JPH05328778A - Inertia estimating device for brushless motor - Google Patents

Abstract

PURPOSE:To stably estimate inertia of a brushless motor without rotating the motor in a predetermined direction in a short time. CONSTITUTION:Switches 58 and 59 are set to shown positions. An instruction unit 56 instructs a torque current command iT' for inhibiting synchronization of a motor 1 and a pole position signal phi' corresponding to an exciting frequency, drives the motor 1 through a vector operator 55 and a power amplifier 4, and then generates a miniature vibration. Two-phase pulses A, B from an encoder 3 generated by the vibration are processed by a pulse processor 6, input to a speed detector 51 and an inertia detector 57, thereby estimating magnitude of the inertia from an amplitude of the vibration of a rotary angular speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-phase brushless motor (hereinafter also simply referred to as a motor) having a permanent magnet as a rotor, and an estimating device for estimating the inertia of a load device connected to the three-phase brushless motor.

[0002]

2. Description of the Related Art Conventionally, as a method of estimating inertia, there is known a method of estimating inertia by giving a constant torque current command to a motor to accelerate or decelerate and measure the acceleration / deceleration time.

[0003]

However, the conventional inertia estimation method has the following problems. (1) Since the rotor must be rotated with a constant torque in a certain direction in order to know the magnitude of the inertia, it cannot be applied to a load that cannot permit the rotation of the rotor other than a normal operation. (2) Since the inertia is completely unknown and the magnitude of the torque current command to be given is unknown, the magnitude of the torque current command is changed several times to accelerate or decelerate the motor, and the inertia is detected by detecting the acceleration / deceleration time. It may be necessary to perform a series of operations for estimating Therefore, an object of the present invention is to make it possible to estimate the inertia by a single operation without rotating the rotor in a fixed direction.

[0004]

In order to solve such a problem, according to the first invention, a three-phase brushless motor comprising a stator winding and a rotor having a permanent magnet is mounted on the rotor shaft. Encoder, counting means for counting the pulses emitted from this encoder, a control device for giving a voltage command or a current command and a frequency command to the motor, and the three-phase brushless motor by amplifying these commands. And a power amplifier for driving the motor, and a predetermined voltage or current command and a predetermined frequency command are given from the control device to the stator winding of the motor through the power amplifier to give a predetermined voltage or current command and a predetermined frequency command. A small vibration of the same frequency generated by alternating current excitation and generated in the rotor as a result is detected through the encoder and the counting means, and a rotation angle acceleration signal or a rotation angle of the small vibration is detected. To detect either the amplitude of the degree signal or the rotational angle signal is characterized by determining the magnitude of inertia based on this.

In the second aspect of the invention, a three-phase brushless motor consisting of a stator winding and a rotor having a permanent magnet, an encoder mounted on the rotor shaft, and a counter for counting the pulses emitted from this encoder. Means, a control device for giving a voltage command or a current command and a frequency command to the motor, a power amplifier for amplifying these commands to drive the three-phase brushless motor, and a timer for measuring time. , A predetermined frequency command and a voltage or current command that gradually increases from zero over time so as to cause the motor to step out of the stator winding of the motor from the control device via a power amplifier; A small vibration whose amplitude is gradually increased at the same frequency generated in the rotor by the phase alternating current excitation is detected through the encoder and the counting means, and the small vibration is detected. The amount of inertia is obtained by measuring the time elapsed by the timer until the amplitude of any of the rotational angular acceleration signal, the rotational angular velocity signal, or the rotational angle signal exceeds a predetermined value. I am trying.

[0006]

The torque generated in the brushless motor is
When the magnetic flux created by the magnetic poles of the rotor and the current flowing through the stator winding are captured as a space vector, the outer product is obtained. Therefore, when three-phase AC excitation is performed with the rotor not rotating, only the current vector rotates, the generated torque is represented as a sine wave function of the excitation frequency, and the generated torque causes the rotor to vibrate. By the way, since the amplitude of this vibration is determined by the magnitude of the current, the excitation frequency and the magnitude of the inertia, three-phase AC excitation is performed at a predetermined current and excitation frequency, and the inertia of the inertia is detected by detecting the amplitude of the vibration at that time. Can be estimated. This will be described below using mathematical expressions.

The relationship between the rotation angle θ and the torque T in the motor is assumed as in the following equation (1). T = J × (d ² θ / dt ² ) J: Inertia [Kg · m ² ] ... (1) Now, when the stator winding is excited by a three-phase alternating current at a certain angular frequency ω, the current (I) vector is the same. If it rotates at an angular frequency and the rotor remains stationary at a certain position at this time,
The generated torque T is given by the equation (2). T = KIsin (ωt) (2) Here, K represents a torque constant [Kg · m / A].

By substituting the equation (1) into the equation (2), the rotational angular acceleration, the rotational angular velocity, and the rotational angle due to the three-phase AC excitation can be obtained, and these are all sinusoidal functions.
Focusing on the amplitude of each function, the rotational angular acceleration A1 (d ² θ / dt ² ) and the rotational angular velocity A 2 (dθ / d
t) and the rotation angle A3 (θ) are as follows (3),
It can be obtained as in equations (4) and (5). Rotational angular acceleration: A1 = (K _T · I) / J (3) Rotational angular velocity: A2 = (K _T · I · ω) / J (4) Rotational angle: A3 = (K _T · I · ω ² ) / J (5) Here, since K _T is a constant and I and ω are predetermined values (setting values), J and these amplitudes A1, A2, and A3 are in inverse proportion to each other. Therefore, the amplitudes A1, A2, A
It is possible to obtain the magnitude of inertia by detecting any one of the three.

Instead of the above, the following is also possible. That is, in three-phase AC excitation, if the current is set to an increasing function I (t) whose magnitude gradually increases from zero over time, the amplitude of vibration in this case is the elapsed time from the start of excitation. , Since it is determined by the function of current, the excitation angular frequency and the magnitude of inertia, if three-phase AC excitation is performed at a predetermined excitation angular frequency and a predetermined current function (increasing function), the amplitude of the resulting microvibration will be reduced. By measuring the time until it becomes a certain value or more, the magnitude of inertia can be estimated by one estimation operation.

That is, the current I is defined as a function I (t) that gradually increases with time, and this is, for example, I (t) =
Considering α · t (α is a positive constant), the amplitude A1 ′ of the rotational angular acceleration, the amplitude A2 ′ of the rotational angular velocity, and the amplitude A3 ′ of the rotational angle are respectively calculated from the equations (3) to (5) below. It can be expressed like an expression. Rotational angular acceleration: A1 ′ = (K _T · α · t) / J (6) Rotational angular velocity: A2 ′ = (K _T · α · ω · t) / J (7) Rotational angle: A3 ′ = ( K _T · α · ω ² · t) / J (8) Since the amplitudes A1 ′, A2 ′ and A3 ′ of the minute vibrations gradually increase over time, until they reach a certain value. Assuming that the time of t0 is t0, this t0 and the magnitude J of the inertia are in a proportional relationship.
By measuring, the magnitude J of inertia can be obtained. Although I (t) is set to I (t) = α · t in the above, the function is not limited to this as long as it is a function that gradually increases with the passage of time, and for example, a quadratic function or an exponential function may be used. There is no end.

[0011]

FIG. 1 shows an embodiment of the present invention. As shown in the figure, a brushless motor (also simply referred to as a motor) 1 whose rotor is a permanent magnet, a magnetic pole sensor 2 and an encoder (PE) 3 coupled to the rotor, and a commanded current to the motor 1 A power amplifier 4 including a power converter for supplying,
From the pulse processing unit 6 or the like which receives the pulses (two-phase pulses A and B) detected by the controller 5 and the encoder 3 which give a current command value to the power amplifier 4 and which outputs the rotation angle signal within the sampling period. Composed.

The control device 5 has a built-in portion for performing normal control of the motor 1 and a portion for estimating inertia. That is, the part for performing normal control is a speed detecting section 51 for detecting the speed n from the encoder pulse number Δθ within the sampling period, a magnetic pole detecting section 52 for detecting the magnetic pole position φ from the magnetic pole signals (U, V, W), An adder 53 that calculates the error between the speed command value n ^* and the detected speed value (actual value n = dθ / dt), and a speed adjustment that calculates the torque command current value i _T ^* using the error output from the adder 53 as an input. Container (ASR) 5
4. A vector calculator 55 for converting the torque current command value i _T ^* into each phase current command value of the motor 1 and the like.
On the other hand, the control portion for inertia estimation includes a command unit 56, an inertia detection unit 57, a switch 58 that can be switched between an inertia estimation mode and a normal operation mode,
It is composed of 59 and the like.

FIG. 2 is a block diagram showing a specific example of the command unit and inertia detection unit shown in FIG. That is, the command unit 56, as shown in FIG. 2A, sets the magnetic pole position signal φ ′ corresponding to the excitation frequency to a predetermined value.
1 and a setter 562 that sets the torque current command value i _T ′ to be output at the time of inertia estimation to a predetermined value. As shown in FIG. 2B, the detection unit 57 includes an amplitude detector 571 that detects the amplitude of the rotational angular velocity, a divider 572 that receives “1” to take the reciprocal of the amplitude, and a reciprocal of the amplitude that is a constant (K1). ) Multiplier 573 and the like.

Here, regarding the inertia estimation operation,
A description will be given mainly with reference to FIG. Switch 5 now
With the positions 8 and 59 set to the positions shown in the figure, the command unit 56 commands the torque current command value i _T 'and the magnetic pole position signal φ'corresponding to the excitation frequency, and these are given to the vector calculator 55, and the power amplifier 4 The motor 1 is driven via. At this time, if the torque current command value i _T 'and the magnetic pole position signal φ'corresponding to the excitation frequency are selected and commanded so that the motor 1 is not synchronized, the motor 1 is out of step and the minute vibration as described above occurs. As a result, the two-phase pulses A and B from the encoder (position sensor) 3 that accompany this are processed by the pulse processing unit 6 and input to the speed detecting unit 51 and the inertia detecting unit 57, whereby the rotational angular velocity is The magnitude J of inertia can be obtained from the amplitude of the vibration.

FIG. 3 is a block diagram showing another specific example of the command unit and inertia detection unit shown in FIG. That is, as shown in FIG. 3A, a setting unit 561 that sets the magnetic pole position signal φ ′ corresponding to the excitation frequency to a predetermined value in the command unit 56, and a torque current command value i _T to be output at the time of inertia estimation. In addition to the setter 562 that sets'to a predetermined value, a setter 563 of the amount of change per unit time is added in order to gradually increase the torque current command value from zero over time. In addition, as shown in FIG. 3B, the inertia detector 57 includes an amplitude detector 571 for detecting the amplitude of the rotational angular velocity, and an amplitude value A of the rotational angular velocity.
A comparator 574 that compares 2 ′ with a set value A0, a timer 575 that measures an elapsed time t0 until the amplitude of the rotational angular velocity gradually increases and becomes equal to or more than a set value, and a constant (constant for converting the time t0 into inertia J ( K2) A multiplier 576 for multiplication is added.

In such a configuration, by giving a predetermined frequency command from the command unit 56 and an exciting current command so as to gradually increase from zero over time,
The amplitude A2 'of the rotational angular velocity from the start of excitation gradually increases, and the inertia can be estimated by detecting the time t0 until the magnitude of the amplitude reaches a certain set value A0 or more by the timer 575. it can. The operation at this time is shown in FIG. 4, which briefly shows the relationship between the amplitude A2 ′ of the rotational angular velocity and the time t0 until the amplitude A2 ′ becomes equal to or larger than the set value A0.

[0017]

According to the present invention, a three-phase AC excitation is performed at a frequency at which a rotating magnetic field is generated in the three-phase brushless motor but the rotor does not rotate, and a minute vibration generated by the resulting torque is rotated. By detecting the amplitude of either angular acceleration, rotational angular velocity or rotational angle,
An advantage is obtained that the inertia can be estimated without rotating the rotor in a certain direction. Also, the above 3
During phase AC excitation, the voltage or current command is gradually increased, and the vibration torque generated as a result, or the rotational angular acceleration, the rotational angular velocity or the rotational angle of the minute vibration generated by the generated torque, is By measuring the time to reach a certain predetermined value, not only the inertia can be estimated without rotating the rotor in a certain direction, but also the inertia can be estimated by one estimation operation. ..

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a specific example of a command unit and a detection unit shown in FIG.

FIG. 3 is a block diagram showing another specific example of the command unit and the detection unit shown in FIG.

FIG. 4 is an explanatory diagram for explaining the operation of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Brushless motor, 2 ... Magnetic pole sensor, 3 ... Encoder (PE), 4 ... Power amplifier, 5 ... Control device, 6 ... Pulse processing part, 51 ... Speed detection part, 52 ... Magnetic pole detection part, 53
... Adder, 54 ... Speed controller, 55 ... Vector calculator,
56 ... Command unit, 57 ... Inertia detection unit, 58, 59 ...
Switches, 561 to 563 ... Setting device, 571 ... Amplitude detector, 572 ... Divider, 573, 576 ... Multiplier, 574
... comparators, 575 ... timers.

Claims (2)

[Claims] 1. A three-phase brushless motor comprising a stator winding and a rotor having a permanent magnet, an encoder mounted on the rotor shaft, and a counting means for counting pulses emitted from the encoder, A control device that gives a voltage command or a current command and a frequency command to the motor, and a power amplifier that amplifies these commands to drive the three-phase brushless motor, are provided from the control device via the power amplifier. A predetermined voltage or current command and a predetermined frequency command are applied to the stator winding of the motor to excite a three-phase alternating current, and as a result, minute vibrations of the same frequency generated in the rotor are generated by the encoder. And the amplitude of either the rotational angular acceleration signal or the rotational angular velocity signal or the rotational angle signal of the minute vibration is detected, and Inertia estimating device for a brushless motor and obtains the sizes of the Hazuki inertia. 2. A three-phase brushless motor comprising a stator winding and a rotor having a permanent magnet, an encoder mounted on the rotor shaft, and counting means for counting the pulses emitted from the encoder, The control device includes: a control device that gives a voltage command or a current command and a frequency command to the motor; a power amplifier that amplifies these commands to drive the three-phase brushless motor; and a timer that measures time. Through a power amplifier, a three-phase AC excitation is performed by giving a predetermined frequency command and a voltage or current command that gradually increases from zero over time so that the motor goes out of synchronization with the stator winding of the motor. As a result, the minute vibration whose amplitude is gradually increased at the same frequency generated in the rotor is detected through the encoder and the counting means, and the rotational angle acceleration of the minute vibration is detected. A brushless motor characterized in that the amount of inertia is obtained by measuring the time elapsed until the amplitude of any one of the signal, the rotation angular velocity signal, and the rotation angle signal exceeds a predetermined value by the timer. Inertia estimation device.