Steering control method and system for multi-axis lunar rover

Abstract

The invention discloses a multi-axis lunar rover steering control method and system. The method comprises the steps that the relation between a first axis steering angle and a second axis steering angle of a multi-axis lunar rover and the relation between all axis wheel steering angles of a double-track model and a single-track model are determined according to Ackerman steering geometry; establishing a mathematical model of a relationship between a first shaft steering angle and a third shaft steering angle of the multi-shaft lunar rover based on zero sideslip feedforward control, wherein the mathematical model comprises a relationship between the third shaft steering angle and a fourth shaft steering angle; optimizing the ratio of the fourth shaft steering angle to the third shaft steering angle, and determining each shaft steering angle according to a preset vehicle body state and the first shaft steering angle; and converting the steering angles of the shafts of the monorail model into the steering angles of the wheels on the two sides of the shafts of the double-rail model according to the wheel steering angle relation of the shafts of the double-rail model and the monorail model, so as to realize the steering of the multi-shaft lunar rover. According to the invention, the influence of lunar surface environment and tire side deviation can be well dealt with, and the overall maneuverability and safety of the lunar rover are improved.

Description

Technical Field

[0001] The present invention relates to the field of vehicle control technology, and in particular to a multi-axis lunar rover steering control method and system. Background Art

[0002] With the continuous advancement of my country's lunar exploration project, building a mobile laboratory on the moon has been put on the agenda. The mobile laboratory on the moon has a large load, so a multi-axis design is used to improve the load-bearing capacity, and it has the ability of all-wheel independent drive and independent steering. Such a multi-axis vehicle will face many challenges when driving on the moon. The rugged and soft terrain and low gravity environment on the moon place high demands on vehicle performance. One of the important research directions is the steering control of the lunar rover. Under the influence of terrain and low gravity, the lateral force that the lunar surface can provide to the lunar rover is relatively low, which makes the vehicle prone to lateral slip when turning. Therefore, advanced steering control methods are needed to improve the turning performance of the lunar rover and ensure the smooth progress of lunar research projects.

[0003] Traditional ground vehicles generally do not involve steering control, but use a steering mechanism that can approximate Ackerman steering geometry to achieve steering. Ackerman steering geometry was first proposed by a German carriage engineer in 1817. Its principle is to use geometric structures to control the different steering angles of the inner and outer wheels when the vehicle turns. In an ideal Ackerman steering, the vertical lines of the inner and outer wheel turning angles of each axle intersect at one point, that is, the center of the turning circle, which means that the inner wheel turning angle is greater than the outer wheel turning angle. At this time, the Ackerman steering ratio is 100%. When the vertical lines of the inner and outer wheel turning angles are parallel, it is called parallel steering, and the Ackerman steering ratio is 0%. At present, the steering of traditional ground vehicles is generally between parallel steering and Ackerman steering. This steering method can reduce wheel side slip and allow the vehicle to turn more smoothly. However, ideal Ackerman steering does not exist in reality. Especially when turning at high speed, the tires will produce a large side slip angle, which will cause the vehicle body to produce significant lateral slip. The theoretical Ackerman steering will have a large deviation from the actual steering effect. The understeer of the vehicle caused by tire slip will increase with the increase of vehicle speed, and the side slip of the vehicle body will reduce the handling stability of the vehicle. It is precisely because the Ackerman steering geometry does not take the tire's side slip characteristics into consideration that the actual heading of the tire during the steering process is different from the theoretical heading, and the desired steering effect cannot be achieved.

[0004] In order to achieve better steering effect and improve the overall performance of the lunar rover during turning, the wheel angle needs to be controlled. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a multi-axis lunar rover steering control method and system, which can better cope with the influence of the lunar surface environment and tire side deviation, and improve the overall handling performance and driving safety of the lunar rover.

[0006] To achieve the above purpose, the present invention adopts the following technical solution.

[0007] In some embodiments, a multi-axis lunar rover steering control method is provided, wherein the multi-axis lunar rover includes a first axis, a second axis, a third axis, and a fourth axis, each axis includes wheels on left and right sides, and the multi-axis lunar rover steering control method includes:

[0008] According to the Ackerman steering geometry, the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover, as well as the relationship between the wheel angles of each axle of the double-track model and the single-track model are determined; the relationship between the first-axis steering angle and the second-axis steering angle is based on the single-track model;

[0009] A mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover is established based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model;

[0010] The ratio of the fourth-axis steering angle to the third-axis steering angle is optimized, and the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are determined according to a preset vehicle body state and the first-axis steering angle; the first-axis steering angle, the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are steering angles of the respective axes based on a single-track model;

[0011] According to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model, the steering angles of each axle of the single-track model are converted into the wheel turning angles on both sides of each axle of the double-track model;

[0012] The corresponding wheels are controlled according to the wheel turning angles on both sides of each axle to achieve the steering of the multi-axle lunar rover.

[0013] In some embodiments, optimizing the ratio of the fourth axis steering angle to the third axis steering angle includes:

[0014] Taking the center-of-mass sideslip angle of the multi-axis lunar rover as the optimization target, the ratio of the fourth-axis steering angle to the third-axis steering angle is optimized according to the relationship between the third-axis steering angle and the fourth-axis steering angle, so as to minimize the center-of-mass sideslip angle.

[0015] In some embodiments, the relationship between the first-axis steering angle and the second-axis steering angle includes a ratio of the second-axis steering angle to the first-axis steering angle, and determining the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover according to the Ackermann steering geometry includes:

[0016] The relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover is determined as:

[0017]

[0018] The ratio of the second axis steering angle to the first axis steering angle is:

[0019]

[0020] Among them, L1 and L2 are the wheelbases of the center of mass of the first and second wheelbase multi-axis lunar rover, respectively, and δ1 and δ2 are the steering angles of the first and second axes, respectively.

[0021] In some embodiments, the relationship between the wheel angles of each axle of the double-track model and the single-track model is:

[0022]

[0023] Among them, δ iL is the left wheel turning angle of the i-th axis of the double-track model, δ iR is the right wheel turning angle of the i-th axis of the double-track model, δ i is the i-th axis steering angle of the single-track model, L i is the wheelbase of the mass center of the i-th wheelbase multi-axle lunar rover, W half Half wheelbase.

[0024] In some embodiments, the zero sideslip feedforward control is to eliminate the lateral slip of the center of mass of the multi-axis lunar rover by controlling the wheel angles of the third axis and the fourth axis.

[0025] In some embodiments, the relationship between the first axis steering angle and the third axis steering angle is:

[0026]

[0027] Among them, k 1,3 is the proportional coefficient representing the relationship between the steering angle of the first axis and the steering angle of the third axis, m is the mass of the vehicle, C1, C2, C3, C4 are the lateral stiffness of the first axis, the second axis, the third axis, and the fourth axis respectively, L1, L2, L3, L4 are the wheelbases of the center of mass of the first axis, the second axis, the third axis, and the fourth wheelbase multi-axis lunar rover respectively, U is the longitudinal speed of the vehicle body, λ is the proportional coefficient representing the relationship between the steering angle of the third axis and the steering angle of the fourth axis, δ4=λδ3.

[0028] In some embodiments, the multi-axis lunar rover steering control method further includes:

[0029] The wheel speed of each axle of the single-track model is calculated according to the Ackermann steering geometry, and then the wheel speed of both sides of each axle of the double-track model is calculated by using the relationship between the wheel angles of each axle of the double-track model and the single-track model, and the wheel speed relationship is obtained:

[0030] v1=v4

[0031] v2=v3

[0032]

[0033] where v i is the wheel speed of each axle of the single-track model; v iL 、v iR They are the wheel speeds on the left and right sides of each axle of the double-track model.

[0034] In some embodiments, a multi-axis lunar rover steering control system is further provided, wherein the multi-axis lunar rover comprises a first axis, a second axis, a third axis, and a fourth axis, each axis comprises wheels on left and right sides, and the multi-axis lunar rover steering control system comprises:

[0035] A first calculation unit is used to determine the relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover, and the relationship between the wheel angles of each axis of the double-track model and the single-track model according to the Ackermann steering geometry; the relationship between the first axis steering angle and the second axis steering angle is based on the single-track model;

[0036] A second calculation unit is used to establish a mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model;

[0037] an optimization unit, for optimizing a ratio of a fourth-axis steering angle to a third-axis steering angle;

[0038] A unit for determining the steering angles of each axis of the single-track model, used to determine the steering angles of the second axis, the third axis, and the fourth axis according to a preset vehicle body state and the steering angle of the first axis; the steering angles of the first axis, the second axis, the third axis, and the fourth axis are steering angles of each axis based on the single-track model;

[0039] A double-track model wheel turning angle determination unit, used for converting the steering angle of each axle of the single-track model into the wheel turning angles on both sides of each axle of the double-track model according to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model;

[0040] The control unit is used to control the corresponding wheels according to the wheel angles on both sides of each axle to achieve steering of the multi-axle lunar rover.

[0041] In some embodiments, an electronic device is also provided, the electronic device comprising:

[0042] processor;

[0043] A memory containing processor-executable instructions, wherein:

[0044] The processor reads instructions from the memory to implement the steps of any of the above methods.

[0045] In some embodiments, a computer-readable storage medium is also provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of any of the above methods are implemented.

[0046] In the embodiment of the present application, the front two axles of the lunar rover still use the traditional Ackerman steering geometry, but the rear two axles no longer use Ackerman steering. Instead, according to the motion information of the lunar rover, the wheel angles of the rear two axles are controlled to make the sideslip angle of the lunar rover's center of mass zero. Since the control target is only the sideslip angle of the center of mass, there is a random coupling relationship between the wheel angles of the third and fourth axles. In order to determine the turning angle of each tire at any time, the present invention proposes to use the sideslip angle of the center of mass of the vehicle body as an evaluation index to optimize the proportional relationship between the wheel angles of the third and fourth axles. The embodiment of the present application can fully consider the impact of tire side slip and the lunar surface environment on the driving of the lunar rover, so that the wheel steering angle can adapt to the turning conditions of different vehicle speeds. While ensuring that the vehicle body has as small a lateral deviation as possible, other indicators for evaluating the handling stability of the lunar rover are comprehensively considered to improve the comprehensive performance of the lunar rover in the actual turning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the overall process of the multi-axis lunar rover steering control method according to some embodiments of the present invention.

[0048] Figure 2 Schematic diagram of the Ackerman steering principle of a four-axis lunar rover single-track model in some embodiments of the present invention.

[0049] Figure 3 Schematic diagram of the Ackerman steering principle of a four-axis lunar rover dual-track model according to some embodiments of the present invention.

[0050] Figure 4 Schematic diagram of a two-degree-of-freedom monorail model of a four-axis lunar rover according to some embodiments of the present invention.

[0051] Figure 5 Schematic diagram of a multi-axis lunar rover steering control system according to some embodiments of the present invention.

[0052] Figure 6 Schematic diagram of electronic devices according to some embodiments of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0054] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The interpretation of such words should be made from the perspective of those skilled in the art. For example, "above...", "below..." should be understood as the positional relationship of the main structure or structure of a component, etc. in an initial state, which may break through the above positional relationship during movement. "...disposed on..." should be understood as the approximate connection relationship of the components, rather than necessarily being above.

[0055] In the present invention, unless otherwise clearly defined and specified, the terms "set", "install", "connect", "connect", "fix" and the like should be understood in a broad sense from the perspective of those skilled in the art. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0057] Figure 1 FIG. 1 is a flowchart of a multi-axis lunar rover steering control method according to an embodiment of the present invention. Figure 1 Some embodiments of the present application provide a steering control method for a multi-axis lunar rover. In some embodiments, the multi-axis lunar rover is a four-axis lunar rover, and the multi-axis lunar rover includes a first axis, a second axis, a third axis, and a fourth axis, and each axis includes wheels on left and right sides. The steering control method for the multi-axis lunar rover includes:

[0058] According to the Ackerman steering geometry, the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover, as well as the relationship between the wheel angles of each axle of the double-track model and the single-track model are determined; the relationship between the first-axis steering angle and the second-axis steering angle is based on the single-track model;

[0059] A mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover is established based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model;

[0060] The ratio of the fourth-axis steering angle to the third-axis steering angle is optimized, and the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are determined according to a preset vehicle body state and the first-axis steering angle; the first-axis steering angle, the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are steering angles of the respective axes based on a single-track model;

[0061] According to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model, the steering angles of each axle of the single-track model are converted into the wheel turning angles on both sides of each axle of the double-track model;

[0062] The corresponding wheels are controlled according to the wheel turning angles on both sides of each axle to achieve the steering of the multi-axle lunar rover.

[0063] The multi-axis lunar rover steering control method in the embodiment of the present application fully considers the influence of tire side deviation on the lunar rover's turning performance, adopts zero sideslip feedforward control to eliminate the lateral slip of the lunar rover's center of mass caused by tire side deviation, and optimizes the ratio of the wheel angles of the rear two axles, which not only improves the lunar rover's steering ability, but also enables the lunar rover to obtain better turning handling stability, thereby improving the lunar rover's performance, comfort and safety.

[0064] In some embodiments, the relationship between the first-axis steering angle and the second-axis steering angle includes a ratio of the second-axis steering angle to the first-axis steering angle, and determining the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover according to the Ackermann steering geometry includes:

[0065] The relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover is determined as:

[0066]

[0067] And, the ratio of the second axis steering angle to the first axis steering angle is:

[0068]

[0069] Among them, L1 and L2 are the wheelbases of the center of mass of the first and second wheelbase multi-axis lunar rover, respectively, and δ1 and δ2 are the steering angles of the first and second axes, respectively.

[0070] The present invention first uses Ackerman steering geometry to establish the steering relationship between the first two axes, so as to facilitate the subsequent vehicle dynamics analysis. The Ackerman steering principle diagram of the four-axis lunar rover single-track model can be referenced Figure 2 In the figure, O is the center of the turning circle; C is the center of mass of the multi-axis lunar rover, which is also the instantaneous rotation center of the lunar rover. According to the geometric relationship, the following equation can be obtained:

[0071] Single track model first axis steering angle:

[0072]

[0073] Single track model second axis steering angle:

[0074]

[0075] The relationship between the first and second axis steering angles of the single-track model:

[0076]

[0077] The ratio of the steering angle of the second axis to the first axis is:

[0078]

[0079] Among them, L1 and L2 are the first and second wheelbases of the lunar rover's center of mass; δ1 and δ2 are the first and second axis steering angles.

[0080] In some embodiments, the relationship between the wheel angles of each axle of the double-track model and the single-track model is:

[0081]

[0082] Among them, δ iL is the left wheel turning angle of the i-th axis of the double-track model, δ iR is the right wheel turning angle of the i-th axis of the double-track model, δ i is the i-th axis steering angle of the single-track model, L i is the wheelbase of the mass center of the i-th wheelbase multi-axle lunar rover, W half It is understandable that i can be 1, 2, 3, 4, corresponding to the first axis, the second axis, the third axis, and the fourth axis, respectively.

[0083] Since the left and right wheel turning angles of the actual lunar rover are not equal, the wheel turning angle relationship between the single-track model and the double-track model is further derived in the embodiment of the present application for subsequent actual control. Figure 3 As shown. It can be understood that Figure 3Take the steering shown in as an example, which is a left turn, the center of the steering circle is the left point O, and each axle has left and right wheels (in the steering, they are the inner wheel and the outer wheel, respectively, the wheel close to the O point is the inner wheel, and the wheel far from the O point is the outer wheel). Figure 3 The left wheel shown is the inside wheel and the right wheel is the outside wheel.

[0084] The wheel turning angles on the left and right sides of the first axle are:

[0085]

[0086] then,

[0087]

[0088] Similar to available,

[0089]

[0090] where δ iL is the left wheel turning angle of the i-th axis of the double-track model, δ iR is the right wheel turning angle of the i-th axis of the double-track model; δ i is the steering angle of the i-th axis of the single-track model; L i is the wheelbase of the i-th axis; W half It is understandable that i can be 1, 2, 3, 4, corresponding to the first axis, the second axis, the third axis, and the fourth axis, respectively.

[0091] In some embodiments, the relationship between the first axis steering angle and the third axis steering angle is:

[0092]

[0093] Among them, k 1,3 is the proportional coefficient representing the relationship between the first axis steering angle and the third axis steering angle, that is, the ratio of the third axis steering angle to the first axis steering angle, m is the vehicle mass, C1, C2, C3, C4 are the cornering stiffness of the first axis, the second axis, the third axis, and the fourth axis respectively, L1, L2, L3, L4 are the wheelbases of the first axis, the second axis, the third axis, and the fourth axis respectively, U is the longitudinal speed of the vehicle body, λ is the proportional coefficient representing the relationship between the third axis steering angle and the fourth axis steering angle, that is, the ratio of the fourth axis steering angle to the third axis steering angle, δ4=λδ3. In some embodiments, the zero sideslip feedforward control is to eliminate the lateral slip of the center of mass of the multi-axis lunar rover by controlling the wheel angles of the third and fourth axes.

[0094] The two-degree-of-freedom monorail model of the four-axis lunar rover is as follows Figure 4 As shown. The tire lateral force F Yi (i=1,2,3,4) direction is positive, side slip angle α iC(i=1,2,3,4) is negative; the steering angle of the front two axes δ iC (i=1,2) is positive, the steering angle of the rear two axes δ iC (i=3,4) is negative; the vehicle body yaw angular velocity w is positive. This embodiment only considers the lateral degree of freedom and yaw degree of freedom of the vehicle body, the preset vehicle body state is that the longitudinal velocity of the vehicle body remains unchanged, and other degrees of freedom are not considered.

[0095] The two-degree-of-freedom dynamic equation of this model is:

[0096]

[0097] Where m is the vehicle mass; I zz is the yaw moment of inertia; U and V are the longitudinal and lateral velocities of the vehicle body; w is the yaw angular velocity of the vehicle body; is the lateral acceleration of the vehicle body; is the vehicle body yaw angular acceleration; C1, C2, C3, C4 are the cornering stiffness of each axle, specifically the sum of the cornering stiffness of the left and right wheels. The tire cornering stiffness can be calculated using ground mechanics based on the lunar terrain; λ is the ratio of the fourth-axis steering angle to the third-axis steering angle, δ4=λδ3.

[0098] The following calculation formula is known for the vehicle body center of mass side slip angle:

[0099]

[0100] Where β is the side slip angle of the vehicle body center of mass; is the vehicle body's center of mass sideslip angular velocity.

[0101] So the dynamic equation can be rearranged as:

[0102]

[0103] In steady state, the vehicle body's center of mass sideslip angle and yaw rate no longer change, that is, So there is

[0104]

[0105] According to the above formula, the calculation formula of the vehicle body center of mass side slip angle is:

[0106]

[0107] Let β = 0, and the relationship between the steering angles of the third axis and the first axis is:

[0108]

[0109] In some embodiments, the multi-axis lunar rover steering control method further includes:

[0110] The wheel speed of each axle of the single-track model is calculated according to the Ackermann steering geometry, and then the wheel speed of both sides of each axle of the double-track model is calculated by using the relationship between the wheel angles of each axle of the double-track model and the single-track model, and the wheel speed relationship is obtained:

[0111] v1=v4

[0112] v2=v3

[0113]

[0114] where v i is the wheel speed of each axle of the single-track model; v iL 、v iR They are the wheel speeds on the left and right sides of each axle of the double-track model. It can be understood that the wheel speed is the rotation speed of the wheel moving forward.

[0115] For a four-axle lunar rover with eight independent wheels, in addition to the turning angle, the wheel speed will also affect the turning performance of the lunar rover. In the embodiment of the present application, the wheel speed of each axle of the single-track model is calculated using the Ackerman steering geometry, and then the wheel speed of both sides of each axle of the double-track model is calculated using the relationship between the wheel turning angles of each axle of the double-track model and the single-track model, so that the lunar rover has better turning performance.

[0116] In some embodiments, optimizing the ratio of the fourth axis steering angle to the third axis steering angle includes:

[0117] Taking the center-of-mass sideslip angle of the multi-axis lunar rover as the optimization target, the ratio of the fourth-axis steering angle to the third-axis steering angle is optimized according to the relationship between the third-axis steering angle and the fourth-axis steering angle, so as to minimize the center-of-mass sideslip angle.

[0118] The zero sideslip control of the four-axis lunar rover in the embodiment of the present application is based on the single-track model. Since the left and right wheel turning angles of the actual lunar rover are different when turning, and there is a certain error in the relationship between the turning angle and speed of the single-track model and the double-track model under zero sideslip control using Ackerman steering geometry, it is impossible to make the center of mass slip angle 0 during actual control, and it can only reduce the lateral slip of the center of mass of the lunar rover. In the embodiment of the present application, the steering angle ratio of the third and fourth axes of the single-track model is optimized to determine the steering angles of the remaining axes under a certain vehicle body state and the first axis steering angle input.

[0119] When the vehicle body and tire information are determined, the proportional coefficient k between the first axis steering angle and the third axis steering angle is obtained. 1,3It is only related to the longitudinal speed U of the multi-axis lunar rover and the ratio λ of the steering angles of the third and fourth axes. When the longitudinal speed U of the lunar rover is constant and λ is selected to different values, different steering angles of the third and fourth axes will be obtained, which can reduce the sideslip of the center of mass of the lunar rover to a certain extent. This embodiment optimizes the ratio of the steering angles of the third and fourth axes with the goal of minimizing the sideslip angle of the center of mass. In some embodiments, taking the steady-state rotation condition as an example, at a certain rotation speed, different λ values ​​are set, and the sideslip angles of the center of mass of the multi-axis lunar rover are measured respectively, and the λ corresponding to the one with the smallest root mean square value of the sideslip angle of the center of mass is selected as the optimal λ at that speed.

[0120] Finally, the relationship between the wheel angles of each axle of the single-track model and the double-track model is used to obtain the steering angle of each wheel of the four-axis lunar rover, which is used for the steering control of the lunar rover. Simulation tests can also be carried out under different working conditions to analyze the steering performance of the lunar rover.

[0121] refer to Figure 5 In some embodiments, a multi-axis lunar rover steering control system is further provided, wherein the multi-axis lunar rover comprises a first axis, a second axis, a third axis, and a fourth axis, each axis comprises wheels on left and right sides, and the multi-axis lunar rover steering control system comprises:

[0122] A first calculation unit is used to determine the relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover, and the relationship between the wheel angles of each axis of the double-track model and the single-track model according to the Ackermann steering geometry; the relationship between the first axis steering angle and the second axis steering angle is based on the single-track model;

[0123] A second calculation unit is used to establish a mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model;

[0124] an optimization unit, for optimizing a ratio of a fourth-axis steering angle to a third-axis steering angle;

[0125] A unit for determining the steering angles of each axis of the single-track model, used to determine the steering angles of the second axis, the third axis, and the fourth axis according to a preset vehicle body state and the steering angle of the first axis; the steering angles of the first axis, the second axis, the third axis, and the fourth axis are steering angles of each axis based on the single-track model;

[0126] A double-track model wheel turning angle determination unit, used for converting the steering angle of each axle of the single-track model into the wheel turning angles on both sides of each axle of the double-track model according to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model;

[0127] The control unit is used to control the corresponding wheels according to the wheel angles on both sides of each axle to achieve steering of the multi-axle lunar rover.

[0128] The multi-axis lunar rover steering control system provided by the embodiment of the present invention can implement the various processes in the method embodiment described in the above embodiment, and can be applied to the electronic equipment described below. To avoid repetition, its effects will not be described here.

[0129] In some embodiments, an electronic device is also provided, such as Figure 6 As shown, the electronic device includes: a processor 10; a memory 20 storing instructions executable by the processor, wherein: the processor reads instructions from the memory to implement the steps of the multi-axis lunar rover steering control method as described in any of the above items, and can achieve the same technical effect. To avoid repetition, it will not be repeated here.

[0130] In some embodiments, the electronic device may include but is not limited to a smart phone, a tablet computer, a wearable device, a personal computer (PC), a netbook, a personal digital assistant (PDA), a smart watch, a vehicle-mounted device, a robot, a desktop computer, etc.

[0131] Some embodiments further provide a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed in a computer, the computer is caused to execute the multi-axis lunar rover steering control method described in each of the above method embodiments.

[0132] Some embodiments also provide a computer-readable storage medium on which data of each unit and model of the multi-axis lunar rover steering control system are stored.

[0133] The computer-readable storage medium may be a memory, which may be used to store software programs and various data. The memory may mainly include a program storage area and a data storage area, wherein the program storage area may store the above-mentioned computer program. The data storage area may store data of the above-mentioned multi-axis lunar rover steering control model, etc. In addition, the memory may include a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk storage device, a flash memory device, or other volatile solid-state storage devices.

[0134] In some embodiments, the computer-readable storage medium of the present application may include one or more databases, such as a key-value database, a MySQL database, etc. The present application does not elaborate on the categories of each database and its data storage method. Among them, one or more databases in some embodiments of the present application may be integrated with the electronic device, or may exist as an independent server or cloud storage, which may be determined according to the system structure and application requirements of the application platform to which it is applied.

[0135] The processor is the control center of the electronic device. It uses various interfaces and lines to connect the various parts of the entire electronic device. It executes various functions of the electronic device and processes data by running or executing software programs and / or models stored in the memory, and calling data stored in the memory, thereby controlling the electronic device as a whole. The processor may include one or more processing units; preferably, the processor may integrate an application processor and a modem processor, wherein the application processor mainly processes the operating system, user interface, and application programs, and the modem processor mainly processes wireless communications. It is understandable that the above-mentioned modem processor may not be integrated into the processor.

[0136] In some embodiments, a computer program product is also provided, including a computer program, which, when executed by a processor, implements the steps of the multi-axis lunar rover steering control method as described in any of the above embodiments.

[0137] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-axis lunar rover steering control method, characterized in that: The multi-axis lunar rover comprises a first axis, a second axis, a third axis, and a fourth axis, each axis comprises wheels on left and right sides, and the multi-axis lunar rover steering control method comprises: According to the Ackerman steering geometry, the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover, as well as the relationship between the wheel angles of each axle of the double-track model and the single-track model are determined; the relationship between the first-axis steering angle and the second-axis steering angle is based on the single-track model; A mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover is established based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model; The ratio of the fourth-axis steering angle to the third-axis steering angle is optimized, and the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are determined according to a preset vehicle body state and the first-axis steering angle; the first-axis steering angle, the second-axis steering angle, the third-axis steering angle, and the fourth-axis steering angle are steering angles of the respective axes based on a single-track model; According to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model, the steering angles of each axle of the single-track model are converted into the wheel turning angles on both sides of each axle of the double-track model; The corresponding wheels are controlled according to the wheel turning angles on both sides of each axle to achieve the steering of the multi-axle lunar rover.

2. The multi-axis lunar rover steering control method according to claim 1, characterized in that: The optimizing the ratio of the fourth axis steering angle to the third axis steering angle includes: Taking the center-of-mass sideslip angle of the multi-axis lunar rover as the optimization target, the ratio of the fourth-axis steering angle to the third-axis steering angle is optimized according to the relationship between the third-axis steering angle and the fourth-axis steering angle, so as to minimize the center-of-mass sideslip angle.

3. The multi-axis lunar rover steering control method according to claim 2, characterized in that: The relationship between the first-axis steering angle and the second-axis steering angle includes a ratio of the second-axis steering angle to the first-axis steering angle. Determining the relationship between the first-axis steering angle and the second-axis steering angle of the multi-axis lunar rover according to the Ackerman steering geometry includes: The relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover is determined as: And, the ratio of the second axis steering angle to the first axis steering angle is: Among them, L1 and L2 are the wheelbases of the center of mass of the first and second wheelbase multi-axis lunar rover, respectively, and δ1 and δ2 are the steering angles of the first and second axes, respectively.

4. The multi-axis lunar rover steering control method according to claim 3, characterized in that: The relationship between the wheel angles of each axle of the double-track model and the single-track model is: Among them, δ iL is the left wheel turning angle of the i-th axis of the double-track model, δ iR is the right wheel turning angle of the i-th axis of the double-track model, δ i is the i-th axis steering angle of the single-track model, L i is the wheelbase of the mass center of the i-th wheelbase multi-axle lunar rover, W half Half wheelbase.

5. The multi-axis lunar rover steering control method according to claim 4, characterized in that: The zero sideslip feedforward control is to eliminate the lateral slip of the center of mass of the multi-axis lunar rover by controlling the wheel angles of the third axis and the fourth axis.

6. The multi-axis lunar rover steering control method according to claim 5, characterized in that: The relationship between the first axis steering angle and the third axis steering angle is: Among them, k 1,3 is the proportional coefficient representing the relationship between the steering angle of the first axis and the steering angle of the third axis, that is, the ratio of the steering angle of the third axis to the steering angle of the first axis, m is the mass of the vehicle, C1, C2, C3, C4 are the lateral stiffness of the first axis, the second axis, the third axis, and the fourth axis respectively, L1, L2, L3, L4 are the wheelbases of the center of mass of the first axis, the second axis, the third axis, and the fourth wheelbase multi-axis lunar rover respectively, U is the longitudinal speed of the vehicle body, λ is the proportional coefficient representing the relationship between the steering angle of the third axis and the steering angle of the fourth axis, that is, the ratio of the steering angle of the fourth axis to the steering angle of the third axis, δ4=λδ3.

7. The multi-axis lunar rover steering control method according to claim 6, characterized in that: The multi-axis lunar rover steering control method further comprises: The wheel speed of each axle of the single-track model is calculated according to the Ackermann steering geometry, and then the wheel speed of both sides of each axle of the double-track model is calculated by using the relationship between the wheel angles of each axle of the double-track model and the single-track model, and the wheel speed relationship is obtained: v1=v4 v2=v3 where v i is the wheel speed of each axle of the single-track model; v iL 、v iR They are the wheel speeds on the left and right sides of each axle of the double-track model.

8. A multi-axis lunar rover steering control system, characterized in that: The multi-axis lunar rover comprises a first axis, a second axis, a third axis, and a fourth axis, each axis comprises wheels on left and right sides, and the multi-axis lunar rover steering control system comprises: A first calculation unit is used to determine the relationship between the first axis steering angle and the second axis steering angle of the multi-axis lunar rover, and the relationship between the wheel angles of each axis of the double-track model and the single-track model according to the Ackermann steering geometry; the relationship between the first axis steering angle and the second axis steering angle is based on the single-track model; A second calculation unit is used to establish a mathematical model of the relationship between the first axis steering angle and the third axis steering angle of the multi-axis lunar rover based on zero sideslip feedforward control, wherein the mathematical model includes the relationship between the third axis steering angle and the fourth axis steering angle; the relationship between the first axis steering angle and the third axis steering angle is based on a single track model; An optimization unit, used for optimizing the ratio of the fourth axis steering angle to the third axis steering angle; A unit for determining the steering angles of each axis of the single-track model, used to determine the steering angles of the second axis, the third axis, and the fourth axis according to a preset vehicle body state and the steering angle of the first axis; the steering angles of the first axis, the second axis, the third axis, and the fourth axis are steering angles of each axis based on the single-track model; A double-track model wheel turning angle determination unit, used for converting the steering angle of each axle of the single-track model into the wheel turning angles on both sides of each axle of the double-track model according to the relationship between the wheel turning angles of each axle of the double-track model and the single-track model; The control unit is used to control the corresponding wheels according to the wheel angles on both sides of each axle to achieve steering of the multi-axle lunar rover.

9. An electronic device, characterized in that: The electronic device comprises: processor; A memory containing processor-executable instructions, wherein: The processor reads instructions from the memory to implement the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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