂ (τ) and conversion velocity signals v ₁ (t) and v ₂ (t) for them, respectively.
However, the speed target values v ₁ (τ) and v ₂ (τ) in FIG. 7 do not include the pause time due to the stop signal ST. Although the speed target values v ₁ (τ) and v ₂ (τ) show waveforms that change in an analog manner, the actual speed target values v ₁ (τ),
v ₂ (τ) is equal to a sample value obtained by sampling the waveform of FIG. 7 at a minute time dτ as shown in FIG. Time τ in FIG.
The sampled values at each time point τ ₁ , τ ₂ , τ ₃ , ... On each axis of, ie, the speed target value from the target speed generator 2 are v ₁ (τ ₁ ) and v with respect to the first axis, respectively. ₁ (τ ₂ ), v ₁
(Τ ₃ ), ..., v ₂ (τ ₁ ), v with respect to the second axis
₂ (τ ₂ ), v ₂ (τ ₃ ), and so on. Where dτ =
τ ₂ −τ ₁ = τ ₃ −τ ₂ = τ ₄ −τ ₃ = ...

The acceleration detectors 3-1 and 3-2 respectively detect the velocity target values v ₁ (τ) and v ₂ (τ) and the converted velocity v ₁ (t) and v ₂ (for the velocity target value one sample before. The acceleration target value is generated according to the difference with t), but the initial time τ ₁
Since the conversion speed signal is not generated in, the above (1)
In the formula, both v ₁ (t) and v ₂ (t) are 0. Therefore, the speed target value _{v 1 (τ 1), v} 2 acceleration target value for _{(τ 1) a 1 (τ} 1), a 2 (τ 1) is given by the following equation. a ₁ (τ ₁ ) = v ₁ (τ ₁ ) / d τ a ₂ (τ ₁ ) = v ₂ (τ ₁ ) / d τ Next, the comparing units 4-1 and 4-2 respectively set the acceleration target value a ₁
(Τ ₁ ), a ₂ (τ ₁ ) are acceleration allowable values A _{1, max} ,
Whether or not A _{2, max} is exceeded _, and the target velocity value v ₁ (τ
₁ ), v ₂ (τ ₁ ) are speed allowable values V _{1, max} , V
_It is detected whether or not _{2, max} is exceeded, and the acceleration excess signals S _{a, 1} (τ ₁ ), S are calculated from the equations (2) and (3).
_{a, 2} (τ ₁ ) and overspeed signal S _{v, 1} (τ ₁ ), S
Generate _{v, 2} (τ ₁ ). Inter-axis cooperation unit 5-1 and 5-2
Detects the largest one of the acceleration excess signals and the velocity excess signals of all the axes by the equation (4), and outputs it as the time direction change amount S (τ ₁ ). As shown in FIG. 8, the acceleration until reaching the velocity target value v ₂ (τ ₁ ) at the start of the route tracking is extremely large, and the acceleration excess signal S
_{When a, 2} (τ ₁ ) is the maximum, the time-direction change amount S
(Τ ₁ ) = S _{a, 2} (τ ₁ ).

As shown in FIG. 9, the speed converters 6-1 and 6 are provided.
-2 is based on the equations (5) and (6), and the time parameter dτ is set to the actual time dt ₁ = t ₂ −t ₁ = S (τ ₁ ) · d.
τ, the velocity target values v ₁ (τ ₁ ) of the first axis and the second axis,
v ₂ (τ ₁ ) is the velocity signal v ₁ (t ₁ ) = v
₁ (τ ₁ ) / S ₁ (τ ₁ ), v ₂ (t ₁ ) = v
Convert to ₂ (τ ₁ ) / S ₂ (τ ₁ ). This conversion is only the conversion of the time axis of the first and second axes and the speed, and does not cause the change of the moving distance.

The velocity target values v ₁ (τ ₁ ), v
Velocity signals v ₁ (t ₁ ) and v for ₂ (τ ₁ ).
The conversion to ₂ (t ₁ ) is completed. Next, in the target speed generator 2, the speed converters 6-1 and 6-2 convert the converted speed signal v ₁ (t
₁ ) and v ₂ (t ₁ ) are generated, the following velocity target values v ₁ (τ ₂ ) and v ₂ (τ ₂ ) are generated, and the acceleration detection unit 3
−1 and 3-2 are acceleration target values a ₁ (τ
₂ ), a ₂ (τ ₂ ) is detected. a ₁ (τ ₂ ) = {v ₁ (τ ₂ ) −v ₁ (t ₁ )} / d τ a ₂ (τ ₂ ) = {v ₂ (τ ₂ ) −v ₂ (t ₁ )} / d τ From the comparators 4-1, 4-2 to the speed conversion units 6-1, 6
Repeat the same operation until -2.

The first axis and the second axis converted as described above
The axis velocity signal causes the XY table to follow a circular orbit at high speed and with high accuracy under acceleration and velocity constraints. That is, as shown in FIG. 6, the route according to this embodiment substantially matches the target route.

In the embodiment of the present invention described above, the velocity target value of at least one axis is v _i (τ) or the acceleration target value a _i (τ) exceeds the constraint condition of acceleration or velocity,
When the acceleration excess signal S _{a, i} (τ)> 1 or the speed excess signal S _{v, i} (τ)> 1, the speed target values of all axes are suppressed and the time axes of the respective axes are extended. Was there. However, as in the case of using a light XY table, conversely, the velocity target values v _i (τ) and the acceleration target values a of all axes are
_When both _i (τ) are smaller than the constraint conditions of acceleration and speed and there is a margin in the driving capability of the motor, the control to increase the speed to the constraint condition is not performed. That is, in the latter case, the comparator 4-i causes the over acceleration signal S _{a, i} (τ)
And the overspeed signal S _{v, i} (τ) are forcibly set to 1 and the time-direction variation S (τ) is set to 1, so that the speed conversion unit 6-i
Outputs the speed target value as it is as the speed signal v _i (t).

In the second embodiment of the present invention, the comparator 4-i.
Instead of the above, only the arithmetic units for arithmetically operating the equations (2) and (3), that is, only the arithmetic units 42 and 46 in FIG. 4 are used. As a result, the over-acceleration signal S _{a, i} (τ) and the over-speed signal S _{v, i} (τ) can be set to 1 or less, and the velocity target value v _i (τ) and the acceleration target value of all axes can be set. a
_When both _i (τ) are smaller than the constraint conditions of acceleration and velocity, the time-direction variation S (τ) becomes 1 or less. In this case, the speed converting unit 6-i can increase the speed so that at least one axis is subject to the acceleration or the constraint condition of the speed, and the high speed performance is further improved.

FIG. 10 is a block diagram showing a third embodiment of the servo control device of the present invention.

In the figure, the servo controller of this embodiment is similar to the servo controller of FIG.
(I = 1, 2, 3, ..., N) is provided, and the acceleration allowable value A
_{i, max} and the allowable speed value V _{i, max} are made variable.

Generally, when the load 13-i of the motor 11-i fluctuates and suddenly becomes heavy, the motor 11-i accurately follows the target route under the preset constraint conditions of the acceleration allowable value and the speed allowable value. Becomes difficult. In such cases,
It is necessary to further reduce the acceleration or speed to recover the tracking accuracy. The tolerance control circuit 12-i is configured to load the load 13-i.
The change in the response characteristic of the drive system due to the change in the acceleration is detected, and the acceleration tolerance A _{i, max} and the speed tolerance V _{i, max} are lowered in accordance with the detected change amount, thereby recovering the tracking accuracy. . In this embodiment, as a method for detecting the change in the load 13-i, the speed signal v _i (t) and the motor 11-
A method is used in which the response characteristic of the drive system is measured from the angular velocity detection signal i and the load change is indirectly detected.

FIG. 11 is a block diagram of the allowable value control circuit 12-i.

The allowable value control circuit 12-i includes a subtractor 9-i.
Virtual model 121-i, the compensation unit 10-i virtual model 122-i, the motor 11-i virtual model 123-i,
The virtual model 124-i of the load 13-i is configured by software, and a virtual calculation circuit 120-i for calculating and estimating the rotational angular speed of the motor when the speed signal v _i (t) is input by the microprocessor, and the motor 11 -I and the subtraction unit 130-i for detecting the difference between the angular velocity detection signal from the virtual arithmetic circuit 120-i and the velocity signal v
_A load model adjustment circuit 140-i for modifying the load model based on _i (t) and the output of the subtractor 130-i, and a new acceleration allowable value A according to the modification of the load model.
_{i, max} and a permissible value generation circuit 150-i for generating the permissible speed value V _{i, max} .

The virtual arithmetic circuit 120-i outputs the angular velocity estimation signal assuming a certain load model. Therefore, when the load 13-i rapidly changes and becomes heavy, the difference signal from the subtractor 130-i becomes large. The load model adjustment circuit 140-i uses the increased difference signal and the speed signal v _i.
The change in the load is detected from (t), the parameter of the load model is estimated, the load model is corrected, and the parameter is output to the allowable value generating circuit 140-i. The tolerance value generating circuit 140-i lowers the tolerance value by outputting new acceleration tolerance values A _{i, max} and speed tolerance values V _{i, max} based on the parameters of the modified load model.

Now, assume that a square on a plane including the first axis and the second axis is given as the target route as shown in FIG. If the allowable value control circuit 12-i is not provided, the conversion speed signals v ₁ (t) and v ₂ (t) and the motors 11-1 and 11 are obtained.
The rotation angular velocity of -2 changes as shown in FIG. Figure 1
3, the sections 201 and 202 have loads 13-1 and 13
-2, when there is no large change, sections 203 and 204 show the case where the load 13-1 changes and becomes heavy, and the solid line shows the time change of the conversion speed signals v ₁ (t) and v ₂ (t). The broken line shows the change over time in the angular velocity of the motors 11-1 and 11-2. As shown in the figure, in the sections 201 and 202, the motors 11-1 and 11-2 at the time of rising and falling of each section.
Is driven under the constraint conditions of the acceleration permissible value and the speed permissible value and follows the converted speed signals v ₁ (t) and v ₂ (t) well, but in the sections 203 and 204, the motor 1 is overloaded.
1-1 cannot follow, and the path is disturbed as shown by the broken line in FIG.

However, by adding the allowable value control circuit 12-i as in the embodiment shown in FIG.
In 3,204, the allowable acceleration value can be reduced by adapting to changes in the load. Therefore, as shown in FIG.
The motor 1 with respect to the converted speed signals v ₁ (t) and v ₂ (t)
It becomes possible for 1-1 and 11-2 to follow, and the disturbance of the route does not occur.

FIG. 15 is a block diagram showing a fourth embodiment of the servo controller according to the present invention. In the figure, the comparator 4
-Acceleration allowable value A _{i, max} for _i and speed allowable value V
_{i and max} are directly supplied from the input device 1, and the circuits after the target speed generator 2 are the same as those in the servo control device shown in FIG. The input device 1 is connected to a memory 1A that stores a movement command program. The movement command program is composed of a sub-program for instructing a target route and a target speed, and a sub-program for instructing the allowable acceleration values A _{i, max} and the allowable speed values V _{i, max} .

The input device 1 reads the movement command program from the memory 1A, generates the target route data DT and the target velocity data DV by the subprogram for instructing the target route and the target velocity, outputs the target route data DT and the target velocity data DV to the target velocity generating section, and accelerates the acceleration. The acceleration allowable values A _{i, m ax are} set by the sub-program that specifies the allowable values A _{i, max} and the speed allowable values V _{i, max.}
And the allowable speed value V _{i, max} are output to the comparator 4-i.
In the present embodiment, the constraint conditions of speed and acceleration that change depending on the operation and processing state can be set by writing in the program in advance, so that for example, the posture of the robot changes greatly, or an object is grabbed and carried by the robot hand. When the change of the controlled object, especially the load, is known, such as when the hardness of the work changes with the NC machine tool, the constraint condition is changed in real time without stopping the motor to improve the machine performance. It is possible to pull out to the maximum and always secure the desired tracking accuracy.

[0050]

As described above, according to the servo control device of the present invention, the conversion in the time axis direction is used in the conversion from the speed target value to the speed signal, so that any target path can be obtained. Can be applied. At this time, since the inter-axis coordinating means is provided to determine the amount of change in the time direction, the operation of each drive shaft can be coordinated to maintain the shape of the path. Moreover, not only can the speed and acceleration be kept within the allowable values, but on the contrary, if there is a margin in the speed and acceleration, it is possible to increase the speed by performing a conversion that shrinks in the time axis direction.
The efficiency of the machine can be further improved.

Further, since the allowable value control means for detecting the change in the parameter of the controlled object to change the allowable value of the acceleration or the speed is provided, even if the parameter of the controlled object changes with time, the position shift does not occur and the high value is maintained. You can follow the route accurately. In addition, by providing a means to set constraint conditions such as acceleration and speed from the movement command program, you can change the constraint conditions in real time without stopping the motor when the change of the control target, especially the load, is known. It is possible to maximize the performance of the machine and always ensure the desired tracking accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of a servo controller according to the present invention.

FIG. 2 is a detailed block diagram of a target speed generator used in the servo controller shown in FIG.

FIG. 3 is a flowchart showing an operation of the servo control device shown in FIG.

FIG. 4 is a detailed block diagram of a comparator used in the servo control device shown in FIG.

5 is a detailed block diagram of an inter-axis cooperation unit used in the servo control device shown in FIG.

6 is a plan view showing a target route and a route to be controlled by the servo control device shown in FIG. 1. FIG.

FIG. 7 is a diagram showing a time change of a speed target value and a converted speed signal for following the target route shown in FIG.

FIG. 8 is a timing chart showing in detail the time change of the speed target value shown in FIG.

9 is a timing chart showing in detail the change over time of the conversion speed signal shown in FIG.

FIG. 10 is a block diagram showing a third embodiment of the servo controller according to the present invention.

11 is a detailed block diagram of a tolerance control circuit used in the servo control device shown in FIG.

FIG. 12 is a plan view showing a square target route and a route to be controlled when the load fluctuates midway.

FIG. 13 is a diagram showing a case in which there is no tolerance control circuit shown in FIG.
It is a figure which shows the conversion speed signal with respect to the target course shown in FIG. 12, and the time change of the angular velocity of a motor.

14 is a diagram showing a change over time in a conversion speed signal and a motor angular speed with respect to the target path shown in FIG. 12, when the tolerance control circuit shown in FIG. 11 is used.

FIG. 15 is a block diagram showing a fourth embodiment of the servo control device according to the present invention.

FIG. 16 is a block diagram showing an example of a conventional servo control device.

[Explanation of symbols]

 1 Input Device 2 Target Speed Generator 3 Accelerometer 4 Comparator 5 Inter-Axis Coordinator 6 Speed Converter 7 Buffer 8 Stop Signal Generator 9 Subtractor 10 Compensator 11 Motor 12 Allowable Value Control Circuit

Claims (7)

[Claims] 1. A servo control device for causing a movement path of a controlled object to follow a target path, a plurality of motors connected to a plurality of axes for driving the controlled object, and the plurality of axes based on the target path. Target speed generating means for generating, for each axis, a speed target value representing the target drive speed of the plurality of motors driving each, and provided for each axis, from the speed target value from the target speed generating means An acceleration detecting means for detecting an acceleration target value; a first signal indicating a ratio of the acceleration target value detected by the acceleration detecting means to an allowable value of a predetermined acceleration;
A means for generating a second signal indicating a ratio of the speed target value to an allowable value of a predetermined speed; and comparing the magnitudes of the first signal and the second signal with each other, Inter-axis coordinating means for calculating a time-direction change amount common to each motor so as to satisfy the allowable value of the speed and the allowable value of the speed, and the controlled object moves when the motor is driven at the speed target value. Speed conversion means for changing the speed target value according to the time direction change amount so as to move by the same distance as the distance and generating the speed signal, and at the same time changing the time at which the speed signal is generated. Servo control device. 2. The servo control device according to claim 1, wherein the target speed generating means sequentially generates the speed target value as a sample value. 3. The acceleration detecting means generates an acceleration target value according to a difference between the speed target value and a speed signal from the speed converting means with respect to the speed target value one sample before. The servo control device according to claim 2. 4. The first and second signal generating means outputs an over-acceleration signal indicating the degree to which the acceleration target value exceeds when the acceleration target value exceeds the allowable value of the acceleration, or "1" when the acceleration target value does not exceed the allowable value of the acceleration. Generating a signal as said first signal,
When the speed target value exceeds the allowable value of the speed, an overspeed signal indicating the degree of the speed is exceeded, and when the speed target value does not exceed the allowable value of the speed,
2. The servo controller according to claim 1, wherein a 1 "signal is generated as the second signal. 5. The inter-axis coordinating means detects a maximum value from the first signal and the second signal, and outputs the maximum value signal as the temporal change amount. The servo control device according to claim 1. 6. The servo control device according to claim 1, further comprising an allowable value control means for changing at least one of the allowable value of the acceleration and the allowable value of the speed in accordance with the fluctuation of the load of the controlled object. Servo control device. 7. The servo control device according to claim 1, wherein the target speed generating means includes means for generating an allowable value of the acceleration and an allowable value of the speed.