JP3630281B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus that directly applies the power of an electric motor to a steering system to reduce the steering force of the driver, and in particular, an electric power steering apparatus that notifies the driver of a change in the steering reaction force and performs appropriate steering. About.
[0002]
[Prior art]
In a conventional electric power steering device, the difference between the slip angle (βf) of the front wheel of the vehicle and the slip angle (βr) of the rear wheel of the vehicle based on the vehicle speed, the yaw angular velocity, and the steering angle (tire cut angle) (hereinafter, Angle difference (referred to as βfr = βf−βr), a correction amount of vehicle behavior (oversteer state, understeer state, etc.) is determined based on the angle difference βfr, and the target steering torque signal based on the steering torque is determined as the angle difference. By driving the electric motor with a correction amount corresponding to βfr, the auxiliary torque generated by the electric motor is corrected and applied to the steering system, and the steering reaction force transmitted from the road via the steering wheel is determined according to the vehicle behavior. There are known devices that allow a driver to sense and allow the driver to perform an appropriate steering operation according to vehicle behavior.
[0003]
[Problems to be solved by the invention]
The conventional electric power steering apparatus is configured so that the driver can perform an appropriate steering operation by correcting the target steering torque signal with a correction amount corresponding to the angle difference βfr according to the vehicle behavior when the vehicle moves forward. However, there is a problem that the vehicle behavior becomes unstable when the vehicle moves backward.
[0004]
For example, when the vehicle moves backward, the caster angle set for the suspension of the front wheels is opposite to the direction in which the vehicle acts when the vehicle is moving forward. Is unstable and staggers.
Further, the force to return the handle to the center (steering angle 0 degree) becomes weak.
[0005]
Such a phenomenon becomes conspicuous in a vehicle having an assist torque that can set the steering force to an optimum lightness in a low vehicle speed region in order to improve steering.
[0006]
In the vehicle having the steering characteristics as described above, there is a problem that it is difficult for the driver with low driving skill, for example, a driver who has just obtained a license, to operate the steering wheel when the vehicle moves backward.
[0007]
Further, in the conventional electric power steering apparatus, the control for changing the assist torque according to the vehicle behavior is set to be executed in a vehicle speed region (for example, 30 Km / h or more) in which the vehicle behavior changes greatly. Has been.
[0008]
However, even when the vehicle travels in a low vehicle speed range such as when traveling on a low μ road or during a U-turn, the vehicle behavior may change greatly. Under such conditions, the auxiliary torque depends on the vehicle behavior. It is desired from a driver with a high driving skill to change this.
[0009]
The electric power steering device that changes the auxiliary torque according to the vehicle behavior even when traveling in the low vehicle speed range makes the vehicle behavior unstable when the vehicle is moving backward, and therefore assists according to the vehicle behavior even when the vehicle is moving backward. Changing the torque is desirable for drivers with high driving skills.
[0010]
The present invention has been made to solve such problems, and a first object of the present invention is to provide an electric power steering device that prohibits a driver with low driving skill from changing the auxiliary torque when the vehicle moves backward. There is to do.
[0011]
A second object of the present invention is to provide an electric power steering device capable of changing an auxiliary torque according to the vehicle behavior when the vehicle is reversing for a driver with high driving skill.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, an electric power steering apparatus according to the present invention includes a reverse detection means for detecting the reverse of the vehicle, and the control means corrects the vehicle behavior determination means based on a reverse signal from the reverse detection means. A correction amount control means for controlling the amount is provided.
[0013]
The electric power steering apparatus according to the present invention includes a reverse detection means for detecting the reverse of the vehicle, and the control means controls the correction amount from the vehicle behavior determination means based on the reverse signal from the reverse detection means. Since the control means is provided, the auxiliary torque can be corrected or prohibited according to the vehicle behavior not only when the vehicle moves forward but also when the vehicle moves backward.
[0014]
Further, the correction amount control means of the electric power steering apparatus according to the present invention prohibits the output of the correction amount from the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle. Features.
[0015]
The correction amount control means of the electric power steering apparatus according to the present invention prohibits the output of the correction amount from the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle. It is possible not to execute the correction of the auxiliary torque according to the vehicle behavior for a driver having a low speed.
[0016]
Furthermore, the correction amount control means of the electric power steering apparatus according to the present invention reverses the polarity of the yaw angular velocity signal supplied to the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle. The target current signal is corrected with the correction amount from the vehicle behavior determining means.
[0017]
The correction amount control means of the electric power steering apparatus according to the present invention reverses the polarity of the yaw angular velocity signal supplied to the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle, Since the target current signal is corrected with the correction amount from the vehicle behavior determining means, the target current signal can be corrected according to the vehicle behavior in the same manner as when the vehicle moves forward when the vehicle moves backward.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
In the present invention, even when the vehicle is moving backward, the driver senses the understeer state or the oversteer state of the vehicle as a steering reaction force through the steering wheel.
[0019]
FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention.
In FIG. 1, an electric power steering apparatus 1 includes a rack and pinion mechanism 5 including a steering wheel 2, a steering shaft 3, a hypoid gear 4, a pinion 5a and a rack shaft 5b, a tie rod 6, a front wheel 7 for steering wheels, and an auxiliary torque. An electric motor 8, a control means 13, an electric motor driving means 14, and an electric motor current detecting means 15 acting on the steering system are provided.
[0020]
The electric power steering device 1 detects a yaw angular velocity acting on the vehicle, outputs a yaw angular velocity signal Y converted into an electric signal corresponding to the yaw angular velocity, detects a front wheel turning angle, A turning angle sensor 10 for outputting a turning angle signal δ converted to an electrical signal corresponding to the turning angle of the front wheel, a vehicle speed sensor 11 for detecting a vehicle speed and outputting a vehicle speed signal V converted to an electrical signal corresponding to the vehicle speed, A steering torque sensor 12 that detects a steering torque acting on the steering wheel 2 and outputs a steering torque signal T converted into an electric signal corresponding to the steering torque, detects a reverse (back) of the vehicle, and is converted into an electric signal. Vehicle reverse detection means 16 for outputting the reverse signal R.
The turning angle signal δ may be calculated from the steering angle of the steering shaft.
Further, the vehicle reverse detection means 16 constituting the reverse detection means detects a signal corresponding to the reverse (R) position of the shift lever (for example, a voltage detection value of the potentiometer), and the reverse is converted into, for example, an H level signal. The signal R is supplied to the control means 13.
[0021]
The yaw angular velocity signal Y, the turning angle signal δ, and the steering torque signal T each have a magnitude and direction, and are supplied to the control means 13.
As for the directions of the yaw angular velocity signal Y, the turning angle signal δ, and the steering torque signal T, the clockwise direction is positive (plus) and the counterclockwise direction is negative (minus).
The vehicle speed signal V is assumed to have only a magnitude and no direction.
[0022]
When the steering wheel 2 is steered, the manual steering torque applied to the steering shaft 3 is converted from the rotational force of the pinion 5a to the axial movement of the rack shaft 5b via the rack and pinion mechanism 5, and via the tie rod 6. The steering of the front wheel 7 is changed.
[0023]
In order to assist manual steering torque, when the electric motor 8 is driven in response to the steering torque signal T, the electric motor torque is converted into auxiliary torque (assist torque) boosted via the hypoid gear 4 and the steering shaft 3 It acts on the vehicle and reduces the driver's steering force.
[0024]
The control means 13 is composed of various calculation means, processing means, determination means, switch means, signal generation means, memory, etc. based on a microprocessor, and generates a target current signal (IMS) corresponding to the steering torque signal T. An electric motor control signal VO (for example, an on signal, an off signal, and a PWM) corresponding to a difference (negative feedback) between the target current signal (IMS) and the electric motor current signal IMF corresponding to the electric motor current IM detected by the electric motor current detecting means 15 A mixed signal of signals) is generated, and the driving of the motor driving means 14 is controlled so that this difference becomes zero quickly.
[0025]
The control means 13 includes a slip angle difference estimation means, a correction means, and the like. Based on the yaw angular velocity signal Y, the turning angle signal δ, the vehicle speed signal V, and the vehicle dimensional parameter (wheel base), the front wheel slip angle and the rear angle are determined. A difference in the slip angle of the wheel (angle difference signal) is estimated by calculation, and an understeer correction amount and an oversteer correction amount are determined based on the magnitude of the difference (angle difference signal), and the target current signal (IMS) is determined based on the correction amount. ) Is corrected.
[0026]
Further, the control means 13 compares the direction signal (P) of the difference between the slip angle of the front wheels and the slip angle of the rear wheels (angle difference signal) and the direction signal (N) of the yaw angular velocity signal Y, thereby It is determined whether (vehicle behavior) is an understeer region or an oversteer region.
[0027]
Further, when the control means 13 detects the reverse of the vehicle and determines whether the vehicle state (vehicle behavior) is the understeer region or the oversteer region, the target current signal (understeer correction amount and oversteer correction amount) is used. A correction amount control means for correcting or prohibiting IMS) is provided, and correction is executed according to the driving skill of the driver when the vehicle is moving backward, or correction is prohibited.
[0028]
The motor driving means 14 is constituted by a bridge circuit composed of switching elements such as four power FETs (field effect transistors) and insulated gate / bipolar transistors (IGBT), for example, and PWM (pulse width modulation) based on the motor control signal VO. ) Is output, and the electric motor 8 is PWM-driven in the forward rotation or the reverse rotation.
[0029]
The motor current detection means 15 detects the motor current IM converted into a voltage by a resistor or a hall element connected in series with the motor 8 and feeds back the motor current signal IMF corresponding to the motor current IM to the control means 13. (Negative feedback).
[0030]
FIG. 2 is a block diagram showing a basic part of an embodiment of the electric power steering apparatus according to the present invention.
In FIG. 2, the control means 13 of the electric power steering apparatus 1 includes a target current signal setting means 21, a deviation calculation means 22, a drive control means 23, a vehicle behavior determination means 24, a correction means 25, and a correction amount control means 17.
[0031]
The target current signal setting means 21 stores in advance a steering torque signal T—target current signal IMS characteristic data shown in FIG. 6 and a vehicle speed signal V—vehicle speed coefficient KT characteristic data shown in FIG. A new vehicle speed signal V obtained by multiplying the target current signal IMS corresponding to the steering torque signal T detected by the steering torque sensor 12 and the vehicle speed coefficient KT corresponding to the vehicle speed signal V detected by the vehicle speed sensor 11 as a parameter. A target current signal IMS is supplied to the correction means 25.
The new target current signal IMS using the vehicle speed signal V as a parameter is set so as to decrease as the vehicle speed signal V increases even if the torque signal T is the same, thereby ensuring the stability of steering in the high vehicle speed region.
The sign (polarity) of the target current signal IMS is positive (+) when the steering torque signal T is clockwise (for example, right steering), and the steering torque signal T is counterclockwise (for example, left). In the case of (steering), it is minus (−).
[0032]
The deviation calculating means 22 has a subtractor or a subtracting function and has a difference ΔI (= IMH−IMF) between the target current signal IMH supplied from the correcting means 25 and the motor current signal IMF supplied from the motor current detecting means 15. And the deviation signal ΔI (= IMH−IMF) is supplied to the drive control means 23.
[0033]
The drive control unit 23 includes a PID controller, an electric motor control signal generation unit, and the like, and after performing proportional (P), integral (I) and differential (D) control on the deviation signal ΔI supplied from the deviation calculating unit 22, A motor control signal VO of PWM corresponding to right steering or left steering of the steering wheel (steering wheel 2) is generated based on a mixed signal obtained by mixing these signals subjected to proportional / integral / differential (PID) control, and the motor control signal is generated. VO is supplied to the motor driving means 14.
[0034]
The vehicle behavior determination unit 24 includes a slip angle difference estimation unit, a direction determination unit, a selection unit, an understeer correction amount output unit, an oversteer correction amount output unit, and the like. The vehicle speed signal V supplied from the vehicle speed sensor 11 and the yaw angular velocity sensor 9 are provided. The difference between the front wheel slip angle (βf) of the vehicle and the rear wheel slip angle (βr) of the vehicle (angle difference βfr = βf−) from the yaw angular velocity signal Y supplied from the vehicle and the cut angle signal δ supplied from the cut angle sensor 10. βr) is calculated, understeer correction amount (DA) and oversteer correction amount (DO) are generated based on this angular difference βfr, and correction signal ID corresponding to understeer correction amount (DA) or oversteer correction amount (DO) is corrected. This is supplied to the control means 17.
[0035]
FIG. 3 is a block diagram of the main part of the vehicle behavior determining means according to the present invention.
In FIG. 3, the vehicle behavior determination means 24 includes a vehicle speed coefficient generation means 26, a slip angle difference estimation means 30, a selection means 31, a direction determination means 32, an understeer correction amount output means 33, an oversteer correction amount output means 34, and a multiplication means 35. , Multiplication means 36, addition means 37, angle difference change amount calculation means 39, and angle difference change coefficient generation means 40.
[0036]
The vehicle speed coefficient generating means 26 includes a memory such as a ROM, stores characteristic data of the vehicle speed signal V and the vehicle speed coefficient KR shown in FIG. 8 in advance, and corresponds when the vehicle speed signal V is supplied from the vehicle speed sensor 11. The vehicle speed coefficient KR is read out and provided to the multiplication means 35 and the multiplication means 36.
[0037]
The slip angle difference estimation means 30 has a memory and a calculation function, and is based on a vehicle speed signal V, a yaw angular speed signal Y, a turning angle signal δ, and a vehicle dimension parameter L (for example, a wheel base) preset in the memory. The difference βfr (= βf−βr) between the front wheel slip angle (βf) and the rear wheel slip angle (βr) is calculated from the angle, and the angle difference signal βfr is selected by the selection means 31, the direction determination means 32, and the angle difference change amount calculation means 39. To supply.
[0038]
[Expression 1]
βfr = Y * L / V−δ
[0039]
Note that the front wheel slip angle (βf) and the rear wheel slip angle (βr) represent the angle in the tire traveling direction with reference to the tire direction, so that when the steering wheel is turned clockwise (right steering), the front wheel The advancing direction of the tire is counterclockwise with respect to the tire direction. When the clockwise direction is positive (plus), the front wheel slip angle (βf) is negative (minus).
Similarly, the rear wheel slip angle (βr) is also negative (minus), and the direction (sign) of the angle difference signal βfr is the absolute value of the rear wheel slip angle (βr) | βr | is the absolute value of the front wheel slip angle (βf). Until | βf | or more (| βr | ≧ | βf |), it is expressed as negative (minus).
[0040]
Further, when the steering wheel is turned counterclockwise (left steering), the tire traveling direction is clockwise with respect to the direction of the front tire, and when the clockwise direction is positive (plus), the front wheel slip angle (βf) The direction of is positive.
Similarly, the rear wheel slip angle (βr) is also positive (plus), and the direction (sign) of the angle difference signal βfr is the absolute value of the rear wheel slip angle (βr) | βr | is the absolute value of the front wheel slip angle (βf). Until | βf | or more (| βr | ≧ | βf |), it is expressed as positive (plus).
[0041]
Further, instead of the yaw angular velocity signal Y supplied to the direction determining means 32, a lateral acceleration G may be substituted.
[0042]
The selection means 31 has a soft control switch function, switches the switch based on the determination signal HO supplied from the direction determination means 32, and outputs the angle difference signal βfr supplied from the slip angle difference estimation means 30 to the understeer correction amount output. This is supplied to the means 33 or the oversteer correction amount output means 34.
[0043]
The direction determination unit 32 has a sign comparison function and is based on the direction signal P of the angular difference signal βfr supplied from the slip angle difference estimation unit 30 and the direction signal N of the yaw angular velocity signal Y supplied from the yaw angular velocity sensor 9. Thus, when the direction signal P and the direction signal N match (the signs are the same), for example, the determination signal HO at the H level is supplied to the selection means 31, and the direction signal P and the direction signal N are different (the signs are different). In this case, for example, an L level determination signal HO is supplied to the selection means 31.
[0044]
When the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y are different (mismatch), for example, the yaw angular velocity Y is clockwise and the counterclockwise slip angle (βf) of the front wheel is rearward. When the wheel is larger than the counterclockwise slip angle (βr), the direction signal N of the yaw angular velocity signal Y is positive (+) and the direction signal P of the angular difference signal βfr is negative (−), so that the vehicle The selection means 31 selects the understeer correction amount output means 33 by determining that the behavior is an understeer region (solid line display).
[0045]
On the other hand, when the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y are the same (match), for example, the yaw angular velocity Y is clockwise and the counterclockwise slip angle (βr of the rear wheel) ) Is larger than the counterclockwise slip angle (βf) of the front wheel, the direction signal N of the yaw angular velocity signal Y is plus (+) and the direction signal P of the angular difference signal βfr is plus (+). The selection means 31 selects the oversteer correction amount output means 34 (denoted by a broken line) by determining that the vehicle behavior is an oversteer region.
[0046]
Note that the relationship between the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y has been described in the case where the steering wheel is in the clockwise direction (right steering) while the vehicle is moving forward. When the steering wheel is moving in the counterclockwise direction (left steering), the direction signal P of the angular difference signal βfr and the direction signal N of the yaw angular velocity signal Y are handled in reverse to the case of right steering. The understeer region or oversteer region of the vehicle behavior can be determined.
[0047]
Understeer area with strong vehicle behavior means that the vehicle will not bend any further even if the steering wheel is further turned from the current steering state, and it is better to let the driver feel the reaction force and return the steering wheel. This is the steering area to notify.
[0048]
Since the reaction force correction is not necessary in the weak understeer region, the dead zone region of the understeer correction amount DA for the angular difference signal βfr is set large as shown in FIG.
[0049]
On the other hand, the strong oversteer region of the vehicle is a state where the vehicle may spin if it is as it is, and makes the driver feel a strong reaction force to facilitate counter-steering.
[0050]
The understeer correction amount output means 33 includes a memory such as a ROM, stores characteristic data of the absolute value | βfr | of the angle difference signal and the understeer correction amount DA shown in FIG. When the signal βfr is supplied, the corresponding understeer correction amount DA is read, and the understeer correction amount signal DA is supplied to the multiplication unit 35.
[0051]
The oversteer correction amount output means 34 includes a memory such as a ROM, stores characteristic data of the absolute value | βfr | of the angle difference signal and the oversteer correction amount DO shown in FIG. When the signal βfr is supplied, the corresponding oversteer correction amount DO is read, and the oversteer correction amount signal DO is supplied to the multiplication means 36.
[0052]
The understeer correction amount signal DA and the oversteer correction amount signal DO are expressed as positive (+) when the steering wheel is in the clockwise direction (right steering) with the vehicle moving forward, and the vehicle is moving forward. When the steering wheel is in the counterclockwise direction (left steering), it is expressed as negative (-).
[0053]
The understeer correction amount DA and oversteer correction amount DO have their own dead zones as shown in FIGS. 9 and 10, respectively, so that optimum correction according to the understeer state or oversteer state can be performed. .
[0054]
The multiplication means 35 has a software-controlled multiplication function, multiplies the vehicle speed coefficient KR, the understeer correction amount signal DA, and the angle difference change coefficient KV, and performs an understeer correction amount signal IDA (= KR * KV * DA as a subtraction correction signal). ) Is supplied to the adding means 37.
[0055]
Since the understeer correction amount signal IDA corrects the understeer correction amount DA shown in FIG. 9 with the vehicle speed coefficient KR shown in FIG. 8, understeer correction is performed in all of the low vehicle speed region, the medium vehicle speed region, and the high vehicle speed region except for the extremely low stop speed region. It can be set to the same characteristic as the quantity DA.
[0056]
The multiplication means 36 has a software-controlled multiplication function, multiplies the vehicle speed coefficient KR, the oversteer correction amount signal DO, and the angular difference change coefficient KV, and performs an oversteer correction amount signal IDO (= KR * KV * DO) as a subtraction correction signal. ) Is supplied to the adding means 37.
[0057]
Since the oversteer correction amount signal IDO corrects the oversteer correction amount DO shown in FIG. 10 by the vehicle speed coefficient KR shown in FIG. 8, oversteer correction is performed in all of the low vehicle speed region, the medium vehicle speed region, and the high vehicle speed region excluding the extremely low stop speed region. It can be set to the same characteristics as the quantity DO.
The oversteer correction amount DO is set so that the dead zone is narrower and the inclination is smaller than the understeer correction amount DA.
[0058]
The adding means 37 has a software-controlled adding function, and an understeer correction amount signal IDA (= KR * KV * DA) supplied from the multiplying means 35 and an oversteer correction amount signal IDO (= KR) supplied from the multiplying means 36. * KV * DO) is added, and one of the understeer correction amount signal IDA and the oversteer correction amount signal IDO is supplied to the correction amount control means 17 shown in FIG. 2 as the correction signal ID.
[0059]
The angular difference change amount calculation means 39 has a differential calculation function, performs a differential calculation on the angle difference signal βfr supplied from the slip angle difference estimation means 30, and determines the angular difference change amount signal DV (= dβfr / dt) as the angular difference. This is supplied to the change coefficient generator 40.
[0060]
The angle difference change coefficient generating means 40 includes a memory such as a ROM, stores characteristic data of the angle difference change amount DV and the angle difference change coefficient KV shown in FIG. 11 in advance, and is supplied with an angle difference change amount signal DV. Then, the corresponding angular difference change coefficient KV is read out and supplied to the multiplication means 35 and the multiplication means 36.
[0061]
The angle difference change amount DV represents a change in the angle difference signal βfr, and thus represents a temporal change in the vehicle behavior. Therefore, the understeer correction amount signal IDA (= KR * KV * DA) corresponding to the sudden change in the vehicle behavior. Alternatively, the oversteer correction amount signal IDO (= KR * KV * DO) can be generated.
[0062]
Returning to FIG. 2, the correction unit 25 has a subtraction function, and a deviation (= IMS−ID) between the target current signal IMS supplied from the target current signal setting unit 21 and the correction signal ID supplied from the correction amount control unit 24. ) And is supplied to the deviation calculating means 22 as a corrected new target current signal IMH (= IMS-ID).
In this way, the correction means 25 subtracts and corrects the target current signal IMS with the correction signal ID (understeer correction amount signal IDA or oversteer correction amount signal IDO).
[0063]
The correction amount control means 17 prohibits the supply of the correction signal ID supplied from the vehicle behavior determination means 24 to the correction means 25 when the vehicle moves backward based on the H level reverse signal R supplied from the vehicle reverse detection means 16. Or control the execution.
[0064]
As described above, the electric power steering apparatus 1 according to the present invention includes the reverse detection means 16 for detecting the reverse of the vehicle, and the control means 13 is based on the reverse signal R from the reverse detection means 16 and the vehicle behavior determination means. Since the correction amount control means 17 for controlling the correction amount ID from 24 is provided, correction of the auxiliary torque is executed or prohibited not only when the vehicle is moving forward but also when the vehicle is moving backward according to the vehicle behavior. Can do.
[0065]
FIG. 4 is a block diagram showing the principal part of one embodiment of the correction amount control means according to the present invention.
In FIG. 4, the correction amount control means 17 is constituted by a soft control switch means. When the vehicle reverse detection means 16 detects the reverse of the vehicle and an H level reverse signal R is supplied, the switch is closed. Switching from the formation (make: solid line display) state to the opening (break: broken line display), the supply of the correction signal ID supplied from the vehicle behavior determination means 24 to the correction means 25 is prohibited.
[0066]
On the other hand, when the vehicle is in the forward state, the correction amount control unit 17 is supplied with the L level reverse signal R from the vehicle reverse detection unit 16, and thus the switch is kept closed (make: solid line display). Then, the correction signal ID supplied from the vehicle behavior determination means 24 is supplied to the correction means 25.
[0067]
As described above, the correction amount control means 17 of the electric power steering apparatus 1 according to the present invention provides the correction amount ID from the vehicle behavior determination means 24 based on the reverse signal R when the reverse detection means detects the reverse of the vehicle. Therefore, it is possible to prevent the driver having a low driving skill from performing the correction of the auxiliary torque in accordance with the vehicle behavior when the vehicle moves backward.
[0068]
Next, a description will be given of a driver capable of sensing the vehicle behavior as the steering reaction force by executing the correction of the auxiliary torque with respect to the vehicle behavior even when the vehicle is moving backward, for a driver with high driving skill.
[0069]
If the steering wheel is steered clockwise (right steering) when the vehicle is moving backward, the direction of the vehicle speed signal V and the turning angle signal δ is the same as when the steering wheel is steered clockwise (right steering) while the vehicle is moving forward. Only the yaw angular velocity signal Y turns the vehicle body counterclockwise, so the direction signal N is negative (-) and the polarity is reversed.
[0070]
In order to handle the correction amount ID output from the vehicle behavior determination means 24 even when the vehicle is moving backward, the problem is solved by reversing (reversing) the sign of the yaw angular velocity signal Y when the vehicle moves backward. be able to.
[0071]
FIG. 5 is a block diagram showing the principal part of another embodiment of the correction amount control means according to the present invention.
In FIG. 5, the correction amount control means 18 includes an inverted sign generation means 41 and a multiplication means 42, and is arranged between the yaw angular velocity sensor 9 and the yaw angular velocity signal Y input terminal of the vehicle behavior determination means 24 in the control means 28.
FIG. 5 shows a state in which the steering wheel is steered clockwise (right steering) when the vehicle is moving backward. In this state, the yaw angular velocity signal Y is negative (−) and is represented by the yaw angular velocity signal −Y.
[0072]
The inversion code generation means 41 is composed of a memory such as a ROM, stores constant 1 and constant −1 in advance, reads constant 1 when L level backward signal R is supplied, and multiplies constant 1 Supply to means 42.
[0073]
Further, the inverted code generation means 41 reads the constant −1 when the H level backward signal R is supplied, and supplies the constant −1 to the multiplication means 42.
[0074]
The multiplication unit 42 has a multiplication function, and multiplies the yaw angular velocity signal Y (or -Y) supplied from the yaw angular velocity sensor 9 by the constant 1 (or -1) supplied from the inversion code generation unit 41. (Y * 1 or -Y * -1) and a new yaw angular velocity signal Y is supplied to the vehicle behavior determination means 24.
[0075]
As described above, the direction signal N of the new yaw angular velocity signal Y is obtained when the steering wheel is steered to the right while the vehicle is moving forward, or when the steering wheel is steered to the right while the vehicle is moving backward. Both are positive (+).
[0076]
On the other hand, the direction signal N of the new yaw angular velocity signal Y is negative when the steering wheel is left-steered while the vehicle is moving forward or when the steering wheel is left-steered while the vehicle is moving backward. (-).
[0077]
Therefore, the direction signal N of the yaw angular velocity signal Y can be determined only by the right steering or left steering state of the steering wheel, regardless of whether the vehicle is moving forward or backward.
As a result, the sign (polarity) of the correction signal ID output from the vehicle behavior determination means 24 can be determined only by the right steering or left steering state of the steering wheel, regardless of whether the vehicle is moving forward or backward.
[0078]
As described above, the correction amount control means 18 of the electric power steering apparatus 1 according to the present invention provides the yaw supplied to the vehicle behavior determination means 24 based on the reverse signal R when the reverse detection means detects the reverse of the vehicle. Since the polarity of the angular velocity signal Y is reversed and the target current signal IMS is corrected with the correction amount ID from the vehicle behavior determination means 24, the auxiliary torque is also applied in accordance with the vehicle behavior in the same manner as when the vehicle moves forward when the vehicle moves backward. Can be corrected.
[0079]
It should be noted that the setting of prohibition of auxiliary torque correction shown in FIG. 4 or correction execution of auxiliary torque shown in FIG. 5 may be switched by an operation of a driver.
Further, it may be set at the time of factory shipment or at a service station.
[0080]
【The invention's effect】
As described above, the electric power steering apparatus according to the present invention includes the reverse detection means for detecting the reverse of the vehicle, and the control means corrects from the vehicle behavior determination means based on the reverse signal from the reverse detection means. A correction amount control means for controlling the amount is provided, and correction of auxiliary torque can be executed or prohibited according to vehicle behavior not only when the vehicle moves forward but also when the vehicle moves backward. It is possible to improve the steering feeling when the driver with high driving skill moves backward.
[0081]
Further, the correction amount control means of the electric power steering apparatus according to the present invention prohibits the output of the correction amount from the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle. Since the correction of the assist torque according to the vehicle behavior is not executed for the driver with low skill, it is possible to provide a steering feeling without a sense of incongruity to the driver with low driving skill.
[0082]
Furthermore, the correction amount control means of the electric power steering apparatus according to the present invention reverses the polarity of the yaw angular velocity signal supplied to the vehicle behavior determination means based on the reverse signal when the reverse detection means detects the reverse of the vehicle. The target current signal is corrected with the correction amount from the vehicle behavior determination means, and the target current signal can be corrected according to the vehicle behavior in the same manner as when the vehicle moves forward when the vehicle moves backward. By sensing as a steering reaction force, it is possible to improve the steering feeling of the driver with high driving skill when the vehicle moves backward.
[0083]
Therefore, it is possible to provide an electric power steering apparatus that can detect the vehicle behavior as a steering reaction force even when the vehicle is moving backward and improve the steering feeling of the driver.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an electric power steering apparatus according to the present invention.
FIG. 2 is a block diagram of a basic part of an embodiment of an electric power steering apparatus according to the present invention.
FIG. 3 is a block diagram of the main part of the vehicle behavior determining means according to the present invention.
FIG. 4 is a block diagram of a main part of an embodiment of a correction amount control means according to the present invention.
FIG. 5 is a block diagram of the main part of another embodiment of the correction amount control means according to the present invention.
FIG. 6 is a characteristic diagram of steering torque signal T-target current signal IMS.
FIG. 7 is a characteristic diagram of vehicle speed signal V-vehicle speed coefficient KT.
[Fig. 8] Vehicle speed signal V-vehicle speed coefficient KR characteristic diagram
FIG. 9 is an absolute value | βfr | −understeer correction amount DA characteristic diagram of the angle difference signal βfr.
FIG. 10 is an absolute value of the angle difference signal | βfr | —oversteer correction amount DO characteristic diagram;
FIG. 11 is an angle difference change amount DV-angle difference change coefficient KV characteristic diagram;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering wheel, 9 ... Yaw angular velocity sensor, 10 ... Cutting angle sensor, 11 ... Vehicle speed sensor, 12 ... Steering torque sensor, 13, 27, 28 ... Control means, 16 ... Vehicle reverse detection means , 17, 18 ... Correction amount control means, 21 ... Target current signal setting means, 22 ... Deviation calculation means, 23 ... Drive control means, 24 ... Vehicle behavior means, 25 ... Correction means, 41 ... Inverted sign generation means, 42 ... Multiplication means.

Claims (3)

A steering torque sensor for detecting steering torque of the steering system, an electric motor for adding auxiliary torque to the steering system, vehicle behavior determination means for determining a vehicle behavior based on a slip angle difference between front and rear wheels and outputting a correction amount, at least Target current signal setting means for setting a target current signal based on a steering torque signal from the steering torque sensor, and correction means for correcting the target current signal from the target current signal setting means with a correction amount from the vehicle behavior determination means. An electric power steering apparatus comprising: control means for controlling the drive of the electric motor;
The vehicle is provided with reverse detection means for detecting the reverse of the vehicle, and the control means is provided with a correction amount control means for controlling a correction amount from the vehicle behavior determination means based on a reverse signal from the reverse detection means. Electric power steering device. 2. The correction amount control means for prohibiting output of a correction amount from the vehicle behavior determination means based on a reverse signal when the reverse detection means detects a reverse of the vehicle. Electric power steering device. The correction amount control means reverses the polarity of the yaw angular velocity signal supplied to the vehicle behavior determination means based on a reverse signal when the reverse detection means detects the reverse of the vehicle, and from the vehicle behavior determination means The electric power steering apparatus according to claim 1, wherein the target current signal is corrected with a correction amount.

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