WO2019181663A1 - Steering system and vehicle equipped with same - Google Patents

Abstract

Provided is a steering system equipped with a mechanical mechanism having a simple structure in which safety is ensured, such that it is possible to control the angle of left and right front wheels according to the vehicle speed and the steering instruction angle and improve the responsiveness of the vehicle to the steering command from an automatic steering driving device. This steering system (100) comprises: a first steering device (11) which is mechanically linked and steers left and right front wheels (9) by changing the angle of a suspension frame component (6); and a second steering device (150). The second steering device (150) changes the angle of the wheels (9) with respect to the suspension frame component (6) by driving an auxiliary steering actuator (5). The auxiliary steering control unit (151) of the second steering device (150) performs control so that the left and right front wheels (9) are turned on the basis of the steering instruction angle and the vehicle speed at a steering angle which is the difference between the steering angle determined by the numerical model of vehicle movement and the actual steering angle.

Description

Steering system and vehicle equipped with the same Related applications

This application is priority to Japanese Patent Application No. 2018-053064 filed on Mar. 20, 2018, Japanese Patent Application No. 2018-178253 filed on Sep. 25, 2018, and Japanese Patent Application No. 2019-040354 filed on Mar. 6, 2019. And is hereby incorporated by reference in its entirety as part of this application.

The present invention adds a mechanism for adding auxiliary steering of ± several degrees or less to a normal steering device, and improves the responsiveness of the vehicle to a driver's steering operation, and a vehicle equipped with the steering system About.

The conventional general steering device changes the angle of the underbody frame parts that are mechanically interlocked with the rotation of the steering wheel to steer the front wheels. The responsiveness to change is still low. Patent Documents 1 and 2 have been proposed as techniques for improving such responsiveness.

Patent Document 1 describes a vehicle behavior control device that controls the behavior of a vehicle whose front wheels are steered, in addition to reflecting the driver's intention in the behavior of the vehicle, and further improving the stability and riding comfort of the vehicle posture. It is a device for controlling the vehicle behavior.
The steering device in this document is a steering device that transmits rotation of a steering wheel to a front wheel, and includes a steering wheel side mechanism and a wheel side mechanism that steers a front wheel that is mechanically separated from the steering wheel side mechanism.
The steering wheel side mechanism is provided with a first steering angle sensor for detecting the rotational steering angle of the steering wheel, and the wheel side mechanism is provided with a second steering angle sensor for detecting a steering angle corresponding to steering of the front wheels. . The steering speed is calculated from the output of the first steering angle sensor and the output of the second steering angle sensor, and the steering generated in the vehicle is steering corresponding to the steering operation that the driver has intentionally performed, or disturbance Based on the outputs of the first and second steering angle sensors, the steering speed is determined based on the result of the determination.

Patent Document 2 describes that two motors are used in one wheel to adjust both the toe angle and the camber angle of the wheel.

Japanese Patent No. 6270251 German Patent Application Publication No. 10201206337

In the configuration using the steer-by-wire system as in Patent Document 1, it may be impossible to operate the vehicle, such as when the power supply fails during traveling, and there is a problem in safety.
Moreover, since the mechanism provided with the auxiliary steering function of patent document 2 etc. aims at changing the toe angle and camber angle of a wheel freely, it has a complicated structure. In the case of Patent Document 2, since two motors are used, not only the cost increases due to the increase in the number of motors, but also a complicated and large in order to control both the toe angle and the camber angle within one wheel. Become a mechanism.

The present invention solves the above-mentioned problems, and its object is to control the angle of the left and right front wheels according to the vehicle speed and the steering command angle while having a mechanical structure with a simple structure and ensuring safety. It is possible to provide a steering system and a vehicle capable of improving the responsiveness of the vehicle to a steering operation or a steering command from an automatic driving device.

Hereinafter, in order to facilitate understanding, the present invention will be described with reference to the reference numerals of the embodiments for convenience.

Steering system 100 of the present invention, the left and right wheels 9, 9 which is a front wheel of the vehicle 101 is mechanically interlocked, the right and left wheels as the front wheels of the vehicle 101 in accordance with the steering indication angle [delta] _h by rotation or electrical signals of the handle 200 A first steering device 11 that steers 9 and 9 by changing the angle of the left and right underbody frame parts 6 and 6 of the suspension device 12 on which the left and right wheels 9 and 9 are installed;
By driving auxiliary steering actuators 5, 5 provided for the left and right wheels 9, 9, the angles of the wheels 9, 9 with respect to the underbody frame parts 6, 6 are changed to change the left and right wheels 9. , 9 are individually steered, a second steering device 150,
A vehicle information detection unit 110 which detects the vehicle information including the vehicle speed V and the steering instruction angle [delta] _h of the vehicle 101,
A steering system 100 comprising:
The second steering device 150, the front wheel steering angle [delta] which is obtained by numerical model M of vehicle motion based on the steering instruction angle [delta] _h and information of the vehicle speed V, is steered by the first steering device 11 An auxiliary turning control unit 151 that controls the auxiliary turning actuator 5 so as to turn by an additional turning steering angle δ _{2 that} is a difference from the actual steering angle δ ₁ of the front wheels 9, 9. It is characterized by that.

According to this configuration, the first steering device 11, the steering instruction accordance angle [delta] _h the left and right suspension frame parts 6,6 and the angle changes in mechanical interlocking, the left and right wheels 9, 9 are front legs It is steered together with the rotating frame parts 6 and 6. For example, mechanically interlocking with the rotation of the steering wheel 200 by the driver, the left and right underbody frame parts 6 change the angle, and the wheels 9 and 9 that are front wheels together with the underbody frame parts 6 and 6 are steered. This steering is the same as general vehicle steering. The steering by the second steering device 150 is added to the steering angle δ ₁ by the first steering device 11 by the control by the auxiliary steering control unit 151.

In this case, the second steering device 150, based on the information of the steering instruction angle [delta] _h and the vehicle speed V, as a numerical model M of the vehicle motion, i.e. dynamic model by the response best steering angle (ideal steering angle) The auxiliary steering actuator 5 is controlled so as to steer only the steering angle δ ₂ which is the difference between the obtained steering angle δ and the steering angle δ ₁ of the actual wheels 9 and 9 steered by the first steering device 11. To do. That is, during turning, according to the traveling speed and the steering instruction angle [delta] _h, so that the appropriate wheel angle based on the dynamic model of the vehicle, is corrected by the second steering device 150. Therefore, it is possible to improve the responsiveness to the steering operation or the steering command from the automatic driving device.
Since the second steering device 150 corrects steering by normal steering operation as described above, the maximum turning angle may be limited to, for example, ± several degrees (± 2 to ± 5). . Therefore, unlike the conventional steer-by system, even when the auxiliary steering actuator 5 cannot be operated correctly due to a power failure or the like, the influence on the traveling direction of the vehicle 101 is small and safety is ensured. The The second steering device 150 adds steering of an angle of ± several degrees or less, and only one auxiliary steering actuator 5 is required. Therefore, both the conventional toe angle and camber angle are adjusted. Compared to the mechanism, a simple structure is sufficient. Further, since the steering angle is corrected within ± several degrees, the response to the steering wheel operation can be improved without causing the driver to feel danger.
Thus, while using the mechanism structure is to ensure simple and safe, and controls the steering angle of the left and right wheels 9, 9 in accordance with the vehicle speed V and the steering instruction angle [delta] _h, the driver steering or It becomes possible to improve the responsiveness of the vehicle 101 with respect to the steering command from the automatic driving device.

In the steering system 100 according to the present invention, a two-wheel model is used for the control by which the auxiliary steering control unit 151 of the second steering device 150 determines and steers the steering angle δ ₂ of the additional steering. (14) may be used.

here,
δ ₂ : Steering angle of additional steering as a difference δ _h : Steering instruction angle V: Vehicle speed V _{β = 0} : Vehicle speed when side slip angle β with respect to the steering angle is 0 n: Steering instruction angle and front wheel steering Ratio to angle (gear ratio)
ζ: damping rate ω _n : natural frequency (vehicle natural frequency)
α ₁ , α ₂ , α ₃ : Parameter k _r : Tire cornering power per rear wheel l _r : Distance between vehicle center of gravity and rear wheel axle l: Distance between front wheel axle and rear wheel axle (l _f + l _r )
I: Yaw moment of inertia of vehicle s: Complex variable in Laplace transform

Using the above equation (14), as described in detail in the detailed description section of the present invention, based on the information of the steering instruction angle [delta] _h and the vehicle speed V, the steering angle of the front wheels of the ideal calculated by numerical model of vehicle motion [delta] And the steering angle δ _{2 of} the additional turning that is the difference between the actual steering angle δ ₁ of the actual wheels 9 and 9 steered by the first steering device 11, that is, the steering angle δ to be supplementarily added is appropriately obtained. be able to. Therefore, it is possible to satisfactorily improve the response of the vehicle to the driver's steering operation.

　上記式(27)を用いて追加転舵の操舵角δ_ｈｂを演算し、左右それぞれの第２のステアリング装置１５０を微小な角度で制御することで、タイヤの操縦安定性能を効果的に利用できる。 In the steering system 100 of the present invention, the following equation (27) is used for the control for _obtaining the steering angle δ _hb of the additional turning by the auxiliary turning control unit 151 of the second steering device 150 and turning it. Also good.

By calculating the steering angle δ _hb of the additional turning using the above equation (27) and _controlling the left and right second steering devices 150 at minute angles, the steering stability performance of the tire can be effectively used. .

In the steering system 100 of the present invention, the auxiliary steering control unit 151 includes the steering angles δ of the left and right front wheels determined by the numerical model of the vehicle motion, and the actual front wheels steered by the first steering device 11. Even if the auxiliary steering actuators 5 and 5 are controlled so that they are steered only by the individual steering angles (δ _2L , δ _2R ) of the additional steering that are the respective differences from the respective left and right steering angles δ _1. Good. In this case, when turning the vehicle, for example, by finely changing the left and right steering angles, the running characteristics of the vehicle are changed, and the load applied to each of the wheels 9, 9 can be finely controlled. Further improvements in vehicle performance can be expected.

In the steering system 100 of the present invention, the second steering device 150 is connected to the hub unit body 2 having the wheel bearing hub bearing 15 and the suspension frame component 6 or a part of the suspension frame component 6. A unit support member 3 configured as
The hub unit main body 2 is supported by the unit support member 3 via a rotation-allowing support component 4 so as to be rotatable around an auxiliary turning axis A extending in the vertical direction, and is driven by the auxiliary turning actuator 5. A hub unit with an auxiliary turning function rotated around the auxiliary turning axis A may be used.
By configuring the second steering device 150 as described above, the toe angles of the wheels 9 and 9 attached to the hub unit body 2 can be freely adjusted with a simple structure without changing the basic structure of an existing vehicle. can do.

In the steering system 100 according to the present invention, the second steering device 150 is connected to the hub unit main body 2 having the wheel bearing mounting hub bearing 15 and the underbody frame part 6 or a part of the underbody frame part 6. A mechanism unit 150a having a unit support member 3 configured to support the hub unit body 2 with respect to the undercarriage frame component 6 so that the angle of the hub unit body 2 can be changed, the auxiliary turning control unit 151, and the auxiliary turning control. A control device unit 150b having motor control devices 170 and 175 for driving the auxiliary steering actuator 5 by outputting a drive current corresponding to the motor command signal output by the unit 151 may be used.
By configuring the second steering device 150 to include the mechanism unit 150a and the control unit 150b as described above, while using a mechanical mechanism that has a simple structure and ensures safety, the vehicle speed V and in accordance with the steering instruction angle [delta] _h separately control the angle of the left and right wheels, is possible to improve the responsiveness of the vehicle relative to steering operation of the driver can be realized with a simple configuration.

In the steering system 100 of the present invention, the auxiliary steering actuator 5 of the second steering device 150 may include a reverse input prevention mechanism 25b.
When the reverse input prevention mechanism 25b is provided, when an abnormality occurs in the control system, the control of the auxiliary steering actuator 5 is stopped immediately, and the reverse input from the road surface is prevented, thereby preventing the hub unit from moving. Fluctuation can be suppressed, and the vehicle can be moved to a state where it can be surely stopped by the driver's steering operation, and safety can be ensured. The reverse input prevention mechanism 25b can be easily configured by using a trapezoidal screw as a mechanism for transmitting the operation of the auxiliary turning actuator 5.

The vehicle of the present invention is a vehicle equipped with the steering system 100 having any one of the above-described configurations of the present invention.
According to the vehicle of this configuration, by using a mechanical mechanism which structure is to ensure simple and safe to the steering system 100 to control the steering angle of the left and right front wheels in accordance with the vehicle speed V and the steering instruction angle [delta] _h Thus, the responsiveness of the vehicle 101 to the steering operation of the driver and the steering command from the automatic driving device can be improved.

Any combination of at least two configurations disclosed in the claims and / or the specification and / or the drawings is included in the present invention. In particular, any combination of two or more of each claim in the claims is included in the invention.

The present invention will be understood more clearly from the following description of preferred embodiments with reference to the accompanying drawings. However, the embodiments and drawings are for illustration and description only and should not be used to define the scope of the present invention. The scope of the invention is defined by the appended claims. In the accompanying drawings, the same reference numerals in a plurality of drawings indicate the same or corresponding parts.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically showing a conceptual configuration of a steering system and a vehicle equipped with the system according to an embodiment of the present invention. It is a block diagram which shows the conceptual structure of the steering system. It is a figure which shows the premise of the conceptual structure of the auxiliary steering control part of the steering system. It is a block diagram which shows the conceptual structure of the auxiliary steering control part of the steering system. It is explanatory drawing of the four-wheel model of the vehicle. It is explanatory drawing of the two-wheel model which converted the same four-wheel model. It is a graph which shows the change of the yaw angular velocity of a vehicle, and a lateral acceleration with respect to the case where auxiliary steering control is performed in the steering system. It is a longitudinal cross-sectional view which shows the structure of the mechanism part of the 2nd steering apparatus in the steering system, and its periphery. It is a horizontal sectional view showing composition of a mechanism part etc. of the 2nd steering device. It is a horizontal sectional view showing different operation states of a mechanism part etc. of the second steering device. It is a perspective view which shows the external appearance of the mechanism part of the 2nd steering apparatus. It is a disassembled front view of the mechanism part of the 2nd steering device. It is a side view of the mechanism part of the 2nd steering device. It is a top view of the mechanism part of the 2nd steering device. It is the XIV-XIV sectional view taken on the line of FIG. It is a figure which shows the analysis result of a vehicle locus | trajectory and a lateral acceleration. It is a figure which shows the analysis result of a left tire angle and a right tire angle.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram schematically showing a conceptual configuration of a vehicle 101 such as an automobile equipped with a steering system 100 according to this embodiment. The vehicle 101 is a four-wheel vehicle having left and right wheels 9 and 9 as front wheels and left and right wheels 9 and 9 as rear wheels, and the driving method is any of front wheel drive, rear wheel drive, and four wheel drive. It may be.

The steering system 100 is a system for steering the vehicle 101, and includes a first steering device 11, a second steering device 150, and a vehicle information detection unit 110.

<Configuration of first steering device 11>
The first steering device 11 is mechanically interlocked with the handle 200, and the left and right wheels 9, 9 that are the front wheels according to the steering instruction angle that is the handle angle are connected to the left and right feet on which the left and right wheels 9, 9 are installed. This device is steered by changing the angle of the rotating frame parts 6 and 6. The suspension frame parts 6 and 6 are knuckles in this embodiment.
The first steering device 11 has a known mechanical configuration such as a steering shaft 32 to which a handle 200 is attached, a rack and pinion (not shown), a tie rod 14 and the like. When the driver inputs rotation to the handle 200, the steering shaft 32 also rotates in conjunction with it. When the steering shaft 32 rotates, the tie rod 14 connected to the steering shaft 32 by the rack and pinion moves in the vehicle width direction, so that the suspension frame 12 and the suspension frame component 6 are installed on the suspension frame component 6. The direction of the wheel 9 is changed, and the left and right wheels 9 and 9 can be steered in conjunction with each other.

<Schematic configuration of second steering device 150>
The second steering device 150 is a device that performs auxiliary steering by control according to the state of the vehicle 101, and includes a mechanism portion 150 a that is a mechanical structure portion, and a control device portion 150 b that controls the mechanism portion 150 a. Have
The mechanism portion 150a is a mechanism provided for each of the wheels 9 and 9 to be auxiliary-steered, and is provided in the tire housing 105 of the vehicle 101 to drive the wheels 9 individually by driving the auxiliary-steering actuator 5. The underbody frame component 6 is steered. As shown in FIGS. 1 and 7, the mechanism unit 150a is connected to the hub unit body 2 having the hub bearing 15 and the suspension frame part 6 or is configured as a part of the suspension frame part 6 to form a hub unit. It is configured as a hub unit with an auxiliary turning function having a unit support member 3 that supports the main body 2 with respect to the undercarriage frame component 6 so that the angle can be changed. The auxiliary steering actuator 5 includes a reverse input prevention mechanism 25b (see FIG. 8) that prevents reverse input in which an external force from the road surface enters the motor 26 serving as a drive source.

The second steering device 150 is configured as a hub unit with an auxiliary turning function as described above, and has one auxiliary turning axis A different from the rotation axis of the wheel 9 in the hub unit. Further, the auxiliary turning actuator 5 in the hub unit is turned around the auxiliary turning axis A. The left and right wheels 9, 9 can be steered independently.

Details of the mechanism portion 150a will be described later with reference to FIGS.
In FIG. 1, the control device unit 150 b includes an auxiliary turning control unit 151 that controls the auxiliary turning actuator 5 based on the vehicle information representing the state of the vehicle 101 detected by the vehicle information detection unit 110.

<Vehicle information detection unit 110>
The vehicle information detection unit 110 is means for detecting the state of the vehicle 101 and refers to a group of various sensors. The vehicle information detected by the vehicle information detection unit 110 is transferred to the auxiliary turning control unit 151 of the second steering device 150 via the main ECU 130.
As shown in FIG. 2, as the vehicle information detection unit 110, in this embodiment, a vehicle speed detection unit 111 that detects a vehicle speed that is a traveling speed of the vehicle 101 (FIG. 1), and a steering instruction that is a rotation angle of the handle 200. A steering instruction angle detection unit 112 that detects an angle is provided.
The vehicle speed detection unit 111 detects the vehicle speed of the vehicle, for example, based on the output of a sensor (not shown) such as a speed sensor attached to the inside of a transmission included in the vehicle, and outputs the vehicle speed to the ECU 130.
The steering instruction angle detection unit 112 detects the steering angle based on the output of a sensor (not shown) such as a resolver attached to the motor unit included in the first steering device 11 and outputs the detected steering angle to the ECU 130.

<ECU 130>
ECU 130 is a control device that performs overall cooperative control or overall control of vehicle 101 (FIG. 1), and is also referred to as VCU. The auxiliary steering control unit 151 may be provided as a part of the ECU 130, but in this example, is provided as a dedicated ECU different from the ECU 130.

<Control device section 150b>
As shown in FIG. 2, the control unit 150b outputs a drive current corresponding to the auxiliary steering control unit 151 and a motor command signal output by the auxiliary steering control unit 151 to generate a right wheel and a left wheel hub. Motor control devices 170 and 175 for the right and left wheels that drive the auxiliary steering actuators 5 and 5 in the units 1R and 1L are provided.

<Auxiliary turning control unit 151>
As shown in FIGS. 3A and 3B, the auxiliary steering control unit 151, steering angle and [delta] of the wheel determined by the numerical model M of vehicle motion based on the information of the steering instruction angle [delta] _h and the vehicle speed V, the first steering The auxiliary steering actuators 5 and 5 for the left and right wheels are steered by the steering angle δ _{2 of the} additional steering which is a difference from the steering angle δ ₁ of the actual wheel 9 steered by the device 11 (FIG. 2). It is a means to control.
Auxiliary steering control unit 151, an auxiliary turning angle calculation unit 151a having a difference operation unit 151aa for converting the steering angle [delta] ₂ of the additional turning from numerical model M of the vehicle motion becomes the difference, the auxiliary steering the steering angle [delta] ₂ corner calculating unit 151a is calculated and a control command output section 151b configured to output as the motor command signal.

Auxiliary steering control unit 151, the control based on the steering instruction angle [delta] _h and information of the vehicle speed V using the numerical model M, using the following equation (14) to control to improve the responsiveness of the steering, the front wheels Formula (27) is used for the control which uses a tire effectively. Equations (14) and (27) are equations derived using the numerical model M. The auxiliary turning control unit 151 does not include the numerical model M itself, and includes Expressions (14) and (27).

Here, each code | symbol of Formula (14) is defined as follows.
δ ₂ : Steering angle of additional steering as a difference δ _h : Steering instruction angle V: Vehicle speed V _{β = 0} : Vehicle speed when side slip angle β with respect to the steering angle is 0 n: Steering instruction angle and front wheel steering Ratio with angle ζ: Damping rate ω _n : Vibration frequency (natural frequency of vehicle)
α ₁ , α ₂ , α ₃ : Parameter k _r : Tire cornering power per rear wheel l _r : Distance between vehicle center of gravity and rear wheel axle l: Distance between front wheel axle and rear wheel axle (l _f + l _r )
I: Yaw moment of inertia of vehicle s: Complex variable in Laplace transform

<Control to improve steering response>
The auxiliary turning actuator 5 is controlled so as to turn by the steering angle δ ₂ which is the difference obtained by the above equation (14). Thus, by using a mechanical mechanism which structure is to ensure simple and safe, and controls the angle of the left and right wheels in accordance with the vehicle speed V and the steering instruction angle [delta] _h, the response of the vehicle relative to the handle operation of a driver Can be improved.
The reason why the responsiveness is improved by using the equation (14) and the equation (14) will be described below.

With respect to a coordinate system in which the center of gravity G of the vehicle 101 is set as the origin and is fixed to the vehicle, the lateral movement is expressed by Expression (1) with reference to the four-wheel model in FIG. Further, since the cornering forces Y _f1 , Y _f2 , Y _r1 and Y _r2 work as yawing moments around the center of gravity G, the yawing motion around the vertical axis passing through the center of gravity G of the vehicle 101 is expressed by equation (2).
These formulas (1) and (2) are examples of a numerical model of vehicle motion referred to in the claims.

Here, the symbols are defined as follows.
m: Inertial mass of the vehicle
V: Vehicle speed
Y _f1 , Y _f2 , Y _r1 , Y _r2 : Cornering force of each wheel δ: Steering angle of front wheel r: Vehicle yaw angular velocity β: Side slip angle of vehicle center of gravity β _f1 , β _f2 , β _r1 , β _r2 : Each wheel Side slip angle
I: Vehicle yaw moment of inertia l _f : Distance between vehicle center of gravity and front wheel axle l _r : Distance between vehicle center of gravity and rear wheel axle

Here, in order to solve simply, the front and rear two-wheel model of FIG. 5 is considered. The cornering force and the side slip angle β (β _f1 , β _f2 , β _r1 , β _r2 ) of the left and right wheels 9 and 9 are converted into a two-wheel model by equations (3) and (4).

In consideration of Expressions (3) and (4), Expressions (1) and (2) are rewritten into Expressions (5) and (6).
These formulas (5) and (6) are other examples of the numerical model of vehicle motion referred to in the claims. In the case where the two-wheel model, the steering angle [delta] which is obtained from the numerical model of the left and right wheels 9, 9 the same value, and also the steering angle [delta] ₂ additional steered left and right wheels the same.

For equations (5) and (6), β (s), r (s), δ (s), and δ _h (s) are the slip angle β of the vehicle center of gravity, yaw angular velocity r, front wheel steering angle δ, steering When the Laplace transform of the instruction angle δ _h is performed, Expressions (7) and (8) are obtained. Here, K _f and K _r indicate tire cornering power per front wheel and rear wheel.

Solving these equations (7) and (8) with respect to β (s) and r (s), equations (9) and (10) are obtained. Here, ω _n represents the natural frequency of the vehicle response to steering, and ζ represents the attenuation rate of the vehicle response to steering. G _δ ^β (0) is a side slip angle gain constant, which indicates the value of the side slip angle β with respect to the steering angle δ of the front wheels. G _δ ^r (0) is a yaw angular velocity gain constant, and indicates the value of the yaw angular velocity r with respect to the steering angle δ of the front wheels.

Further, the lateral acceleration y ^·· can be expressed by Expression (11) by assuming that β is small.

Expression (12) is obtained by performing Laplace transform on Expression (11) and substituting Expressions (9) and (10). G _δ ^{y ··} (0) is a lateral acceleration gain constant, which indicates the value of the lateral angular velocity y ^·· with respect to the steering angle δ of the front wheels.

From the formulas (9), (10), and (12), the control law of the steering angle of the front wheels that improves the steering responsiveness is shown in the formula (13). At this time, the parameters α ₁ , α ₂ , and α ₃ correspond to the damping rate ζ, the natural frequency ω, and the lateral acceleration y ^·· , respectively, and if the values of α ₁ , α ₂ , and α ₃ are small, Assuming that, the following equation (13) is derived. By appropriately changing the parameters α ₁ , α ₂ , and α ₃ , it is possible to simultaneously improve the responses of the side slip angle β, the yaw angular velocity r, and the lateral acceleration y ^·· .

From equation (13), the control law for determining the steering angle δ ₂ of the additional turning performed using the second steering device 150 is represented by equation (14).

The steering responsiveness can be adjusted by changing the parameters α ₁ , α ₂ , and α ₃ . FIG. 6 shows the analysis results of the yaw angular velocity r and the lateral acceleration y ^··· when the lane change is 2.5 [m] by sine steering of 0.5 [Hz]. Here, α ₁ = −0.2, α ₂ = 0.2, and α ₃ = 1. The curve data shown in black is controlled, and the curve data shown in gray is the result without control. It can be seen that the yaw angular velocity and lateral acceleration rise faster with control, and the steering response is improved.

In this example, since the control formula using the two-wheel model is used, the steering angles of the left and right wheels 9 and 9 are the same. However, when the four-wheel model is used, the left and right wheels 9 and 9 are generally Different values (δ _2L , δ _2R ). In that case, even if the left and right wheels are additionally steered with different values, the steering angle δ ₂ of one additional steering is obtained from the different left and right values, and both left and right are determined by the steering angle δ _2. The wheels 9 and 9 may be additionally steered.

Furthermore, by operating the hub unit with auxiliary steering function independently from the left and right sides according to the following formula using the steering wheel angle and travel speed information, tires in the tire load movement region from the Ackerman steer at extremely low speed to the medium load speed Realize the effective use of the system in a unified manner.
<Control that effectively uses front tires>

By appropriately changing the parameter α, the skid angle corresponding to the load movement due to the acceleration at the medium / high speed is realized while satisfying the Ackermann steer condition at the extremely low speed.
15 and 16 show the analysis results of the turning trajectory and lateral acceleration when steering is performed at a vehicle speed of 40 [km / h] and ramp steps of 0.5 [s] and 120 [deg].
Here, the analysis result set to α = 0.5 is shown. Solid line data is the result of control, and dotted line data is the result of no control. It can be seen that the control increases the outer ring whose load increases during turning and cuts back the inner ring whose load decreases, resulting in a smaller turning radius.

<Action, effect>
The result of the simulation example of the improvement of the steering response has been described. According to the steering system configured as described above, the following advantages can be obtained.
Using the second steering device 150 that is provided in the running to the left and right wheels 9, 9, based on the information of the vehicle speed V and the steering instruction angle [delta] _h, additional steered using equation (14) By calculating the steering angle δ ₂ and controlling the left and right second steering devices 150 at minute angles, the vehicle response to the driver's steering operation is improved without causing the driver to feel danger. can do.
Here, when a control formula using a two-wheel model is used, the steering angles of the left and right wheels 9 and 9 are the same, but the response of the vehicle can be improved without cost by a simple control formula. In addition, when the four-wheel model is used, for example, the vehicle running characteristics are changed by slightly changing the left and right steering angles, and the load applied to each wheel 9, 9 (inner wheel, outer wheel) is changed finely. Control is possible, and further improvement in vehicle motion performance can be expected.
_Further, by calculating the steering angle δ _hb of the additional turning using the above equation (27) and _controlling the left and right second steering devices 150 at minute angles, the performance of the tire can be effectively used. .

The hub unit with an auxiliary turning function as the second steering device 150 has an auxiliary turning axis A different from the rotation axis of the wheel 9 in the hub unit. As shown in FIG. Is held rotatably around the auxiliary turning axis A by mounting shaft portions 16b, 16b provided above and below the outer ring 16. As shown in FIG. 7, the auxiliary turning actuator 5 disposed in the hub unit 1 can be rotated about the auxiliary turning axis A. With this mechanism, the toe angle of the wheels 9 and 9 attached to the hub unit 1 can be freely adjusted with a simple structure without changing the basic structure of the existing vehicle.

Further, as shown in FIG. 8, the auxiliary steering actuator 5 has a reverse input prevention function 25b, and the maximum turning angle of the hub unit 1 with the auxiliary turning function is limited to ± several degrees necessary for the correction operation. Therefore, when the power supply of one of the motor control devices 170 and 175 shown in FIG. 3B is lost, the control of the other motor control device 170 and 175 is stopped, so that the hub unit The turning angle is fixed, and the driver can safely move the vehicle to a safe place such as the road shoulder using the steering wheel. Therefore, a mechanism for safety measures in the event of system failure can be omitted or simplified.

<Specific Configuration Example of Second Steering Device 150>
As shown in FIGS. 1 and 9, the second steering device 150 can steer the left and right wheels 9 and 9 independently. A right wheel hub unit 1 </ b> R (FIG. 2) and a left wheel hub unit 1 </ b> L (FIG. 2) are provided as a mechanism portion 150 a serving as a hub unit with an auxiliary turning function of the second steering device 150. The right wheel hub unit 1 </ b> R and the left wheel hub unit 1 </ b> L steer the wheels 9 and 9 by the auxiliary steering actuator 5 (FIG. 7) provided in the tire housing 105.

The mechanism 150a serving as a hub unit with an auxiliary turning function of the second steering device 150 includes the right wheel hub unit 1R and the left wheel hub unit 1L as described above, and these right wheel hub unit 1R and left wheel hub unit 1L. Are configured as a hub unit 1 with an auxiliary turning function shown in FIG.
As shown in FIG. 7, the hub unit 1 includes a hub unit main body 2, a unit support member 3, a rotation allowable support component 4, and an auxiliary steering actuator 5. The unit support member 3 is provided integrally with the knuckle which is the underbody frame component 6.

As shown in FIG. 11, the actuator main body 7 of the auxiliary steering actuator 5 is provided on the inboard side of the unit support member 3, and the hub unit main body 2 is provided on the outboard side of the unit support member 3. In a state where the hub unit 1 (FIG. 7) is mounted on the vehicle, the vehicle width direction outer side of the vehicle is referred to as an outboard side, and the vehicle width direction center side of the vehicle is referred to as an inboard side.
As shown in FIGS. 8 and 10, the hub unit main body 2 and the actuator main body 7 are connected by a joint portion 8. Usually, the joint portion 8 is provided with a boot (not shown) for waterproofing and dustproofing.

As shown in FIG. 7, the hub unit main body 2 is attached to the unit support member 3 via the rotation-allowing support parts 4 and 4 at two upper and lower positions so as to be rotatable around the auxiliary turning axis A extending in the vertical direction. It is supported. The auxiliary turning axis A is an axis different from the rotation axis O of the wheel 9 and is also different from the kingpin axis that performs steering of the first steering device. In a normal vehicle, the kingpin angle is set to 10 to 20 degrees for the purpose of improving the straight running stability of the vehicle traveling. However, the hub unit 1 of this embodiment has an angle (axis) different from the kingpin angle. It has a steering shaft. The wheel 9 includes a wheel 9a and a tire 9b.

As shown in FIG. 1, the hub unit 1 (FIG. 7) of this embodiment is added to the steering of the left and right wheels 9, 9 as front wheels by the first steering device 11, and ± 5 degrees or less for each of the left and right wheels individually. Is provided integrally with the underbody frame component 6 of the suspension device 12 as a mechanism for turning the angle (about ± 5 deg). The first steering device 11 is of a rack and pinion type, but any type of steering device may be used. The suspension device 12 uses, for example, a strut suspension mechanism that directly fixes the shock absorber to the underbody frame component 6, but a multi-link suspension mechanism or other suspension mechanisms may be applied.

<About hub unit body 2>
As shown in FIG. 7, the hub unit main body 2 includes a hub bearing 15 for supporting the wheel 9, an outer ring 16, and an arm portion 17 (FIG. 10) that is a steering force receiving portion described later.
As shown in FIG. 14, the hub bearing 15 includes an inner ring 18, an outer ring 19, and rolling elements 20 such as balls interposed between the inner and outer rings 18, 19. 7).

In the illustrated example, the hub bearing 15 is an angular ball bearing in which the outer ring 19 is a fixed ring, the inner ring 18 is a rotating ring, and the rolling elements 20 are in a double row. The inner ring 18 includes a hub ring portion 18a having a hub flange 18aa and constituting a race surface on the outboard side, and an inner ring portion 18b constituting a race surface on the inboard side. As shown in FIG. 7, the wheel 9a of the wheel 9 is bolted to the hub flange 18aa so as to overlap the brake rotor 21a. The inner ring 18 rotates around the rotation axis O.

As shown in FIG. 14, the outer ring 16 includes an annular portion 16 a fitted to the outer peripheral surface of the outer ring 19, and a trunnion shaft-like mounting shaft portion provided so as to protrude vertically from the outer periphery of the annular portion 16 a. 16b, 16b. Each attachment shaft portion 16b is provided coaxially with the auxiliary turning shaft center A.
As shown in FIG. 8, the brake 21 includes a brake rotor 21a and a brake caliper 21b. The brake caliper 21b is attached to two upper and lower brake caliper attachment portions 22 (FIG. 12) formed integrally with the outer ring 19 so as to project into an arm shape.

<About rotation-supporting support parts and unit support members>
As shown in FIG. 14, each rotation-allowing support component 4 is composed of a rolling bearing. In this example, a tapered roller bearing is applied as the rolling bearing. The rolling bearing includes an inner ring 4a fitted to the outer periphery of the mounting shaft portion 16b, an outer ring 4b fitted to the unit support member 3, and a plurality of rolling elements 4c interposed between the inner and outer rings 4a and 4b.

The unit support member 3 includes a unit support member main body 3A and a unit support member combined body 3B. A substantially ring-shaped unit support member assembly 3B is detachably fixed to the end of the unit support member main body 3A on the outboard side. Partial concave spherical fitting hole forming portions 3a are respectively formed on the upper and lower portions of the side surface of the inboard side of the unit support member assembly 3B.

As shown in FIGS. 13 and 14, partial concave spherical fitting hole forming portions 3Aa are respectively formed on the upper and lower portions of the outboard side end of the unit support member main body 3A. As shown in FIG. 10, the unit support member combined body 3B is fixed to the outboard side end of the unit support member main body 3A, and the fitting hole forming portions 3a and 3Aa (FIG. 13) are combined with each other for each upper and lower portion. As a result, a fitting hole is formed continuously around the entire circumference. The outer ring 4b is fitted in this fitting hole. In FIG. 10, the unit support member 3 is indicated by a one-dot chain line.

As shown in FIG. 14, each mounting shaft portion 16b of the outer ring 16 is formed with a female screw portion extending in the radial direction, and is provided with a bolt 23 that is screwed into the female screw portion. A disc-like pressing member 24 is interposed on the end surface of the inner ring 4a, and a preload is applied to each rotation-allowing support component 4 by applying a pressing force to the end surface of the inner ring 4a by a bolt 23 that is screwed into the female screw portion. Giving. Thereby, the rigidity of each rotation permission support component 4 can be improved. Even when the weight of the vehicle acts on the hub unit 1, the initial preload is set so as not to escape. Note that the rolling bearing of the rotation-allowing support component 4 is not limited to the tapered roller bearing, and an angular ball bearing can be used depending on use conditions such as a maximum load. In such a case as well, a preload can be applied in the same manner as described above.

As shown in FIG. 8, the arm portion 17 is a portion serving as an action point for applying a steering force to the outer ring 19 of the hub bearing 15, and is integrated with a part of the outer periphery of the annular portion 16 a or a part of the outer periphery of the outer ring 19. Protrusively. The arm portion 17 is rotatably connected to the linear motion output portion 25 a of the auxiliary steering actuator 5 via the joint portion 8. As a result, the linear output part 25a of the auxiliary turning actuator 5 advances and retreats, whereby the hub unit body 2 rotates around the auxiliary turning axis A (FIG. 7), that is, is turned.

<About the auxiliary steering actuator 5>
As shown in FIG. 10, the auxiliary turning actuator 5 has an actuator body 7 that drives the hub unit body 2 to rotate about the auxiliary turning axis A (FIG. 7).
As shown in FIG. 8, the actuator body 7 converts the motor 26, the speed reducer 27 that decelerates the rotation of the motor 26, and the forward / reverse rotation output of the speed reducer 27 into the reciprocating linear motion of the linear motion output unit 25a. And a linear motion mechanism 25. The motor 26 is, for example, a permanent magnet type synchronous motor, but may be a DC motor or an induction motor.

The reduction gear 27 can use a wrapping type transmission mechanism such as a belt transmission mechanism or a gear train, and a belt transmission mechanism is used in the example of FIG. The reducer 27 includes a drive pulley 27a, a driven pulley 27b, and a belt 27c. A drive pulley 27 a is coupled to the motor shaft of the motor 26, and a driven pulley 27 b is provided in the linear motion mechanism 25. The driven pulley 27b is disposed in parallel to the motor shaft. The driving force of the motor 26 is transmitted from the drive pulley 27a to the driven pulley 27b via the belt 27c. The drive pulley 27a, the driven pulley 27b, and the belt 27c constitute a winding-type speed reducer 27.

As the linear motion mechanism 25, a feed screw mechanism such as a slide screw or a ball screw, or a rack and pinion mechanism can be used. In this example, a trapezoidal screw slide screw is used as the feed screw mechanism that also serves as the reverse input prevention mechanism 25b. The feed screw mechanism used is used. Since the linear motion mechanism 25 includes a feed screw mechanism using a sliding screw of the trapezoidal screw as the reverse input prevention mechanism 25b, the effect of preventing reverse input from the tire 9b can be enhanced. The actuator body 7 including the motor 26, the speed reducer 27, and the linear motion mechanism 25 is assembled as a semi-assembly and is detachably attached to the case 6b with bolts or the like. A mechanism that directly transmits the driving force of the motor 26 to the linear motion mechanism 25 without using a reduction gear is also possible. Further, the reverse input preventing mechanism 25b may be a worm gear or the like, and the linear motion mechanism 25 may have a structure that does not have a reverse input blocking function such as a ball screw.

The case 6b is integrally formed with the unit support member main body 3A as a part of the unit support member 3. The case 6 b is formed in a bottomed cylindrical shape, and is provided with a motor housing portion that supports the motor 26 and a linear motion mechanism housing portion that supports the linear motion mechanism 25. A fitting hole for supporting the motor 26 at a predetermined position in the case is formed in the motor housing portion. The linear motion mechanism accommodating portion is formed with a fitting hole for supporting the linear motion mechanism 25 at a predetermined position in the case, a through hole for allowing the linear motion output portion 25a to advance and retreat.

As shown in FIG. 10, the unit support member main body 3A includes the case 6b, a shock absorber mounting portion 6c serving as a shock absorber mounting portion, and a steering device coupling serving as a coupling portion of the first steering device 11 (FIG. 8). Part 6d. The shock absorber mounting portion 6c and the steering device coupling portion 6d are also integrally formed with the unit support member main body 3A. A shock absorber mounting portion 6c is formed on the upper portion of the outer surface portion of the unit support member main body 3A so as to protrude. A steering device coupling portion 6d is formed on the side surface portion of the outer surface portion of the unit support member main body 3A so as to protrude.
Although an example in which the unit support member 3 is integrated with the knuckle has been shown, a unit support member manufactured as a separate part may be integrally fixed to the knuckle.

Incidentally, the embodiment is means for instructing the steering instruction angle [delta] _h of the first steering device 11 has been explained the case is a handle 200, means for instructing steering instruction angle [delta] _h, the automatic operation device (Fig. (Not shown). Further, the first steering device 11 may have a structure in which the left and right wheels 9 and 9 serving as front wheels are mechanically interlocked, and the steering that drives a steering actuator (not shown) by operating the handle 200 is used. It may be a by-wire system.

As described above, the preferred embodiments have been described with reference to the drawings, but various additions, modifications, and deletions are possible without departing from the spirit of the present invention. Therefore, such a thing is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 2 ... Hub unit main body, 3 ... Unit support member, 5 ... Actuator for auxiliary steering, 6 ... Suspension frame component, 9 ... Wheel, 11 ... First steering device, 12 ... Suspension device, 15 ... Hub bearing, 25b DESCRIPTION OF SYMBOLS ... Reverse input prevention mechanism, 100 ... Steering system, 101 ... Vehicle, 105 ... Tire housing, 110 ... Vehicle information detection part, 150 ... Second steering device, 150a ... Mechanism part, 150b ... Control device part, 151 ... Auxiliary rotation Rudder control unit, 151a ... auxiliary turning angle calculation unit, 151b ... control command output unit, 170, 175 ... motor control device, 200 ... handle

Claims (8)

The left and right wheels that are the front wheels of the vehicle are mechanically interlocked, and the left and right wheels that are the front wheels of the vehicle according to the steering instruction angle by the rotation of the steering wheel or the electric signal are A first steering device for steering by changing the angle of the rotating frame parts;
A second steering device for individually turning the left and right wheels by changing an angle of the wheel with respect to the underbody frame component by driving an auxiliary steering actuator provided for each of the left and right wheels;
A vehicle information detection unit for detecting vehicle information including a vehicle speed of the vehicle and the steering instruction angle;
A steering system comprising:
The second steering device includes a steering angle of the front wheel determined by a numerical model of vehicle motion based on the steering instruction angle and the vehicle speed information, and an actual steering angle of the front wheel steered by the first steering device. An auxiliary turning control unit that controls the auxiliary turning actuator so as to turn only the steering angle δ _{2 of the} additional turning that is the difference between
A steering system characterized by that. 2. The steering system according to claim 1, wherein a two-wheel model is used for the control to obtain and steer the steering angle δ ₂ of the additional turning by the auxiliary turning control unit of the second steering device. Steering system using formula.

here,
δ ₂ : Steering angle of additional steering as a difference δ _h : Steering instruction angle V: Vehicle speed V _{β = 0} : Vehicle speed when side slip angle β with respect to the steering angle is 0 n: Steering instruction angle and front wheel steering Ratio to angle ζ: Damping rate ω _n : Natural frequency (vehicle natural frequency)
α ₁ , α ₂ , α ₃ : Parameter k _r : Tire cornering power per rear wheel l _r : Distance between vehicle center of gravity and rear wheel axle l: Distance between front wheel axle and rear wheel axle (l _f + l _r )
I: Yaw moment of inertia of vehicle s: Complex variable in Laplace transform 2. The steering system according to claim 1, wherein the auxiliary steering control unit of the second steering device obtains a steering angle of the additional steering and performs steering to control the steering.

2. The steering system according to claim 1, wherein the auxiliary turning control unit is configured to determine a left and right steering angle of the front wheel obtained from the numerical model of the vehicle motion and an actual front wheel steered by the first steering device. A steering system that controls the auxiliary steering actuator so as to steer only an individual steering angle (δ _2L , δ _2R ) of additional steering that is a difference between each of the left and right steering angles. 5. The steering system according to claim 1, wherein the second steering device is connected to a hub unit main body having a hub bearing for attaching a wheel and the underbody frame component or a foot. A unit support member configured as a part of the rotating frame part,
The hub unit body is supported by the unit support member via a rotation-allowing support component so as to be rotatable around an auxiliary turning axis extending in the vertical direction, and the auxiliary turning axis is driven by driving the auxiliary turning actuator. A steering system that can be rotated around. 6. The steering system according to claim 1, wherein the second steering device is connected to a hub unit main body having a hub bearing for attaching a wheel and the underbody frame component or a foot. A mechanism part having a unit support member configured as a part of a rotating frame part and supporting the hub unit main body so that the angle of the hub unit body can be changed with respect to the undercarriage frame part; the auxiliary turning control part; and the auxiliary turning part A steering system, which is a hub unit with an auxiliary turning function, comprising: a control unit having a motor control unit that outputs a drive current according to a motor command signal output from the control unit to drive the auxiliary steering actuator. The steering system according to any one of claims 1 to 6, wherein the auxiliary steering actuator of the second steering device includes a reverse input prevention mechanism. A vehicle equipped with the steering system according to any one of claims 1 to 7.

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