JP7526643B2 - Steering force control device, steering control device and steer-by-wire system - Google Patents

Description

The present invention relates to a steering force control device, a steering control device, and a steer-by-wire system.

Steering devices that assist steering operation by rotating an electric motor are known. For example, Patent Document 1 discloses a technology for improving the steering feeling by adding a rack axial force calculated based on various steering state quantities and vehicle state quantities to a basic target current control quantity calculated based on the driver's steering in calculating the control quantity of the electric power steering.

JP 2015-186942 A

The inventors of the present invention have discovered that the driver operating the vehicle senses the vehicle behavior based on changes in the vehicle's acceleration, and steers the vehicle based on the sensing of the vehicle behavior. The inventors of the present invention have discovered that if steering is performed based on the sensing of the vehicle behavior, the driver cannot achieve the steering sensation he or she desires in response to the vehicle behavior felt by the driver, and the driver's sense of unity with the vehicle is lost.

As such, there is still room for improvement in conventional steering devices in terms of improving vehicle drivability.

One aspect of the present invention aims to realize a steering force control device that makes it easier for the driver to feel a sense of unity with the vehicle and contributes to improving the drivability of the vehicle.

To solve the above problems, a steering force control device according to one aspect of the present invention includes a basic steering force component calculation unit that calculates a basic steering force component based on at least one of a driver's steering state quantity and a vehicle's motion state quantity, a first correction component calculation unit that calculates a first correction component based on the lateral acceleration of the vehicle, and a final steering force component calculation unit that calculates a final steering force component by correcting the basic steering force component with the first correction component.

According to one aspect of the present invention, it is possible to realize a steering force that makes it easier to feel a sense of unity with the vehicle and contributes to improving the drivability of the vehicle.

1 is a diagram illustrating an example of a configuration of a vehicle according to a first embodiment of the present invention; 1 is a block diagram showing a schematic configuration of an ECU according to a first embodiment of the present invention. FIG. 2 is a block diagram showing an example of the configuration of a steering control unit according to the first embodiment of the present invention. FIG. 11 is a block diagram showing an example of the configuration of a steering control unit according to a second embodiment of the present invention. FIG. 11 is a block diagram showing an example of the configuration of a steering control unit according to a third embodiment of the present invention. FIG. 10 is a diagram illustrating a schematic configuration of a main part of a steering device according to a fourth embodiment of the present invention. FIG. 13 is a block diagram showing an example of the configuration of a reaction force generating unit according to a fourth embodiment of the present invention.

[Embodiment 1]
Hereinafter, the first embodiment of the present invention will be described in detail.

[Vehicle configuration]
FIG. 1 is a diagram showing an example of the configuration of a vehicle 900 according to this embodiment. As shown in FIG. 1, the vehicle 900 includes a suspension 100, a vehicle body 200, wheels 300, tires 310, a steering member 410, a steering shaft 420, a torque sensor 430, a steering angle sensor 440, a torque application unit 460, a rack and pinion mechanism 470, a rack shaft 480, an engine 500, an ECU (Electronic Control Unit) 600, a power generation unit 700, and a battery 800. As shown in FIG. 1, the vehicle 900 may further include a steering force application unit 490 that applies a steering force to the rack shaft 480. Here, the suspension 100 and the ECU 600 constitute a suspension device according to this embodiment. Also, the rack and pinion mechanism 470, the rack shaft 480, and the ECU 600 constitute a steering device according to this embodiment.

The steering member 410, the steering shaft 420, the torque sensor 430, the steering angle sensor 440, the torque application unit 460, the rack and pinion mechanism 470, the rack shaft 480, and the ECU 600 constitute the electric power steering device according to this embodiment. The ECU 600 also includes an electric power steering control device that controls the steering device of the vehicle 900 using the electric power steering device.

The wheels 300, on which the tires 310 are mounted, are suspended from the vehicle body 200 by the suspension system 100. Since the vehicle 900 is a four-wheeled vehicle, the suspension system 100, the wheels 300, and the tires 310 are provided on each of the four wheels.

The tires and wheels of the left front wheel, right front wheel, left rear wheel, and right rear wheel are also referred to as tire 310A and wheel 300A, tire 310B and wheel 300B, tire 310C and wheel 300C, and tire 310D and wheel 300D, respectively. Similarly, below, the components associated with the left front wheel, right front wheel, left rear wheel, and right rear wheel may be expressed by adding the symbols "A", "B", "C", and "D", respectively.

The suspension system 100 includes a hydraulic shock absorber, an upper arm, and a lower arm. As an example, the hydraulic shock absorber includes a solenoid valve that adjusts the damping force generated by the hydraulic shock absorber. However, this does not limit the present embodiment, and the hydraulic shock absorber may use a solenoid valve other than a solenoid valve as the solenoid valve that adjusts the damping force. For example, the solenoid valve may be configured to include a solenoid valve that uses an electromagnetic fluid (magnetic fluid).

The engine 500 is equipped with a power generation device 700, and the electricity generated by the power generation device 700 is stored in the battery 800.

The steering member 410 operated by the driver is connected to one end of the steering shaft 420 in a torque transmitting manner, and the other end of the steering shaft 420 is connected to the rack and pinion mechanism 470.

The rack and pinion mechanism 470 is a mechanism for converting the rotation around the axis of the steering shaft 420 into a displacement along the axial direction of the rack shaft 480. When the rack shaft 480 is displaced in the axial direction, the wheels 300A and 300B are steered via the tie rod and the knuckle arm.

The torque sensor 430 detects the steering torque applied to the steering shaft 420, in other words, the steering torque applied to the steering member 410, and provides the ECU 600 with a torque sensor signal indicating the detection result. More specifically, the torque sensor 430 detects the twist of a torsion bar provided inside the steering shaft 420, and outputs the detection result as a torque sensor signal. Note that the torque sensor 430 may be a well-known sensor such as a Hall IC, an MR element, or a magnetostrictive torque sensor.

The steering angle sensor 440 detects the steering angle of the steering member 410 and provides the detection result to the ECU 600.

The torque application unit 460 applies an assist torque or a reaction torque corresponding to the steering control amount supplied from the ECU 600 to the steering shaft 420. The torque application unit 460 includes a motor that generates the assist torque or the reaction torque corresponding to the steering control amount as a motor torque, and a torque transmission mechanism that transmits the motor torque generated by the motor to the steering shaft 420.

In the above description, "connected so that torque can be transmitted" refers to a connection in which one member rotates as the other member rotates. For example, this includes at least the cases where one member and the other member are integrally molded, where one member is fixed directly or indirectly to the other member, and where one member and the other member are connected so as to be interlocked via a coupling member or the like.

The ECU 600 controls various electronic devices equipped in the vehicle 900. For example, the ECU 600 controls the magnitude of the assist torque or reaction torque applied to the steering shaft 420 by adjusting the steering control amount supplied to the torque application unit 460.

The ECU 600 also supplies a suspension control amount to a solenoid valve provided in a hydraulic shock absorber included in the suspension system 100, thereby controlling the opening and closing of the solenoid valve. To enable this control, a power line is provided to supply drive power from the ECU 600 to the solenoid valve.

The vehicle 900 also includes a wheel speed sensor 320 for each wheel 300 that detects the wheel speed of each wheel 300, a lateral G sensor 330 that detects the lateral acceleration of the vehicle 900, a longitudinal G sensor 340 that detects the longitudinal acceleration of the vehicle 900, a yaw rate sensor 350 that detects the yaw rate of the vehicle 900, a roll rate sensor 360 that detects the roll rate of the vehicle 900, a pitch rate sensor 370 that detects the pitch rate of the vehicle 900, an engine torque sensor 510 that detects the torque generated by the engine 500, an engine speed sensor 520 that detects the rotation speed of the engine 500, and a brake pressure sensor 530 that detects the pressure applied to the brake fluid of the brake device. The detection results from these various sensors are supplied to the ECU 600.

Although not shown in the figure, the vehicle 900 is equipped with an ABS (Antilock Brake System), which is a system for preventing wheel lock during braking, a TCS (Traction Control System), which suppresses wheel spin during acceleration, and a brake device that can be controlled by VSA (Vehicle Stability Assist), which is a vehicle behavior stabilization control system equipped with an automatic braking function for yaw moment control during turning or a brake assist function, etc.

Here, the ABS, TCS, and VSA compare the wheel speed determined according to the estimated vehicle speed with the wheel speed detected by the wheel speed sensor 320, and determine that a slip state exists if the two wheel speed values differ by a predetermined value or more. Through this processing, the ABS, TCS, and VSA perform optimal brake control or traction control according to the running state of the vehicle 900, thereby stabilizing the behavior of the vehicle 900.

In addition, the detection results from the various sensors described above are supplied to the ECU 600, and control signals are transmitted from the ECU 600 to each section via a CAN (Controller Area Network) 380.

Signals supplied to ECU 600 via CAN 380 include, for example, the following signals (signals in parentheses indicate the source of the signals):

Wheel speeds of the four wheels (wheel speed sensors 320A to 320D)
Pitch rate (pitch rate sensor 370)
Roll rate (roll rate sensor 360)
Yaw rate (yaw rate sensor 350)
Front and rear G (front and rear G sensor 340)
Lateral G (lateral G sensor 330)
Brake pressure (brake pressure sensor 530)
Engine torque (engine torque sensor 510)
Engine speed (engine speed sensor 520)
Steering angle (steering angle sensor 440)
Steering torque (torque sensor 430)
Images of the surroundings of the vehicle 900 (camera 550)

(ECU 600)
The ECU 600 will be specifically described below with reference to different drawings.

As shown in FIG. 2, the ECU 600 includes a steering control unit 610.

The steering control unit 610 refers to the detection results of various sensors included in the CAN 380 and sets the magnitude of the steering control amount to be supplied to the torque application unit 460. The steering control unit 610 supplies the set steering control amount to the torque application unit 460.

In this specification, the expression "with reference to" can include meanings such as "using," "taking into consideration," and "depending on."

The process of "setting the magnitude of the control amount" also includes setting the magnitude of the control amount to zero, i.e., not supplying a control amount.

(Steering control unit)
Next, the steering control unit 610 will be described in more detail with reference to Fig. 3. Here, the steering control unit 610 of the present embodiment is an example of a steering control device described in the claims. Fig. 3 is a block diagram showing an example of the configuration of the steering control unit 610.

As shown in FIG. 3, the steering control unit 610 includes a basic control amount calculation unit 611, a rack axial force calculation unit 612, and an adder unit 613. The steering control unit 610 calculates the steering control amount based on the basic control amount calculated by the basic control amount calculation unit 611 and the rack axial force calculated by the rack axial force calculation unit 612. Here, the rack axial force calculation unit 612 is an example of a steering force control device described in the claims.

The basic control amount calculation unit 611 calculates a basic control amount for controlling the magnitude of the assist torque or reaction torque according to the steering by the driver, based on the steering torque supplied from the torque sensor 430 and the vehicle speed calculated from the wheel speed supplied from the wheel speed sensor 320. The basic control amount calculated by the basic control amount calculation unit 611 is supplied to the addition unit 613.

Note that, as an example of a method for acquiring the vehicle speed of the vehicle 900, a configuration in which the vehicle speed is calculated from the wheel speed supplied from the wheel speed sensor 320 has been given, but this does not limit the present embodiment. For example, the vehicle 900 may further include a vehicle speed sensor, and the basic control amount calculation unit 611 may be configured to acquire the vehicle speed from this vehicle speed sensor.

The rack axial force calculation unit 612 calculates the rack axial force based on the driver's steering state quantity and the vehicle's motion state quantity. The rack axial force calculated by the rack axial force calculation unit 612 is supplied to the addition unit 613. Here, the rack axial force is an example of a steering force component that is a component that produces the driver's steering force. The specific configuration of the rack axial force calculation unit 612 will be described later.

The adder 613 calculates the steering control amount by adding the basic control amount supplied from the basic control amount calculation unit 611 and the rack axial force supplied from the rack axial force calculation unit 612. The adder 613 supplies the calculated steering control amount to the torque application unit 460.

<Rack axial force calculation section>
The rack axial force calculation section 612 includes a basic rack axial force calculation section 614, a first correction component calculation section 615, and a final rack axial force calculation section 616. Here, the basic rack axial force calculation section 614 is an example of a basic steering force component calculation section set forth in the claims. Also, the final rack axial force calculation section 616 is an example of a final steering force component calculation section set forth in the claims.

The basic rack axial force calculation unit 614 includes a motor torque calculation unit 617 and an adder unit 618. The basic rack axial force calculation unit 614 calculates the basic rack axial force as a basic steering force component based on at least one of the driver's steering state quantity and the vehicle's motion state quantity. Here, the driver's steering state quantity may be, for example, steering torque. Also, the vehicle's motion state quantity may be, for example, the motor current for controlling the motor included in the torque application unit 460 described above.

The motor torque calculation unit 617 calculates the motor torque to be generated in the motor provided in the torque application unit 460. Specifically, the torque application unit 460 determines the motor current based on the supplied steering control amount. The motor torque calculation unit 617 acquires the motor current from the torque application unit 460. The motor torque calculation unit 617 calculates the motor torque based on the acquired motor current. The motor torque calculation unit 617 supplies the calculated motor torque to the addition unit 618.

The adder 618 calculates the basic rack axial force by adding the steering torque supplied from the torque sensor 430 and the motor torque supplied from the motor torque calculation unit 617. The adder 618 supplies the calculated basic rack axial force to the final rack axial force calculation unit 616.

In this embodiment, the basic rack axial force calculation unit 614 calculates the basic rack axial force by adding the steering torque and the motor torque, but this does not limit the present embodiment. For example, the above-mentioned steering device may further include a rack axial force sensor that estimates the rack axial force, and the basic rack axial force calculation unit 614 may calculate the basic rack axial force based on the estimated rack axial force obtained from the rack axial force sensor.

The first correction component calculation unit 615 calculates a first correction component that corrects the basic steering force component based on the lateral acceleration of the vehicle 900 supplied from the lateral G sensor 330. The first correction component calculation unit 615 calculates a first correction component such that the basic steering force component is larger as the lateral acceleration is smaller, and calculates a first correction component such that the basic steering force component is smaller as the lateral acceleration is larger. More specifically, the first correction component calculation unit 615 calculates a first correction component with a larger absolute value as the lateral acceleration is smaller, and calculates a first correction component with a smaller absolute value as the lateral acceleration is larger.

The final rack axial force calculation unit 616 calculates the rack axial force as the final steering force component by correcting the basic rack axial force supplied from the basic rack axial force calculation unit 614 with the first correction component supplied from the first correction component calculation unit 615. The final rack axial force calculation unit 616 supplies the calculated rack axial force to the addition unit 613.

Here, the method of correcting the basic steering force component in the final rack axial force calculation unit 616 includes gain correction, in which a gain is set according to the lateral acceleration and the basic steering force component is multiplied by the gain. More specifically, the final rack axial force calculation unit 616 sets a gain according to the first correction component supplied from the first correction component calculation unit 615. The final rack axial force calculation unit 616 calculates the final steering force component by multiplying the set gain by the basic steering force component supplied from the basic rack axial force calculation unit 614. This calculation process is also called gain correction.

In this embodiment, an example has been given of a configuration in which gain correction is used as a method of correcting the basic steering force component in the final rack axial force calculation unit 616, but this embodiment is not limited to this. For example, additive correction may be used in which a first correction component is added to the basic steering force component. Alternatively, a filter may be applied to the basic steering force component, and filter correction may be used in which the coefficient of this filter is corrected based on the first correction component.

In addition, in this embodiment, an example has been given of a configuration in which the rack axial force calculated by the rack axial force calculation unit 612 is added to the basic control amount calculated by the basic control amount calculation unit 611 for correction, but this embodiment is not limited to this. For example, a configuration in which the rack axial force calculated by the rack axial force calculation unit 612 is used as a target steering torque value and feedback control is performed with the actual steering torque may be performed.

Here, the mechanism behind the relationship between vehicle motion and the driver's steering sensation is explained as follows.

The turning behavior of a vehicle is determined by the balance between the lateral load acting on the vehicle, which is the product of the lateral acceleration and the vehicle's mass, and the cornering performance of the tires. In the relationship between the lateral load (acting on the outside of the turning direction of the vehicle) and the tire cornering force (acting on the inside of the turning direction of the tire), if the lateral load exceeds the maximum value of the cornering force, the vehicle will drift out to the outside of the turning circle.

Here, the smaller the lateral acceleration, the smaller the lateral load value compared to the tire cornering force, and the larger the difference between the lateral load value and the cornering force value tends to be. With this tendency, the driver feels a sense of freedom when turning the steering wheel. More specifically, the driver feels as if the steering wheel is being pulled to the inside of the turn, even though the driver's body is not being pulled very much to the outside of the turn. Also, the greater the lateral acceleration, the larger the lateral load value compared to the tire cornering force, and the larger the difference between the lateral load value and the cornering force value tends to be. With this tendency, the driver feels like he wants to turn the steering wheel more. More specifically, the driver feels as if the steering wheel cannot be turned to the inside of the turn, even though the driver's body is being pulled to the outside of the turn.

The rack axial force calculation unit 612 according to this embodiment reduces the difference between the lateral load value and the cornering force value by calculating a first correction component based on the lateral acceleration of the vehicle. More specifically, the rack axial force calculation unit 612 according to this embodiment controls the value of the basic steering force component to be larger (to increase the steering reaction force) as the lateral acceleration is smaller, and controls the value of the basic steering force component to be smaller (to decrease the steering reaction force) as the lateral acceleration is larger. In this way, the rack axial force calculation unit 612 according to this embodiment makes it easier for the driver to feel a sense of unity between the steering and the vehicle behavior, improving drivability.

If the control in the rack axial force calculation unit 612 according to this embodiment is not introduced and the steering force is generated without considering the lateral acceleration, the steering force will not increase (the steering reaction force will not increase) even though the lateral acceleration is increasing, causing the driver to feel a sense of looseness, or conversely, the steering force will increase excessively (the steering reaction force will increase excessively), causing the driver to feel uncomfortable. In this way, if the control in the rack axial force calculation unit 612 according to this embodiment is not introduced and the steering force is generated without considering the lateral acceleration, the driver will feel that there is no sense of unity between the steering and the vehicle behavior, and drivability is low.

The rack axial force calculation unit 612 according to this embodiment corrects the steering force based on the lateral acceleration, based on the driver's perception of the vehicle behavior in response to changes in lateral acceleration, making it easier for the driver to feel a sense of unity between the steering and the vehicle behavior, improving drivability.

[Embodiment 2]
Hereinafter, a second embodiment of the present invention will be described in detail. For the sake of convenience, the same reference numerals will be given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

Figure 4 is a block diagram showing an example of the configuration of the steering control unit 610a. The steering control unit 610a according to this embodiment includes a first correction component calculation unit 615a instead of the first correction component calculation unit 615 in the steering control unit 610 according to embodiment 1.

The first correction component calculation unit 615a calculates a first correction component that corrects the basic steering force component based on the lateral acceleration of the vehicle 900 supplied from the lateral G sensor 330 and the longitudinal acceleration of the vehicle 900 supplied from the longitudinal G sensor 340. More specifically, the first correction component calculation unit 615a generates a value that serves as a basis for calculating the first correction component by adding the lateral acceleration and the longitudinal acceleration. The first correction component calculation unit 615a calculates the first correction component from this base value.

The first correction component calculation unit 615a calculates a first correction component that increases the basic steering force component as the longitudinal acceleration decreases. More specifically, the first correction component calculation unit 615a calculates a first correction component with a larger absolute value as the longitudinal acceleration decreases.

Here, the mechanism behind the relationship between vehicle motion and the driver's steering sensation is explained as follows.

For example, when turning on a curved road, the vehicle decelerates to enter the curved road and accelerates to leave the curved road. When braking or driving force is generated on the vehicle by decelerating or accelerating the vehicle, the load on the tires increases, and the cornering force decreases. As a result, the force in the turning direction of the tires becomes smaller. At this time, even though the driver would like to feel the tire compress and the grip force decrease, if they are unable to do so, the driver will feel an uncomfortable steering sensation. Thus, when a vehicle turns on a curved road, the effects of both lateral acceleration and longitudinal acceleration must be taken into consideration.

The rack axial force calculation unit 612a according to this embodiment controls the steering force to be increased by calculating a first correction component based on the longitudinal acceleration of the vehicle in addition to the lateral acceleration of the vehicle. More specifically, the rack axial force calculation unit 612a according to this embodiment controls the basic rack axial force to be greater (to increase the reaction force) as the longitudinal acceleration of the vehicle decreases, in addition to the configuration of the rack axial force calculation unit 612 according to the first embodiment. As a result, the rack axial force calculation unit 612a according to this embodiment makes it easier for the driver to feel a sense of unity between the steering and the vehicle's behavior, even when the vehicle is turning on a curved road, thereby improving drivability.

[Embodiment 3]
Hereinafter, the third embodiment of the present invention will be described in detail. For the sake of convenience, the same reference numerals will be given to members having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

Figure 5 is a block diagram showing an example of the configuration of the steering control unit 610b. The steering control unit 610b according to this embodiment includes a rack axial force calculation unit 612b instead of the rack axial force calculation unit 612a in the steering control unit 610a according to embodiment 2.

The rack axial force calculation unit 612b includes a basic rack axial force calculation unit 614, a first correction component calculation unit 615a, a final rack axial force calculation unit 616a, and a second correction component calculation unit 619.

The second correction component calculation unit 619 calculates a second correction component that corrects the basic steering force component based on the yaw rate of the vehicle 900 supplied from the yaw rate sensor 350. The second correction component calculation unit 619 calculates a second correction component such that the basic steering force component is larger as the yaw rate is smaller, and calculates a second correction component such that the basic steering force component is smaller as the yaw rate is larger. More specifically, the second correction component calculation unit 619 calculates a second correction component with a larger absolute value as the yaw rate is smaller, and calculates a second correction component with a smaller absolute value as the yaw rate is larger.

The final rack axial force calculation unit 616a calculates the rack axial force as a final steering force component by correcting the basic rack axial force supplied from the basic rack axial force calculation unit 614 with the first correction component supplied from the first correction component calculation unit 615a and the second correction component supplied from the second correction component calculation unit 619. More specifically, the final rack axial force calculation unit 616a calculates the rack axial force by adding the first correction component and the second correction component to the basic rack axial force. The final rack axial force calculation unit 616 supplies the calculated rack axial force to the addition unit 613.

In this embodiment, the second correction component calculation unit 619 has been described as calculating the second correction component based on the yaw rate, but this embodiment is not limited to this. For example, the second correction component calculation unit 619 of this embodiment may be configured to calculate the second correction component by referring to at least one of the yaw rate of the vehicle 900 supplied from the yaw rate sensor 350, the roll rate of the vehicle 900 supplied from the roll rate sensor 360, and the pitch rate of the vehicle 900 supplied from the pitch rate sensor 370. In this case, the second correction component calculation unit 619 calculates the second correction component so that the smaller the yaw rate, roll rate, or pitch rate is, the larger the basic steering force component is, and calculates the second correction component so that the larger the yaw rate, roll rate, or pitch rate is, the smaller the basic steering force component is. More specifically, the second correction component calculation unit 619 calculates a second correction component with a larger absolute value as the yaw rate, roll rate, or pitch rate is smaller, and calculates a second correction component with a smaller absolute value as the yaw rate, roll rate, or pitch rate is larger.

The rack axial force calculation unit 612b according to this embodiment performs a correction using a second correction component based on the yaw rate in addition to the first correction component, thereby making it possible to perform a correction to the basic steering force component that more accurately reflects the vehicle's turning behavior.

In addition, since the yaw rate and roll rate are related to the vehicle state quantity corresponding to the lateral acceleration, the basic steering force component can be corrected with a second correction component based on the yaw rate or roll rate to calculate a final steering force component that takes into account the vehicle state corresponding to the lateral acceleration. As a result, the rack axial force calculation unit 612b according to this embodiment makes it easier for the driver to feel a sense of unity between the steering and the vehicle behavior, improving drivability.

In addition, since the pitch rate is related to the vehicle state quantity corresponding to the longitudinal acceleration, the final steering force component that takes into account the vehicle state corresponding to the longitudinal acceleration can be calculated by correcting the basic steering force component with a second correction component based on the pitch rate. As a result, the rack axial force calculation unit 612b according to this embodiment makes it easier for the driver to feel a sense of unity between the steering and the vehicle behavior, improving drivability.

[Embodiment 4]
Hereinafter, a fourth embodiment of the present invention will be described in detail. For the sake of convenience, the same reference numerals will be given to members having the same functions as those described in the above embodiments, and the description thereof will not be repeated.

Figure 6 is a schematic diagram showing the main configuration of the steering device 1. In this embodiment, instead of the steering device described in the first to third embodiments in which the steering member 410 and the rack shaft 480 are always mechanically connected, a steer-by-wire type steering device 1 is provided.

The steering device 1 according to this embodiment includes a steering section 10, a turning section 20, a steering member 410, and an ECU 600, and is used to turn the wheels 300 in response to a steering operation by the driver via the steering member 410.

As shown in FIG. 6, the steering device 1 according to this embodiment is a steer-by-wire type steering device that does not have a mechanical torque transmission path between the steering member 410 and the steering unit 20, but can electrically control the steering angle of the wheels 300 in response to steering operations via the steering member 410.

As an example of the steering member 410, a steering wheel having a wheel shape as shown in FIG. 6 is given, but this does not limit the present embodiment, and other shapes and mechanisms may be used as long as they can accept steering operations by the driver.

(Steering unit 10)
The steering unit 10 has both a function of accepting a steering operation by a driver via a steering member 410 and a function of generating a reaction force against the steering operation and transmitting the reaction force to the steering member 410. As shown in FIG. 6 , the steering unit 10 includes a torque application unit 461, a steering shaft 420, and a torque sensor 430.

In the following description, "upper end" refers to the end closest to the steering member 410, and "lower end" refers to the end farther from the steering member 410.

The upper end of the steering shaft 420 is connected to the steering member 410 so as to be able to transmit torque, and the steering member 410 and the steering shaft 420 rotate together. The lower end of the steering shaft 420 is connected to the torque application unit 461 so as to be able to transmit torque, and the torsion occurring in the steering shaft 420 is detected by the torque sensor 430.

The torque application unit 461 generates torque according to the torque control signal supplied from the ECU 600.

(Steering unit 20)
The steering unit 20 is configured to steer the wheels 300 in response to the steering operation of the driver received by the steering unit 10. As shown in Fig. 6, the steering unit 20 includes a rack shaft 480, a tie rod 481, a knuckle arm 482, and a steering force application unit 490.

The steering force application unit 490 generates a steering force according to a steering force control signal from the ECU 600, and displaces the rack shaft 480 in the axial direction. As the rack shaft 480 displaces in the axial direction, the wheels 300 are steered via tie rods 481 provided at both ends of the rack shaft 480 and knuckle arms 482 connected to the tie rods 481.

(ECU 600)
ECU 600 according to this embodiment controls the steering force generated by steering force application section 490 and the torque generated by torque application section 461 in response to a steering operation by the driver.

More specifically, the ECU 600 references the torque sensor signal supplied from the torque sensor 430 to generate a torque control signal for controlling the torque generated by the torque application unit 461 and a steering force control signal for controlling the steering force generated by the steering force application unit 490, and supplies these to the torque application unit 461 and the steering force application unit 490, respectively.

The ECU 600 may be configured to generate a torque control signal and a steering force control signal by further referring to a signal indicating the steering angle of the steering member 410 and a vehicle speed signal from a vehicle speed sensor.

The ECU 600 controls the torque application unit 461 so that a reaction torque in the opposite direction to the driver's steering torque input via the steering member 410 is transmitted to the steering shaft 420. This allows the driver to obtain a sense of operation in response to the steering operation.

The ECU 600 according to this embodiment is equipped with a steering control unit 610C instead of the steering control unit described in the first to third embodiments.

Figure 7 is a block diagram showing an example of the configuration of the steering control unit 610c. The steering control unit 610c according to this embodiment further includes a reaction force control amount calculation unit 620 in addition to the steering control unit 610b according to embodiment 3.

The steering control unit (reaction force generating unit) 610c according to this embodiment functions both as a steering control unit that controls the magnitude of the steering control amount supplied to the steered unit 20 and as a reaction force generating unit that controls the magnitude of the reaction force control amount supplied to the steering unit 10. Here, the steering control unit 610c is an example of a reaction force generating device as described in the claims.

The steering control unit 610c calculates the steering control amount by adding the basic control amount supplied from the basic control amount calculation unit 611 and the rack axial force supplied from the rack axial force calculation unit 612 in the addition unit 613.

The steering control unit 610c supplies the steering control amount calculated in the adder 613 to the turning unit 20. The steering control unit 610c also supplies the steering control amount calculated in the adder 613 to the reaction force control amount calculation unit 620.

The reaction force control amount calculation unit 620 calculates a reaction force control amount for controlling the reaction force torque generated by the torque application unit 461 based on the acquired steering control amount. The reaction force control amount calculation unit 620 supplies the calculated reaction force control amount to the steering unit 10.

Thus, the steering control unit 610c according to this embodiment, even though it is configured as a steer-by-wire steering device, can easily make the driver feel a sense of unity between the steering and the vehicle behavior, improving drivability, as with the steering control units according to embodiments 1 to 3. More specifically, the steering control unit 610c according to this embodiment corrects the steering force based on the lateral acceleration based on the driver's perception of the vehicle behavior according to changes in lateral acceleration, so that the driver can easily feel a sense of unity between the steering and the vehicle behavior, improving drivability.

In this embodiment, a configuration in which a portion of the torque transmission path from the steering member 410 to the rack shaft 480 is mechanically separated at all times has been described as an example, but this does not limit the present embodiment. The steering device according to this embodiment may also be configured in which a portion of the torque transmission path from the steering member 410 to the rack shaft 480 is selectively separated.

In addition, in the explanation of the steering control unit 610c according to this embodiment, a configuration in which the steering control unit 610b according to embodiment 3 is modified has been given as an example, but this does not limit this embodiment. The steering control unit 610c according to this embodiment may be configured to further include a reaction force control amount calculation unit 620 in the steering control unit 610 according to embodiment 1 or the steering control unit 610a according to embodiment 2.

[Software implementation example]
The control blocks (steering control units 610, 610a, 610b) of the ECU 600 may be realized by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or may be realized by software using a CPU (Central Processing Unit).

In the latter case, the ECU 600 includes a CPU that executes the commands of a program, which is software that realizes each function, a ROM (Read Only Memory) or storage device (these are referred to as "recording media") in which the program and various data are recorded so as to be readable by the computer (or CPU), and a RAM (Random Access Memory) in which the program is expanded. The object of the present invention is achieved when the computer (or CPU) reads the program from the recording medium and executes it. The recording medium may be a "non-transient tangible medium," such as a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit. The program may also be supplied to the computer via any transmission medium (such as a communication network or a broadcast wave) capable of transmitting the program. The present invention may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. The technical scope of the present invention also includes embodiments obtained by appropriately combining the technical means disclosed in different embodiments.

610, 610a, 610b Steering control unit 610c Steering control unit (reaction force generation unit)
611: Basic control amount calculation unit 612, 612a, 612b: Rack axial force calculation unit (steering force control device)
613, 618 Addition unit 614 Basic rack axial force calculation unit (basic steering force component calculation unit)
615, 615a: First correction component calculation unit 616, 616a: Final rack axial force calculation unit (final steering force component calculation unit)
617 Motor torque calculation section 619 Second correction component calculation section 620 Reaction force control amount calculation section

Claims (11)

a basic steering force component calculation unit that calculates a basic steering force component based on at least one of a driver's steering state quantity and a vehicle motion state quantity;
a first correction component calculation unit that calculates a first correction component based on a lateral acceleration of the vehicle;
a second correction component calculation unit that calculates a second correction component for correcting the basic steering force component by referring to at least one of a roll rate and a pitch rate;
a final steering force component calculation unit that calculates a final steering force component by correcting the basic steering force component with the first correction component and the second correction component . The steering force control device according to claim 1, wherein the first correction component calculation unit calculates the first correction component such that the smaller the lateral acceleration is, the larger the basic steering force component is. The steering force control device according to claim 1 or 2, wherein the first correction component calculation unit calculates the first correction component so as to reduce the basic steering force component as the lateral acceleration increases. The steering force control device according to any one of claims 1 to 3, wherein the first correction component calculation unit calculates the first correction component based on the longitudinal acceleration of the vehicle in addition to the lateral acceleration. The steering force control device according to claim 4, wherein the first correction component calculation unit calculates the first correction component such that the smaller the longitudinal acceleration is, the larger the basic steering force component becomes. 6. The steering force control device according to claim 1, wherein the second correction component calculation unit calculates the second correction component such that the basic steering force component becomes smaller as the roll rate or the pitch rate becomes larger. 7. The steering force control device according to claim 6, wherein the second correction component calculation unit calculates the second correction component such that the basic steering force component becomes larger as the roll rate or the pitch rate becomes smaller. A steering control device comprising the steering force control device according to any one of claims 1 to 7 . An electric power steering device comprising the steering control device according to claim 8 . A reaction force generating device comprising the steering force control device according to any one of claims 1 to 7 . A steer-by-wire system comprising the reaction force generating device according to claim 10 .

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