JP6401637B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

In recent years, in an electric power steering apparatus that assists a driver's steering force with the power of an electric motor, even when the detection means (torque sensor) that detects the steering torque cannot detect the steering torque, A technique that makes it possible to apply assist force has been proposed.
For example, the electric power steering device described in Patent Document 1 drives the motor based on the rotation angle detected by the resolver and the assist current characteristics when the abnormality of the torque sensor is detected by the abnormality detection unit. In this case, control is performed so that the assist current for driving the motor decreases as the rotation angular velocity calculated based on the rotation angle increases.

JP 2012-144100 A

When the assist force by the electric motor is determined based on the steering angle of the steering wheel when a failure occurs in the torque detection means (torque sensor), the dead zone region where the assist force is zero in the region where the steering angle is close to zero Can be set. This is because in the region where the steering angle is close to zero, it is considered that it is preferable not to apply the assist force in order to suppress the steering wobbling rather than to apply the assist force. For this reason, even if the driver steers the steering wheel to change the traveling direction, a steering force equivalent to zero assist force is required in the dead zone region, which places a heavy burden on the driver.
An object of the present invention is to provide an electric power steering apparatus that can suppress steering fluctuation and reduce a steering burden even when a failure occurs in a torque detection means.

For this purpose, the present invention relates to an electric motor for applying an assisting force to steering of a steering wheel of a vehicle, torque detecting means for detecting a steering torque of the steering wheel, and a rotation angle of the steering wheel. A steering angle estimating means for estimating a steering angle; a failure detecting means for detecting a failure of the torque detecting means; and when the failure detecting means detects no failure , based on the steering torque detected by the torque detecting means. When the failure detecting means detects a failure, the electric motor increases the assist force as the differential value of the estimated steering angle estimated by the steering angle estimating means increases. and a control means for controlling, the control unit, when said failure detecting means detects failure, based on the estimated steering angle A value obtained by adding the first assist current determined in this step and the second assist current determined based on the differential value of the estimated steering angle is determined as the assist current of the electric motor, and the estimated steering angle is predetermined. In the electric power steering apparatus, the first assist current is determined to be zero when the steering angle is smaller than a predetermined steering angle .

Here, the control means may correct the second assist current to be smaller when the estimated steering angle is large than when the estimated steering angle is small.

  According to the present invention, even when a failure occurs in the torque detection means, it is possible to suppress steering fluctuation and reduce the steering burden.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of a control apparatus. It is a schematic block diagram of a target current calculation part. It is the schematic of the control map which shows a response | compatibility with steering torque, vehicle speed, and base current. It is a schematic block diagram of a control part. It is a schematic block diagram of the current determination part at the time of a sensor failure. It is a schematic block diagram of the base current calculation part at the time of a sensor failure. It is the schematic of the control map which shows a response | compatibility with the steering angle after absolute value conversion, and a temporary sensor failure base current. It is the schematic of the control map which shows a response | compatibility with a vehicle speed correction coefficient and a vehicle speed. It is a schematic block diagram of a return correction coefficient setting part. It is the schematic of the control map which shows a response | compatibility with the steering angle after absolute value conversion, and a temporary return correction coefficient. It is the schematic of the control map which shows a response | compatibility with a motor rotational speed and a rotational speed correction coefficient. It is the schematic of the control map which shows a response | compatibility with a vehicle speed and a vehicle speed correction coefficient. It is the schematic of the control map which shows a response | compatibility with a steering angle differential value and a differential value electric current. It is the schematic of the control map which shows a response | compatibility with the absolute value of a calculated steering angle, and a steering angle correction coefficient. It is a figure which shows the relationship between the steering angle and steering force when a torque sensor fails.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
Electric power steering device 100 (hereinafter, also simply referred to as “steering device 100”) is a steering device for arbitrarily changing the traveling direction of a vehicle, and in this embodiment, an automobile as an example of the vehicle. 1 illustrates the configuration applied to 1.

  The steering device 100 includes a wheel-like steering wheel 101 that is operated by a driver to change the traveling direction of the automobile 1, and a steering shaft 102 that is provided integrally with the steering wheel 101. Yes. The steering device 100 includes an upper connecting shaft 103 connected to the steering shaft 102 via a universal joint 103a, and a lower connecting shaft 108 connected to the upper connecting shaft 103 via a universal joint 103b. . The lower connecting shaft 108 rotates in conjunction with the rotation of the steering wheel 101.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via the torsion bar 112 in the steering gear box 107. The steering gear box 107 has a steering torque T applied to the steering wheel 101 based on the relative rotation angle between the lower connecting shaft 108 and the pinion shaft 106, in other words, based on the twist amount of the torsion bar 112. A torque sensor 109 is provided as an example of torque detecting means for detecting the torque.

  Further, the steering device 100 includes an electric motor 110 supported by the steering gear box 107 and a speed reduction mechanism 111 that reduces the driving force of the electric motor 110 and transmits it to the pinion shaft 106. The speed reduction mechanism 111 includes, for example, a worm wheel (not shown) fixed to the pinion shaft 106, a worm gear (not shown) fixed to the output shaft of the electric motor 110, and the like. The electric motor 110 applies a driving force for rolling the front wheel 150 to the rack shaft 105 by applying a rotational driving force to the pinion shaft 106. The electric motor 110 according to the present embodiment is a three-phase brushless motor having a resolver 120 that detects the rotation angle of the electric motor 110.

  In addition, the steering device 100 includes a control device 10 that controls the operation of the electric motor 110. An output signal from the torque sensor 109 described above is input to the control device 10. In addition, the control device 10 includes a vehicle speed sensor that detects a vehicle speed Vc that is a moving speed of the automobile 1 via a network (CAN) that performs communication for sending signals for controlling various devices mounted on the automobile 1. An output signal from 170 or the like is input.

  The steering device 100 configured as described above drives the electric motor 110 based on the detected torque detected by the torque sensor 109 and transmits the generated torque of the electric motor 110 to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
FIG. 2 is a schematic configuration diagram of the control device 10.
The control device 10 is an arithmetic logic operation circuit including a CPU, a ROM, a RAM, an EEPROM (Electrically Erasable & Programmable Read Only Memory), and the like.
The control device 10 includes a torque signal Td obtained by converting the steering torque T detected by the torque sensor 109 described above into an output signal, and a vehicle speed signal obtained by converting the vehicle speed Vc detected by the vehicle speed sensor 170 into an output signal. v, a rotation angle signal θs that is an output signal corresponding to the motor rotation angle θ of the electric motor 110 from the resolver 120 is input.

  Then, the control device 10 calculates (sets) a target current It necessary for the electric motor 110 to supply based on the torque signal Td, the vehicle speed signal v, and the like, and a target current calculation unit 20. And a control unit 30 that performs feedback control or the like based on the target current It calculated by. Further, the control device 10 calculates a motor rotation speed Vm based on the motor rotation angle calculation unit 71 that calculates the motor rotation angle θ of the electric motor 110 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. A motor rotation speed calculation unit 72 to calculate and a steering angle calculation unit 73 to calculate a steering angle that is a rotation angle of the steering wheel 101 are provided.

Next, the target current calculation unit 20 will be described in detail.
FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 calculates a base current calculation unit 21 that calculates a base current Ib that serves as a reference for setting the target current It, and inertia compensation that calculates an inertia compensation current Is for canceling the inertia moment of the electric motor 110. A current calculation unit 22 and a damper compensation current calculation unit 23 that calculates a damper compensation current Id that limits the rotation of the motor are provided. Further, the target current calculation unit 20 determines a temporary target current Itf that is a temporary target current based on the values calculated by the base current calculation unit 21, the inertia compensation current calculation unit 22, and the damper compensation current calculation unit 23. A temporary target current determination unit 25 is provided. In addition, the target current calculation unit 20 includes a phase compensation unit 26 that compensates for the phase of the steering torque T detected by the torque sensor 109.

The target current calculation unit 20 also includes a sensor failure detection unit 27 as an example of a failure detection unit that detects a failure of the torque sensor 109, and the electric motor 110 when the sensor failure detection unit 27 detects a failure of the torque sensor 109. And a sensor failure current determination unit 28 as an example of a control means for calculating a current that is a basis of the target current It supplied to the sensor. The target current calculation unit 20 includes a final target current determination unit 29 that determines a target current It that is finally supplied to the electric motor 110.
The target current calculation unit 20 receives a torque signal Td, a vehicle speed signal v, a motor rotation speed signal Vms, and the like.

FIG. 4 is a schematic diagram of a control map showing the correspondence between the steering torque T, the vehicle speed Vc, and the base current Ib.
The base current calculation unit 21 calculates a base current Ib based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170. In other words, the base current calculation unit 21 calculates the base current Ib according to the steering torque T phase-compensated by the phase compensation unit 26 and the vehicle speed Vc. The base current calculation unit 21 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and base current that are created in advance based on empirical rules and stored in the ROM. The base current Ib is calculated by substituting the steering torque T and the vehicle speed Vc into the control map illustrated in FIG. 4 illustrating the correspondence with Ib.

  The inertia compensation current calculation unit 22 calculates the inertia compensation current Is based on the torque signal Ts and the vehicle speed signal v obtained by phase compensation of the torque signal Td by the phase compensation unit 26. In other words, the inertia compensation current calculation unit 22 calculates the inertia compensation current Is according to the steering torque T phase-compensated by the phase compensation unit 26 and the vehicle speed Vc. Note that the inertia compensation current calculation unit 22, for example, a phase-compensated steering torque T (torque signal Ts) and vehicle speed Vc (vehicle speed signal v) and inertia, which are created based on empirical rules and stored in the ROM in advance. The inertia compensation current Is is calculated by substituting the phase-compensated steering torque T and the vehicle speed Vc into the control map indicating the correspondence with the compensation current Is.

  The damper compensation current calculation unit 23 calculates the damper compensation current Id based on the torque signal Ts, the vehicle speed signal v, the motor rotation speed signal Vms, etc., in which the phase of the torque signal Td is compensated by the phase compensation unit 26. In other words, the damper compensation current calculation unit 23 calculates the damper compensation current Id according to the steering torque T phase-compensated by the phase compensation unit 26, the vehicle speed Vc, and the motor rotation speed Vm. The damper compensation current calculation unit 23 is, for example, a phase-compensated steering torque T (torque signal Ts), vehicle speed Vc (vehicle speed signal v), and motor, which are previously created based on empirical rules and stored in the ROM. By substituting the phase-compensated steering torque T, vehicle speed Vc, and motor rotational speed Vm into a control map indicating the correspondence between the rotational speed Vm (motor rotational speed signal Vms) and the damper compensation current Id, the damper compensation current Id is obtained. calculate.

  The temporary target current determination unit 25 includes a base current Ib calculated by the base current calculation unit 21, an inertia compensation current Is calculated by the inertia compensation current calculation unit 22, and a damper calculated by the damper compensation current calculation unit 23. A temporary target current Itf is determined based on the compensation current Id. For example, the temporary target current determination unit 25 determines the current obtained by adding the inertia compensation current Is to the base current Ib and subtracting the damper compensation current Id as the temporary target current Itf.

The sensor failure detection unit 27 detects, for example, an abnormality such that the output from the torque sensor 109 is fixed to zero (V) or a voltage other than zero to 5 (V) is output. Is determined to have failed, and the failure is output to the current failure determination unit 28 and the final target current determination unit 29.
The sensor failure current determination unit 28 will be described in detail later.

  The final target current determination unit 29 determines the temporary target determined by the temporary target current determination unit 25 when the sensor failure detection unit 27 does not determine that there is a failure (when a signal indicating failure has not been acquired). The current Itf is determined as the final target current It. On the other hand, when the sensor failure detection unit 27 determines that a failure has occurred (when a signal indicating failure has been acquired), the sensor failure current Ie determined by the sensor failure current determination unit 28 is used as the final target current. It is determined as It. That is, when the sensor failure detection unit 27 determines that there is a failure, the electric motor 110 generates an assist force corresponding to the sensor failure current Ie.

  Here, a state in which the torsion bar 112 has a zero twist amount is defined as a neutral state (neutral position), and the steering wheel 101 (lower connection shaft 108) and pinion shaft when the steering wheel 101 rotates clockwise from the neutral state (neutral position). The direction in which the relative rotation angle with respect to 106 changes (the direction in which the relative rotation angle occurs) is positive (the steering torque T is positive). On the other hand, the direction in which the relative rotation angle between the steering wheel 101 (lower connection shaft 108) and the pinion shaft 106 changes when the steering wheel 101 rotates counterclockwise from the neutral state (the direction in which the relative rotation angle occurs) is minus (steering torque T Is minus). At this time, an output value from the torque sensor 109 when the relative rotation angle between the steering wheel 101 and the pinion shaft 106 is twisted in the clockwise direction from the neutral state (the torsion bar 112 is twisted in the clockwise direction). The sign of a certain torque signal Td is added, and the sign of the torque signal Td from the torque sensor 109 when the relative rotation angle is twisted counterclockwise from the neutral state (the torsion bar 112 is twisted counterclockwise). Negative.

  When the sign of the torque signal Td from the torque sensor 109 is positive, the base current calculation unit 21 calculates the base current Ib so as to rotate the electric motor 110 in one rotation direction, and the base current Ib The direction of flow is positive. That is, as shown in FIG. 4, when the sign of the torque signal Td from the torque sensor 109 is positive and the steering torque T is positive, the base current calculation unit 21 calculates a positive base current Ib, Torque is generated in the direction of rotation in the direction of rotation. On the other hand, when the sign of the torque signal Td from the torque sensor 109 is negative, the base current calculation unit 21 calculates a negative base current Ib, and generates torque in a direction that rotates the electric motor 110 in the other rotation direction.

Next, the control unit 30 will be described in detail.
FIG. 5 is a schematic configuration diagram of the control unit 30.
As shown in FIG. 5, the control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and an actual current Im that actually flows through the electric motor 110. And a motor current detection unit 33 for detection. Further, the control unit 30 has a feedback current calculation unit 38 that calculates the feedback current If based on the actual current Im detected by the motor current detection unit 33 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. doing.

  The motor drive control unit 31 performs feedback control based on a deviation between the target current It finally determined by the target current calculation unit 20 and the feedback current If calculated by the feedback current calculation unit 38 ( F / B) The control unit 40 and the PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110 are included.

  The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current It finally determined by the target current calculating unit 20 and the feedback current If calculated by the feedback current calculating unit 38, and the deviation is A feedback (F / B) processing unit 42 that performs feedback processing so as to be zero.

The feedback (F / B) processing unit 42 performs feedback control so that the target current It and the feedback current If match. For example, the feedback (F / B) processing unit 42 is proportional to the deviation calculated by the deviation calculating unit 41. Is proportionally processed, integrated by an integral element, and these values are added by an addition operation unit.
The PWM signal generation unit 60 generates a PWM signal for PWM (pulse width modulation) driving of the electric motor 110 based on the output value from the feedback control unit 40 and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. Generate and output the generated PWM signal.

  The motor drive unit 32 is a so-called inverter, and includes, for example, six independent transistors (FETs) as switching elements. Three of the six transistors are a positive line of a power source, an electric coil of each phase, The other three transistors are connected to the electric coil of each phase and the negative side (ground) line of the power source. Then, the driving of the electric motor 110 is controlled by driving the gates of two transistors selected from the six and switching the transistors.

The motor current detection unit 33 detects the value of the actual current Im flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor connected to the motor drive unit 32.
The feedback current calculation unit 38 is based on the arithmetic expression stored in advance in the ROM, the actual current Im detected by the motor current detection unit 33, and the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. Is calculated.

The motor rotation angle calculation unit 71 calculates the motor rotation angle θ based on the output signal of the resolver 120.
The motor rotation speed calculation unit 72 (see FIG. 2) calculates the motor rotation speed Vm of the electric motor 110 based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71, and the calculated motor rotation speed Vm is an output signal. The motor rotation speed signal Vms converted into is output.

The steering angle calculation unit 73 (see FIG. 2) is configured such that the rotation angle (steering angle) of the steering wheel 101 and the motor rotation angle θ of the electric motor 110 because the steering wheel 101, the speed reduction mechanism 111, and the like are mechanically coupled. The steering angle is calculated based on the motor rotation angle θ calculated by the motor rotation angle calculation unit 71. For example, the steering angle calculation unit 73 performs steering based on the integrated value of the difference between the previous value and the current value of the motor rotation angle θ calculated periodically (for example, every 1 millisecond) by the motor rotation angle calculation unit 71. Calculate the corner. In other words, the steering angle calculation unit 73 calculates the steering angle based on the history of the motor rotation angle θ of the electric motor 110.
The resolver 120, the motor rotation angle calculation unit 71, and the steering angle calculation unit 73 function as an example of a steering angle estimation unit that estimates the steering angle. The calculated steering angle θsc calculated by the steering angle calculation unit 73 is the steering angle estimated by the steering angle estimation means.

  Here, the sign of the steering angle when the steering wheel 101 is rotated clockwise from zero degree is plus, and the sign of the steering angle when the steering wheel 101 is rotated counterclockwise is minus. Further, the sign of the rotation direction of the electric motor 110 mechanically connected to the steering wheel 101 is added to the rotation direction of the electric motor 110 when the steering wheel 101 is rotated to the right (one rotation direction described above), The rotation direction of the electric motor 110 when the steering wheel 101 is rotated counterclockwise (the other rotation direction described above) is negative.

[Sensor failure current determination unit 28]
Next, the sensor failure current determination unit 28 will be described in detail.
FIG. 6 is a schematic configuration diagram of the sensor failure current determination unit 28.
The sensor failure current determination unit 28 calculates a substitution steering angle θse, which is a steering angle for substitution into a control map described later, based on the calculated steering angle θsc calculated by the steering angle calculation unit 73. A calculation unit 281; a sensor failure base current calculation unit 282 that calculates a sensor failure base current Ieb that is a base of the temporary sensor failure current Iea based on the substitution steering angle θse calculated by the substitution steering angle calculation unit 281; It is equipped with.

  The sensor failure current determination unit 28 includes a return correction coefficient setting unit 283 that sets a return correction coefficient Kr for correcting the sensor failure current Ie so that the steering wheel 101 is turned back down. The return correction coefficient for calculating the return-corrected base current Iebr by multiplying the sensor-failure base current Ieb calculated by the sensor-failure base current calculation section 282 and the return correction coefficient setting section 283. A multiplication unit 284.

  In addition, the sensor failure current determination unit 28 includes a rotation speed correction coefficient setting unit 285 that sets a rotation speed correction coefficient Km according to the motor rotation speed Vm, and a return-corrected base calculated by the return correction coefficient multiplication unit 284. A rotation speed correction coefficient multiplying unit 286 that calculates a rotation speed corrected base current Iebv by multiplying the current Iebr by the rotation speed correction coefficient Km set by the rotation speed correction coefficient setting unit 285;

  Further, the sensor failure current determination unit 28 includes a limit processing unit 287 that performs a limit process on the rotation speed corrected base current Iebv calculated by the rotation speed correction coefficient multiplication unit 286, and a limit processing unit 287 that performs limit processing. An encoding processing unit 288 that performs encoding processing on the post-limit processing base current Il that is the post-rotation speed corrected base current Iebv.

  The sensor failure current determination unit 28 includes a fade processing unit 289 that performs a fade process on the post-limit processing base current Il that has been encoded by the encoding processing unit 288 based on the vehicle speed Vc. . The current after the fade processing is performed by the fade processing unit 289 is the temporary sensor failure current Iea.

  In addition, the sensor failure current determination unit 28 calculates the steering angle differential value calculation unit 291 that calculates the differential value of the calculated steering angle θsc calculated by the steering angle calculation unit 73 and the steering angle differential value calculation unit 291. A differential value current calculation unit 292 that calculates a differential value current Iθ according to the steering angle differential value θsc ′.

  In addition, the sensor failure current determination unit 28 includes a steering angle correction coefficient setting unit 293 that sets a steering angle correction coefficient Kθ corresponding to the calculated steering angle θsc calculated by the steering angle calculation unit 73, and a differential value current calculation unit. A steering angle correction coefficient multiplication unit 294 that calculates a differential current Iθs after steering angle correction by multiplying the differential current Iθ calculated in 292 and the steering angle correction coefficient Kθ set by the steering angle correction coefficient setting unit 293. And.

  In addition, the sensor failure current determination unit 28 performs a final determination based on the temporary sensor failure current Iea output from the fade processing unit 289 and the steering angle corrected differential current Iθs output from the steering angle correction coefficient multiplication unit 294. In addition, a final sensor failure current determination unit 295 is provided for determining the sensor failure current Ie.

Next, elements constituting the sensor failure current determination unit 28 will be described in detail.
<Substituted steering angle calculation unit 281>
The substitution steering angle calculation unit 281 calculates the zero degree by integrating the difference between the previous value and the current value of the calculated steering angle θsc periodically (for example, every 1 millisecond) calculated by the steering angle calculation unit 73 from zero degree. The rotation angle from is calculated, and this calculated value is set as the substitution steering angle θse. When a predetermined reset condition is satisfied, the substitution steering angle θse is reset to zero. The reset condition may be any condition as long as the difference in rotation angle (steering angle) of the steering wheel 101 can be grasped to be zero. For example, the target current It or the motor current set by the target current calculation unit 20 can be used. A case where the actual current Im detected by the detection unit 33 becomes zero or near the zero value can be exemplified.

<Sensor Failure Base Current Calculation Unit 282>
FIG. 7 is a schematic configuration diagram of the sensor failure base current calculation unit 282.
The sensor failure base current calculation unit 282 is converted into an absolute value by the absolute value conversion unit 282a that converts the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 into an absolute value and an absolute value conversion unit 282a. A temporary base current calculation unit 282b that calculates a temporary sensor failure base current Ieba that is a temporary sensor failure base current Ieb based on the absolute steering angle | θse |. The sensor failure base current calculation unit 282 includes a vehicle speed correction coefficient setting unit 282c that sets the vehicle speed correction coefficient Kv based on the vehicle speed signal v, and a temporary sensor failure base current calculated by the temporary base current calculation unit 282b. A vehicle speed correction coefficient multiplication unit 282d that calculates the sensor failure base current Ieb by multiplying Ieba by the vehicle speed correction coefficient Kv set by the vehicle speed correction coefficient setting unit 282c. The sensor failure base current calculation unit 282 calculates the sensor failure base current Ieb periodically (for example, every 1 millisecond).

(Absolute part 282a)
The absolute value converting unit 282a calculates the absolute value of the steering angle θse for substitution having a plus or minus sign. The value calculated by the absolute value converting unit 282a is the steering angle | θse | after the absolute value conversion.

(Temporary base current calculation unit 282b)
FIG. 8 is a schematic diagram of a control map showing the correspondence between the steering angle | θse | after absolute value conversion and the base current Ieba at the time of temporary sensor failure.
The temporary base current calculation unit 282b is illustrated in FIG. 8 that shows the correspondence between the steering angle | θse | after absolute value and the base current Ieba at the time of failure of the temporary sensor, which is created based on an empirical rule and stored in the ROM in advance. By substituting the steering angle | θse | after the absolute value into the control map, the base current Ieba at the time of temporary sensor failure is calculated.

In the control map shown in FIG. 8, when the absolute steering angle | θse | is equal to or smaller than a predetermined reference steering angle θse0, the temporary sensor failure base current Ieba is zero, and after the absolute value is obtained. As the steering angle | θse | becomes larger than the reference steering angle θse0, the temporary sensor failure base current Ieba gradually increases from zero. It can be exemplified that the reference steering angle θse0 is 10 degrees.
Since the control map indicating the correspondence between the steering angle | θse | after the absolute value and the base current Ieba at the time of failure of the temporary sensor is configured as shown in FIG. 8, the steering angle calculated based on the motor rotation angle θ ( A dead zone region in which the temporary sensor failure current Iea is zero is set in a region where the rotation angle of the steering wheel 101 is close to zero (| θse | ≦ θse0).

(Vehicle speed correction coefficient setting unit 282c)
FIG. 9 is a schematic diagram of a control map showing the correspondence between the vehicle speed correction coefficient Kv and the vehicle speed Vc.
The vehicle speed correction coefficient setting unit 282c substitutes the vehicle speed Vc into the control map illustrated in FIG. 9 that shows the correspondence between the vehicle speed correction coefficient Kv and the vehicle speed Vc, which is created in advance based on empirical rules and stored in the ROM. Thus, the vehicle speed correction coefficient Kv is calculated.
In the control map illustrated in FIG. 9, the vehicle speed correction coefficient Kv when the vehicle speed Vc is zero (km / h) is 1, and the vehicle speed correction coefficient Kv when the vehicle speed Vc is approximately 1 (km / h). 0.5. Further, the vehicle speed correction coefficient Kv when the vehicle speed Vc is approximately 5 (km / h) is set to approximately 0.3, and the vehicle speed correction coefficient Kv is changed while the vehicle speed Vc changes from approximately 1 to approximately 5 (km / h). It is gradually decreasing. Further, the vehicle speed correction coefficient Kv when the vehicle speed Vc is about 40 (km / h) is set to about 0.4, and the vehicle speed correction coefficient Kv is changed while the vehicle speed Vc changes from about 5 to about 40 (km / h). It is gradually rising. The vehicle speed correction coefficient Kv is gradually decreased as the vehicle speed Vc increases from approximately 40 (km / h).

(Vehicle speed correction coefficient multiplier 282d)
The vehicle speed correction coefficient multiplication unit 282d multiplies the temporary sensor failure base current Ieba calculated by the temporary base current calculation unit 282b by the vehicle speed correction coefficient Kv set by the vehicle speed correction coefficient setting unit 282c, thereby causing a sensor failure. The time base current Ieb is calculated, and the calculated sensor failure time base current Ieb is output to the return correction coefficient multiplier 284.

<Return correction coefficient setting unit 283>
FIG. 10 is a schematic configuration diagram of the return correction coefficient setting unit 283.
The return correction coefficient setting unit 283 includes an absolute value converting unit 283a that converts the calculated steering angle θsc calculated by the steering angle calculating unit 73 into an absolute value, and an absolute value converted into an absolute value by the absolute value converting unit 283a. A temporary return correction coefficient calculation unit 283b that calculates a temporary return correction coefficient Kra, which is a temporary return correction coefficient Kr, based on the rear steering angle | θsc |. The return correction coefficient setting unit 283 includes a first selection unit 283c that selects the temporary return correction coefficient Kra calculated by the temporary return correction coefficient calculation unit 283b or a predetermined value according to the vehicle speed Vc. . Further, the return correction coefficient setting unit 283 turns the steering wheel 101 based on the calculated steering angle θsc calculated by the steering angle calculation unit 73 and the substitution steering angle θse calculated by the substitution steering angle calculation unit 281. A determination unit 283d is provided for determining whether it is inserted or cut back. Further, the return correction coefficient setting unit 283 includes a second selection unit 283e that selects a value selected by the first selection unit 283c or a predetermined value according to the steering situation determined by the determination unit 283d. .

(Absolute part 283a)
The absolute value converting unit 283a calculates the absolute value of the calculated steering angle θsc having a plus or minus sign. The value calculated by the absolute value converting unit 283a is the steering angle | θsc | after the absolute value conversion.

(Temporary return correction coefficient calculation unit 283b)
FIG. 11 is a schematic diagram of a control map showing the correspondence between the steering angle | θsc | after absolute value conversion and the provisional return correction coefficient Kra.
The provisional return correction coefficient calculation unit 283b is illustrated in FIG. 11 illustrating the correspondence between the absolute value steering angle | θsc | and the provisional return correction coefficient Kra, which is created based on an empirical rule and stored in the ROM in advance. The temporary return correction coefficient Kra is calculated by substituting the steering angle | θsc | after absolute value into the control map.
In the control map shown in FIG. 11, when the absolute steering angle | θsc | is equal to or smaller than the predetermined lower steering angle θd, the provisional return correction coefficient Kra is zero, and the absolute steering angle is obtained. When | θsc | is equal to or greater than a predetermined upper steering angle θu, the provisional return correction coefficient Kra is 1. When the absolute steering angle | θsc | is between the lower steering angle θd and the upper steering angle θu, the provisional return correction coefficient Kra gradually increases from zero to one.

(First selection unit 283c)
The first selection unit 283c selects the temporary return correction coefficient Kra calculated by the temporary return correction coefficient calculation unit 283b when the vehicle speed Vc is equal to or higher than a predetermined vehicle speed Vcd, and when the vehicle speed Vc is less than the predetermined vehicle speed Vcd. Selects 1 which is a predetermined value. The predetermined vehicle speed Vcd can be exemplified as 1 km / h.

(Determination unit 283d)
The determination unit 283d multiplies the calculated steering angle θsc calculated by the steering angle calculation unit 73 by the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 (= θsc × If θse) is greater than or equal to zero, it is determined that the cut is made, and if the multiplication value is less than zero, it is determined that the cut is made.

(Second selection unit 283e)
The second selection unit 283e selects 1 which is a predetermined value when it is determined that the determination unit 283d has been cut, and the second selection unit 283e has a first value when it has been determined that the determination unit 283d has been cut back. The temporary return correction coefficient Kra selected by the 1 selection unit 283c is selected. Then, the second selection unit 283e outputs the selected value as a return correction coefficient Kr.

  With the configuration described above, the return correction coefficient setting unit 283 sets the return correction coefficient Kr periodically (for example, every 1 millisecond). Then, the return correction coefficient setting unit 283 sets the return correction coefficient Kr to 1 when the steering wheel 101 is cut. Further, even when the steering wheel 101 is turned back, the return correction coefficient setting unit 283 sets the return correction coefficient Kr to 1 when the vehicle speed Vc is less than the predetermined vehicle speed Vcd. Further, the return correction coefficient setting unit 283 is configured such that when the steering wheel 101 is turned back and the vehicle speed Vc is equal to or higher than the predetermined vehicle speed Vcd, the post-absolute steering angle | θsc | is equal to or higher than the upper steering angle θu. In some cases, the return correction coefficient Kr is set to 1. On the other hand, when the steering wheel 101 is turned back and the vehicle speed Vc is equal to or higher than the predetermined vehicle speed Vcd, the return correction coefficient setting unit 283 has a steering angle | θsc | after the absolute value is less than the upper steering angle θu. In some cases, a return correction coefficient Kr is set in accordance with the steering angle | θsc |

<Rotation speed correction coefficient setting unit 285>
The rotation speed correction coefficient setting unit 285 sets a rotation speed correction coefficient Km corresponding to the motor rotation speed Vm.
FIG. 12 is a schematic diagram of a control map showing the correspondence between the motor rotation speed Vm and the rotation speed correction coefficient Km.
The rotation speed correction coefficient setting unit 285 adds a motor map to the control map illustrated in FIG. 12 that shows the correspondence between the motor rotation speed Vm and the rotation speed correction coefficient Km, which is previously created based on empirical rules and stored in the ROM. The rotational speed correction coefficient Km is calculated by substituting the rotational speed Vm.
In the control map shown in FIG. 12, when the motor rotational speed Vm is equal to or lower than the predetermined rotational speed Vm0, the rotational speed correction coefficient Km is 1, and when the motor rotational speed Vm is larger than the rotational speed Vm0. The rotational speed correction coefficient Km is a value that gradually decreases from 1 to zero as the motor rotational speed Vm increases.

FIG. 13 is a schematic diagram of a control map showing the correspondence between the vehicle speed Vc and the vehicle speed correction coefficient Kc.
The rotational speed correction coefficient setting unit 285 corrects the motor rotational speed Vm to be substituted into the control map shown in FIG. 12 using the vehicle speed correction coefficient Kc set based on the control map and the vehicle speed Vc shown in FIG. (Motor rotation speed Vm to be substituted into the control map shown in FIG. 12 = motor rotation speed Vm × Kc calculated by the motor rotation speed calculation unit 72).
In the control map illustrated in FIG. 13, the vehicle speed correction coefficient Kc when the vehicle speed Vc is from zero to the first vehicle speed V1 is 1, and the vehicle speed correction coefficient Kc is approximately 0 when the vehicle speed Vc is greater than the second vehicle speed V2. .3. Further, the vehicle speed correction coefficient Kc is set to a value that gradually decreases from 1 to 0.3 while the vehicle speed Vc increases from the first vehicle speed V1 to the second vehicle speed V2. It can be illustrated that the first vehicle speed V1 is approximately 15 (km / h) and the second vehicle speed V2 is approximately 35 (km / h).

  With the configuration described above, the rotation speed correction coefficient setting unit 285 sets the rotation speed correction coefficient Km periodically (for example, every 1 millisecond). Then, the rotational speed correction coefficient setting unit 285 sets the rotational speed correction coefficient Km to a value smaller than 1 in order to suppress excessive cutting when the motor rotational speed Vm is high, in other words, when the steering angular speed of the steering wheel 101 is high. Set to. However, in order to secure the assist force necessary for avoiding danger when the vehicle speed Vc is high, when the vehicle speed Vc is higher than the second vehicle speed V2, the motor rotation speed Vm substituted into the control map shown in FIG. Correct so that On the other hand, when the vehicle speed Vc is lower than the first vehicle speed V1, no correction is made to reduce the motor rotation speed Vm that is substituted into the control map shown in FIG.

<Limit processing unit 287>
The limit processing unit 287 outputs the upper limit value as the post-limit processing base current Il when the post-rotation speed corrected base current Iebv calculated by the rotational speed correction coefficient multiplication unit 286 is larger than a predetermined upper limit value. When the calculated rotation speed corrected base current Iebv is equal to or lower than the upper limit value, the calculated rotation speed corrected base current Iebv is output as the limit-processed base current Il.

<Encoding processing unit 288>
When the sign of the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 is positive, the encoding processing unit 288 adds a plus sign to the post-limit processing base current Il output from the limit processing unit 287. Is attached. On the other hand, when the sign of the substitution steering angle θse calculated by the substitution steering angle calculation unit 281 is negative, the encoding processing unit 288 minus the limit-processed base current Il output from the limit processing unit 287. The symbol is attached.

  The return correction coefficient multiplication unit 284, the rotation speed correction coefficient multiplication unit 286, the limit processing unit 287, and the encoding processing unit 288 described above perform each process periodically (for example, every 1 millisecond). Therefore, the encoding processing unit 288 outputs the rotational speed-corrected base current Iebv to which the code is attached to the fade processing unit 289 periodically (for example, every 1 millisecond).

<Fade processing unit 289>
The fade processing unit 289 determines the temporary sensor failure current Iea based on the vehicle speed Vc. When the fade processing unit 289 determines the temporary sensor failure current Iea based on the vehicle speed Vc, the vehicle speed Vc greatly changes the vehicle speed correction coefficient Kv as shown in the control map illustrated in FIG. In the case of a magnitude other than between zero and approximately 1 (km / h) (a speed greater than 1 (km / h)), the encoding processing unit 288 determines the sign of the temporary sensor failure current Iea. The determined base current Iebv after the rotation speed correction is determined. On the other hand, when the vehicle speed Vc is 1 (km / h) or less, it takes a predetermined period from the previous temporary sensor failure current Iea to the rotational speed-corrected base current Iebv to which the current encoding processing unit 288 is attached. Gradually change. For example, when the vehicle speed Vc is decelerating from 1 (km / h), after the rotational speed correction, the current encoding processing unit 288 adds a sign from the previous temporary sensor failure current Iea in 1 second. A value that changes in the base current Iebv is determined as the temporary sensor failure current Iea periodically (for example, every 1 millisecond). On the other hand, when the vehicle speed Vc is accelerating from zero, the rotational speed-corrected base current Iebv, which is signed by the current encoding processing unit 288 from the previous temporary sensor failure current Iea in 0.5 seconds. The value that changes to is periodically determined (for example, every 1 millisecond) as the temporary sensor failure current Iea.

<Steering angle differential value calculation unit 291>
The steering angle differential value calculation unit 291 calculates the difference between the previous value and the current value of the calculated steering angle θsc calculated periodically (for example, every 1 millisecond (sampling time)) by the steering angle calculation unit 73 as the sampling time. The steering angle differential value θsc ′ is calculated by dividing.

<Differential Value Current Calculation Unit 292>
FIG. 14 is a schematic diagram of a control map showing the correspondence between the steering angle differential value θsc ′ and the differential value current Iθ.
The differential value current calculation unit 292 calculates a differential value current Iθ according to the steering angle differential value θsc ′. For example, the differential value current calculation unit 292 is based on the control map illustrated in FIG. 14 that shows the correspondence between the steering angle differential value θsc ′ and the differential value current Iθ, which is created in advance based on empirical rules and stored in the ROM. Then, the differential value current Iθ is calculated by substituting the steering angle differential value θsc ′.
In the control map shown in FIG. 14, as the absolute value of the steering angle differential value θsc ′ increases, the differential current Iθ increases from zero.

<Steering angle correction coefficient setting unit 293>
FIG. 15 is a schematic diagram of a control map showing the correspondence between the absolute value | θsc | of the calculated steering angle θsc and the steering angle correction coefficient Kθ.
The steering angle correction coefficient setting unit 293 sets a steering angle correction coefficient Kθ corresponding to the absolute value | θsc | of the calculated steering angle θsc calculated by the steering angle calculation unit 73.
The steering angle correction coefficient setting unit 293 is illustrated in FIG. 15 showing the correspondence between the absolute value | θsc | of the calculated steering angle θsc that is created based on an empirical rule and stored in the ROM, and the steering angle correction coefficient Kθ. The steering angle correction coefficient Kθ is calculated by substituting the absolute value | θsc | of the calculated steering angle θsc into the control map.
In the control map shown in FIG. 15, when the absolute value | θsc | of the calculated steering angle θsc is equal to or smaller than a predetermined reference steering angle θsc0, the steering angle correction coefficient Kθ is 1, and the calculated steering angle θsc When the absolute value | θsc | is larger than the reference steering angle θsc0, the steering angle correction coefficient Kθ is a value that gradually decreases from 1 as the absolute value | θsc | of the calculated steering angle θsc increases. It can be illustrated that the reference steering angle θsc0 is 10 degrees, similar to the reference steering angle θse0 in the control map shown in FIG.

<Steering angle correction coefficient multiplier 294>
The steering angle correction coefficient multiplication unit 294 multiplies the differential value current Iθ calculated by the differential value current calculation unit 292 and the steering angle correction coefficient Kθ set by the steering angle correction coefficient setting unit 293 to thereby obtain the steering angle. The corrected differential current Iθs is calculated, and the calculated steering angle corrected differential current Iθs is output to the final sensor failure current determination unit 295.

<Final sensor failure current determination unit 295>
The final sensor failure current determination unit 295 is output from the fade processing unit 289 when the sensor failure detection unit 27 detects a failure of the torque sensor 109 in processing periodically (for example, every 1 millisecond). A value obtained by adding the temporary sensor failure current Iea and the steering angle corrected differential current Iθs output from the steering angle correction coefficient multiplier 294 is determined as the sensor failure current Ie (Ie = Iea + Iθs). On the other hand, if the sensor failure detection unit 27 does not detect a failure of the torque sensor 109 in the process performed periodically (for example, every 1 millisecond), the final sensor failure current determination unit 295 Ie is determined to be zero.

According to the steering device 100 configured as described above, normal assist control is performed using the target current It determined based on the steering torque T detected by the torque sensor 109 when the torque sensor 109 has failed as an assist current. Even when it cannot be performed, the assist control at the time of failure can be performed based on the output value from the resolver 120.
When the assist control at the time of failure is performed, the vehicle speed correction coefficient Kv is set to 1 based on the control map illustrated in FIG. 9 when the vehicle has a large road frictional force, so that the vehicle speed Vc is larger than zero. Increases assist power. As a result, even in the case of assist control at the time of failure, handling characteristics at the time of parking and stopping are ensured. On the other hand, when the vehicle speed Vc is greater than approximately 1 (km / h) and the vehicle moves to the dynamic friction force region, the vehicle speed correction coefficient Kv is set to 0.5 or less based on the control map illustrated in FIG. Since the assist force is suddenly weakened, it is adjusted so that there is no excessive assist. Further, in a region where the vehicle is turning and the vehicle speed Vc is larger than about 10 (km / h), the steering force tends to increase. At this speed, the vehicle speed correction coefficient Kv is about 5 (km / h). The assist power increases because it is higher than that. However, since the vehicle speed correction coefficient Kv is set small in a region where the vehicle speed Vc is greater than approximately 40 (km / h), the assist force is weakened. Thereby, the wobbling of the vehicle at a high vehicle speed is suppressed.
Furthermore, even when the vehicle speed correction coefficient Kv changes greatly between zero and approximately 1 (km / h), the assist force is gradually changed by the fade processing unit 289, so that the assist force changes abruptly. The deterioration of the steering feeling due to this is suppressed.

  Further, in the assist control at the time of failure, excessive rotation when the steering angular speed of the steering wheel 101 is large is suppressed by the rotational speed correction coefficient Km set by the rotational speed correction coefficient setting unit 285. However, when the vehicle speed Vc is higher than the second vehicle speed V2, the rotational speed correction coefficient Km is set so as to increase, so that the assist force necessary to avoid danger when the vehicle speed Vc is high is ensured. Further, when the vehicle speed Vc is smaller than the first vehicle speed V1, the rotational speed correction coefficient Km is set to be small, so that steering is suppressed even when traveling on a low μ road at low speed. Further, the steering catch when the vehicle is stopped is suppressed.

  As described above, according to the steering device 100 according to the present embodiment, it is possible to apply the assist force according to the use state of the vehicle even during the assist control at the time of failure. That is, it is possible to realize the provision of assist force for avoiding danger and also to provide assist force for general travel. As a result, even after a failure occurs in the torque sensor 109, it is possible to go to the home or the nearest dealer, and the safety of the driver can be ensured.

  Further, according to the steering device 100 according to the present embodiment, when the torque sensor 109 fails, the sensor failure current Ie determined by the sensor failure current determination unit 28 is the temporary sensor failure current Iea and the steering. This is a current obtained by adding the differential current Iθs after the angle correction. In other words, the differential current Iθs after steering angle correction corresponding to the differential value of the estimated steering angle (calculated steering angle θsc) is added to the target current It when the torque sensor 109 fails.

FIG. 16 is a diagram illustrating the relationship between the steering angle and the steering force when the torque sensor 109 fails. In FIG. 16, the steering force of the driver in the steering device 100 according to the present embodiment is shown by a solid line, and the steering force of only the temporary sensor failure current Iea is shown by a two-dot chain line (the differential current Iθs after steering angle correction). Not added). Further, the steering force when the assist force is zero is shown by a broken line.
When the differential current Iθs after steering angle correction is not taken into account, in the dead zone region where the steering angle is close to zero (| θse | ≦ θse0≈θsc0), the temporary sensor failure current Iea becomes zero. As shown, the driver's steering force is a steering force equivalent to zero assist force, and the driver's burden is heavy. Further, in this region, the steering wheel 101 does not rotate smoothly, and a catch occurs at the start of steering.
On the other hand, in the steering device 100 according to the present embodiment, the assist force corresponding to the differential current Iθs after the steering angle correction can be added in this dead zone region (| θsc | ≦ θsc0≈θse0). Therefore, as shown by the solid line in FIG. 16, the driver's steering burden can be reduced.

  As described above, in the steering apparatus 100 according to the present embodiment, the dead zone is set while setting the zone where the current Iea at the time of the temporary sensor failure becomes zero in the dead zone where the steering angle is close to zero (| θse | ≦ θse0). An assist force equivalent to the differential current Iθs after the steering angle correction based on the steering angle differential value can be applied to the region (| θse | ≦ θse0). As a result, when the steering wheel 101 is steered by the driver to change the traveling direction while providing an appropriate dead zone region to suppress steering wobbling, the differential value after the steering angle correction even in the dead zone region. The driver's steering burden can be reduced by the assist force of the current Iθs.

  In the above-described embodiment, the fade processing unit 289 fades the temporary sensor failure current Iea in accordance with the vehicle speed Vc. For example, the post-rotation speed corrected base current Iebv input to the limit processing unit 287 may be faded before the limit processing unit 287. As a result, the steering feeling is prevented from deteriorating due to the abrupt change of the assist force.

  In the above-described embodiment, the sensor failure current Ie is determined using the rotation angle (steering angle) of the steering wheel 101 calculated by the steering angle calculation unit 73 based on the output signal from the resolver 120. However, it is not particularly limited to such an embodiment. For example, a steering angle sensor that detects the rotation angle of the steering wheel 101 may be provided, and the sensor failure current Ie may be determined based on the steering angle detected by the steering angle sensor.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target current calculation part, 28 ... Current determination part at the time of sensor failure, 30 ... Control part, 100 ... Electric power steering apparatus, 109 ... Torque sensor, 110 ... Electric motor, 120 ... Resolver

Claims (2)

An electric motor that applies assisting force to the steering wheel of the vehicle;
Torque detecting means for detecting a steering torque of the steering wheel;
Steering angle estimating means for estimating a steering angle which is a rotation angle of the steering wheel;
Failure detection means for detecting a failure of the torque detection means;
When the failure detection means does not detect a failure, the assist force is determined based on the steering torque detected by the torque detection means, and when the failure detection means detects a failure, the steering angle estimation Control means for controlling the electric motor such that the assist force increases as the differential value of the estimated steering angle estimated by the means increases;
Equipped with a,
The control means includes a first assist current determined based on the estimated steering angle and a second assist current determined based on a differential value of the estimated steering angle when the failure detection means detects a failure. The added value is determined as the assist current of the electric motor, and when the estimated steering angle is smaller than a predetermined steering angle, the first assist current is determined to be zero. apparatus. 2. The electric power steering apparatus according to claim 1, wherein the control unit corrects the second assist current to be smaller when the estimated steering angle is large than when the estimated steering angle is small.

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