Vertical obstacle crossing control method and device based on vehicle posture adjustment and vehicle

Abstract

The invention relates to a vertical obstacle crossing control method and device based on vehicle posture adjustment and a vehicle, and belongs to the technical field of multi-axle wheeled vehicle motion control. In the crossing process, the vehicle posture is adjusted to be a trapezoid with the high front portion and the low rear portion by controlling the suspension system, loads are distributed and moved backwards, the torque requirement for crossing of the first shaft is reduced, then the angle theta of the vehicle in the obstacle crossing process is assisted to be increased through the single-shaft wheel lifting action, the limit torque needed by all shafts in the obstacle crossing process is reduced, and therefore the obstacle crossing capacity of the vehicle is improved. The invention is suitable for wheeled vehicles, manned vehicles and unmanned vehicles with three axles and more than three axles and with vehicle posture adjusting and independent wheel lifting functions. Compared with a wheeled vehicle without vehicle posture adjustment and wheel lifting actions, the torque requirement of the multi-axle wheeled vehicle for crossing the vertical obstacle is reduced, and the height of the multi-axle vehicle for crossing the vertical obstacle is increased under the driving motor with the same torque.

Description

Technical Field

[0001] The invention belongs to the technical field of multi-axle vehicle motion control, and in particular relates to a control method for a multi-axle vehicle to climb over a vertical obstacle. Background Art

[0002] The passing performance of a multi-axle vehicle is an important indicator of its off-road capability, and the height of the vertical obstacle it can climb over is a key parameter for evaluating the passing performance of a multi-axle vehicle. The control process for a multi-axle vehicle with a posture adjustment function to pass through a vertical obstacle is as follows: Figure 7 First, the vehicle is adjusted to the obstacle-crossing posture, and then the vehicle is driven close to the vertical obstacle. Subsequently, by increasing the driving torque, the vehicle is driven over the vertical obstacle axle by axle to complete the crossing. The crossing process is shown in Figure 1 As shown in the figure, under the same vertical obstacle and test conditions, the maximum height of the obstacle that a vehicle can climb over is positively correlated with the maximum driving torque of the vehicle.

[0003] Take the 8×8 vehicle’s third axle going over a vertical obstacle as an example. Ignoring tire deformation, the tire trajectory during the overtaking process is as follows: Figure 4 As shown in the figure, force analysis shows that to climb over a vertical obstacle, the driving force of the third axis needs to satisfy the following inequality:

[0004] F T >F g cosθ+F Z (1)

[0005] Among them, F T Indicates the current shaft driving force, F N Indicates the current shaft support force, F g Indicates the current axle load gravity, F Z Indicates the rolling resistance of the current axis, F Z =F g *f, f represents the rolling resistance coefficient, usually f=0.026, which is the same as F N and F g In comparison, F Z The value of is very small and can be ignored in the calculation analysis. Therefore, the driving force inequality of the overtaking process can be simplified to:

[0006] F T >F g cosθ (2)

[0007] In the interval [0°, 90°], cosθ is a monotonically decreasing function. Therefore, in F g and F Z Under the same conditions, the larger θ is, the smaller the driving force limit required for overturning is.

[0008] During the overtaking process, as the current axle is lifted, the current axle load and support force are actually gradually increasing. Figure 4 In the illustrated state, as the third axle clears the ground, the tires of the fourth axle gradually lift off, gradually transferring the axle load to the third axle. Once the fourth axle is completely off the ground, the axle load on the third axle reaches its maximum, reaching the point of maximum driving force required to clear the obstacle. At this point, the ability to clear the vertical obstacle depends on whether the driving force can exceed the axle load's weight component when the vehicle reaches its torque limit. Therefore, improving a vehicle's ability to clear vertical obstacles can be achieved by increasing driving torque, increasing tire radius, increasing the θ angle, and reducing axle load.

[0009] When ordinary multi-axle vehicles climb over vertical obstacles, the tire radius, θ angle, and axle load cannot be actively changed. Therefore, the climbing ability only depends on the vehicle's driving torque limit. Summary of the Invention

[0010] In response to the above problems, the present invention provides a method, device and vehicle for controlling vertical obstacle crossing based on vehicle posture adjustment.

[0011] On the one hand, the present application proposes a method for controlling a multi-axle vehicle to cross vertical obstacles based on vehicle posture adjustment, including adjusting the vehicle posture to be higher in the front and lower in the rear in the direction of travel, so that the load distribution moves backward; lifting the single-axle wheel from front to rear in sequence, and completely crossing the vertical obstacles one by one.

[0012] Further, the following steps are included:

[0013] Step 1: Control the suspension and raise all single-axle positions, decreasing the height in sequence, so that the vehicle body appears to be higher in the front and lower in the back;

[0014] Step 2: Drive the vehicle close to the vertical obstacle. When the i-th axis is about to touch the vertical obstacle, the vehicle stops moving forward.

[0015] Step 3: Control the i-th axle to lift the wheel; control the vehicle to continue moving forward, increasing the driving torque until the i-th axle completely passes the vertical obstacle;

[0016] Step 4: After the i-th axle has completely passed the vertical obstacle, the vehicle stops moving forward, the i-th axle wheel lifting action is released, and the i-th axle position is raised to a higher vehicle posture; return to step 2 until all single axles have passed the vertical obstacle.

[0017] Furthermore, the completely crossing over the vertical obstacle refers to the current axis center crossing the vertical plane of the vertical obstacle.

[0018] Furthermore, each time the wheel is lifted to the wheel lifting limit, the wheel lifting limit refers to the tire lifting height being equal to the maximum wheel lifting stroke allowed by the wheel lifting.

[0019] On the other hand, the present application proposes a multi-axle vehicle vertical obstacle crossing control device based on vehicle posture adjustment, including an obstacle crossing vehicle posture adjustment module and a climbing over wheel lifting control module; the obstacle crossing vehicle posture adjustment module is responsible for adjusting the vehicle posture before climbing over the vertical obstacle, and adjusting the vehicle posture to a trapezoidal state with high front and low rear; the climbing over wheel lifting control module is responsible for driving the vehicle forward during the climbing process, controlling each axle to perform a single-axis wheel lifting action in turn, and completing the climbing over the vertical obstacle.

[0020] On the other hand, the present application proposes a multi-axle vehicle capable of crossing vertical obstacles based on vehicle posture adjustment, including the control device described above, and a vehicle capable of crossing vertical obstacles by the control device.

[0021] Beneficial effects

[0022] (1) The trapezoidal vehicle posture constructed by the present invention transfers the axle load backward, reducing the load distribution on the first axle, thereby reducing the torque demand caused by the load weight that needs to be offset when the first axle goes over a vertical obstacle, thereby reducing the difficulty of the first axle going over a vertical obstacle.

[0023] (2) The present invention can assist a multi-axle vehicle in increasing the angle θ during obstacle crossing by lifting the wheel, thereby reducing the maximum torque demand point and effectively enhancing the ability of the multi-axle vehicle to cross vertical obstacles. Without increasing the driving capacity, the vehicle can cross higher vertical obstacles.

[0024] (3) The present invention is not limited by the type of vehicle. As long as a multi-axle vehicle has the functions of vehicle posture adjustment and independent single-axle wheel lifting, the present invention can be applied, and has good versatility.

[0025] (4) The control device of the present invention is simple, easy to install and modify on existing vehicles, and highly practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the process of a common multi-axle vehicle passing through a vertical obstacle, taking an 8×8 vehicle as an example;

[0027] Figure 2 Schematic diagram of the process of a multi-axle vehicle of the present invention passing a vertical obstacle, taking an 8×8 vehicle as an example, wherein (a) shows a trapezoidal vehicle posture adjustment, (b) shows one axle wheel lifting, (c) shows one axle climbing over a vertical obstacle, (d) shows each axle adjusted to the highest vehicle posture, (e) shows two axles wheel lifting, (f) shows two axles climbing over a vertical obstacle, (g) shows three axles wheel lifting, (h) shows three axles climbing over a vertical obstacle, (i) shows four axles wheel lifting, and (j) shows four axles climbing over a vertical obstacle, completing the obstacle traversal.

[0028] Figure 3 The diagram below shows the wheel lifting action, taking the first axis as an example;

[0029] Figure 4This is a schematic diagram of the original process of crossing a vertical obstacle without lifting the wheel, taking an 8×8 vehicle as an example;

[0030] Figure 5 This is a schematic diagram of the process of an 8×8 vehicle lifting its wheels to cross a vertical obstacle;

[0031] Figure 6 This is a schematic diagram of a single axis completely crossing a vertical obstacle;

[0032] Figure 7 Provides control strategies for common multi-axle vehicles to pass vertical obstacles;

[0033] Figure 8 This is a control strategy for a multi-axle vehicle passing through vertical obstacles according to the present invention.

[0034] in,

[0035] i——The axis number from front to back of the vehicle, indicating the i-th axis

[0036] n——number of vehicle axles

[0037] h——Current wheel lifting height

[0038] h t ——Lifting wheel limit height

[0039] h d ——The height of the chassis from the ground at a certain point

[0040] α——the distance between the front end of the vehicle and the vertical surface of the vertical obstacle

[0041] O——axis center

[0042] L——the distance from the center of the axis to the vertical plane of the vertical obstacle

[0043] θ——The angle between the line connecting the tire center and the tire ground contact point and the horizontal line

[0044] F T ——Current axis driving force

[0045] F N ——Current shaft support force

[0046] F Z ——Current axle driving resistance

[0047] F g ——Current axle load gravity DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0049] The control method of the present invention is as follows: Figure 8 As shown, taking an 8×8 vehicle (4-axle) with a wheel lifting limit ht of 0.4m and a center of gravity located at the center of the vehicle body as an example, the embodiment and control principle are as follows:

[0050] (1) Control the suspension and raise the first axle of the vehicle to the highest position, then the second axle, and so on until the last axle, so that the vehicle body presents a trapezoidal state with the front higher and the back lower, such as Figure 2 (a) Driving the vehicle close to a vertical obstacle;

[0051] (2) When the first axle is about to touch the vertical obstacle, that is, the distance between the front end of the vehicle's front wheel and the vertical plane of the vertical obstacle is less than 0.1 meters (empirical value), the vehicle stops moving forward and the first axle is lifted. When the lifting limit is reached, if Figure 2 (b) shows that the wheel lift height h is equal to 0.4m, the wheel lift is locked, and the vehicle is driven forward by increasing the driving torque until the first axle completely passes over the vertical obstacle;

[0052] (3) After the first axis has completely crossed the vertical obstacle, if Figure 2 As shown in (c), the vehicle stops moving forward, the wheel lifting action of the first axle is released, and all axles are raised to the highest vehicle posture, such as Figure 2 As shown in (d), the second axis is then lifted until the second axis reaches its limit. Figure 2 As shown in (e), i.e., the wheel lift height h is equal to 0.4 m, the vehicle is driven forward by increasing the driving torque until the second axle completely passes over the vertical obstacle;

[0053] (4) After the second axle has completely crossed the vertical obstacle, the vehicle stops moving forward, the second axle wheel lifting action is released, and the second axle is raised to the highest vehicle posture, such as Figure 2 As shown in (f), if i is not equal to 1 and i is not equal to 4, the third axis is lifted and the lifting limit of the third axis is reached. Figure 2 (g), i.e. the wheel lift height h is equal to 0.4 m, and the vehicle is driven forward until the third axle completely passes over the vertical obstacle;

[0054] (5) After the third axle has completely crossed the vertical obstacle, the vehicle stops moving forward, the third axle wheel lifting action is released, and the third axle is raised to the highest vehicle posture, such as Figure 2 As shown in (h), if i is not equal to 1 and i is not equal to 4, the 4th axis is lifted and the 4th axis reaches the lifting limit, as shown in Figure 2 (i) The wheel lift height h is equal to 0.4 m, and the vehicle is driven forward until the fourth axle completely passes over the vertical obstacle;

[0055] (6) After the 4th axle has completely crossed the vertical obstacle, the vehicle stops moving forward, the 4th axle wheel lifting action is released, and the 4th axle is raised to the highest vehicle posture. It is judged that i is not equal to 1, but i is equal to 4. All axles have completely crossed the vertical obstacle, and the vertical obstacle is completed. Figure 2 (j) shown.

[0056] The trapezoidal state with high front and low rear means that the first axle is in the highest position allowed by the vehicle, the nth axle is in the lowest position allowed by the vehicle, and the middle axle is in the middle position. The overall support moves the center of gravity of the vehicle backward, and the axle load distribution of the vehicle increases in turn, reducing the load distribution of the first axle, thereby reducing the torque demand of the first axle when rolling over.

[0057] About to contact a vertical obstacle means that the distance between the front end of the wheel and the vertical surface of the vertical obstacle is less than α meters. α is an artificially set empirical threshold that is related to the vehicle structure and the terrain environment factors where the obstacle is located. The value of α should be greater than or equal to 0.

[0058] Wheel lifting means lifting the tire of a specified axle by controlling the suspension system, such as Figure 3 As shown, taking the wheel lifting of the tire of the first axle as an example, it is pulled from the original position shown by the dotted circle to the final position; reaching the wheel lifting limit means that the tire lifting height h is equal to the maximum wheel lifting stroke ht meters allowed by the wheel lifting. ht is determined by the vehicle structure and suspension function design and is an inherent parameter of vehicles with wheel lifting function.

[0059] Completely crossing the vertical obstacle means that the current axis center O crosses the vertical extension line of the vertical obstacle, such as Figure 6 As shown, L is greater than 0.

[0060] The highest vehicle posture means that the vehicle chassis ground clearance reaches the maximum value by controlling the suspension system; the lowest vehicle posture means that the vehicle chassis ground clearance reaches the minimum value by controlling the suspension system. For a single axle, the highest vehicle posture means that the suspension system is controlled so that the height of the chassis directly below the current axle from the ground reaches the maximum value; for a single axle, the lowest vehicle posture means that the suspension system is controlled so that the height of the chassis directly below the current axle from the ground reaches the minimum value.

[0061] In this embodiment, the maximum passability can be achieved by adjusting the wheel lift and vehicle posture according to the maximum adjustment range. In practice, the adjustment may not be performed according to the maximum adjustment range, depending on the actual situation.

[0062] The present invention gives full play to the suspension control advantage of the multi-axle vehicle with vehicle posture adjustment and wheel lifting function, reduces the load distribution of the first axle by axle load transfer, thereby reducing the axle load resistance of the first axle turning over, and through the wheel lifting action, such as Figure 5As shown, the auxiliary vehicle increases the angle θ during the obstacle crossing process, reduces the resistance of the multi-axle vehicle to climbing over the vertical obstacle, and thus reduces the difficulty of climbing over. The present invention proposes a control method for multi-axle vehicles to cross vertical obstacles based on vehicle posture adjustment. The control method consists of an obstacle-crossing vehicle posture adjustment module and a climbing wheel-lifting control module. The obstacle-crossing vehicle posture adjustment module is responsible for performing vehicle posture initialization adjustment before climbing over the vertical obstacle, adjusting the vehicle posture to a trapezoidal state with high front and low back, reducing the axle load of the first axle, and thus reducing the climbing resistance of the first axle. The climbing wheel-lifting control module is responsible for driving the vehicle forward in the subsequent climbing process, controlling each axle to perform a single-axle wheel-lifting action in turn, increasing the angle θ during the obstacle crossing process, and assisting each axle to cross the maximum torque demand point, thereby completing the climbing of each axle over the vertical obstacle, and finally completing the climbing of the vertical obstacle by the entire vehicle.

[0063] The present invention also proposes a multi-axle vehicle capable of crossing vertical obstacles based on vehicle posture adjustment, comprising the control device and a vehicle capable of crossing vertical obstacles by the control device.

Claims

1. A vertical obstacle control method based on vehicle posture adjustment, characterized by: In the direction of travel, adjust the vehicle posture so that the front is higher and the back is lower, so that the load distribution moves backward; lift the single-axle wheel from front to back in sequence, and completely cross the vertical obstacles one by one.

2. The vertical obstacle control method based on vehicle posture adjustment according to claim 1, characterized in that: During the obstacle crossing process, the vehicle posture is always raised with the front higher and the back lower.

3. The vertical obstacle control method based on vehicle posture adjustment according to claim 1, characterized in that: The following steps are included: Step 1: Control the suspension and raise all single-axle positions, decreasing the height in sequence, so that the vehicle body appears to be higher in the front and lower in the back; Step 2: Drive the vehicle close to the vertical obstacle. When the i-th axis is about to touch the vertical obstacle, the vehicle stops moving forward. Step 3: Control the i-th axle to lift the wheel; control the vehicle to continue moving forward, increasing the driving torque until the i-th axle completely passes the vertical obstacle; Step 4: After the i-th axle completely passes over the vertical obstacle, the vehicle stops moving forward and the i-th axle wheel lifting action is released; then return to step 2 until all single axles pass over the vertical obstacles.

4. The vertical obstacle control method based on vehicle posture adjustment according to claim 1, characterized in that: The completely crossing over the vertical obstacle refers to the vertical plane where the current axis center crosses the vertical obstacle.

5. A vertical obstacle control method based on vehicle posture adjustment according to any one of claims 1 to 4, characterized in that: Each time the wheel is lifted, it is lifted to the wheel lifting limit, which means that the tire lifting height is equal to the maximum wheel lifting stroke allowed by the wheel.

6. A vertical obstacle control device based on vehicle posture adjustment, characterized by: It includes an obstacle-crossing vehicle posture adjustment module and a climbing wheel-lifting control module; the obstacle-crossing vehicle posture adjustment module is responsible for adjusting the vehicle posture before climbing over a vertical obstacle, adjusting the vehicle posture to a trapezoidal state with the front higher and the back lower; the climbing wheel-lifting control module is responsible for driving the vehicle forward during the climbing process, controlling each axle to perform a single-axis wheel-lifting action in sequence, and completing the climbing over the vertical obstacle.

7. A multi-axle vehicle capable of traversing vertical obstacles based on vehicle posture adjustment, characterized in that: The invention comprises the control device according to claim 5, and a vehicle capable of vertically crossing obstacles by the control device.

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