Vehicle travelling direction detecting device

Abstract

To provide a vehicle travelling direction detecting device that detects the travelling direction of an oblique movement of a vehicle relative to a back-and-forth axis in an independent-steering-type vehicle.SOLUTION: In a vehicle in which each tire can independently turn, acceleration is produced by braking and driving force of each tire output by each of braking and driving actuators 81 to 84. A first acceleration sensor 35 and a second acceleration sensor 36 detect accelerations in a first axis and a second axis, respectively, which intersect with each other on a parallel plane to a road surface. A running instructing unit 25 of a vehicle travelling direction detecting device 20 instructs respective target tire angles δ*1 to δ*4 for respective turning actuators 71 to 74, and respective target braking and driving forces BD*1 to BD*4 for the respective braking and driving actuators 81 to 84. When braking and driving control is performed on a vehicle, an oblique movement angle calculating unit 26 calculates, based on the acceleration αx in the first axis obtained from the first acceleration sensor 35 and the acceleration αy in the second axis obtained from the second acceleration sensor 36, an oblique movement angle θ that is the angle of the travelling direction of the vehicle relative to the back-and-forth axis.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vehicle travel direction detection device. [Background technology]

[0002] Conventionally, there is known a technique for detecting a slip angle of a vehicle.

[0003] For example, a vehicle slip angle detection device disclosed in Patent Document 1 detects the vehicle slip angle using an angular velocity (gyro) sensor and an acceleration sensor provided in a sensor unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-248455 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 can detect the straight-line or turning of a general vehicle, but cannot detect the direction of diagonal movement relative to the front and rear axes of the vehicle, which is unique to independently steered vehicles. Note that in this specification, the term "vehicle" includes, from a technical point of view, any moving body that can run on the ground using wheels, regardless of the 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 vehicle travel direction detection device that detects the travel direction of oblique movement with respect to the front and rear axes of an independently steering vehicle. [Means for solving the problem]

[0007] A vehicle (100, 105, 107) to which the vehicle travel direction detection device according to the present invention is applied has three or more tires (91-94), and each tire can be steered independently by the steering torque output by the steering actuator (71-74) corresponding to each tire. In addition, acceleration occurs when the braking / driving force of each tire output by one or more braking / driving actuators (81-84, 85-86, 87) is transmitted to the road surface. "Acceleration" includes negative acceleration during deceleration due to braking.

[0008] The vehicle includes a first acceleration sensor (35) and a second acceleration sensor (36) for detecting accelerations of a first axis and a second axis that intersect with each other on a plane parallel to the road surface. The vehicle travel direction detection device detects the travel direction of the vehicle in the diagonal movement with respect to the front-rear axis.

[0009] The vehicle travel direction detection device includes a travel instruction unit (25) and a diagonal movement angle calculation unit (26). The travel instruction unit calculates a target tire angle (δ) with respect to the steering actuator. * 1-δ * 4), and the target braking / driving force (BD * 1-BD * 4) is instructed.

[0010] The diagonal movement angle calculation unit calculates a diagonal movement angle (θ), which is the angle of the traveling direction with respect to the front-rear axis of the vehicle, based on the acceleration of the first axis (αx) obtained from the first acceleration sensor and the acceleration of the second axis (αy) obtained from the second acceleration sensor when the vehicle is braking or driving.

[0011] The vehicle travel direction detection device of the present invention can detect the travel direction of oblique movement in an independently steering vehicle by using two-axial acceleration detected during braking and driving. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a vehicle equipped with a vehicle travel direction detection device according to a first embodiment. [Diagram 2]A diagram showing (a) diagonal movement and (b) lateral movement in an independently steered vehicle. [Diagram 3] 1 is a block diagram of a vehicle traveling direction detection device according to a first embodiment. [Figure 4] 4A and 4B are diagrams for explaining acceleration generated when accelerating while traveling straight and while traveling obliquely; [Diagram 5] 1 is a diagram showing the relationship between vehicle speed, X-axis acceleration, Y-axis acceleration, and diagonal movement angle. [Figure 6] 4 is a flowchart showing a process performed by the vehicle travel direction detection device. [Figure 7] FIG. 6 is a block diagram of a vehicle traveling direction detection device according to a second embodiment. [Figure 8] FIG. 4 is a diagram illustrating lateral acceleration due to turning. [Figure 9] FIG. 11 is a block diagram of a vehicle traveling direction detection device according to a third embodiment. [Figure 10] FIG. 13 is a block diagram of a vehicle traveling direction detection device according to a fourth embodiment. [Figure 11] FIG. 4 is a rear view of a vehicle illustrating the effect of a cross gradient on acceleration. [Figure 12] FIG. 4 is a side view of a vehicle illustrating the effect of a longitudinal gradient on acceleration. [Figure 13] FIG. 13 is a diagram showing an arrangement of braking / driving actuators in another embodiment. [Figure 14] FIG. 13 is a diagram showing the configuration of a braking / driving actuator in another embodiment. [Figure 15] 13A and 13B are diagrams showing examples of setting the first axis and the second axis in another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A number of embodiments of a vehicle travel direction detection device will be described with reference to the drawings. In the number of embodiments, substantially the same configurations are given the same reference numerals and descriptions thereof will be omitted. The following first to fourth embodiments will be collectively referred to as "the present embodiment." The vehicle travel direction detection device of the present embodiment is a device that detects the travel direction of oblique movement with respect to the front and rear axes of a vehicle in an independently steerable vehicle in which three or more tires can be independently steered, typically a four-wheel independently steerable vehicle.

[0014] (First embodiment) The configuration of an independently steerable vehicle 100 on which a vehicle travel direction detection device 20 of the first embodiment is mounted will be described with reference to Fig. 1. The vehicle 100 shown in Fig. 1 has four tires 91-94, and each tire 91-94 can be steered independently and can be independently braked and driven. 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 each element below and the suffixes "1" to "4" of each symbol correspond to the tires 91-94 of FL, FR, RL, and RR, respectively.

[0015] Vehicle 100 is equipped with steering actuators 71-74, braking / driving actuators 81-84, and tire angle sensors 671-674 that detect actual tire angles (hereinafter "actual tire angles") corresponding to the tires 91-94. In the drawing, "actuator" is written as "Act." 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.

[0016] 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.

[0017] 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. Acceleration occurs when the braking / driving forces of the tires 91-94 output by the braking / driving actuators 81-84 are transmitted to the road surface. Hereinafter, "acceleration" includes positive acceleration during acceleration due to driving, as well as negative acceleration during deceleration due to braking.

[0018] 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.

[0019] Here, we define a "first axis" and a "second axis" that intersect with each other on a plane parallel to the road surface. In this embodiment, the X-axis, which is the front-rear axis (vertical axis) of the vehicle 100, is defined as the first axis, and the Y-axis, which is the left-right axis (horizontal axis) of the vehicle 100, is defined as the second axis. Therefore, in this embodiment, the first axis and the second axis are perpendicular to each other. The vehicle 100 is equipped with a first acceleration sensor 35 that detects the X-axis acceleration αx, which is the "acceleration of the first axis," and a second acceleration sensor 36 that detects the Y-axis acceleration αy, which is the "acceleration of the second axis."

[0020] A moving direction indication value by a steering wheel operation by a driver or a steering signal of an autonomous vehicle is input to the vehicle moving direction detection device 20. Based on the moving direction indication value, the vehicle moving direction detection device 20 calculates a target tire angle δ for the steering actuators 71-74. * 1-δ * 4, and the target braking / driving force BD for the braking / driving actuators 81-84. * 1-BD * Specify 4.

[0021] The vehicle travel direction detection device 20 calculates a "diagonal movement angle", which is the angle of the travel direction with respect to the front and rear axes of the vehicle 100, based on the two-axial accelerations αx, αy obtained from the acceleration sensors 35, 36 when the vehicle 100 is driven or braked (i.e., when driving or braking).

[0022] The vehicle travel direction detection device 20 also obtains the detected tire angles δs1-δs4 of the tires 91-94 detected by the tire angle sensors 671-674. The vehicle travel direction detection device 20 calculates the target tire angle δs1-δs4 from the oblique movement angle and the detected tire angles δs1-δs4. *1-δ * 4 is corrected, and the corrected target tire angle δ ** 1-δ ** 4 is instructed to the steering actuators 71-74.

[0023] Next, before describing the detailed configuration of vehicle travel direction detection device 20, the significance of detecting the travel direction of diagonal movement in independently steered vehicle 100 will be described. Conventionally, in a typical vehicle, a pair of left and right tires are mechanically connected via a link, and the tires are steered by steering the steering wheel. In the future, it is expected that developments will progress to steer-by-wire, in which the steering wheel and the link between the pair of left and right tires are mechanically separated, and to four-wheel independently steered vehicles in which the left and right rear wheels can be steered independently in addition to the left and right front wheels.

[0024] A four-wheel independently steering vehicle is capable of diagonal movement as shown in FIG. 2(a) and lateral movement as shown in FIG. 2(b). In diagonal movement, all tires 91-94 are steered to the same tire angle with an absolute value of less than 90 degrees. In lateral movement, all tires 91-94 are steered to an absolute value of 90 degrees. For example, diagonal movement is effective for changing driving lanes, and lateral movement is effective for parallel parking. In the following figures, the front side of an independently steering vehicle 100 is illustrated in a streamlined shape. The characters "front / rear" and "center of gravity" of the vehicle are only shown in FIG. 2(a) and are omitted in subsequent figures.

[0025] In order for an independently steered vehicle to travel diagonally or laterally, the actual tire angle must be accurately detected by the tire angle sensors 671-674 and the target tire angle δ must be accurately set. * 1-δ * 4, feedback control is required. However, due to improper installation of tire angle sensors 671-674 or improper adjustment of steering actuators 71-74, there is a possibility that the detected tire angles δs1-δs4 may deviate from the actual tire angles. This may result in diagonal movement even when the vehicle is intended to be traveling straight, or the direction of the diagonal movement may deviate from the intended direction. In addition, if some tire angles deviate from the average tire angle of the entire vehicle, driving loss may increase or unwanted vehicle behavior such as yaw may occur.

[0026] Therefore, the object of this embodiment is to correctly detect the direction of diagonal movement relative to the vehicle front and rear axes even when there is a detection error in the tire angle sensors 671-674 in the independently steered vehicle 100. To this end, the vehicle traveling direction detection device 20 of this embodiment calculates the angle of diagonal movement based on the X-axis acceleration αx and the Y-axis acceleration αy detected by the two-axis acceleration sensors 35, 36 when the vehicle 100 is accelerated or decelerated while braking or driving.

[0027] The configuration and operation of the vehicle traveling direction detection device 20 will be described with reference to Fig. 3 to Fig. 6. As shown in Fig. 3, the vehicle traveling direction detection device 20 of the first embodiment has a driving instruction unit 25, a diagonal movement angle calculation unit 26, and, as an optional configuration, a target tire angle correction unit 27. The basic configuration of the vehicle traveling direction detection device 20 of the second to fourth embodiments is the same as that of the first embodiment, but the device is mounted on a vehicle 100 further equipped with other additional devices, and processing using information acquired from the additional devices is added.

[0028] The travel instruction unit 25 determines the target tire angle δ for the steering actuators 71-74 based on the input travel direction instruction value. * 1-δ * 4, and the target braking / driving force BD for the braking / driving actuators 81-84. * 1-BD * The driving instruction unit 25 also notifies the oblique movement angle calculation unit 26 of driving angle and acceleration / deceleration instruction information. * 1-δ * 4 is reflected in the driving angle instruction information, and the target braking / driving force BD * 1-BD * 4 is reflected in the acceleration / deceleration instruction information.

[0029] The diagonal movement angle calculation unit 26 recognizes that the vehicle 100 is being braked or driven based on acceleration / deceleration instruction information from the driving instruction unit 25. When the vehicle 100 is being braked or driven, the diagonal movement angle calculation unit 26 acquires an X-axis acceleration αx from the first acceleration sensor 35 and an Y-axis acceleration αy from the second acceleration sensor 36. The diagonal movement angle calculation unit 26 calculates a diagonal movement angle θ based on the acquired two-axis accelerations αx and αy.

[0030] With reference to Fig. 4 and Fig. 5, the calculation of the accelerations αx, αy, and the diagonal movement angle θ that occur when accelerating while traveling straight and diagonally will be described. The vehicle acceleration α is the acceleration in the vehicle's traveling direction on the XY plane including the X-axis and the Y-axis. Regarding the setting of the positive and negative of the X-axis and the Y-axis, the forward direction of the X-axis is shown as positive. On the other hand, it is acceptable to appropriately select whether the rightward or leftward direction of the Y-axis is positive. Since expressing acceleration in the negative direction as a negative value may be mistaken for a deceleration operation, the direction of the Y-axis where the Y-axis acceleration αy occurs is regarded as the positive direction in each case, and the description will be given as "αy≧0".

[0031] When accelerating while driving straight ahead as shown in the upper part of Figure 4, the vehicle acceleration α and the X-axis acceleration αx have the same value as shown in equation (1.1). The diagonal movement angle θ is calculated as 0 [m / s 2 ]

[0032] α = αx (1.1) θ=cos -1 (αx / α) = 0 (1.2)

[0033] In this way, when the acceleration of one of the first and second axes is in the vehicle travel direction, the acceleration may be calculated from a relational expression between the vehicle drive torque and the mass, or from the time derivative of the wheel rotation speed.

[0034] On the other hand, when accelerating during diagonal traveling as shown in the lower part of Fig. 4, the vehicle acceleration α is calculated by equation (1.3), and the diagonal movement angle θ is calculated by equation (1.4). Therefore, based on the two-axial accelerations αx, αy detected by the acceleration sensors 35, 36, the diagonal movement angle θ is calculated, and it is possible to determine whether the vehicle is traveling straight ahead or diagonally.

[0035] α = √(αx 2 +αy 2 ) (1.3) θ=cos -1 (αx / α) (1.4)

[0036] In FIG. 5, the dashed line shows the vehicle speed V, the X-axis acceleration αx, the Y-axis acceleration αy, and the diagonal movement angle θ according to the formula (1.4) when accelerating at a constant vehicle acceleration α while driving straight ahead, and the solid line shows the CAE analysis results when driving diagonally. The vehicle acceleration α is commonly set to 1 [m / s 2 ], and the driving angle indication value when driving diagonally is 5[deg].

[0037] 1 [m / s 2 When the vehicle accelerates with a vehicle acceleration of α, the X-axis acceleration αx is 1 [m / s 2 ], Y-axis acceleration αy is 0 [m / s 2 On the other hand, when traveling diagonally, the speed is 1 [m / s 2 When the vehicle accelerates with a vehicle acceleration of α, the X-axis acceleration αx is 0.996 [m / s 2 ], and the Y-axis acceleration αy is 0.09 [m / s 2 The diagonal movement angle θ calculated by formula (1.4) is equal to the travel angle command value, which is 5 [deg].

[0038] The target tire angle correction unit 27 stores the oblique movement angle θ calculated by the oblique movement angle calculation unit 26. The target tire angle correction unit 27 also acquires the detected tire angles δs1-δs4 of each tire 91-94 detected by the tire angle sensors 671-674, and calculates the deviation from the oblique movement angle θ. The target tire angle correction unit 27 calculates the target tire angle δs1-δs4 of each tire 91-94 according to the deviation between the oblique movement angle θ and the detected tire angles δs1-δs4. * 1-δ * Corrected target tire angle δ after correcting 4 ** 1-δ ** 4. Then, the target tire angle correction unit 27 calculates the corrected target tire angle δ ** 1-δ ** In this manner, the target tire angle δs1-δs4 is determined by feedback control of the detected tire angles δs1-δs4. ** 1-δ ** 4 is corrected.

[0039] 6 is a flowchart showing the process performed by the vehicle travel direction detection device 20. In the explanation of the flowchart, the symbol "S" means a step. This process is repeatedly performed while the vehicle 100 is traveling, from when it starts traveling until it stops.

[0040] In S1, the driving instruction unit 25 determines the target tire angle δ for the steering actuators 71-74 based on the movement direction instruction value. * 1-δ * 4, and the target braking / driving force BD for the braking / driving actuators 81-84. * 1-BD * In S2, the vehicle 100 travels in the instructed movement direction in accordance with the operations of the steering actuators 71-74 and the braking / driving actuators 81-84.

[0041] In S3, the target braking / driving force BD * 1-BD * It is determined whether an acceleration / deceleration command is being output by S4, i.e., whether the vehicle is currently in driving or braking mode. If an acceleration / deceleration command is not being output and the vehicle is traveling at a constant speed, the result in S3 is NO and the routine ends. If an acceleration command by driving or a deceleration command by braking is being output, the result in S3 is YES and the routine proceeds to S4.

[0042] In S4, the diagonal movement angle calculation unit 26 acquires the X-axis acceleration αx from the first acceleration sensor 35, and acquires the Y-axis acceleration αy from the second acceleration sensor 36. In S5, the diagonal movement angle calculation unit 26 calculates the diagonal movement angle θ based on the acquired X-axis acceleration αx and Y-axis acceleration αy.

[0043] In S6, the target tire angle correction unit 27 acquires the detected tire angles δs1-δs4 of each tire 91-94. In S7, the target tire angle correction unit 27 calculates the target tire angle δs1-δs4 of each tire 91-94 according to the deviation between the oblique movement angle θ calculated by the oblique movement angle calculation unit 26 and the detected tire angles δs1-δs4. * 1-δ * Corrected target tire angle δ after correcting 4 ** 1-δ **In step S8, the target tire angle correction unit 27 calculates the corrected target tire angle δ ** 1-δ ** 4 is instructed to the steering actuators 71-74.

[0044] As described above, the vehicle traveling direction detection device 20 calculates the diagonal movement angle θ using the two-axial accelerations αx, αy detected during braking and driving in the independently steered vehicle 100. For example, even if the detected tire angles δs1-δs4 are misaligned with the actual tire angles due to improper installation of the tire angle sensors 671-674, the traveling direction of the diagonal movement can be detected. This makes it possible to determine whether the traveling direction of the vehicle 100 is the intended direction.

[0045] In addition, the calculated oblique movement angle θ is used to calculate the target tire angle δ * 1-δ * By correcting 4 and issuing a command to the steering actuators 71-74, the vehicle 100 can be moved in the intended direction without mechanically adjusting the alignment of the steering actuators 71-74.

[0046] Second embodiment A second embodiment will be described with reference to Fig. 7 and Fig. 8. As shown in Fig. 7, a vehicle travel direction detection device 20 is mounted on a vehicle equipped with a vehicle speed detection device 40 that detects a vehicle speed V, and a yaw rate detection device 45 that detects a yaw rate γ of the vehicle. The oblique movement angle calculation unit 26 corrects the X-axis acceleration αx and the Y-axis acceleration αy using the vehicle speed V acquired from the vehicle speed detection device 40 and the yaw rate γ acquired from the yaw rate detection device 45. Specifically, mainly the Y-axis acceleration αy is corrected.

[0047] In the example shown in Fig. 8, tire angles δ1, δ2, and δ3 other than the right rear wheel 94 are steered equally to the right, and only the tire angle δ4 of the right rear wheel 94 is steered excessively to the right. In this case, the vehicle 100 turns counterclockwise while moving diagonally. In this way, when some tire angles deviate from the average tire angle of the entire vehicle, a turn (yaw motion) occurs, and an error in the diagonal movement angle θ occurs due to the acceleration αyaw caused by the turn.

[0048] In FIG. 8, the yaw rate γ (rad / s) is expressed by the formula (2.1) using the vehicle speed V (m / s) and the turning radius R (m). 2 ) is expressed by equation (2.2) using vehicle speed V (m / s) and yaw rate γ (rad / s). For example, when the vehicle speed V = 22.2 m / s, turning radius R = 1000 m, and yaw rate γ = 0.022 (rad / s), the generated acceleration αyaw is 0.49 m / s 2 It becomes.

[0049] γ = V / R (2.1) αyaw=Vγ=V 2 / R (2.2)

[0050] In the second embodiment, the acceleration αyaw due to turning is calculated using the vehicle speed V and the yaw rate γ, and a correction is made to remove the acceleration error due to turning from the accelerations αx and αy detected by the acceleration sensors 35 and 36, thereby improving the accuracy of the diagonal movement angle θ.

[0051] (Third and fourth embodiments) 9 to 12, the third and fourth embodiments will be described. When the road on which the vehicle 100 is traveling is inclined, the X-axis acceleration αx and the Y-axis acceleration αy detected by the acceleration sensors 35 and 36 contain acceleration components generated by the road gradient, which results in an error in the diagonal movement angle θ.

[0052] Therefore, in the third and fourth embodiments, the diagonal movement angle calculation unit 26 corrects the X-axis acceleration αx and the Y-axis acceleration αy using the road gradient angle. In other words, the accuracy of the diagonal movement angle θ can be improved by correcting the accelerations αx and αy detected by the acceleration sensors 35 and 36 to remove the acceleration error caused by the road gradient. The third and fourth embodiments may be combined with the second embodiment in which the accelerations αx and αy are corrected using the vehicle speed V and the yaw rate γ.

[0053] The third and fourth embodiments differ in the way in which the diagonal movement angle calculation unit 26 acquires the road gradient angle. In the third embodiment shown in Fig. 9, the vehicle travel direction detection device 20 is mounted on a vehicle equipped with a road gradient angle detection device 50 that detects the road gradient angle. For example, the road gradient angle detection device 50 detects the road gradient angle using map information including road surface gradient information and a coordinate detection sensor (GPS).

[0054] In FIG. 11, which shows the rear view of the vehicle, the gradient angle in a cross section perpendicular to the longitudinal axis of the vehicle 100 is represented as a transverse gradient angle ψs. The acceleration αs due to the transverse gradient is calculated by multiplying the acceleration of gravity g (≈9.8 m / s 2 For example, when the cross slope angle ψs is 1.17 deg, the acceleration αs due to the cross slope is 0.2 m / s 2 It becomes.

[0055] αs = g sinψs (3.1)

[0056] Similarly, in Fig. 12, which shows a side view of the vehicle, the gradient angle in a cross section along the longitudinal axis of the vehicle 100 is represented as the longitudinal gradient angle ψf. The acceleration αf due to the longitudinal gradient is expressed by the formula (3.2) using the gravitational acceleration g. For example, when the longitudinal gradient angle ψf is 6.84 deg (gradient 12%), the acceleration αf due to the longitudinal gradient is 1.17 m / s 2 It becomes.

[0057] αf = g sinψf (3.2)

[0058] The oblique movement angle calculation unit 26 uses the road gradient angles ψs, ψf obtained from the road gradient angle detection device 50 to correct the X-axis acceleration αx and the Y-axis acceleration αy so as to remove the acceleration error caused by the road gradient.

[0059] In the fourth embodiment shown in Fig. 10, the vehicle travel direction detection device 20 is mounted on a vehicle equipped with a third acceleration sensor 37 that detects acceleration of a third axis perpendicular to the road surface. The third axis is perpendicular to the first and second axes on a plane parallel to the road surface, i.e., the X-axis and Y-axis in this embodiment. In the fourth embodiment, the third axis is represented as the Z-axis, and the acceleration of the third axis is represented as the Z-axis acceleration αz.

[0060] In Figure 11, "αz = g cosψs" and "ψs = cos -1 Since the acceleration αs due to the transverse gradient is calculated using the formula (3.1), the acceleration αs due to the transverse gradient can be calculated from the Z-axis acceleration αz using the formula (4). The calculation of the acceleration αf due to the longitudinal gradient in FIG. 12 is similar.

[0061] αs = √(g 2 -αz 2 ) ···(4)

[0062] The oblique movement angle calculation unit 26 corrects the X-axis acceleration αx and the Y-axis acceleration αy using the road gradient angles ψs, ψf estimated based on the Z-axis acceleration αz acquired from the third acceleration sensor 37.

[0063] (Other embodiments) (a) The braking / driving actuators need not be provided individually for each tire 91-94 as long as they can generate acceleration in the vehicle 100 by transmitting the braking / driving force output to each tire 91-94 to the road surface. In other words, the tires 91-94 are independently steered but do not need to be independently braked or driven.

[0064] An independently steering vehicle 105 shown in Fig. 13 is equipped with a front wheel braking / driving actuator 85 that outputs a common braking / driving force to left and right front tire 91, 92, and a rear wheel braking / driving actuator 86 that outputs a common braking / driving force to left and right rear tire 93, 94. An independently steering vehicle 107 shown in Fig. 14 is equipped with a four wheel braking / driving actuator 87 that outputs a common braking / driving force to all four tire 91-94. For example, the main motor or engine corresponds to the four wheel drive actuator, and a hydraulic pressure generating device that distributes brake hydraulic pressure to the four wheels corresponds to the four wheel braking actuator.

[0065] The vehicle travel direction detection device 20 is also applied to these vehicles 105 and 107. When applied to the vehicle 105, the target braking / driving force BD * 1 and BD * 2 are the same value, and the target braking / driving force BD * 3 and BD * When applied to the vehicle 107, the target braking / driving force BD * 1-BD * 4 is the same value.

[0066] Furthermore, the brakes and the drive motors do not necessarily have to be provided as a set. For example, four electric brakes may be provided for each tire, and two drive motors may be provided, one for each of the left and right front wheels and one for each of the left and right rear wheels.

[0067] (b) The "first and second axes intersecting each other on a plane parallel to the road surface" along which acceleration is detected by the acceleration detection device are not limited to the mutually orthogonal X-axis and Y-axis. As shown in Fig. 15, the p-axis and q-axis, which are non-orthogonal axes, may be set as the first and second axes. The phase of the vehicle acceleration α, which is a resultant vector of the p-axis acceleration αp and the q-axis acceleration αq, is calculated as the oblique movement angle θ.

[0068] (c) If there is no need to correct the traveling direction of the vehicle 100 based on the oblique movement angle θ calculated by the oblique movement angle calculation unit 26, the vehicle traveling direction detection device 20 does not need to include the target tire angle correction unit 27.

[0069] (d) In Fig. 1, vehicle travel direction detection device 20 is shown as a higher-level control device of steering actuators 71-74. This configuration is not limiting, and vehicle travel direction detection device 20 and the drive devices of each steering actuator 71-74 may function as one unit. For example, the drive devices of the four steering actuators 71-74 may communicate information with each other to cooperate and realize the function of vehicle travel direction detection device 20.

[0070] (e) The independently steered vehicle on which the vehicle travel direction detection device 20 is mounted is not limited to a four-wheeled vehicle, but may be any "vehicle with three or more wheels that can be steered independently," including three-wheeled vehicles, six-wheeled vehicles, etc. "Vehicles" include not only vehicles that run on public roads following the steering wheel operation by a driver or the steering signal of an automatic driving device, but also green slow mobility and AGVs (automated guided vehicles) that run at low speeds in specific areas.

[0071] 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.

[0072] The disclosure of "a vehicle travel direction detection device mounted on a vehicle equipped with a vehicle speed detection device (40) that detects a vehicle speed, and a yaw rate detection device (45) that detects a yaw rate of the vehicle, wherein the diagonal movement angle calculation unit corrects the acceleration of the first axis and the second axis using the vehicle speed acquired from the vehicle speed detection device and the yaw rate acquired from the yaw rate detection device" corresponding to the second embodiment may be combined with the disclosure of "a vehicle travel direction detection device mounted on a vehicle equipped with a road gradient angle detection device (50) that detects a road gradient angle, wherein the diagonal movement angle calculation unit corrects the acceleration of the first axis and the second axis using the road gradient angles (ψs, ψf) acquired from the road gradient angle detection device" corresponding to the third embodiment.

[0073] The disclosure of "a vehicle travel direction detection device mounted on a vehicle equipped with a vehicle speed detection device (40) that detects a vehicle speed and a yaw rate detection device (45) that detects a yaw rate of the vehicle, the diagonal movement angle calculation unit corrects the acceleration of the first axis and the second axis using the vehicle speed acquired from the vehicle speed detection device and the yaw rate acquired from the yaw rate detection device" corresponding to the second embodiment may be combined with the disclosure of "a vehicle travel direction detection device mounted on a vehicle equipped with a third acceleration sensor (37) that detects the acceleration of a third axis perpendicular to a road surface, the diagonal movement angle calculation unit corrects the acceleration of the first axis and the second axis using a road gradient angle (ψs, ψf) estimated based on the acceleration of the third axis (αz) acquired from the third acceleration sensor" corresponding to the fourth embodiment.

[0074] Each control unit (travel instruction unit, diagonal movement angle calculation unit, target tire angle correction 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 a combination of 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]

[0075] 20 Vehicle travel direction detection device, 25... Driving instruction unit, 26...diagonal movement angle calculation unit, 27...target tire angle correction unit, 35... first acceleration sensor, 36... second acceleration sensor, 71-74 ···Steering actuator, 81-84, 85-86, 87... Braking / driving actuator, 91-94···Tires, 100, 105, 107... (independent steering) vehicles, αx: X-axis acceleration (acceleration of the first axis), αy: Y-axis acceleration (acceleration of the second axis).

Claims

1. A vehicle (100, 105, 107) is provided with three or more tires (91-94), each of which can be steered independently by a steering torque output from a steering actuator (71-74) corresponding to each tire, and acceleration is generated when the braking / driving force of each tire output from one or more braking / driving actuators (81-84, 85-86, 87) is transmitted to a road surface, and the vehicle is provided with a first acceleration sensor (35) and a second acceleration sensor (36) that respectively detect accelerations of a first axis and a second axis that intersect with each other in a plane parallel to the road surface. The vehicle travel direction detection device detects the travel direction of a diagonal movement relative to the front and rear axes of the vehicle and controls the travel of the vehicle, The target tire angle (δ ＊ 1-δ ＊ 4), and the target braking / driving force (BD ＊ 1-BD ＊ a travel instruction unit (25) that instructs the driver to an oblique movement angle calculation unit (26) that calculates an oblique movement angle (θ) that is the angle of the traveling direction with respect to a longitudinal axis of the vehicle based on the acceleration (αx) of the first axis acquired from the first acceleration sensor and the acceleration (αy) of the second axis acquired from the second acceleration sensor when braking or driving the vehicle; a target tire angle correction unit (27) that acquires detected tire angles (δs1-δs4) of the respective tires detected by tire angle sensors (671-674), corrects the target tire angle in accordance with the oblique movement angle calculated by the oblique movement angle calculation unit, and instructs the steering actuator of a corrected target tire angle (δ**1-δ**4); A vehicle travel direction detection device having the same.

2. A vehicle (100, 105, 107) is provided with three or more tires (91-94), each of which can be steered independently by a steering torque output from a steering actuator (71-74) corresponding to each tire, and acceleration is generated when the braking / driving force of each tire output from one or more braking / driving actuators (81-84, 85-86, 87) is transmitted to a road surface, and the vehicle is provided with a first acceleration sensor (35) and a second acceleration sensor (36) that respectively detect accelerations of a first axis and a second axis that intersect with each other in a plane parallel to the road surface. The vehicle travel direction detection device detects the travel direction of a diagonal movement relative to the front and rear axes of the vehicle and controls the travel of the vehicle, The vehicle is equipped with a vehicle speed detection device (40) for detecting the vehicle speed and a yaw rate detection device (45) for detecting the yaw rate of the vehicle, The target tire angle (δ ＊ 1-δ ＊ 4), and the target braking / driving force (BD ＊ 1-BD ＊ a travel instruction unit (25) that instructs the driver to an oblique movement angle calculation unit (26) that calculates an oblique movement angle (θ) that is the angle of the traveling direction with respect to a longitudinal axis of the vehicle based on the acceleration (αx) of the first axis acquired from the first acceleration sensor and the acceleration (αy) of the second axis acquired from the second acceleration sensor when braking or driving the vehicle; and The diagonal movement angle calculation unit calculates the acceleration (αyaw) due to turning that occurs during the diagonal movement of the vehicle using the vehicle speed obtained from the vehicle speed detection device and the yaw rate obtained from the yaw rate detection device, and performs a correction to remove errors in the acceleration due to turning from the acceleration of the first axis and the second axis.

3. A vehicle (100, 105, 107) is provided with three or more tires (91-94), each of which can be steered independently by a steering torque output from a steering actuator (71-74) corresponding to each tire, and acceleration is generated when the braking / driving force of each tire output from one or more braking / driving actuators (81-84, 85-86, 87) is transmitted to a road surface, and the vehicle is provided with a first acceleration sensor (35) and a second acceleration sensor (36) that respectively detect accelerations of a first axis and a second axis that intersect with each other in a plane parallel to the road surface. The vehicle travel direction detection device detects the travel direction of a diagonal movement relative to the front and rear axes of the vehicle and controls the travel of the vehicle, The road gradient angle detection device (50) is mounted on a vehicle equipped with the road gradient angle detection device (50), The target tire angle (δ ＊ 1-δ ＊ 4), and the target braking / driving force (BD ＊ 1-BD ＊ a travel instruction unit (25) that instructs the driver to an oblique movement angle calculation unit (26) that calculates an oblique movement angle (θ) that is the angle of the traveling direction with respect to a longitudinal axis of the vehicle based on the acceleration (αx) of the first axis acquired from the first acceleration sensor and the acceleration (αy) of the second axis acquired from the second acceleration sensor when braking or driving the vehicle; and The diagonal movement angle calculation unit corrects the acceleration of the first axis and the second axis using the road gradient angle (ψs, ψf) acquired from the road gradient angle detection device.

4. A vehicle (100, 105, 107) has three or more tires (91-94), each of which can be steered independently by a steering torque output from a steering actuator (71-74) corresponding to each tire, and acceleration is generated when the braking / driving force of each tire output from one or more braking / driving actuators (81-84, 85-86, 87) is transmitted to a road surface, and the vehicle (100, 105, 107) is equipped with a first acceleration sensor (35) and a second acceleration sensor (36) that respectively detect accelerations of a first axis and a second axis that intersect with each other in a plane parallel to the road surface, and a third acceleration sensor (37) that detects accelerations of a third axis that is perpendicular to the road surface, the vehicle travel direction detection device detecting the travel direction of a diagonal movement relative to the front and rear axes of the vehicle and controlling the travel of the vehicle, The target tire angle (δ ＊ 1-δ ＊ 4), and the target braking / driving force (BD ＊ 1-BD ＊ a travel instruction unit (25) that instructs the driver to an oblique movement angle calculation unit (26) that calculates an oblique movement angle (θ) that is the angle of the traveling direction with respect to a longitudinal axis of the vehicle based on the acceleration (αx) of the first axis acquired from the first acceleration sensor and the acceleration (αy) of the second axis acquired from the second acceleration sensor when braking or driving the vehicle; and The diagonal movement angle calculation unit corrects the acceleration of the first axis and the acceleration of the second axis using a road gradient angle (ψs, ψf) estimated based on the acceleration of the third axis (αz) acquired from the third acceleration sensor.

5. The tire angle sensors (671-674) acquire the detected tire angles (δs1-δs4) of the respective tires, and calculate the corrected target tire angles (δ) obtained by correcting the target tire angles in accordance with the oblique movement angles calculated by the oblique movement angle calculation unit. ＊＊ 1-δ ＊＊ 5. The vehicle traveling direction detection device according to claim 2, further comprising a target tire angle correction unit (27) that instructs the steering actuator to set a target tire angle.

Images