JP2002104218A - Control device of motor-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device for motor-driven power steering device capable of keeping the safety high even if an erroneous steering angle is sensed, for example resulting from any failure in a steering angle sensor. SOLUTION: The target steering torque setting part 32 of a central processing unit(CPU) 21 of this control device 20 sets a target steering torque Th* on the basis of the steering angle θ and car speed V. A current command value calculation part 31 calculates the assist current command value I on the basis of the steering torque Th, target steering torque Th*, and the current Im of a motor 6. The CPU 21 makes drive control of the motor 6 on the basis of the assist current command value I. A failure sensing part 71 for the steering angle in which the steering angle signal θ* to generate the steering angle θis fed deenergizes a relay 75 to stop the motor 6 when judgement is such that the steering angle signal θ* is in failure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an electric power steering device for applying an assisting force by a motor to a steering system of an automobile or a vehicle.

[0002]

2. Description of the Related Art FIG. 15 schematically shows a control device relating to a conventional electric power steering device used for an automobile or the like.

A steering shaft 42 connected to a steering wheel 41 is provided with a torsion bar 43. A torque sensor 44 is mounted on the torsion bar 43. When the steering shaft 42 rotates and a force is applied to the torsion bar 43,
The torsion bar 43 is twisted according to the applied force, and the torque sensor 44 detects the twist.

[0004] A speed reducer 45 is fixed to the steering shaft 42. This reduction gear 45 has a motor 4
The gear 47 attached to the rotation shaft 6 is meshed. Further, a pinion shaft 48 is fixed to the speed reducer 45. A pinion 49 is provided at the tip of the pinion shaft 48.
Is fixed, and the pinion 49 is
Is engaged.

At both ends of the rack 51, tie rods 52 are provided.
Is fixed. Knuckles 53 are rotatably connected to both ends of the tie rod 52. A front wheel 54 is fixed to the knuckle 53. Also, Knuckle 5
3 is rotatably connected to the cross member 55.

Accordingly, when the motor 46 rotates, the rotation speed is reduced by the speed reducer 45 and transmitted to the pinion shaft 48, and transmitted to the rack 51 via the rack and pinion mechanism 50. The knuckle 53 connected to the tie rod 52 fixed to the rack 51 moves rightward or leftward according to the rotation direction of the motor 46.
The front wheel 54 is provided with a vehicle speed sensor 56.

The number of rotations and the direction of rotation of the motor 46 are determined by positive and negative assist currents supplied from a motor driving device 57. The assist current supplied by the motor driving device 57 to the motor 46 is calculated by an assist current determining unit 58 that controls the motor driving device 57. The assist current determination means 58
U and the like, and calculates the current steering torque of the steering wheel 41 from the detection signal from the torque sensor 44 and calculates the current vehicle speed from the detection signal from the vehicle speed sensor 56.

[0008] The assist current determining means 58 calculates an assist current (an assist current command value) based on the calculated steering torque and vehicle speed. This calculation is obtained from an assist map previously stored in a memory in the assist current determining means 58. Then, the assist current determining means 58 controls the current of the motor 46 for generating the assist torque so as to be the assist current (assist current command value).

However, the assist map is a value set in a specific road surface reaction force condition (for example, a flat asphalt road), and changes the road surface reaction force condition, that is, a low μ road such as a snowy road or a tire. When the air pressure drops and tire specifications (wear, tire type, etc.) change, the road surface reaction force changes, and therefore the steering force changes, leading to a deterioration in feeling.

The rise of the steering torque with respect to the steering angle (build-up feeling) is used as an index for judging the steering feeling. However, since the control device determines the assist current for the steering torque and the vehicle speed, There is a problem that it is very difficult to set map data for outputting a predetermined steering torque with respect to the steering angle (that is, for giving a feeling of buildup).

Further, when a disturbance torque due to inertia and viscosity is generated by a motor, a speed reducer, etc. during fast steering, etc., the disturbance torque cannot be canceled by the assist current determining means. Therefore, a separate control for canceling the inertia and viscosity is performed. Was needed.

Further, there is a problem that the control of the hysteresis of the steering torque when the vehicle is steered right and left cannot be set freely, and the degree of freedom for realizing an ideal steering feeling is low.

In order to solve these problems, the present applicant sets a target steering torque according to the steering angle and the vehicle speed, and sets an assist current command value based on the steering torque, the target steering torque and the motor current. A device that determines and controls the motor is proposed.

That is, a steering angle sensor 59 for detecting the steering angle of the steering shaft 42 (in FIG.
(Shown by a dotted chain line), and the assist current determining means 58
The target steering torque is set based on the steering angle from the steering angle sensor 59 and the vehicle speed. The target steering angle torque is determined by referring to a map for calculating the target steering angle torque from the steering angle at a certain vehicle speed, as shown in FIG. 16, for example.

Further, an assist current (assist current command value) is calculated based on the steering torque, the target steering torque, and the motor current of the motor 46. As a result, the target steering torque with respect to the vehicle speed and the steering angle can be set freely,
The inclination of the steering torque with respect to the steering angle can be easily set, and the adaptation of the build-up feeling is easily performed. Further, even if the road surface reaction force decreases, or the actual steering torque decreases or increases due to the viscosity or inertia of the motor 46 or a speed reducer connected to the motor, the steering torque remains at the target steering torque T.
Assist current (assist current command value) so that h *
The function of adjusting the operation works, and a stable operation feeling can be provided.

[0016]

In the above apparatus, it is assumed that the steering angle sensor 59 is disconnected while the steering wheel 41 is steered to the right by a certain steering angle θ0. As shown in FIG. 17, even if the steering wheel 41 is steered at this time and the steering angle (actual steering angle) changes, the assist current determination means 58 determines that the steering angle θ0 has not changed.

Therefore, even if the actual steering angle is changed by steering, the control is performed such that the target steering torque becomes the target steering torque T1 at the steering angle θ0. At this time, the actual steering torque tends to be equal to or more than T1 with the increase of the road surface reaction force that further cuts to the right (see FIG. 17). However, the assist current determining means 58 acts to increase the assist current in order to maintain the target steering torque T1. For this reason,
As long as the capability of the motor 46 and the capability of the assist current determining means 58 allow, the actual steering torque becomes equal to the target steering torque T1. In other words, when the steering angle is cut to a value equal to or greater than the disconnected steering angle θ0, a phenomenon occurs in which the steering torque does not change and the vehicle does not respond, and the user feels strange.

On the other hand, when the steering wheel 41 is turned leftward from the state of the steering angle θ0, the actual steering torque decreases, and eventually becomes the steering torque of the opposite polarity. At this time, the assist current determining means 58 outputs the target steering torque T
In order to maintain the value of 1, the assist current acts in the direction of decreasing the assist current, and the assist current eventually becomes zero. Therefore, when the vehicle is turned leftward, the assist current is completely lost, and the vehicle enters a manual steering state. Therefore, as described above, when an abnormal situation such as a disconnection occurs in the steering angle sensor 59, there is a possibility that the feeling may be remarkably lacking in steerability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to maintain high safety even if an abnormal steering angle is detected due to an abnormal steering angle sensor. It is an object of the present invention to provide a control device for an electric power steering device that can perform the above.

[0020]

According to a first aspect of the present invention, there is provided a control system for an electric power steering apparatus having control means for controlling the driving of a motor based on an assist current command value. In the device, target steering torque setting means for setting a target steering torque based on the input steering angle and vehicle speed, and an assist current command value is calculated based on the steering torque, the target steering torque, and the motor current of the motor. Assist current calculation means, and steering angle abnormality detection means for determining whether or not the input steering angle is abnormal. When the steering angle abnormality detection means detects an abnormality, the control means stops driving the motor. The point is to do.

According to a second aspect of the present invention, there is provided a control device for an electric power steering apparatus having a control means for controlling the driving of a motor based on an assist current command value, wherein a target steering torque is determined based on the input steering angle and vehicle speed. Target assisting torque setting means for setting an assist current command value based on the steering torque, the target steering torque, and the motor current of the motor; and input vehicle speed and steering torque. A second assist current calculating means for calculating an assist current command value based on the detected steering angle; and a steering angle abnormality detecting means for determining whether or not the input steering angle is abnormal, according to an abnormality detection result of the steering angle abnormality detecting means. The control means needs to drive the motor based on the assist current command value calculated by either the first or second assist current calculation means. To.

(Action) According to the first aspect of the present invention, the target steering torque setting means sets the target steering torque based on the steering angle and the vehicle speed. The assist current calculation means calculates an assist current command value based on a steering torque, the target steering torque, and a motor current of the motor. The control means drives and controls the motor based on the assist current command value. The steering angle abnormality detecting means determines whether the steering angle is abnormal. When the steering angle abnormality detection unit detects that the steering angle is abnormal, the control unit stops driving the motor.

According to the invention of claim 2, the target steering torque setting means sets the target steering torque based on the steering angle and the vehicle speed. The first assist current calculation means calculates an assist current command value based on a steering torque, the target steering torque, and a motor current of the motor. The control means drives and controls the motor based on the assist current command value. The steering angle abnormality detecting means determines whether the steering angle is abnormal. When the steering angle abnormality detecting means detects that the steering angle is abnormal, the control means controls the motor based on the assist current command value calculated based on the vehicle speed and the steering torque by the second assist current calculating means. Drive control.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment in which the present invention is embodied in a control device for an electric power steering device of a column and pinion assist type mounted on an automobile will be described with reference to FIGS. I do.

FIG. 1 schematically shows an electric power steering apparatus. A steering shaft 2 connected to the steering wheel 1 is provided with a torsion bar 3. For convenience of explanation, the steering wheel may be hereinafter referred to as a steering wheel. This torsion bar 3
Is equipped with a torque sensor 4. When the steering shaft 2 rotates and a force is applied to the torsion bar 3, the torsion bar 3 is twisted in accordance with the applied force, and the torsion bar 3, that is, the steering torque Th applied to the steering wheel 1 is detected by the torque sensor 4. I have. Further, a steering angle sensor 17 for detecting a steering angle θ of the steering shaft 2 is mounted on the steering shaft 2.
These sensor outputs are supplied to the control device 20.

The steering shaft 2 has a speed reducer 5
Is fixed. A gear 7 attached to a rotating shaft of an electric motor (hereinafter referred to as a motor) 6 is engaged with the speed reducer 5. Further, the reduction gear 5 has a pinion shaft 8.
Is fixed. A pinion 9 is fixed to the tip of the pinion shaft 8, and the pinion 9 meshes with a rack 10. The rack 10 and the pinion 9 constitute a rack & pinion mechanism 11. A tie rod 12 is fixed to both ends of the rack 10, and a knuckle 13 is rotatably connected to a tip end of the tie rod 12. A front wheel 14 as a tire is fixed to the knuckle 13. One end of the knuckle 13 is rotatably connected to the cross member 15.

Therefore, when the motor 6 rotates, the rotation speed is reduced by the speed reducer 5 and transmitted to the rack 10. The rack 10 can change the direction of the front wheels 14 provided on the knuckle 13 via the tie rods 12 to change the traveling direction of the vehicle. The motor 6
Is provided with a motor rotation angle sensor 72 for detecting the motor rotation angle θm.

The front wheel 14 is provided with a vehicle speed sensor 16. Next, FIG. 1 shows an electrical configuration of the electric power steering device. The torque sensor 4 outputs a signal indicating the steering torque Th of the steering wheel 1. The steering angle sensor 17 outputs a steering angle signal indicating the steering angle θ of the steering shaft 2. Vehicle speed sensor 16
Outputs a detection signal corresponding to the rotation speed of the front wheels 14 indicating the vehicle speed V at that time. The motor rotation angle sensor 72 is
The control device 20 outputs a signal indicating the motor rotation angle θm of the motor 6.
Output to The control device 20 is electrically connected to a motor drive current sensor 18 for detecting a drive current (motor current Im, corresponding to the motor current value) flowing through the motor 6. Current Im
Is supplied.

The control device 20 includes a central processing unit (CPU) 21 as control means, a read-only memory (ROM).
22 and a read-only and write-only memory (RAM) 23 for temporarily storing data.

Various control programs executed by the CPU 21 are stored in the ROM 22. RAM
Reference numeral 23 temporarily stores the result of the arithmetic processing when the CPU 21 performs the arithmetic processing.

A motor driving device 24 is connected to an output side of the control device 20, and drives the motor 6 based on a control signal from the control device 20. The motor driving device 24 includes a PWM of a CPU 21 described later.
A power element (not shown) such as an FET for performing PWM control based on the calculation is provided.

As shown in FIG. 2, a relay 75 is connected between the motor driving device 24 and the battery B. The relay contact of the relay 75 is a so-called a contact, which shuts off the supply of power from the battery B to the motor drive unit 24 during demagnetization and allows the supply of power from the battery B to the motor drive unit 24 during excitation. It has become.

The CPU 21 corresponds to target steering torque setting means, assist current calculation means, and steering angle abnormality detection means. Next, the assist control will be described with reference to FIGS.

In the following description of the functions inside the CPU 21, "vehicle speed V", "steering torque Th", "steering angle θ"
And the like are used as meanings of their corresponding signals for convenience of explanation.

FIG. 2 is a control block diagram of the CPU 21. In this embodiment, the inside of the CPU 21 shows functions executed by a program. For example, the phase compensator 30
Represents a phase compensation function executed inside the CPU 21 instead of independent hardware. Similarly, FIGS. 4 and 7 to 9 show, in a control block diagram, processing functions executed by the CPU 21 in accordance with a program, and do not mean an actual hardware configuration.

Hereinafter, functions and operations of the CPU 21 will be described. (Vehicle Speed Sensitive Assist Control) As shown in FIG. 2, the CPU 21 includes phase compensators 30 and 35, a current command value calculating unit 31 as an assist current determining unit, a target steering torque setting unit 32 as a target steering torque setting unit, and a subtractor 33. , Current control unit 34, steering angle abnormality detection unit 7 as steering angle abnormality detection means
It has functions such as 1.

The target steering torque setting section 32 inputs the vehicle speed V from the vehicle speed sensor 16 and the steering angle θ from the steering angle sensor 17, and sets the target steering torque Th *. The steering angle θ
Is input to the target steering torque setting unit 32 via the phase compensator 35. That is, the phase compensator 35
Is configured to compensate the phase of the steering angle signal θ * output from the steering angle sensor 17 to advance the phase, and to output the result to the target steering torque setting unit 32 as the steering angle θ.

More specifically, the phase compensator 35
Is, as shown in FIG. 4, a differentiator 36 and a gain multiplier 37.
And an adder 38. The differentiator 36 obtains a steering angular velocity S by differentiating the steering angle signal θ * from the steering angle sensor 17, and the gain multiplication unit 37 adds a value ST obtained by multiplying the steering angular velocity S by a preset gain T. 38. The gain T is calculated based on the steering angle signal θ *.
Is determined based on a value obtained by a test or the like in advance so that a phenomenon that the steering torque (actual steering torque) for the steering angle signal θ * does not coincide with the aimed target steering torque Th * does not occur. . The adder 38 adds the ST to the steering angle signal θ * to advance the phase (in this embodiment, this is referred to as the steering angle θ), and outputs the value to the target steering torque setting unit 32. It has become.

As shown in FIG. 5, the target steering torque setting section 32 includes a plurality of target steering torque setting maps corresponding to a plurality of different predetermined vehicle speeds. Vehicle speed V
The target steering torque setting map is set such that the slope of the target steering torque Th becomes steeper as the vehicle speed V becomes lower as the vehicle speed V becomes lower.

More specifically, a method of setting the target steering torque Th * will be described with reference to a flowchart of a target steering torque setting routine executed by the CPU 21 (see FIG. 3).
First, in S10, the steering angle θ is read, and in S11, the current steering state is right steering (steering to the right), left steering (steering to the left), or the state where the steering is maintained. In order to determine whether or not the steering angle is different, the steering angle θ is differentiated to calculate the steering angular velocity dθ / dt.

In the next step S12, when the steering angular velocity is close to zero (| dθ / dt | ≦ ε, ε is a constant that is a small value), it is determined that the steering is maintained (in S12, YES)), the steering direction determined in the previous control cycle in S17 is set as the current steering direction,
Move to S14.

When the steering angular velocity dθ / dt is not close to zero (when it is determined “NO” in S12),
In S13, the sign of the steering angular velocity dθ / dt is checked to determine the steering direction.

Next, in S14, a target steering torque setting map relating to a vehicle speed close to the vehicle speed V is checked out of a plurality of target steering torque setting maps stored in the ROM 22 in advance for the vehicle speed V. The vehicle speeds on the map side, which are close to the vehicle speed V, are V1 and V2 (V1 ≦ V <V2).

The target steering torque setting map is shown in FIG.
As shown in (1), a target steering torque is determined for each speed corresponding to right steering and left steering. In the next S15, temporary target steering torques Th1 * and Th2 * are obtained from the retrieved target steering torque setting maps of the vehicle speeds V1 and V2 based on the steering direction determined in S13 in accordance with the steering angle θ. In S16, the target steering torque Th * with respect to the vehicle speed V and the steering angle θ is calculated by a linear interpolation formula with respect to the vehicle speed V.

The equation for the linear interpolation is as follows. Th * = (Th2 * −Th1 *) / (V2−V1) ×
(V−V1) + Th1 * Next, the current command value calculation unit 31 will be described.

The steering torque Th input from the torque sensor 4 is phase-compensated by the phase compensator 30 in order to enhance the stability of the steering system, and is input to the current command value calculator 31.
The vehicle speed V detected by the vehicle speed sensor 16, the motor current Im detected by the motor drive current sensor 18, and the target steering torque Th * from the target steering torque setting unit 32 are input to the current command value calculation unit 31. .

The current command value calculating section 31 is a vehicle speed sensitive assist command which is a control target value of a current supplied to the motor 6 based on the inputted steering torque Th, vehicle speed V, target steering torque Th * and motor current Im. A value (corresponding to an assist current command value) I is determined. The current command value calculation unit 31
As shown in FIG. 7, a dead zone width setting section 25 and a vehicle speed sensitive assist torque calculating section 26 are provided.

The dead zone width setting section 25 calculates the
As shown in FIG. 8, the dead zone width T0 of the steering torque that is not energized is obtained using the dead zone width map MP stored in the ROM 22 in advance, and supplied to the vehicle speed sensitive assist torque calculation unit 26. Note that the dead zone width map MP is a two-dimensional map including the vehicle speed V and the dead zone width T0, and the dead zone width T0 is uniquely obtained from the vehicle speed V.

As shown in FIG. 6, the vehicle speed sensitive assist torque calculating section 26 determines that the target steering torque Th * obtained by the target steering torque setting section 32 is equal to the dead zone width T0 (that is, in FIG. , -T0 to T0), the vehicle speed-sensitive assist command value (corresponding to the assist current command value, hereinafter referred to as an assist current command value) I is determined to be 0. , And outputs this value to the subtractor 33.

When the target steering torque Th * is out of the range of the dead zone width T0, the rack thrust calculated by the current steering torque Th and the motor current Im, and the target steering torque Th
* The assist current command value I is set so that the rack thrust at the assist current command value I is balanced.

Hereinafter, a method of determining the assist current command value I in the case of the control device of the column and pinion assist type electric power steering device of the present embodiment will be described.

In the case of the column and pinion assist type, the rack thrust F at the time of the steering torque Th and the motor current Im is obtained by the following equation (A). F (Th, Im) = 2π (Th + Kt · Im · G · ηg) · ηp / St (A) where Th is the steering torque, ηp is the rack and pinion gear efficiency, and St is the stroke ratio. Kt is a torque constant, G is a reduction ratio of the reduction gear 5, and ηg is a reduction gear efficiency of the reduction gear 5.

Therefore, using the above equation (A), the target steering torque Th * at the vehicle speed V, the steering angle θ, and the rack thrust F at the assist current command value I (hereinafter, this thrust is referred to as F (Th *, I), and a rack thrust F at the time of the steering torque Th and the motor current Im (hereinafter, this thrust is referred to as F
(Th, Im). ) Are set equal to each other.

When F (Th *, I) = F (Th, Im),
When I is obtained by substituting the above equation (A), the following equation is obtained. I = Im + (Th−Th *) / (Kt · G · ηg) The assist current command value I thus obtained is output to the subtractor 33.

When the assist current command value I has the opposite sign to the target steering torque Th *, that is, reverse assist, the assist current command value I is determined to be zero and output to the subtractor 33.

The subtracter 33 outputs a signal (corresponding to an assist current control value) corresponding to the difference from the actual motor current Im to the current control unit 34. In the present embodiment, the current control unit 34 performs known PI control, and performs motor drive to perform feedback control based on a signal corresponding to the difference between the output of the subtracter 33 and the actual motor current Im. Supply to device 24. That is, in the current control unit 34,
PWM calculation is performed so that the motor current becomes the assist command current value, and the motor 6 is driven based on the calculation result.

As a result, by controlling the driving of the motor 6 via the motor driving device 24, an appropriate assisting force by the motor 6 can be obtained. Next, the steering angle abnormality detection unit 71 will be described.

The steering angle signal θ * output from the steering angle sensor 17 and before the phase compensation is performed is output from the steering angle abnormality detector 7.
1 is input. The motor rotation angle θm detected by the motor rotation angle sensor 72 is also input to the steering angle abnormality detection unit 71.

The steering angle abnormality detection section 71 determines whether or not the input steering angle signal θ * is abnormal based on the input steering angle signal θ * and motor rotation angle θm. Then, it is determined whether or not to output a control signal for degaussing the relay 75 based on this.

The steering angle abnormality detecting section 71 includes a steering angle estimating section 73 and a comparing section 74 as shown in FIG.
In the present embodiment, the steering angle signal θ * corresponds to “steering angle”.

The steering angle estimating unit 73 calculates (estimates) the steering angle (hereinafter referred to as “estimated steering angle”) θs of the steering wheel 1 by dividing the motor rotation angle θm by the reduction ratio G of the speed reducer 5. Then, the estimated steering angle θs is output to the comparison unit 74.

The comparator 74 compares the steering angle signal θ * with the estimated steering angle θs to determine whether the steering angle signal θ * from the steering angle sensor 17 is abnormal. That is, the comparison unit 74
Determines whether the steering angle signal θ * and the estimated steering angle θs satisfy the following equation (α).

Δθ−θo ≧ θ1 (α) where Δθ is a deviation between the steering angle signal θ * and the estimated steering angle θs, and is calculated by the following equation (β).

Δθ = | θs−θ * | (β) Further, θo is an offset value. That is, the estimated steering angle θs estimated from the motor rotation angle sensor 72 is not always that the steering wheel 1 is at the neutral position, and the absolute angle is unknown. Therefore, when the control device 20 is first turned on, the estimated steering angle θs is set to 0, and the steering angle θo detected by the steering angle sensor 17 at that time is stored in the RAM 23 as an offset value. Θ1 is an abnormality determination threshold, which is stored in the ROM 22 in advance.

When the above equation (α) is satisfied, a control signal is output so that the relay 75 is demagnetized and turned off. On the other hand, if the above equation (α) is not satisfied, a control signal is output to keep the relay 75 in the ON state.

Next, the steering angle abnormality detection processing in this embodiment will be described with reference to the flowchart shown in FIG.
The CPU 21 executes the steering angle abnormality detection processing by interruption every predetermined time.

First, in S101, the CPU 21
The steering angle signal θ * input from the steering angle sensor 17 is read, and in S102, the steering angle abnormality detection unit 71 of the CPU 21 determines whether the input steering angle signal θ * is abnormal. Since the above-mentioned equation (α) is not satisfied, the steering angle signal θ *
If the steering angle abnormality detection unit 71 determines that the steering angle is normal, the process proceeds to S103. That is, a control signal is output from the steering angle abnormality detection unit 71 to the relay 75 so as to keep the relay 75 in the ON state.

In steps S103 to S109, a target steering torque Th * is set according to the steering angle θ and the vehicle speed V, and an assist current command value I is determined based on the steering torque Th, the target steering torque Th *, and the motor current Im. (Hereinafter, this control is referred to as MA-MT control).
I do.

More specifically, in S103, the CP
U21 reads the vehicle speed V from the vehicle speed sensor 16, and the next S
At 104, the phase compensator 35 of the CPU 21 performs phase compensation on the steering angle signal θ * to obtain a steering angle θ.

Further, in S105, the CPU 21
Reads the steering torque Th from the torque sensor 4 and performs phase compensation in the phase compensator 30 of the CPU 21.
In S106, the motor current Im is read from the motor drive current sensor 18.

Then, in the next S107, the CPU 2
1 calculates the target steering torque Th * with respect to the steering angle θ and the vehicle speed V in the target steering torque setting section 32. next,
In S108, the CPU 21 causes the current command value calculation unit 31 to execute the target steering torque Th * and the steering torque T
h, an assist current command value I for the vehicle speed V and the motor current Im is calculated. At the same time, the CPU 21 uses the subtracter 33 to calculate an assist current control value for the motor current Im.

Thereafter, in S109, the CPU 21
Performs PI control in the current control unit 34 to
Drive. Then, the CPU 21 returns to S101 so as to interrupt again.

On the other hand, in S102, the steering angle sensor 1
When the steering angle signal θ * satisfies the above-described expression (α) and the steering angle signal θ * is abnormal, the steering angle abnormality detection unit 71
If (CPU 21) determines, the process proceeds to S110. Then, in S110, a control signal is output from the steering angle abnormality detection unit 71 to the relay 75 so that the relay 75 is demagnetized and turned off.

Then, power is not supplied from the battery B to the motor 6, and the steering wheel 1 is set to manual steering in which the steering is not assisted by the motor 6 in any direction.

Therefore, according to the above embodiment, the following effects can be obtained. (1) In the above embodiment, the steering angle abnormality detection unit 71 is provided, and the steering angle abnormality detection unit 71
When it is determined that the steering angle signal θ * input to the controller 6 is abnormal, the relay 75 is demagnetized and turned off to cut off the power supply to the motor 6. Therefore, even when an abnormal steering angle signal θ * is input due to a disconnection of the steering angle sensor 17 and the abnormal assist current command value I is set in the current command value calculation unit 31, power supply to the motor 6 is not performed. Since it is not performed, the motor 6 does not assist the steering of the steering wheel 1, and the steering wheel 1 is in manual steering. Therefore, it is possible to prevent an abnormal assist state in which the steering feeling varies depending on the steering direction, and it is possible to improve safety.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG.
This will be described with reference to FIGS. The hardware configuration of the present embodiment is the same as that of FIG. 1 of the first embodiment, and the software configuration is partially different. Therefore, the first
In the configuration of the embodiment, the same or corresponding components are denoted by the same reference numerals, detailed description thereof will be omitted, and different portions will be mainly described.

FIG. 11 is a diagram corresponding to FIG. 2 of the first embodiment. In the present embodiment, unlike the first embodiment, a relay 75 is not connected to the motor driving device 24, and the CPU 21 newly has functions of an alternative operation unit 76 and a control switching unit 77.

In this embodiment, the CPU 21 and the current command value calculator 31 correspond to first assist current calculator, and the CPU 21 and the substitute calculator 76 correspond to second assist current calculator.

More specifically, the alternative operation unit 76 includes:
The steering torque Th output from the torque sensor 4 and phase-compensated by the phase compensator 30 is input. Further, the vehicle speed V detected by the vehicle speed sensor 16 is also input to the alternative calculation unit 76. The substitute calculation unit 76 calculates the input steering torque Th,
An alternative assist current command value Id is determined based on the vehicle speed V.

More specifically, the substitute calculation section 76 has a substitute assist map as shown in FIG. The alternative assist map is a three-dimensional map including the steering torque Th, the vehicle speed V, and the alternative assist current command value Id, and the alternative assist current command value Id is obtained according to a plurality of different predetermined vehicle speeds. ing. Further, the alternative assist current command value Id is determined so as to correspond to right steering and left steering. The alternative assist map is set so that the gradient of the alternative assist current command value Id becomes steeper as the vehicle speed V becomes lower than in the high speed side. Then, two alternative assist current command values related to the vehicle speed close to the vehicle speed V are obtained, and the vehicle speed V
Then, an alternative assist current command value Id for the vehicle speed V and the steering torque Th is calculated by a linear interpolation formula. Substitution operation section 76 outputs substitution assist current command value Id to control switching section 77 shown in FIG.

The control switching unit 77 includes the alternative operation unit 76
, An assist current command value I from the current command value calculation unit 31 and a control signal output from the steering angle abnormality detection unit 71 are input. Then, based on a control signal from the steering angle abnormality detection unit 71,
The control switching unit 77 switches and selects one of the assist current command value I and the alternative assist current command value Id, and outputs the selected value to the subtracter 33.

In the steering angle abnormality detecting section 71, when the above-mentioned equation (α) (that is, Δθ−θo ≧ θ1) is satisfied, the control switching section 77 sets the alternative assist current command value Id to 33. Output a control signal to select. On the other hand, when the above equation (α) is not satisfied, the control switching unit 77 outputs a control signal so as to select the assist current command value I.

Next, the steering angle abnormality detection processing in this embodiment will be described with reference to the flowchart shown in FIG.
First, in S101, the CPU 21 reads the steering angle signal θ * from the steering angle sensor 17, and in S102,
The steering angle abnormality detection unit 71 of the CPU 21 determines whether the input steering angle signal θ * is abnormal. Equation (α) described above
If the steering angle abnormality detection unit 71 determines that the steering angle signal θ * is normal, the process proceeds to S103. That is, a control signal is output from the steering angle abnormality detection unit 71 to the control switching unit 77 so that the control switching unit 77 selects the assist current command value I. And S103 ~
In S109, MA-MT control is performed.

On the other hand, in S102, the steering angle sensor 1
When the steering angle signal θ * satisfies the above-described expression (α) and the steering angle signal θ * is abnormal, the steering angle abnormality detection unit 71
If (CPU 21) determines, the process proceeds to S210. That is, a control signal is output from the steering angle abnormality detection unit 71 to the control switching unit 77 so that the control switching unit 77 selects the alternative assist current command value Id. And S210
In steps S213 to S213, the assist current is determined based on the vehicle speed V and the steering torque Th to control the motor 6 (hereinafter, this control is referred to as alternative assist control).

More specifically, in S210, the CP
U21 reads the vehicle speed V from the vehicle speed sensor 16. next,
In S211, the CPU 21 reads the steering torque Th from the torque sensor 4 and performs phase compensation in the phase compensator 30 of the CPU 21.

Then, in the next S212, the CPU 2
1 denotes the vehicle speed V and the steering torque Th in the alternative calculation unit 76.
Is calculated. At the same time, the CPU 21 uses the subtracter 33 to calculate an assist current control value for the substitute assist current command value Id and the motor current Im.

Thereafter, in S213, the CPU 21
Performs PI control in the current control unit 34 to
Drive. Then, the CPU 21 returns to S210 as a process when the steering angle signal θ * is abnormal, and performs the interruption work again.

As a result, even when a disconnection or the like occurs in the steering angle sensor 17 and an abnormal steering angle signal θ * is detected, based on the alternative assist current command value Id calculated from the vehicle speed V and the steering torque Th. Assistance from the motor 6 to the steering wheel 1 is performed.

Therefore, according to the present embodiment, the following effects can be obtained. (2) In the present embodiment, the steering angle abnormality detection unit 71 is provided,
When it is determined that the steering angle θ input to the steering angle abnormality detection unit 71 is abnormal, the current command value output by the control switching unit 77 is switched, the MA-MT control is stopped, and the vehicle speed V and the steering torque Th The alternative assist control according to is performed. For this reason, when an abnormal steering angle signal θ * is input due to disconnection of the steering angle sensor 17 or the like and an abnormal assist command current value I is set in the current command value calculation unit 31, the steering angle abnormality detection unit 71 Also, the MA-MT control is not performed by the control switching unit 77. On the other hand, in the alternative assist control,
An assisting force corresponding to the vehicle speed V and the steering torque Th is generated, so that a good steering feeling can be continuously obtained from low speed to high speed running. Therefore, the same effect as the effect (1) in the first embodiment is obtained, and further, the operability of the steering wheel 1 is not impaired.

Note that each of the above embodiments may be changed to another example as follows. In each of the above embodiments, the control device for the column and pinion assist type electric power steering device
Although the configuration is such that the A-MT control is performed, it may be embodied as a control device of a rack assist type electric power steering device as shown in FIG.

In the drawing, the motor 6 arranged coaxially with the rack 10 transmits the auxiliary steering force generated by the motor 6 to the rack 10 via the ball nut mechanism 6a. Therefore, when the motor 6 rotates, the rotation speed is reduced by the ball nut mechanism 6a and transmitted to the rack 10. The rack 10 can change the direction of the front wheels 14 provided on the knuckle 13 via the tie rods 12 to change the traveling direction of the vehicle. The other configuration has the same configuration as that of the first embodiment, and thus the detailed description is omitted.

In this embodiment, the same configuration as the electrical configuration of the first embodiment is adopted, and only the method of determining the assist current command value I is different from that of the first embodiment. How to determine the value I will be described below.

In the case of the rack assist type, the steering torque T
h, the rack thrust F at the time of the motor current Im is obtained by the following equation (B). F = Fm + Fh (B) Here, Fm is a thrust assisted by the motor 6, and Fh is a thrust by steering the steering wheel, and can be obtained by the following equations.

Fm = 2π · Tm · ηb / L (C) Fh = 2π · Th · ηp / St (D) In the above (C), Tm represents motor torque, and Tm = Kt × Im. … (E)

Here, Tm is the motor torque, ηb is the ball screw efficiency of the ball nut mechanism 6a, and L is the ball screw lead. Th is the steering torque, ηp is the rack &
The rack & pinion gear efficiency, St, of the pinion mechanism 11 is its stroke ratio. Kt is a torque constant.

Therefore, using the above equation (B), the target steering torque Th * at the vehicle speed V, the steering angle θ, and the rack thrust F at the assist current command value I (hereinafter, this thrust is referred to as F (Th *, I), and a rack thrust F at the time of the steering torque Th and the motor current Im (hereinafter, this thrust is referred to as F
(Th, Im). ) Are set equal to each other.

When F (Th *, I) = F (Th, Im),
When I is obtained by substituting the above (C), (D) and (E), the following equation is obtained. I = Im + (Th−Th *) L · ηp / (St · Kt ·
ηb) The assist current command value I thus obtained is output to the subtractor 33.

If the assist current command value I has the opposite sign to the target steering torque Th *, that is, reverse assist, the assist current command value I is determined to be zero and output to the subtractor 33. Thereafter, processing is performed in the same manner as in the first embodiment.

In the first embodiment, when the input steering angle signal θ * is abnormal, the steering angle abnormality detecting unit 71 of the CPU 21 demagnetizes the relay 75 and turns off the control signal. However, it is also possible to stop the motor drive without providing the relay 75. That is, the control signal from the steering angle abnormality detection unit 71 is set to be output to the current control unit 34. When the steering angle abnormality detection unit 71 detects an abnormality in the steering angle signal θ *, the current control unit 3
4 to output a control signal to prohibit the PWM operation by the current control unit 34. As a result, the motor driving device 2
The operation of the power element in 4 is stopped, and accordingly,
The driving of the motor 6 is stopped. Even in this case, the steering wheel 1 is in a manual steering state regardless of which direction the steering is performed, and the same effect as the effect (1) of the first embodiment is obtained.

Further, the turning off of the relay 75 in the first embodiment may be combined with the control for inhibiting the PWM control.

[0101]

As described in detail above, according to the first or second aspect of the present invention, high safety is maintained even if an abnormal steering angle is detected due to an abnormality in the steering angle sensor. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a control device of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of the control device.

FIG. 3 is a flowchart of a target steering torque setting routine.

FIG. 4 is a functional block diagram of the phase compensator 35.

FIG. 5 is an explanatory diagram of a target steering torque setting map.

FIG. 6 is an explanatory diagram of a dead zone.

FIG. 7 is a block diagram of a current command value calculator.

FIG. 8 is an explanatory view of calculating a dead zone width.

FIG. 9 is a block diagram of a steering angle abnormality detection unit.

FIG. 10 is a flowchart showing a steering angle abnormality detection process.

FIG. 11 is a block diagram of a control device of the electric power steering device according to the second embodiment.

FIG. 12 is an explanatory diagram of an alternative assist map.

FIG. 13 is a flowchart showing a steering angle abnormality detection process.

FIG. 14 is a schematic diagram of a control device according to an electric power steering device of another embodiment.

FIG. 15 is a schematic diagram of a control device according to a conventional electric power steering device.

FIG. 16 is an explanatory diagram of a map for calculating a target steering angle torque.

FIG. 17 is an explanatory diagram of a map for calculating a target steering angle torque.

[Explanation of symbols]

6 ... motor, 21 ... CPU (control means, target steering torque setting means, assist current calculation means, first assist current calculation means, second assist current calculation means, steering angle abnormality detection means), 31 ... current command value calculation section (Assist current calculation means, first assist current calculation means), 32: target steering torque setting section (target steering torque setting means), 71: steering angle abnormality detection section (steering angle abnormality detection section), 76: alternative calculation section ( Second assist current calculating means).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B62D 113: 00 B62D 113: 00 119: 00 119: 00 F term (Reference) 3D032 CC33 CC40 DA03 DA15 DA23 DA64 DC08 DC18 DD01 DD05 DD10 DD17 EA01 EB04 EB06 EC23 GG01 3D033 CA03 CA13 CA20 CA21 CA31 5H571 AA03 BB07 CC04 GG04 HD03 JJ03 JJ04 JJ25 LL22 LL32 LL43

Claims (2)

[Claims] 1. A control device for an electric power steering device comprising a control means for controlling a motor based on an assist current command value, wherein a target steering torque is set based on an input steering angle and a vehicle speed. Means, an assist current calculating means for calculating an assist current command value based on a steering torque, the target steering torque, and a motor current of the motor, and a steering angle abnormality detection for determining whether or not the input steering angle is abnormal. Means for controlling the electric power steering apparatus, wherein when the steering angle abnormality detecting means detects an abnormality, the control means stops driving the motor. 2. A control device for an electric power steering device comprising a control means for controlling driving of a motor based on an assist current command value, wherein a target steering torque is set based on the input steering angle and vehicle speed. Means, first assist current calculation means for calculating an assist current command value based on the steering torque, the target steering torque, and the motor current of the motor; and an assist current command value based on the input vehicle speed and steering torque. A second assist current calculating means for calculating; and a steering angle abnormality detecting means for determining whether or not the input steering angle is abnormal. Or an electric power drive for driving a motor based on an assist current command value calculated by any of the second assist current calculation means. The control device of the bearings device.