Braking and driving force control device

Abstract

To provide a braking and driving force control device that reduces an unintended yaw motion at the time of in-phase steering.SOLUTION: In a vehicle in which all of tires 91 to 94 can be steered and each of the tires 91 to 94 can be braked and driven independently, a braking and driving force control device 201 controls braking and driving forces F1 to F4 output by braking and driving actuators 81 to 84. A steering state determination unit 26 determines whether the respective tires 91 to 94 are mutually in an in-phase state. A braking and driving force instruction unit 28 calculates braking and driving force instruction values F*1 to F*4 for instruction to the braking and driving actuators 81 to 84. When it is determined by the steering state determination unit 26 that the respective tires 91 to 94 are mutually in the in-phase state, and when it is determined that a yaw motion of the vehicle occurs based on information acquired from a yaw motion detection device 30 or it is predicted that a yaw motion of the vehicle will occur, the braking and driving force instruction unit 28 corrects the braking and driving force instruction values F*1 to F*4 to be instructed to at least one of the braking and driving actuators.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a braking / driving force control device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there are known techniques for suppressing the yaw motion of a vehicle other than when the vehicle is turning.

[0003] For example, a vehicle control device disclosed in Patent Document 1 is for a four-wheel steering vehicle in which the steering angle of the rear wheels is controlled according to the steering angle of the front wheels. When the front and rear wheels are steered in the same phase, the rear wheels are controlled to take a rear-wheel target steering angle determined according to the steering angle of the front wheels. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-285036 A Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 modifies the steering angle of the wheels to suppress the yaw rate, which increases the running resistance. Patent Document 1 also makes no mention of control of the braking and driving forces of each wheel of a vehicle. Note that in this specification, the term "vehicle" includes, from a technical point of view, any moving body capable of running on the ground by wheels, regardless of legal classification regarding running on public roads. For example, green slow mobility and AGVs (automated guided vehicles) are also included in the term "vehicle."

[0006] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a braking / driving force control device that suppresses unintended yaw motion during in-phase steering. [Means for solving the problem]

[0007] In a vehicle (100, 105) to which the braking / driving force control device of the present invention is applied, all of the tires (91-94) of three or more wheels can be steered, and each tire can be independently braked / driven by the braking / driving forces (F1-F4) output by the braking / driving actuators (81-84) corresponding to the tires. The vehicle is also equipped with a yaw motion detection device (30) that detects yaw motion. The braking / driving force control device controls the braking / driving forces output by the braking / driving actuators.

[0008] The braking / driving force control device includes a target tire angle calculation control section (25), a steering state determination section (26), and a braking / driving force instruction section (28). The target tire angle calculation control section calculates a target tire angle (δ * 1-δ * 4. δ * 12, δ * 34) and issues a command to the steering actuators (71-76).

[0009] The steering state determination unit determines whether the tires are in phase with each other based on the target tire angles of each tire instructed by the target tire angle calculation control unit, or the detected tire angles (θs1-θs4, δs12, δs34) of each tire acquired from the tire angle sensors (671-676). The braking / driving force instruction unit calculates a braking / driving force instruction value (F * 1-F * 4) is calculated and sent to the braking / driving actuator.

[0010] When the steering state determination unit determines that the tires are in phase with each other and determines that yaw motion of the vehicle is occurring based on information obtained from the yaw motion detection device, or predicts that yaw motion of the vehicle will occur, the braking / driving force instruction unit corrects the braking / driving force instruction value to be instructed to at least one braking / driving actuator.

[0011] The braking / driving force control device of the present invention can suppress unintended yaw motion during in-phase steering by adjusting the balance of the braking / driving forces of each tire in a vehicle capable of braking and driving each tire independently. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a four-wheel independently steering vehicle equipped with a braking / driving force control device according to an embodiment of the present invention; [Diagram 2] 1 is a block diagram of a four-wheel steering vehicle equipped with a braking / driving force control device according to an embodiment of the present invention; [Diagram 3] A diagram showing diagonal movement due to in-phase steering on a four-wheel independently steering vehicle and a four-wheel steering vehicle (absolute value of tire angle less than 90 degrees). [Figure 4] A diagram showing the lateral movement and tight turning of a four-wheel independently steering vehicle. [Diagram 5] 1 is a block diagram of a braking / driving force control device according to a first embodiment. [Figure 6] FIG. 2 is a diagram for explaining the four-wheel geometric center of a four-wheel vehicle. [Figure 7] 11 is a diagram for explaining the balance of yaw moment when the center of gravity coincides with the geometric center of the four wheels during oblique movement. FIG. [Figure 8] 13 is a diagram showing the generation of yaw motion when the center of gravity is shifted from the geometric center of the four wheels during oblique movement, and the distribution of braking and driving forces for suppressing the yaw motion. [Figure 9] 4 is a flowchart showing a braking force control process according to the first embodiment. [Figure 10] FIG. 5 is a block diagram of a braking / driving force control device according to a second embodiment. [Figure 11] 10 is a flowchart showing a braking force control process according to a second embodiment. [Figure 12] FIG. 11 is a block diagram of a braking / driving force control device according to a third embodiment. [Figure 13] FIG. 13 is a diagram showing the distribution of braking / driving force when all tires are not in a slipping state during oblique movement. [Figure 14] 13A and 13B are diagrams showing the occurrence of yaw motion when slip suppression processing is executed during oblique movement, and the distribution of braking / driving forces for suppressing the yaw motion. [Figure 15] 10 is a flowchart showing a braking force control process according to a third embodiment. [Figure 16] FIG. 13 is a block diagram of a braking / driving force control device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Several embodiments of the braking / driving force control device will be described with reference to the drawings. In the several embodiments, substantially the same configurations are given the same reference numerals and the description will be omitted. The following first to fourth embodiments will be collectively referred to as "the present embodiment". The braking / driving force control device of the present embodiment is mounted on a vehicle in which all tires of three or more wheels can be steered, typically a four-wheel independently steered vehicle, or a four-wheel steered vehicle in which the front left and right wheels and the rear left and right wheels are respectively connected. Furthermore, all tires of three or more wheels can be independently braked and driven by braking / driving forces output by braking / driving actuators corresponding to each tire. The braking / driving force control device controls the braking / driving forces output by the braking / driving actuators.

[0014] The configurations of a four-wheel independently steering vehicle 100 and a four-wheel steering vehicle 105 equipped with the braking / driving force control device 20 of this embodiment will be described with reference to Figures 1 and 2. The four-wheel independently steering vehicle 100 shown in Figure 1 and the four-wheel steering vehicle 105 shown in Figure 2 each have four tires 91-94. The left front wheel 91 is labeled "FL", the right front wheel 92 is labeled "FR", the left rear wheel 93 is labeled "RL", and the right rear wheel 94 is labeled "RR". The symbols of the following elements and the suffixes "1" to "4" of each symbol correspond to the FL, FR, RL and RR tires 91-94, respectively.

[0015] The vehicles 100 and 105 are provided with braking / driving actuators 81-84 corresponding to the respective tires 91-94. In the drawing, "actuator" is written as "Act." For example, the braking / driving actuators 81-84 are configured as a set of an electric brake as a braking actuator and an in-wheel motor as a driving actuator. Each tire 91-94 can be independently braked / driven by the braking / driving forces F1-F4 outputted by the braking / driving actuators 81-84. When driven by the driving actuator, the driving force of each tire 91-94 is transmitted to the road surface, generating positive acceleration, and the vehicles 100 and 105 accelerate. When braking by the braking actuator, the braking force of each tire 91-94 is transmitted to the road surface, generating negative acceleration, and the vehicles 100 and 105 decelerate.

[0016] A movement direction instruction value is input to the braking / driving force control device 20 from the movement direction instruction device 15. The movement direction instruction value includes operation signals of the steering wheel, accelerator, brake, etc. by the driver and signals of the automatic driving control device, and includes information on not only the movement direction but also the movement speed. The braking / driving force control device 20 calculates the braking / driving force instruction value F, which is an instruction value for the braking / driving force output by the braking / driving actuators 81-84 based on the movement direction instruction value. * 1-F * 4 and issues a command to the braking / driving actuators 81-84.

[0017] In common with the first to fourth embodiments, the vehicles 100, 105 are provided with a yaw motion detection device 30. The yaw motion detection device 30 detects the yaw motion of the vehicles 100, 105, such as the yaw rate, yaw angular acceleration, and yaw angle. In embodiments other than the second embodiment, the vehicles 100, 105 are provided with a center-of-gravity position detection device 40. The center-of-gravity position detection device 40 calculates the center-of-gravity position of the vehicles 100, 105 from the difference in moment in the vehicle front-rear direction (pitch direction) based on, for example, wheel load information of each tire 91-94. In the third embodiment, the vehicles 100, 105 are further provided with a slip ratio detection device 50, indicated by a dashed line frame. The slip ratio detection device 50 detects the slip ratio of each tire 91-94 using, for example, wheel speed information from a wheel speed sensor.

[0018] The driving and braking force control device 20 determines the driving and braking force command value F according to the situation based on the information acquired from the detection devices 30, 40, and 50 of the vehicles 100 and 105. * 1-F * 4 is corrected based on the information that the braking / driving force control device 20 acquires from each of the detection devices 30, 40, 50 and the braking / driving force command value F * 1-F * The correction of 4 will be described in detail later.

[0019] In the four-wheel independently steerable vehicle 100 shown in Fig. 1, all of the tires 91-94 can be steered independently. The vehicle 100 is provided with steering actuators 71-74 and tire angle sensors 671-674 that detect the actual tire angles (hereinafter "actual tire angles") corresponding to the tires 91-94. The tire angle is expressed as 0 at a neutral position parallel to the vehicle's longitudinal axis, with a counterclockwise direction being positive and a clockwise direction from the neutral position being negative.

[0020] For example, steering actuators 71-74 are configured integrally with a motor section such as a three-phase brushless motor including a stator and a rotor around which windings are wound, and a motor drive device that controls the drive current passed through the windings. Each of tires 91-94 can be steered independently by steering torques Tst1-Tst4 output by steering actuators 71-74.

[0021] Tire angle sensors 671-674 may be configured with encoders or the like that directly detect actual tire angles. Alternatively, if there is a correlation between the drive current of steering actuators 71-74 and the tire angles, the drive current of steering actuators 71-74 detected by a current sensor may be converted into detected tire angles δs1-δs4 based on the current-torque characteristics or the torque transfer coefficient. In that case, the current sensors are considered to function as tire angle sensors 671-674.

[0022] The braking / driving force control device 20 adjusts the target tire angle δ of each tire 91-94 based on the movement direction indication value input from the movement direction indication device 15. * 1-δ *4 and issues a command to steering actuators 71-74. Braking / driving force control device 20 also acquires detected tire angles δs1-δs4 of each of tires 91-94 detected by tire angle sensors 671-674.

[0023] In a four-wheel steering vehicle 105 shown in Fig. 2, front left and right wheels 91, 92 and rear left and right wheels 93, 94 are mechanically coupled by rack shafts 95, 96, respectively. Each tire 91-94 is coupled to both ends of the rack shafts 95, 96 via a link mechanism such as a tie rod. This corresponds to a vehicle known as a "4WS." For each rack shaft 95, 96, steering actuators 75, 76 and tire angle sensors 675, 676 that convert the stroke of the rack shafts 95, 96 to detect the tire angle are provided.

[0024] The front row has a target tire angle of δ * In response to signal output δs12, the steering torque output by steering actuator 75 is transmitted to rack shaft 95, which is driven left and right, thereby steering front row left and right wheels 91, 92 in conjunction with each other. Tire angle sensor 675 detects detected tire angle δs12 of front row left and right wheels 91, 92, and notifies braking / driving force control device 20.

[0025] In the rear row, the target tire angle is δ * The steering torque output by steering actuator 76 in response to steering angle δs34 is transmitted to rack shaft 96, which is driven left and right, causing rear row left and right wheels 93, 94 to turn in unison. Tire angle sensor 676 detects detected tire angle δs34 of rear row left and right wheels 93, 94, and notifies braking / driving force control device 20.

[0026] In addition to the vehicles 100, 105 shown in Figures 1 and 2, the braking / driving force control device 20 may be installed in a partially independently steering vehicle in which, for example, the left front wheel 91 and the right front wheel 92 can be steered independently and the rear row left and right wheels 93, 94 are mechanically connected, or conversely, in which the left rear wheel 93 and the right rear wheel 94 can be steered independently and the front row left and right wheels 91, 92 are mechanically connected.

[0027] A driving characteristic of four-wheel independently steering vehicle 100 and four-wheel steering vehicle 105 will be described with reference to Figs. 3 and 4. In the vehicle diagrams below, the symbol Cg indicates the center of gravity. Conventionally, in a typical vehicle, a pair of left and right tires are mechanically connected via a link, and only the front left and right wheels are steered by steering the steering wheel. In the future, developments are expected to include steer-by-wire in which the steering wheel and the link between the left and right wheels are mechanically separated, four-wheel steering vehicle 105 in which the rear left and right wheels can be steered in addition to the front left and right wheels, and further four-wheel independently steering vehicle 100 in which all wheels can be steered independently.

[0028] As shown in FIG. 3, in the four-wheel independently steering vehicle 100 and the four-wheel steering vehicle 105, diagonal movement is possible by steering all the wheels in the same phase. The angle of the traveling direction with respect to the front and rear axes of the vehicle during diagonal movement is denoted as diagonal movement angle θ. For example, when changing lanes while traveling straight, by steering all four wheels in the same phase and moving diagonally, it is possible to change lanes with zero yaw rate while suppressing travel loss due to tire drag. The steering of all four wheels in the same phase is realized by performing feedback control so that the actual tire angles δ1-δ4 of each tire 91-94 are equal based on the currently detected tire angles δs1-δs4 of each tire 91-94.

[0029] Except for those equipped with a special link mechanism, in a normal four-wheel steering vehicle 105, the absolute value of the maximum tire angle is less than 90 degrees, and the absolute value of the diagonal movement angle θ is also less than 90 degrees. In contrast, as shown in the top of Figure 4, in the four-wheel independently steering vehicle 100, a maximum tire angle of 90 degrees or more in absolute value can be achieved, so lateral movement by in-phase steering of ±90 degrees is possible. Also, as shown in the bottom of Figure 4, in the four-wheel independently steering vehicle 100, tight turns are possible by greatly changing the tire angles of the inside wheel and the outside wheel about the turning center Ct.

[0030] Below, the first to fourth embodiments will be described in order, focusing mainly on the oblique movement achieved by in-phase steering where the absolute value of the tire angle is less than 90 degrees. The reference numerals for the braking / driving force control device in each embodiment are designated by the third digit following "20", which indicates the embodiment. In the following description, the reference numerals "100, 105" will not be used as vehicle reference numerals, and only the reference numeral "100" will be used for the four-wheel independently steering vehicle as a representative reference. In addition, in the description of the steering actuators, the reference numerals for steering actuators 71-74, etc. in four-wheel independently steering vehicle 100 and the reference numeral for target tire angle δ will be used as the reference numerals for the four-wheel independently steering vehicle 100. * 1-δ * 4. This description is "the steering actuators 75, 76 in a four-wheel steering vehicle 105, the target tire angle δ * 12, δ * 34, etc." may be read as such.

[0031] (First embodiment) The first embodiment will be described with reference to Figures 5 and 6. As shown in Figure 5, a braking / driving force control device 201 of the first embodiment has a target tire angle calculation control unit 25, a turning state determination unit 26, and a braking / driving force instruction unit .

[0032] The target tire angle calculation control unit 25 calculates the target tire angle δ of each tire 91-94 based on the movement direction indication value input from the movement direction indication device 15. * 1-δ * For example, when a lane change is instructed at a diagonal movement angle θ while the vehicle is traveling straight ahead, the target tire angle calculation control unit 25 calculates the diagonal movement angle θ and issues a command to the steering actuators 71-74. * 1-δ * Indicate as 4.

[0033] The steering state determination unit 26 determines whether the tires 91-94 are in phase with each other, based on the detected tire angles δs1-δs4 of each tire obtained from the tire angle sensors 671-674, and notifies the driving / braking force instruction unit 28. For example, when the range from the minimum value to the maximum value of the detected tire angles δs1-δs4 is equal to or less than the determination threshold, the tires 91-94 are determined to be in phase with each other. Making the determination based on the detected tire angles δs1-δs4 makes it possible to perform control that reflects the actual vehicle behavior.

[0034] The braking / driving force instruction unit 28 outputs a braking / driving force instruction value F, which is an instruction value for the braking / driving force output by the braking / driving actuators 81-84, based on the movement direction instruction value. * 1-F * 4 and issues a command to the braking / driving actuators 81-84.

[0035] Braking / driving force instruction unit 28 receives a notification of the same phase determination from steering state determination unit 26. Braking / driving force instruction unit 28 also acquires yaw motion parameters such as yaw rate, yaw angular acceleration, and yaw angle from yaw motion detection device 30. Based on the information acquired from yaw motion detection device 30, braking / driving force instruction unit 28 determines whether or not yaw motion of vehicle 100 is occurring.

[0036] When the steering state determination unit 26 determines that the tires 91-94 are in the same phase with each other and determines that yaw motion of the vehicle 100 is occurring based on the information obtained from the yaw motion detection device 30, the braking / driving force instruction unit 28 outputs a braking / driving force instruction value F to be instructed to at least one braking / driving actuator. * 1-F * Correct 4.

[0037] 6 to 8, the mechanism by which yaw motion occurs during diagonal movement and the braking / driving force command value F * 1-F *The significance of correcting 4 will be explained. First, refer to FIG. 6. The front-rear axis of the vehicle is the X-axis (front is positive), the left-right axis is the Y-axis (right is positive), the wheelbase is Lx, and the tread width is Ly. The wheelbase Lx corresponds to the distance between the front wheel axis yf connecting the centers of the front left and right wheels 91, 92 and the rear wheel axis yr connecting the centers of the rear left and right wheels 93, 94.

[0038] The point that is the center of the wheelbase Lx in the vehicle longitudinal direction and the center of the tread width Ly in the vehicle lateral direction is defined as the four-wheel geometric center Cm. The distance from the four-wheel geometric center Cm to the center of each tire in the vehicle longitudinal direction is expressed as (Lx / 2), and the distance in the vehicle lateral direction is expressed as (Ly / 2). The diagonal movement angle θ is defined as positive, for example, in the counterclockwise direction with the X-axis set to 0.

[0039] Figure 7 shows a state in which the center of gravity Cg coincides with the four-wheel geometric center Cm during diagonal movement. A straight line that passes through the center of gravity Cg and extends in the direction of the diagonal movement angle θ is represented as the traveling direction center of gravity line p. The length of a perpendicular line drawn from the center of each tire 91-94 to the traveling direction center of gravity line p is defined as the acting distance L1-L4. For example, in diagonal movement to the right (θ<0), if the intersection point between the front wheel axis yf and the traveling direction center of gravity line p is P, the center of the left front wheel 91 is Q, and the length of the line PQ is Lo1, then the acting distance L1 is calculated by formula (1.1).

[0040] L1=Lo1·cosθ ={(Ly / 2)-(Lx / 2)tanθ}cosθ ···(1.1)

[0041] Similarly, the action distance L2 is calculated using formula (1.2).

[0042] L2={(Ly / 2)+(Lx / 2)tanθ}cosθ ···(1.2)

[0043] The acting distance L1 is equal to the acting distance L4, and the acting distance L2 is equal to the acting distance L3 (L1=L4, L2=L3). The same magnitude of braking / driving force F is distributed to each wheel 91-94, and the yaw moments on the left and right sides of the traveling center of gravity line p are balanced, as shown in equation (1.3).

[0044] (L1+L3)F=(L2+L4)F (1.3)

[0045] In this way, if the center of gravity Cg of the vehicle 100 coincides with the four-wheel geometric center Cm, the braking / driving force F is distributed equally to each tire 91-94 during diagonal movement, and when acceleration or deceleration occurs in the vehicle 100, the yaw moment is balanced and no yaw motion occurs in the vehicle 100. Therefore, diagonal movement with a yaw rate of zero is possible.

[0046] However, when the loading situation of occupants, luggage, etc. changes, the center of gravity Cg of the vehicle 100 may shift from the four-wheel geometric center Cm, as shown in FIG. 7. In the example shown at the top of FIG. 8, the position of the center of gravity Cg is shifted forward from the four-wheel geometric center Cm. Hereinafter, "center of gravity position shift" refers to the shift of the center of gravity Cg from the four-wheel geometric center Cm. The amount of shift of the center of gravity position is represented as "ΔGx", and the acting distance in a state where there is a center of gravity position shift is represented as Lg1-Lg4. Since the traveling direction center of gravity line p shifts forward, the acting distance Lg1 is not equal to the acting distance Lg4, and the acting distance Lg2 is not equal to the acting distance Lg3. In this example, "Lg1" is<Lg4、Lg2> Lg3".

[0047] As a result, in a situation where the same magnitude of braking / driving force F is distributed to each wheel 91-94, the balance of the yaw moment is lost during acceleration / deceleration as shown in equation (1.4), and a yaw rate γ is generated. In this example, the yaw moment due to the braking / driving force F of the right front wheel 92 and the right rear wheel 94 exceeds the yaw moment due to the braking / driving force F of the left front wheel 91 and the left rear wheel 93, so a yaw rate γ is generated that turns the vehicle 100 left, and the vehicle behavior becomes unstable.

[0048] (Lg1+Lg3)F<(Lg2+Lg4)F ···(1.4)

[0049] Therefore, the braking / driving force command unit 28 of the braking / driving force control device 201 calculates the initially calculated braking / driving force command value F based on the deviation amount ΔGx of the center of gravity position obtained from the center of gravity position detection device 40. * 1-F *When the driving / braking force command value F4 is received, it is predicted that the vehicle 100 will yaw. The driving / braking force command value F4 is then sent to the driving / braking force actuators 81-84 to suppress the yaw rate caused by the displacement of the center of gravity. * 1-F * For this correction, braking / driving force instructor 28 uses the amount of deviation ΔGx of the center of gravity position, and estimates the oblique movement angle θ from the detected tire angles δs1-δs4 acquired by steering state determiner 26.

[0050] The center of gravity position detection device 40 obtains the wheel loads Fz1-Fz4 of the tires 91-94 by, for example, a load sensor, and calculates the deviation amount ΔGx of the center of gravity position using formula (2). The part "Fz1+Fz2-Fz3-Fz4" in the numerator of formula (2) means the difference in wheel loads between the front wheels 91, 92 and the rear wheels 93, 94, that is, the difference in the moment in the pitch direction. When the moment in the pitch direction is balanced, "ΔGx=0" is satisfied, and there is no deviation in the center of gravity position. Also, when "Fz1, Fz2>>Fz3, Fz4", "ΔGx≒(Lx / 2)" is satisfied, and the center of gravity Cg is asymptotically approaching the front wheel axle yf. "x" and "z" in the formula are written as subscripts.

[0051]

number

[0052] Braking / driving force indicator 28 calculates acting distances Lg1-Lg4 for each of tires 91-94 using the center of gravity position deviation amount ΔGx and the oblique movement angle θ according to equations (3.1) to (3.4), where "x" and "y" are subscripts.

[0053]

number

[0054] Next, braking / driving force instruction unit 28 calculates braking / driving forces Fg1-Fg4 for each of tires 91-94 so that equation (4) holds. As shown in the bottom of Figure 8, when equation (4) holds, yaw moment is balanced during acceleration / deceleration, and the occurrence of yaw rate is suppressed.

[0055] Lg1·Fg1+Lg3·Fg3=Lg2·Fg2+Lg4·Fg4 (4)

[0056] For example, by substituting the longitudinal forces Fg1-Fg4 determined by equations (5.1) and (5.2) into both sides of equation (4), the following equation is established: where L is calculated by equation (5.3).

[0057]

number

[0058] L = Lg1 + Lg2 + Lg3 + Lg4 (5.3)

[0059] The driving and braking forces Fg1-Fg4 calculated in this way are the corrected driving and braking force command value F * 1-F * Braking / driving force command unit 28 commands each of braking / driving force actuators 81-84 as "F4". * 1=Fg1, F * 2=Fg2, F * 3=Fg3, F * The driving / braking force command value Fg4 is set to Fg4. * 1-F * 4. Therefore, the yaw rate caused by the deviation of the center of gravity position is suppressed before the yaw movement actually occurs.

[0060] The braking / driving force control process according to the first embodiment is shown in the flowchart of FIG. 9. In the following explanation of the flowchart, the symbol "S" denotes a step. Common step numbers are used for steps that are common to the second embodiment shown in FIG. 11. Steps that correspond to but differ partially between the first and second embodiments are distinguished by adding the symbol "A / B" to the end of the step number. This process is performed repeatedly while the vehicle 100 is traveling, from when it starts traveling until it stops.

[0061] In S1A, the braking / driving force indicator 28 calculates the braking / driving force indicator values ​​F * 1-F * In S2, the steering state determination unit 26 acquires the detected tire angles δs1-δs4 of the tires 91-94 from the tire angle sensors 671-674. In S3, it is determined whether the tires 91-94 are in phase with each other based on the detected tire angles δs1-δs4. If the result in S3 is NO during cornering, the process proceeds to before S10A. If the result in S3 is YES, the process proceeds to S4.

[0062] In S4, braking / driving force instruction unit 28 acquires the center of gravity position of vehicle 100 from center of gravity position detection device 40. In S5, it is determined whether the absolute value of center of gravity position deviation amount ΔGx is equal to or greater than a determination threshold value. If NO in S5, the process proceeds to before S10A. If YES in S5, braking / driving force instruction unit 28 acquires pre-correction braking / driving force instruction value F * 1-F * If 4 is specified as is, it is predicted that yaw motion of the vehicle 100 will occur, and the process proceeds to S9A.

[0063] In S9A, braking / driving force instruction unit 28 calculates braking / driving force instruction values ​​F for each tire 91-94 using the center-of-gravity position deviation amount ΔGx obtained from center-of-gravity position detection device 40 in equations (3.1) to (3.4). * 1-F * In S10A, braking / driving force instruction unit 28 corrects braking / driving force instruction value F * 1-F * 4 is instructed to the braking / driving actuators 81-84. When the flow moves from S9A, the corrected braking / driving force instruction value F * 1-F *If the transition is made with NO in S3 or S5, the braking / driving force command value F * 1-F * 4 is indicated.

[0064] When the braking / driving force instruction unit 28 of the first embodiment predicts the occurrence of yaw motion of the vehicle 100 based on the center-of-gravity position deviation amount ΔGx acquired from the center-of-gravity position detection device 40, the braking / driving force instruction value F * 1-F * 4 is corrected to cancel the yaw moment of the vehicle 100 caused by the displacement of the center of gravity. * 1-F * By correcting 4, unintended yaw movement can be suppressed during diagonal movement (in-phase steering).

[0065] Second embodiment The second embodiment will be described with reference to Figures 10 and 11. A vehicle 100 equipped with a braking / driving force control device 202 of the second embodiment does not need to have a center-of-gravity state detection device 40. Or, even if the vehicle 100 has a center-of-gravity position detection device 40, the braking / driving force control device 202 does not need to acquire center-of-gravity position information from the center-of-gravity position detection device 40, for example, in cases where there is little change in the loading status of occupants or luggage and the center-of-gravity position is almost constant.

[0066] In other words, as shown in Fig. 10, no center-of-gravity position information is input to the driving / braking force control device 202. Instead, the driving / braking force control device 202 stores an estimated value of the center-of-gravity position as a default value. * 1-F * When correcting 4, braking / driving force indicator 28 uses an estimated value of center of gravity position deviation amount ΔGx stored internally.

[0067] The braking / driving force control process according to the second embodiment will be described with reference to the flowchart of Figure 11, particularly the differences from Figure 9. In S1B, braking / driving force instruction unit 28 calculates braking / driving force instruction values ​​F * 1-F *4 and issues a command to the braking / driving actuators 81-84. That is, unlike S1A in FIG. 9, the command is issued after the calculation. S2 and S3 are the same as in FIG. 9. However, if NO in S3, the braking / driving force command value F * 1-F * Since 4 has already been instructed, the routine ends after S10B. If YES in S3, proceed to S7.

[0068] In S7, the braking / driving force instruction unit 28 acquires yaw motion parameters, such as the yaw rate, yaw angular acceleration, and yaw angle, from the yaw motion detection device 30. Here, the larger the absolute value of the yaw motion parameter, the more the vehicle 100 is yaw moving. In S8, it is determined whether the absolute value of the yaw motion parameter is equal to or greater than a judgment threshold value. If the answer is NO in S8, such as while the vehicle is traveling straight ahead, the routine ends. If the answer is YES in S8, it is determined that "yaw motion of the vehicle 100 is occurring," and the process proceeds to S9B.

[0069] In S9B, braking / driving force instruction unit 28 calculates braking / driving force instruction values ​​F * 1-F * In S10B, braking / driving force indicator 28 corrects the corrected braking / driving force indicator value F * 1-F * 4 is instructed to the braking / driving actuators 81-84.

[0070] The second embodiment differs from the first embodiment in that the yaw rate is suppressed after the yaw motion actually occurs, but like the first embodiment, unintended yaw motion can be suppressed during oblique movement (in-phase steering). In addition, the second embodiment can be installed on a vehicle 100 that does not have a center-of-gravity state detection device 40, so the range of application is wider than that of the first embodiment.

[0071] Third embodiment The third embodiment will be described with reference to Figs. 12 to 15. When the friction characteristics of each tire are approximately the same, the driving / braking force that becomes the tire's slip limit depends on the tire's wheel load. When the center of gravity Cg is deviated from the four-wheel geometric center Cm, the wheel loads of each wheel are different, and therefore the slip limit is also different. In addition, by correcting the driving / braking force of each tire according to the first embodiment, there is a possibility that a phenomenon will occur in which only a specific tire slips.

[0072] As shown in FIG 12, a braking / driving force control device 203 of the third embodiment is mounted on a vehicle equipped with a slip ratio detection device 50 that detects the slip ratio of each tire. The slip ratio is the difference between the vehicle body speed and the wheel speed divided by the vehicle body speed. The slip ratio is 0% when the tires are rolling on the road surface without any slipping, and 100% when the tires are completely locked. The slip ratio detection device 50 calculates the slip ratio of each tire using wheel speed information from wheel speed sensors of each wheel, for example.

[0073] Braking / driving force control device 203 of the third embodiment further includes a slip state determination unit 27 in addition to the configuration of braking / driving force control device 201 of the first embodiment. Slip state determination unit 27 determines whether or not each tire is in a slip state based on the slip ratio obtained from slip ratio detection device 50. In other words, slip state determination unit 27 determines that each tire is not in a slip state when the slip ratio is less than a threshold value, and determines that a tire is in a slip state when the slip ratio is equal to or greater than the threshold value. Slip state determination unit 27 notifies braking / driving force instruction unit 28 of the determination result.

[0074] One or more tires that are determined to be in a slipping state are defined as "slip tires", and one or more tires other than the slipping tires are defined as "non-slip tires". Since at least one non-slip tire is required, a four-wheeled vehicle has three or fewer slipping tires. Generally speaking, an N-wheeled vehicle has (N-1) or fewer slipping tires.

[0075] When slip state determination unit 27 determines that one or more tires are in a slip state, i.e., when it is determined that there is one or more slipping tires, braking / driving force instruction unit 28 executes a "slip suppression process" to maintain or reduce the braking / driving force of the slipping tire. Acceleration due to an increase in driving force is prohibited during driving, and deceleration due to an increase in braking force is prohibited during braking. The target values ​​at which braking / driving force instruction unit 28 maintains or reduces the braking / driving force may be stored in a map or the like using parameters such as the diagonal movement angle θ and the vehicle speed, for example.

[0076] Braking / driving force command unit 28 corrects the braking / driving force command values ​​of the non-slip tires so as to cancel out the yaw moment of vehicle 100 that occurs due to the slip suppression process.

[0077] Fig. 13 shows the braking force distribution when none of the tires 91-94 are in a slipping state during diagonal movement. As in the lower diagram of Fig. 8, the state in which the center of gravity Cg is offset from the geometric center Cm of the four wheels is illustrated. As in the above formula (4), the yaw moment on both sides of the traveling center of gravity line p is balanced, so no yaw moment is generated in the vehicle 100.

[0078] Lg1·Fg1+Lg3·Fg3=Lg2·Fg2+Lg4·Fg4 (4)

[0079] FIG. 14 shows the braking force distribution when the left rear wheel 93 is in a slipping state. The "s" in the braking force symbol Fgs comes from slip. As shown in the upper diagram, the braking / driving force of the slipping tire 93 is reduced from Fg3 (FIG. 13) to Fgs3 by slip suppression processing. At this time, if the braking / driving forces of the non-slip tires 91, 92, 94 are the same as the values ​​in FIG. 13, the yaw moment on both sides of the traveling direction center of gravity line p will not be balanced, as shown in equation (6.1). In addition, a yaw moment is generated in the vehicle 100 due to the deviation between the driving force command value of the slipping tire 93 and the actual braking / driving force.

[0080] Lg1 Fg1+Lg3 Fgs3 <Lg2·Fg2+Lg4·Fg4 (6.1)

[0081] Therefore, as shown in the lower diagram, in order to suppress the yaw moment, the braking / driving force command unit 28 sets the braking / driving force command value F of the non-slip tires 91, 92, 94 so that the formula (6.2) holds. * 1. F * 2. F * 4 is corrected to the values ​​of Fgs1, Fgs2, and Fgs4, respectively.

[0082] Lg1・Fgs1+Lg3・Fgs3=Lg2・Fgs2+Lg4・Fgs4 (6.2)

[0083] The braking force control process according to the third embodiment is shown in the flowchart of Fig. 15. In S21, the slip state determination unit 27 obtains the slip ratio from the slip ratio detection device 50 and determines whether each tire is in a slip state. In S22, it is determined whether one or more tires are in a slip state. If the result in S22 is NO, the routine ends.

[0084] If the answer is YES in S22, the slip suppression process is executed in S23. That is, braking / driving force instruction unit 28 maintains or reduces the braking / driving force of the slipping tire. In S24, braking / driving force instruction unit 28 increases or decreases the braking / driving force instruction value F of the non-slip tire so as to cancel the yaw moment of vehicle 100 caused by the slip suppression process. * 1-F * Correct 4.

[0085] In this way, in the third embodiment, slippage is suppressed by maintaining or reducing the braking / driving force of the slipping tire. Furthermore, the yaw moment of the vehicle 100 generated by the slip suppression process is calculated based on the braking / driving force command value F * 1-F * Therefore, even if a particular tire is in a slipping state, unintended yaw motion can be suppressed during diagonal movement (in-phase steering).

[0086] (Fourth embodiment) A braking / driving force control device 204 according to a fourth embodiment will be described with reference to FIG. 16. The third embodiment differs from the first embodiment only in the tire angle information that the steering state determination unit 26 uses to determine the in-phase state, and the rest of the configuration is the same. In the fourth embodiment, feedback control of the tire angle is appropriately performed, and the target tire angle δ * 1-δ * Assume that 4 corresponds to the actual tire angle.

[0087] The steering state determination unit 26 determines the target tire angle δ of each tire instructed by the target tire angle calculation control unit 25 instead of the detected tire angles δs1-δs4 of each tire. * 1-δ * Based on the detected tire angles δs1-δs4 and the target tire angle δs5, the steering state determination unit 26 determines whether the tires are in phase with each other based on the detected tire angles δs1-δs4 and the target tire angle δs6. This allows for a quick determination without being affected by communication delays from the tire angle sensors 671-674. * 1-δ * 4, two different determinations may be made regarding the in-phase state, and then the results of the determinations may be reconciled.

[0088] "The vehicle has a slip state determination unit 27, and a braking / driving force instruction unit 28 determines the braking / driving force instruction value F of the non-slip tire so as to cancel the yaw moment of the vehicle caused by the slip suppression process. * 1-F * In the embodiment, the driving / braking force control device according to the third embodiment in which the steering state determination unit 26 determines whether the tires are in phase with each other based on the detected tire angles δs1-δs4 may be combined with the driving / braking force control device according to the fourth embodiment in which the steering state determination unit 26 determines whether the tires are in phase with each other based on the detected tire angles δs1-δs4.

[0089] (Other embodiments) (a) In the first embodiment, the braking / driving force instruction unit 28 always acquires the center of gravity position detected by the center of gravity position detection device 40, and in the second embodiment, it does not always acquire the center of gravity position. In other embodiments, it is assumed that the vehicle 100 has the center of gravity position detection device 40, and the first embodiment and the second embodiment may be switched depending on the situation. For example, depending on the loading situation of occupants or luggage, etc., when there is a large change in the loading situation, the braking / driving force instruction unit 28 may acquire the center of gravity position detected by the center of gravity position detection device 40, and ... use an estimated value stored internally without acquiring the center of gravity position.

[0090] (b) In the third embodiment, slip state determination unit 27 determines whether each tire is in a slip state or not in a slip state. In other embodiments, the slip rate may be evaluated in further stages, and determined in three or more stages, for example, "heavy slip state, light slip state, no slip state." In the slip suppression process, the process may be divided, for example, so that the braking / driving force is reduced in a heavy slip state and the braking / driving force is maintained in a light slip state.

[0091] 1 and 2, braking / driving force control device 20 is shown as a higher-level control device for steering actuators 71-74 and braking / driving actuators 81-84. This configuration is not limiting, and braking / driving force control device 20 and the drive devices for each of steering actuators 71-74 or braking / driving actuators 81-84 may function together. For example, the drive devices for the four steering actuators 71-74 may communicate information with each other to cooperate to realize the function of braking / driving force control device 20.

[0092] (d) The independently steered vehicle or steered vehicle on which the braking / driving force control device 20 is mounted is not limited to a four-wheeled vehicle, but may be any "vehicle in which all tires of three or more wheels can be steered," including three-wheeled vehicles, six-wheeled vehicles, etc. For example, in a three-wheeled vehicle with one front wheel and left and right rear wheels, or left and right front wheels and one rear wheel, when the tire angles of the three wheels are all in phase, it is determined that the vehicle is in phase. Also, when the center of gravity is shifted from the geometric center of the three wheels during diagonal movement, yaw motion occurs, just like in a four-wheeled vehicle.

[0093] (e) "Vehicle" includes not only vehicles that run on public roads in accordance with steering signals from an automatic driving device or a driver operated by a steering wheel, but also green slow mobility vehicles and AGVs (automated guided vehicles) that run at low speeds in specific areas.

[0094] The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

[0095] Each control unit (target tire angle calculation control unit, turning state determination unit, braking / driving force instruction unit) and its method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, each control unit and its method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, each control unit and its method described in the present disclosure may be realized by one or more dedicated computers configured by combining a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0096] 20(201-204) Braking / driving force control device, 25...Target tire angle calculation control unit, 26... Steering state determination unit, 28... Braking / driving force instruction unit, 30 Yaw movement detection device, 40....Center of gravity position detection device, 671-676···Tire angle sensor, 71-76···Steering actuator, 81-84 Braking / driving actuator, 91-94 Tire, 100··· (four-wheel independent steering) vehicles, 105··· (four-wheel steering) vehicles.

Claims

1. A vehicle (100, 105) in which all three or more tires (91-94) are steerable and can be independently braked and driven by braking and driving forces (F1-F4) output by braking and driving actuators (81-84) corresponding to each tire, and which is equipped with a yaw motion detection device (30) that detects yaw motion and a center-of-gravity position detection device (40) that detects the center-of-gravity position of the vehicle, is provided with a braking and driving force control device that controls the braking and driving forces output by the braking and driving actuators, Based on the movement direction indication value, the target tire angle (δ ＊ 1-δ ＊ 4. δ ＊ 12. δ ＊ a target tire angle calculation control unit (25) that calculates the target tire angle (34) and issues an instruction to the steering actuators (71-76); a steering state determination unit (26) that determines whether or not the tires are in the same phase state based on the target tire angles of the tires instructed by the target tire angle calculation control unit or the detected tire angles (δs1-δs4, δs12, δs34) of the tires acquired from the tire angle sensors (671-676); The braking / driving force command value (F ＊ 1-F ＊ a braking / driving force instruction unit (28) that calculates the braking / driving force and issues an instruction to the braking / driving actuator; and When the steering state determination unit determines that the tires are in the same phase state, and when it is determined that a yaw motion of the vehicle is occurring or the occurrence of a yaw motion of the vehicle is predicted based on the information acquired from the yaw motion detection device, The braking / driving force command unit corrects the braking / driving force command value to be commanded to at least one of the braking / driving actuators based on the center of gravity position of the vehicle acquired from the center of gravity position detection device.

2. A braking / driving force control device for a vehicle (100, 105) in which all tires (91-94) of three or more wheels are steerable and can be independently braked / driven by braking / driving forces (F1-F4) output by braking / driving actuators (81-84) corresponding to each tire, and which is equipped with a yaw motion detection device (30) that detects yaw motion, the braking / driving force control device controls the braking / driving forces output by the braking / driving actuators, Based on the movement direction indication value, the target tire angle (δ ＊ 1-δ ＊ 4. δ ＊ 12. δ ＊ a target tire angle calculation control unit (25) that calculates the target tire angle (34) and issues an instruction to the steering actuators (71-76); a steering state determination unit (26) that determines whether or not the tires are in the same phase state based on the detected tire angles (δs1-δs4, δs12, δs34) of the tires acquired from the tire angle sensors (671-676); The braking / driving force command value (F ＊ 1-F ＊ a braking / driving force instruction unit (28) that calculates the braking / driving force and issues an instruction to the braking / driving actuator; and When the steering state determination unit determines that the tires are in the same phase state, and when it is determined that a yaw motion of the vehicle is occurring or the occurrence of a yaw motion of the vehicle is predicted based on the information acquired from the yaw motion detection device, The braking / driving force command unit is a braking / driving force control device that corrects the braking / driving force command value that is commanded to at least one of the braking / driving actuators.

3. The vehicle is equipped with a slip ratio detection device (50) that detects the slip ratio of each tire, The vehicle further includes a slip state determination unit (27) that determines whether each tire is in a slip state based on the slip ratio acquired from the slip ratio detection device, When the slip state determination unit determines that one or more tires are in a slip state, the one or more tires determined to be in a slip state are defined as slip tires, and the one or more tires other than the slip tires are defined as non-slipping tires. The braking / driving force instruction unit execute a slip suppression process to maintain or reduce the braking / driving force of the slipping tire; 3. The braking / driving force control device according to claim 1, wherein the braking / driving force command values ​​for the non-slip tires are corrected so as to cancel out the yaw moment of the vehicle caused by the slip suppression process.

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