Stuck Escape Control System

Abstract

We provide a stack escape control system that enables efficient stack escape. [Solution] When a vehicle gets stuck (YES in ST1), the drive motor periodically applies forward and reverse rotational driving force to the non-stuck drive wheels (ST3). While this periodic driving force is being applied, the ground contact load of the stuck drive wheel is estimated based on the vehicle's attitude angle. At the timing when this estimated ground contact load of the drive wheel increases to a predetermined escape load (YES in ST4), the drive motor applies driving force to the stuck wheel (ST5). This ensures that sufficient ground contact force is maintained on the stuck wheel, allowing the driving force to be transmitted to the road surface and enabling the wheel to escape from being stuck.

Description

Technical Field

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[0001] The present invention relates to a stack escape control system. In particular, the present invention relates to an improvement in control for stack escape in a vehicle capable of applying independent driving forces to each wheel.

Background Art

[0002] Conventionally, control for a vehicle to escape from a stack (for example, a state where one wheel has entered a recess in the road surface and cannot escape; hereinafter, it may also be referred to as "the wheel is in a stack" or "the driving wheel is in a stack") has been proposed.

[0003] For example, in Patent Document 1, when an automatic start switch is turned on by a driver and automatic start control is executed, control is performed to control the driving torque and braking torque of the stacked driving wheel (control to gradually decrease the braking torque after the driving torque can be sufficiently generated), thereby causing the driving wheel to escape from the stack.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors of the present invention have considered a more efficient stack escape method. As a result, they have arrived at the finding that by effectively using both the stacked driving wheel and the non-stacked driving wheel, it is possible to efficiently escape from the stack.

[0006] The present invention has been made in view of this point, and an object thereof is to provide a stack escape control system that enables efficient stack escape. [Means for solving the problem]

[0007] The present invention provides a solution for achieving the above objectives, based on a stack escape control system for freeing a stuck vehicle from the stack. This stack escape control system is characterized by comprising: a driving force application means capable of individually applying driving force to each wheel; a grip driving wheel control unit that applies a predetermined driving force from the driving force application means to the wheels that are not stuck; a ground load estimation unit that estimates the ground load on the stuck wheels; and a stack driving wheel control unit that applies driving force from the driving force application means to the stuck wheels, provided that the ground load estimation unit has increased the ground load to a predetermined escape load.

[0008] This specific mechanism ensures that, when a vehicle becomes stuck, a predetermined driving force is first applied to the wheels that are not stuck. This causes a change in the ground contact load of the stuck wheel. This change in ground contact load is estimated by a ground contact load estimation unit, and when it increases to a predetermined load that allows for escape, a driving force is applied to the stuck wheel. This ensures that the driving force of the stuck wheel is transmitted to the road surface while sufficient ground contact force is maintained, making it possible to free that wheel from being stuck. In this way, by effectively utilizing the driving force of the wheels that are not stuck and optimizing the timing of applying driving force to the stuck wheel, efficient escape from being stuck becomes possible. [Effects of the Invention]

[0009] In this invention, a predetermined driving force is applied to the wheels that are not stuck, and only when the ground contact load on the stuck wheels increases to a predetermined load that allows for escape does the driving force to be applied to the stuck wheels. This effectively utilizes the driving force of the wheels that are not stuck and optimizes the timing of applying the driving force to the stuck wheels, thereby enabling efficient escape from being stuck. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1(a) shows the first stuck state, Figure 1(b) shows the second stuck state, and Figure 1(c) shows the unstuck state. [Figure 2] This is a block diagram showing a schematic configuration of a stack escape control system according to an embodiment. [Figure 3] This is a flowchart illustrating the procedure for escaping a stack. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the drawings. This embodiment describes the case in which the present invention is applied to a vehicle that employs a drive system in which each of the four wheels has a built-in drive motor (referred to as an in-wheel motor). In this embodiment, the case in which the left front wheel gets stuck will be used as an example of vehicle getting stuck.

[0012] Figure 1(a) is a side view showing vehicle V in a stuck state. First, to briefly explain the drive system of vehicle V, vehicle V according to this embodiment employs an in-wheel motor system in which drive motors (in-wheel motors: means of providing driving force) M1, M2, M3, M4 (see Figure 2) are built into each of the four wheels (drive wheels) W1, W2. The configuration of drive motors M1 to M4 is a well-known configuration that includes, for example, a stator fixed to the body of vehicle V, a rotor that rotates with the tire, and a planetary gear reduction mechanism that reduces the rotational speed of the rotor. The configuration of drive motors M1 to M4 is not limited to this.

[0013] Furthermore, the vehicle V according to this embodiment has a suspension system configuration that has anti-squat and anti-dive characteristics. The front suspension system employs a well-known trailing arm type suspension device equipped with a trailing arm TA, and the rear suspension system employs a well-known leading arm type suspension device equipped with a leading arm LA. The configuration of the suspension system of vehicle V is not limited to this.

[0014] Next, the configuration of the stack escape control system 1 will be described. Figure 2 is a block diagram showing the schematic configuration of the stack escape control system 1 according to this embodiment. As shown in Figure 2, the stack escape control system 1 includes a vehicle speed sensor 21, attitude angle sensor 22, wheel speed sensor 23, stack escape switch 3, stack escape ECU 4, and each drive motor M1 to M4.

[0015] The vehicle speed sensor 21 is a sensor that detects the movement speed of vehicle V. The information transmitted from the vehicle speed sensor 21 (vehicle V movement speed information) is used to determine whether or not the stuck vehicle V has escaped from being stuck. In other words, when vehicle V is stuck, even if the wheels (drive wheels) W1 and W2 rotate, the vehicle V itself does not move in proportion to the amount of rotation of the drive wheels W1 and W2. Therefore, when it is detected that a predetermined movement speed has been achieved by the stuck vehicle V, it can be determined that vehicle V has escaped from being stuck.

[0016] The attitude angle sensor 22 is a sensor that detects the attitude angle of the vehicle V (for example, the inclination angle of a straight line extending in the longitudinal direction of the vehicle with respect to the road surface). Alternatively, the attitude angle of the vehicle V may be detected by a well-known inertial navigation system. This attitude angle sensor 22 is used to detect the ground contact load of a stuck drive wheel W1. In other words, the ground contact load of the stuck drive wheel W1 differs depending on whether the drive wheel W1 is in contact with the bottom of a recess H in the road surface or is in contact with the area near the top of the recess H, as if going over the recess H. The ground contact load tends to be larger in the latter case than in the former case. Furthermore, the attitude angle of the vehicle V also differs depending on whether the stuck drive wheel W1 is in contact with the bottom of a recess H in the road surface or is in contact with the area near the top of the recess H. The attitude angle tends to be smaller in the latter case than in the former case. For example, if the front wheels are stuck, the vehicle V will tilt downwards toward the front, and if the rear wheels are stuck, the vehicle V will tilt downwards toward the rear. In both cases, the attitude angle is larger when the stuck drive wheels are in contact with the bottom of a depression in the road surface. As described above, in the case of a stuck vehicle V, there is a correlation between the ground contact load of the stuck drive wheels and the attitude angle of the vehicle V. In other words, the smaller the attitude angle of the vehicle V, the greater the ground contact load of the drive wheels tends to be. Utilizing this relationship, in this embodiment, the smaller the attitude angle of the vehicle V detected by the attitude angle sensor 22, the greater the ground contact load of the drive wheels is determined to be.

[0017] The wheel speed sensor 23 is a sensor that detects the rotational speed of each drive wheel W1 and W2. For example, well-known electromagnetic or optical sensors can be used.

[0018] The stack escape switch 3 is a switch that is pressed by an occupant to instruct the execution of control for stack escape (hereinafter referred to as stack escape control) when the vehicle V is stacked. That is, when this stack escape switch 3 is pressed, the process proceeds to stack escape control. Also, in this embodiment, the stacking of the vehicle V is automatically recognized and the process automatically proceeds to stack escape control. In the present invention, it is not necessarily required to have both the stack escape switch 3 and the automatic stack recognition function, and only one of them may be provided.

[0019] The stack escape ECU 4 includes, for example, a processor such as a CPU, a ROM that stores a control program, a RAM that temporarily stores data, and input / output ports. Then, as functional units realized by the stored computer program, the stack escape ECU 4 includes an information transmission / reception unit 41, a stack determination unit 42, a grip drive wheel control unit 43, a ground load estimation unit 44, and a stack drive wheel control unit 45.

[0020] The information transmission / reception unit 41 receives moving speed information from the vehicle body speed sensor 21, attitude angle information from the attitude angle sensor 22, and wheel speed information from the wheel speed sensor 23. Also, during the stack escape control described later, the information transmission / reception unit 41 transmits the driving force command information calculated by the grip drive wheel control unit 43 and the stack drive wheel control unit 45 to the drive motor selected from each drive motor (the left front drive motor M1 of the left front wheel, the right front drive motor M2 of the right front wheel, the left rear drive motor M3 of the left rear wheel, and the right rear drive motor M4 of the right rear wheel).

[0021] The stack detection unit 42 is a functional unit for automatically recognizing when a vehicle V is stuck. For example, it compares the rotational speed information of each drive wheel W1, W2 detected by the wheel speed sensor 23 (wheel speed information) with the vehicle's movement speed information detected by the vehicle speed sensor 21. It determines that the vehicle V is stuck if the rotational speed of any of the drive wheels W1, W2 is above a predetermined value, but the vehicle's movement speed is approximately zero. However, the method of stack detection is not limited to this. When the stack detection unit 42 determines that the vehicle V is stuck, it instructs the ground load estimation unit 44 to start the ground load estimation operation and transmits a command signal to start stack escape control to the grip drive wheel control unit 43 and the stack drive wheel control unit 45. Furthermore, if the stack escape switch 3 is pressed, the stack escape switch 3 instructs the ground load estimation unit 44 to start the ground load estimation operation and transmits a command signal to start stack escape control to the grip drive wheel control unit 43 and the stack drive wheel control unit 45.

[0022] The grip drive wheel control unit 43 is a functional unit that controls the driving force of the drive wheels W2 that are not stacked (not entering the depression H on the road). On the condition that it receives a stack escape control start command signal, it starts stack escape control and controls the driving force of this drive wheel (the drive wheel not entering the depression H on the road) W2. Specifically, a command signal is transmitted to the drive motor of this drive wheel W2 so as to periodically generate a driving force in the forward rotation direction and a driving force in the reverse rotation direction. As a result, the drive wheels W2 that are not stacked will periodically repeat forward rotation and reverse rotation. Then, due to the action of the anti-squat force and anti-dive force associated with the application of this driving force, the vehicle V will rock back and forth. FIGS. 1(a) and (b) show the state where the left front wheel W1 is stacked. In this case, the grip drive wheel control unit 43 transmits a command signal to the drive motors M2, M3, and M4 of the drive wheels other than the left front wheel W1 so as to alternately generate a driving force in the forward rotation direction (refer to arrow T1 in FIG. 1(a)) and a driving force in the reverse rotation direction (refer to arrow T2 in FIG. 1(b)). Incidentally, at this time, as the drive wheels that periodically repeat forward rotation and reverse rotation, it may be all of the drive wheels that are not stacked, or it may be some of the drive wheels that are not stacked.

[0023] Since the forward rotation of the drive wheel W2 is the rotation in the direction in which the vehicle V moves forward, the stacked drive wheel (left front wheel) W1 will move in the direction of escaping forward from the stack. FIG. 1(a) shows this state (stack first state), and the stacked left front wheel W1 is pressed against the front inclined surface (the left inclined surface in FIG. 1(a)) in the depression H so as to cross the depression H. That is, the ground load is in a state where it is relatively large.

[0024] On the other hand, the reverse rotation of the drive wheel W2 is a rotation in the direction that moves the vehicle V backward. Therefore, when the drive wheel W2 rotates in the reverse direction after the forward rotation described above, the stuck drive wheel W1 moves in a direction that causes it to become embedded in the stack. In this state, the ground contact load becomes relatively small. Furthermore, when the drive wheel W2 rotates in the reverse direction, the stuck drive wheel W1 is pressed against the rear inclined surface of the recess. Figure 1(b) shows this state (second stacking state).

[0025] Furthermore, it is preferable that the period for changing the direction of the driving force be the period during which resonance occurs in the vehicle V's posture (roll or pitch). This allows for a greater effect of shifting the ground load.

[0026] The grip drive wheel control unit 43 causes the non-stuck drive wheels W2 to repeatedly rotate in the forward and reverse directions periodically, which causes the ground contact load of the stuck drive wheels W2 to fluctuate. As mentioned above, in a stuck vehicle V, there is a correlation between the ground contact load of the stuck drive wheels W1 and the attitude angle of the vehicle V. In other words, the smaller the attitude angle of the vehicle V, the greater the ground contact load of the drive wheels W1 tends to be. The ground contact load estimation unit 44 estimates the ground contact load of the stuck drive wheels W1 by receiving attitude angle information from the attitude angle sensor 22. For example, the ROM stores a map (ground contact load estimation map) that defines the relationship between the attitude angle and the ground contact load of the drive wheels W1, and the ground contact load of the drive wheels W1 is estimated by fitting the attitude angle to this map. Alternatively, the ground contact load of the drive wheels W1 may be calculated using a predetermined calculation formula.

[0027] The stuck drive wheel control unit 45 is a functional unit that controls the driving force of a stuck drive wheel W1. Specifically, when the ground contact load of the drive wheel W1 estimated by the ground contact load estimation unit 44 increases to a preset escape load (synchronized with the timing when the ground contact load of the stuck drive wheel W1 increases), it sends a command signal to the drive motor M1 of the stuck drive wheel W1 to apply driving force to the stuck drive wheel W1. As a result, driving force is applied to the stuck drive wheel W1 while sufficient ground contact force is secured, so that the driving force can be transmitted to the road surface, making it possible to free the drive wheel W1 from being stuck.

[0028] Next, we will explain the stack escape control. Figure 3 is a flowchart of the stack escape control procedure. First, in step ST1, it is determined whether or not a stack has occurred. This operation is performed by the stack determination unit 42 described above. If no stack has occurred and the determination in step ST1 is NO, then the execution of stack escape control is not necessary, and the control is terminated.

[0029] If a stuck situation occurs and the result in step ST1 is YES, the process moves to step ST2, where the stuck drive wheel is identified and the stuck-out control is initiated. For example, attitude angle information from the attitude angle sensor 22 can be used to identify the stuck drive wheel. For example, as shown in Figure 1(a), if the left front wheel W1 is stuck, the vehicle V will be tilted downwards toward the left front, which allows identification of the stuck left front wheel W1.

[0030] In step ST3, the drive motors of the gripping drive wheels (drive wheels that are not stuck) are periodically subjected to both forward and reverse rotational driving forces. This operation is performed by the gripping drive wheel control unit 43 described above.

[0031] In this state, the process moves to step ST4, where it is determined whether the ground contact load of the stuck drive wheels has increased to a predetermined escape load L1. In other words, it is determined whether the ground contact load estimated by the ground contact load estimation unit 44 has increased to the escape load L1. This escape load is a value that has been predetermined by experiments or simulations. If the ground contact load of the stuck drive wheels has not increased to the escape load L1, and step ST4 determines NO, the process returns to step ST3, and the aforementioned operation (an operation that periodically generates a driving force in the forward rotation direction and a driving force in the reverse rotation direction) is repeated.

[0032] When the ground contact load of a stuck drive wheel increases to the escape load L1, and a YES determination is made in step ST4, a synchronized escape drive force is applied to the stuck drive wheel in synchronization with the timing when this ground contact load increases to the escape load L1. In other words, the synchronized escape drive force is applied at the timing when sufficient ground contact force is secured on the stuck drive wheel and the drive force of that drive wheel can be transmitted to the road surface. This operation is performed by the stuck drive wheel control unit 45 described above.

[0033] In step ST6, it is determined whether the vehicle has escaped the jam by applying synchronous driving force for escape. This determination is made based on the vehicle speed information from the vehicle speed sensor 21, as described above. If the vehicle has not yet escaped the jam and the determination in step ST6 is NO, the process returns to step ST3 and the above operations are repeated.

[0034] On the other hand, if the stack has been exited and a YES determination is made in step ST6, the stack exit control is terminated.

[0035] As explained above, in this embodiment, a periodic driving force is applied to the non-stuck drive wheels W2, and a driving force (synchronous driving force for escape) is applied to the stuck drive wheels W1 when the ground contact load on the stuck drive wheels W1 increases to a predetermined escape load. This makes efficient escape from being stuck possible by effectively utilizing the driving force of the non-stuck drive wheels W2 and optimizing the timing of applying driving force to the stuck drive wheels W1.

[0036] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments described above, and all modifications and applications are possible within the scope of the claims and equivalents thereof.

[0037] For example, although the above embodiment described the case where the left front wheel W1 gets stuck, the same method can be applied when other drive wheels get stuck. Furthermore, even if multiple drive wheels get stuck, the present invention can be applied as long as there are drive wheels that are not stuck.

[0038] Furthermore, in the above embodiment, the ground contact load of the stuck drive wheel was estimated based on the attitude angle of the vehicle V. The present invention is not limited to this, and the ground contact load may be estimated based on the difference in the suspension stroke amount of each drive wheel.

[0039] Furthermore, in the above embodiment, the vehicle was configured to automatically recognize when it had escaped from being stuck. The present invention is not limited to this, however, the vehicle may also be configured so that the crew recognizes when it has escaped from being stuck and performs an operation to terminate the stuck escape control (for example, by turning OFF the stuck escape switch 3). [Industrial applicability]

[0040] The present invention is applicable to a vehicle-mounted system for preventing vehicles from getting stuck, which is capable of applying independent driving force to each wheel. [Explanation of Symbols]

[0041] 1…Stack escape control system 22…Attitude and angle sensor 4…Stack escape ECU 43...Grip drive wheel control unit 44...Ground load estimation unit 45...Stack drive wheel control unit V...Vehicle W1, W2...Drive wheels M1~M4...Drive motors (means for applying driving force)

Claims

[Claim 1] A vehicle stuck in a stack escape control system for removing the vehicle from the stack, A driving force application means capable of individually applying driving force to each wheel, A grip drive wheel control unit that applies a predetermined driving force from the driving force application means to wheels that are not stuck, A ground load estimation unit that estimates the ground load on the stuck wheels, A stack escape control system characterized by comprising: a stack drive wheel control unit that applies driving force from the driving force application means to the stuck wheels, provided that the ground load estimation unit has increased the ground load to a predetermined escape load.

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