JP2010028971A - Motor drive control apparatus and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a simple configuration even with one shunt system and to prevent an output limit of a motor. <P>SOLUTION: A current command value Irefj to a motor 7 is calculated and a voltage command value Vj is calculated based on the calculated current command value Irefj and a resistance estimation value R^ of the motor 7 to drive the motor 7 based on the calculated voltage command value Vj. A total current estimation value I^ for energizing the motor 7 is calculated and a total current detection value Idct is detected by a current detector 26. An estimation resistance value R^ of the motor 7 is estimated based on the total current estimation value I^ and total current detection value Idct and the estimation resistance value R^ used to calculate the voltage command value Vj is updated by the estimation resistance value R^. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive control device and an electric power steering device including the same.

In the feedback control of the electric motor, each phase current is required. However, a single shunt system is known in which all currents are detected by one shunt resistor and each phase current is detected based on this current.
In order to detect the phase current, a plurality of PWM patterns combining a basic vector and a zero vector are generated, and the magnitude of this basic vector is made to correspond to the switching energization time, and the detection timing is matched to the duty ratio. There is something to change (see Patent Document 1).

On the other hand, although the detection timing is fixed, there is a type in which PWM driving is performed by shifting the rising time of switching in the order of phases with a large duty ratio, and each phase current is detected at the rising of switching (see Patent Document 2).
JP 2006-246649 A JP-T-2005-53270

  However, in the conventional example described in Patent Document 1, the detection timing must be changed in accordance with the duty ratio, which requires a special controller. Further, in the conventional example described in Patent Document 2, since it is necessary to shift the switching rise time for each phase, current detection becomes difficult when the duty ratio of each phase is balanced with a large value. Therefore, it is necessary to limit the use band of the duty ratio, but this limits the motor output.

  An object of the present invention is to provide a simple configuration even in the case of a single shunt system, and to prevent output limitation of an electric motor.

  The motor drive control device according to claim 1 is a motor drive control device that drives and controls an electric motor, calculates a current command value for the electric motor, and calculates the calculated current command value and circuit characteristics of the electric motor. A calculation means for calculating a voltage command value based on the voltage, a drive means for driving the electric motor based on the voltage command value calculated by the calculation means, and a single current detection for detecting a total current supplied to the electric motor. Means, a current estimation means for estimating the total current supplied to the electric motor according to the voltage command value calculated by the calculation means, a detection value detected by the current detection means, and an estimation estimated by the current estimation means Resistance estimation means for estimating the circuit resistance of the electric motor based on the value, and the calculation means calculates the circuit resistance value in the circuit characteristic used for calculating the voltage command value as a previous value. Resistance estimating means for updating the estimated value estimated.

  In the motor drive control device according to claim 2, the electric motor is constituted by a multiphase motor, and the current estimating means is energized to the electric motor in accordance with a voltage command value of each phase calculated by the calculating means. Phase current estimation means for estimating the current of each phase, and total current estimation means for estimating the total current applied to the electric motor according to the estimated value of each phase estimated by the phase current estimation means. Is done.

According to a third aspect of the present invention, in the motor drive control device, the total current estimating means is configured to energize the electric motor with an estimated value having the maximum absolute value among estimated values of each phase estimated by the phase current estimating means. It is estimated as the total current.
According to a fourth aspect of the present invention, in the motor drive control device, the resistance estimation unit calculates a circuit resistance of the electric motor based on a difference between a detection value detected by the current detection unit and an estimation value estimated by the total current estimation unit. presume.

  In the motor drive control device according to claim 5, the resistance estimating unit selects a phase having the maximum absolute value of the estimated value estimated by the phase current estimating unit among the phases as the selected phase. A phase other than the phase is set as a non-selected phase, and in the selected phase, the circuit resistance of the electric motor is estimated based on the difference between the detected value detected by the current detecting means and the estimated value estimated by the total current estimating means. In the non-selected phase, the circuit resistance of the electric motor is estimated based on the ratio between the estimated value estimated by the phase current estimating means and the estimated value estimated by the total current estimating means.

  An electric power steering apparatus according to a sixth aspect includes the motor drive control apparatus according to any one of the first to fifth aspects, wherein the electric motor transmits an assist torque to a steering system, and the calculation unit includes: A current command value for the electric motor is calculated according to the steering torque of the driver.

According to the present invention, it is not necessary to detect each phase current by performing feedforward control for driving the electric motor based on the calculated voltage command value. Therefore, a special controller and complicated arithmetic processing are not required, and a simple configuration can be achieved. Further, it is possible to avoid a situation where current detection is difficult and the motor output is limited.
Further, the total current supplied to the electric motor is estimated, the total current is detected by one current detection means, the circuit resistance of the electric motor is estimated based on the estimated value and the detected value, and the voltage command value By updating the circuit resistance used for the calculation to the estimated value, it is possible to prevent a decrease in robustness that becomes a problem for feedforward control.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, the configuration of the present embodiment will be described.
FIG. 1 is a schematic configuration of a power steering apparatus. The steering wheel 1 is connected to a wheel 5 through a steering shaft 2, a rack and pinion 3, and a tie rod 4 in order, and an electric motor 7 is connected to the steering shaft 2 through a speed reducer 6. The electric motor 7 is driven and controlled by the control device 8 to apply assist torque to the driver's steering operation.

The control device 8 is supplied with electric power from a battery 11 connected via an ignition switch 9 and a fuse 10, and is supplied with a steering torque T detected by a torque sensor 12, detection signals sin θ and cos θ of a resolver 13, and a vehicle speed sensor 14. Is input.
The torque sensor 12 detects a torsion angle of a torsion bar inserted between an input shaft and an output shaft in the steering shaft 2 as a change in magnetic flux by a search coil, and a voltage induced in the search coil. Is converted into the steering torque T. For example, as shown in FIG. 2, the higher the voltage the steering torque T increases in the rightward direction as the steering torque T is zero when V _0, the voltage increases from V _0, the voltage decreases from V ₀ The steering torque T in the left direction increases.

When the one-phase excitation signal sinωt is input, the resolver 13 outputs two-phase detection signals sinθ and cosθ corresponding to the sine and cosine according to the motor rotation angle θ.
Next, the motor drive control process of the first embodiment executed by the control device 8 will be described based on the block diagram of FIG.
First, according to the steering torque T and the vehicle speed V, the current command value Irefj (j = u, v,
w) is calculated. Specifically, when the steering torque T is less than or equal to a predetermined value Ts, the current command value Irefj is maintained at 0, and the current command value Irefj increases as the steering torque T increases and the vehicle speed V increases. The command value Irefj is set to be small.

The feedforward current controller 21 calculates the voltage command value Vj of each phase according to the current command value Irefj of each phase using a transfer function including the motor characteristic formula as shown in the following formula (1). .
Vj = C (s) Irefj = {(Ls + R ^) / (T 1 s + 1)} Irefj
……… (1)
Here, L is an inductance value, R ^ is an estimated resistance value, and T ₁ is a desired system cutoff time constant. The estimated resistance value R ^ is the circuit resistance of the electric motor 7. The transfer function C (s) is a feedforward controller 21 configured so that the dynamic characteristic from the current command value to the actual current value including hardware becomes a desired dynamic characteristic [1 / (T ₁ s + 1)]. Yes, by using the estimated resistance value R ^, it is possible to prevent the occurrence of overcurrent due to insufficient robustness, which is a problem for the feedforward controller 21. If a differentiator can be introduced into the program configuration, the system cut-off time constant T _{1 is set} to zero.

The EMF compensator 22 outputs an EMF compensation value for compensating the back electromotive voltage EMF, the adder 23 adds the EMF compensation value to the voltage command value Vj, and the duty converter 24 performs EMF compensation. Voltage command value Vj is converted to duty command value Dj and output to inverter 25.
The inverter 25 is PWM driven based on the duty command value Dj of each phase, and applies a drive voltage to the electric motor 7. A single current detector 26 composed of a shunt resistor is provided at the lower stage of the inverter 25, and a total current detection value Idct supplied to the electric motor 7 by the current detector 26 is detected.

On the other hand, the phase current estimator 31 receives the voltage command value Vj calculated by the feedforward controller 21 and calculates the phase current estimated value Ij ^ according to the transfer function of the following equation (2).
Ij ^ = {1 / (Ls + R ^)} Vj (2)
The total current estimator 32 receives the phase current estimation value Ij ^ and calculates the total current estimation value I ^ corresponding to the total current detection value Idct.

  For example, in the case of a system driven by a sine wave current, the current of each phase flowing through the motor has a waveform as shown in FIG. When the current detector 26 is composed of a shunt resistor and the sampling method is a peak hold method, the current detector 26 detects a waveform as shown in FIG. 5, that is, a waveform that takes the maximum value of the current of each phase. .

Therefore, the total current estimator 32 calculates the total current estimation value I ^ by first converting each of the current estimation values Ij ^ into an absolute value and selecting the maximum value among them.
The adder 33 calculates a difference ΔI between the total current detection value Idct and the total current estimation value I ^.
The resistance estimator 34 receives the difference ΔI and calculates the estimated resistance value R ^ of the electric motor 7.

Here, the calculation principle of the estimated resistance value R ^ will be described.
When the change from the current estimated resistance value R ^ is ΔR and the back electromotive force EMF is compensated due to the temperature change of the system, the voltage V and the actual current i are as follows (3 ) Expression.
V = L (di / dt) + (R ^ + ΔR) i (3)
On the other hand, the voltage V and the current estimated value i ^ are expressed by the following equation (4).
V = L (di ^ / dt) + R ^ i ^ (4)
From the above equations (3) and (4), the change ΔR is expressed by the following equation (5).
L (di / dt) + (R ^ + ΔR) i = L (di ^ / dt) + R ^ i ^
ΔRi = L (di ^ / dt) -L (di / dt) + R ^ i ^ -R ^ i
ΔRi = L (d / dt) (i ^ -i) + R ^ (i ^ -i)
ΔR = {L (d / dt) (i ^ -i) + R ^ (i ^ -i)} / i
......... (5)

Assuming that the difference e (= i ^ -i) between the current estimated value i ^ and the actual current i, the change ΔR is expressed by the following equation (6).
ΔR = {L (d / dt) e + R ^ e} / i (6)
The above equation (6) represents one phase and can be considered by replacing it with the total current. That is, when the actual current i is considered as the total current detection value Idct and the current estimation value i ^ is considered as the total current estimation value I ^, the following equation (7) is derived.
ΔR = {L (d / dt) e + R ^ e} / Idct
= (Ls + R ^) e / Idct (7)

Here, the differential value of e is required due to the structure of the formula, but the introduction of a differentiator may not be preferable. That is, if noise is added to the total current detection value Idct, the differential value is greatly affected, and the estimation error by the resistance estimator 34 becomes large. Therefore, as shown in the following equation (8), noise resistance is improved by adding a filter configuration.
ΔR = (g / Idct) {(Ls + R ^) / (T ₂ s + 1)} e (8)
Here, T ₂ is a desired filter cutoff time constant capable of sufficiently removing noise, and g is a convergence gain that affects the convergence speed of the estimated value.

The resistance estimator 34 calculates the change ΔR as described above, adds it to the current estimated resistance value R ^, updates it as a new estimated resistance value R ^, and outputs it to the feedforward current controller 21.
The feedforward current controller 21 updates the input estimated resistance value R ^ as a new estimated resistance value R ^ and uses it to calculate the voltage command value Vj.

Next, the effect of this embodiment is demonstrated.
When one shunt method is used, feedback control is performed. In addition to requiring a special controller and arithmetic processing to detect each phase current, conditions are imposed on current detection and motor output may be limited. there were.

Therefore, in this embodiment, feedforward control is performed. This eliminates the need to detect each phase current, so that a special controller and arithmetic processing are not required, and a simple configuration can be achieved. In addition, it is possible to avoid a situation where current detection becomes difficult and the motor output is limited.
In addition, the total current estimated value I ^ energized to the electric motor 7 is calculated, and the single current detector 26 detects the total current detected value Idct. The total current estimated value I ^ and the total current detected value Idct are Therefore, the estimated resistance value R ^ of the electric motor 7 is estimated, and the estimated resistance value R ^ used to calculate the voltage command value Vj is updated with this estimated resistance value R ^. It is possible to prevent a decrease in robustness.

  Regarding the calculation of the total current estimated value I ^, first, the phase current estimated value Ij ^ is calculated according to the voltage command value Vj, and the total current estimated value I ^ is calculated according to the phase current estimated value Ij ^. The total current estimated value I ^ can be easily calculated. In particular, among the phase current estimated values Ij ^, the estimated value having the maximum absolute value is simply calculated as the total current estimated value I ^, so that it can be easily calculated.

As for the calculation of the estimated resistance value R ^, it is easy to calculate the estimated resistance value R ^ based on the difference ΔI between the total current detection value Idct and the total current estimation value Ij ^ by using the equation (8). The estimated resistance value R ^ can be calculated.
From the above, the feedforward current controller 21 corresponds to “calculation means”, the inverter 25 corresponds to “drive means”, the current detector 26 corresponds to “current detection means”, the phase current estimator 31 and all The current estimator 32 corresponds to “current estimation means”, and the resistance estimator 34 corresponds to “resistance estimation means”. The phase current estimator 31 corresponds to “phase current estimation means”, and the total current estimator 32 corresponds to “current estimation means”.

[Second Embodiment]
Next, the motor drive control process of the second embodiment executed by the control device 8 will be described based on the block diagram of FIG.
In the first embodiment described above, it is assumed that the circuit resistance of each phase of the three-phase motor is balanced, but in this second embodiment, the circuit resistance of each phase of the three-phase motor is different. It is assumed that there is.

Therefore, a phase determination unit 41 is provided for determining the phase having the maximum absolute value of the phase current estimation value Ij ^ as the selected phase m and the other phases as the non-selected phase n, and the determination result is used as the resistance estimator 34. Output to.
In the selection phase m, the resistance estimator 34 is based on the difference ΔI between the total current detection value Idct and the total current estimation value Ij ^ using the equation (8) as described in the first embodiment. Calculate the estimated resistance value Rm ^. On the other hand, in the non-selected phase n, as shown in the following equation (9), the ratio [| In ^ | / | I ^ |] of the phase current estimated value In ^ and the total current estimated value I ^ (= Im ^) Based on the above, the estimated resistance value Rn ^ is calculated.

Rn ^ = Rn ^ + ΔRm (| In ^ | / | I ^ |) ² (9)
As described above, the estimated resistor 34 calculates the resistance change amount of the non-selected phase n by ΔRm (| In ^ | / | I ^ |) ² and adds it to the current estimated resistance value Rn ^. The estimated resistance value Rn ^ is updated and output to the feedforward current controller 21.
The feedforward current controller 21 updates the input estimated resistance value Rj ^ of each phase as a new estimated resistance value Rj ^ and uses it to calculate the voltage command value Vj.

Next, the effect of this embodiment is demonstrated.
The estimated resistance value Rj ^ of each phase is not always the same.
Therefore, in the present embodiment, the phase having the maximum absolute value of the phase current estimated value Ij ^ is set as the selected phase m, the other phases are set as the non-selected phase n, and in the selected phase m, the total current detection value Idct and Calculate the estimated resistance value Rm ^ based on the difference ΔI from the total current estimated value Ij ^. In the unselected phase n, the estimated resistance value is calculated based on the ratio between the phase current estimated value In ^ and the total current estimated value I ^. Rn ^ is calculated. Thereby, even if the estimated resistance value Rj ^ of each phase is unbalanced, the estimated resistance value Rj ^ of each phase can be accurately calculated.
From the above, the resistance estimator 34 and the phase determiner 41 correspond to “resistance estimation means”.

[Third Embodiment]
Next, a third embodiment will be described.
In the third embodiment, as shown in FIGS. 7 and 8, the current detector 26 is provided in the upper stage of the inverter 25. That is, except that the current detector 26 is provided in the upper stage, the same motor drive control process as that of the first embodiment is executed in FIG. 7, and the same motor drive control process as that of the second embodiment is executed in FIG. Execute.
Thus, even if the current detector 26 is in the upper stage, the above-described effects can be obtained.

It is a schematic block diagram of an electric power steering device. It is a detection signal of a torque sensor. It is a block diagram which shows the motor drive control process of 1st Embodiment. It is a waveform of a phase current. It is a waveform of a phase current and a total current. It is a block diagram which shows the motor drive control process of 2nd Embodiment. It is a modification of 1st Embodiment. It is a modification of 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Rack and pinion, 4 ... Tie rod, 5 ... Wheel, 6 ... Reduction gear, 7 ... Electric motor, 8 ... Control apparatus, 12 ... Torque sensor, 13 ... Resolver, 14 ... Vehicle speed sensor, 21 ... feed forward current controller, 22 ... EMF compensator, 23 ... adder, 24 ... duty converter, 25 ... inverter, 26 ... current detector, 31 ... phase current estimator, 32 ... total current estimation , 33 ... adder, 34 ... resistance estimator, 41 ... phase determiner

Claims (6)

A motor drive control device for driving and controlling an electric motor,
Calculating a current command value for the electric motor, calculating a voltage command value based on the calculated current command value and circuit characteristics of the electric motor; and based on the voltage command value calculated by the calculation unit Drive means for driving the electric motor;
One current detecting means for detecting the total current supplied to the electric motor, a current estimating means for estimating the total current supplied to the electric motor according to the voltage command value calculated by the calculating means, and the current Resistance estimation means for estimating circuit resistance of the electric motor based on the detection value detected by the detection means and the estimation value estimated by the current estimation means,
The motor drive control device, wherein the calculation means updates a circuit resistance value in the circuit characteristic used for calculation of the voltage command value to an estimated value estimated by the resistance estimation means. The electric motor is composed of a multiphase motor,
The current estimation means includes a phase current estimation means for estimating a current of each phase energized to the electric motor according to a voltage command value of each phase calculated by the calculation means, and each of the phase current estimation means estimated by the phase current estimation means The motor drive control device according to claim 1, comprising: a total current estimation unit configured to estimate a total current supplied to the electric motor according to an estimated value of the phase.   The total current estimating means estimates an estimated value having the maximum absolute value among estimated values of each phase estimated by the phase current estimating means as a total current to be supplied to the electric motor. The motor drive control device according to claim 2.   The resistance estimation unit estimates the circuit resistance of the electric motor based on a difference between a detection value detected by the current detection unit and an estimation value estimated by the total current estimation unit. 4. The motor drive control device according to 3. The resistance estimation means, among each phase, the phase having the maximum absolute value of the estimated value estimated by the phase current estimation means is a selected phase, and a phase other than the selected phase is a non-selected phase,
In the selection phase, the circuit resistance of the electric motor is estimated based on the difference between the detection value detected by the current detection unit and the estimation value estimated by the total current estimation unit,
3. The circuit resistance of the electric motor is estimated based on a ratio between an estimated value estimated by the phase current estimating means and an estimated value estimated by the total current estimating means in the non-selected phase. Or the motor drive control apparatus of 3. The motor drive control device according to any one of claims 1 to 5,
The electric motor transmits assist torque to a steering system,
The electric power steering apparatus characterized in that the calculating means calculates a current command value for the electric motor in accordance with a steering torque of a driver.

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