WO2014199020A1

WO2014199020A1 - Electric power steering system

Info

Publication number: WO2014199020A1
Application number: PCT/FR2013/000150
Authority: WO
Inventors: Philippe PUDLO; Stéphane BROUILLAND; Axelle BAILLET; Elisabeth BATAILLIE; André THEVENON; Tomoyasu Kada
Original assignee: Université De Valenciennes Et Du Hainaut-Cambrésis; Fondation Hopale; Centre National De La Recherche Scientifique; Centre Hospitalier Régional Et Universitaire De Lille; Université Lille 2 - Droit Et Santé; Jtekt Corporation; Jtekt Europe
Priority date: 2013-06-12
Filing date: 2013-06-12
Publication date: 2014-12-18

Abstract

The aim of this invention is to provide an electric power steering system that provides appropriate steering assistance based on a force applied to a steering member by a person with a physical disability while he or she is driving a vehicle. In order to address the problem, the invention involves providing a first weight-adding unit (71) that executes a process of adding weight to detected pressure values (PL1 to PL5) in order to calculate a first control pressure value (P1), a second weight-adding unit (71) that executes a process of adding weight to detected pressure values (PR1 to PR5) in order to calculate a second control pressure value (P2), an adding unit (73) that adds the first control pressure value (P1) and the second control pressure value (P2) together in order to calculate a control pressure value (P), and a unit (75) for adjusting the q axis current control value that adjusts a second q axis current control value (Iq2*) based on the control pressure value (P) calculated by the adding unit (73), a vehicle speed (V) detected by a vehicle speed sensor (23) and a steering direction defined by a steering direction defining unit (74).

Description

SPECIFICATION

POWER ASSISTED STEERING SYSTEM [TECHNICAL FIELD]

The invention relates to an electric power steering system.

[PRIOR ART]

There is an electric power steering system that generates a steering assistance force using an electric motor. The conventional electric power steering system adjusts a target current value based on a steering torque detected by a torque sensor, and drives an electric motor so that a motor current passing through an electric motor approaches the target current value.

According to Patent Document 1 below, it is judged whether a driver pushes or pulls a steering wheel on the basis of an axial force on a rotating shaft of a steering wheel, and when the driver pulls the steering wheel , the viscosity coefficient becomes larger than the viscosity coefficient in normal time to provide higher stability. In addition, according to Patent Document 1, it is judged whether the driver maneuvers the steering wheel with one hand or with both hands on the basis of an axial force on the rotating shaft of the steering wheel and a moment around the rotating shaft, the moment being perpendicular to the rotary shaft, and, when the driver operates the steering wheel with one hand, a steering assistance force is increased and the viscosity coefficient is increased. Further, according to Patent Document 2 below, a model of pressure distribution of a driver's foot depression force is recognized and then steering control is performed on the basis of recognition result. For example, when the pressure distribution model indicates that the weight of the driver is placed on the toe of his right foot, a right turn is made. [PATENT DOCUMENT 1]

Japanese Patent Application Publication No. 2008- 296601

[PATENT DOCUMENT 2]

Publication of Japanese Patent Application No. 2005-

205955

[PROBLEMS TO BE SOLVED BY THE INVENTION] When a person with a physical disability has a physical disability in the arm, wrist, or the like, drives a vehicle, it is expected that a force that is greater than necessary is applied to a steering wheel in comparison with the case where a person without a physical disability drives a vehicle. Therefore, when a person with a physical disability drives a vehicle, it is expected that a steering torque detected by a torque sensor does not always coincide with a force applied to the steering wheel by the driver. As a result, the conventional electric power steering system which sets a target current value based on a steering torque detected by a torque sensor may not provide appropriate steering assistance with respect to the force applied to the steering wheel. direction by a person with a physical disability. The object of the invention is to provide an electric power steering system which can provide appropriate steering assistance on the basis of a force applied to a steering member by a person with a physical disability while driving a vehicle. .

[MEANS TO SOLVE THE PROBLEM]

The invention according to claim 1 for realizing the above object relates to an electric power steering system (1) which generates a steering assistance force by using an electric motor (18). The electric power steering system (1) comprises: pressure detecting means (51a-51e, 52a-52e) for detecting pressures applied to a steering member (2) respectively by a plurality of fingers of a conductor; target current value setting means (31, 32, 62) for setting a target current value of the electric motor based on the pressures applied respectively by the plurality of fingers detected by the pressure sensing means; and control means (33 to 41) for executing a drive command on the electric motor based on the target current value set by the target current value setting means. Note that the alphanumeric characters in parentheses indicate corresponding elements, or the like, in an embodiment described below, and it is understood that the scope of the invention is not limited to the embodiment. Hereinafter, it is the same in this section.

The electric power steering system according to the invention comprises the pressure detection means for detecting pressures applied to the steering member. respectively by the many fingers of the driver. The target current value of the electric motor is set based on the pressures applied respectively by the many fingers, detected by the pressure sensing means. Then, a drive command on the electric motor is executed on the basis of the set target current value. Thus, for example, when a person with a physical disability drives a vehicle, appropriate steering assistance, corresponding to the pressures applied by the driver to the steering wheel, is obtained.

The control means may execute a drive command on the electric motor such that a motor current flowing through the electric motor coincides with the target current value set by the target current value setting means.

The invention according to claim 2 relates to the electric power steering system according to claim 1, wherein the target current value adjusting means comprises: weighting means (71,72) for assigning weights to the applied pressures respectively by the plurality of fingers, detected by the pressure sensing means; control pressure value calculating means (71, 72, 73) for calculating a control pressure value on the basis of the pressures applied by the plurality of fingers, respectively, to which weights are allocated by the weighting means; and the target current value adjusting means (75) for setting a target current value of the electric motor based on the control pressure value calculated by the control pressure value calculating means. With the above configuration, appropriate steering assistance can be obtained depending on the problems experienced by persons with physical disabilities. For example, for a person with a physical disability who applies an unnecessarily large force to rotate the steering member, the weight for a portion corresponding to that force may be increased. Thus, one can reduce a load on a finger that can apply unnecessarily large force to the steering member, resulting in a reduction in a load on a person with a physical disability.

The invention according to claim 3 relates to the electric power steering system according to claim 1 or 2, which further comprises steering angle detecting means (24) for detecting a steering angle, wherein the steering means control is configured to execute a drive command to sweat the electric motor when the steering angle detected by the steering angle detecting means changes.

The pressures sensed by the pressure sensing means increase, even in a state where the driver simply maintains the steering member without maneuvering it. In such a state, it is desirable that the steering assistance force not be generated. With this configuration, in a state where the pressures are applied to the steering member although the steering operation is not performed, it is possible to prevent the generation of a steering assistance force.

As in the invention according to claim 4, the pressure sensing means may be provided at a glove worn by the driver. Alternatively, the pressure sensing means may be provided at the steering member. [BRIEF DESCRIPTION OF THE DRAWINGS]

Figure 1 is a schematic view showing the schematic configuration of an electric power steering system according to an embodiment of the invention.

Figure 2 is a schematic view showing the electrical configuration of an Electronic Control Unit (ECU).

The figure. 3 is a block diagram which shows the detailed configuration of a current control value generation unit of the axis q.

The figure. 4 is a graph showing an example of setting a first current control value of the axis q.

Fig. 5 is a graph showing an example of setting the absolute value of a second current control value of the axis q. [MODES FOR CARRYING OUT THE INVENTION]

Hereinafter an embodiment of the invention will be described in detail with reference to the associated drawings.

The figure. 1 is a schematic view showing the schematic configuration of an electric power steering system according to the embodiment of the invention. An electric power steering system 1 comprises a steering wheel 2 which serves as a steering member for steering a vehicle, a steering mechanism 4 which directs steering wheels 3 in accordance with a rotation of the steering wheel 2, and a mechanism 5 steering assistance device for assisting a driver in performing a steering operation. The steering wheel 2 and the steering mechanism 4 are mechanically coupled to each other via a steering shaft 6 and an intermediate shaft 7.

The steering shaft 6 extends linearly. The steering shaft 6 comprises an input shaft 8 coupled to the steering wheel 2 and an output shaft 9 coupled to the intermediate shaft 7. The input shaft 8 and the output shaft 9 are coupled to the drive shaft. to one another via a torsion bar spring 10 so as to be rotatable relative to each other about the same axis. That is, when the steering wheel 2 is rotated, the input shaft 8 and the output shaft 9 rotate in the same direction while rotating relative to each other.

A steering angle sensor 24 and a torque sensor 11 are provided near the steering shaft 6. The steering angle sensor 24 detects a steering angle which is the angle of rotation of the shaft. The torque sensor 11 detects a steering torque applied to the steering wheel 2 based on a relative rotational movement between the input shaft 8 and the output shaft 9. The steering angle detected by the steering angle sensor 24 and the steering torque detected by the torque sensor 11 are introduced into an electronic control unit (ECU) 12. In addition, a vehicle speed detected by a speed sensor 23 is detected. vehicle is introduced into ECU 12. The steering mechanism 4 is formed of a rack mechanism and a pinion mechanism which comprises a pinion shaft 13 and a rack shaft 14 which serves as a steering shaft. Each steering wheel 3 is coupled to a corresponding portion of the end portions of the rack shaft 14 via a tie rod

15 and a control arm (not shown). The pinion shaft 13 is coupled to the intermediate shaft 7. The pinion shaft 13 rotates in accordance with a steering wheel steering operation 2. A pinion 16 is coupled to the distal end (lower end in FIG. 1) of the pinion shaft 13.

The rack shaft 14 extends linearly in a lateral direction (direction perpendicular to the forward direction) of an automobile. A rack 17 is formed in a middle portion of the rack shaft 14 in the axial direction. The rack 17 is engaged with the pinion 16. The pinion 16 and the rack 17 convert the rotation of the pinion shaft 13 into an axial movement of the rack shaft 14. By moving the rack shaft 14 into the rack axial direction, the steering wheels 3 are pointed.

When the steering wheel 2 is turned (turned), the rotation is transmitted to the pinion shaft 13 through the steering shaft 6 and the intermediate shaft 7. Then, the rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 13 by the pinion

16 and the rack 17. Thus, the steering wheels 3 are steered.

The steering assistance mechanism 5 comprises an electric motor 18 and a reduction mechanism 19. The electric motor 18 is used to assist the driver in performing a steering operation. The mechanism of reduction 19 is used to transmit the torque output from the electric motor 18 to the steering mechanism 4. In the present embodiment, the electric motor 18 is formed of a brushless three-phase motor. The reduction mechanism 19 is formed of a worm gear mechanism which comprises a worm shaft 20 and a worm wheel 21 which is engaged with the worm shaft 20. The Reduction mechanism 19 is housed in a gear case 22 which serves as a transmission mechanism casing.

The worm shaft 20 is rotated by the electric motor 18. The worm wheel 21 is coupled to the steering shaft 6 so that it can rotate together with the steering shaft 6 in the same direction. direction. The worm wheel 21 is rotated by the worm shaft 20.

When the worm shaft 20 is rotated by the electric motor 18, the worm wheel 21 is rotated, and then the steering shaft 6 rotates. Then, the rotation of the steering shaft 6 is transmitted to the pinion shaft 13 through the intermediate shaft 7. The rotation of the pinion shaft 13 is converted into an axial movement of the rack shaft 14 Thus, the steering wheels 3 are steered. That is, when the worm shaft 20 is rotated by the electric motor 18, the steering wheels 3 are steered.

The rotation angle of the rotor (rotor rotation angle) of the electric motor 18 is detected by a rotation angle sensor, such as a resolver. The signal delivered at the output of the angle of rotation sensor 25 is introduced into the ECU 12. The electric motor 18 is controlled by the ECU 12 which serves as an engine control unit.

In the present embodiment, to provide appropriate steering assistance when a person with a physical disability, or the like, has a physical disability in the arm, wrist, or the like, drives a vehicle, applied pressure at the steering wheel 2 respectively by the driver's fingers are detected, and the electric motor 18 is controlled on the basis of the detected pressures. In order to execute such an engine control, the electric power steering system 1 comprises a glove

51 for left hand with pressure sensors and a glove 52 for right hand with pressure sensors (hereinafter collectively referred to as "sensor gloves 51 and

52 "where applicable).

The glove 51 for left hand has five pressure sensors 51a to 51e which are used to detect pressures applied to the steering wheel 2 respectively by the fingers of the left hand of the driver. The five pressure sensors 51a, 51b, 51c, 51d and 51e correspond respectively to the thumb, the index finger, the middle finger, the ring finger and the little finger of the left hand. Hereinafter, the pressure sensors 51a to 51e corresponding to the respective fingers of the left hand will be collectively referred to as "left hand pressure sensors 51" as appropriate. Similarly, the glove 52 for right hand has five pressure sensors 52a to 52e which are used to detect pressures applied to the steering wheel 2 respectively by the fingers of the right hand of the driver. The five pressure sensors 52a, 52b, 52c, 52d and 52e respectively correspond to the thumb, index finger, middle finger, ring finger and little finger of the right hand. Hereinafter, the pressure sensors 52a to 52e corresponding to the respective fingers of the right hand will be collectively referred to as "right hand pressure sensors 52" as appropriate.

The control mode in which the electric motor 18 is controlled by the ECU 12 includes a "normal control mode" and a "control mode for a person with a physical disability". The "normal control mode" is a control mode in which the electric motor 18 is controlled so that the electric motor 18 generates a steering assistance force corresponding to the steering torque T detected by the torque sensor 11. On the other hand, the "control mode for a person with a physical disability" is a control mode in which the electric motor 18 is controlled so that the latter generates a steering assistance force corresponding to the pressures detected by the sensors. 51 pressure sensors for left hand and 52 pressure sensors for right hand. A mode change switch 26 is provided near a driver's seat of the vehicle. The mode change switch 26 is used to change the control mode between the normal control mode and the control mode for a person with a physical disability. The mode change switch 26 is connected to the ECU 12.

The driver is allowed to select a desired control mode from the "normal control mode" and the "physically handicapped control mode" by operating the mode change switch 26. When the driver selects the "control mode for person with a physical disability", the driver wears the sensor gloves 51 and 52 on respective hands to perform a steering operation. In this case, the pressure sensors 51a to 51e supplied to the sensor level 51 and the pressure sensors 52a to 52e provided at the sensor glove level 52 are connected to the ECU 12 using exclusive connecting cables (not shown).

The figure. 2 is a schematic view showing the electrical configuration of the ECU 12.

When the normal control mode is selected by the change switch 26, the ECU 12 drives the electric motor 18 based on the output signal from the rotation angle sensor 25, the steering torque T detected by the sensor. 11 and the vehicle speed V detected by the vehicle speed sensor 23 to provide appropriate steering assistance on the basis of a steering state.

On the other hand, when the control mode for a person with a physical disability is selected by the change switch 26, the ECU 12 drives the electric motor 18 based on the signal outputted by the rotation angle sensor 25. , the pressures detected by the left hand pressure sensors 51 and the right hand pressure sensors 52, the vehicle speed V detected by the vehicle speed sensor 24 and the steering angle θs detected by the sensor 24d. steering angle to provide appropriate steering assistance on the basis of a steering state. The ECU 12 comprises a microcomputer 27, a drive circuit (inverter circuit) 28 and a current detection unit 29. The driving circuit 28 is controlled by the microcomputer 27, and supplies electrical power to the electric motor 18, the current detection unit 29 detects currents which pass through stator coils of the respective phases of the electric motor 18.

The current detection unit 29 detects phase currents I ₀ , I _v and I _w (hereinafter collectively referred to as "detected three-phase currents I ₀ , I _v and I _w " as appropriate) passing through the stator coils of the respective phases of the electric motor 18. These are current values in respective directions of the coordinate axis in a UVW coordinate system.

The microcomputer 27 includes a CPU and memories (ROM, RAM, and the like), and executes predetermined programs to function as a plurality of functional processing units. The plurality of functional processing units comprise a current control value generating unit 31 of an axis of a current control value generation unit 32 of an axis q, a deflection calculation unit 33 current of the axis of a q axis current deflection calculation unit 34, a control unit of the IP type (proportional integral) of the axis d, an IP control unit 36 ( proportional integral) of the axis q, a control voltage generation unit 37 of the axis d, a control voltage generation unit 38 of the axis q, a first coordinate conversion unit 39, a unit PWM control unit 40, a rotation angle calculation unit 41 and a second coordinate conversion unit 42.

The d-axis current control value generation unit 31 generates a control value la of a current component of the axis d along a magnetic pole direction of the electric motor rotor. Overall, the control value I _d * of the current of the axis d is "0". The unit 32 of value generation of current control of an axis q generates a control value I _q * of a current component of the axis q (where a coordinate plane dq is a plane along the direction of rotation of the rotor of the electric motor 18 ). The axis q is perpendicular to the axis d. The control value la * of the current component of the axis d and the control value Iq * of the current component of the axis q can be collectively referred to as "two-phase control currents I _d * and I _q * Where appropriate. Two-phase control currents I _d * and I _q * are current target values. The detailed operation of the current control value generation unit 32 of the axis q will be described later. The rotation angle calculating unit 41 calculates the rotation angle of the rotor (rotation angle of the rotor) 9a of the electric motor 18 on the basis of the signal output from the angle of rotation sensor 25. The detected three-phase currents lu, Iv, and I _w that are detected by the current detection unit 29 are transmitted to the second coordinate conversion unit 42. The second coordinate conversion unit 42 uses the rotation angle θa of the rotor calculated by the rotation angle calculation unit 41 to convert the detected three-phase currents I ₀ , I _v , and I _w to a current Id of the axis d and a current I _q of the axis q (hereinafter collectively referred to as "two-phase currents detected I _d and I _q " if appropriate) on a coordinate dq.

The current deviation calculation unit 33 of the axis d calculates a deviation of the current I _d of the axis d from the current control value I _d * of the axis d. The current deflection calculated by the current deviation calculating unit 33 of the d-axis is transmitted to the IP-type control unit of the d-axis and is subject to IP type operation. The unit 37 voltage generating control the d-axis generates a voltage V * _to control the d-axis based on the calculated result by the unit 35 IP-based control of the d axis.

The current deviation calculating unit 34 of the axis q calculates a deviation of the current I _q from the axis q from the value I _q * of current control of the axis q. The current deflection calculated by the current deviation calculating unit 34 of the q axis is transmitted to the IP type control unit 36 of the q axis, and is subjected to an IP type operation. The control voltage generation unit 38 of the axis q generates a control voltage V _q * of the axis q on the basis of the result calculated by the control unit 36 of type IP of the axis q.

The control voltage V _d * of the axis d and the control voltage V _q * of the axis q are transmitted to the first coordinate conversion unit 39. The first coordinate conversion unit 39 uses the rotation angle Qa of the rotor calculated by the rotation angle calculation unit 41 to convert the control voltage V _d * of the axis d and the voltage V _q *. for controlling the q axis at control voltages on the UVW coordinate system, ie, V _u * _f V _v * and V _w * control voltages for phase U, phase V and phase W ( hereinafter collectively referred to as "three-phase control voltages V _u *, V _v * and V _w *" if applicable).

The PWM control unit 40 generates a U phase PWM control signal, a V phase PWM control signal and a W phase PWM control signal having cyclic ratios respectively corresponding to the phase control voltage V _u *. U, the phase control voltage V _v * and the phase control voltage V _w *, and feeds the generated PWM control signals to the driver 28. The driving circuit 28 is formed of a three-phase inverter circuit corresponding to the phase U, the phase V and the phase W. Power elements that constitute the inverter circuit are controlled by the PWM control signals transmitted from the unit. PWM control unit 40 for applying voltages corresponding to the three-phase control voltages V _u *, V _v * and V _w * to the stator coils of the respective phases of the electric motor 18.

The current deflection calculating units 33 and 34 and the IP control units 35 and 36 constitute a current feedback control means. Due to the function of the current feedback control means, a motor current flowing through the electric motor 18 is controlled to bring the two-phase control currents I _d ^* and I _q ^* respectively set by the units 31 and 32 of current control value generation.

Fig. 3 is a block diagram showing the detailed configuration of the current control value generating unit 32 of the q axis. The current control value generation unit 32 of the axis q comprises a first current control value generation unit 61 of the axis q, a second current control value generation unit 62 of the q axis and a second selection unit 63. The first q axis current command value generation unit 61 generates a current control value of the q axis for the normal control mode. The current control value generation unit 62 of the q axis generates a current control value of the axis q for the control mode for a person with a physical disability. The first q-axis current control value generation unit 61 generates a first q-axis current control value I _q i * on the basis of the steering torque detected by the torque sensor 11 (torque direction T detected) and the speed V of the vehicle detected by the vehicle speed sensor 23. An example of setting the first current control value I _q i * of the axis q with respect to the detected direction torque T is shown in the figure. 4. With regard to the detected steering torque T, for example, a torque for a right-hand turn takes a positive value, and a torque for a left-turn takes a negative value. In addition, the first q-axis current control value I _q1 * adopts a positive value when the right-turn steering assistance force should be generated by the electric motor 18, and adopts a negative value. when the steering assist force for a left turn should be generated by the electric motor 18.

The first current control value I _q i * of the axis q adopts a positive value with respect to a positive value of the detected direction torque T, and adopts a negative value with respect to a negative value of the detected steering torque T. . When the detected steering torque T is close to zero, the first current control value _q1 * of the axis q is set to zero. Then, as the absolute value of the detected steering torque T increases, the absolute value of the first current control value Iqi * of the axis q is set to a larger value. Thus, as the absolute value of the detected steering torque T increases, the steering assistance force is increased. Further, as the speed V of the vehicle detected by the vehicle speed sensor 23 increases, the absolute value of the first current control value I _q1 * of the axis q is set to a smaller value. Thus, a large steering assistance force is generated when the vehicle is traveling at a low speed, and the steering assistance force is reduced when the vehicle is traveling at a high speed.

The first q-axis current control value generation unit 61 uses, for example, a card which stores the correlation between the steering torque T and the first current control value I _q1 * of the axis q. , shown in the figure. 4, for each vehicle speed to generate the first current control value I _q1 * of the axis q corresponding to the steering torque T and the speed V of the vehicle. The first current control value _q of the q-axis generated by the first q-axis current control value generating unit 61 is input to the second selection unit 63.

The second q-axis current control value generating unit 62 includes a first weight adding unit 71, a second weight adding unit 72, an adding unit 73, a determining unit 74 steering steering unit, a q-axis current control value setting unit 75, a steering angle change monitoring unit 76 and a first selection unit 77. In the present embodiment, the steering angle sensor 24 is configured to detect the amount of rotation (rotation angle) of the steering wheel 2 in each of the forward directions and reverse from a neutral position (reference position) of the steering wheel 2, outputs an amount of clockwise rotation from the neutral position as a positive value, and outputting a quantity of counter-clockwise rotation from the neutral position as a negative value.

The steering direction determining unit 74 determines the steering direction on the basis of the steering angle Os detected by the steering angle sensor 24. In particular, the steering direction determining unit 74 determines that a rightward deflection is effected when the steering angle Os detected by the steering angle sensor 24 is a positive value, and determines that a steering to the left is performed when the detected steering angle Os is a negative value. The steering direction determined by the steering direction determining unit 74 is transmitted to the current control value setting unit 75 of the axis q.

Note that the steering direction determining unit 74 determines the steering direction as follows. That is, the steering direction determining unit 74 acquires the steering angle θs detected by the steering angle sensor 24 at predetermined calculation cycles. Next, it is determined whether a rightward or leftward deflection is made based on the previously acquired Os steering angle and the currently acquired steering angle Os.

The steering angle change monitoring unit 76 determines whether the steering angle changes on the basis of the steering angle Os detected by the steering angle sensor 24. Specifically, the steering angle change monitoring unit 76 acquires the steering angle Os detected by the steering angle sensor 24 at predetermined calculation cycles. Then, it is determined that the steering angle changes when the absolute value of the deviation between the steering angle Os previously acquired and the steering angle 6s currently acquired is greater than a predetermined threshold, and it is determined that the steering angle remains unchanged when the absolute value of the deviation is less than or equal to the threshold. The result determined by the steering angle change monitoring unit 76 is transmitted to the first selection unit 77.

The first weight adding unit 71 submits detected PLI to PL5 pressure values which are respectively detected by the pressure sensors 51a to 51e provided at the left hand glove 51 to weight adding processes to thereby calculate a first value PLI of control pressure. More specifically, the first weight adding unit 71 multiplies the pressure values PL1 to PL5 detected by weighting coefficients KL1 to KL5 correspondingly preset, respectively. Then, the multiplied results are added together to calculate the first control pressure value PI.

The first control pressure PI value is expressed by Equation 1 indicated below, where the detected PLI to PL5 pressure values are indicated by PLn (n = 1, 2, 5) and the weighting coefficients.

KL1 to KL5 are indicated by PLn (n = 1, 2, ..., 5).

5

Equation 1 ^{p 1} = Σ PLn · KLn

n = 1

The weighting coefficients KL1 to KL5 are, for example, adjusted so that the total sum ΣKLn becomes equal to 1. The weighting coefficients KL1 to KL5 are set as follows. For example, a temporal change in the pressure of each finger when a person with a physical disability who is driving the vehicle performs a steering operation and a change temporal pressure of each finger when a person without physical disability performs a steering operation are measured in advance. By comparing the two measured results to one another, the finger with which the person with a physical disability unnecessarily applies a large force (force that is greater than a force required for a steering operation) to the steering wheel 2 during the steering operation is identified. Then, for the finger with which a large unnecessarily larger force is applied to the steering wheel 2 during the steering operation, the corresponding weighting coefficient is set to a larger value. The reason will be described below. When a person with a physical disability drives a vehicle, an unnecessarily large force (force that is greater than a force required for a steering operation) may be applied to the steering wheel 2. The finger with which an unnecessarily large force is applied steering wheel 2 is considered to be different depending on the problems faced by people with physical disabilities. Then, by increasing the weighting coefficient corresponding to the finger with which an unnecessarily large force is applied to the steering wheel 2, the steering assistance force can be increased as an unnecessarily large force is applied to the steering wheel 2. Thus, it is possible to reduce a load on the finger that can apply an unnecessarily large force to the steering wheel 2.

In addition, for example, a temporal change in the pressure of each finger at the moment when the driver performs a steering operation can be measured in advance, and the weighting coefficient for the finger whose time pressure change is closer a change of the steering torque can be set to a larger value. Thus, it is possible to obtain a steering assistance force which corresponds to the pressures applied by the person with a physical handicap at the steering wheel 2 and who is also close to a steering assistance force corresponding to the steering torque. . In addition, the driver may be allowed to adjust or modify the weighting coefficients KL1 to KL5.

The second weight adding unit 72 subjects the detected pressure values PR1 to PR5 which are respectively detected by the pressure sensors 52a to 52e provided at the right hand glove 52 to a weight adding process to thereby calculate a second value P2 of control pressure. More specifically, the second weight adding unit 72 multiplies the pressure values PR1 to PR5 detected by weighting coefficients KR1 to KR5 corresponding preset, respectively. Then, these multiplied results are added together to calculate the second control pressure value P2.

The second control pressure value P2 is expressed by Equation 2 indicated below, where the pressure values PR1 to PR5 detected are denoted by PRn (n = 1, 2, 5) and the weighting coefficients.

KR1 to KR5 are designated KRn (n = 1, 2, 5).

5

Equation 2 F 2 = Σ FRn · KRn

n = 1

The weighting coefficients KR1 to KR5 are, for example, set such that the total sum ΣKRn becomes equal to 1. The weighting coefficients KR1 to KR5 are set by a method similar _to that for the weighting coefficients to KL1 KL5 described above. The adding unit 73 adds the first control pressure PI value and the second control pressure value P2 together to calculate a control pressure final value P (= PI + P2).

The current control value setting unit 75 of the q axis sets the second current axis current control value I _Q 2 * on the basis of the control pressure value P calculated by the unit. of addition 73, the vehicle speed V detected by the vehicle speed sensor 23 and the steering direction determined by the steering direction determining unit 74.

More specifically, the current control value setting unit 75 of the axis q initially generates the absolute value | I _Q 2 * I of the second current control value of the axis q based on the control pressure value P calculated by the adding unit 73 and the vehicle speed V detected by the sensor 23 vehicle speed.

An example of setting the absolute value | I _Q 2 * I of the second current control value of the axis q with respect to the control pressure value P is shown in the figure. 5. When the control pressure value P is a value close to zero, the absolute value II _q2 * I of the second current control value of the axis q is set to zero. Thus, as the control pressure value P increases, the absolute value | I _q2 * I of the second current control value of the q axis increases. Thus, as the control pressure value P increases, a greater steering assist force is generated. In addition, as the speed V of the vehicle detected by the vehicle speed sensor 23 increases, the absolute value I I _O I * I of the second current control value of the q axis is set to a smaller value.

The current control value setting unit 75 of the axis q uses, for example, a card which stores the correlation between the control pressure value P and the absolute value | I _q 2 * I of the second current control value of the axis q, shown in the figure. 5, for each vehicle speed to thereby generate the absolute value | I _q 2 * I of the second current control value of the axis q, corresponding to the control pressure value P and the speed V of the vehicle.

Subsequently, the current control value setting unit 75 of the q axis determines the sign of the second current control value of the q-axis based on the steering direction determined by the unit. 74 for steering direction determination. Specifically, when the steering direction determining unit 74 determines that a rightward steering is performed, the sign of the second current control value of the q axis is set to be positive; while, when the steering direction determining unit 74 determines that left turning is performed, the sign of the second current control value of the q axis is set to be negative. Thus, the absolute value and the sign of the second current control value of the axis q are set, so that the second current control value I _q2 * of the axis q is set.

The second q axis current control value I _q2 * set by the q axis current control value setting unit 75 and the control value "0" are input into the first selection unit. 77. When the change monitoring unit 76 turning angle determines that the steering angle changes, the first selection unit 77 selects the second current control value I _q2 * of the axis q as the second final value I _q 2 * of current control of the axis q and outputs the second final value I _q 2 * current control of the axis q.

On the other hand, when the steering angle change monitoring unit 76 determines that the steering angle does not change, the first selection unit 77 selects the control value "0" as the second final value. I _q 2 * current control of the axis q and outputs the second final value I _q 2 * current control of the axis q. This is because the pressures detected by the pressure sensors 51a-51e and 52a-52e increase, even in a state where the driver simply holds the steering wheel 2 without maneuvering it and, therefore, a power-assist force generation. steering is prevented in such a state.

The second final value I _q2 * of current control of the axis q output from the first selection unit 77 is set as the second current control value I _q2 * of the axis q generated by the second unit 62 of current control value generation of the axis q. The second q axis current control value I _q2 * is input to the second selection unit 63. The mode change signal from the mode change switch 26 is input to the second selection unit 63 as than control signal. When the normal control mode is set by the mode change switch 26, the second selection unit 63 selects the first current control value I _q1 * of the axis q generated by the first current control value generation unit 61 of the axis q as the final value I _q * of the current control of the axis q and outputs the final value Iq * of the current control of the axis q . On the other hand, when the control mode for a person with a physical disability is set by the mode change switch 26, the second selection unit 63 selects the second current control value I _q 2 * of the axis q generated by the second current control value generation unit 62 of the axis q as the final value I _q * of the current control of the axis q and outputs the final value I _q * of current control of the q axis. When a driver, such as a person with a physical disability, actuates the mode change switch 26 to select the control mode for a person with a physical disability, the second axis current control value I _q2 * q generated by the second current control value generation unit 62 of the axis q is set as the current control value _{q q} * of the axis q.

According to the embodiment above, when a person with a physical disability, or the like, drives a vehicle, the appropriate steering assistance corresponding to the pressures applied by the driver to the steering wheel is obtained. In addition, the current control value of the axis q is set based on the control pressure value obtained by subjecting the pressures applied respectively by the driver's fingers to the weight adding process. As a result, appropriate turnaround assistance can be obtained based on the problems faced by people with physical disabilities. Thus, for example, one can reduce a load on the finger that can unnecessarily apply a great force to the steering wheel 2. The embodiment of the invention is described above; however, the invention may be implemented in other embodiments. For example, in the embodiment described above, the steering direction is determined by the steering direction determining unit 74 which determines the steering direction on the basis of the steering angle Qs; however, instead of the steering direction determining unit 74, a steering direction determining unit 74A which determines the steering direction on the basis of the steering torque T can be provided as indicated by the broken line in the steering direction determination unit. Fig. 3. The steering direction determining unit 74A determines that a rightward deflection is effected when the steering torque T detected by the torque sensor 11 is a positive value, and determines that a steering to the left is performed when the steering torque .T is a negative value. The steering direction determined by the steering direction determining unit 74A is transmitted to the q axis current control value setting unit 75, and is used to determine the sign of the second control value. In addition, instead of the steering angle change monitoring unit 76, a steering torque change monitoring unit 76A may be provided as indicated by the dashed line in FIG. Fig. 3. The steering torque change monitoring unit 76A determines whether the steering torque changes on the basis of the steering torque T detected by the torque sensor 11. In particular, the torque change monitoring unit 76A. direction acquires the steering torque T detected by the torque sensor 11 at predetermined calculation cycles. Thus, it is determined that the steering torque changes when the absolute value of the deviation between the previously acquired steering torque T and the currently acquired steering torque T is greater than a predetermined threshold, and it is determined that the steering torque remains unchanged when the absolute value of the deviation is less than or equal to threshold.

In this case, when the steering torque change monitoring unit 76A determines that the steering torque changes, the first selection unit 77 selects the second current control value I _q2 * of the axis q as second current control end value _{q1 q2} * of the axis q and outputs the second final value I _q2 * current control of the axis q. On the other hand, when the steering torque change monitoring unit 76A determines that the steering torque remains unchanged, the first selection unit 77 selects the control value "0" as the second final value I _q2 * control ^'current of the q-axis and outputs the second final value IQ2 current control * of the q axis.

In addition, in the above embodiment, the pressure sensors 51a to 51e are provided at the glove 51 and the pressure sensors 52a to 52e are provided at the glove 52; instead, the pressure sensors 51a-51e and 52a-52e can be provided at the steering wheel 2.

Various design changes, other than those mentioned above, may be made within the scope of the claims.

[DESCRIPTION OF DIGITAL REFERENCES]

1: POWER ASSISTED STEERING SYSTEM 2: STEERING WHEEL

5: MECHANISM OF ASSISTANCE TO BRAQUAGE

11: TORQUE SENSOR

12: ECU

18: ELCTRIC MOTOR

24: STRAIGHT ANGLE SENSOR

25: ROTATION ANGLE SENSOR

27: MICROCOMPUTER

31: CURRENT AXIS CURRENT CONTROL VALUE GENERATION UNIT

32: AXIS CURRENT CONTROL VALUE GENERATION UNIT q

51 to 51e, 52a to 52e: PRESSURE SENSOR

62: SECOND GENERATION UNIT OF AXIS CURRENT CONTROL VALUE q

Claims

An electric power steering system that generates a steering assistance force using an electric motor, comprising:

pressure detection means for detecting pressures applied to a steering member respectively by a plurality of fingers of a conductor;

target current value setting means for setting a target current value of the electric motor based on the pressures applied respectively by the plurality of fingers detected by the pressure sensing means; and

control means for executing a drive command on the electric motor based on the target current value set by the target current value setting means.

An electric power steering system according to claim 1, wherein

the target current value setting means comprises:

weighting means for assigning weights to the pressures applied respectively by the many fingers, detected by the pressure sensing means;

control pressure value calculating means for calculating a control pressure value on the basis of the pressures applied respectively by the many fingers, to which weights are allocated by the weighting means; and

target current value setting means for setting a target current value of the electric motor based on the control pressure value calculated by the control pressure value calculating means.

An electric power steering system according to claim 1 or 2, further comprising:

steering angle detection means for detecting a steering angle, where

the control means is configured to execute a drive command on the electric motor when the steering angle detected by the steering angle detecting means changes.

An electric power steering system according to any one of claims 1 to 3, wherein the pressure sensing means is provided at a glove which is carried by the driver.