JP5125403B2 - Vehicle steering system - Google Patents

Description

  The present invention relates to a vehicle steering apparatus having a so-called steer-by-wire configuration that includes a steering mechanism that is steered by a driver and a steering mechanism that is separated from the steering mechanism and steers steered wheels.

As this type of vehicle steering device, for example, the king pins of the left and right front wheels equipped with special steering motors are linked by link members that connect the tips of the respective knuckle arms, for example, one steering motor is in a failed state. When this happens, a vehicle steering device has been proposed in which the front wheel corresponding to the steering motor is steered by the rotation of the other steering motor transmitted through a link member (see, for example, Patent Document 1). .
Japanese Patent Laying-Open No. 2003-170849 (first page, FIG. 1)

  However, in the conventional example described in Patent Document 1, when one steering motor is in a failed state, the front wheel corresponding to this steering motor is steered by the rotation of the other steering motor via the link member. Therefore, even when an abnormality occurs in one steering motor, it is possible to continue the steering control of the steered wheels on the side of the steering motor that has become abnormal due to the other steering motor. Since the tip of the knuckle is connected by the link member, there is an unsolved problem that the left and right steering motors cannot be individually controlled to independently control the slip angle of the steered wheels.

  Therefore, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and can control the slip angle of the left and right steered wheels independently, and abnormally detects one of the left and right steered actuators. An object of the present invention is to provide a vehicle steering apparatus that can ensure a fail-safe operation when the above occurs.

In order to achieve the above object, a vehicle steering apparatus according to claim 1 includes a steering mechanism that is steered by a driver, and a steering mechanism that is steered from a steered wheel by being separated from the steering mechanism. The steering mechanism is movable while providing a pair of steered parts having a steered actuator that individually imparts a steered force to the left and right steered wheels, and a movable resistance that connects the pair of steered parts. at least a connecting member movable range is restricted in said connecting member is characterized that you have configured the movable resistor to generate at least one of viscosity and friction.

  Further, the vehicle steering apparatus according to claim 2 includes a steering mechanism that is steered by a driver, and a steering mechanism that steers the steered wheels by being separated from the steering mechanism, and the steering mechanism includes: A pair of steered portions having a steered actuator that individually imparts a steered force to the left and right steered wheels and a movable resistance that connects the pair of steered portions while being movable, and the movable range is restricted. And a steering control means for independently controlling the steering actuators of the pair of steering units based on a lateral force acting on the steered wheels.

  Furthermore, the vehicle steering apparatus according to claim 3 is the invention according to claim 2, wherein the turning control means includes a lateral force detecting means for detecting a lateral force acting on the steered wheel, and a wheel of the steered wheel. Wheel speed detection means for detecting speed, and steering control for independently feedback control of the slip angle of the steered wheel based on the lateral force detected by the lateral force detection means and the wheel speed detected by the wheel speed detection means It is characterized by having a part.

Furthermore, a steering apparatus for a vehicle according to claim 4 is the invention according to claim 3, wherein the lateral force detecting means and the wheel speed detection means, you are characterized by being built into the hub of the wheel.

  According to the present invention, the steering mechanism includes a pair of steered portions having a steered actuator that individually imparts a steered force to the left and right steered wheels, and a movable resistance that connects the pair of steered portions. At least a connecting member that is movable while restricting the movable range, so that it is possible to individually control the steering angle for the left and right steered wheels, and an abnormality occurs in one of the steered actuators. Even if it does, the effect that the steered wheel by the side of the steered actuator in which abnormality generate | occur | produced via the connection member with a normal steered actuator can be steered is acquired.

  In addition, by independently controlling the steering actuators of the left and right steered parts based on the lateral force acting on the steered wheels and the wheel speed of the steered wheels, the slip angles of both steered wheels can be individually controlled without using separate actuators. Thus, the fuel efficiency can be improved, and the performance of the vehicle can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a steer-by-wire type vehicle steering device. The vehicle steering device 1 is a steering mechanism that is steered by a driver. 2 and a steered mechanism 4 that steers steered wheels 3FL and 3FR that are separated from the steering mechanism 2 and are front and right wheels.

The steering mechanism 2 includes a steering shaft 22 on which a steering wheel 21 to be steered by a driver is mounted, and a steering reaction force generator 24 that generates a steering reaction force by an electric motor 23 built in the steering shaft 22. .
Further, the steering mechanism 4 is connected to the tie rods 41L and 41R having one ends connected to the knuckle arms 32L and 32R connected to the hubs 31L and 31R of the steered wheels 3FL and 3FR, and to the other ends of the tie rods 41L and 41R. Pitman arms 42L and 42R, pitman actuators 43L and 43R as turning actuators for swinging and driving the pitman arms 42L and 42R, and a connecting member 44 for connecting the pitman arms 42L and 42R. Here, the tie rods 41L and 41R, the pitman arms 42L and 42R, and the pitman actuators 43L and 43R constitute a pair of steered portions.

  As shown in FIG. 2, each of the pitman actuators 43L and 43R is arranged at the upper end of the housing 52, a housing 52 fixed to the vehicle body side member 51, a planetary gear speed reduction mechanism 53 incorporated in the housing 52, and the housing 52. And an electric motor 54L, 54R connected to the input side of the planetary gear type reduction mechanism 53. The pitman arms 42L, 42R are connected to the output shaft of the planetary gear type reduction mechanism 53. Yes.

  The planetary gear type reduction mechanism 53 is configured to output a large torque with a reduction ratio of about 1/200 in a compact configuration by combining a normal 2KH type planetary reduction device 55 and a 3K type planetary reduction device 56. Has been. Specifically, it has a center shaft 57 connected to the output shaft 54a of the electric motors 54L and 54R, a normal 2KH type planetary reduction gear 55 is disposed on the lower end side of the center shaft 57, and 3K on the upper end side. A type planetary speed reducer 56 is provided.

  A normal 2KH type planetary reduction gear 55 includes a sun gear 61 connected to a central shaft 57 serving as an input unit, a first pinion gear 63 supported by a first pinion carrier 62 serving as an output unit, and meshing with the sun gear 61, The first ring gear 64 is fixed to the housing 52 that meshes with the first pinion gear 63. When the central shaft 57 rotates, the first ring gear 64 is fixed to the housing 52, so that the first pinion gear 63 revolves while rotating according to the gear ratio between the sun gear 61 and the first ring gear 64, and the first A deceleration output is obtained from the pinion carrier 62.

  The 3K-type planetary speed reducer 56 includes a sun gear 71 connected to the first pinion carrier 62, a second pinion gear 72 that meshes between the sun gear 71 and the first ring gear 64 described above, and an elastic key 73 to the second pinion gear 72. A third pinion gear 74 having a larger number of teeth than the second pinion gear 72 integrally connected thereto, a pinion carrier 75 supporting the third pinion gear 74, and a rotatable freely meshing with the third pinion gear 74 The second ring gear 76 and an output shaft 77 fixed to the second ring gear 76 are configured. Here, the output shaft 77 includes a cylindrical portion 77 a rotatably supported by a rolling bearing 78 on the upper end portion of the housing 52, and a part integrally connected to the lower end of the cylindrical portion 77 a outward from the housing 52. The horizontal plate portion 77b is protruded, and the lower surface of the horizontal plate portion 77b is screwed to the second ring gear 76, and the pitman arm 42L and the upper surface of the plate portion protruding from the housing 52 of the horizontal plate portion 77b. 42R is screwed.

  The connecting member 44 has connecting rods 81L and 81R, one end of which is rotatably connected to the tip of each of the pitman arms 42L and 42R, and a relay rod that is extendable and connects the connecting rods 81L and 81R and whose expansion range is restricted. 82. The relay rod 82 is connected to the other end of the connecting rod 81R and the other end of the connecting rod 81L so as to be slidable with a predetermined sliding resistance. The sliding shaft portion 84 is provided. The outer cylinder portion 83 includes a large-diameter cylinder portion 83a on the connecting rod 81R side and a small-diameter cylinder portion 83b on the connecting rod 81L side. The sliding shaft portion 84 is fitted so as to be in sliding contact with a predetermined frictional resistance within the large diameter shaft portion 84a that engages in the large diameter tube portion 83a of the outer tube portion 83 and the small diameter tube portion 83b of the outer tube portion 83. The small-diameter shaft portion 84b is connected to the connecting rod 81L. Here, as shown in FIG. 1, the sliding resistance between the small-diameter cylindrical portion 83b of the outer cylindrical portion 83 and the small-diameter shaft portion 84b of the sliding shaft portion 84 causes the small-diameter cylindrical portion 83b and the small-diameter shaft portion 84b to move. They are fitted, O-rings are inserted into either of them, high-viscosity grease is applied between them, or an elastic body such as a spring or rubber is disposed on either of them, and the other slide It can be applied by pressing on the moving surface. In addition, the expansion / contraction range of the sliding shaft portion 84 with respect to the outer cylinder portion 83 is regulated to be a length capable of absorbing the difference between the controllable slip angles of the left and right steered wheels 3FL and 3FR, and restricts the expansion / contraction range. As described above, the axial length of the large diameter portion 83 a of the outer cylinder portion 83 and the axial length of the large diameter shaft portion 84 a of the sliding shaft portion 84 are set.

  Further, as shown in FIG. 3, each steered wheel 3FL, 3FR is composed of a hub body 31a and an inner cylinder portion 31b extending from the hub body 31a toward the inside of the vehicle. Balls as rolling elements held by the retainers 31e on both ends in the axial direction between the inner cylinder part 31b of the hubs 31L and 31R and the outer cylinder part 31d attached to the knuckle 31c constituting the suspension device A double row angular contact ball bearing structure is formed with 31f interposed.

The steerable wheels 3FL, with axial load or lateral force is detected by the lateral force sensor 91, the rotational speed or wheel speed of the inner cylindrical portion 31b of the hub 31L and 31R Vw _FL and Vw _FR is a wheel speed sensor acting on 3FR 92.
Here, as shown in FIG. 4, the lateral force sensor 91 calculates the revolution speed N of the ball 31f outside the vehicle acting on the vehicle, and calculates the axial load, ie, lateral force, of the vehicle from the calculated revolution speed N. It is configured. The lateral force sensor 91 is fixed to the outer cylinder portion 31d so as to face the first encoder 91a and the first encoder 91a in which N poles and S poles are alternately formed in the circumferential direction formed in the cage 31e. A pair of magnetic sensors 91b and 91c separated by a predetermined distance D in the arranged tangential direction and separated by an angle (center angle pitch) θ in the circumferential direction, and pulse signals detected by these magnetic sensors 91b and 91c are signal processed. In addition, a signal processing circuit 91d that performs a predetermined calculation process to calculate the revolution speed N and calculates lateral forces Fy _FL and Fy _FR acting on the wheels from the calculated revolution speed N is provided.

The signal processing circuit 91d detects a delay time T from one rising point of the pulse signals input from the magnetic sensors 91b and 91c to the other rising point, and a distance between the detected delay time T and the magnetic sensors 91b and 91c. The revolution speed N is calculated by performing the following equation (1) or (2) based on D or the angle θ.
N = (60 / πT) × sin ⁻¹ (D / 2R) (1)
N = (30 / π) × (θ / T) (2)
Here, R is a rotation radius from the rotation center of the encoder 91a to the portion where the detection units of the magnetic sensors 91b and 91c are opposed to each other.

Note that the distance D and the angle θ have the relationship of the following equation (3).
θ = 2sin ⁻¹ (D / 2R) (3)
Thus, since the revolution speed N of the ball 31f is calculated by calculating the delay time T between the pulse signals of the magnetic sensors 91b and 91c, the magnetic characteristic of the encoder 91a changes, that is, the N pole and the S pole. The revolution speed N can be calculated every time the boundary between and passes the magnetic sensors 91b and 91c. Since there are many boundaries on one side of the encoder 91a, the revolution speed N of each ball 31f can be obtained in substantially real time. Further, since the distance D between the magnetic sensors 91b and 91c does not change regardless of the rotation of the encoder 91a, the revolution speed N can be accurately detected regardless of the manufacturing error or the assembly error of the encoder 91a. it can.

Thus, by calculating the revolution speed N of each ball 31f by the signal processing circuit 91d, the axial load acting on the rolling bearing unit, which acts between the wheel 35 and the knuckle 31c constituting the steered wheels 3FL and 3FR, is applied. Lateral force can be detected.
That is, since the inner cylindrical portion 31b and the outer cylindrical portion 31d and the ball 31f have a double-row angular ball bearing configuration, when an axial load is applied thereto, the contact angle of each ball 31f changes. For example, as shown by an arrow α in FIG. 3, when an inward axial load is applied, the contact angle of the balls 31f in the outer (left side in FIG. 3) row increases. As is well known in the field of rolling bearings, the revolution speed of the balls 31f constituting the angular ball bearings changes as the contact angle of the balls 31f changes. Specifically, with respect to the outer row that supports the axial load, the revolution speed of the balls 31f increases as the axial load increases. Therefore, the axial load applied to the rolling bearing unit can be obtained by measuring the change in the revolution speed.

For example, FIG. 5 shows the relationship between the magnitude of the axial load and the revolution speed of the ball 31f when the axial load in the direction of the arrow α is added to the back-row combined type double row rolling bearing unit having the structure shown in FIG. Showing the relationship.
The solid line a in FIG. 5 represents the relationship between the axial load and the revolution speed of the balls 31f in the outer (left side of FIG. 3) line, and the broken line b represents the relationship between the axial load and the revolution speed of the balls 31f in the inner row. Represents each. The radial load was constant. As is apparent from the characteristic curve of FIG. 5, the magnitude of the axial load and the revolution speed N of each of the balls 31f are in a substantially proportional relationship with respect to the balls 31f on the side receiving the axial load. Therefore, by measuring the revolution speed N of each ball 31f, the axial load can be calculated with reference to the characteristic curve of FIG. Here, the characteristic curve of FIG. 5 can be obtained by experiment or by simulation. By storing the characteristic curve of FIG. 5 in the signal processing circuit 91d as a lateral force calculation map, the lateral forces Fy _FL and Fy _FR acting on the steered wheels 3FL and 3FR can be calculated from the revolution speed N. Further, the lateral force sensor 91 having the above configuration is also provided in the rear wheels 3RL and 3RR, and calculates the lateral forces Fy _RL and Fy _RR of the rear wheels 3RL and 3RR.

Further, the wheel speed sensor 92 is provided with a second encoder 92a similar to the first encoder 91a described above on the vehicle inner end face of the inner cylinder portion 31b of the hubs 31L and 31R, and is opposed to the second encoder 92a. By providing one magnetic sensor 92b, the number of pulse signals per short time output from the magnetic sensor 92b is counted, or the time from the rising point of one pulse signal to the rising point of the next pulse signal is counted. By measuring, the wheel speeds Vw _FL and Vw _FR are calculated.

The vehicle integrated control in which the lateral forces Fy _{FL to} Fy _RR detected by the lateral force sensor 91 provided on each wheel 3FL to 3RR and the wheel speeds Vw _FL and Vw _FR detected by the wheel speed sensor 92 control the vehicle control system. In addition to being input to the unit 100, the yaw rate, the accelerator opening, the brake depression amount, the engine information, and the like representing other traveling conditions of the vehicle are also input to the vehicle integrated control unit 100. 101 is connected via a network such as an in-vehicle LAN, and information required by the steer-by-wire control unit 101 is transmitted from the vehicle integrated control unit 100.

As shown in FIG. 6, the steer-by-wire control unit 101 is a reaction force control that controls the reaction force actuator 23 based on the lateral force Fy _FL Fy _FR acting on the steered wheels 3FL and 3FR read from the vehicle integrated control unit 100. The yaw rate differential value γ ′ and lateral acceleration Gy are estimated according to the simple vehicle model based on the lateral forces Fy _FL , Fy _FR , Fy _RL and Fy _RR acting on the front and rear four wheels read from the unit 102 and the vehicle integrated control unit 100. Vehicle behavior estimation unit 103, and a slip for estimating the slip angle θ of the vehicle body based on the yaw rate differential value γ ′ estimated by the vehicle behavior estimation unit 103, the lateral acceleration Gy, and the wheel speeds Vw _FL and Vw _FR of the non-driven wheels an angular estimation unit 104, the steered wheels 3FL, lateral force Fy _FL and Fy _FR wheel speed Vw _FL and Vw _FR and Sri acting 3FR The road surface friction coefficient estimating unit 105 that estimates the road surface friction coefficient μ based on the steering angle θ, and the steering angle δ and the road surface friction coefficient estimating unit that are output from the steering angle sensor 25 that detects the steering angle δ by the reaction force actuator 23. Based on the road surface friction coefficient μ output from 105, a reference model 106 for outputting a reference behavior target value composed of a target yaw rate differential value γt ′ and a target lateral acceleration Gyt according to a predetermined reference model, and output from the reference model 106 The reference behavior target value, the slip angle θ output from the slip angle estimation unit 104, the road surface friction coefficient μ output from the road surface friction coefficient estimation unit 105, and the yaw rate differential value γ ′ output from the vehicle behavior estimation unit 103 Further, stabilization control is performed based on the lateral acceleration Gy and the wheel speeds Vw _FL and Vw _FR, and the turning angle command value δt is output to the adders 108L and 108R. And a stabilizing controller 107 to be applied.

Here, the reaction force control unit 102 calculates a steering reaction force to be applied to the steering wheel 21 based on the lateral forces Fy _FL and Fy _FR acting on the steered wheels 3FL and 3FR read from the vehicle integrated control unit 100, A torque command value corresponding to the steering reaction force is output to the reaction force actuator 23, and the reaction force actuator 23 is controlled.
Further, the vehicle behavior estimation unit 103 considers the vehicle as a simple four-wheel model, and a simple four-wheel model shown in FIG. 7 is considered when the lateral forces Fy _{FL to} Fy _RR related to the vehicle are represented.

The equation of motion at this time is
M · Gy = Fy _FL + Fy _FR + Fy _RL + Fy _RR (1)
I · γ ′ = Fy _FL × L _FL + Fy _FR × L _FR + Fy _RL × L _RL + Fy _RR × L _RR (2)
Here, M is the weight of the vehicle body, Gy is the lateral acceleration, I is the vehicle inertia moment, and γ ′ is the yaw rate differential value.

From this equation (1), the lateral acceleration Gy is Gy = (Fy _FL + Fy _FR + Fy _RL + Fy _RR ) / M (3)
The yaw rate differential value γ ′ is calculated by
γ ′ = {(L _F (Fy _FL + Fy _FR ) −L _R (Fy _RL + Fy _RR )} / I (4)
Is calculated by Here, L _F is the distance from the center of gravity to the axis connecting the front wheels, and L _R is the distance from the center of gravity to the axis connecting the rear wheels.

Therefore, if the lateral forces Fy _FL , Fy _FR , Fy _RL and Fy _{RR of} each wheel are known, the lateral acceleration Gy and the yaw rate differential value γ ′ can be calculated. Of these, the yaw rate differential value γ ′ should be measured directly. Further, these values change before the actual yaw rate and actual lateral acceleration in a vehicle equipped with an actual suspension. That is, a change in behavior can be predicted before the behavior of the vehicle changes, and since advanced control is possible, it can be referred to as a yaw rate differential value and a pre-read value of lateral acceleration. These yaw rate differential values γ ′ And the lateral acceleration Gy are output to the slip angle estimation unit 104 and a stabilization controller 107 described later.

Further, the slip angle estimation unit 104 calculates the vehicle body slip angle θ based on the yaw rate differential value γ ′ and the lateral acceleration Gy calculated by the vehicle behavior estimation unit 103.
For calculating the vehicle body slip angle θ, first, the yaw rate differential value γ ′ is integrated as shown in the following equation (5) to calculate the yaw rate γ, and the wheel speeds Vw of the steered wheels 3FL, 3FR to be non-driven wheels are calculated. _The vehicle speed V (= (Vw _FL + Vw _FR ) / 2)) is calculated by calculating the average value of _FL and Vw _FR .

γ = ∫ {(L _F (Fy _FL + Fy _FR ) −L _R (Fy _RL + Fy _RR ) / I)} dt (5)
Here, the yaw rate γ is not limited to the calculation according to the above equation (5), and the yaw rate detected by the yaw rate sensor provided in the vehicle may be applied.
Next, based on the calculated yaw rate γ, vehicle speed V and lateral acceleration Gy, the following equation (6) is calculated to calculate the vehicle body slip angle θ.

θ = ∫ (Gy / V−γ) dt (6)
The slip angle θ obtained in this manner is shifted in value due to drift at the time of integration, but is corrected using the relationship among the lateral forces Fy _FL and Fy _FR , the road surface friction coefficient μ, and the slip angle θ. It is preferable.
Further, the road surface friction coefficient estimating unit 105 calculates the following equation (7) based on the lateral forces Fy _FL and Fy _{FR of} the steered wheels 3FL and 3FR and the slip angle θ estimated by the slip angle estimating unit 104, thereby calculating the road surface. Estimate the coefficient of friction μ.

μ = {(Fy _FL + Fy _FR ) / 2} / (Kf × θ) (7)
Here, Kf is a cornering power constant determined from tire specifications.
Further, in the reference model 106, a reference behavior value serving as a reference for the turning angle is calculated based on the input steering angle δ. From the road surface friction coefficient estimation unit 105, the road surface friction coefficient μ is supplied. The normative model itself, such as a standard that keeps the slip angle θ of the vehicle body small in order to prevent vehicle spin, without trying to obtain a large yaw rate on road surfaces with low friction coefficient such as snowy roads, frozen roads, and rainy roads Is changed according to the road surface condition, and a standard behavior value composed of a more stable target yaw rate differential value γt ′ and a target lateral acceleration Gyt is calculated.

  Further, in the stabilization controller 107, a normative behavior value composed of the target yaw rate differential value γt ′ and the target lateral acceleration Gyt output from the normative model 106, and a yaw rate differential value that is a look-ahead value estimated by the vehicle behavior estimation unit 103 is obtained. A turning angle command value δt is calculated based on γ ′ and lateral acceleration Gy, the slip angle θ estimated by the slip angle estimation unit 104, and the road surface friction coefficient μ estimated by the road surface friction coefficient estimation unit 105, The calculated turning angle command value δt is output to one input side of the adders 108L and 108R.

  This stabilization controller 107 is a controller that calculates the turning angle command value δt so that the actual behavior is equal to the normative behavior value of the normative model 106, and the look-ahead values of the yaw rate differential value γ ′ and the lateral acceleration Gy are By inputting from the vehicle behavior estimation unit 103, the change information of the behavior can be known before the behavior of the vehicle changes, so that the stability can be greatly improved as compared with the conventional controller.

Further, slip angles θ _F and θ _R of the steered wheels 3FL and 3FR are input from the active toe angle controller 109 as toe angle command values to the other input side of the adders 108L and 108R. Outputs are individually supplied to the motor drive circuits 110L and 110R, and the electric motors 54L and 54R of the pitman actuators 43L and 43R are driven and controlled by the motor drive circuits 110L and 110R.

The active toe angle controller 109 executes a toe angle control process shown in FIG.
This active toe angle control is executed as a timer interruption process every predetermined time (for example, 10 msec). First, in step S1, a lateral force acting on the steered wheels 3FL and 3FR from the vehicle integrated control unit 100 via the in-vehicle LAN. Fy _FL and Fy _FR and wheel speeds Vw _FL and Vw _FR are read, and then the process proceeds to step S2, and work is performed based on the read lateral forces Fy _FL and Fy _FR and wheel speeds Vw _FL and Vw _FR . The slip angles θ _L and θ _R of the left and right steered wheels 3FL, 3FR that minimize the rolling resistance of the steered wheels 3FL, 3FR are calculated by performing an operation that minimizes the objective function expressed below.

Fy _FL・ θ _L・ Vw _FL + Fy _R・ θ _R・ Vw _FR
Then, the processing proceeds to step S3, the calculated slip angle theta _L and theta _R from the output of the adder 108L and 108R end the timer interrupt processing returns to the predetermined main program.
Next, the operation of the above embodiment will be described.

Assuming that the steering wheel 21 is neutral and the vehicle is traveling straight on a good road, the lateral forces Fy _FL , Fy _FR , Fy _RL and Fy acting on each wheel of the vehicle in this straight traveling state are assumed. _RR is substantially zero, and the lateral acceleration Gy and the yaw rate differential value γ ′ calculated by the vehicle behavior estimating unit 103 according to the equations (3) and (4) are both substantially zero.
Therefore, the yaw rate γ calculated by the slip angle estimation unit 104 according to the equation (5) is also substantially zero, and the vehicle body slip angle θ calculated by the equation (6) is also substantially zero.

Further, the road surface friction coefficient μ calculated by the road surface friction coefficient estimating unit 105 according to the equation (7) becomes substantially zero, but the road surface friction coefficient μ calculated at the previous turn is maintained.
Further, since the lateral forces Fy _FL and Fy _FR acting on the steered wheels 3FL and 3FR are substantially zero, the torque command output from the reaction force control unit 102 is also a small value that does not cause the steering wheel 21 to swing. When this is supplied to the reaction force actuator 23, the reaction force actuator 23 generates a steering reaction force that prevents the steering wheel 21 from swinging, and the steering wheel 21 is prevented from swinging. .

  At this time, since the steering wheel 21 is in the neutral position, the steering angle δ output from the steering angle sensor 25 is also substantially zero, the target value of the yaw rate differential value, the lateral acceleration target value, etc. calculated by the reference model 106 Is also set to substantially zero, and the steering controller 107 calculates the turning angle at which the yaw rate differential value γ ′ and the lateral acceleration Gy input from the vehicle behavior estimation unit 103 coincide with the reference behavior value. The turning angle is also substantially zero.

Further, the slip angles θ _F and θ _R that minimize the rolling resistance calculated by the active toe angle controller 109 are also substantially zero, and the output values of the adders 108L and 108R are also substantially zero, so that the pitman actuators 43L and 43R The electric motors 54L and 54R control the pitman arms 42L and 42R so that the steered angles of the steered wheels 3FL and 3FR become substantially zero, so that the steered wheels 3FL and 3FR are controlled to the steered angle in the straight traveling state. .

  When the steering wheel 21 is steered to the left (or right) to shift to the turning traveling state from the straight traveling state, the steering angle δ is input to the reference model 106 according to the steering of the steering wheel 21. Based on the steering angle δ and the road surface friction coefficient μ input from the road surface friction coefficient estimating unit 105, the reference model 106 calculates a standard behavior value including a target yaw rate differential value γt ′ and a target lateral acceleration Gyt according to the road surface condition. These are input to the stabilization controller 107.

At this time, since the lateral forces Fy _{FL to} Fy _{RR of} the respective wheels 3FL to 3RR calculated by the signal processing circuit 91d are input to the vehicle behavior estimating unit 103, the look-ahead value is based on these lateral forces Fy _{FL to} Fy _RR. The yaw rate differential value γ ′ and the lateral acceleration Gy are calculated, and the yaw rate differential value γ ′ and the lateral acceleration Gy are input to the stabilization controller 107.
Therefore, the yaw rate differential value γ ′ and the lateral acceleration Gy, which are the look-ahead values estimated by the vehicle behavior estimation unit 103 in the stabilization controller 107, are the target yaw rate differential value γt ′ and the target lateral acceleration Gyt calculated by the reference model 106, respectively. The turning angle is calculated so as to match, the slip angle θ is added to the turning angle, and the turning angle command value δt is calculated by adding the road surface friction coefficient μ estimated by the road surface friction coefficient estimating unit 105. The turning angle command value δt is output to the adders 108L and 108R.

On the other hand, in the active toe angle controller 109, in order to optimally distribute the slip angle between the left and right steered wheels 3FL and 3FR so as to obtain a cornering load while minimizing the rolling resistance, the lateral force Fy of the steered wheels 3FL and 3FR is obtained. Objective functions Fy _FL · θ _L · Vw _FL + Fy _R · θ _R · Vw _FR having work dimensions represented by _FL and Fy _FR , wheel speeds Vw _FL and Vw _FR , and slip angles θ _L and θ _R Slip angles θ _L and θ _R are calculated, and the calculated slip angles θ _L and θ _R are output to the adders 108L and 108R. In this way, by calculating the slip angles θ _L and θ _R based on the lateral forces Fy _FL and Fy _FR of the steered wheels 3FL and 3FR and the wheel speeds Vw _FL and Vw _FR , the steered wheels 3FL and 3FR are moved from the road surface. Slip angles θ _L and θ _R corresponding to the input reaction force are calculated.

For this reason, the slip angle θ _L and θ _R input from the active toe angle controller 109 are added to the turning angle command value δt input from the stabilization controller 107 by the adders 108L and 108R to add the motor drive circuit 110L and By outputting to 110R, the electric motors 54L and 54R of the pitman actuators 43L and 43R are independently controlled so that the required cornering load can be obtained while minimizing the rolling resistance, and the left and right pitman arms 42L and 42R are independent. And rotate.

  At this time, the left and right pitman arms 42L and 42R are connected by the connecting member 44, and the connecting rods 81L and 81R of the connecting member 44 are connected by the relay rod 82 with a predetermined sliding resistance, and extend and contract in the axial direction. Therefore, the left and right pitman arms 42L and 42R can be allowed to rotate independently, and the expansion and contraction of the relay rod 82 in the axial direction has a predetermined sliding resistance. For this reason, reaction forces acting on the left and right steered wheels 3FL and 3FR from the road surface are different, reaction forces in the direction of canceling each other are generated, or the reaction force of one steered wheel is considerably larger than the reaction force of the other steered wheel In this case, the energy loss generated in the left and right electric motors 54L and 54R is proportional to the current of the motor torque, and the energy loss is proportional to the square of the current. It becomes larger than the energy loss caused by.

However, since the left and right pitman arms 42L and 42R are connected by the relay rod 82 with a predetermined sliding resistance, the force for rotating the left and right pitman arms 42L and 42R can be averaged to some extent. Rudder energy loss can be reduced.
Here, the sliding resistance of the relay rod 82 is not required to cause the left and right pitman actuators 43L and 43R to violently move relative to each other. You can take advantage of independent control.

  On the other hand, when an abnormality occurs in one of the left and right pitman actuators 43L and 43R, for example, in the control system of the pitman actuator 43R, the control of the pitman actuator 43R in which the abnormality has occurred is stopped. Since the pitman arm 42R corresponding to 43R is connected to the pitman arm 42L driven by the normal pitman actuator 43L via the connecting member 44, the normal pitman actuator 43L corresponds to the abnormal pitman actuator 43R. The pitman arm 42R can be driven, and the relay rod 82 has some resistance to relative motion, so that the fail-side steered wheels 3FR are less likely to vibrate, and stable steering is possible. That. During this failure, a force greater than the sliding resistance is transmitted to the relay rod 82 and the outer cylinder portion 83 and the sliding shaft portion 84 move relative to each other, and the small diameter shaft portion 84b of the sliding shaft portion 84 and the connecting rod 81L in FIG. The distance La between the connecting end surface and the end surface of the outer cylindrical portion 83 or the small diameter portion 83b of the outer cylindrical portion 83 and the step portion of the large diameter portion 83a and the small diameter shaft portion 84b and the large diameter shaft portion of the sliding shaft portion 84. When the distance Lb between the stepped portion 84a becomes zero, the outer cylinder portion 83 and the sliding shaft portion 84 move together, and the left and right are reliably connected so that they can be normally steered. Is done.

  As described above, according to the above embodiment, the left and right pitman arms 42L and 42R are connected by the connecting member 44 having a predetermined degree of freedom for expansion and contraction in the axial direction. Therefore, the pitman arms 42L and 42R are connected to the pitman actuator 43L. And 43R can be controlled independently on the left and right. In addition, when a failure occurs in one of the control systems of the pitman actuators 43L and 43R, the pitman arm on the fail side can be driven via the connecting member 44 by the other normal pitman actuator.

Further, the lateral force of the steered wheels 3FL and 3FR is measured by the lateral force sensor 91 provided on the hubs 31L and 31R having the double row angular ball bearing configuration constituted by the inner cylindrical portion 31b, the outer cylindrical portion 31d and the ball 31f. the lateral force Fy _FL ~Fy _RR acting directly detected in, by active control independently left and right of the pitman actuators 43L and 43R on the basis of the detected lateral force Fy _FL ~Fy _RR, while minimizing rolling resistance A necessary cornering load can be obtained, and an effect of improving fuel efficiency can be obtained, and at the same time, exercise performance can be improved.

Moreover, since the lateral forces Fy _{FL to} Fy _RR acting on the wheels are directly detected and the tire slip angle θ and the road surface friction coefficient μ are estimated based on the detected lateral forces Fy _{FL to} Fy _RR , these slip angles θ In addition, it is possible to accurately estimate the road surface friction coefficient.
Furthermore, the normative behavior calculated by the normative model 106 is equal to the actual vehicle behavior consisting of the yaw rate differential value γ ′, which is the look-ahead value calculated from the lateral forces Fy _{FL to} Fy _{RR by the} vehicle behavior estimation unit 103, and the lateral acceleration Gy. By calculating the turning angle command value δt by the stabilization controller 107, it is possible to predict a change in behavior before the vehicle behavior changes, and to perform highly accurate turning angle control. . Here, the road surface friction coefficient μ is also fed back to the reference model 106, so that, for example, a low yaw rate is not obtained on a low friction coefficient road surface, and the slip angle θ of the vehicle body is kept small to prevent spin. The norm model 106 can also be changed according to the road surface condition, and a more stable norm behavior can be calculated.

In the above-described embodiment, the case where the connecting member 44 is configured by the connecting rods 81L and 81R and the relay rod 82 has been described. However, the present invention is not limited to this, and a fluid-type shock having a piston using an orifice. A connecting member that is slidable and whose sliding range is regulated, such as an absorber, can also be applied.
In the above embodiment, the case where the active toe angle controller 109 performs feedback control that minimizes a predetermined objective function has been described. However, the present invention is not limited to this, and the slip angle is simply left and right. You may make it control so that it may become equal.

  Furthermore, in the above-described embodiment, the case where the steering mechanism is the pitman arm type has been described. However, the present invention is not limited to this, and as shown in FIG. 9, the pitman arms 42L and 42R and the pitman actuators 43L and 43R are used. May be omitted, and instead of these, geared motors 120L and 120R equipped with reduction gears may be applied to control the turning angle.

  That is, the geared motors 120L and 120R are fixedly disposed on the vehicle body side member so that the deceleration output shafts 121L and 121R are symmetrical in the vehicle width direction and are concentric, and the screw shafts are respectively connected to the deceleration output shafts 121L and 121R. 122L and 122R are connected. Then, tie rods 41L and 41R are rotatably connected to nuts 123L and 123R that are screwed onto the screw shafts 122L and 122R. Further, the motor output shafts 124L and 124R connected to the rotors of the geared motors 120L and 120R are projected from the opposite side to the deceleration output shafts 121L and 121R, and predetermined frictional resistances are mutually attached to the tips of the motor output shafts 124L and 124R. The connecting disks 125L and 125R that are in contact with each other are attached, and the geared motors 120L and 120R can be controlled independently by the contact resistance of these connecting disks 125L and 125R, and one of the geared motors 120L (or 120R) becomes abnormal. Sometimes, the motor output of the geared motor 120L (or 120R) in which the rotational force of the motor output shaft 124R (or 124L) of the other normal geared motor 120R (or 120L) becomes abnormal via the coupling disks 125L and 125R On shaft 124L (or 124R) Even to reach, it is possible to obtain the same effect as the above embodiment. In this case, the contact resistance between the connecting disks 125L and 125R is a friction resistance between the connecting disks 125L and 125R, a high-viscosity grease is used between them, or a spring or rubber provided on one of the connecting disks 125L and 125R. For example, an annular fluid chamber is formed on one motor output shaft 124L (or 124R) instead of the connecting disks 125L and 125R, and an orifice is formed in the fluid chamber. It is possible to provide fluid resistance by an orifice through a partition plate connected to the other motor output shaft 124R (or 124L). In this case as well, the relative rotation of the connecting disks 125L and 125R is performed, for example, by engaging the engaging pin provided on the other side with the engaging hole provided on one side, or on the other outer peripheral surface with the protrusion provided on one outer peripheral surface. By engaging the engaging pins, the rotation range between the connecting disks 125L and 125R is regulated so that the difference between the slip angles of the left and right steered wheels 3FL and 3FR can be absorbed.

  Further, as shown in FIGS. 10A to 10C, the projecting portions 126L and 126R projecting in the radial direction from both the coupling discs 125L and 125R with the coupling discs 125L and 125R facing each other without being brought into contact with each other. And an engaging pin 127 that engages the circumferential side surface of the other protruding portion 126L is formed on one protruding portion 126R so that the motor output shafts 124L and 124R can rotate freely within one rotation in the circumferential direction. In this case, since there is no frictional resistance until the engagement pin 127 is engaged with the protrusion 126L, as a steering actuator by the left and right average effect by the connecting member Although the energy reduction effect of the geared motors 120L and 120R cannot be obtained, the steered wheels 3FL and The reaction force from the road surface of the FR, that is, the self-aligning torque can be measured, and the left and right geared motors 120L and 120R can be independently controlled based on the measured self-aligning torque, and the steered wheels 3FL and 3FR can be controlled independently. The steered actuator can be independently controlled without detecting lateral force.

It is a schematic block diagram which shows the steer-by-wire type vehicle steering apparatus of this invention. It is the side view which made the deceleration mechanism which shows a pitman actuator a cross section. It is an expanded sectional view which shows the hub of a steered wheel. It is a schematic block diagram which shows the lateral force sensor which detects the lateral force of a wheel. It is a characteristic diagram which shows the relationship between the revolution speed of a rolling element, and an axial load. It is a block diagram which shows a steer-by-wire control unit. It is explanatory drawing which shows a simple 4 wheel model. It is a flowchart which shows an example of the toe angle control processing procedure performed with an active toe angle controller. It is a top view which shows other embodiment of this invention. It is explanatory drawing of the connection member which shows the modification of FIG. 9, Comprising: (a) is a longitudinal cross-sectional view explaining a connection disk, (b) is a front view of one connection disk, (c) is the other connection. It is a front view of a disk.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 2 ... Steering mechanism, 3FL, 3FR ... Steering wheel (front wheel), 3RL, 3RR ... Rear wheel, 4 ... Steering mechanism, 21 ... Steering wheel, 22 ... Steering shaft, 23 ... Electric motor, 24 ... Steering reaction force generating part, 31L, 31R ... Hub, 32L, 32R ... Knuckle arm, 41L, 41R ... Tie rod, 42L, 42R ... Pitman arm, 43L, 43R ... Pitman actuator, 44 ... Connecting member, 51 ... Car body side Member 52 ... Housing 53 ... Planetary gear type reduction mechanism 54L, 54R ... Electric motor 81L, 81R ... Connecting rod 82 ... Relay rod 83 ... Outer cylinder part 84 ... Sliding shaft part 91 ... Lateral force Sensor, 92 ... Wheel speed sensor, 100 ... Vehicle integrated control unit, 101 ... Steer-by-wire control unit, 10 DESCRIPTION OF SYMBOLS ... Reaction force control part, 103 ... Vehicle behavior estimation part, 104 ... Slip angle estimation part, 105 ... Road surface friction coefficient estimation part, 106 ... Reference model, 107 ... Stabilization controller, 108L, 108R ... Adder, 109 ... Active Toe angle controller, 110L, 110R ... motor drive circuit, 120L, 120R ... geared motor, 121L, 121R ... deceleration output shaft, 122L, 122R ... screw shaft, 123L, 123R ... nut, 124L, 124R ... motor output shaft, 125L, 125R: Connection disk, 126L, 126R ... Projection, 127 ... Engagement pin

Claims (4)

A steering mechanism that is steered by the driver, and a steering mechanism that steers the steered wheels by being separated from the steering mechanism, and the steered mechanism individually imparts a steering force to the left and right steered wheels. Having at least a pair of steered portions having a steered actuator to be applied, and a connecting member that is movable while restricting a movable range while providing a movable resistance for connecting the pair of steered portions ;
The connecting member is a vehicle steering apparatus characterized that you have configured the movable resistor to generate at least one of viscosity and friction. A steering mechanism that is steered by the driver, and a steering mechanism that steers the steered wheels by being separated from the steering mechanism, and the steered mechanism individually imparts a steering force to the left and right steered wheels. A pair of steered portions having a steered actuator to be applied, and a connecting member that is movable while restricting a movable range while providing a movable resistance for coupling the pair of steered portions; A steering control means for independently controlling the steering actuator of the steering unit based on the lateral force acting on the steered wheels ,
The connecting member is a vehicle steering apparatus characterized that you have configured the movable resistor to generate at least one of viscosity and friction. The steering control means includes a lateral force detection means for detecting a lateral force acting on the steered wheels, a wheel speed detection means for detecting a wheel speed of the steered wheels, and a lateral force detected by the lateral force detection means. The vehicle steering apparatus according to claim 2, further comprising: a steering control unit that independently feedback-controls a slip angle of the steered wheel based on a wheel speed detected by the wheel speed detecting unit. . The vehicle steering apparatus according to claim 3, wherein the lateral force detecting means and the wheel speed detecting means are built in a hub of the wheel.

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