JP4231428B2 - Vehicle steering device - Google Patents

Description

  The present invention includes a steering handle that is operated by a driver to steer a vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, and a steering actuator for turning steered wheels. The present invention also relates to a steering-by-wire vehicle steering apparatus including a steering control device that drives and controls a steering actuator in accordance with an operation of a steering handle to steer a steered wheel.

In recent years, the development of steering devices that employ this type of steering-by-wire system has been actively carried out. For example, Patent Document 1 below detects a steering angle and a vehicle speed, calculates a transmission ratio that decreases as the steering angle increases and increases as the vehicle speed increases, and divides the steering angle by this transmission ratio, thereby dividing the front wheel A steering device is shown in which a turning angle (amount of rack shaft displacement) is calculated and the front wheels are turned to the calculated turning angle. Further, in this steering device, the steering response and followability of the front wheels are improved by correcting the calculated turning angle in accordance with the steering speed obtained by time-differentiating the detected steering angle. Further, by calculating the target yaw rate using the detected vehicle speed and the detected steering angle, and correcting the calculated turning angle according to the difference between the calculated target yaw rate and the detected actual yaw rate, the vehicle behavior state Steering control that takes into account is realized.
JP 2000-85604 A

Further, in Patent Document 2 below, the steering torque and the steering angle of the steering wheel are detected, two turning angles that increase as the steering torque and the steering wheel steering angle increase are calculated, and these calculated turning angles are added. A steering device is shown in which the front wheels are steered at the steered angle. In this steering apparatus, the vehicle speed is also detected, the both turning angles are corrected based on the detected vehicle speed, and the turning characteristics are changed according to the vehicle speed.
Japanese Patent Laid-Open No. 11-124047

  However, in any of the above-described conventional devices, the steering angle and the steering torque, which are the operation input values for the steering wheel by the driver for steering the vehicle, are detected, and the front wheels are detected using the detected steering angle and steering torque. The steering angle is directly calculated, and the front wheels are steered to the calculated steering angle. However, although the steering control of these front wheels has removed the mechanical connection between the conventional steering wheel and the steered wheels, the response of the steering of the front wheels to the operation of the steering wheel is the operation position of the steering wheel. Alternatively, the basic technical idea of determining the front wheel turning angle according to the operating force is exactly the same, and in these turning methods, the front wheel turning angle is determined according to human sensory characteristics. It was difficult to drive the vehicle.

  That is, in the above-described conventional device, the turning angle that cannot be perceived by the driver is determined directly in response to the operation of the steering wheel, and the vehicle turns by turning the front wheels according to the turning angle. . The driver senses the lateral acceleration, yaw rate, and turning curvature of the vehicle due to the turning of the vehicle by touch or vision, and feeds back to the operation of the steering handle to turn the vehicle in a desired manner. In other words, since the turning angle of the front wheels with respect to the steering wheel operation by the driver is a physical quantity that cannot be perceived by humans, the turning angle that is directly determined by the driver's steering operation is the driver's perception. It was not determined according to the characteristics, and this made it difficult to drive the vehicle.

  Further, in the above-described conventional apparatus, the determined turning angle is corrected according to the difference between the target yaw rate calculated using the detected vehicle speed and the detected steering wheel angle, and the detected actual yaw rate. This is merely correction of the turning angle in consideration of the behavior state of the vehicle, and does not determine the turning angle according to the yaw rate that the driver will perceive by operating the steering wheel. Accordingly, in this case as well, the turning angle determined for the driver's steering operation is not determined in accordance with the driver's perceptual characteristics, making it difficult to drive the vehicle.

Patent Document 3 below discloses a vehicle steering assist device that performs appropriate steering support by determining the driver's arousal level, that is, the driver's sleepiness. The vehicle steering assist device determines the driver's arousal level when determining that the vehicle is traveling substantially straight based on a photographed image by a CCD (Charge Coupled Device) camera mounted on the vehicle or a detection value of the yaw angle sensor. In addition to calculating the center frequency fo for steering, the center frequency f for the current steering is calculated. Then, the arousal level is estimated based on the difference between the calculated center frequency fo and center frequency f. As described above, when it is determined that the estimated wakefulness is not sufficient for driving operation (low wakefulness), the steering actuator applies rotational torque to the steering wheel (steering handle), and the vehicle travels safely in the lane. It is designed to assist the driver's steering.
JP 2001-151137 A

  In the conventional vehicle steering assist device, the arousal level is estimated from the difference value between the center frequency fo calculated based on the output of the CCD camera or the yaw angle sensor and the current center frequency f. However, by estimating the arousal level in this way, even if the driver's arousal level is sufficient for driving operation (a high level of arousal level), rotational torque is applied to the steering wheel against the driver's intention. May be granted. That is, when the driver steers the steering wheel at the center frequency f in order to avoid obstacles existing on the road in a state of high arousal level, based on the difference value from the calculated center frequency fo It is estimated that the arousal level is low, and a rotational torque is automatically applied to the steering wheel. In this case, since the rotational torque is applied to the steering wheel against the driver's intention, the driver may feel uncomfortable.

  Further, in the conventional vehicle steering assist device, although the driver's arousal level can be determined based on the output from the CCD camera or yaw angle sensor separately mounted on the vehicle, the expensive CCD camera or yaw angle can be determined. There are problems such as an increase in vehicle manufacturing costs due to the mounting of sensors and a complicated system for controlling these devices and sensors. Therefore, by using other devices and sensors already installed in the vehicle, the vehicle manufacturing cost can be reduced and the control system can be simplified. It is desired to reliably detect the operation state.

  In order to cope with the above problem, the present inventors have worked on research on a vehicle steering apparatus that can steer a vehicle in accordance with human perceptual characteristics in response to a steering wheel operation by a driver. Regarding such human perception characteristics, according to Weber-Fechner's law, it is said that the human sensory quantity is proportional to the logarithm of the physical quantity of the given stimulus. In other words, if the physical quantity of a stimulus given to a human is changed exponentially when the manipulated variable is a displacement, and if the manipulated variable is a torque, the physical quantity of the stimulus given to the human is changed exponentially. And the physical quantity can be matched to human perceptual characteristics. The present inventors have applied the Weber-Hefner's law to a vehicle steering system and discovered the following.

  When driving a vehicle, the vehicle turns by operating the steering handle, and the vehicle's motion state quantities such as lateral acceleration, yaw rate, and turning curvature change as the vehicle turns, and the driver senses the motion state quantity of the vehicle. And it feels more visually. Therefore, if the amount of motion state of the vehicle that can be perceived by the driver is changed exponentially or exponentially with respect to the driver's operation on the steering wheel, the driver's operation on the steering wheel can be reduced. Thus, the vehicle can be driven according to the driver's perceptual characteristics.

  An object of the present invention is to reliably detect a driver's driving operation state with a simplified configuration and warn of deterioration of the state, and based on the above discovery, human perception characteristics with respect to the steering wheel operation by the driver It is an object of the present invention to provide a vehicle steering apparatus that makes driving of a vehicle easy by steering the vehicle in accordance with the above.

In order to achieve the above object, the features of the present invention include a steering handle operated by a driver to steer a vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, A steering-by-wire type vehicle having a steering actuator for turning a steered wheel and a steered control device that drives and controls the steered actuator according to an operation of the steering handle to steer the steered wheel. in rudder device, the an operation force sensor that detects the operation force of the driver against the steering wheel, and the minute operation force detecting means for detecting a minute operation force exerted on the steering wheel by using the detected operation force the was the a predetermined allowable value calculated by multiplying the predetermined Weber ratio and the detected operation force with respect to the operation force for steering wheel detection fine And operation detection means for detecting a change in the driving operation state of the driver by comparing the Do operating force, the driver in accordance with the driving operation state of the driver detected by the operation detection means And a warning notification means for notifying the warning. In this case, before Symbol operation detection means may detect changes in the driving operation state of the driver by the detected small operating force to determine whether greater than a predetermined allowable operating force . In this case, vehicle speed detection means for detecting the vehicle speed of the vehicle is further provided, and the driver state detection means operates when the vehicle speed detected by the vehicle speed detection means is greater than a predetermined vehicle speed. It is preferable to detect a change in the operation state.

According to these, by using an operation force sensor (for example, a steering torque sensor) of a steering wheel that is generally used by other devices mounted on the vehicle, a minute operation amount (operation force of the driver) ) Can be detected. Then, based on a comparison between a minute operating force detected by the operating force sensor and a predetermined allowable value calculated by multiplying a predetermined Weber ratio with respect to the operating force on the steering wheel and the detected operating force. The change in the driving operation state of the driver (particularly, the deterioration of the driving operation state) can be detected. Here, the predetermined permissible value is a permissible value for detecting deterioration of the driving operation state (for example, driving posture or arousal level) of the driver, including a characteristic value related to a human operation amount, for example, driving can be determine based on small operating force is measured when the driving operation state of the user is degraded. Further, when detecting the driving operation state of the driver, according to the magnitude of the vehicle speed detected by the vehicle speed detecting means (for example, a vehicle speed sensor), specifically, when the detected vehicle speed is higher than a predetermined vehicle speed. In addition, the driving operation state of the driver can be detected. Thereby, especially in a high-speed traveling state where a favorable driving operation state of the driver is required, it is possible to detect a change in the driving operation state of the driver with priority. When the driving state of the driver changes (especially deteriorates), the driver can be appropriately warned by warning notification means (for example, vibration of the steering wheel or warning sound).

  Thus, by using a general-purpose operating force sensor and vehicle speed detection means that are also used by other devices mounted on the vehicle, it is not necessary to mount an expensive device on the vehicle, and the manufacturing cost of the vehicle increases. Can be prevented, and a change in the driving operation state of the driver can be reliably detected. Further, since no separate device is mounted on the vehicle, it is not necessary to construct a separate control system in the vehicle, and the entire vehicle system can be simplified.

Another feature of the present invention is that the steering control device represents a vehicle motion state quantity that can be perceived by a driver in relation to turning of the vehicle, and a predetermined Weber related to the motion state quantity is determined. The expected motion state quantity of the vehicle, which is defined as a power function of the operation force with an index obtained by dividing the ratio by the predetermined Weber ratio related to the operation force , is the operation force detected by the operation force sensor. Using the calculated expected motion state quantity, the motion state quantity calculating means for calculating using the calculated expected motion state quantity, and the turning angle of the steered wheel necessary for the vehicle to move with the calculated expected motion state quantity a steering angle calculating means, to the steered wheels by controlling the steering actuator according to the turning angle that is the calculated constituted by the steering control means for steering the steering angle which is the calculated There is also. In this case, the pre-Symbol anticipated motion state quantity, the lateral acceleration of the vehicle, may is one of a yaw rate and turning curvature.

According to these, first, the driver's operating force with respect to the steering wheel represents the amount of motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle, and a predetermined Weber ratio relating to the motion state amount. Is converted into a predicted motion state quantity (lateral acceleration, yaw rate, turning curvature, etc.) of the vehicle defined as a power function of the operation force with an index obtained by dividing the value by a predetermined Weber ratio relating to the operation force . Then, based on the converted expected motion state quantity, the turning angle of the steered wheel necessary for the vehicle to move with the expected motion state quantity is calculated, and the steered wheel is added to the calculated turning angle. Steered. Therefore, when the vehicle turns by turning the steered wheels, the driver is given the expected motion state quantity as the “physical quantity of the applied stimulus” according to the Weber-Hefner law. Then, the anticipated motion state quantity, since it is intended to change in the base Ki-th power relationship to the operation force of the steering wheel, the driver, while perceiving the motion state quantity that matches the human perception characteristics, steering The handle can be operated. The lateral acceleration and yaw rate can be sensed tactilely by the driver in contact with each part in the vehicle. Further, the turning curvature can be visually perceived by the driver due to changes in the situation within the field of view of the vehicle. As a result, according to the present invention, the driver can operate the steering wheel in accordance with human perceptual characteristics, so that driving of the vehicle is simplified.

  Hereinafter, a vehicle steering apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a vehicle steering apparatus according to this embodiment.

  The steering apparatus includes a steering handle 11 as an operation unit that is turned by a driver to steer left and right front wheels FW1 and FW2 as steered wheels. The steering handle 11 is fixed to the upper end of the steering input shaft 12, and the lower end of the steering input shaft 12 is connected to a reaction force actuator 13 including an electric motor and a speed reduction mechanism. The reaction force actuator 13 applies a reaction force to the turning operation of the steering handle 11 by the driver.

  In addition, the steering device includes a steering actuator 21 including an electric motor and a speed reduction mechanism. The turning force by the turning actuator 21 is transmitted to the left and right front wheels FW1 and FW2 via the turning output shaft 22, the pinion gear 23, and the rack bar 24. With this configuration, the rotational force from the steering actuator 21 is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the rotation of the pinion gear 23. Due to the displacement in the axial direction, the left and right front wheels FW1, FW2 are steered left and right.

  Next, an electric control device that controls the operation of the reaction force actuator 13 and the steering actuator 21 will be described. The electric control device includes a steering angle sensor 31, a turning angle sensor 32, a vehicle speed sensor 33, and a lateral acceleration sensor 34.

  The steering angle sensor 31 is assembled to the steering input shaft 12, detects the rotation angle from the neutral position of the steering handle 11, and outputs it as the steering angle θ. The steered angle sensor 32 is assembled to the steered output shaft 22, detects the rotational angle from the neutral position of the steered output shaft 22, and corresponds to the actual steered angle δ (the steered angle of the left and right front wheels FW1, FW2). ). Note that the steering angle θ and the actual turning angle δ are represented by setting the neutral position to “0”, the left rotation angle as a positive value, and the right rotation angle as a negative value. The vehicle speed sensor 33 detects and outputs the vehicle speed V. The lateral acceleration sensor 34 detects and outputs the actual lateral acceleration G of the vehicle. The actual lateral acceleration G also represents leftward acceleration as positive and rightward acceleration as negative.

  These sensors 31 to 34 are connected to the electronic control unit 35. The electronic control unit 35 includes a microcomputer including a CPU, a ROM, a RAM, and the like as main components, and controls the operations of the reaction force actuator 13 and the turning actuator 21 by executing a program. The ROM stores an abnormality notification program described later in advance, and the electronic control unit 35 (specifically, the CPU) executes each step of the program to change the driving operation state of the driver, that is, the driving posture. The driver is alerted to the driver by detecting the deterioration of the vehicle or the decrease in the arousal level. Drive circuits 36 and 37 for driving the reaction force actuator 13 and the steering actuator 21 are connected to the output side of the electronic control unit 35, respectively. In the drive circuits 36 and 37, current detectors 36a and 37a for detecting a drive current flowing through the electric motor in the reaction force actuator 13 and the steering actuator 21 are provided. The drive current detected by the current detectors 36a and 37a is fed back to the electronic control unit 35 in order to control the drive of both electric motors.

  A steering torque sensor 38 is also connected to the electronic control unit 35. The steering torque sensor 38 is assembled to the steering input shaft 12 and detects a steering torque T applied to the steering handle 11, particularly a minute steering torque change (a fine adjustment amount of steering torque) accompanying the steering of the driver. Output.

  Next, regarding the steering device of the present embodiment configured as described above, first, regarding the steering operation of the device, the function block of FIG. 2 representing functions realized by computer program processing in the electronic control unit 35. This will be described with reference to the drawings. The electronic control unit 35 includes a reaction force control unit 40 for controlling the reaction force applied to the steering handle 11, and the left and right front wheels FW1 and FW2 corresponding to the driver's sensory characteristics based on the turning operation of the steering handle 11. It comprises a sensory adaptation control unit 50 for determining the target turning angle δd and a steering control unit 60 for controlling the left and right front wheels FW1, FW2 based on the target turning angle δd.

When the steering handle 11 is turned by the driver, the steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering handle 11, and uses the detected steering angle θ as the reaction force control unit 40 and the sense. Each is output to the matching control unit 50. In the reaction force control unit 40, the displacement-torque conversion unit 41 calculates a reaction force torque Tz that is an exponential function of the steering angle θ by using the following equation (1).
Tz ＝ To ・ exp (K1 ・ θ)… Formula 1
However, To and K1 in the formula 1 are constants, and these values will be described in detail when the sensory adaptation control unit 50 described later is described. Further, the steering angle θ in the equation 1 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant To is set to a negative value, and the detected steering angle θ is If negative, the constant To is a positive value having the same absolute value as the negative constant To. Here, it is also possible to calculate the reaction force torque Tz using a conversion table having characteristics as shown in FIG. 3 in which the reaction force torque Tz with respect to the steering angle θ is stored, instead of the calculation of the equation (1).

  The calculated reaction force torque Tz is supplied to the drive control unit 42. The drive control unit 42 inputs a drive current flowing from the drive circuit 36 to the electric motor in the reaction force actuator 13 and feedback-controls the drive circuit 36 so that a drive current corresponding to the reaction force torque Tz flows through the electric motor. . By the drive control of the electric motor in the reaction force actuator 13, the electric motor applies a reaction force torque Tz to the steering handle 11 via the steering input shaft 12. Therefore, the driver feels the reaction force torque Tz that changes exponentially with respect to the steering angle θ, in other words, while applying a steering torque equal to the reaction force torque Tz to the steering handle 11, It will rotate. The relationship between the steering angle θ and the reaction torque Tz also follows the above-mentioned Weber-Hefner law, and the driver rotates the steering handle 11 while receiving a sense from the steering handle 11 that matches human perception characteristics. Can be operated.

On the other hand, with respect to the steering angle θ input to the sensory adaptation control unit 50, the displacement-torque conversion unit 51 calculates the steering torque Td according to the following equation 2 similar to the equation 1.
Td ＝ To ・ exp (K1 ・ θ)… Formula 2
Also in this case, To and K1 in the formula 2 are constants similar to those in the formula 1. However, the steering angle θ in Equation 2 represents the absolute value of the detected steering angle θ. If the detected steering angle θ is positive, the constant To is set to a positive value, and the detected steering angle is If θ is negative, the constant To is a negative value having the same absolute value as the positive constant To. Here, in this case as well, the steering torque Td may be calculated using a conversion table having characteristics as shown in FIG. 3 in which the steering torque Td with respect to the steering angle θ is stored, instead of the calculation of the expression 2. Good.

The calculated steering torque Td is supplied to the torque-lateral acceleration conversion unit 52. If the absolute value of the steering torque Td is less than a predetermined positive value To, the torque-lateral acceleration conversion unit 52 calculates the expected lateral acceleration Gd that the driver expects by turning the steering wheel 11 as follows: Thus, when the absolute value of the steering torque Td is not less than a predetermined positive value To, the expected lateral acceleration Gd, which is a power function of the steering torque Td, is calculated according to the following equation 4.
Gd = 0 (| Td | <To)… Formula 3
Gd = C · Td ^K2 (To ≦ | Td |) Equation 4
However, C and K2 in Formula 4 are constants. Further, the steering torque Td in the equation 4 represents the absolute value of the steering torque Td calculated using the equation 2, and if the calculated steering torque Td is positive, the constant C is a positive value. If the calculated steering torque Td is negative, the constant C is set to a negative value having the same absolute value as the positive constant C. In this case as well, the steering torque Td is calculated by using a conversion table having characteristics as shown in FIG. 4 in which the expected lateral acceleration Gd with respect to the steering torque Td is stored instead of the calculations of the expressions 3 and 4. May be.

Here, Formula 4 will be described. When the steering torque Td is eliminated using the above equation 2, the following equation 5 is obtained.
Gd = C (To · exp (K1 · θ)) ^K2 = C · To ^K2 · exp (K1, K2 · θ) = Go · exp (K1, K2 · θ)
In Equation 5, Go is a constant C · To ^K2 , and Equation 5 indicates that the expected lateral acceleration Gd varies exponentially with respect to the steering angle θ of the steering wheel 11 by the driver. The expected lateral acceleration Gd is a physical quantity that can be perceived by the driver due to the contact of a part of the driver's body with a predetermined part in the vehicle, and follows the aforementioned Weber-Hefner law. Therefore, if the driver can turn the steering handle 11 while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the relationship between the turning operation of the steering handle 11 and the steering of the vehicle can be expressed by human perception characteristics. It can be made to correspond.

As described above, the expected lateral acceleration Gd shown in the equation 4 (that is, the equation 5) changes exponentially with respect to the steering angle θ, which is the operation amount of the steering wheel 11, and thus the human perception specification is performed. It is suitable for. Further, the simplest method for the turning operation of the steering handle 11 by the driver is to turn the steering handle 11 at a constant speed ω (θ = ω · t). The acceleration Gd changes exponentially with respect to time t as shown in the following equation (6). Therefore, it will be understood that if the steering handle 11 can be rotated while perceiving a lateral acceleration equal to the expected lateral acceleration Gd, the driver can easily rotate the steering handle 11.
Gd = Go · exp (K0 · ω · t) ... Equation 6
However, K0 is a constant having a relationship of K0 = K1 · K2.

Further, as shown in Equation 3, when the steering torque Td is less than the predetermined value To, the expected lateral acceleration Gd is kept at “0”. This is because, even when the steering angle θ is “0”, that is, when the steering wheel 11 is kept at the neutral position, the steering torque Td becomes a positive predetermined value To by the calculation of the above equation 2, and this steering torque Td If (= To) is applied to the calculation of Equation 4, the expected lateral acceleration Gd becomes a positive value C · To ^K2 , which is not realistic. However, as described above, if the steering torque Td is less than the predetermined value To, the expected lateral acceleration Gd is “0”, so this problem is solved.

In this case, the minimum steering torque that can be perceived by the driver is the predetermined value To, the minimum perceived lateral acceleration that the driver can perceive is Go, and the predetermined value To has a relationship of Go = C · To ^K2. By doing so, the expected lateral acceleration Gd of the vehicle until the steering torque Td reaches a predetermined value To, that is, until the driver feels the lateral acceleration generated in the vehicle by turning the vehicle by operating the steering handle 11. Is kept at “0”. According to this, only when the steering handle 11 is steered at the minimum steering torque To or more, the left and right front wheels FW1, FW2 are steered by the steered angle required to generate the expected lateral acceleration Gd. Will correspond exactly to the steering of the vehicle.

  Next, how to determine the parameters K1, K2, and C (predetermined values K1, K2, and C) used in the expressions 1 to 6 will be described. In the description of how to determine the parameters K1, K2, and C, the steering torque Td and the expected lateral acceleration Gd in the expressions 2 to 6 are handled as the steering torque T and the lateral acceleration G. According to the aforementioned Weber-Hefner law, “the ratio ΔS / S between the minimum physical quantity change ΔS perceivable by humans and the physical quantity S at that time is constant regardless of the value of the physical quantity S, and the ratio ΔS / S is called the Weber ratio. The present inventors confirmed that the above-mentioned Weber-Hefner's law is established with respect to steering torque and lateral acceleration, and in order to determine the Weber ratio, the following experiments were conducted for men and women, age, and vehicle driving. I went to various people with different histories.

  Regarding the steering torque, a torque sensor is assembled to the steering handle of the vehicle, a test torque is applied to the steering handle from the outside, and the test torque is changed in various manners, and a human being resists this test torque. Measured the human's ability to adjust the steering torque to adjust the steering handle so that it does not rotate by applying an operating force to the steering handle. That is, in the above situation, when the detected operation torque at a certain time is T, and the minimum steering torque change amount that can be perceived as a change from the detected steering torque T is ΔT, the ratio value ΔT / T, that is, Weber The ratio was measured for various humans (subjects). According to this experimental result, the Weber ratio ΔT / T was approximately constant 0.03 regardless of the operation direction of the steering wheel, the state of the hand holding the steering wheel, and the magnitude and direction of the inspection torque. . Here, the measurement of the Weber ratio was performed in a state in which the subject is most likely to steer and maintains a good driving posture and the arousal level at that time is high.

  Regarding the lateral acceleration, a wall member is provided on the side of the driver's seat, and a force sensor for detecting the pressing force of the human shoulder is assembled to the wall member. The wall member is made to contact the wall member against the inspection force while applying the inspection force to the wall member from the outside in the lateral direction and changing the inspection force in various modes. It was adjusted so that the wall member does not move by pushing, that is, the human side force adjustment ability to maintain the posture was measured. That is, in the above situation, when F is the detection force that can withstand lateral force from outside at a certain time and maintain the driving posture, and the minimum force change amount ΔF that can perceive the change from the detection force F The ratio value ΔF / F, that is, the Weber ratio was measured for various humans (subjects). According to the results of this experiment, the Weber ratio ΔF / F was a substantially constant value of about 0.09 regardless of the magnitude and direction of the reference force applied to the wall member.

On the other hand, when the formula 2 is differentiated and the formula 2 is considered in the differentiated formula, the following formula 7 is established.
ΔT ＝ To ・ exp (K1 ・ θ) ・ K1 ・ Δθ = T ・ K1 ・ Δθ
When the equation 7 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is Kt, the following equation 8 is established.
K1 = ΔT / (T · Δθ) = Kt / Δθ Equation 8

If the maximum steering torque is Tmax, the following formula 9 is established from the above formula 2.
Tmax ＝ To ・ exp (K1 ・ θmax) ... Equation 9
If Equation 9 is modified, the following Equation 10 is established.
K1 = log (Tmax / To) / θmax Equation 10
Then, the following formula 11 is derived from the formula 8 and the formula 10.
Δθ = Kt / K1 = Kt · θmax / log (Tmax / To) (Formula 11)
In Equation 11, Kt is the Weber ratio of the steering torque T, θmax is the maximum value of the steering angle, Tmax is the maximum value of the steering torque, and To is the minimum steering torque that can be perceived by humans as described above. Since these values Kt, θmax, Tmax, and To are constants determined by experiments and systems, the differential value Δθ can be calculated using the equation (11). Then, a predetermined value (coefficient) K1 can also be calculated based on Equation 8 using the differential value Δθ using the Weber ratio Kt.

In addition, when the expression 4 is differentiated and the expression 4 is considered in the differentiated expression, the following expression 12 is established.
ΔG = C ・ K2 ・ T ^K2-1 ΔT = G ・ K2 ・ ΔT / T
When Expression 12 is modified and the Weber ratio ΔT / T related to the steering torque obtained by the experiment is set to Kt and the Weber ratio ΔF / F related to the lateral acceleration is set to Ka, the following Expressions 13 and 14 are established.
ΔG / G = K2 · ΔT / T Equation 13
K2 = Ka / Kt ... Formula 14
In this equation 14, Kt is the Weber ratio related to the steering torque, and Ka is the Weber ratio related to the lateral acceleration, both of which are given as constants. Therefore, using these Weber ratios Kt and Ka, the above equation is used. 14 can also calculate the coefficient K2.

If the maximum value of the lateral acceleration is Gmax and the maximum value of the steering torque is Tmax, the following equation 15 is derived from the equation 4.
C = Gmax / Tmax ^K2 Equation 15
In Equation 15, Gmax and Tmax are constants determined by experiments and systems, and K2 is calculated by Equation 14, so that a constant (coefficient) C can also be calculated.

  As described above, the maximum value θmax of the steering angle θ, the maximum value Tmax of the steering torque T, the maximum value Gmax of the lateral acceleration G, the minimum steering torque To, the minimum sensed lateral acceleration Go, the Weber ratio Kt and the lateral acceleration relating to the steering torque T. If the Weber ratio Ka is determined by experiment and system, the coefficients K1, K2, and C in the equations 1 to 5 can be determined in advance by calculation. Accordingly, in the displacement-torque conversion units 41 and 51 and the torque-lateral acceleration conversion unit 52, the reaction force torque Tz, the steering torque Td, and the expected lateral acceleration that match the driver's perceptual characteristics are obtained using the equations 1-5. Gd can be calculated.

  Returning to the description of FIG. 2 again, the expected lateral acceleration Gd calculated by the torque-lateral acceleration conversion unit 52 is supplied to the turning angle conversion unit 53. The turning angle conversion unit 53 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected lateral acceleration Gd, and changes according to the vehicle speed V as shown in FIG. And a table representing a change characteristic of the target turning angle δd with respect to the expected lateral acceleration Gd. This table is a set of data collected by running the vehicle while changing the vehicle speed V and actually measuring the turning angle δ and the lateral acceleration G of the left and right front wheels FW1, FW2. Then, the turning angle conversion unit 53 refers to this table and calculates a target turning angle δd corresponding to the input expected lateral acceleration Gd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the lateral acceleration G (expected lateral acceleration Gd) and the target turning angle δd stored in the table are both positive, but the expected lateral acceleration Gd supplied from the turning angle conversion unit 53 is negative. In this case, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the lateral acceleration G as shown in the following formula 16, it can be calculated by executing the calculation of the following formula 16 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · Gd / V ² Equation 16
However, L in the equation 16 is a predetermined value (for example, 2.67 m) indicating the wheel base of the vehicle, and A is a predetermined value (for example, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 61 of the turning control unit 60. The turning angle correction unit 61 receives the expected lateral acceleration Gd from the torque-lateral acceleration conversion unit 52 and also the actual lateral acceleration G detected by the lateral acceleration sensor 34, and calculates the following equation (17). The corrected target turning angle δda is calculated by correcting the inputted target turning angle δd.
δda = δd + K3 · (Gd−G) Equation 17
However, the coefficient K3 is a predetermined positive constant. When the actual lateral acceleration G is less than the expected lateral acceleration Gd, the coefficient K3 is corrected so that the absolute value of the corrected target turning angle δda is increased. . When the actual lateral acceleration G exceeds the expected lateral acceleration Gd, the correction target turning angle δda is corrected to be smaller. By this correction, the target turning angle δd of the left and right front wheels FW1, FW2 necessary for the expected lateral acceleration Gd is ensured with higher accuracy.

  The calculated corrected target turning angle δda is supplied to the drive control unit 62. The drive control unit 62 inputs the actual turning angle δ detected by the turning angle sensor 32, and electrically drives the turning actuator 21 so that the left and right front wheels FW1, FW2 are turned to the corrected target turning angle δda. Feedback control of motor rotation. The drive control unit 62 also receives a drive current that flows from the drive circuit 37 to the electric motor in the steering actuator 21, and drives the electric motor so that a drive current having a magnitude corresponding to the steering torque flows appropriately. The circuit 37 is feedback controlled. By the drive control of the electric motor in the steering actuator 21, the rotation of the electric motor is transmitted to the pinion gear 23 via the steering output shaft 22, and the rack bar 24 is displaced in the axial direction by the pinion gear 23. As the rack bar 24 is displaced in the axial direction, the left and right front wheels FW1 and FW2 are steered to the corrected target turning angle δda.

  Next, in the state where the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda with respect to the steering angle θ input to the steering handle 11 of the driver as described above, the electronic control unit 35 is A warning notification program for determining whether the driver's driving operation state, that is, whether the driving posture is good or not, and whether the driver's driving operation state has deteriorated, and alerting the driver when the driver's driving operation state deteriorates every predetermined short time Repeatedly. Hereinafter, this warning notification program will be described in detail with reference to the flowchart shown in FIG.

  The warning notification program starts executing in step S10 when an ignition switch (not shown) is turned on. In step S11, the electronic control unit 35 determines whether or not the vehicle speed V supplied from the vehicle speed sensor 33 is higher than a predetermined vehicle speed Vokm / h. The predetermined vehicle speed Vo is a threshold value for determining whether or not detection of the driving operation state of the driver is started in step S11, and detection of the driving operation state of the driver in step S20 described later. Is a threshold value for determining whether or not to continue. Then, the electronic control unit 35 repeatedly executes step S11 based on the “No” determination until the vehicle speed V becomes higher than the predetermined vehicle speed Vokm / h, and when the vehicle speed V becomes higher than the predetermined vehicle speed Vokm / h, It determines with "Yes" and progresses to step S12.

  In step S12, the electronic control unit 35 initially sets a count value representing the number of consecutive times that the driver has steered the steering handle 11 when the driving operation state of the driver is poor, that is, the driving posture is deteriorated or the awakening level is low. And set to "0", and the process proceeds to step S13. In step S <b> 13, the electronic control unit 35 calculates a minute change amount ΔTs of the steering torque T based on the steering torque T detected by the steering torque sensor 38. Hereinafter, the calculation of the change amount ΔTs will be described in detail.

  First, it is considered that the time-series data T (t) of the driver's steering torque T when traveling at a higher speed than the predetermined vehicle speed Vo has a tendency as schematically shown in FIG. That is, as shown in FIG. 7A, when the vehicle is traveling at high speed, the driver finely adjusts the steering torque T in the vicinity of a certain steering torque value regardless of whether the vehicle is traveling straight or turning. Try to maintain vehicle attitude. For this reason, the steering torque T is considered to change stepwise. As a result, when the driver intentionally steers, the absolute value of the time variation T ′ (t) of the steering torque T becomes a large value. On the other hand, when the driver does not intentionally steer, the steering torque T is substantially constant, so the absolute value of the time change amount T ′ (t) of the steering torque T is substantially “0”.

  Based on the tendency of the time series data T (t), the electronic control unit 35 calculates the change amount ΔTs of the steering torque T as shown below. More specifically, since the time series data T (t) of the steering torque T supplied from the steering torque sensor 38 is actually discrete data, the electronic control unit 35 can obtain the time series data T (t) as A time change amount of the steering torque T corresponding to the time change amount T ′ (t) is calculated based on a difference from the time series data T (t−1). Next, the absolute value of the difference between the time series data T (t) and the time series data T (t−1) (hereinafter, the absolute value of this difference is referred to as S (t)) is greater than a predetermined determination threshold value h. Is also compared. From this comparison, if S (t) is larger than the predetermined determination threshold value h, S (t) = “1” is set, and if S (t) is smaller than the predetermined determination threshold value h, S (t t) Set to “0”. Then, the steering torque T (t) at time t set to S (t) = “0” is temporarily stored in a RAM (not shown). By repeating such calculation processing at a predetermined short cycle, the difference between the steering torque T (t) stored at the time of the current program execution and the steering torque T (t−1) stored at the time of the previous program execution. From this, the change amount ΔTs can be calculated.

  On the other hand, the inventors of the present invention conducted an experiment to confirm whether or not the driver's intentional steering torque change amount can be detected by calculating the change amount ΔTs. Hereinafter, the result of this confirmation experiment will be described in detail. In this confirmation experiment, the steering wheel of the vehicle is held at a predetermined reference torque (reference torque), the steering wheel is steered with the minimum steering torque change that can be perceived by the driver, and the steering torque changes The steering torque change was measured when the steering torque was reduced to the original reference torque immediately after the perception. If the steering torque change measured by this confirmation experiment is expressed as time-series data, it is as shown in FIG. When the change amount ΔTs of the steering torque T is small with respect to the time series data, that is, only the steering torque T when S (t) = “0” is selected and plotted, FIG. c).

  As shown in FIG. 7C, the steering torque when the driver intentionally steers the steering wheel and the change amount ΔTs of the steering torque T is large, that is, when S (t) = “1” is set. By not selecting T, it is possible to reliably detect the driver's intentional steering wheel steering. In other words, by detecting the steering of the steering wheel in a state where the driver's arousal level is high, the steering of the steering wheel in a state where the driver's arousal level is low can be reliably detected. Thus, every time S (t) is set to “0”, the electronic control unit 35 determines the value of the steering torque T at that time and the steering torque T when S (t) was previously set to “0”. The amount of change ΔTs in a state where the driver's arousal level is low can be calculated by calculating the difference between them as needed. Here, in the calculation of the change amount ΔTs, as shown in FIG. 7C, for example, even when the driver keeps the steering torque T constant, for example, the driver's unconscious hand A change in the steering torque T caused by tremors may be calculated as the change amount ΔTs. This can be eliminated by the determination process in step S14 of the warning notification program described later, so that there is no problem.

  In the above calculation of the change amount ΔTs, in order to calculate the change amount ΔTs more accurately, the sampling period of the steering torque T and the determination threshold value according to the speed of the steering operation of the driver (steering torque speed). It is good to determine h appropriately. Further, since the change amount ΔTs is calculated from the difference of the steering torque T expressed by the digital value after the AD data is converted from the output data (analog value) from the steering torque sensor 38, the LSB (Least Significant Bit: the least significant bit) ) Should be sufficiently small. Further, in order to smooth the time series data T (t) of the steering torque T, an LPF (Low Pass Filter) may be provided. Also by these, a more accurate change amount ΔTs can be calculated.

  Returning to the flowchart of FIG. 6 again, after the change amount ΔTs calculation processing in step S13, in step S14, the electronic control unit 35 determines whether or not the steering wheel 11 is steered by the driver. That is, the electronic control unit 35 determines the steering of the driver's steering wheel 11 by comparing the change amount ΔTs with the threshold obtained by multiplying the Weber ratio Kt related to the steering torque and the current steering torque T. To do.

  More specifically, if the change amount ΔTs is equal to or greater than the threshold value obtained by multiplying the current steering torque T by the Weber ratio, the change amount larger than the minimum steering torque change amount ΔT at which the driver can perceive the change. In this state, the steering handle 11 is being steered by ΔTs. In other words, the driver is in a state of steering the steering wheel 11 with a perceivable steering torque. Therefore, if the change amount ΔTs is equal to or greater than the threshold value, the electronic control unit 35 determines that the driver has steered the steering wheel 11, determines “Yes”, and proceeds to step S15. On the other hand, the change amount ΔTs being smaller than the threshold value is a state where the steering wheel 11 is steered by a steering torque smaller than the minimum steering torque change amount ΔT at which the driver can perceive the change. As described above, when the change amount ΔTs is smaller than the steering torque change amount ΔT, the steering handle 11 is steered by a steering torque that cannot be perceived by the driver, for example, an unconscious hand tremor, and the driver. Is not actively steering the steering wheel 11. Accordingly, the electronic control unit 35 determines that the driver is not steering the steering handle 11, determines “No”, and proceeds to step S20.

  In step S15, the electronic control unit 35 determines whether or not the driving operation state of the driver, that is, the driving posture / wakefulness is deteriorated. That is, the driver's driving operation state is determined by comparing the change amount ΔTs with a predetermined constant k, a Weber ratio Kt, and an allowable value obtained by multiplying the current steering torque T. Here, the predetermined constant k is a constant determined experimentally in advance in order to determine a driver's driving operation state failure.

  More specifically, when the change amount ΔTs is larger than an allowable value obtained by multiplying the predetermined constant k, the Weber ratio Kt, and the current steering torque T, the steering torque in a favorable driving operation state of the driver Compared with T, for example, a state where an excessive steering torque T is applied to the steering handle 11 as the driving posture deteriorates, or an excessive steering torque T is applied to the steering handle 11 unconsciously with a low arousal level. It can be determined that the state is given. Therefore, if the change amount ΔTs is larger than the allowable value, the electronic control unit 35 determines that the driving operation state of the driver is poor, that is, the driving posture is deteriorated or the arousal level is decreased, and “Yes” is determined. Then, the process proceeds to step S16. In step S16, the electronic control unit 35 adds “1” to the count value indicating the continuous number of times that the driver has steered the steering wheel 11 due to a bad state, and proceeds to step S18.

  Here, when the vehicle traveling state changes from a straight traveling state to a turning state, or from a turning state to a straight traveling state, the change amount ΔTs is allowed even if the driver's driving posture is not deteriorated or the arousal level is not lowered. The electronic control unit 35 may determine “Yes” in step S15. However, when changing the traveling state of the vehicle, the steering handle 11 is steered only once or twice immediately after the start of the change in the traveling state when the amount of change ΔTs exceeds the allowable value. Then, after the change in the running state of the vehicle, the steering becomes minute to maintain the traveling direction of the vehicle. For this reason, even when the electronic control unit 35 determines “Yes” in step S15 in accordance with a change in the running state of the vehicle and adds “1” to the count value in step S16, the steps described later are performed. By appropriately setting the continuous frequency threshold value n in S18, it is possible to eliminate warning notifications unnecessary for the driver.

  On the other hand, if the amount of change ΔTs is less than or equal to the allowable value in step S15, the electronic control unit 35 determines that there is no problem in the driving posture and arousal level of the driver, determines “No”, and step S17. Proceed to In step S17, the electronic control unit 35 initializes the count value and sets it to “0”. This is because, in step S15, it is determined that there is no problem in the driver's driving posture and arousal level, for example, the driver's driving posture and the arousal level are defective during the previous program execution. However, the driver's driving posture and arousal level may be corrected during the current program execution. In such a case, it is necessary to initialize the count value to “0”. And the electronic control unit 35 progresses to step S20 after the initialization process of step S17.

  In step S18, the electronic control unit 35 determines whether or not the count value is larger than the continuous count threshold value n. This continuous number of times threshold value n is a value for determining whether or not to warn the driver of the deterioration of the driving posture and the decrease in the arousal level. Needless to say, the continuous number threshold value n can be appropriately changed according to the driving operation state of the driver. If the count value is larger than the continuous number of times threshold value n, the electronic control unit 35 determines “Yes” and proceeds to step S19. On the other hand, if the count value is less than or equal to the threshold value n of continuous times, the electronic control unit 35 determines “No” and proceeds to step S20.

  In step S19, the electronic control unit 35 warns the driver of the deterioration of the driving posture and the decrease in the arousal level. More specifically, the electronic control unit 35 drives the reaction force actuator 13 via the drive circuit 36 to vibrate the steering handle 11 for a predetermined time (or a predetermined number of times). Thus, by vibrating the steering handle 11, the driver can recognize the warning from the electronic control unit 35, and can correct the driving posture and the arousal level. Here, in this embodiment, since the steer-by-wire system is adopted, the traveling direction of the vehicle does not change even if the steering handle 11 is vibrated in the turning direction, for example. In the present embodiment, the steering handle 11 is vibrated so as to notify a warning to the driver. For example, the warning is notified by sound from a speaker (not shown) mounted on the vehicle, It is also possible to notify the warning by vibrating the seat on which the driver is seated. As described above, when the electronic control unit 35 notifies the driver of the warning, the electronic control unit 35 proceeds to step S20.

  In step S20, the electronic control unit 35 determines whether or not the vehicle speed V supplied from the vehicle speed sensor 33 is higher than a predetermined vehicle speed Vkm / h, as in step S11. If the vehicle speed V is greater than the predetermined vehicle speed Vokm / h as a result of this determination, the electronic control unit 35 determines “Yes” and executes the processes after step S13. This is because it is necessary to continue detecting the driving operation state of the driver because the vehicle maintains a high speed traveling state larger than the predetermined vehicle speed Vkm / h. On the other hand, if the vehicle speed V is equal to or lower than the predetermined vehicle speed Vkm / h, the electronic control unit 35 determines “No”, returns to step S11, and continues to “No” until the vehicle speed V becomes higher than the predetermined vehicle speed Vkm / h. Step S11 is repeatedly executed based on the determination. When the vehicle speed V becomes higher than the predetermined vehicle speed Vkm / h, it is determined as “Yes”, and the processes after step S12 are executed.

  As can be understood from the above description of the operation, according to the present embodiment, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque conversion unit 51 and is also converted. The steering torque Td thus converted is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the left and right front wheels FW1, FW2 are estimated laterally by the turning angle conversion unit 53, the turning angle correction unit 61, and the drive control unit 62. The vehicle is steered to the corrected target turning angle δda necessary for generating the acceleration Gd.

  In this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering wheel 11 due to the action of the reaction force actuator 13 and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to human perceptual characteristics while feeling a reaction force according to Weber-Hefner's law. The actual lateral acceleration G generated in the vehicle by turning the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the actual lateral acceleration G is controlled to be equal to the expected lateral acceleration Gd. Further, the expected lateral acceleration Gd also changes exponentially with respect to the steering angle θ input by the driver (exponentially by transforming Equation 4 into Equation 5). Accordingly, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perceptual characteristic while feeling the lateral acceleration according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with human perceptual characteristics, and thus driving of the vehicle is simplified.

  Further, the turning angle correction unit 61 corrects the target turning angle δd so that the actual lateral acceleration G actually generated in the vehicle accurately corresponds to the steering angle θ of the steering handle 11, so that the vehicle An actual lateral acceleration G accurately corresponding to the steering angle θ of the steering handle 11 is generated. As a result, the driver can operate the steering wheel 11 while perceiving the lateral acceleration more accurately according to the human perceptual characteristics, so that the driving of the vehicle becomes easier.

  Further, the electronic control unit 35 detects the steering torque T by using the steering torque sensor 38 of the steering handle 11 that is generally used by other devices mounted on the vehicle, and based on the steering torque T. The minute change amount ΔTs of the steering torque T of the driver can be calculated. If the amount of change ΔTs is greater than the allowable value based on the Weber ratio, it is determined that the driver's driving operation state has deteriorated, that is, the driving posture has deteriorated and the arousal level has decreased, and the driver is warned. Can be notified. Thus, by detecting the deterioration of the driving operation state of the driver using the steering torque sensor 38 also used by other devices mounted on the vehicle, there is no need to mount an expensive device on the vehicle. The increase in the manufacturing cost of the vehicle can be eliminated. Further, since no separate device is mounted on the vehicle, it is not necessary to construct a separate control system in the vehicle, and the entire vehicle system can be simplified.

  Next, a modification of the above embodiment in which the steering torque T is used as the operation input value of the steering handle 11 will be described. In this modification, the displacement-torque converter 51 is not provided in the functional block diagram of FIG. 2 representing the computer program related to the turning operation, and the torque-lateral acceleration converter 52 is the displacement- Instead of the steering torque Td calculated by the torque converter 51, the expected lateral acceleration Gd is calculated by executing the calculations of equations 3 and 4 using the steering torque T detected by the steering torque sensor 38. In this case as well, the expected lateral acceleration Gd may be calculated using a conversion table representing the characteristics shown in FIG. The other program processing executed by the electronic control unit 35 is the same as in the above embodiment.

  According to this modification, the steering torque T as an operation input value of the driver for the steering handle 11 is converted into the expected lateral acceleration Gd by the torque-lateral acceleration conversion unit 52, and the turning angle conversion unit 53, the turning angle correction. By the unit 61 and the drive control unit 62, the left and right front wheels FW1, FW2 are steered to the corrected target turning angle δda necessary for generating the expected lateral acceleration Gd. In this case as well, the steering torque T is a physical quantity that the driver can perceive from the steering handle 11, and the expected lateral acceleration Gd changes in a power function with respect to the steering torque T. The steering handle 11 can be turned according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law. Therefore, in this modification as well, in the same manner as in the above embodiment, the driver turns the steering wheel 11 according to the human perception characteristic while feeling the lateral acceleration according to the Weber-Hefner law, Since it can be made to turn, the effect similar to the said embodiment is anticipated.

  Furthermore, the vehicle steering control according to the above embodiment and the vehicle steering control according to the modification may be switchable. That is, both the steering angle sensor 31 and the steering torque sensor 38 are provided, and the expected lateral acceleration Gd is calculated using the target turning torque Td calculated by the displacement-torque conversion unit 51 as in the above embodiment. It is also possible to switch between the case where the expected lateral acceleration Gd is calculated using the steering torque T detected by the steering torque sensor 38 and to make it usable. In this case, the switching may be performed automatically according to the driver's intention or according to the motion state of the vehicle.

  In addition, the abnormality notification program in the above embodiment is applied to a steering apparatus that employs lateral acceleration as a motion state quantity. Instead, the abnormality notification program can be applied to a steering apparatus that employs a yaw rate as a motion state quantity. Hereinafter, this modification will be described. As shown by a broken line in FIG. 1, the steering apparatus in this modified example includes a yaw rate sensor 39 that detects an actual yaw rate γ that is a movement state quantity that can be perceived by the driver, instead of the lateral acceleration sensor 34 in the above embodiment. I have. Other configurations are the same as those in the above embodiment, but the computer program executed by the electronic control unit 35 is slightly different from that in the above embodiment with respect to the turning operation. Moreover, since the abnormality notification program applied to the steering device that uses the yaw rate according to this modification as the motion state quantity is the same as the abnormality notification program of the above-described embodiment, detailed description thereof is omitted.

  In this modification, the computer program executed by the electronic control unit 35 with respect to the steering operation is shown in the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the above embodiment, but a torque-yaw rate conversion unit 54 is provided instead of the torque-lateral acceleration conversion unit 52 in the above embodiment. ing.

The torque-yaw rate conversion unit 54 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected yaw rate γd that the driver expects from the turning operation of the steering handle 11 to the steering torque Td. If the absolute value is less than the positive small predetermined value To, the value is set to “0” as shown in the following equation 18;
γd = 0 (| Td | <To) Equation 18
γd = C · Td ^K2 (To ≦ | Td |) Equation 19
However, C and K2 in Equation 19 are constants as in the above embodiment. Also in this case, the steering torque Td in the equation 19 represents the absolute value of the steering torque Td calculated using the above equation 2. If the calculated steering torque Td is positive, the constant C Is a positive value, and if the calculated steering torque Td is negative, the constant C is a negative value having the same absolute value as the positive constant C. In this case, the expected yaw rate γd may be calculated using a conversion table having characteristics as shown in FIG. 9 in which the expected yaw rate γd with respect to the steering torque Td is stored instead of the calculations of the equations 18 and 19. Good.

  Further, the turning angle conversion unit 55 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected yaw rate γd, and changes according to the vehicle speed V as shown in FIG. And a table representing the change characteristic of the target turning angle δd with respect to the expected yaw rate γd. This table is a set of data collected by actually measuring the turning angle δ and yaw rate γ of the left and right front wheels FW1 and FW2 while driving the vehicle while changing the vehicle speed V. Then, the turning angle conversion unit 55 refers to this table and calculates the target turning angle δd corresponding to the input expected yaw rate γd and the detected vehicle speed V input from the vehicle speed sensor 33. Further, the yaw rate γ (expected yaw rate γd) and the target turning angle δd stored in the table are both positive, but if the expected yaw rate γd supplied from the turning angle conversion unit 55 is negative, The output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the yaw rate γ as shown in the following equation 20, it can be calculated by executing the calculation of the following equation 20 instead of referring to the table. .
δd = L · (1 + A · V ² ) · γd / V Equation 20
However, also in Equation 20, L is a predetermined value (for example, 2.67 m) indicating the wheel base, and A is a predetermined value (for example, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 63 of the turning control unit 60. The turning angle correction unit 63 receives the expected yaw rate γd from the torque-yaw rate conversion unit 54 and also the actual yaw rate γ detected by the yaw rate sensor 39, and executes the calculation of the following equation (21). The corrected target turning angle δda is calculated by correcting the input target turning angle δd.
δda = δd + K4 · (γd−γ) Equation 21
However, the coefficient K4 is a predetermined positive constant, and when the actual yaw rate γ is less than the expected yaw rate γd, the coefficient K4 is corrected so that the absolute value of the corrected target turning angle δda becomes larger. When the actual yaw rate γ exceeds the expected yaw rate γd, the absolute value of the corrected target turning angle δda is corrected. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected yaw rate γd are more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the above embodiment. And in the functional block diagram of FIG. 8, the same code | symbol as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  Also in the modified example described above, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque Td is The torque-yaw rate conversion unit 54 converts it into the expected yaw rate γd, and the left and right front wheels FW1, FW2 are corrected by the turning angle conversion unit 55, the turning angle correction unit 63, and the drive control unit 62 to generate the corrected target yaw rate γd. It is steered to the steering angle δda. Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the yaw rate γ generated in the vehicle by the steering of the left and right front wheels FW1 and FW2 is a physical quantity that can be perceived, and the yaw rate γ is controlled to be equal to the expected yaw rate γd. It changes in a power function with respect to θ (exponentially by changing Expression 19 in the same manner as changing from Expression 4 to Expression 5 in the above embodiment). Therefore, the driver can turn the steering wheel 11 by turning the steering handle 11 according to the human perception characteristic while feeling the yaw rate according to the Weber-Hefner law. As a result, the driver can operate the steering handle 11 in accordance with the human perceptual characteristics, as in the case of the above-described embodiment, so that the driving of the vehicle is simplified.

  The abnormality notification program in the above embodiment is applied to a steering apparatus that employs lateral acceleration as an amount of motion state. Alternatively, the present invention can be applied to a steering apparatus that employs a turning curvature as a motion state quantity. Hereinafter, this modification will be described. Also in this modification, the steering device is configured as shown in FIG. 1 as in the above embodiment. However, regarding the turning operation, the computer program executed by the electronic control unit 35 is slightly different from that in the above embodiment. Moreover, since the abnormality notification program applied to the steering device using the turning curvature according to this modification as the amount of motion state is the same as the abnormality notification program of the above-described embodiment, detailed description thereof is omitted.

  In this modification, the computer program executed by the electronic control unit 35 with respect to the steering operation is shown in the functional block diagram of FIG. In this case, in the sensory adaptation control unit 50, the displacement-torque conversion unit 51 functions in the same manner as in the above embodiment, but a torque-turning curvature conversion unit 56 is provided instead of the torque-lateral acceleration conversion unit 52 in the above embodiment. It has been.

The torque-turning curvature conversion unit 56 uses the steering torque Td calculated by the displacement-torque conversion unit 51 to calculate the expected turning curvature ρd that the driver expects by turning the steering handle 11 as the steering torque. If the absolute value of Td is less than a small positive predetermined value To, it is set to “0” as shown in Equation 22 below, and if the absolute value of the steering torque Td is greater than or equal to a positive small predetermined value To, it is calculated according to Equation 23 below.
ρd = 0 (| Td | <To) Equation 22
ρd = C · Td ^K2 (To ≦ | Td |) Equation 23
However, C and K2 in Expression 23 are constants as in the above embodiment. Also in this case, the steering torque Td in the equation 23 represents the absolute value of the steering torque Td calculated using the above equation 2. If the calculated steering torque Td is positive, the constant C Is a positive value, and if the calculated steering torque Td is positive, the constant C is a negative value having the same absolute value as the positive constant C. In this case, the expected turning curvature ρd is calculated using a conversion table having characteristics as shown in FIG. 12 in which the expected turning curvature ρd with respect to the steering torque Td is stored in place of the calculations of the equations 22 and 23. May be.

  Further, the turning angle conversion unit 57 calculates the target turning angle δd of the left and right front wheels FW1 and FW2 necessary for generating the expected turning curvature ρd, according to the vehicle speed V as shown in FIG. There is a table that changes and represents the change characteristic of the target turning angle δd with respect to the expected turning curvature ρd. This table is a set of data collected by actually measuring the turning angle δ and the turning curvature ρ of the left and right front wheels FW1 and FW2 while the vehicle is running while changing the vehicle speed V. Then, the turning angle conversion unit 57 refers to this table and calculates the target turning angle δd corresponding to the input expected turning curvature ρd and the detected vehicle speed V input from the vehicle speed sensor 33. The turning curvature ρ (expected turning curvature ρd) and the target turning angle δd stored in the table are both positive, but the expected turning curvature ρd supplied from the torque-turning curvature conversion unit 56 is negative. If so, the output target turning angle δd is also negative.

Since the target turning angle δd is a function of the vehicle speed V and the turning curvature ρ as shown in the following equation 24, the target turning angle δd can be calculated by executing the operation of the following equation 24 instead of referring to the table. it can.
δd = L · (1 + A · V ² ) · ρd Equation 24
However, also in the formula 24, L is a predetermined value (eg, 2.67 m) representing the wheel base, and A is a predetermined value (eg, 0.00187).

The calculated target turning angle δd is supplied to the turning angle correction unit 64 of the turning control unit 60. The turning angle correction unit 64 receives the expected turning curvature ρd from the torque-turning curvature conversion unit 56 and also receives the actual turning curvature ρ from the turning curvature calculation unit 65. The turning curvature calculation unit 65 uses the lateral acceleration G detected by the lateral acceleration sensor 34 or the yaw rate γ detected by the yaw rate sensor 39 and the vehicle speed V detected by the vehicle speed sensor 33 to calculate the following Expression 25. The actual turning curvature ρ is calculated by execution and output to the turning angle correction unit 64.
ρ = G / V ² or ρ = γ / V Equation 25

And the turning angle correction | amendment part 64 performs the calculation of following formula 26, correct | amends the input target turning angle (delta) d, and calculates corrected target turning angle (delta) da.
δda = δd + K5 · (ρd−ρ) Equation 26
However, the coefficient K5 is a positive constant determined in advance, and when the actual turning curvature ρ is less than the expected turning curvature ρd, the coefficient K5 is corrected so that the absolute value of the corrected target turning angle Δda is increased. When the actual turning curvature ρ exceeds the expected turning curvature ρd, the absolute value of the corrected target turning angle δda is corrected to be smaller. By this correction, the turning angles of the left and right front wheels FW1, FW2 necessary for the expected turning curvature ρd are more accurately ensured.

  The other program processing executed by the electronic control unit 35 is the same as that in the above embodiment. And in the functional block diagram of FIG. 11, the code | symbol same as FIG. 2 of the said embodiment is attached | subjected, and the description is abbreviate | omitted.

  Also in the modified example described above, the steering angle θ as the operation input value of the driver with respect to the steering handle 11 is converted into the steering torque Td by the displacement-torque converter 51, and the converted steering torque Td is The torque-turning curvature converting unit 56 converts the predicted turning curvature ρd, and the left and right front wheels FW1 and FW2 are necessary to generate the expected turning curvature ρd by the turning angle conversion unit 57, the turning angle correction unit 64, and the drive control unit 62. To the correct correction target turning angle δda. Also in this case, since the steering torque Td is equal to the reaction force torque Tz, it is a physical quantity that can be perceived by the driver from the steering handle 11 by the action of the reaction force actuator 13, and changes exponentially with respect to the steering angle θ. Therefore, the driver can turn the steering handle 11 according to the human perceptual characteristic while feeling the reaction force according to the Weber-Hefner law.

  Further, the turning curvature due to the turning of the left and right front wheels FW1 and FW2 is also a physical quantity that can be visually perceived, and this turning curvature ρ is controlled to be equal to the expected turning curvature ρd, and the expected turning curvature ρd is also steered. It changes in a power function with respect to the angle θ (exponentially by changing Expression 23 in the same manner as changing from Expression 4 to Expression 5 in the above embodiment). Accordingly, the driver can turn the vehicle by turning the steering handle 11 according to human perceptual characteristics while visually perceiving the turning curvature according to the Weber-Hefner's law. As a result, the driver can operate the steering wheel 11 in accordance with the human perceptual characteristics as in the case of the above-described embodiment, so that the driving of the vehicle is simplified.

  Furthermore, in carrying out the present invention, the present invention is not limited to the above-described embodiments and modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment and each modified example, the abnormality notification program according to the present invention converts the steering angle and the steering torque as the operation input value input to the steering handle into the expected motion state quantity, and the conversion is expected. The present invention was applied to a steer-by-wire vehicle steering device that calculates the steering angle using the amount of motion state. However, the abnormality notification program according to the present invention is applied to a conventional steer-by-wire vehicle steering device that directly calculates the steering angle based on the steering angle and steering torque input to the steering wheel. Is also possible. Even in this case, it is only necessary to detect and calculate the driver's minute steering torque change by using the steering torque sensor already mounted on the vehicle to determine the driving operation state of the driver. The cost can be reduced and the control system can be simplified. And a driver | operator's driving operation state can be detected reliably and a warning can be alert | reported exactly.

  Moreover, in the said embodiment and each modification, in order to steer a vehicle, the steering handle 11 rotated is used. However, instead of this, for example, a joystick-type steering handle that is linearly displaced may be used, or any other one that can be operated by the driver and instructed to steer the vehicle is used. May be.

  Moreover, in the said embodiment and each modification, by rotating the steering output shaft 22 using the steering actuator 21, the left and right front wheels FW1 and FW2 were steered. However, instead of this, the left and right front wheels FW1, FW2 may be steered by linearly displacing the rack bar 23 using the steered actuator 21.

  Further, in the above-described embodiment and each modified example, lateral acceleration, yaw rate, and turning curvature are each independently used as the amount of vehicle motion state that can be perceived by humans. However, the vehicle steering control may be performed by switching the amount of motion state of these vehicles by a selection operation by the driver or by automatically switching according to the traveling state of the vehicle. When switching automatically according to the traveling state of the vehicle, for example, when the vehicle is traveling at a low speed (for example, less than 40 km / h), the turning curvature is used as the motion state quantity, and the vehicle is traveling at a medium speed (for example, 40 km). / H or more and less than 100 km / h), the yaw rate is used as the motion state quantity, and lateral acceleration is used as the motion state quantity when the vehicle is traveling at a high speed (for example, 100 km / h or more). According to this, appropriate steering control of the vehicle is performed according to the running state of the vehicle, and the driving of the vehicle becomes easier.

1 is a schematic view of a vehicle steering apparatus according to an embodiment of the present invention. FIG. 2 is a functional block diagram functionally representing a computer program process of steering control executed by the electronic control unit of FIG. 1 according to the embodiment of the present invention. It is a graph which shows the relationship between a steering angle and a steering torque. It is a graph which shows the relationship between steering torque and estimated lateral acceleration. It is a graph which shows the relationship between a prospective lateral acceleration and a target turning angle. 2 is a flowchart showing an abnormality notification program executed by the electronic control unit of FIG. 1 according to the embodiment of the present invention. (A) to (c) are graphs for explaining detection of the driving operation state of the driver. FIG. 9 is a functional block diagram functionally representing a computer program process of steering control executed by the electronic control unit of FIG. 1 according to a modification of the present invention. It is a graph which shows the relationship between steering torque and estimated yaw rate. It is a graph which shows the relationship between an expected yaw rate and a target turning angle. FIG. 9 is a functional block diagram functionally representing a computer program process of steering control executed by the electronic control unit of FIG. 1 according to a modification of the present invention. It is a graph which shows the relationship between steering torque and prospective turning curvature. It is a graph which shows the relationship between a prospective turning curvature and a target turning angle.

Explanation of symbols

FW1, FW2 ... front left and right wheels, 11 ... steering handle, 12 ... steering input shaft, 13 ... reaction force actuator, 21 ... steering actuator, 22 ... steering output shaft, 31 ... steering angle sensor, 32 ... steering angle sensor, 33 ... Vehicle speed sensor, 34 ... Lateral acceleration sensor, 35 ... Electronic control unit, 38 ... Steering torque sensor, 39 ... Yaw rate sensor, 40 ... Reaction force control unit, 50 ... Sensory adaptation control unit, 51 ... Displacement-torque conversion unit, 52 ... Torque-lateral acceleration conversion unit, 53, 55, 57 ... Steering angle conversion unit, 54 ... Torque-yaw rate conversion unit, 56 ... Torque-turning curvature conversion unit, 60 ... Steering control unit, 61, 63, 64 ... Turning angle correction unit

Claims (5)

A steering handle that is operated by a driver to steer the vehicle, a reaction force actuator that applies a reaction force to the operation of the steering handle, a steering actuator that steers a steered wheel, and the steering In a steering device for a steering-by-wire vehicle equipped with a steering control device that drives and controls the steering actuator according to the operation of the steering wheel to steer the steered wheels,
An operation force sensor for detecting the operation force of the driver with respect to the steering wheel;
A small operating force detecting means for detecting a minute operation force exerted on the steering wheel by using the detected operation force,
By comparing a predetermined allowable value calculated by multiplying a predetermined Weber ratio with respect to the operation force with respect to the steering wheel and the detected operation force with the detected minute operation force , A driver state detecting means for detecting a change in driving operation state;
A steering-by-wire vehicle steering apparatus comprising: warning notification means for notifying the driver of a warning according to the driving operation state of the driver detected by the driver state detection means. In the steering device for a steering-by-wire vehicle according to claim 1 ,
Before SL operation detection means comprises a detection means detects a change in the driving operation state of the driver by the detected small operating force to determine whether the larger than the predetermined allowable value A steering-by-wire steering system for a vehicle. In the steering device for a steering-by-wire vehicle according to claim 1,
Furthermore, a vehicle speed detecting means for detecting the vehicle speed of the vehicle is provided,
The driver state detection unit detects a change in the driving operation state of the driver when the vehicle speed detected by the vehicle speed detection unit is higher than a predetermined vehicle speed. Rudder device. In the steering device for a steering-by-wire vehicle according to claim 1,
The steering control device,
A value representing the amount of motion state of the vehicle that can be perceived by the driver in relation to the turning of the vehicle, and a value obtained by dividing a predetermined Weber ratio related to the amount of motion state by the predetermined Weber ratio related to the operating force. A motion state quantity calculation means for calculating a predicted motion state quantity of the vehicle defined as a power function of the operation force with an index as an index , using the operation force detected by the operation force sensor ;
A turning angle calculation means for calculating a turning angle of the steered wheels necessary for the vehicle to move with the calculated expected motion state quantity, using the calculated expected motion state quantity;
Of the steering-by-wire system, characterized in that is constituted by the steering control means for steering the steered angle of the steered wheels are the calculated and controls the turning actuator according to the turning angle that is the calculated Vehicle steering device. In the steering device for a steering-by-wire vehicle according to claim 4 ,
The predicted motion state quantity is a steering-by-wire vehicle steering apparatus that is one of a lateral acceleration, a yaw rate, and a turning curvature of the vehicle.

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