JP2001260920A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reliability and safety by correctly determining the output state of a driving signal being outputted to an induction motor for auxiliary steering. SOLUTION: A control unit 13 calculates a target torque instruction value Ts according to a steering torque signal To of a driver, a vehicle speed signal V, and a braking signal B, and a motor driving circuit 16 outputs a three-phase AC driving signal corresponding to the target torque instruction value Ts. Thereby, the induction motor 5 generates an auxiliary steering force corresponding to the steering force of a driver. A determination value computing part 27 calculates a determination value Li corresponding to the driving state of a vehicle from each upper limit value data memorized in an upper limit value data memory part 25, and a signal determination part 28 compares the sum of squares of real currents iU, iV, iW, of the driving signal detected with current sensors 10, 11, 12 with a determination value Li. The output abnormality caused by excessive driving signal can accurately be determined, and reliability and safety can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering apparatus preferably used for reducing a steering force by an induction motor when a driver of a vehicle performs a steering operation.

[0002]

2. Description of the Related Art Generally, a vehicle such as an automobile is equipped with a hydraulic or electric power steering device. And
For example, an electric power steering device is configured to reduce a driver's steering force by an output of an electric motor connected to a steering shaft of a vehicle.

[0003] An electric power steering apparatus of this kind according to the prior art includes an induction motor for generating an auxiliary steering force for assisting a driver's steering force, and the steering motor for controlling an output torque of the induction motor. A control unit that calculates a torque command value according to a force, a motor drive circuit that is provided integrally with or separate from the control unit and that outputs a drive signal corresponding to the torque command value calculated by the control unit to the induction motor. (For example, Japanese Patent Application Laid-Open No. H8-164863).

Here, the control unit controls the output torque of the induction motor using a control method called vector control. In this vector control, the control of the induction motor is virtually treated as the control of the DC motor, and the command signal for controlling the output torque is controlled by two.
After calculating the target excitation current and the target torque current, which are two DC current components, this command signal is converted into an AC signal corresponding to the induction motor.

[0005] For this reason, the control unit comprises: a torque command value calculation unit for detecting a steering force when a driver of the vehicle performs a steering operation with a torque sensor or the like and calculating a torque command value corresponding to the steering force; A command signal calculator for calculating a target excitation current command value and a target torque current command value as a DC command signal using the torque command value by the torque command value calculator; and a DC command calculated by the command signal calculator. And a signal converter for converting the signal into a three-phase AC signal.

In this case, the command signal computing section holds the target excitation current command value at a substantially constant value according to the design specifications of the induction motor, for example, and sets the target torque current command value to the steering force (torque command value) of the driver. ). The signal converter converts the DC command signal into a three-phase AC signal, and outputs the AC signal to the motor drive circuit as a voltage signal by means such as pulse width modulation (PWM).

The motor drive circuit is, for example, a PWM
3 corresponding to the voltage waveform of the command signal by an inverter, etc.
A phase alternating current signal is generated, and this current signal is output as a drive signal to each phase of the induction motor. Thereby, the induction motor is driven with an output torque corresponding to the torque command value of the control unit, and is configured to appropriately assist the steering operation of the driver.

Further, the prior art power steering apparatus described in Japanese Patent Application Laid-Open No. H8-148663 discloses an abnormal stop in which, for example, when a failure or the like occurs in a motor drive circuit, this is detected and the induction motor is stopped. Means. The abnormal stop means, for example, reverses the time during which the polarity of the AC signal converted by the signal converter of the control unit is inverted between positive and negative and the polarity of the drive signal actually output from the motor drive circuit. If the two signals have different polarity reversal times (that is, two signal periods), it is determined that the drive signal is in a DC state due to an abnormality such as a short circuit, and the induction motor is controlled. Stop the power supply. Thus, the abnormal stop means prevents the induction motor from becoming a generator due to an abnormality in the drive signal and applying a braking force to the steering shaft (power generation braking state).

[0009]

In the prior art described above, the period of the AC signal obtained by converting the command signal and the period of the drive signal are compared by the abnormal stop means, and the drive signal becomes DC due to an abnormality such as a short circuit. , The drive signal to the induction motor is stopped in order to prevent the power generation braking of the induction motor.

However, the abnormality stopping means used in the prior art merely detects the abnormality by comparing the polarity inversion times of the two signals. If the signal values are different, the error of the drive signal with respect to the command signal cannot always be detected stably.

For this reason, in the prior art, there is a possibility that the output torque of the induction motor becomes excessive with respect to the steering force of the driver due to, for example, an abnormality in the drive signal, and the reliability in performing the abnormal stop processing is reduced. There is a problem that it is difficult to improve.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to detect an abnormality of a drive signal output to an induction motor without fail, and to provide guidance based on a driver's steering force or the like. An object of the present invention is to provide a power steering device capable of stably controlling the output torque of a motor and improving reliability.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an induction motor for generating an auxiliary steering force for assisting a steering force, and at least the above-mentioned control for controlling the output torque of the induction motor. The motor includes a torque command value calculating means for calculating a target torque command value corresponding to a steering force, and a motor drive circuit for outputting a drive signal corresponding to the target torque command value calculated by the torque command value calculating means to the induction motor. Applied to power steering devices.

The first aspect of the present invention is characterized in that a driving state detecting means for detecting a driving state of the vehicle and a driving signal detecting means for detecting a driving signal outputted from the motor driving circuit to the induction motor. An upper limit data storage unit storing upper limit data for determining an upper limit of the output state of the drive signal; and an upper limit value of the upper limit data storage unit according to the driving state of the vehicle detected by the driving state detection unit. Judgment value calculation means for calculating a judgment value from the data, and comparing the output value of the drive signal detected by the drive signal detection means with the judgment value by the judgment value calculation means to determine whether the output state of the drive signal is normal or not. And a signal determination unit that performs the determination.

With this configuration, the torque command value calculating means can calculate the torque command value according to, for example, the steering force of the driver, the driving state of the vehicle, and the like. A corresponding drive signal can be output to drive the induction motor. In addition, the upper limit data storage unit stores in advance a plurality of types of upper limit data according to, for example, the driving state of the vehicle, and the determination value calculation unit includes:
A determination value can be calculated from the upper limit data in accordance with the driving state of the vehicle detected by the driving state detecting means. The signal determination means determines whether the output state of the drive signal is normal by comparing the output value of the drive signal detected by the drive signal detection means with the determination value calculated by the determination value calculation means. Can be.

According to a second aspect of the present invention, the driving state detecting means comprises a vehicle speed sensor for detecting the traveling speed of the vehicle, and the upper limit data storage means stores a plurality of types of upper limit data according to the traveling speed of the vehicle. And the determination value calculating means calculates a determination value from each of the upper limit value data using a detection signal output from the vehicle speed sensor.

Thus, for example, in normal motor control, when the output value of the drive signal is changed in accordance with the running state of the vehicle, the output characteristic of the drive signal with respect to the vehicle speed and the like are stored in the upper limit data storage means. It can be stored in advance as type upper limit data. As a result, the determination value calculation means can calculate a determination value according to the vehicle speed from the upper limit data using the detection signal from the vehicle speed sensor, and the signal determination means changes the drive signal according to the traveling state of the vehicle. Even in such a case, it can always be determined whether or not the output value is normal.

According to the third aspect of the present invention, the driving state detecting means includes a vehicle speed sensor for detecting a running speed of the vehicle,
Deceleration state detection means for detecting a deceleration state of the vehicle, the upper limit value data storage means stores a plurality of types of upper limit value data according to the traveling speed and deceleration state of the vehicle, and the determination value calculation means comprises A determination value is calculated from the upper limit data using detection signals output from the vehicle speed sensor and the deceleration state detection means.

Thus, the deceleration state detecting means can detect, for example, a negative acceleration applied to the vehicle, a brake operation force of the driver, and the like as a deceleration state of the vehicle. Further, the upper limit data storage means may store in advance, for example, the output characteristics of the drive signal with respect to the traveling speed and the deceleration state of the vehicle as a plurality of types of upper limit data. The signal determination means always determines whether or not the output value of the drive signal is normal using the determination value by the determination value calculation means, even when the drive signal changes according to the traveling speed and the deceleration state of the vehicle. Can be.

Further, according to the invention of claim 4, the deceleration state detecting means comprises a braking force sensor for detecting a braking force of the vehicle.

Thus, for example, the braking force applied to the vehicle at the time of the braking operation can be detected as the deceleration state of the vehicle by the braking force sensor, and the judgment value calculation means uses the detection signals from the vehicle speed sensor and the braking force sensor to determine the upper limit value. The determination value for the drive signal can be calculated from the upper limit value data of the data storage means.

Further, according to the invention of claim 5, the torque command value calculating means is configured to calculate the torque command value in accordance with the driving state of the vehicle and the steering force detected by the driving state detecting means.

Thus, the torque command value calculating means calculates the torque command value according to not only the driver's steering force but also, for example, the running speed and deceleration state of the vehicle detected by a vehicle speed sensor, a braking force sensor or the like. be able to. Then, the motor drive circuit can control the output torque of the induction motor by changing the output state (output value) of the drive signal according to the torque command value.

According to a sixth aspect of the present invention, the motor drive circuit outputs a three-phase AC current signal to the induction motor as the drive signal, and the drive signal detecting means outputs the three-phase AC current signal. A current sensor for individually detecting at least two-phase current values, wherein the signal determination means squares and adds the three-phase current values of the drive signal obtained from the detection results of the current sensor, and The sum of the squares of the current values is calculated as the output value of the drive signal.

As a result, at least two-phase current values of the three-phase AC drive signals output from the motor drive circuit can be detected by the current sensor, and the other one-phase current values can be obtained by subtracting these two-phase current values. It can be calculated using, or directly detected by another current sensor. Further, the signal determination means can calculate the sum of squares of the respective current values as the output value of the drive signal by squaring and adding the three-phase current values of the drive signal.

Further, according to the invention of claim 7, the signal judging means judges that the drive signal is normal when the output value of the drive signal is equal to or less than the judgment value, and the output value of the drive signal exceeds the judgment value. In some cases, it is determined to be abnormal.

Thus, the judgment value calculation means can calculate a judgment value according to the driving state of the vehicle using the upper limit value data and the like, and the signal judgment means compares this judgment value with the output value of the drive signal. Thus, when the drive signal increases beyond the determination value, the output value can be determined to be abnormal.

Further, according to the present invention, when the signal determination means determines that the output state of the drive signal is abnormal, it is provided with fail-safe means for notifying the abnormality or stopping the drive signal to the induction motor. And

Thus, when an abnormality is determined by the signal determination means, the failure can be notified to the driver of the vehicle by the fail-safe means or the drive signal to the induction motor can be stopped.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power steering apparatus for a vehicle according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Reference numeral 1 denotes a steering shaft for steering the vehicle. The steering shaft 1 includes an input shaft 1A that is integrally rotated with a steering handle 2 (hereinafter, referred to as a handle 2) of the vehicle, and an induction motor 5 described later. Output shaft section 1B driven to rotate by
The output shaft portion 1B is connected to a steering wheel (not shown) of the vehicle via a connecting portion 3 such as a rack-pinion.
It is connected to. Further, a torque sensor 4 described later is provided between the input shaft 1A and the output shaft 1B of the steering shaft 1.

Reference numeral 4 denotes a torque sensor provided on the steering shaft 1. The torque sensor 4 detects a steering force when the driver steers the steering wheel 2 as a rotational torque of the input shaft portion 1A, which will be described later. A steering torque signal To is output to the control unit 13.

Reference numeral 5 denotes a three-phase induction motor serving as a power source of a power steering device. The induction motor 5 has an output side connected to an output shaft portion 1B of the steering shaft 1 via a reduction gear 6, and When the driver steers the steering wheel 2, auxiliary power (auxiliary steering force) for assisting the driver's steering force is added to the output shaft portion 1B.

The induction motor 5 generates an auxiliary steering force according to a driver's steering force or the like according to a drive signal output from a motor drive circuit 16 to be described later, and the auxiliary steering force is reduced by the reduction gear 6 and the steering shaft. When the vehicle is steered, the steering force of the driver is reduced by transmitting the power to the steering wheel via the output shaft portion 1B, the connecting portion 3, and the like.

Reference numeral 7 denotes a rotation sensor provided on the induction motor 5. The rotation sensor 7 detects the rotation speed at which the output shaft of the induction motor 5 is actually rotated, and outputs the detection result to the motor rotation speed (angular speed) ω. _This is output to the control unit 13 as _m .

Reference numeral 8 denotes a vehicle speed sensor which constitutes driving state detecting means together with a braking force sensor 9 described later. The vehicle speed sensor 8 detects the running speed (vehicle speed) of the vehicle and outputs a vehicle speed signal V to the control unit 13.

Reference numeral 9 denotes a braking force sensor as a deceleration state detecting means for detecting a deceleration state (braking state) of the vehicle. The braking force sensor 9 is, for example, an acceleration sensor for detecting a negative acceleration applied to the vehicle, a deceleration sensor. And a brake fluid pressure sensor for detecting the brake fluid pressure of the vehicle.
The braking force sensor 9 is controlled by the control unit 13
The braking signal B is output to

Reference numerals 10, 11, and 12 denote, for example, 3 as drive signal detecting means provided on the output side of the motor drive circuit 16.
Current sensors 10, 11, and 12
The actual currents i _U , i _V , which are actually output from the motor drive circuit 16 to the respective phases of the induction motor 5 as three-phase AC drive signals
The value of i _W is individually detected, and these detection signals are output to the control unit 13.

Reference numeral 13 denotes a control unit constituted by a microcomputer or the like. The control unit 13 is a storage unit 1 comprising, for example, a ROM and a RAM.
3A. The storage unit 13A stores various data including data maps 22 and 26 shown in FIGS.
The motor control processing programs shown in FIGS. 6 and 7 are stored in advance.

The control unit 13 is connected to a torque sensor 4, a rotation sensor 7, a vehicle speed sensor 8, a braking force sensor 9, current sensors 10, 11, 12 and the like on its input side, and has an output side to be described later. The motor drive circuit 16, the drive circuit cut-off relay 17, the warning light 18, and the like are connected.
The control unit 13 is turned on when the ignition switch 14 of the vehicle is closed (ON). At the time of turning on the power, the control unit 13 closes the drive circuit cut-off relay 17 to connect the battery 15 to the motor drive circuit 16. It is configured to supply power.

The control unit 13 calculates a target torque command value Ts according to, for example, a driver's steering force, a vehicle driving state, etc., as shown in a control block diagram in FIG. The target torque current command value It and the target excitation current command value IΦ corresponding to the value Ts are calculated as DC command signals, and the command signals are converted into three-phase AC current command values I _U , I _V , and I _W. Output to the motor drive circuit 16 so that the induction motor 5
Is controlled in accordance with the driver's steering force or the like.

The control unit 13 outputs a control signal En for controlling the operation and stop of the motor drive circuit 16, and when the output state of the drive signal output from the motor drive circuit 16 is determined to be abnormal as described later, , The motor drive circuit 16 is stopped to cut off the power supply (drive signal) to the induction motor 5.

Reference numeral 16 denotes a motor drive circuit provided on the output side of the control unit 13;
Is constituted by, for example, a PWM inverter using a plurality of transistors (not shown). A drive circuit cut-off relay 17 that is opened and closed by the control unit 13 is provided between the motor drive circuit 16 and the battery 15.

Then, the motor drive circuit 16 receives the power from the battery 15 and
It generates real currents i _U , i _V , i _W of phase alternating current, and outputs these currents as drive signals to each phase of the induction motor 5. Further, the motor drive circuit 16 operates and stops according to the signal value of the control signal En output from the control unit 13, and the like.

Reference numeral 18 denotes a warning light provided in, for example, a driver's cab of the vehicle.
When the output state of the induction motor 5 is determined to be abnormal, the light is turned on to notify the driver or the like of the abnormality.

Next, a motor control process by the control unit 13 will be described with reference to a control block diagram shown in FIG.

Numeral 21 denotes a torque command value calculation unit as a torque command value calculation means for calculating a target torque command value Ts to be output from the induction motor 5.
The target corresponding to the steering force of the driver, the driving state of the vehicle, and the like is determined using the steering torque signal To, the vehicle speed signal V, and the braking signal B output from the torque sensor 4, the vehicle speed sensor 8, and the braking force sensor 9, respectively. This is for calculating the torque command value Ts.

For this reason, as shown in FIG. 3, the torque command value calculating section 21 has a torque data map 22 corresponding to the running speed and the deceleration state of the vehicle.
2 is a plurality of types corresponding to, for example, a characteristic line 22a for normal traveling, a characteristic line 22b for low-speed traveling, a characteristic line 22c for high-speed traveling, a characteristic line 22d for normal deceleration, and a characteristic line 22e for rapid deceleration. It contains data.

For example, when the vehicle is traveling at the normal speed, the target torque command value Ts is calculated from the data of the characteristic line 22a for the normal running in accordance with the steering torque signal To, and the calculated value is determined by the driver. The size corresponds to the steering force.

When the vehicle is stopped or running at a low speed, the target torque command value Ts is calculated from the data on the characteristic line 22b for the low speed running in accordance with the steering torque signal To, and the calculated value is used for the normal running. Is larger than when the characteristic line 22a is used. This makes it possible to reduce the driver's steering force even when the steering force required for the steering operation increases due to frictional resistance from the wheels, for example, when the vehicle is stopped.

When the vehicle is traveling at high speed, the target torque command value Ts is calculated from the data of the characteristic line 22c for high-speed traveling, and the calculated value is smaller than when the characteristic line 22a for normal traveling is used. Become. As a result, when the vehicle is running at high speed, the output torque of the induction motor 5 with respect to the steering force is suppressed, and the driver can be given a moderately heavy steering wheel operation feeling to ensure the running stability of the vehicle.

On the other hand, for example, when the vehicle is decelerating while traveling at the normal speed, the target torque command value Ts is calculated from the data of the characteristic line 22d for the normal deceleration, and the calculated value is the characteristic for the normal traveling. It is larger than when the line 22a is used. When the vehicle is suddenly decelerated due to, for example, sudden braking of the driver, the characteristic line 2 for rapid deceleration is used.
2e, the target torque command value Ts is calculated as a larger value.

As a result, the steering force of the driver can be reduced even when a load is applied to the steering wheels during deceleration of the vehicle, resulting in an increased steering feeling. Also,
Characteristic line 22b for low-speed running, characteristic line 22c for high-speed running
, Characteristic lines (not shown) for deceleration and rapid deceleration are respectively set in advance.

Reference numeral 23 denotes a command signal calculation unit for calculating a command signal using the target torque command value Ts and the like. The command signal calculation unit 23 controls the output torque of the induction motor 5 to match the target torque command value Ts. The output state is variably controlled by means such as vector control. In this vector control, control of the induction motor 5 is virtually treated as control of a DC motor, and two DC current components, a target excitation current command value IΦ and a target torque current command value, are used to control the output torque. It is calculated as a command signal.

Here, if the magnetic flux generated by the stator of the induction motor 5 and interlinking with the rotor (both not shown) is assumed to be the interlinkage magnetic flux Φr, the current component contributing to the interlinkage magnetic flux Φr Corresponds to the target excitation current command value IΦ.

The target exciting current command value IΦ is stored in the storage unit 13 of the control unit 13 as a standard value according to, for example, the design specifications of the induction motor 5 and the motor drive circuit 16.
A coefficient k determined in accordance with the linkage magnetic flux Φr previously stored in A and the mutual inductance between the stator and the rotor.
1 and is calculated by the following equation (1).

[0057]

## EQU1 ## IΦ = k1 × Φr

The target torque current command value It corresponds to a current component contributing to the output torque of the induction motor 5. The target torque current command value It uses the target torque command value Ts, the linkage flux Φr, and the coefficient k2 to obtain the following equation (2). Is calculated by the following equation.

[0059]

(Equation 2)

The coefficient k2 is a constant determined in advance according to, for example, the number of pole pairs of the induction motor 5, the self-inductance of the rotor, the mutual inductance, and the like. The target excitation current command value IΦ and the target torque current command value It are:
Actual current i detected by current sensors 10, 11, 12
_U, i _V, by a command signal operation unit 23 by using the i _W, etc. are intended to be feedback-controlled.

On the other hand, the command signal calculator 23 calculates the slip frequency ω _SE corresponding to the frequency difference between the frequency of the drive signal (power supply frequency ω) and the rotation frequency of the induction motor 5 by using the target torque current command value It and the linkage The calculation is performed using the magnetic flux Φr and the coefficient k3 according to the following equation (3). Here, the coefficient k3 is a constant determined in advance according to, for example, the resistance and the self-inductance of the rotor, the mutual inductance, and the like.

[0062]

(Equation 3)

Using the slip frequency ω _SE and the motor rotation speed ω _m detected by the rotation sensor 7, the command signal calculation unit 23 calculates the power supply frequency ω
And the power supply frequency ω is determined by the target excitation current command value I
Φ and the frequency of the target torque current command value It.

[0064]

[Equation 4] ω = ω _m + ω _SE

Reference numeral 24 denotes a signal converter for converting a command signal.
The signal converter 24 converts the DC command signal into a three-phase AC signal and outputs the converted signal. The DC target excitation current command value IΦ and the target torque current command value It are obtained by dividing these DC components by two. According to the following equation (5), which is regarded as a three-phase AC component and is converted into a three-phase AC component, the frequency becomes the power supply frequency ω and the current command value I of the three-phase AC having a phase difference of 120 °
_U , _IV and _IW are converted.

[0066]

(Equation 5)

In this case, the angle θ in the equation (5) is an electrical phase angle (electrical angle), which is obtained by time-integrating the power supply frequency ω.

The signal conversion unit 24 outputs, for example, a pulse
The current command value I is obtained by means such as width modulation (PWM)._U , I
_V , I_W Generates three-phase AC voltage signals corresponding to
And outputs these voltage signals to the motor drive circuit 16.
You. As a result, the current command value I
_U , I_V , I_W Current i of three-phase alternating current corresponding to_U , I
_V , I _W Is output, the induction motor 5
Output according to command value Ts (target torque current command value It)
The torque is generated as an auxiliary steering force.

That is, in the vector control of the induction motor 5,
The target excitation current command value IΦ (linkage magnetic flux Φr), the target torque current command value It, and the slip frequency ω _SE are adjusted by adjusting the power supply frequency ω of the drive signal and the like so as to satisfy the above equations (3) and (4). The output torque T of the induction motor 5 can be controlled according to the target torque current command value It.

On the other hand, reference numeral 25 denotes an upper limit data storage unit as upper limit data storage means constituted by a part of the storage unit 13A of the control unit 13, and the upper limit data storage unit 25 stores the upper limit data as shown in FIG. An upper limit data map 26 is stored in advance as upper limit data for calculating a determination value Li described below according to the traveling speed and the deceleration state of the vehicle.

Here, the output torque of the induction motor 5 is
As described above, the actual current i of the drive signal_U , I _V , I_W To the sum of squares of
The upper limit value data map 26
Determines the upper limit value of the sum of squares, the determination value Li.
By setting according to the state, the output of the induction motor 5
This prevents the torque from becoming excessive.

The upper limit value data map 26 includes, for example, a characteristic line 26a for normal running, a characteristic line 26b for deceleration,
It includes a plurality of types of data corresponding to the characteristic line 26c for rapid deceleration and the like. Also, the characteristic line 2 for normal running
6a is a low-speed characteristic line section 26 corresponding to low-speed running of the vehicle.
a1 and an intermediate vehicle speed characteristic line portion 26a corresponding to the intermediate vehicle speed
2 and a high-speed characteristic line portion 26a3 corresponding to high-speed running. The characteristic lines 26b and 26c for deceleration and rapid deceleration are configured in substantially the same manner as the characteristic line 26a.

In this case, the upper limit value data map 26 can be expressed by the following equation (6) using a function that determines the determination value Li according to the vehicle speed signal V and the braking signal B.

[0074]

Equation 6: Li = f (V, B)

The characteristic line 26a for normal traveling corresponds to the normal traveling (non-deceleration) state of the vehicle.
judgment value Li _a by a can be expressed as the following equation Equation 7.

[0076]

[Expression 7] Li _a = f _a (V)

In this case, among the characteristic lines 26a, the low-speed characteristic line portion 26a1 corresponds to the low-speed traveling characteristic line 22b of the torque data map 22, and the intermediate vehicle speed characteristic line portion 26a2.
Is a characteristic line 22a for the normal driving of the torque data map 22.
The high-speed characteristic line portion 26a3 corresponds to the high-speed running characteristic line 22c of the torque data map 22.

The characteristic line 26b for deceleration is a normal
This characteristic corresponds to the deceleration state of the vehicle due to rake operation etc.
Determination value Li based on line 26b_b Is the torque data
Corresponding to the characteristic line 22d for normal deceleration of the
Set to the value (Li_b > Li _a ), As shown in equation 8 below
Can be expressed as

[0079]

## EQU8 ## Li _b = f _b (V)

[0080] Further, the characteristic line 26c for rapid deceleration corresponds to the state of rapid deceleration of the vehicle due to sudden braking or the like, the determination value Li _c according to the characteristic line 26c, for example, the characteristic line for the rapid deceleration of the torque data map 22 The value is set to a larger value corresponding to 22e (Li _c > Li _b ), and can be represented by the following equation (9).

[0081]

Equation 9: Li _c = f _c (V)

Assuming that a boundary between the low speed and the medium speed with respect to the vehicle speed signal V is a boundary value V1 in FIG. 4 and a boundary between the medium speed and the high speed is a boundary value V2, for example, the characteristic line 26a shows these boundary values V1 , V2 and the vehicle speed signal V are set according to the following equation (10).

[0083]

F _a1 (V) = H _a (0 <V ≦ V 1) f _a2 (V) = − α × V + β (V 1 <V ≦ V 2) f _a3 (V) = L _a (V 2 <V) , H _a, L _a: set value _{(L a <H a) α} , β: constants

The other characteristic lines 26b and 26c are also set so that the characteristics change in accordance with the vehicle speed signal V, substantially in the same manner as in the equation (10).

As a result, if the drive signal becomes excessively large as compared with the operation state of the vehicle due to, for example, an abnormality of the motor drive circuit 16, the judgment value Li calculated from the upper limit value data map 26 is used. The configuration is such that an abnormality in the drive signal can be detected at an arbitrary vehicle speed and deceleration state.

Reference numeral 27 denotes a judgment value calculation unit as judgment value calculation means. The judgment value calculation unit 27 uses the vehicle speed signal V from the vehicle speed sensor 8 and the braking signal B from the braking force sensor 9 to calculate
The judgment value Li is calculated from the upper limit value data map 26 in FIG.

Then, for example, when the vehicle is not in a deceleration state,
When the normal running state is maintained, the determination value Li is calculated from the normal running characteristic line 26a according to the vehicle speed signal V. At this time, when the vehicle is running at low speed, the low speed characteristic line portion 26a1 is used. The judgment value Li is set to a large value, and the judgment value Li is set to a small value using the high-speed characteristic line portion 26a3 during high-speed running.

Further, for example, when the vehicle is decelerated by a normal brake operation or the like, the judgment value Li is set to be large by the deceleration characteristic line 26b. Further, when the vehicle is suddenly decelerated due to sudden braking of the driver or the like, the determination value Li is set to be larger by the rapid deceleration characteristic line 26c.

Reference numeral 28 denotes a signal judging unit as signal judging means. The signal judging unit 28 comprises the actual currents i _U , i
_V and i _W are detected by the current sensors 10, 11 and 12, and the sum of squares Ir ² of the drive signal is calculated by using the detected values according to the following equation (11).

[0090]

[Equation 11] Ir ² = i _U ² + i _V ² + i _W ²

The signal determination unit 28 determines whether the output state of the drive signal is normal or not by comparing the sum of squares Ir ^{2 of the} drive signal with the determination value Li, as described later. When it is determined that the output torque is excessive, the driver is notified of an abnormality by a fail-safe process or the drive signal to the induction motor 5 is stopped to prevent the output torque from becoming excessive.

Here, the relationship between the output torque of the induction motor 5 and the sum of squares Ir ² of the drive signal will be described. First, the output torque T 'can be expressed as a general equation as in the following equation (12).

[0093]

(Equation 12) Here, P: the number of pole pairs of the induction motor 5 M: mutual inductance between the stator and the rotor Lr: self-inductance of the rotor i _1s : γ-axis component of stator current i _2s : δ-axis component of stator current Φ _1r : γ-axis component of linkage flux Φr Φ _2r : δ-axis component of linkage flux Φr

In this case, the γ axis and the δ axis correspond to the power frequency ω
Is an orthogonal axis in a rotating coordinate system rotating with. Also,
The following _equation 1 is provided between the currents i _1s , i _2s and the magnetic fluxes Φ _1r , Φ _2r.
3. The state equation shown by the equation 14 is established.

[0095]

(Equation 13) Here, Rr: resistance of the rotor ω _SE : slip frequency

[0096]

[Equation 14]

When the induction motor 5 is driven, the control unit 13 keeps the flux linkage Φr (the target excitation current command value IΦ) at a substantially constant value.
Equation 5 holds.

[0098]

(Equation 15)

As a result, the expressions (13), (14) and (1)
Using the equation (5), the magnetic flux Φ _1r and Φ _2r are given by
Equation (17) can be derived.

[0100]

(Equation 16)

[0101]

[Equation 17]

Then, the equations of the equations (16) and (17) are
By substituting into the equation (12), the output torque T ′
The following equation (18) can be obtained.

[0103]

(Equation 18)

Here, the currents i _1s and i _2s are
Are expressed as current components along the γ-axis and δ-axis of the rotating coordinate system, and when the induction motor 5 is driven, the stator currents are the three-phase AC actual currents i _U , i _V , i
Given as _W. Therefore, between these currents,
Similarly to the equation (5), the following equation (19) representing the relationship between the DC component and the three-phase AC component is established.

[0105]

[Equation 19]

From the equation (19), the following equation (20) relating to the sum of squares of the current value can be derived.

[0107]

[Equation 20] i _U ² + i _V ² + i _W ² = i _1s ² + i _2s ²

By substituting the equation (20) into the equation (18), the following equation (21) can be obtained.

[0109]

(Equation 21)

As a result, the relationship between the output torque T ′ and the slip frequency ω _SE according to the equation (21) is as shown by the characteristic line in FIG. 5 with the driving signal held at a constant value.
The slip frequency ωmax that gives the maximum value Tmax of the output torque
Is given by the following equation (22) by finding a point where (∂T / ∂ω _SE ) = 0 from the equation (21).

[0111]

(Equation 22)

[0112] Then, by substituting the slip frequency ωmax as an expression in the slip frequency omega _SE of the number 21, the maximum value of the output torque relative to the slip frequency omega _SE Tma
x can be calculated, and the maximum value Tmax can be used as the output torque T to derive the following equation (23).

[0113]

(Equation 23)

Thus, the output torque T of the induction motor 5
Is the square sum Ir ² of the actual currents i _U , i _V , i _W of the drive signal.
It can be understood that it is approximately proportional to the following equation.

[0115]

[Equation 24] T∝Ir ²

Therefore, the signal judging section 28 judges that the driving signal 2
By comparing and determining the sum of the products Ir ² and the determination value Li,
It is possible to prevent the output torque T of the induction motor 5 from becoming excessive due to the output abnormality or the like.

The power steering apparatus according to the present embodiment is configured as described above. Next, the motor control processing by the control unit 13 will be described with reference to FIG.

First, in step 1, the steering torque signal To from the torque sensor 4, the vehicle speed signal V from the vehicle speed sensor 8, the braking signal B from the braking force sensor 9, etc. are read, and in step 2, these detection signals are read. Is used to calculate the target torque command value Ts from the torque data map 22. Thereby, the target torque command value Ts is set to a value corresponding to the steering force when the driver performs the steering operation of the steering wheel 2, the running state of the vehicle, the load state of the steering wheel, and the like.

In step 3, the target excitation current command value IΦ is calculated by the equation (1) using the stored value of the linkage flux Φr and the like. In step 4, the target torque command value Ts, the linkage flux Φr and the like are calculated. Then, the target torque current command value It is calculated by the equation (2). In step 5, the slip frequency ω _SE is calculated by the equation (3) using the target torque current command value It, the linkage flux Φr, and the like.

[0120] In step 6, the motor rotation speed omega _m detected by the rotation sensor 7, the current sensor 10,11,1
The actual currents i _U , i _V , and i _{W of} the drive signal detected in step 2 are read, and in step 7, the power supply frequency ω of the command signal is higher than the motor rotation speed ω _m by the slip frequency ω _SE . The power supply frequency ω is calculated by the equation (4).

At step 8, the DC target current command value I
Φ and It are converted into three-phase AC current command values I _U , I _V , and I _W by the above equation (5), and in step 9 these are output to the motor drive circuit 16 to drive the induction motor 5. .

In step 10, a drive signal determination process described later is performed. In step 11, it is determined whether or not the ignition switch 14 is open (OFF).
If the determination is "S", the motor control process ends at step 12 because the engine of the vehicle is stopped. Also,
If "NO" is determined in the step 11, the process returns to the step 1, and the motor control process is continued.

Next, the drive signal determination process in FIG. 6 will be described with reference to FIG. 7. First, in step 21, the above-mentioned values are calculated using the actual currents i _U , i _V and i _W detected in step 6. The sum of squares Ir ² of the drive signal is calculated by the equation (11). Then, in step 22, the determination value Li is calculated by the upper limit data map 26 using the vehicle speed signal V and the braking signal B.

In step 23, the square sum Ir of the drive signal
^It is determined whether or not ² is larger than the determination value Li. When it is determined "NO" in step 23, the drive signal has a magnitude corresponding to the driving state of the vehicle, so that the output state is determined to be normal, and step 24 is performed.
Now, the counter C for measuring the duration of the output abnormality
Is cleared to zero, and the routine returns in step 25.

When the determination in step 23 is "YES", the output signal state is large because the magnitude of the drive signal is excessive compared to the operation state of the vehicle due to, for example, a failure of the motor drive circuit 16. It is determined that there is an abnormality, and the routine proceeds to step 26.

In step 26, the counter C is incremented by "1". In this case, the drive signal determination process
Since it is repeatedly executed at regular time intervals together with the motor control processing shown in FIG. 6, the value of the counter C increases according to the duration of the output abnormality.

In step 27, it is determined whether or not the counter C has exceeded a predetermined determination value C0. When the determination is "NO", for example, a case where the drive signal becomes momentarily excessive due to noise or the like is considered. Then, step 28 described later
Without performing the fail-safe processing described above.

If "YES" is determined in the step 27, the output abnormality of the drive signal has continued for a certain period of time, so that the fail-safe process is performed in the step 28.

In step 28, the induction motor 5
The control signal En for stopping the signal is output to the motor drive circuit 16 or the drive circuit cut-off relay 1
7, the power supply (drive signal) from the motor drive circuit 16 to the induction motor 5 is stopped. In addition, a warning light 18
Is turned on to warn the driver or the like of the abnormality of the motor drive circuit 16, and the process returns in step 25.

Thus, according to the present embodiment, control unit 13 includes upper limit data storage unit 25 storing upper limit data map 26 and upper limit data map 2.
Judgment value calculation unit 2 for calculating a judgment value Li of the drive signal from the control signal 6
7, and a signal determination unit 28 that determines whether the output state of the drive signal is normal using the determination value Li.

As a result, the upper limit value data map 26 for determining the output state of the drive signal can be stored in the upper limit value data storage unit 25 in advance. The determination value Li of the drive signal corresponding to the driving state of the vehicle can be easily calculated from the data map 26.

If the drive signal becomes excessively large compared to the driving state of the vehicle due to, for example, an abnormality in the motor drive circuit 16, the signal determination unit 28 calculates the sum of squares Ir ^{2 of the} drive signal and the determination value Li. By comparing with the above, it is possible to reliably determine the output abnormality of the drive signal, and to perform a fail-safe process such as turning on the warning light 18 or stopping the drive signal using the drive circuit cut-off relay 17 or the like. .

In addition, the prior art merely compares the cycle (polarity reversal time) between the AC signal obtained by converting the command signal and the drive signal. On the other hand, in the present embodiment, the output torque of the induction motor 5 is reduced. It is possible to directly compare the magnitude of the sum of squares Ir ² of the drive signal substantially corresponding to the magnitude of T with the determination value Li. As a result, it is possible to reliably prevent the output torque T of the induction motor 5 from becoming excessive with respect to the driver's steering force, and it is possible to improve reliability and safety as compared with the related art.

Further, since the determination value Li of the drive signal is set as the upper limit data map 26 including a plurality of types of data corresponding to the traveling speed and the deceleration state of the vehicle, the determination value calculation unit 27 sets the vehicle speed sensor The determination value Li can be calculated from the upper limit data map 26 using the vehicle speed signal V from the vehicle speed signal 8 and the braking signal B from the braking force sensor 9. Can be changed with substantially the same characteristics as the drive signal.

As a result, during the operation of the vehicle, the judgment value Li corresponding to the operation state can always be appropriately calculated, and even if the drive signal becomes excessive at an arbitrary vehicle speed and deceleration state, this output abnormality is judged. It can be detected stably by the value Li.

The torque command value calculating section 21 uses the steering torque signal To, the vehicle speed signal V and the braking signal B output from the torque sensor 4, the vehicle speed sensor 8 and the braking force sensor 9 to set the target torque command value Ts. Is calculated, the output torque of the induction motor 5 can be controlled in accordance with the steering force of the driver, and the output torque is appropriately adjusted in accordance with the running state of the vehicle, the load state of the steering wheels, and the like. As a result, it is possible to improve the driver's steering operation feeling as compared with the related art.

That is, when the vehicle is running at low speed, the steering operation can be smoothly performed against the frictional resistance force from the wheels by increasing the target torque command value Ts. By reducing the value Ts, the steering operation of the vehicle can be appropriately suppressed, and the running stability can be increased. In addition, when the driver operates the brake, by increasing the target torque command value Ts, the steering wheel operation feeling can be favorably maintained against the load on the steering wheel.

In the embodiment, step 22 shown in FIG. 7 shows a specific example of the judgment value calculating means.
Reference numeral 3 denotes a specific example of the signal determination means. Step 28 shows a specific example of the fail-safe means.

In the embodiment, the determination value Li is calculated according to the traveling speed and the deceleration state of the vehicle using the upper limit data map 26 stored in the upper limit data storage unit 25 in advance. However, the present invention is not limited to this. For example, as in a modified example shown in FIG.

In this case, the upper limit data map 31 includes, for example, a characteristic line group 31a when the driver's steering force is small,
It has a characteristic line group 31b when the steering force is medium and a characteristic line group 31c when the steering force is large, and these characteristic line groups 31a, 31b, 31c are respectively used for normal running, deceleration, and sudden. While being constituted by the characteristic line for deceleration,
The determination value calculator 27 may be configured to calculate the determination value Li from the upper limit data map 31 according to the steering torque signal To, the vehicle speed signal V, and the braking signal B.

In the embodiment, for example, three current sensors 10, 11, and 12 are used to output a three-phase AC real current i.
_U, i _V, but i _W were respectively configured to detect separately, the invention is not limited to this, the drive signal detecting means, actual current i _U by two current sensors, i _V, among the i _W The actual current of any two phases may be detected, and the actual current of the other one phase may be estimated and calculated from the following equation (25) showing the characteristics of three-phase alternating current.

[0142]

## EQU25 ## i _U + i _V + i _W = 0

Further, in the embodiment, the linkage flux Φr and the target exciting current command value IΦ are configured to be kept at constant values. However, the present invention is not limited to this, and the present invention is not limited to this. Resistance loss and linkage flux Φr and target excitation current command value IΦ
A configuration may be adopted in which the flux linkage Φr, the target excitation current command value IΦ, and the like are corrected and controlled in accordance with a response delay between them.

[0144]

As described in detail above, according to the first aspect of the present invention, the judgment value calculation means calculates the judgment value for the drive signal using the upper limit data stored in the upper limit data storage means, The signal determination means is configured to determine the output state of the drive signal by comparing the output value of the drive signal detected by the drive signal detection means with the determination value, so that the upper limit data storage means stores the upper limit value for the drive signal. The data can be stored in advance, and the determination value calculating means can easily calculate the determination value corresponding to the driving state of the vehicle from the upper limit data. The signal determination means can directly compare the magnitude of the determination value with the output value of the drive signal. For example, when the drive signal becomes abnormal as compared with the operation state of the vehicle due to a failure of the motor drive circuit or the like. Can reliably determine this output abnormality and can stop the drive signal to the induction motor, for example. Therefore, it is possible to reliably prevent the output torque of the induction motor from becoming too large or too small with respect to the driver's steering force, and it is possible to improve reliability and safety as compared with the related art.

According to the second aspect of the present invention, the upper limit data storage means stores a plurality of types of upper limit data according to the traveling speed of the vehicle, and the determination value calculation means outputs a detection signal from the vehicle speed sensor. The determination value is calculated from each upper limit value data by using the configuration. For example, when the drive signal is changed according to the vehicle speed by normal motor control, the determination value of the drive signal according to the vehicle speed is determined by the determination value calculation means. Can always be appropriately calculated, and the output abnormality can be stably detected during driving of the vehicle even if the drive signal becomes abnormal at an arbitrary vehicle speed.

According to the third aspect of the present invention, the upper limit data storage means stores a plurality of types of upper limit data according to the traveling speed and the deceleration state of the vehicle.
Since the determination value is calculated from each upper limit value data using the detection signal from the vehicle speed sensor and the deceleration state detection means,
For example, when the drive signal is changed according to the vehicle speed and the deceleration state by normal motor control, the determination value of the drive signal according to the driving state of the vehicle can always be appropriately calculated by the determination value calculation means, During driving, even if the drive signal becomes abnormal at an arbitrary vehicle speed and deceleration state, this output abnormality can be stably detected.

Further, according to the invention of claim 4, since the deceleration state detecting means is constituted by the braking force sensor, for example, the braking force applied to the vehicle at the time of the brake operation can be detected by the braking force sensor. The determination value of the drive signal can be appropriately calculated according to the traveling speed of the vehicle and the deceleration state due to the brake operation.

According to the fifth aspect of the present invention, the torque command value calculating means is configured to calculate the torque command value in accordance with the driving state of the vehicle and the steering force detected by the driving state detecting means. The output torque of the induction motor can be appropriately controlled by the torque command value calculating means in accordance with the driver's steering force and the driving state of the vehicle, and the steering feel can be improved as compared with the prior art.

According to the invention of claim 6, the signal determination means calculates the sum of squares of each current value of the drive signal from the detection result of the current sensor, and uses the sum of squares as the output value of the drive signal. With this configuration, the signal determination means can calculate the sum of squares of the respective current values substantially corresponding to the magnitude of the output torque of the induction motor as the output value of the drive signal. Is compared to make an abnormality determination, it is possible to prevent the output torque of the induction motor from becoming too large or too small with respect to the driver's steering force.

Further, according to the invention of claim 7, the signal judging means judges that the drive signal is abnormal when the output value of the drive signal exceeds the judgment value. If the output becomes excessive compared with the driving state of the vehicle, the output abnormality can be reliably determined, and the reliability and safety can be improved.

Further, according to the invention of claim 8, when the output state of the drive signal is determined to be abnormal by the signal determination means, the failure signal is notified or the drive signal is stopped. At the time of the abnormality determination by the signal determination means, the failure safe means can notify the driver of the vehicle of the abnormality or stop the drive signal to the induction motor, thereby improving reliability and safety.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a power steering device according to an embodiment of the present invention.

FIG. 2 is a control block diagram illustrating a motor control process performed by a control unit.

FIG. 3 is a characteristic diagram showing a relationship between a steering torque signal and a target torque command value.

FIG. 4 is a characteristic diagram of upper limit data indicating a relationship between a determination value of a drive signal and a vehicle speed.

FIG. 5 is a characteristic diagram showing a relationship between an output torque by an induction motor and a slip frequency.

FIG. 6 is a flowchart showing a motor control process by a control unit.

FIG. 7 is a flowchart showing a drive signal determination process in FIG. 6;

FIG. 8 is a characteristic diagram showing an upper limit value data map according to a modification of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steering axis 2 Steering handle 3 Connecting part 4 Torque sensor 5 Induction motor 6 Reduction gear 7 Rotation sensor 8 Vehicle speed sensor (driving state detecting means) 9 Braking force sensor (Deceleration state detecting means) 10, 11, 12 Current sensor (Drive) 13 signal control means 14 ignition switch 15 battery 16 motor drive circuit 17 drive circuit cut-off relay 18 warning light 21 torque command value calculation section (torque command value calculation means) 23 command signal calculation section 24 signal conversion section 25 upper limit value data Storage unit (upper limit value data storage unit) 26, 31 Upper limit value data map (upper limit value data) 27 Judgment value operation unit (judgment value operation unit) 28 Signal judgment unit (signal judgment unit)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D032 CC34 CC40 DA03 DA15 DA23 DA64 DA93 DB01 DB10 DC08 DC33 DD01 DD06 EA01 EB12 EC23 FF01 3D033 CA03 CA13 CA16 CA20 CA21 CA27 CA31 CA33

Claims (8)

[Claims] An induction motor for generating an assisting steering force for assisting a steering force, and a torque command value calculation for calculating a target torque command value corresponding to at least the steering force for controlling an output torque of the induction motor. And a motor drive circuit for outputting a drive signal corresponding to the target torque command value calculated by the torque command value calculation means to the induction motor, wherein a driving state for detecting a driving state of the vehicle is provided. Detection means, drive signal detection means for detecting a drive signal output from the motor drive circuit to the induction motor, and upper limit value data storage means for storing upper limit value data for determining an upper limit of the output state of the drive signal And a judgment value for calculating a judgment value from the upper limit data in the upper limit data storage means according to the driving state of the vehicle detected by the driving state detection means. And San means,
A signal determination unit configured to compare an output value of the drive signal detected by the drive signal detection unit with a determination value by the determination value calculation unit to determine whether an output state of the drive signal is normal; A power steering device, characterized in that: 2. The driving state detecting means comprises a vehicle speed sensor for detecting a running speed of the vehicle, and the upper limit data storing means stores a plurality of types of upper limit data corresponding to the running speed of the vehicle. The power steering device according to claim 1, wherein the calculation means is configured to calculate a determination value from each of the upper limit value data using a detection signal output from the vehicle speed sensor. 3. The driving state detecting means includes a vehicle speed sensor for detecting a traveling speed of the vehicle, and a deceleration state detecting means for detecting a decelerating state of the vehicle. A plurality of types of upper limit value data corresponding to the deceleration state are stored, and the determination value calculation means calculates a determination value from each of the upper limit value data using detection signals respectively output from the vehicle speed sensor and the deceleration state detection means. The power steering device according to claim 1, wherein the power steering device is configured to perform the following. 4. The power steering apparatus according to claim 3, wherein said deceleration state detecting means comprises a braking force sensor for detecting a braking force of the vehicle. 5. The vehicle according to claim 1, wherein said torque command value calculating means calculates said torque command value according to a driving state and a steering force of the vehicle detected by said driving state detecting means. 5. The power steering device according to 4. 6. The motor drive circuit outputs a three-phase AC current signal to the induction motor as the drive signal, and the drive signal detecting means outputs a current value of at least two phases of the three-phase AC current signal. , And the signal determination means squares and adds the three-phase current values of the drive signal obtained from the detection result of the current sensor to obtain the square of each current value. 3. A configuration for calculating a sum as an output value of the drive signal.
The power steering device according to 3, 4, or 5. 7. A configuration in which the signal determination means determines that the drive signal is normal when the output value of the drive signal is equal to or less than the determination value, and determines that the drive signal is abnormal when the output value of the drive signal exceeds the determination value. The power steering device according to claim 1, 2, 3, 4, 5, or 6, wherein 8. A system according to claim 1, further comprising fail-safe means for notifying the abnormality or stopping the drive signal to said induction motor when said signal determination means determines that the output state of said drive signal is abnormal. , 3, 4, 5, 6 or 7.