JPH10234195A - Method and apparatus for speed control of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for the speed control of a motor, with which a good control characteristic can be made both in a starting operation and in steady operation. SOLUTION: An operating-state adjustment means 4F and a gain-constant changeover means 4G, which changes over a gain constant used for a computing operation by a PID computing part 4D, according to an operating state judged by the operating-state judgment means 4F are installed at a controller 4 which controls a drive circuit 5, giving a driven signal to a transistor at an inverter circuit 2 which makes an exciting current flow to armature coils 1u, 1v, 1w of a motor 1. When the operating state is judged to be a transient operating state by the operating-state judgment means 4F, a gain constant is set to a value which is suitable for a starting operation, and when the operation state is judged to be a steady operating state, the gain constant is set to a value which is suitable for a steady operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In a case where a motor is controlled so as to keep its rotation speed at a target rotation speed, in many cases, an operation mode from the start of starting the motor until the rotation speed reaches a set value is a start mode. In the starting mode, an exciting current suitable for starting is supplied to the armature coil, and the constant speed control mode is started when the rotation speed reaches a set value. In the constant speed control mode, the difference between the rotation speed of the electric motor and the target rotation speed is detected, and the magnitude of the excitation current necessary to make the difference zero is calculated by performing a proportional, integral and differential operation on the difference. The control is performed so that the rotation speed is maintained at the target rotation speed by flowing the excitation current of the calculated magnitude to the armature coil of the motor.

A motor has an n-phase (n is an integer of 2 or more) armature coil, and a rotor is rotated by commutating an exciting current (armature current) to the n-phase armature coil. In such a case, an inverter circuit is used to commutate the exciting current.

For example, a brushless DC motor includes a stator having an n-phase armature coil, a rotor having a field made of a permanent magnet, and a position sensor for detecting a rotational angle position of the rotor. Then, the rotor is rotated by commutating the exciting current from the DC power supply to the n-phase armature coil in accordance with the rotational angle position of the rotor.

[0005] A speed control device for controlling the rotation speed of the brushless DC motor so as to maintain the rotation speed at a set speed includes an inverter circuit having a switching element for switching an excitation current flowing through an armature coil of each phase; A phase pattern signal generating section for generating a phase pattern signal indicating an excited phase and a non-excited phase of the armature coil according to the position, a speed setting section for providing a target rotation speed of the motor, and detecting an actual rotation speed of the motor A speed detection unit, a speed deviation detection unit that detects a deviation between the target rotation speed given by the speed setting unit and the actual rotation speed detected by the speed detection unit, and the actual rotation speed after the motor starts to start. A period until the set value is reached is set as a start-up period, and a period after the start-up period elapses is set as a constant speed control period. After entering the constant speed control period, it is necessary to perform a proportional, integral and differential operation on the deviation detected by the speed deviation detection unit using a predetermined gain constant to make the deviation zero. A PID calculation unit for calculating the magnitude of the exciting current of the armature coil to calculate the magnitude of the exciting current,
A PWM signal generating unit for generating a PWM signal that is intermittent with a duty required for performing WM modulation to obtain the magnitude given by the PID calculation unit; an excitation phase based on the phase pattern signal with the phase pattern signal and the PWM signal as inputs; And a drive circuit that supplies a drive signal to a switching element that constitutes an inverter circuit so that an excitation current modulated by the PWM signal flows through the armature coil of the selected phase.

When a motor controlled by such a speed control device is started, a predetermined starting current is applied to the armature coil until the rotation speed reaches a set value after the start of the motor. ), The rotation speed N
Is raised. When the rotation speed reaches the set value No at time t1, the constant speed control is started, and the exciting current is adjusted so that the deviation between the actual rotation speed of the motor and the target rotation speed becomes zero.
Control is performed so that the actual rotation speed N matches the target rotation speed Ns. Immediately after the start of the constant speed control, since the rotation speed Ns has not yet reached the target rotation speed, the rotation speed of the motor increases toward the target rotation speed Ns, but eventually converges on the target rotation speed Ns. .

[0007]

In the conventional speed control device, the gain constant used for the PID calculation is constant in the entire region where the constant speed control is performed. However, if the gain constant is set so as to improve the controllability in a steady operation state after the rotation speed of the electric motor is settled at the target rotation speed,
As shown in FIG. 3A, after the constant speed control is started,
When the rotation speed is set to the target rotation speed, the rotation speed fluctuates due to the vibration generated in the control system, and the control characteristics become the characteristic of the vibration, and it takes a long time for the rotation speed to settle to the target rotation speed. Problems arise. On the other hand, if the control is strengthened by increasing the gain constant in order to suppress the vibration when the rotation speed is set to the target rotation speed, the gain constant becomes too large during the steady operation after the settling.
As shown in (1), the control characteristics at the time of steady operation become almost full of oscillation, and the controllability of the rotational speed is deteriorated.

[0008] As described above, in the conventional speed control device, if the controllability during the steady operation is improved, the setting of the rotation speed at the time of starting is deteriorated, and conversely, the setting of the rotation speed at the time of starting is improved. In this case, there is a problem that controllability during steady operation is deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a speed control method and a speed control device for a motor which can improve both the stabilization of the rotational speed at the time of starting and the controllability at the time of steady operation. is there.

[0010]

According to the speed control method of the present invention, after the motor is started, the constant speed control mode is started when the rotation speed of the motor reaches a set value.
In the constant speed control mode, the magnitude of the exciting current required to make the deviation zero by detecting the deviation between the rotation speed of the electric motor and the target rotation speed and performing an operation on the deviation,
The control is performed so that the rotation speed of the motor is maintained at the target rotation speed by flowing the exciting current of the determined magnitude through the armature coil of the motor.

In the present invention, a state until the set time elapses after the start of the constant speed control mode is defined as a transient operation state, and in the transient operation state, a gain constant used for calculation is set to a value suitable for startup. The state after a set time has elapsed after the start of the constant speed control mode is defined as a steady operation state. In the steady operation state, the gain constant used for the calculation is set to a value suitable for the steady operation.

A speed control device to which the present invention is directed is an inverter circuit having a switching element for switching an exciting current flowing through an armature coil of an electric motor, a speed setting unit for providing a target rotation speed of the electric motor, and an actual motor of the electric motor. A speed detection unit for detecting the rotation speed, a speed deviation detection unit for detecting a deviation between the target rotation speed given by the speed setting unit and the actual rotation speed detected by the speed detection unit, and the motor starts to start. From the time until the actual rotation speed reaches the set value as a start period, the period after the start period elapses as a constant speed control period, and during the start period, the excitation current suitable for starting is given. After entering the constant speed control period,
The magnitude of the excitation current required to reduce the deviation to zero is calculated by applying an arithmetic operation to the deviation detected by the speed deviation detection unit using a predetermined gain constant. An arithmetic unit for supplying the PWM signal (pulse width modulation) to the excitation current flowing through the armature coil to generate a PWM signal that is intermittently generated at a duty required for obtaining the magnitude given by the arithmetic unit; , The P
And a drive circuit for supplying a drive signal to a switching element forming an inverter circuit so that an exciting current modulated by the WM signal flows through the armature coil.

According to the present invention, there are provided operating state determining means for determining the operating state of the motor, and gain constant switching means for switching a gain constant in accordance with the determination result of the operating state determining means.

The operating state determining means determines a state from a point in time when the constant speed control period starts to a point in time when the set time elapses as a transient operation state. The state after the elapse of the elapsed time is determined as a steady operation state.

The gain-constant switching means sets a gain constant used for calculation in the calculation unit to a value suitable for starting when the operating state is determined to be in a transient operation state by the operating-state determining means. When the operating state is determined to be in the steady operation state, the gain constant used for the calculation in the calculation unit is determined according to the determination result by the operating state determination means so that the gain constant used for the calculation becomes a value suitable for the steady operation. Switch.

As described above, the transient operation state and the steady operation state of the electric motor are determined based on the elapsed time from the start of the constant speed control, and the calculation in the arithmetic unit is performed according to the determined operation state. By switching the gain constant to be used, the gain constant can be set to an optimum value in each operation state, so that both the settling property of the rotation speed at the start and the controllability of the rotation speed during the steady operation are improved. be able to.

[0017]

1 shows an example of the configuration of a speed control device according to the present invention. In FIG. 1, reference numeral 1 denotes a stator having three-phase armature coils 1u, 1v and 1w, and a permanent magnet. A brushless DC motor comprising a rotor (not shown) having a field formed by a brushless DC motor, and an inverter 2 having a switching element for switching an exciting current flowing through the three-phase armature coils 1u to 1w of the brushless DC motor 1. The circuit 3 is a rotary encoder RE built in the motor 1.
The speed detector 4 detects the rotation speed of the motor from the output of the motor and outputs a speed detection signal. The microcomputer 4 uses a microcomputer to detect the speed detection signal obtained from the speed detector 3 and the rotation angle position of the rotor of the motor. A controller that generates a signal for controlling the inverter circuit 2 using the output of the position sensor PS as an input, 5 is a drive circuit that supplies a drive signal to the inverter circuit 2 according to a signal given from the controller 4, and 6 is a drive circuit of the motor 1. It is a load.

The respective parts will be described in more detail. In the inverter circuit 2, the PNP transistors TRu, TRv and TRw whose emitters are commonly connected, and the collectors of the transistors TRu to TRw are connected to each other, and the emitters are grounded. NPN transistor TR
x, TRy and TRz and transistors TRu to TRw
Between the emitters and collectors of the transistors TRx to TRz, the cathodes of which are connected in parallel with the cathodes facing the emitters of the transistors TRu to TRw, and the cathodes of the transistors TRx to TRz are connected between the collectors and emitters of the transistors TRx to TRz. And feedback diodes Dx to Dz connected in parallel in a state facing the collector side. In the illustrated example, the transistors TRu to TRw
, And TRx to TRz respectively constitute a switch element on the upper side and a switch element on the lower side of the bridge, and these switch elements are connected in a three-phase bridge to form a three-phase inverter circuit. Also, transistors TRu ~
Feedback diodes Du to Dw and Dx to Dz connected in parallel to TRw and TRx to TRz, respectively, are connected in a three-phase bridge, and these diodes constitute a three-phase full-wave rectifier circuit. In this inverter circuit, the common connection point of the emitters of the transistors TRu to TRw and the common connection point of the emitters of the transistors TRx to TRZ become the power supply terminal 2a on the positive polarity side and the power supply terminal 2b on the negative polarity side (earth side), respectively. The power terminals 2a and 2b are connected to a positive output terminal and a negative output terminal of a DC power supply (not shown), respectively.

The rotary encoder RE is a known encoder that generates a pulse signal every time the rotor of the electric motor 1 rotates by a small angle. The speed detection unit 3 is configured by, for example, a frequency-voltage conversion circuit that converts the frequency of a pulse signal output from the rotary encoder RE into a voltage signal, and uses a voltage signal having a magnitude proportional to the rotation speed of the motor as a speed detection signal. Output.

The controller 4 includes a phase pattern signal generator 4A for generating a phase pattern signal indicating an exciting phase (a phase in which an exciting current flows) and a non-exciting phase (a phase in which no exciting current flows) of the motor; Speed setting unit 4 for giving target rotation speed
B, a speed deviation detection unit 4C for detecting a deviation between the target rotation speed and the actual rotation speed, a PID calculation unit 4D for giving the magnitude of the exciting current flowing through the armature coils 1u to 1w, and the armature coils 1u to 1w. PWM modulates the exciting current flowing through
A PWM signal generation unit 4E for generating a PWM signal that is intermittently provided with a duty required to obtain the magnitude given by the calculation unit 4D.

The phase pattern signal generating section 4A outputs a phase pattern signal indicating the excited phase and the non-excited phase of the armature coils 1u to 1w according to the output of the position sensor PS for detecting the rotational angle position of the rotor of the motor. This is the part that occurs. The phase pattern signal generator 4A includes transistors (switching elements) TRu-TRw and TRx-T of the inverter circuit 2.
Output terminals 2u to 2w and 2x to
2z, and of these output terminals, the potential of the output terminal corresponding to the transistor to be turned on and the potential of the output terminal corresponding to the transistor to be turned off are made different, so that the armature coil A phase pattern signal indicating an excited phase and a non-excited phase is output. As shown, in the case of a brushless DC motor having armature coils 1 u to 1 w of U to W three phases, the excitation phase is changed as the rotor rotates.
For example, (U phase, Y phase) → (U phase, Z phase) → (V phase, Z phase)
Phase) → (V phase, X phase) → (W phase, X phase) → (W phase, Y phase
Phase) → (U phase, Y phase)...
In this case, for example, the output terminal 2 of the phase pattern signal generation unit
The state in which the potentials of u to 2w and 2x to 2w are high is “1”, the state of low level (ground potential) is “0”, and the state of the output terminal corresponding to the switching element to be turned on is “1”. ", The output terminal (2
u, 2v, 2w, 2x, 2y, 2z), the phase pattern signal is (1, 0, 0, 0, 1, 0) → (1, 0,
0,1,0,0) → (0,1,0,1,0,0) →
(0,1,0,0,0,1) → (0,0,1,0,0,
1) → (0,0,1,0,1,0) → (1,0,0,
0, 1, 0),.

The speed setting section 4B is a section for giving a target rotation speed of the electric motor 1. The speed setting section 4B detects, for example, a displacement amount of a speed adjustment member and generates a voltage signal indicating the target rotation speed. It can be composed of a position sensor and an A / D converter that converts the voltage signal into a digital signal.

The speed deviation detecting section 4C detects a deviation e between the target rotational speed given by the speed setting section 4B and the actual rotational speed detected by the speed detecting section 3, and is provided in the microcontroller 4 provided in the controller 4. This is realized by causing a computer to execute a program for calculating a difference between the target rotation speed and the actual rotation speed.

The PID calculation section 4D sets the period from the start of the start of the motor to the time when the actual rotation speed reaches the set value as the start period, and sets the period after the start period as the constant speed control period as the start period. During the period, a suitable magnitude of the exciting current is applied at the time of startup, and after entering the constant speed control period, proportional, integral, and differential operations are performed using a predetermined gain constant for the deviation e detected by the speed deviation detection unit. To obtain the deviation e
Calculate the magnitude of the exciting current necessary to make the value zero.

The deviation between the target rotation speed and the actual rotation speed is represented by e,
Assuming that the time is t, the PID calculation unit 4D obtains the magnitude of the exciting current i flowing through the armature coils 1u to 1w, for example, by performing the following calculation.

I = K 1 e + K 2 ∫edt + K 3 (de / dt) (1) where K 1, K 2 and K 3 are gain constants of a proportional term, an integral term and a differential term, respectively.

The PWM signal generating section 4E performs PWM modulation of the exciting current flowing through the armature coil to obtain the magnitude given by the arithmetic section 4D.
Generate a WM signal.

The drive circuit 5 has input terminals connected to the output terminals 2u to 2w and 2x to 2z of the phase pattern signal generator, an input terminal to which a PWM signal is input, and transistors (switching elements) TRu to TRw. And TR
It has output terminals 5u to 5w and 5x to 5z connected to respective bases (drive signal input terminals of the switching elements) of x to TRz, and a predetermined transistor of the inverter circuit performs PWM control according to the phase pattern signal. A drive signal modulated by a signal (a drive signal that is intermittent at a predetermined duty) is provided. The drive circuit 5 shown in the drawing is configured such that when a signal in a state of “1” is given from the output terminals 2 u to 2 w of the phase pattern signal generation unit, a drive signal in a state of “0” is output from the output terminals 5 u to 5 w (grounded). Level signal) to turn on the transistors TRu to TRw, and when a signal of “0” state is given from each of the output terminals 2u to 2w of the phase pattern signal generation unit, the output terminal 5u is output.
5w output signals (high-level signals) in the state of "1" (turn off the drive signal) to turn off the transistors TRu to TRw. The driving circuit 5 also
When a signal in the state of “1” is given from each of the output terminals 2x to 2z of the phase pattern signal generating unit 2, the drive signal in the state of “1” (high-level state) is output from the output terminals 5x to 5z. To output the transistors TRx to TRz.
Is turned on, and the output terminal 2 of the phase pattern signal
When a signal in a state of "0" is given from x to 2z, a signal in a state of "0" (state of ground level) is output from each of output terminals 5x to 5z (the drive signal is extinguished). ) Turn off the transistors TRx to TRz.

In the inverter circuit 2, the transistor to which the drive signal is supplied from the drive circuit 5 is turned on, and an exciting current flows through the armature coil in the exciting phase. For example, when the U phase and the V phase are the excitation phases and the W phase is the non-excitation phase, the transistors TRu and TRy are turned on, and a DC power supply (not shown) → the transistor TRu → the electronic coil 1u → the armature coil Excitation current flows through the path of 1v → transistor TRy → DC power supply. The phase pattern signal is changed with the change of the rotation angle position of the rotor, and the combination of the upper transistor and the lower transistor that are turned on by the change of the phase pattern signal is sequentially changed. The rotor is rotationally driven by the commutation. Since the drive signal supplied from the drive circuit 5 to each transistor of the inverter circuit is modulated by the PWM signal, the excitation current also has a PWM-modulated waveform, and the magnitude (average value) of the excitation current is determined by the PID operation unit 4D. Is the size calculated by

The phase pattern signal generating section 4A, speed setting section 4B, speed deviation detecting section 4C, PID calculating section 4D, PW
The configurations of the M signal generator 4E and the drive circuit 5 are the same as those used in a conventional control device of this type.

In the present invention, in addition to the above configuration, the controller 4 further includes an operating state determining means 4F realized by a microcomputer and a gain constant switching means 4G.

The operating state determining means 4F is shown in FIG.
As shown in (B), after the motor is started, the state from the time when the rotation speed N reaches the set value No and the constant speed control period is started until the set time T elapses is referred to as a transient operation state. Is a means for determining a state after a set time has elapsed from the time when the constant speed control period is started to be a steady operation state. This operation state determination means 4F uses a timer 4H provided in the microcomputer to
This can be realized by measuring the elapsed time from the start of the constant speed control period. That is, after the motor starts,
When the rotation speed reaches the set value No (when the constant speed control period is started), the timer 4H starts measuring the set time, and the state in which the timer 4H is performing the set time measurement operation is changed to a transient state. The operating state determining means 4F can be realized by causing the microcomputer to perform the processing of determining the operating state and determining the state after the timer finishes measuring the set time as the steady operating state.

The gain constant switching means 4G includes gain constants K1 to K4 which are used when the PID calculation unit 4D performs proportional, integral and differential calculations when the operating state determining means 4F determines that the operating state is in the transient operating state. K3 is set to a value suitable for start-up, and when the operating state is determined by the operating state determining means to be in a steady operation state, the gain constants K1 to K3 are set to values suitable for steady operation by the operating state determining means. The gain constants K1, K2, and K3 used for the operation in the PID operation unit are switched according to the judgment result.

The gain constant switching means 4G stores the values of the gain constants K1 to K3 in the transient operation state and the values of the gain constants K1 to K3 in the steady operation state in the ROM of the microcomputer and determines the determined operation. The value of the predetermined gain constant is read from the ROM according to the state and P
The processing given to the ID operation unit 4D can be configured by adding it to a program executed by a microcomputer to realize each unit of the controller 4.

As described above, the transient operation state and the steady operation state of the motor are determined based on the elapsed time from the start of the constant speed control, and the calculation is performed by the arithmetic unit in accordance with the determined operation state. By switching the gain constant to be used, the gain constant can be set to an optimum value in each operation state, so that both the settling property of the rotation speed at the start and the controllability of the rotation speed during the steady operation are improved. be able to.
For example, if the constant speed control is performed with the gain constant fixed at a value suitable for steady operation, the control characteristic of the rotational speed becomes oscillatory in the transient operation state as shown in FIG. Although it takes time for the rotation speed to settle to the target rotation speed, as in the present invention, if the gain constant switching means 4G is provided to set the gain constant in the transient operation state to a value suitable for startup, FIG. As shown in FIG. 2 (B), the rotational speed can be quickly settled at the target rotational speed while suppressing the vibration of the control characteristics in the transient operation state.

In the above example, the present invention is applied to a three-phase brushless DC motor. However, the present invention can be applied to a two-phase brushless DC motor or a multi-phase brushless DC motor. The present invention can be applied to a case where a motor other than the brushless DC motor is controlled at a constant speed.

In the above example, a transistor is used as a switching element constituting the inverter circuit 2. However, the inverter circuit may be constituted by using another switching element such as an FET capable of on / off control.

In the above example, the magnitude of the exciting current required to make the deviation zero by performing the PID operation on the deviation is calculated. However, the I (integral) operation and the D (differential) operation are performed. The present invention can be applied to a case where at least one is omitted.

[0039]

As described above, according to the present invention, the transient operation state and the steady operation state of the motor are determined based on the elapsed time from the start of the constant speed control, and the determined operation state is set. The gain constant used for the calculation in the calculation unit is switched accordingly, so that the gain constant is set to the optimum value in each of the operation states at the time of start-up and steady-state operation, and the rotational speed at the time of start-up is settled. Both the controllability of the rotational speed during the steady operation and the controllability can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration example of a motor speed control device according to the present invention.

FIG. 2 is a diagram showing a comparison between control characteristics of a conventional speed control device and control characteristics of a speed control device according to the present invention.

FIGS. 3A and 3B are diagrams showing different examples of control characteristics obtained by a conventional speed control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Motor 2 Inverter circuit 3 Speed detection part 4 Controller 4A Phase pattern signal generation part 4B Speed setting part 4C Speed deviation detection part 4D PID calculation part 4E PWM signal generation part 4F Operating state judgment means 4G Gain constant switching means 4H timer

Claims (2)

[Claims] After the motor is started, a constant speed control mode is started when the rotation speed of the motor reaches a set value. In the constant speed control mode, a deviation between the rotation speed of the motor and a target rotation speed is set. By calculating the magnitude of the excitation current required to make the deviation zero by detecting the deviation and calculating the deviation, the excitation current of the determined magnitude is supplied to the armature coil of the electric motor. In the motor speed control method for controlling the rotation speed of the motor to be maintained at a target rotation speed, a state until a set time has elapsed after the constant speed control mode is started is set as a transient operation state, and the transient operation state In the above, the gain constant used for the calculation is set to a value suitable for startup, the state after the set time has elapsed is set to a steady operation state, and in the steady operation state, the gain constant used for the calculation is set for the steady operation. Speed control method for an electric motor, characterized in that the values. 2. An inverter circuit including a switching element for switching an exciting current flowing through an armature coil of an electric motor, a speed setting unit for providing a target rotational speed of the electric motor, and a speed detector for detecting an actual rotational speed of the electric motor. Department and
A speed deviation detection unit that detects a deviation between the target rotation speed given by the speed setting unit and an actual rotation speed detected by the speed detection unit, and the actual rotation speed is set to a set value after the electric motor starts to start. Is a start-up period, a period after the start-up period has elapsed is a constant-speed control period, and during the start-up period, the magnitude of the exciting current suitable for start-up is given. After that, the deviation detected by the speed deviation detection unit is calculated using a predetermined gain constant to calculate the magnitude of the excitation current required to make the deviation zero, thereby calculating the excitation current. An arithmetic unit for giving the magnitude of the current; and a PWM signal for generating a PWM signal intermittently at a duty required to PWM-modulate the exciting current flowing through the armature coil to the magnitude given by the arithmetic unit Speed control of an electric motor, comprising: a raw part; and a drive circuit that supplies a drive signal to a switching element included in the inverter circuit so that an excitation current modulated by the PWM signal flows through the armature coil with the PWM signal as input. In the device, a state until the set time elapses from the time when the constant speed control period is started is determined as a transient operation state, and the set time elapses from the time when the constant speed control period is started. Operating state determining means for determining the state after the operation is a steady operating state; and when the operating state determining means determines that the operating state is in the transient operating state, a gain constant used for the calculation in the calculating unit is activated at the time of startup. When the operating state is determined to be a steady state by the operating state determining means, the gain constant used for the calculation is set to a suitable value. Speed control means for switching a gain constant used for calculation in the calculation unit in accordance with a result of the determination by the operation state determining means so as to obtain a value suitable for a steady operation. apparatus.