JPH06165554A - Method and system for contant speed control of motor - Google Patents

Abstract

PURPOSE:To provide a constant speed controller for motor in which fluctuation of rotational speed due to abrupt variation of load can be suppressed. CONSTITUTION:Constant speed control system for feeding back actual rotational speed of motor comprises a load variation predictive position detecting means 10 for detecting a specific position predictive of abrupt variation of load 2 as a load variation predictive position, and an operating amount correcting means 11 for detecting temporal variation of actual rotational speed every time when a load variation predictive position is detected and forcibly varying the operating amount, by an amount corresponding to a predicted variation of the load, in the direction for suppressing fluctuation of rotational speed due to variation of load when a predicted variation of load is detected from the temporal variation of actual rotational speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant speed control method for controlling the rotation speed of an electric motor so as to keep it at a set rotation speed, and a constant speed control device used for implementing the method.

[0002]

2. Description of the Related Art FIG. 3 shows the configuration of a conventional constant speed control device for an electric motor. In FIG. 3, 1 is an electric motor to be controlled, 2 is a load driven by the electric motor 1, and 3 is an electric motor 1. It is a rotation sensor that detects rotation. The illustrated rotation sensor 3 is composed of a rotary encoder and generates a pulse signal every time the output shaft of the electric motor rotates by a predetermined angle. Reference numeral 4 denotes a speed detecting means, which samples the output of the rotation sensor 3 at regular time intervals and detects a pulse output from the rotation sensor within a constant time by detecting the rotational speed of the electric motor. Output as a signal.

Reference numeral 5 is a speed setting means for outputting a speed setting signal containing information on the set rotation speed of the electric motor, and 6 is deviation detecting means for inputting the rotation speed detection signal and the speed setting signal. The actual rotation speed of the electric motor obtained from the rotation speed detection signal output by the speed detection means 4 and the set rotation speed obtained from the speed setting signal generated by the speed setting means 5 are compared to determine the actual rotation speed and the set rotation speed. Detect the deviation of.

For example, as shown in FIG. 4B, the rotation speed detection signal output from the speed detection means 4 is a rectangular wave pulse whose pulse generation interval Tx is inversely proportional to the rotation speed of the motor. The speed setting signal generated by 5 is shown in Fig. 4.
As shown in (A), the pulse generation interval Ts is a rectangular-wave-shaped reference pulse that is inversely proportional to the set rotation speed. The deviation detecting means 6 compares the pulse generation intervals Tx and Ts, for example, and detects the deviation between the actual rotation speed and the set rotation speed from the difference between Tx and Ts.

Reference numeral 7 is a manipulated variable calculating means, 8 is a motor driving section, and the manipulated variable calculating means 7 performs predetermined proportional, integral, and derivative calculations (PID calculation) with the deviation detected by the deviation detecting means as an input. As a result, an amount corresponding to the drive current that needs to be passed through the electric motor 1 to reduce the deviation to zero is calculated as the manipulated variable. The illustrated electric motor drive unit 8 is composed of a pulse width modulation signal generation means 8a and a drive current control means 8b provided with a switch means such as a transistor for turning on / off the drive current of the electric motor 1. The pulse width modulation signal generating means 8a generates a pulse signal whose pulse width is modulated by the operation amount given from the operation amount calculating means 7,
The drive current control means 8b turns on and off the switch means by this pulse signal and supplies a drive current corresponding to the calculated operation amount to the electric motor. As a result, the deviation between the actual rotation speed of the electric motor and the set rotation speed is controlled to approach zero.

[0006]

In the conventional constant speed control device, when the constant of the control system is set so as to reduce the fluctuation of the rotation speed with respect to the relatively slow load fluctuation at the steady time, If a load change more abruptly than the load change occurs, the control system cannot follow the abrupt change of the load, and there is a problem that the fluctuation range of the rotation speed increases with respect to the abrupt load change.

For example, if the load driven by the electric motor is
If it is predicted that the load will change abruptly at a specific position in the process of displacement as the motor rotates, adjust the control system constants so that the load changes relatively slowly. If it is set, there is a problem that the fluctuation range of the rotation speed becomes large when the load suddenly changes at a specific position.

In this case, it is conceivable to set the constant of the control system to increase the sensitivity of the control system so that it can follow a sudden load change. It was unavoidable that the rotation speed of the electric motor became unstable due to the large fluctuation range of the rotation speed with respect to the load fluctuation.

An object of the present invention is to implement a constant speed control method for a motor and a method for controlling the constant speed of a motor capable of suppressing the fluctuation of the rotation speed due to a sudden change of the load without increasing the fluctuation of the rotation speed in a steady state. It is to provide a constant speed control device to be used.

[0010]

Generally, a sudden change in load does not suddenly occur at an arbitrary position, but a position and a load change in which a sudden change in load is predicted to occur due to the structure of the load, the characteristics of the load, etc. The width is usually known in advance. In the present invention, paying attention to this point, the conventional feedback control is performed in the steady state, and it is detected whether or not the predicted load fluctuation occurs at the position where the sudden change of the load is predicted, and the actual feedback control is performed. When it is detected that a load change has occurred, the predictive control is performed to correct the operation amount by a predetermined amount based on the load change predicted directly, so that the change in the rotation speed with respect to the sudden change in the load is changed. It is something that we try to suppress.

That is, the constant speed control method according to the present invention is
Detects the actual rotation speed of the electric motor that drives a load where a sudden change is predicted at a specific position during the displacement process, and controls the drive current of the electric motor so that the deviation between the actual rotation speed and the set rotation speed becomes zero. In the present invention, a specific position where a sudden change in load is predicted is detected as a load fluctuation prediction position, and whether or not the predicted load fluctuation occurs every time the load fluctuation prediction position is detected. When it is detected that the predicted load fluctuation has occurred, the drive current of the electric motor is immediately forced to suppress the fluctuation of the rotation speed due to the load fluctuation by an amount suitable for the predicted load fluctuation. Change.

A constant speed control device according to the present invention is a constant speed control device for an electric motor for controlling a rotation speed of a motor for driving a load, which is expected to change abruptly at a specific position in a displacement process, so as to maintain the rotation speed at a set rotation speed. Is.

According to the present invention, the output of the rotation sensor for detecting the rotation of the electric motor is sampled at regular intervals to generate a rotational speed detection signal containing information on the actual rotational speed of the electric motor, and the setting of the electric motor. A speed setting means for generating a speed setting signal including information on the rotation speed, an actual rotation speed obtained from the rotation speed detection signal and a set rotation speed obtained from the speed setting signal are compared to set the actual rotation speed and the actual rotation speed. Deviation detecting means for detecting a deviation from the rotation speed, operation amount calculating means for calculating an operation amount corresponding to a drive current required to flow to the electric motor in order to reduce the deviation to zero, and an electric motor according to the operation amount. A motor drive section that supplies a drive current to the load, a load fluctuation predicted position detection unit that detects a specific position where a sudden change in load is predicted as a load fluctuation predicted position, and a load fluctuation predicted position every time the load fluctuation predicted position is detected. When detecting a temporal change in the actual rotation speed and detecting that a load fluctuation predicted from the temporal change in the actual rotation speed is detected, the operation is performed in a direction to suppress the fluctuation in the rotation speed caused by the load fluctuation. An operation amount correction means for forcibly changing the amount by an amount that is predicted and adapted to the fluctuation range of the load is provided.

[0014]

As described above, when constant speed control is performed by controlling the drive current of the electric motor so as to make the deviation between the actual rotation speed and the set rotation speed zero, a specific position where a sudden change in load is predicted. Is detected as the load fluctuation predicted position, and each time the load fluctuation predicted position is detected, it is detected whether or not the predicted load fluctuation has occurred, and it is detected that the predicted load fluctuation has occurred. If the drive current of the motor is forcibly changed in the direction of suppressing the fluctuation of the rotation speed due to the load fluctuation when the load fluctuates, an appropriate amount of the drive current can be suppressed in the direction of suppressing the fluctuation of the rotation speed when the load suddenly changes. Therefore, when the load suddenly changes, it is possible to suppress the fluctuation before the fluctuation of the rotation speed becomes large. Therefore, the fluctuation range of the rotation speed when the load changes suddenly can be reduced.

Since the conventional feedback control is performed in the steady state, the fluctuation range of the rotation speed with respect to the load variation in the steady state does not increase.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. In FIG. 1, 1 is an electric motor to be controlled and 2 is a predetermined position which is known to be suddenly heavy or light. There is a load on the motor. Reference numeral 3 is a rotation sensor that detects the rotation of the electric motor 1, and 4 is a rotation speed that includes the information of the actual rotation speed of the electric motor, and outputs the pulse of the rotation sensor 3 within a fixed time by sampling the output of the rotation sensor 3 at fixed time intervals. The speed detecting means 5 for outputting as a detection signal, 5 is a speed setting means for outputting a speed setting signal including information on the setting rotational speed of the electric motor, and 6 is the actual speed of the electric motor detected by the rotational speed detecting signal obtained from the speed detecting means 4. Deviation detecting means for comparing the rotational speed and the set rotational speed obtained from the speed setting signal generated by the speed setting means 5 to detect the deviation between the actual rotational speed and the set rotational speed, and 7 for making the deviation zero 3 is a manipulated variable calculating means for calculating a manipulated variable corresponding to a driving current required to flow to the electric motor, and 8 is a motor driving unit for supplying a driving current to the electric motor according to the manipulated variable. It is configured similarly to the conventional apparatus.

In the present embodiment, in addition to the configuration shown in FIG. 3, a position detector 9 for detecting that the position of the load 2 has reached a set reference position, and a position detector 9 are set. Load fluctuation prediction for detecting a specific position where a sudden change in load is predicted by counting the number of pulses output from the rotation sensor (rotary encoder in this example) from the time when the position is detected Each time the position detection means 10 and the load fluctuation predicted position are detected, a temporal change in the actual rotation speed is detected, and it is detected that the predicted load fluctuation occurs from the temporal change in the actual rotation speed. The operation amount correction means 11 is provided for forcibly changing the operation amount by an amount suitable for the predicted fluctuation range of the load in the direction of suppressing the fluctuation of the rotation speed caused by the load fluctuation.

The position detector 9 detects that the movable part of the load has reached a predetermined reference position. When the movable part of the load is detected to have reached a predetermined position, an electric signal is sent. Any configuration may be used as long as it can generate. This position detector can be composed of, for example, a magnet attached to the movable portion of the load and a magnetic detector which is provided at a fixed position and generates a position detection signal when facing the magnet. This position detector can also be configured by a protrusion provided on the movable portion of the load and a limit switch that operates when the protrusion comes into contact.

Here, as shown in FIG. 2A, the reference position of the movable portion of the load detected by the position detector 9 is O,
When the movable part of the load reaches a specific position L1, a sudden load change to the heavy load side occurs as shown in FIG.
It is assumed that a sudden load change to the light load side occurs at the specific position L2, and the load suddenly returns to the steady-state magnitude (a change to the heavy load side occurs) at the specific position L3.

The load fluctuation predicted position detection means 10 detects the time t0 at which the position detector 9 generates a position detection signal at the reference position O.
At time t, when counting of the pulses generated by the rotation sensor 3 is started at a constant rotation angle and the load is predicted to suddenly change from the count value, the time t reaches L1, L2, L3.
Detect 1, t2 and t3 respectively.

The load fluctuation predicted position detecting means 10 detects the time t1.
When the position L1 at which a sudden change in the load to the heavy load side is predicted is detected, the manipulated variable correcting unit 11 detects a temporal change in the actual rotation speed of the electric motor detected by the speed detecting unit 4. This temporal change in the actual rotation speed can be detected by taking the difference between the current actual rotation speed sampling value and the previous actual rotation speed sampling value. Also, when the load becomes heavy, the actual rotation speed decreases, and when the load becomes light, the actual rotation speed rises. Therefore, the load change is a change to the heavy load side or a change to the light load side. It can be known from the polarity of the temporal change of the actual rotation speed.

In the present embodiment, when the position L1 at which a sudden change in the load to the heavy load side is predicted is detected at time t1, the sampling value of the actual rotation speed is taken in and the current rotation speed The difference between the sampled value and the previous sampled value is calculated, and the current sampled value is lower than the previous sampled value a predetermined number of times (several times)
When it is detected, it is detected that a load change to the heavy load side has occurred at the load change predicted position L1. When it is detected that the load fluctuation to the heavy load side occurs at the load fluctuation predicted position L1, the predicted load is changed in the direction of suppressing the decrease of the rotation speed due to the load fluctuation (in the direction of increasing the rotation speed). The amount of operation given to the electric motor drive unit 8 is forcibly changed by an amount commensurate with the fluctuation range (the drive current of the electric motor is increased). As a result, the speed of the electric motor is increased and the decrease in the rotation speed is suppressed. When it is detected from the comparison between the current sampling value of the actual rotation speed and the previous sampling value, when it is detected that the rotation speed has stopped decreasing, the change of the operation amount is canceled and the control is shifted to the steady state.

When the position L2 at which the load is predicted to be suddenly lightened is detected at time t2, it is determined that the current sampling value of the actual rotation speed is larger than the previous sampling value a predetermined number of times. If detected,
It is detected that a load change to the light load side has occurred, and at this time, the operation amount given to the electric motor drive unit 8 is changed in the direction of suppressing the rotation speed of the electric motor by an amount suitable for the predicted load change. This suppresses an increase in the actual rotation speed of the electric motor and suppresses speed fluctuations. When it is detected from the comparison between the current sampling value of the actual rotation speed and the previous sampling value, when it is detected that the rotation speed has stopped increasing, the change of the operation amount is canceled and the control is shifted to the steady state.

When a reversible motor is used as the electric motor, when the predicted fluctuation range of the load to the light load side is large and a large increase in the rotation speed is predicted, the electric motor is temporarily reversed. It is also possible to apply a directional drive current to brake the electric motor.

At time t3, the specific position L3 is detected, and when it is detected that the load change to the heavy load side occurs from the temporal change of the actual rotation speed, immediately in the direction of increasing the speed of the electric motor. Correct the operation amount to suppress the decrease in rotation speed and suppress speed fluctuations. When it is detected from the comparison between the current sampling value of the actual rotation speed and the previous sampling value, when it is detected that the rotation speed has stopped decreasing, the change of the operation amount is canceled and the control is shifted to the steady state.

When a sudden change in load occurs as shown in FIG. 2D, when only conventional feedback control is performed, as shown in FIG. 2B, when the load suddenly changes. It is inevitable that the rotation speed will change significantly. On the other hand, when the predictive control is also used as in the above embodiment, as shown in FIG. 2C, the fluctuation range of the rotation speed with respect to the sudden change of the load can be reduced and the rotation of the electric motor can be stabilized. Can be

In the above embodiment, the reference position of the load is detected by the position detector, and the output pulse (position detection pulse) of the rotation sensor is counted from this reference position,
Although each position where a sudden change in load is predicted is detected as a load fluctuation prediction position, a position detector is placed at each load fluctuation prediction position and each load fluctuation prediction position is directly detected by each position detector. You may do it.

In the above embodiment, the manipulated variable correcting means 11
Can be configured to forcibly correct the operation amount given to the motor drive unit when the predicted load change position is detected and when the actual load change is detected. The method is arbitrary. For example, the operation amount may be corrected by adding or subtracting a correction amount to the operation amount calculated by the operation amount calculating means 7, or by changing the constant of the PID calculation in the operation amount calculating means,
The operation amount may be corrected.

The deviation detecting means 6, the manipulated variable calculating means 7, and the manipulated variable correcting means 11 may be constituted by an analog arithmetic circuit, or may be realized by operating a microcomputer by a predetermined program. Good.

In the above embodiment, the speed setting means 5 generates the pulse-shaped reference signal, but when the deviation detecting means 6 and the operation amount calculating means 7 are realized by a computer, the CPU sets the rotation speed. The speed setting means can be configured by a circuit that digitally gives.

In the above embodiment, the position detector 9 is provided. However, when the rotation sensor 3 that can detect the absolute position of the output shaft of the electric motor or the load is used, the output of the rotation sensor is used. Since each position of the load can be detected, it is not necessary to provide the position detector 9.

[0032]

As described above, according to the present invention, when the constant speed control is performed by controlling the drive current of the electric motor so that the deviation between the actual rotation speed and the set rotation speed becomes zero, the load is reduced. A specific position where a sudden change is predicted is detected as the load change prediction position, and each time the load change prediction position is detected, it is detected whether or not the predicted load change has occurred. When it is detected that it is occurring, the drive current of the electric motor is forcibly changed so as to suppress the fluctuation of the rotation speed due to the load fluctuation. Therefore, the direction of suppressing the fluctuation of the rotation speed when the load suddenly changes. The drive current can be quickly changed by an appropriate amount, and when the load changes suddenly, the fluctuation is suppressed before the fluctuation of the rotation speed becomes large, and the fluctuation range of the rotation speed when the load suddenly changes can be suppressed. Can be made smaller. Further, since the conventional feedback control is performed in the steady state, the fluctuation range of the rotation speed with respect to the load variation in the steady state does not increase.

Therefore, according to the present invention, there is an advantage that it is possible to suppress the speed fluctuation when the load suddenly changes, without affecting the speed fluctuation rate in the steady state.

[Brief description of drawings]

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

2A to 2D are diagrams for explaining the operation of the embodiment of FIG.

FIG. 3 is a block diagram showing a configuration of a conventional constant speed control device.

4A and 4B are waveform charts for explaining the operation of the deviation detecting means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric motor 2 Load 3 Rotation sensor 4 Speed detection means 5 Speed setting means 6 Deviation detection means 7 Manipulation amount calculation means 8 Electric motor drive section 9 Position detector 10 Load fluctuation predicted position detection means 11 Operation amount correction means

Claims (2)

[Claims] 1. An actual rotation speed of a motor for driving a load in which a sudden change is predicted at a specific position in the course of displacement is detected, and a difference between the actual rotation speed and a set rotation speed is set to zero. In a constant speed control method of a motor for controlling a drive current, a specific position where a sudden change in the load is predicted is detected as a load change predicted position, and a predicted load change occurs every time the load change predicted position is detected. If it is detected that the predicted load fluctuation is occurring, the drive current of the electric motor is set to the predicted load fluctuation range in the direction of suppressing the fluctuation of the rotation speed due to the load fluctuation. A constant speed control method for an electric motor, which is characterized by forcibly changing an appropriate amount. 2. A constant speed control device for an electric motor for controlling a rotational speed of an electric motor for driving a load for which a sudden change is predicted at a specific position during a displacement process so as to maintain the rotational speed at a set rotational speed, the rotation of the electric motor is detected. The output of the rotation sensor is sampled at regular intervals to generate a rotation speed detection signal including information on the actual rotation speed of the electric motor, and a speed setting signal including information on the setting rotation speed of the electric motor is generated. Comparing the speed setting means, the actual rotation speed obtained from the rotation speed detection signal and the set rotation speed obtained from the speed setting signal,
Deviation detecting means for detecting a deviation between the set rotation speed and the actual rotation speed, and an operation amount calculating means for calculating an amount corresponding to a drive current required to flow to the electric motor as an operation amount in order to reduce the deviation to zero. An electric motor drive unit that supplies a drive current to the electric motor according to the operation amount, a load fluctuation prediction position detection unit that detects a specific position where a sudden change in the load is predicted as a load fluctuation prediction position, and the load fluctuation prediction position Whenever it is detected that the load fluctuation predicted from the temporal change of the actual rotation speed occurs, the change in the actual rotation speed is detected. A constant speed control device for an electric motor, comprising: a manipulated variable correcting unit for forcibly changing the manipulated variable by an amount suitable for a predicted fluctuation range of the load in a direction of suppressing fluctuation of the rotation speed.