JP4961783B2 - Vehicle steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accomplish a steering reaction force control mechanism capable of suitably setting a steering reaction force according to a driver, and to contribute to the reduction of a burden of steering or accurate steering angle control. <P>SOLUTION: A control unit 11 detects an operation amount of steering operation of a drive applied to a steering wheel performed at predetermined timing and presumes a mechanical impedance of the driver based on the detected operation amount. Thereafter, the steering reaction force of the steering wheel is controlled based on the presumed mechanical impedance. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a vehicle steering apparatus.

  Currently, many automobiles are equipped with a power steering device. The power steering device is very useful for reducing the steering force.

On the other hand, the steering device is also required to obtain feedback of reaction force appropriate for steering, and various reaction force control mechanisms have been proposed. For example, Patent Document 1 discloses a mechanism for controlling a steering reaction force according to a vehicle speed and a road surface condition. Patent Document 2 discloses a mechanism for controlling a steering reaction force based on a vehicle speed and a deviation between a target value and an actual value of a tire turning angle.
JP-A-11-78947 Japanese Patent Laid-Open No. 2004-210024

  However, the appropriate steering reaction force should vary depending on the driver. Patent Document 2 proposes that the addition and subtraction of the steering reaction force can be adjusted according to the driver's preference, but at present, this cannot be automatically performed.

  Therefore, an object of the present invention is to realize a steering reaction force control mechanism that can appropriately set a steering reaction force according to a driver, and to contribute to a reduction in steering burden or accurate steering angle control.

A vehicle steering apparatus according to an aspect of the present invention includes a steering wheel, a detection unit that detects an operation amount of a steering operation performed on the steering wheel by a driver at a predetermined timing, and the operation detected by the detection unit. An estimation means for estimating a mechanical impedance of the driver based on the amount; a control means for controlling a steering reaction force of the steering wheel based on the mechanical impedance estimated by the estimation means ; Road surface step detecting means for detecting, and the predetermined timing is within a predetermined period when the road surface step is detected by the road surface step detecting means .

  According to this configuration, the mechanical impedance is estimated based on the operation amount of the driver's steering operation performed at a predetermined timing, so that an appropriate steering reaction force can be set easily and accurately.

Further , the kickback accompanying the passage of the road surface step of the vehicle can be used as a trigger for causing the driver to perform the steering operation. Therefore, in this case, a separate process such as forcibly rotating the steering wheel as a trigger for causing the driver to perform the steering operation is unnecessary. Thereby, the operation amount of the steering operation of the driver can be measured with a simple configuration.

  According to a preferred embodiment of the present invention, there is further provided a torque sensor that detects a rotational torque of the steering wheel, and a steering angle sensor that detects a steering angle of the steering wheel, wherein the estimating means includes the torque sensor. Preferably, the mechanical impedance is estimated based on the output of the rudder angle sensor.

  According to this configuration, the operation amount of the driver's steering operation can be objectively and accurately measured by the torque sensor and the steering angle sensor.

  According to a preferred embodiment of the present invention, the predetermined timing is determined when the output of the torque sensor changes more than a predetermined value within a predetermined time, or when the output of the rudder angle sensor is predetermined within a predetermined time. Preferably, when the value changes more than the value.

  According to this configuration, it is possible to reduce the influence of disturbance on the operation amount of the steering operation (that is, S / N is improved). Therefore, the mechanical impedance can be estimated with high accuracy.

  According to a preferred embodiment of the present invention, the detection means superimposes and inputs a characteristic signal for measuring the mechanical impedance to the steering characteristic, and the steering wheel of the steering wheel according to the steering characteristic superimposed with the characteristic signal. It is preferable to detect an operation amount of the steering operation of the driver with respect to the rotation.

  According to this configuration, the superimposed characteristic itself becomes a trigger for causing the driver to perform a steering operation. Therefore, the operation amount of the steering operation of the driver can be reliably measured.

  According to the present invention, it is possible to appropriately set the steering reaction force according to the driver, thereby contributing to reduction of the steering burden or accurate steering angle control.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, It shows only the specific example advantageous for implementation of this invention. In addition, not all combinations of features described in the following embodiments are indispensable as means for solving the problems of the present invention. Various embodiments will be described below, but it is needless to say that the embodiments can be appropriately combined.

(Embodiment 1)
FIG. 1 is a diagram illustrating a schematic configuration of a steering device 1 according to the present embodiment.

  In FIG. 1, 2 is a steering wheel, and a steering angle sensor 3 for detecting the steering angle and a steering reaction force generating motor 4 for applying a steering reaction force are attached to the steering wheel 2.

  The pair of left and right tires 6, 6 are connected by knuckle arms 7, 7, tie rods 8, 8 and a steering rod 9, and the steering rod 9 is driven in the axial direction at the center of the steering rod 9. A steering motor 10 for providing a cutting angle to 6 is provided.

  The steering device 1 shown in FIG. 1 is a so-called steer-by-wire type. That is, the steering rod 9 is not mechanically connected to the steering wheel 2 by a steering shaft or the like, but is electrically connected. The control unit (C / U) 11 controls the steering control through this electrical connection. The detection value of the steering angle sensor 3 (corresponding to the operation amount given to the steering wheel 2 by the driver) is input to the control unit 11, and the control unit 11 is configured to output the control value to the steering motor 10. Yes. Then, the control unit 11 basically calculates the target value of the turning angle of the tire 6 based on the detected value of the steering angle sensor 3, and controls the tire turning angle by performing feedback control of the steering motor 10 according to the target value. To do.

  The steering device 1 further includes the following components. Reference numeral 12 denotes a vehicle speed sensor that detects the vehicle speed, and reference numeral 13 denotes a seat slide sensor that detects a seat slide position of a driver's seat (not shown). The steering device 1 also has a telescopic mechanism (not shown) that allows the position of the steering wheel 2 in the vehicle front-rear direction to be adjusted, and a telescopic position sensor or a steer position sensor 14 that detects the telescopic position accordingly. Is also provided. Reference numeral 15 denotes an IC card reader for reading driver information (details will be described later) from the IC card 15a. Reference numeral 16 denotes an image sensor (for example, composed of a CCD camera) that acquires image information of the driver.

  FIG. 2 is a block diagram showing the configuration of the control unit 11.

  As shown in the figure, the control unit 11 includes a CPU 111 that performs overall control of the apparatus, a RAM 112 that provides a work area for the CPU 111, a ROM 113 that stores fixed programs and data, and an IC card reader. 15 includes an interface (I / F) 116 for connecting 15 and an interface 117 for connecting the image sensor 16. Specifically, the ROM 113 includes a steering control program 114 for realizing the basic steering control and steering reaction force control described later, and a human impedance calculation reference table (LUT) referred to in steering reaction force control described later. 115 is stored. The CPU 111, RAM 112, ROM 113, and interfaces 116 and 117 are each connected to the bus 118. The steering angle sensor 3, the vehicle speed sensor 12, the seat slide sensor 13, and the telescopic position sensor or steer position sensor 14 are also directly connected to the bus 118, for example, and the IC card reader 15 and the image sensor 16 are respectively connected to the interface 116. And 117 are connected to the bus 118.

  The configuration of the steering device 1 in the present embodiment is generally as described above.

  Next, steering reaction force control in this embodiment will be described.

  A driver grasping the steering wheel 2 can be regarded as resistance to rotation of the steering wheel when viewed from the steering wheel 2 side. In the present specification, this resistance is called “human impedance” or “mechanical impedance” of the driver. Human impedance is a value prescribed for the driver's steering force. Since the steering force varies depending on the driver, it can be said that the human impedance varies depending on the driver. Accordingly, by obtaining this human impedance, it is possible to set the steering reaction force according to the driver. As will be described below, in this embodiment, human impedance is estimated based on gender differences, age, physique, and the like.

  The steering torque (hereinafter referred to as “human impedance torque”) T applied to the steering wheel 2 obtained from the human impedance of the driver can be expressed by the following equation.

However,

Are respectively the steering angle, steering angle change rate, and steering angle change acceleration of the steering wheel 2. K, B, and M represent human impedance characteristic parameters, and specifically indicate a stiffness coefficient, a viscosity coefficient, and an inertia coefficient, respectively.

  FIG. 3 is a flowchart showing a steering reaction force control process in the present embodiment. A program corresponding to this flowchart is included in the steering control program 114 stored in the ROM 113 and is executed by the CPU 111.

  First, in step S101, the driver information written in the IC card 15a is read by the IC card reader 15. The driver information required here is, for example, the gender, age, weight, and height of the driver.

  Next, in step S102, the physique of the driver is estimated based on the read information. If the driver's sex, age, weight, and height data are all successfully read in step S101, the read values can be used as estimated values as they are.

  However, it is expected that such information is not input to the IC card 15a and reading of these data fails. Therefore, in such a case, the physique of the driver is estimated based on the seat slide position specified by the detection value of the seat slide sensor 13 and the telescopic position specified by the detection value of the telescopic position sensor or the steer position sensor 14. Good. For example, a reference table describing the relationship between the seat slide position and telescopic position, height and weight is stored in the ROM 113 in advance, and the height and weight of the driver can be estimated by referring to this.

  Alternatively, the image of the driver may be detected using the image sensor 16 provided toward the driver, and the physique of the driver may be estimated based on the detection result. For example, a plurality of representative driver template images each having a different gender and physique are stored in advance, and the gender corresponding to the template image most similar to the image obtained from the image sensor 16 by a known pattern matching technique, The physique should be specified.

  Next, in step S103, based on the physique estimation result in step S102, a process of calculating a stiffness coefficient K, a viscosity coefficient B, and an inertia coefficient M, which are characteristic values of human impedance, is performed. In the present embodiment, these coefficients can be specified by referring to the human impedance calculation LUT 115 stored in the ROM 113.

  FIG. 4 shows a data structure example of the human impedance calculation LUT 115.

  The human impedance calculation LUT 115 in this embodiment includes LUTs of a stiffness coefficient K, a viscosity coefficient B, and an inertia coefficient M. FIGS. 9A, 9B, and 9C show structural examples of LUTs having a stiffness coefficient K, a viscosity coefficient B, and an inertia coefficient M, respectively. As shown in the figure, coefficient values are arranged according to height and weight, and corresponding coefficients can be output by inputting height and weight. Also, as shown in the drawing, each LUT has a separate sub-LUT for each gender and age, and it is preferable to refer to the sub-LUT according to gender and age.

  Next, in step S104, the human impedance torque T is calculated by applying the stiffness coefficient K, the viscosity coefficient B, and the inertia coefficient M specified in step S103 to the above equation (1).

  Next, in step S105, the target steering reaction force T0 is calculated from the human impedance torque T obtained in step S104. T0 is calculated by the following equation, for example.

T0 = T + k
Here, k is a correction term composed of a predetermined constant.

  Next, in step S106, a steering reaction force change process is performed. FIG. 5 shows a specific procedure of this steering reaction force changing process.

  First, in step S61, it is determined from the detection value of the vehicle speed sensor 12 whether or not the vehicle is currently stopped. If it is stopped, the process proceeds to step S62. If it is not stopped, the process proceeds to step S67.

  In step S62, it is determined whether or not the driver is the same as in the previous process. If the driver information can be read from the IC card reader 15, it can be determined using the information. When the determination from the IC card is not possible, the determination may be made by using the image sensor 16, the seat slide sensor 13, the telescopic position sensor or the steer position sensor 14 in the same manner as described above. If it is determined that the driver is the same as the previous one, the process proceeds to step S63, and if not, the process proceeds to step S66.

  In step S63, a change amount ΔT (= T0−Tr) from the current steering reaction force Tr is calculated.

  Next, in step S64, it is determined whether ΔT is larger than the previous change amount ΔTbefore. If ΔT is larger than the previous change amount ΔTbefore, the process proceeds to step S65, and if not, the process proceeds to step S66.

  In step S65, the current steering reaction force Tr ± ΔT × α (where 0.1 ≦ α ≦ 0.9) is set as the final target steering reaction force T00. This T00 is smaller than the target steering reaction force T0 calculated in step S105.

  In one step S66, Tr ± ΔT is set as the final target steering reaction force T00. This T00 is equal to the target steering reaction force T0 calculated in step S105.

  If the vehicle is not stopped in step S61, the process proceeds to step S67. In step S67, it is determined whether or not the vehicle is traveling straight ahead based on the detection value of the rudder angle sensor 3. If the vehicle is traveling straight ahead, the process proceeds to step S68; otherwise, the process proceeds to step S69.

  In step S68, the current steering reaction force Tr ± ΔT × β (where 0.1 ≦ β ≦ 0.9) is set as the final target steering reaction force T00. This T00 is smaller than the target steering reaction force T0 calculated in step S105. Although it is said that the vehicle is traveling straight ahead at this time, it is not preferable to change the steering feeling rapidly, so it is preferable to gradually change the value of β.

  On the other hand, in step S69, the target steering reaction force T0 calculated in step S105 is directly used as the final target steering reaction force T00. That is, since the steering is in progress at this point and it is not preferable to change the steering feeling, the change is prohibited.

  According to Embodiment 1 demonstrated above, a steering reaction force can be set appropriately according to a driver.

  In the first embodiment, the steer-by-wire type steering apparatus as shown in FIG. 1 has been described, but the present invention is not limited to this. That is, a conventional type in which the steering rod 9 is mechanically connected to the steering wheel 2 via the steering shaft 21 as shown in FIG. Note that the configuration in the case of the conventional type will be described. The steering rod 9 is connected to the steering shaft 22 via the speed reduction mechanism portion 22, and the steering reaction force generation motor 4 is connected to the speed reducer rear portion 22. Configured to work. Even with such a configuration, the above-described embodiment can be similarly applied.

(Embodiment 2)
FIG. 7 is a diagram illustrating a schematic configuration of the steering device 1 according to the present embodiment. This steering device 1 is a steer-by-wire type similar to that shown in FIG. The same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. Below, a different part from FIG. 1 is demonstrated.

  The steering wheel 2 is provided with a steering torque sensor 71 for detecting a steering torque, a pressure sensor 72 for detecting a gripping state of the driver's steering wheel, and a gripping position of the steering wheel from a change in capacitance. An electrostatic sensor 73 for determination is provided.

  In addition to this, the steering device 1 according to the present embodiment includes a road surface sensor 74 for detecting a low μ road and a road surface step, an engine start sensor 75 for detecting engine start, and a pulse sensor for detecting driver tension. 76. When the vehicle is a so-called hybrid vehicle that uses an electric motor as a drive source in addition to the engine, the engine start sensor 75 detects the ON of the start switch of the electric motor.

  The steering torque sensor 71, pressure sensor 72, electrostatic sensor 73, road surface sensor 74, engine start sensor 75, and pulse sensor 76 are each connected to the control unit 11.

  In the present embodiment, the steering reaction force generation motor 4 is also used to forcibly rotate the steering wheel 2 by a predetermined amount in order to estimate human impedance, as will be described later.

  Next, steering reaction force control in this embodiment will be described.

  FIG. 8 is a flowchart showing a steering reaction force control process in the present embodiment. When overviewing this flow, in step S204, as in step S103 in the first embodiment (FIG. 3), calculation processing of a stiffness coefficient, a viscosity coefficient, and an inertia coefficient representing the characteristics of human impedance is performed. However, this embodiment does not calculate the human impedance based on the driver's physique as in the first embodiment, but forcibly rotates the steering wheel 2 by a predetermined amount for measurement and reacts to it as described later. The human impedance is obtained based on the amount of steering operation performed by the driver. That is, the point that the human impedance is obtained by actual measurement is greatly different from the first embodiment. Thus, when obtaining human impedance by actual measurement, it is necessary to consider the disturbance received from the vehicle. Therefore, in steps S202 to S204, a process for removing disturbance is incorporated when estimating human impedance.

  The processes after step S205 are substantially the same as those in the first embodiment. That is, step S205 corresponds to the human impedance torque calculation process of step S104 in the first embodiment (FIG. 3), step S206 corresponds to the target steering reaction force calculation process of step S105, and step S207 corresponds to the steering of step S106. This corresponds to the reaction force changing process.

  In step S201, the steering angle sensor 3, the seat slide sensor 13, the telescopic position sensor or steer position sensor 14, the steering torque sensor 71, the pressure sensor 72, the electrostatic sensor 73, the road surface sensor 74, the engine start sensor 75, and the pulse sensor. Each detection value of 76 is input.

  Subsequent steps S202 to S204 relate to the calculation processing of the stiffness coefficient, the viscosity coefficient, and the inertia coefficient representing the characteristics of human impedance as described above.

  First, in step S202, human impedance including disturbance impedance is calculated. “Disturbance impedance” refers to resistance to rotation of the steering wheel caused by vehicle disturbance.

  FIG. 9 is a flowchart showing a specific example of processing for obtaining human impedance including disturbance impedance in step S202.

  First, in step S2021, it is determined whether the following measurement condition A is satisfied, for example.

Measurement condition A:
(1) The driver holds the steering wheel 2 and (2) the vehicle is in any of the following states (a) to (c).
(A) When starting the engine,
(B) During steady turning,
(C) After a predetermined time of continuous running.

  Whether or not the driver is gripping the steering wheel 2 in (1) can be determined by whether or not the output of the pressure sensor 72 is equal to or greater than a predetermined value. (2) The engine start in (a) can be known from the output of the engine start sensor 75, and the steady turn in (b) can be determined from the outputs of the rudder angle sensor 3 and the vehicle speed sensor 12. .

  Only when the measurement condition A is satisfied, the process proceeds to the next step S2022, and when the measurement condition A is not satisfied, the flow (S202) is exited.

  In step S2022, a measurement signal for driving the steering reaction force generation motor 4 is generated to forcibly rotate the steering wheel 2 by a predetermined amount. The driver's steering behavior in response to the steering wheel 2 forcibly rotated by the measurement signal generated here appears in the output of the steering angle sensor 3 and the output of the steering torque sensor 71. An example of this is shown in FIG.

  10, (a) shows the measurement signal, (b) shows the output of the steering angle sensor 3, and (c) shows the output of the steering torque sensor 71. As shown in (a), the measurement signal is preferably a pulse signal. The example of the solid line in the figure is a triangular wave pulse, but it may be a rectangular wave pulse as shown by a dotted line. The pulse width is preferably within 0.4 seconds, and the change in the steering angle at that time is within 5 °, or the steering torque is preferably 1.5N or more and 3N or less. More preferably, the pulse width is about 0.2 seconds as shown, and the change in the steering angle at that time is about 2 ° or the steering torque is about 2N.

  In the next step S2023, it is determined whether an estimation prohibition condition as shown below is satisfied.

Estimated prohibition conditions:
Satisfy at least one of the following (a) and (b).
(A) The pulse value detected by the pulse sensor 76 exceeds a predetermined value, and it is determined that the driver's tension is high.
(B) The road surface μ detected by the road surface sensor 74 is lower than a predetermined value.

  If the above condition is satisfied, it is determined that the human impedance cannot be stably estimated, and the flow exits (S202). In this way, human impedance estimation is prohibited when the above conditions are satisfied.

  If the estimation prohibition condition is not satisfied, the process proceeds to step S2024. The driver's steering behavior in response to the steering wheel 2 forcibly rotated by the measurement signal generated in step S2022 appears in the output of the steering angle sensor 3 and the output of the steering torque sensor 71. In step S2024, the stiffness coefficient K1, the viscosity coefficient B1, and the inertia coefficient M1 are calculated using the output of the steering angle sensor 3 and the output of the steering torque sensor 71 illustrated in FIG.

  FIG. 11 is a flowchart illustrating an example of the calculation procedure of each coefficient in step S2024.

  First, in step S241, the steering angle θ, the steering angle change rate θ ′, and the steering angle change acceleration θ ″ are detected from the output of the steering angle sensor 3 at each measurement, and the output TR of the steering torque sensor 71 is detected. .

  In the next step S242, the approximate curve L is obtained using the least square method so that the error from each measurement point is minimized in the space formed by θ, θ ′, θ ″ and the torque TR obtained in step S241. 12 is a diagram schematically showing an example of this calculation, and the error from each measurement point is minimized by applying the least square method in a three-dimensional space by θ, θ ′, and TR. A straight line L is obtained.

  Next, in step S243, as shown in FIG. 13A, the stiffness coefficient K1 is obtained from the inclination of the approximate straight line L obtained in step S242 on the θ-T coordinate plane. Next, in step S244, as shown in FIG. 13B, the viscosity coefficient B1 is obtained from the inclination of the approximate straight line L obtained in step S242 on the θ′-T coordinate plane. Next, in step S245, as shown in FIG. 13C, an inertia coefficient M1 is obtained from the inclination of the approximate straight line L obtained in step S242 on the θ-T coordinate plane.

  In this way, the stiffness coefficient K1, the viscosity coefficient B1, and the inertia coefficient M1 are calculated in step S2024 in FIG.

  The process proceeds to step S203 in FIG. In step S203, a process for obtaining disturbance impedance is performed. This processing step needs to be performed in a state where the driver releases the steering wheel 2. In this sense, this processing step does not always have to be performed in the processing flow of FIG. 8, and may be performed in advance before the vehicle is shipped from the factory, for example.

  FIG. 14 is a flowchart showing a specific example of the process for obtaining the disturbance impedance in step S203.

  First, in step S2031, for example, it is determined whether any of the following measurement conditions B (disturbance measurement conditions) is satisfied.

Measurement condition B:
(1) The vehicle is stopped and (2) the steering wheel 2 is not gripped by the driver.

  Whether or not the steering wheel 2 in (2) is held by the driver is determined based on the detection value of the pressure sensor 72. If the measurement condition B is satisfied, the process proceeds to step S2032, and if not, the process proceeds to step S2036.

  In step S2032, as in step S2022 of FIG. 9, a measurement signal for driving the steering reaction force generation motor 4 is generated to forcibly rotate the steering wheel 2 by a predetermined amount. The steering wheel 2 is forcibly rotated by the measurement signal generated here, and the steering behavior due to the disturbance at this time appears in the output of the steering angle sensor 3 and the output of the steering torque sensor 71.

  In step S2033, the stiffness coefficient K0, the viscosity coefficient B0, and the inertia coefficient M0 are calculated by the same method as that in step S2024 in FIG. 9 (that is, the method described with reference to FIGS. 11 to 13).

Next, in step S2034, it is checked whether or not the calculated stiffness coefficient K0, viscosity coefficient B0, and inertia coefficient M0 are within predetermined ranges. That is,
α1 <K0 <α2,
β1 <B0 <β2,
γ1 <M0 <γ2
Determine whether all of the above are satisfied. When a coefficient that is not within the predetermined range is calculated, it is considered that the coefficient is erroneously detected, and the process exits from this flow (S203). If each coefficient is within a predetermined range, the process proceeds to step S2035.

  In step S2035, an average value for a predetermined number of times is calculated for each of the stiffness coefficient K0, the viscosity coefficient B0, and the inertia coefficient M0. By doing so, the impedance of a steady disturbance can be calculated.

  On the other hand, if the measurement condition B is not satisfied in step S2031, the process proceeds to step S2036 to determine whether the following measurement condition C (disturbance negligible condition) is satisfied.

Measurement condition C:
(1) The vehicle is traveling straight ahead at high speed, or (2) is in steady turning within a certain angle.

  It can be determined from the outputs of the vehicle speed sensor 12 and the rudder angle sensor 3 whether (1) the vehicle is traveling straight ahead at high speed and whether the vehicle is in a steady turn within a certain angle (2). is there.

  When the measurement condition C is satisfied, the process proceeds to step S2037, the stiffness coefficient K0, the viscosity coefficient B0, and the inertia coefficient M0 are set to predetermined constants α0, β0, and γ0, respectively, and then the process exits the flow (S203). On the other hand, when the measurement condition C is not satisfied, the flow (S203) is directly exited.

  As described above, in step S203 of FIG. 8, the stiffness coefficient K0, the viscosity coefficient B0, and the inertia coefficient M0 related to the disturbance impedance are calculated.

The process proceeds to step S204 in FIG. 8 to obtain a human impedance from which the influence of disturbance has been removed. A specific example of step S204 is shown in FIG. As shown in the figure, here, the stiffness coefficient K, the viscosity coefficient B, and the inertia coefficient M are calculated as follows (step S2041).
Stiffness coefficient K: K = K1-K0,
Viscosity coefficient B: B = B1-B0,
Inertia coefficient M: M = M1-M0
Thus, the human impedance from which the influence of the disturbance is removed is obtained.

  Then, the process proceeds to step S205 in FIG. As described above, the processes after step S205 are substantially the same as those in the first embodiment. That is, step S205 corresponds to the human impedance torque calculation process of step S104 in the first embodiment (FIG. 3), step S206 corresponds to the target steering reaction force calculation process of step S105, and step S207 corresponds to the steering of step S106. This corresponds to the reaction force changing process. Therefore, description of these steps S205-S207 will use description of step S104-106 in Embodiment 1, and description is abbreviate | omitted here.

  According to Embodiment 2 demonstrated above, a steering reaction force can be set appropriately according to a driver.

  In the second embodiment described above, the steer-by-wire type steering apparatus as shown in FIG. 7 has been described. However, as in the first embodiment, a conventional type similar to that shown in FIG. Needless to say, the present invention is applicable to a steering device.

(Embodiment 3)
The third embodiment is a variation of the above-described second embodiment. FIG. 10A shows an example of the measurement signal, but it is conceivable to correct the measurement signal depending on the situation.

For example, when the measurement signal is generated in step S2022 of FIG. 9, the traveling state of the vehicle is detected, and the measurement signal is corrected according to the traveling state. Specifically, in the following traveling state, correction may be made so that the amplitude of the measurement signal is increased.
(A) When the road surface μ detected by the road surface sensor 74 is lower than a predetermined value. (B) When the rudder angle detected by the rudder angle sensor 3 becomes larger than a predetermined value during steady turning or after a predetermined period of continuous running.
(C) When the vehicle speed detected by the vehicle speed sensor 12 exceeds a predetermined value.

  In such a case, the influence of the disturbance of the vehicle is considered to be large.

In addition to the driving state, it is conceivable to perform the same correction for the driver state. For example, when the driver state is as follows, the measurement signal may be corrected so as to increase the amplitude.
(A) When it is determined by the output of the pressure sensor 72 that the driver is holding the steering wheel 2 with one hand instead of both hands.
(B) The pulse value detected by the pulse sensor 76 is below a predetermined value, and it is determined that the driver's tension is small.
(C) When the gripping position of the steering wheel 2 detected by the electrostatic sensor 73 is positioned in the vertical direction rather than the horizontal position.

  In such a case, since it is determined that the driver has a low ability to sense the forced rotation of the steering wheel 2, it is preferable to increase the amplitude of the measurement signal in such a case.

  In this way, the strength of the forced rotation of the steering wheel can be reliably transmitted to the driver without causing the driver to feel uncomfortable without being affected by disturbances.

(Embodiment 4)
The fourth embodiment is a variation of the second embodiment. FIG. 16 is a view similar to FIG. 10 showing examples of measurement signals, steering angle sensor outputs, and steering torque sensor outputs according to the present embodiment.

  This example is characterized in that the amplitude of the measurement signal is gradually increased. For example, as shown in FIG. 16A, a rectangular wave pulse having a pulse width of, for example, about 0.1 sec is continuously output while gradually increasing (P1, P2, P3, P4,...). If the pulse amplitude is as small as P1, the force of the forced rotation of the steering wheel 2 may be weak and may not be perceived by the driver, but in the process of increasing P2 and P3, the driver's reaction is obtained (FIG. 16 ( b), (c)). Then, for example, when it is detected based on the output of the steering angle sensor 3 that the change rate of the steering angle has changed more than a predetermined value, generation of the measurement signal can be stopped at that time.

  In this way, generation of useless measurement signals can be suppressed, and efficient human impedance measurement can be performed.

(Embodiment 5)
The fifth embodiment is a variation of the second embodiment. In this embodiment, a signal specialized for frequency components effective for estimation of the stiffness coefficient, viscosity coefficient, and inertia coefficient is generated as a measurement signal.

  For example, a single wave having a continuous pulse signal as shown in (a1) of FIG. 17 is generated as a measurement signal. This signal is a signal corresponding to a three-band frequency corresponding to an inertia term, a viscosity term, and a stiffness term indicating the characteristics of human impedance. The driver's reaction to this appears as steering angle sensor output and steering torque sensor output as shown in (b1) and (c1). Alternatively, a mixed wave obtained by mixing the pulses of (a1) as shown in (a2) may be generated as a measurement signal. The driver's reaction to this appears as steering angle sensor output and steering torque sensor output as shown in (b2) and (c2).

  The control unit 11 converts the output signal of the steering angle sensor 3 as shown in (b1) or (b2) into a frequency spectrum signal. FIG. 18 shows an example of an envelope of the frequency spectrum. As shown in the figure, three envelope peaks are observed in this envelope. Typically, such a peak appears in the vicinity of 10 Hz, in the vicinity of 20 Hz, and in the vicinity of 30 Hz, and includes characteristics of a stiffness coefficient, a viscosity coefficient, and an inertia coefficient, respectively. That is, this is a 3-band frequency signal corresponding to an inertia term, a viscosity term, and a stiffness term indicating the characteristics of human impedance. Therefore, each peak is cut out using a bandpass filter. Then, a robust estimation method, which is a parameter estimation method similar to the least square method in the above-described second embodiment, is applied to each of the cut out waveforms, whereby the stiffness coefficient K1, the viscosity coefficient B1, and the inertia coefficient M1 are obtained. presume.

  By such processing, the inertia coefficient, the viscosity coefficient, and the stiffness coefficient, which are characteristics of human impedance, can be efficiently obtained.

(Embodiment 6)
The sixth embodiment is a variation of the second embodiment. In this embodiment, a signal simulating a road reaction force is generated as a measurement signal. FIG. 19A shows an example of a measurement signal simulating a road surface reaction force. The driver's reaction to this appears as steering angle sensor output and steering torque sensor output as shown in (b) and (c).

  According to such a measurement signal simulating the road surface reaction force, the forced rotation of the steering wheel 2 for measuring the human impedance also simulates the road surface reaction force. Therefore, the driver does not feel uncomfortable due to the rotation of the steering wheel 2 for this measurement.

(Embodiment 7)
The human impedance calculation process (see flowcharts in FIGS. 8 and 9) in the second embodiment generates a measurement signal for driving the steering reaction force generation motor 4 to forcibly rotate the steering wheel 2 by a predetermined amount. (Step S2022 in FIG. 9), human impedance is estimated based on the amount of driver steering operation performed in response to the rotation of the steering wheel 2 driven by the steering reaction force generation motor 4 according to the measurement signal. (Step S2024).

  On the other hand, Embodiments 7 and 8 propose a method that eliminates the need for processing such as forcibly rotating the steering wheel as a trigger for causing the driver to perform a steering operation. That is, in the seventh and eighth embodiments, a method for detecting an operation amount of a driver's steering operation performed at a predetermined timing and estimating human impedance based on the operation amount will be described.

  First, in the present embodiment, kickback associated with passage of a road surface step of a vehicle is used as a trigger for causing a driver to perform a steering operation. That is, the above “predetermined timing” is a timing related to the passage of the road surface step of the vehicle.

  FIG. 20 is a flowchart showing a specific example of the process for obtaining human impedance including disturbance impedance (step S202 in FIG. 8) in the present embodiment, and is a flowchart instead of FIG.

  First, in step S701, a road surface step is detected based on the output of the road surface sensor 74. For example, when the output of the road surface sensor 74 exceeds a predetermined value, it is determined as a road surface step. It is determined whether or not it is within a predetermined time after the road surface step is detected, and only when it is determined that it is within the predetermined time after the road surface step is detected, the processing after step S702 is executed. Exit this flow.

  As the road surface steps pass, the steering wheel 2 receives a kickback. It is thought that the driver performs steering operation in response to this kickback. Therefore, in step S702, the output of the steering angle sensor 3 and the output of the steering torque sensor 71 when the road surface step is passed are detected.

  Next, in step S703, it is determined whether an estimation prohibition condition as shown below is satisfied.

Estimated prohibition conditions:
Satisfy at least one of the following (a) and (b).
(A) The pulse value detected by the pulse sensor 76 exceeds a predetermined value, and it is determined that the driver's tension is high.
(B) The road surface μ detected by the road surface sensor 74 is lower than a predetermined value.

  If the above condition is satisfied, it is determined that the human impedance cannot be stably estimated, and this flow is exited.

  On the other hand, if the above condition is not satisfied, the process proceeds to step S704, and the stiffness coefficient K1, the viscosity coefficient B1, and the inertia coefficient M1 are calculated in the same manner as in step S2024 as described above.

  Thus, according to the present embodiment, the kickback associated with the passage of the road surface step of the vehicle can be used as a trigger for causing the driver to perform a steering operation. Therefore, in this case, a separate process such as forcibly rotating the steering wheel as a trigger for causing the driver to perform the steering operation is unnecessary. Thereby, the operation amount of the steering operation of the driver can be measured with a simple configuration.

(Embodiment 8)
The eighth embodiment is a variation of the above-described seventh embodiment.

  FIG. 21 is a flowchart showing a specific example of the process for obtaining human impedance including disturbance impedance (step S202 in FIG. 8) in the present embodiment. The difference from FIG. 20 is that step S711 is replaced with step S711. This is the point at which judgment processing is performed. Since the subsequent processing steps are the same as those in FIG. 20, they are denoted by the same reference numerals and description thereof is omitted.

  In step S711, it is determined whether the output of the steering torque sensor 71 has changed more than a predetermined value within a predetermined time, or whether the output of the steering angle sensor 3 has changed more than a predetermined value within a predetermined time. When this determination condition is satisfied, step S702 and subsequent steps are executed.

  The determination content of step S711 is that even if the steering with the same steering force characteristic is rotated, the steering behavior (that is, the steering behavior) is different due to the difference in the driver's human impedance characteristic (see (a) and (b) of FIG. 22). This is based on the fact that drivers A and B are referred to.).

  According to the eighth embodiment, the influence of disturbance on the operation amount of the steering operation can be reduced (that is, the S / N is improved). Therefore, the human impedance can be estimated with high accuracy.

(Embodiment 9)
In the ninth embodiment, the measurement signal as described in the second embodiment is superimposed on the original steering characteristic P by superimposing the measurement signal characteristic on the portion at a predetermined angle, as shown in FIG. generate.

  FIG. 23 is a flowchart showing a specific example of the process for obtaining the human impedance including the disturbance impedance (step S202 in FIG. 8) in the present embodiment, and is an alternative flowchart of FIG.

  First, in step S721, the steering wheel 2 is at a predetermined steering angle and a predetermined torque by determining whether the output of the steering angle sensor 3 is a predetermined value or whether the steering torque sensor is a predetermined value. Determine whether. When this condition is satisfied, the processing after step S722 is executed.

  In step S722, as described above, the characteristics of the measurement signal are superimposed on the original steering characteristics in a predetermined angle range. When this is seen by the relationship between time and a rudder angle, it represents as (b) of FIG. As shown in the figure, the protruding portion in the predetermined angle range shows the measurement signal.

  Next, in step S723, the output of the steering angle sensor 3 and the output of the steering torque sensor 71 are detected (see (c) and (d) of FIG. 24).

  Next, in step S724, the steering angle sensor output waveform and the steering torque sensor output waveform obtained in step S723 are respectively input to the bandpass filter (BPF). As a result, the steering angle sensor output and the steering torque sensor output corresponding to the measurement signal are extracted (see FIGS. 24E and 24F).

  Thereafter, similarly to FIG. 9, step S2023 (estimation prohibition determination) and step S2024 (coefficient calculation) are executed.

  According to the above processing, the characteristic of the measurement signal superimposed and input in step S722 becomes a trigger for causing the driver to perform the steering operation. Therefore, the operation amount of the steering operation of the driver can be reliably measured.

It is a figure which shows schematic structure of the steering device in Embodiment 1. FIG. FIG. 2 is a block diagram illustrating a configuration of a control unit in the first embodiment. 3 is a flowchart showing a steering reaction force control process in the first embodiment. 6 is a diagram illustrating an example of a data structure of a human impedance calculation LUT according to the first embodiment. FIG. It is a flowchart which shows an example of the steering reaction force change process in embodiment. It is a figure which shows schematic structure of the steering device which concerns on the modification of Embodiment 1. FIG. It is a figure which shows schematic structure of the steering device in Embodiment 2. FIG. 6 is a flowchart illustrating a steering reaction force control process according to the second embodiment. 10 is a flowchart illustrating a specific example of processing for obtaining human impedance including disturbance impedance in the second embodiment. It is a figure which shows the example of the measurement signal in Embodiment 2, a steering angle sensor output, and a steering torque sensor output. 10 is a flowchart illustrating an example of a calculation procedure of a stiffness coefficient, a viscosity coefficient, and an inertia coefficient in the second embodiment. FIG. 10 is a schematic diagram for explaining a calculation procedure of a stiffness coefficient, a viscosity coefficient, and an inertia coefficient in the second embodiment. FIG. 10 is a schematic diagram for explaining a calculation procedure of a stiffness coefficient, a viscosity coefficient, and an inertia coefficient in the second embodiment. 10 is a flowchart illustrating a specific example of processing for obtaining disturbance impedance in the second embodiment. 10 is a flowchart illustrating a specific example of processing for obtaining human impedance from which an influence of disturbance is removed in the second embodiment. It is a figure which shows the example of the measurement signal based on Embodiment 4, a steering angle sensor output, and a steering torque sensor output. It is a figure which shows the example of the measurement signal based on Embodiment 5, a steering angle sensor output, and a steering torque sensor output. It is a figure which shows an example of the envelope of the frequency spectrum of the steering angle sensor output signal in Embodiment 5. It is a figure which shows the example of the measurement signal based on Embodiment 6, a steering angle sensor output, and a steering torque sensor output. 18 is a flowchart illustrating a specific example of processing for obtaining human impedance including disturbance impedance in the seventh embodiment. 16 is a flowchart illustrating a specific example of processing for obtaining human impedance including disturbance impedance in the eighth embodiment. It is a figure explaining that the steering behavior which is different for every driver differs. 20 is a flowchart illustrating a specific example of processing for obtaining human impedance including disturbance impedance in the ninth embodiment. It is a figure explaining the process which calculates | requires the human impedance containing the disturbance impedance in Embodiment 9. FIG.

1: Steering device 2: Steering wheel 3: Steering angle sensor 4: Steering reaction force generating motor 6: Tire 9: Steering rod 10: Steering motor 11: Control unit 71: Steering torque sensor 72: Pressure sensor 73: Electrostatic sensor

Claims (4)

A steering wheel,
Detecting means for detecting an operation amount of a steering operation on the steering wheel of a driver made at a predetermined timing;
Estimating means for estimating the mechanical impedance of the driver based on the operation amount detected by the detecting means;
Control means for controlling a steering reaction force of the steering wheel based on the mechanical impedance estimated by the estimation means;
Road surface step detecting means for detecting a road surface step,
The vehicle steering apparatus according to claim 1, wherein the predetermined timing is within a predetermined period when a road surface level difference is detected by the road level level detection means . A torque sensor for detecting rotational torque of the steering wheel;
A steering angle sensor for detecting a steering angle of the steering wheel;
Further comprising
The vehicle steering apparatus according to claim 1, wherein the estimating unit estimates the mechanical impedance based on outputs of the torque sensor and the steering angle sensor.   The predetermined timing is when the output of the torque sensor changes more than a predetermined value within a predetermined time, or when the output of the rudder angle sensor changes more than a predetermined value within a predetermined time. The vehicle steering apparatus according to claim 2.   The detection means superimposes and inputs a characteristic signal for measuring the mechanical impedance to a steering characteristic, and detects an operation amount of a driver's steering operation with respect to rotation of the steering wheel based on the steering characteristic on which the characteristic signal is superimposed. The vehicle steering apparatus according to claim 1, wherein:

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