JPH06153381A - Motor protective unit - Google Patents

Abstract

PURPOSE:To allow accurate temperature protection of motor at low cost without requiring any temperature sensor. CONSTITUTION:A comparing/deciding section 34 compares a motor winding temperature T1 operated at a temperature conversion operating section 32 based on motor parameters (motor current, motor voltage, and motor speed) with a motor temperature T2 estimated at a motor heat model 35 based on motor current and motor speed to produce an observer estimated deviation epsilon. When the deviation epsilon exceeds a predetermined threshold level, a decision is made for predicting failure to produce a motor temperature protective signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor protection device, and more particularly to a motor protection device suitable for use in an electric power steering device of a vehicle.

[0002]

Motors are widely used in all industrial fields, for example in the field of vehicles.
Typically, for example, an electric power steering device of a vehicle uses an electric type using a motor instead of a hydraulic type, and the motor has an increasing tendency in the future due to advantages such as small size and light weight as an actuator.

In the conventional power steering system, the torque sensor detects the steering torque of the steering system, the vehicle speed sensor detects the vehicle speed, and the drive of the motor connected to the steering system is controlled based on the detection results. , Power assist is done. Generally, it is a vehicle speed sensitive type, and the assist force is controlled according to the torque sensor input so that it is light in the low speed range and heavy in the high speed range. By the way, in the above-mentioned conventional apparatus, the temperature sensor mounted inside the assisting motor is used to protect the motor temperature.

[0004]

However, in such a conventional motor protection device, since the temperature sensor is attached to the motor case, the winding temperature of the motor cannot be accurately known, and the temperature protection set value cannot be obtained. Had to be set to a low value, and the motor performance could not be fully utilized. Further, the addition of the temperature sensor has drawbacks such as an increase in wiring and an increase in cost.

On the other hand, there are a method of calculating the motor temperature from the temperature characteristic of the motor parameter and a method of estimating the motor temperature from a motor thermal model with the driving condition as an input. The estimated value could not be obtained accurately and was not suitable for practical use.

[0006] Therefore, an object of the present invention is to provide a motor protection device which can perform accurate motor temperature protection at low cost without a temperature sensor.

[0007]

In order to achieve the above object, a motor protection device according to the present invention includes a motor information detecting means for detecting a motor current, a motor voltage and a motor speed as parameters relating to a motor, and the motor information detecting means. Motor temperature calculating means for calculating the winding temperature of the motor based on the motor current, motor voltage and motor speed detected by the motor, and inputting the motor current and motor speed to estimate the motor temperature using a predetermined motor thermal model The motor temperature estimating means, the motor temperature calculated by the motor temperature calculating means, and the deviation between the motor temperature estimated by the motor temperature estimating means are compared, and whether the deviation exceeds a predetermined threshold value or not. Motor protection means for determining whether or not, and outputting a motor temperature protection signal when exceeding,
It is characterized by having.

[0008]

In the present invention, the motor parameters (motor current,
The deviation between the winding temperature of the motor calculated from the motor voltage and the motor speed) and the motor temperature estimated from the motor thermal model with the motor current and the motor speed as input are compared, and the deviation exceeds a predetermined threshold value. At this time, the motor temperature protection signal is output. Therefore, when the normal motor is driven, the influence of noise is reduced, and an erroneous protection signal is not output. In addition, it is possible to accurately output the motor temperature protection signal at the time of abnormality without using a temperature sensor, and it is possible to perform accurate motor temperature protection at low cost.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are views showing an embodiment in which the motor protection device according to the present invention is applied to an electric power steering device. FIG. 1 is a functional block diagram of this power steering device. In FIG. 1, 1 is an assist motor that assists steering force, 10 is an assist command unit, 20 is a current control unit, and 30 is a motor temperature protection calculation unit.

The assist command unit 10 includes a torque sensor 11
Detection torque V _T and the vehicle speed V _S detected by the vehicle speed sensor 12 are given. The assist torque value instruction function unit 13 in the assist command unit 10 outputs a command value representing the assist torque to be generated by the motor 1 according to the detected torque V _T.
Further, the multiplication constant function unit 14 generates a constant according to the detected vehicle speed V _S , and this constant is multiplied by the assist torque command value in the multiplication calculation unit 15. As a result, the assist torque value (or motor current command value) output from the multiplication calculator 15 becomes a value determined by the detected torque V _T and the detected vehicle speed V _S.

[0011] In this case, according to the steering torque V _T, which substantially proportional to the motor current (assist torque is generated) flows against the steering torque V _T of a range, when it exceeds the above range, a certain the motor current flows (the assist torque is generated) manner, also according to the vehicle speed V _S, when the vehicle speed V _S is high to reduce the motor current (assist torque), the motor current (assist torque when the vehicle speed V _S is low ), An assist command for controlling the motor 1 is generated.

On the other hand, the detected torque V _T is also given to the phase compensator 16. The phase compensator 16 calculates the differential value of the detected torque V _T , and the output of the phase compensator 16 is added to the output of the multiplication calculator 15 to output the assist commander 10 (reference current command value). ) Is supplied to the current control unit 20. The current control unit 20 may be entirely configured by a hardware circuit, or a part thereof may be implemented by computer software.

The current control unit 20 includes a PWM (Pulse) that follows the H-bridge drive method including, for example, four switching elements.
Width Modulation) The motor 1 is driven and controlled by a chopper operation using a pulse, and current feedback control is performed. That is, the armature current detector 26 detects the armature current ia of the motor 1, and the target current command value and the detected current ia given by the current deviation calculator 21 are detected.
The deviation between and is calculated. The absolute value of the deviation is obtained by the absolute value converter 24, and the duty generator 25 determines the duty ratio of the PWM pulse based on the absolute value.

On the other hand, the polarity (positive or negative) of the deviation is discriminated by the positive / negative discriminating section 22, and the generated duty ratio and the discriminated polarity are given to the motor driving section 23, and the motor driving section 23 determines these values. The four switching elements wired in the H-bridge type are controlled to be turned on / off based on the above, and the motor 1 is driven.

On the other hand, the applied voltage V to the motor 1 is detected by the applied voltage detector 41, and the motor temperature protection calculator 3
Given to 0. Further, the speed (angular speed) ω of the motor 1 is detected by the speed sensor 42 and is also given to the motor temperature protection calculation unit 30. Besides, it is given to the motor temperature protection calculation unit 30. Others, armature current detector 2
The motor current I detected by 6 is given to the motor temperature protection calculation unit 30. The applied voltage detection unit 41, the speed sensor 42, and the armature current detection unit 26 constitute a motor information detection unit 50 as a whole.

The motor temperature protection calculation unit 30 is composed of a winding resistance calculation unit 31, a temperature conversion calculation unit 32, a thermal observer 33 and a comparison / determination unit 34. Winding resistance calculator 3
1 receives the motor voltage V, the motor current I, and the motor speed ω as parameters, and calculates the winding resistance R of the motor 1. Here, the electric equation of the steady state of the DC motor is shown as follows. E = R · I + K _e · ω where K _e : induced voltage constant Therefore, the winding resistance R is calculated by modifying this equation.

The motor winding resistance R calculated by the winding resistance calculation unit 31 is input to the temperature conversion calculation unit 32, and the temperature conversion calculation unit 32 uses the relational expression between the motor winding resistance R and the motor winding temperature. To calculate the temperature. The relational expression is shown below. R = R _ref + c (T ₁ −T _ref ) where R _ref : winding resistance value at reference temperature c: constant (determined by winding material) T ₁ : motor winding temperature T _ref : reference temperature

The current motor winding temperature T ₁ is calculated by inputting the motor winding resistance calculated by the above winding resistance calculating section 31 into R in the above equation. The calculated current motor winding temperature T ₁ is given to the thermal observer 33. The thermal observer 33 has a motor thermal model unit 35, a gain unit 36, and a subtractor 37. The motor heat model unit 35 calculates the state vector T ₂ of the motor temperature based on the motor current I and the motor speed ω.

The calculation process of the motor heat model unit 35 is shown in FIG. In FIG. 2, first, the motor current I and the motor speed ω are input, and an input vector u (corresponding to the motor loss) is calculated in the motor loss calculation unit 61. The input vector u is [u ₁ u ₂
u ₃ ] is used as a parameter. However,
u ₁ is winding loss, u ₂ is eddy current loss, and u ₃ is loss due to motor shaft rotation.

[0020]

[Formula 1]

The input vector u is given to the thermal model parameter matrix B62. The output of the thermal model parameter matrix B62 is output by the adder 63 to the thermal model parameter matrix A6.
4 and 1 / as a state vector (dot T ₂ ).
The motor temperature T ₂ (scalar amount) is output through the S calculator 65. The state vector (dot T ₂ ) is a vector corresponding to the motor temperature, and [T _K2 T
_C2 T _R2 ] as a parameter. Where T _K2 is the motor magnet temperature, T _C2 is the motor case temperature,
T _R2 is the motor winding temperature.

[0022]

[Formula 2]

The state vector (dot T ₂ ) is shown in FIG.
By passing through the arithmetic circuit of, dot T ₂ = A · T ₂ + B · u

Now, the motor temperature T ₂ (scalar amount) which is the output of the motor heat model unit 35 is subtracted from the motor winding temperature T ₁ which is the output of the temperature conversion calculation unit 32 by the subtractor 37, and the deviation ε ( = T ₁ −T ₂ ) is calculated and the comparison determination unit 34
And the deviation ε is input to the gain unit 36. Then, the gain unit 36 multiplies the deviation ε by a predetermined gain H and outputs the product to the motor heat model unit 35. Therefore, the motor temperature T ₂ is expressed by the following equation. T ₂ = A · T ₂ + B · u + H · (T ₁ −T ₂ ) The motor winding temperature T ₁ output from the temperature conversion computing unit 32 is [0 0 T _R1 ] as shown in the following expression 3. It is represented by the determinant.

[0025]

[Formula 3]

Thus, in the thermal observer 33, the deviation ε
By feeding back the motor temperature estimated value T
Control is performed to reduce the error of ₂ . The observer estimated deviation ε (= T ₁ −T ₂ ) is input to the comparison determination unit 34, and the comparison determination unit 34 determines the motor failure prediction based on the observer estimated deviation ε. Here, care is taken not to make false failure prediction detection due to noise. For example, the threshold is ±± in consideration of process noise having characteristics of Gaussian white noise and measurement noise.
Set ³ √ σ ² .

Σ ² here represents the variance of the observer estimation deviation. When the observer estimated deviation ε exceeds this threshold level, it is determined that a failure is predicted and a protection signal is output. The protection signal is used, for example, as a trigger for a procedure such as activating an informing means for informing that the motor temperature is high and is dangerous, or interrupting the current to stop the motor 1.

As described above, in the present embodiment, the motor winding temperature T ₁ calculated from the motor parameters (motor current, motor voltage and motor speed) and the motor estimated from the motor thermal model using the motor current and motor speed as inputs. The observer estimated deviation ε with the estimated temperature value T ₂ is compared, and when the observer estimated deviation ε exceeds a predetermined threshold level, a judgment for predicting a failure is made and a motor temperature protection signal is output. Based on this motor temperature protection signal, for example, the current of the motor 1 is cut off and the power assist is stopped, so that further heat generation of the motor 1 is avoided and a failure is avoided.

[0029] In this case, by this that the gain H is multiplied by the observer estimated differential ε is fed back Chi motor thermal model, since modifications motor temperature estimate T ₂ takes place, to reduce the influence of noise at the time of normal motor drive As a result, the output of a false protection signal can be eliminated. Further, since it is possible to accurately output the motor temperature protection signal when there is an abnormality (for example, motor temperature rise) without using a temperature sensor, accurate motor temperature protection can be performed without increasing costs and without increasing wiring. be able to. As a result, it is possible to obtain a motor protection device that can be sufficiently put to practical use.

The above embodiment is an example in which the present invention is applied to an electric power steering device, but the application of the present invention is not limited to this, and it is applicable to other devices using a motor. Can be widely applied.

[0031]

According to the present invention, it is possible to reduce the influence of noise during normal motor drive and eliminate the output of an erroneous protection signal, and to output the motor temperature protection signal accurately when an abnormality occurs. , Without using a temperature sensor.
Therefore, accurate motor temperature protection can be performed without increasing costs and increasing wiring. As a result, it is possible to obtain a motor protection device that can be sufficiently put to practical use.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment in which a motor protection device according to the present invention is applied to an electric power steering device.

FIG. 2 is a diagram showing a calculation process of a motor thermal model unit of the embodiment.

[Explanation of symbols]

 1 Assist Motor (Steering Auxiliary Motor) Torque Sensor 12 Vehicle Speed Sensor 20 Current Control Section 26 Armature Current Detection Section 30 Motor Temperature Protection Calculation Section 31 Winding Resistance Calculation Section 32 Temperature Conversion Calculation Section 33 Thermal Observer 34 Comparison Judgment Section 41 Applied Voltage Detector 42 Speed sensor 50 Motor information detector 61 Motor loss calculator 62 Thermal model parameter matrix B 63 Adder 64 Thermal model parameter matrix A

Claims (1)

[Claims] 1. A motor information detecting means for detecting a motor current, a motor voltage and a motor speed as parameters relating to the motor, and a motor current detected by the motor information detecting means,
A motor temperature calculating means for calculating the winding temperature of the motor based on the motor voltage and the motor speed; and a motor temperature estimating means for estimating the motor temperature using a predetermined motor thermal model with the motor current and the motor speed as inputs. The deviation between the motor temperature calculated by the motor temperature calculating means and the motor temperature estimated by the motor temperature estimating means is compared, and it is determined whether or not the deviation exceeds a predetermined threshold value. And a motor protection unit that outputs a motor temperature protection signal.