JP4200949B2 - Electric power steering apparatus and control constant determination method and apparatus thereof - Google Patents

Description

  The present invention relates to an electric power steering device for a vehicle, and more particularly to an electric power steering device and a control constant determining method and device for the electric power steering device.

  As one of electric power steering devices for vehicles such as automobiles, a steering assist force is calculated based on at least a steering torque as described in, for example, the following Patent Document 1 filed by the applicant of the present application. There is already known an electric power steering device that detects a vibration of the motor and adds a vibration force having a phase opposite to that of the detected vibration to a steering assist force as a damping force.

According to such an electric power steering device, the damping force in the opposite phase to the vibration of the steering shaft is added to the steering assist force. Therefore, compared with the case where the damping force is not added to the steering assist force, flutter and braking are not performed. It is possible to reduce the transmission of high-frequency vibration caused by wheel vibration from the steering wheel side to the steering wheel as the steering input means through the electric power steering device.
JP-A-6-171541

  However, in the conventional electric power steering apparatus as described above, a sensor for detecting the vibration of the steering shaft is indispensable. Therefore, it is inevitable that the electric power steering apparatus is expensive, and the control response is delayed. In some cases, the vibration of the steering wheel cannot always be effectively reduced.

  The present invention has been made in view of the above-described problems in the conventional electric power steering apparatus configured such that a damping force having a phase opposite to that of the vibration of the steering shaft is added to the steering assist force. The main object of the invention is to optimize the control constant when calculating the steering assist force based on at least the steering torque, so that the vibration input to the electric power steering device from the steering wheel side is included in the steering torque. By generating a reverse phase force, vibration transmitted from the steering wheel side to the steering input means such as the steering shaft via the electric power steering device without reducing the vibration of the steering shaft is reduced.

  According to the present invention, the main problem described above is input from the steering wheel side for an electric power steering device that detects steering torque and generates steering assist force based on at least the steering torque and a predetermined control constant. The control constant determining method for the electric power steering apparatus is used to determine the predetermined control constant so as to suppress the vibration from being transmitted to the steering input means via the electric power steering apparatus. The electric power steering device is vibrated, a steering assist force is calculated based on the steering torque and a predetermined control constant, and the phase of the exciting force of the vibrating means and the phase of the steering assist force are reversed. The predetermined control constant is changed until the control constant determining method for the electric power steering apparatus (configuration of claim 1) or steering For an electric power steering device that detects a torque and generates a steering assist force based on at least a steering torque and a predetermined control constant, vibration input from the steering wheel side passes through the electric power steering device to the steering input means. A control constant determining device for an electric power steering apparatus that determines a predetermined control constant so as to suppress transmission, an excitation means for exciting the electric power steering apparatus from the steering wheel side, and the excitation Means for detecting the excitation force of the means, means for analyzing the phase of the excitation force and the steering assist force, and predetermined control until the phase of the excitation force and the phase of the steering assist force are in reverse phase A control constant determination device for an electric power steering device (configuration of claim 3), or a steering torque detection device. In the electric power steering apparatus that generates the steering assist force based on at least the steering torque and the predetermined control constant, the predetermined control constant is the control constant determination method according to claim 1 or 2. Alternatively, it is achieved by an electric power steering device (structure of claim 5) characterized in that it is a control constant determined by the control constant determining device described in 4.

  Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1 or 3, the predetermined control constant defines at least a phase of the steering assist force with respect to the steering torque. It is comprised so that it may be a control constant (structure of Claim 2 or 4).

  According to the configuration of the first aspect, the electric power steering device is vibrated from the steering wheel side by the vibration means, the steering assist force is calculated based on the steering torque and the predetermined control constant, and the vibration means is applied. The predetermined control constant is changed until the phase of the vibration force and the phase of the steering assist force are reversed. Therefore, the phase of the vibration force and the phase of the steering assist force input from the steering wheel side to the electric power steering device. It is possible to easily, accurately, and reliably obtain a predetermined control constant that reverses the phase.

  According to the second and fourth aspects of the present invention, since the predetermined control constant is a control constant that defines at least the phase of the steering assist force with respect to the steering torque, vibration input to the electric power steering apparatus from the steering wheel side. A predetermined control constant that reverses the phase of the force and the phase of the steering assist force can be obtained easily, accurately, and reliably.

  According to the third aspect of the present invention, the control constant determination device includes a means for detecting the excitation force of the excitation means, a means for analyzing the steering assist force and the phase of the excitation force, the steering assist force and the excitation force. Means for comparing the phase of the force and changing the predetermined control constant until the phases of the steering assist force and the excitation force are in reverse phase, so that the control constant determining method of claim 1 can be easily and reliably performed. Can be executed.

  According to the fifth aspect of the present invention, the electric power steering device applies the steering assist force according to at least the steering torque and the predetermined control constant, and the predetermined control constant is the control constant according to claim 1 or 2. Since the control constant is determined by the determination method or the control constant determination device according to claim 3 or 4, high-frequency vibration caused by wheel vibration during flutter or braking is steered from the steering wheel side via an electric power steering device. Transmission to a steering input means such as a wheel can be reliably and effectively reduced, and it is not necessary to detect vibrations of components of an electric power steering device such as a steering shaft. Compared with other electric power steering devices, the structure of the electric power steering device can be simplified and the cost can be reduced. Kill.

[Preferred embodiment of problem solving means]
According to one preferred aspect of the present invention, in the configuration of the above first to fourth aspects, at a frequency within the range of the frequency of vibration input to the electric power steering device from the steering wheel side when the vehicle is traveling. An electric power steering device is configured to vibrate from the steering wheel side (preferred aspect 1).

  According to another preferred aspect of the present invention, in the configuration of the first to fourth aspects, the magnitude of the difference between the excitation force and the vibration force transmitted to the steering input means is a predetermined value. The predetermined control constant is changed until the product is equal to or larger than the product of the reference coefficient (preferred aspect 2).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 2, the predetermined reference coefficient is configured to be a value greater than 0.5 and 1 or less (preferred embodiment 3).

  According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 3, the predetermined reference coefficient is configured to be 0.8 (preferred embodiment 4).

  According to another preferred aspect of the present invention, in the configuration of the above first to fourth aspects, the steering torque Tsp after phase compensation is calculated according to the following equation 1 where s is a Laplace operator and T is a time constant. The target steering assist torque Tat is calculated based on the calculated steering torque Tsp after phase compensation, and the steering assist force Fat is generated based on the target steering assist torque Tat (preferred aspect 5).

  According to another preferred aspect of the present invention, in the configuration of claim 2 or 4, the predetermined control constant is configured to be a control constant that defines the phase and gain of the steering assist force with respect to the steering torque. (Preferred embodiment 6)

  The present invention will now be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram showing an electric power steering apparatus and a control constant determining apparatus to which one embodiment of a control constant determining method according to the present invention is applied.

  In FIG. 1, reference numeral 10 denotes a rack-and-pinion type electric power steering apparatus that is driven in response to turning of the steering wheel 11 by the driver. In the illustrated embodiment, the electric power steering apparatus 10 is a rack coaxial type electric power steering apparatus, and converts the electric motor 12 and the rotational torque of the electric motor 12 into a force in the reciprocating direction of the rack bar 14. For example, it has a ball screw type conversion mechanism 16 and generates a steering assist force that drives the rack bar 14 relative to the housing 18, thereby reducing the driver's steering burden.

  The electric motor 12 of the electric power steering device 10 is controlled by the electronic control device 20. A signal indicating the steering torque Ts is input to the electronic control device 20 from a torque sensor 24 provided on the steering shaft 22, and a signal indicating a control constant A is input from the control constant determining device 26 as described later. The electronic control unit 20 stores the flowchart shown in FIG. 2, calculates the target steering assist torque Tat based on the steering torque Ts and the control constant A, as will be described in detail later, and the steering assist torque is the target steering assist. The electric motor 12 is controlled so as to have the torque Tat, and the target steering assist torque Tat is converted into the target assist force Fat at the rack bar 14.

  The control constant determination device 26 is detachably connected to one end of the rack bar 14, and detects the axial force Fo applied to the rack bar 14 by the vibration of the vibration unit 28. A force sensor 30, a frequency / phase analysis device 32, and an electronic control device 34 are included. As shown in the figure, a signal indicating the target assist force Fat is input from the electronic control unit 20 to the frequency / phase analysis device 32, and a signal indicating the axial force Fo is input from the force sensor 30. Analyzes the frequency and phase of the target assist force Fat and the axial force Fo, and outputs a signal indicating the analysis result to the electronic control unit.

  The electronic control unit 34 stores the flowchart of the control constant determination control shown in FIG. 4, and determines whether or not the phases of the target assist force Fat and the axial force Fo are opposite to each other as will be described in detail later. When the phases of the target assist force Fat and the axial force Fo are not reversed, the control constant A is sequentially changed according to a predetermined procedure. When the phases of the target assist force Fat and the axial force Fo are opposite, the control constant A is changed. The control constant is determined and output to the electronic control unit 20. When receiving the control constant for control from the electronic control unit 34, the electronic control unit 20 stores the control constant in a predetermined storage area.

  Although not shown in detail in the figure, the electronic control devices 20 and 34 have, for example, a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Includes component microcomputer.

  In particular, the electronic control unit 20 calculates the steering torque Tsp after phase compensation in accordance with the above equation 1 using s as a Laplace operator and T as a time constant, and is shown in FIG. 3 based on the steering torque Tsp after phase compensation. A target steering assist torque Tat is calculated from a map corresponding to the graph.

  Further, since the target assist force Fat is applied to the rack bar 14, as shown in FIG. 12, if the phase difference between the target assist force Fat and the axial force Fo is θ [rad], the rack bar 14 will cause the steering shaft 22 to rotate. The force F transmitted to the side is expressed by the following formula 2, and the vibration force reduction amount ΔF by the control of the target steering assist torque Tat is expressed by the following formula 3.

The larger the magnitude of the vibration force reduction amount ΔF is, the higher the vibration force reduction effect by the control of the target steering assist torque Tat is. The closer the phase difference θ is to π, the higher the vibration force reduction effect by the control of the target steering assist torque Tat. Therefore, the electronic control unit 34 sets the phase of the target assist force Fat and the axial force Fo when Kc is a positive constant coefficient of 0.5 or more and 1 or less, for example, 0.8, and the following inequality is satisfied. Determined to be in reverse phase.
| ΔF | ≧ Kc | Fat | (4)

  Further, if the frequency range of vibrations input to the rack bar 14 of the electric power steering device 10 from the steering wheel side due to flutter or wheel vibration during braking while the vehicle is running is assumed to be f1 to f2, the exciter 28 vibrates the rack bar 14 in the frequency range of f1 to f2.

  The determination of the control constant A by the control constant determination device 26 configured as described above is executed for each vehicle or each vehicle type for the vehicle before shipment. When the control constant A is determined by the control constant determining device 26, the output shaft 28A of the vibration exciter 28 is connected to one end of the rack bar 14 of the electric power steering device 10 by a ball joint for connecting a tie rod, and the electronic control device. 20 and 34 are communicably connected to each other, and then a switch (not shown) of the electronic control units 20 and 34 is turned on.

  Next, the steering assist torque control for determining the control constant in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing a switch (not shown), and is repeatedly executed at predetermined time intervals until the switch is opened.

  First, in step 10, a signal indicating the control constant A input from the electronic control unit 34 is read, and in step 20, a signal indicating the steering torque Ts detected by the torque sensor 24 is read. In step 30, the steering torque Tsp after phase compensation is calculated according to the above equation (1).

  In step 40, the vehicle speed V is set to 0, and the target assist torque Tat is calculated from the map corresponding to the graph shown in FIG. 3 based on the steering torque Tsp after phase compensation. In step 50, the target assist torque Tat is calculated. Based on this, the target assist force Fat at the rack bar 14 is calculated, and a signal indicating the target assist force Fat is output to the control constant determining device 26.

  In step 60, the target control current for the electric motor 12 is calculated based on the target assist torque Tat, and the control current for the electric motor 12 is controlled to become the target control current, whereby the steering assist torque is changed to the target steering assist torque Tat. The electric motor 12 is controlled so that it becomes.

  Next, the control constant determination control routine in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 4 is also started by closing a switch not shown in the figure, and is repeatedly executed at predetermined time intervals until the switch is opened.

  First, at step 110, the control constant A is set to a preset initial value Ao, and a signal indicating the control constant A is output to the electronic control unit 20, and at step 120, the vibrator 28 is set. In response to this, a vibration start command signal is output, whereby the vibration of the rack bar 14 by the vibration generator 28 is started.

  In step 130, a signal indicating the axial force Fo of the rack bar 14 is input from the force sensor 30 to the control constant determination device 26. In step 140, the phase analysis of the axial force Fo is performed to the frequency / phase analyzer 32. A signal indicating the frequency and phase of the axial force Fo is input to the electronic control unit 34.

  In step 150, a signal indicating the target assist force Fat is input from the electronic control unit 20 to the frequency / phase analyzer 32. In step 160, the phase analysis of the target assist force Fat is performed to the frequency / phase analyzer 32. And a signal indicating the frequency and phase of the target assist force Fat are input to the electronic control unit 34.

  In step 170, the vibration force reduction amount ΔF is calculated according to the above equation 3, and the phase of the axial force Fo and the target assist force Fat is opposite to each other by determining whether or not the inequality of the above equation 4 is satisfied. If a negative determination is made, the control constant A is changed according to a predetermined procedure in step 180, and a signal indicating the changed control constant A is output to the electronic control unit 20. After that, the process returns to step 130, and when an affirmative determination is made, the process proceeds to step 190.

  In step 190, the control constant A is fixed to the current value, and a signal indicating the control constant A is output to the electronic control unit 20 as a fixed value. In step 200, the vibrator 28 is output. Is stopped. When the electronic control unit 20 receives the determined control constant A, it stores the value in a storage means such as a ROM.

  Thus, according to the illustrated embodiment, the phase-compensated steering torque Tsp is calculated based on the steering torque Ts and the control constant A in steps 20 and 30, and the phase-compensated steering torque is calculated in steps 40 and 50. A target assist torque Tat is calculated based on Tsp, and a target assist force Fat at the rack bar 14 is calculated based on the target assist torque Tat.

  In a state where the rack bar 14 is vibrated by the shaker 28, a signal indicating the frequency and phase of the axial force Fo due to the vibration of the rack bar 14 is electronically controlled from the frequency / phase analyzer 32 in steps 130 and 140. A signal indicating the frequency and phase of the target assist force Fat input from the electronic control unit 20 in steps 150 and 160 is input to the electronic control unit 34.

  Further, in step 170, the vibration force reduction amount ΔF is calculated according to the above equation 3, and the phase of the axial force Fo and the target assist force Fat is opposite to each other by determining whether or not the inequality of the above equation 4 is satisfied. In step 180, the control constant A is changed according to a predetermined procedure until it is determined that the phases of the axial force Fo and the target assist force Fat are opposite to each other. When it is determined that the phases of the target assist force Fat are opposite to each other, in step 190, a signal indicating the control constant A at that time is output to the electronic control device 20, and the value is stored in the ROM of the electronic control device 20. Is stored as a control constant A determined in the storage means.

  Therefore, according to the illustrated control constant determination device 26 and the control constant determination method by the control constant determination device 26, the phase of the vibration force and the phase of the steering assist force input to the electric power steering device 10 from the side of the steering wheel are obtained. The predetermined control constant A to be reversed can be obtained easily, accurately and reliably.

  Further, according to the illustrated embodiment, the predetermined control constant A is a control constant that determines the phase and gain of the steering assist force with respect to the steering torque Ts, and is therefore input to the electric power steering apparatus 10 from the side of the steered wheels. It is possible to easily, accurately and reliably determine the predetermined control constant A that generates the steering assist force that effectively opposes the vibration force while making the phase of the vibration force and the phase of the steering assist force in opposite phases.

  FIG. 5 is a schematic diagram showing a vehicle equipped with an electric power steering apparatus according to the present invention. In FIG. 5, the same members as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.

  As shown in FIG. 5, the inner ends of the tie rods 42L and 42R are connected to both ends of the rack bar 14 of the electric power steering apparatus 10 by ball joints 40FL and 40FR, and the outer ends of the tie rods 42L and 42R are shown in the drawing. Are connected to the knuckle arms of the left and right front wheels 44FL and 44FR by ball joints not shown. Therefore, the left and right front wheels 44FL and 44FR, which are the steering wheels, are connected to the rack bar 14 and the tie rods 42L and 42R by the rack-and-pinion type electric power steering device 10 driven in response to the operation of the steering wheel 11 by the driver. It is steered through.

  As in the case of determining the control constant, the electric motor 12 of the electric power steering apparatus 10 is controlled by the electronic control apparatus 20. A signal indicating the steering torque Ts from the torque sensor 24, a signal indicating the vehicle speed V from the vehicle speed sensor 46, and a signal indicating the steering angle θ from the steering angle sensor 48 are input to the electronic control device 20.

  The electronic control unit 20 stores the flow chart shown in FIG. 6 and the control constant A determined as described above. Based on the steering torque Ts and the control constant A, the electronic control unit 20 calculates the steering torque Tsp after phase compensation according to the above equation 1. The target assist torque Tat is calculated based on the steering torque Tsp, the vehicle speed V, and the steering angle θ after the phase compensation, and the electric motor 12 is controlled so that the steering assist torque becomes the target assist torque Tat. In addition to reducing the steering burden, vibration transmitted from the left and right front wheels 44FL and 44FR to the steering wheel 11 via the electric power steering device 10 is reduced.

  Next, the steering assist torque control in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 6 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals until the ignition switch is opened.

  First, in step 310, a signal indicating the steering torque Ts is read, and in step 320, the same procedure as in step 30 is performed, and the equation 1 is based on the steering torque Ts and the control constant A. The steering torque Tsp after the phase compensation is calculated, and in step 330, the target basic assist torque Tabt is calculated from the map corresponding to the graph shown in FIG. 7 based on the steering torque Tsp after the phase compensation.

  In step 340, the differential value Tsd of the steering torque Ts is calculated. Based on the differential value Tsd of the steering torque, the steering torque differential value compensation basic torque Tad is calculated from the map corresponding to the graph shown in FIG. Based on V, the vehicle speed coefficient Kad is calculated from a map corresponding to the graph shown in FIG. 9, and the steering torque differential value compensation torque Tadt is calculated as the product of the steering torque differential value compensation basic torque Tad and the vehicle speed coefficient Kad.

  In step 350, the steering speed θd is calculated as a differential value of the steering angle θ, and the steering speed compensation basic torque Tas is calculated from the map corresponding to the graph shown in FIG. Based on the map corresponding to the graph shown in FIG. 11, the vehicle speed coefficient Kas is calculated, and the steering speed compensation torque Tast is calculated as the product of the steering speed compensation basic torque Tas and the vehicle speed coefficient Kas.

  In step 360, the target assist torque Tat is calculated as the sum of the target basic assist torque Tabt, the steering torque differential value compensation torque Tadt, and the steering speed compensation torque Tast. In step 370, based on the target assist torque Tat. A target control current for the electric motor 12 is calculated and controlled such that the control current for the electric motor 12 becomes the target control current, and thereby the electric motor 12 is controlled so that the steering assist torque becomes the target steering assist torque Tat.

  Thus, according to the illustrated embodiment, the phase-compensated steering torque Tsp is calculated in step 320 based on the steering torque Ts and the control constant A according to the above equation 1, and in step 330 the phase-compensated steering torque Tsp. The target basic assist torque Tabt is calculated based on the above, and the steering torque differential value compensation torque Tadt is calculated based on the steering torque differential value Tsd and the vehicle speed V in step 340, and the steering speed θd and vehicle speed V are calculated in step 350. Based on this, the steering speed compensation torque Tast is calculated.

  In step 360, the target assist torque Tat is calculated as the sum of the target basic assist torque Tabt, the steering torque differential value compensation torque Tadt, and the steering speed compensation torque Tast. In step 370, the steering assist torque is converted into the target steering assist torque. The electric motor 12 is controlled to be Tat.

  Therefore, according to the illustrated embodiment, the steering torque Tsp after phase compensation is calculated based on the control constant A and the steering torque Ts determined by the control constant determination device 26 and the control constant determination method by the control constant determination device 26 described above. Since the target basic assist torque Tabt is calculated based on the steering torque Tsp after phase compensation, even if high-frequency vibration caused by wheel vibration during flutter or braking is input to the electric power steering device 10 from the steering wheel side. The vibration force can be effectively canceled by the target basic assist torque Tabt, thereby effectively reducing the transmission of vibration to the steering wheel 11 via the electric power steering device 10.

  Further, according to the illustrated embodiment, it is not necessary to detect the vibration of the constituent member of the electric power steering apparatus 10 such as the steering shaft 22, and the sensor for detecting the vibration is not necessary. Compared to the steering device, the structure of the electric power steering device can be simplified and the cost can be reduced.

  Next, the steering assist torque control for determining the control constant in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing a switch (not shown), and is repeatedly executed at predetermined time intervals until the switch is opened.

  First, in step 10, a signal indicating the control constant A input from the electronic control unit 34 is read, and in step 20, a signal indicating the steering torque Ts detected by the torque sensor 24 is read. In step 30, the steering torque Tsp after phase compensation is calculated according to the above equation (1).

  In step 40, the vehicle speed V is set to 0, and the target assist torque Tat is calculated from the map corresponding to the graph shown in FIG. 3 based on the steering torque Tsp after phase compensation. In step 50, the target assist torque Tat is calculated. Based on this, the target assist force Fat at the rack bar 14 is calculated, and a signal indicating the target assist force Fat is output to the control constant determining device 26.

  In step 60, the target control current for the electric motor 12 is calculated based on the target assist torque Tat, and the control current for the electric motor 12 is controlled to become the target control current, whereby the steering assist torque is changed to the target steering assist torque Tat. The electric motor 12 is controlled so that it becomes.

  Next, the control constant determination control routine in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 4 is also started by closing a switch not shown in the figure, and is repeatedly executed at predetermined time intervals until the switch is opened.

  First, at step 110, the control constant A is set to a preset initial value Ao, and a signal indicating the control constant A is output to the electronic control unit 20, and at step 120, the vibrator 28 is set. In response to this, a vibration start command signal is output, whereby the vibration of the rack bar 14 by the vibration generator 28 is started.

  In step 130, a signal indicating the axial force Fo of the rack bar 14 is input from the force sensor 30 to the control constant determination device 26. In step 140, the phase analysis of the axial force Fo is performed to the frequency / phase analyzer 32. A signal indicating the frequency and phase of the axial force Fo is input to the electronic control unit 34.

  In step 150, a signal indicating the target assist force Fat is input from the electronic control unit 20 to the frequency / phase analyzer 32. In step 160, the phase analysis of the target assist force Fat is performed to the frequency / phase analyzer 32. And a signal indicating the frequency and phase of the target assist force Fat are input to the electronic control unit 34.

  In step 170, the vibration force reduction amount ΔF is calculated according to the above equation 3, and the phase of the axial force Fo and the target assist force Fat is opposite to each other by determining whether or not the inequality of the above equation 4 is satisfied. If a negative determination is made, the control constant A is changed according to a predetermined procedure in step 180, and a signal indicating the changed control constant A is output to the electronic control unit 20. After that, the process returns to step 130, and when an affirmative determination is made, the process proceeds to step 190.

  In step 190, the control constant A is fixed to the current value, and a signal indicating the control constant A is output to the electronic control unit 20 as a fixed value. In step 200, the vibrator 28 is output. Is stopped. When the electronic control unit 20 receives the determined control constant A, it stores the value in a storage means such as a ROM.

  Thus, according to the illustrated embodiment, the phase-compensated steering torque Tsp is calculated based on the steering torque Ts and the control constant A in steps 20 and 30, and the phase-compensated steering torque is calculated in steps 40 and 50. A target assist torque Tat is calculated based on Tsp, and a target assist force Fat at the rack bar 14 is calculated based on the target assist torque Tat.

  In a state where the rack bar 14 is vibrated by the shaker 28, a signal indicating the frequency and phase of the axial force Fo due to the vibration of the rack bar 14 is electronically controlled from the frequency / phase analyzer 32 in steps 130 and 140. A signal indicating the frequency and phase of the target assist force Fat input from the electronic control unit 20 in steps 150 and 160 is input to the electronic control unit 34.

  Further, in step 170, the vibration force reduction amount ΔF is calculated according to the above equation 3, and the phase of the axial force Fo and the target assist force Fat is opposite to each other by determining whether or not the inequality of the above equation 4 is satisfied. In step 180, the control constant A is changed according to a predetermined procedure until it is determined that the phases of the axial force Fo and the target assist force Fat are opposite to each other. When it is determined that the phases of the target assist force Fat are opposite to each other, in step 190, a signal indicating the control constant A at that time is output to the electronic control device 20, and the value is stored in the ROM of the electronic control device 20. Is stored as a control constant A determined in the storage means.

  Therefore, according to the illustrated control constant determination device 26 and the control constant determination method by the control constant determination device 26, the phase of the vibration force and the phase of the steering assist force input to the electric power steering device 10 from the side of the steering wheel are obtained. The predetermined control constant A to be reversed can be obtained easily, accurately and reliably.

  Further, according to the illustrated embodiment, the predetermined control constant A is a control constant that determines the phase and gain of the steering assist force with respect to the steering torque Ts, and is therefore input to the electric power steering apparatus 10 from the side of the steered wheels. It is possible to easily, accurately and reliably determine the predetermined control constant A that generates the steering assist force that effectively opposes the vibration force while making the phase of the vibration force and the phase of the steering assist force in opposite phases.

  FIG. 5 is a schematic diagram showing a vehicle equipped with an electric power steering apparatus according to the present invention. In FIG. 5, the same members as those shown in FIG. 1 are denoted by the same reference numerals as those shown in FIG.

  As shown in FIG. 5, the inner ends of the tie rods 42L and 42R are connected to both ends of the rack bar 14 of the electric power steering apparatus 10 by ball joints 40FL and 40FR, and the outer ends of the tie rods 42L and 42R are shown in the drawing. Are connected to the knuckle arms of the left and right front wheels 44FL and 44FR by ball joints not shown. Therefore, the left and right front wheels 44FL and 44FR, which are the steering wheels, are connected to the rack bar 14 and the tie rods 42L and 42R by the rack-and-pinion type electric power steering device 10 driven in response to the operation of the steering wheel 11 by the driver. It is steered through.

  As in the case of determining the control constant, the electric motor 12 of the electric power steering apparatus 10 is controlled by the electronic control apparatus 20. A signal indicating the steering torque Ts from the torque sensor 24, a signal indicating the vehicle speed V from the vehicle speed sensor 46, and a signal indicating the steering angle θ from the steering angle sensor 48 are input to the electronic control device 20.

  The electronic control unit 20 stores the flow chart shown in FIG. 6 and the control constant A determined as described above. Based on the steering torque Ts and the control constant A, the electronic control unit 20 calculates the steering torque Tsp after phase compensation according to the above equation 1. The target assist torque Tat is calculated based on the steering torque Tsp, the vehicle speed V, and the steering angle θ after the phase compensation, and the electric motor 12 is controlled so that the steering assist torque becomes the target assist torque Tat. In addition to reducing the steering burden, vibration transmitted from the left and right front wheels 44FL and 44FR to the steering wheel 11 via the electric power steering device 10 is reduced.

  Next, the steering assist torque control in the embodiment will be described with reference to the flowchart shown in FIG. The control according to the flowchart shown in FIG. 6 is started by closing an ignition switch (not shown), and is repeatedly executed at predetermined time intervals until the ignition switch is opened.

  First, in step 310, a signal indicating the steering torque Ts is read, and in step 320, the same procedure as in step 30 is performed, and the equation 1 is based on the steering torque Ts and the control constant A. The steering torque Tsp after the phase compensation is calculated, and in step 330, the target basic assist torque Tabt is calculated from the map corresponding to the graph shown in FIG. 7 based on the steering torque Tsp after the phase compensation.

  In step 340, the differential value Tsd of the steering torque Ts is calculated. Based on the differential value Tsd of the steering torque, the steering torque differential value compensation basic torque Tad is calculated from the map corresponding to the graph shown in FIG. Based on V, the vehicle speed coefficient Kad is calculated from a map corresponding to the graph shown in FIG. 9, and the steering torque differential value compensation torque Tadt is calculated as the product of the steering torque differential value compensation basic torque Tad and the vehicle speed coefficient Kad.

  In step 350, the steering speed θd is calculated as a differential value of the steering angle θ, and the steering speed compensation basic torque Tas is calculated from the map corresponding to the graph shown in FIG. Based on the map corresponding to the graph shown in FIG. 11, the vehicle speed coefficient Kas is calculated, and the steering speed compensation torque Tast is calculated as the product of the steering speed compensation basic torque Tas and the vehicle speed coefficient Kas.

  In step 360, the target assist torque Tat is calculated as the sum of the target basic assist torque Tabt, the steering torque differential value compensation torque Tadt, and the steering speed compensation torque Tast. In step 370, based on the target assist torque Tat. A target control current for the electric motor 12 is calculated and controlled such that the control current for the electric motor 12 becomes the target control current, and thereby the electric motor 12 is controlled so that the steering assist torque becomes the target steering assist torque Tat.

  Thus, according to the illustrated embodiment, the phase-compensated steering torque Tsp is calculated in step 320 based on the steering torque Ts and the control constant A according to the above equation 1, and in step 330 the phase-compensated steering torque Tsp. The target basic assist torque Tabt is calculated based on the above, and the steering torque differential value compensation torque Tadt is calculated based on the steering torque differential value Tsd and the vehicle speed V in step 340, and the steering speed θd and vehicle speed V are calculated in step 350. Based on this, the steering speed compensation torque Tast is calculated.

  In step 360, the target assist torque Tat is calculated as the sum of the target basic assist torque Tabt, the steering torque differential value compensation torque Tadt, and the steering speed compensation torque Tast. In step 370, the steering assist torque is converted into the target steering assist torque. The electric motor 12 is controlled to be Tat.

  Therefore, according to the illustrated embodiment, the steering torque Tsp after phase compensation is calculated based on the control constant A and the steering torque Ts determined by the control constant determination device 26 and the control constant determination method by the control constant determination device 26 described above. Since the target basic assist torque Tabt is calculated based on the steering torque Tsp after phase compensation, even if high-frequency vibration caused by wheel vibration during flutter or braking is input to the electric power steering device 10 from the steering wheel side. The vibration force can be effectively canceled by the target basic assist torque Tabt, thereby effectively reducing the transmission of vibration to the steering wheel 11 via the electric power steering device 10.

  Further, according to the illustrated embodiment, it is not necessary to detect the vibration of the constituent member of the electric power steering apparatus 10 such as the steering shaft 22, and the sensor for detecting the vibration is not necessary. Compared to the steering device, the structure of the electric power steering device can be simplified and the cost can be reduced.

  Although the present invention has been described in detail with reference to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the vibration force reduction amount ΔF is calculated in step 170 according to the above equation 3, and the axial force Fo and the target assist force are determined by determining whether or not the inequality of the above equation 4 is satisfied. Whether or not the phases of Fat are opposite to each other is determined. However, whether or not the phases of the axial force Fo and the target assist force Fat are opposite to each other is determined by, for example, α. The positive constant of π / 2 or less may be corrected so as to be performed by determining whether or not the phase difference θ between the target assist force Fat and the axial force Fo is not less than π−α and not more than π + α.

  In the above embodiment, the target assist force Fat at the rack bar 14 is calculated based on the target assist torque Tat at step 50, and the phase of the axial force Fo and the target assist force Fat at step 170. Are determined to be in reverse phase with each other, the actual assist force based on the target assist torque Tat is estimated based on the control current supplied to the motor 12, and in step 170, Then, the axial force Fo and the actual assist force may be corrected so as to determine whether the phases of the assist force and the actual assist force are opposite to each other.

  In the above embodiment, the target basic assist torque Tabt is calculated based on the steering torque Tsp after phase compensation based on the steering torque Ts and the control constant A in step 320, and in step 340, the steering torque is calculated. A steering torque differential value compensation torque Tadt is calculated based on the differential value Tsd and the vehicle speed V, a steering speed compensation torque Tast is calculated based on the steering speed θd and the vehicle speed V in step 350, and a target basic assist torque in step 360. The target assist torque Tat is calculated as the sum of Tabt, steering torque differential value compensation torque Tadt, and steering speed compensation torque Tast. The control constant A and the control constant A determined according to the determination method and determination apparatus of the present invention are as follows. As long as the target basic assist torque Tabt is calculated based on the steering torque Tsp after phase compensation based on the steering torque Ts Thus, the control amount added to the target basic assist torque Tabt may be any control amount known in the art.

  In the above-described embodiment, the electric power steering device 10 is a rack coaxial type electric power steering device, but the electric power steering device 10 to which the present invention is applied assists the steering shaft or the pinion shaft. An electric power steering device of a type to which torque is applied may be used.

1 is a schematic configuration diagram showing an electric power steering apparatus and a control constant determination apparatus to which one embodiment of a control constant determination method according to the present invention is applied. It is a flowchart which shows the steering assist torque control routine for control constant determination in an Example. It is a graph which shows the relationship between the steering torque Tsp after the phase compensation at the time of control constant determination control in an Example, and the target assist torque Tat. It is a flowchart which shows the control constant determination control routine in an Example. 1 is a schematic configuration diagram showing a vehicle equipped with an electric power steering apparatus according to the present invention. It is a flowchart which shows the steering assist torque control routine in an Example. It is a graph which shows the relationship between the steering torque Tsp after phase compensation at the time of normal control, and the target assist torque Tat. It is a graph which shows the relationship between the differential value Tsd of steering torque, and steering torque differential value compensation torque Tad. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kad. It is a graph which shows the relationship between steering speed (theta) sd and steering speed compensation torque Tas. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kas. It is a graph which shows the example of the force F transmitted to the steering shaft side from the axial force Fo, the target assist force Fat, and a rack bar.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Steering wheel 14 Rack bar 16 Electric power steering device 20 Electronic control device 24 Torque sensor 26 Control constant determination device 28 Exciter 30 Force sensor 32 Frequency / phase analysis device 34 Electronic control device 44FL and 44FR Left and right front wheels 46 Vehicle speed sensor 48 Steering angle sensor

Claims (5)

  For an electric power steering device that detects steering torque and generates a steering assist force based on at least the steering torque and a predetermined control constant, vibration input from the steering wheel side passes through the electric power steering device and is a steering input means. In accordance with a control constant determining method for an electric power steering apparatus that determines a predetermined control constant so as to suppress transmission to the steering wheel, the electric power steering apparatus is vibrated from the steered wheel side by a vibration means, and steering torque And calculating a steering assist force based on a predetermined control constant, and changing the predetermined control constant until the phase of the excitation force of the excitation means and the phase of the steering assist force are in opposite phases. A control constant determination method for an electric power steering apparatus.   2. The control constant determining method for an electric power steering apparatus according to claim 1, wherein the predetermined control constant is a control constant that defines a phase of a steering assist force with respect to at least a steering torque.   For an electric power steering device that detects steering torque and generates a steering assist force based on at least the steering torque and a predetermined control constant, vibration input from the steering wheel side passes through the electric power steering device and is a steering input means. A control constant determining device for an electric power steering device that determines a predetermined control constant so as to suppress transmission to the motor, a vibration means for vibrating the electric power steering device from the steering wheel side, A means for detecting a vibration force of the vibration means, a means for analyzing the phase of the vibration force and the steering assist force, and a predetermined phase until the phase of the vibration force and the phase of the steering assist force are reversed. And a control constant determining device for the electric power steering apparatus.   4. The control constant determining apparatus for an electric power steering apparatus according to claim 3, wherein the predetermined control constant is a control constant that defines a phase of a steering assist force with respect to at least a steering torque. 3. The control constant determining method according to claim 1, wherein the predetermined control constant is detected by a steering torque and generates a steering assist force based on at least the steering torque and a predetermined control constant. Alternatively, the electric power steering apparatus is a control constant determined by the control constant determination apparatus according to claim 3.

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