Four-wheel independent drive full-rotation profiling chassis and pose stability control method

Abstract

The application provides a four-wheel independent driving full-rotation profiling chassis and a pose stability control method, which comprises a chassis frame, four steering and walking components, four profiling adjusting components, an inertial measurement unit and a control system; the control system controls the walking and full-rotation steering movement of the chassis, and actively controls the pose of the chassis frame based on the measurement data of the inertial measurement unit through the profiling adjusting components. The steering and walking components of the chassis adopt an independent differential wheel train structure with two inputs and two outputs, and can realize multiple walking and steering movement modes; the series active suspension system can realize ground profiling and pose stability control. Based on the vertical dynamics model of the chassis degrees of freedom, a linear quadratic regulator is designed, the feedback information of the inertial measurement unit and the displacement sensor is fused, active adjustment of the suspension is realized, and the stability of the chassis in complex terrain is improved.

Description

Technical Field

[0001] This invention belongs to the field of agricultural machinery chassis technology, specifically relating to a four-wheel independent drive full-rotation contour chassis and a method for position and posture stability control. Background Technology

[0002] The chassis is a core component of mobile agricultural machinery, and its overall performance directly affects the machine's operating efficiency, reliability, and stability. When facing complex operating environments, such as slopes, high ridges and narrow ditches, and hilly mountainous areas with unstructured terrain, higher demands are placed on the chassis's mobility, stability, and steering flexibility. In high-precision operations such as autonomous navigation and farmland inspection on uneven and rugged terrain, the chassis also requires shock absorption and posture control performance, as these directly affect operational safety and data reliability, preventing image distortion, path tracking deviations, and even rollovers caused by ground tilt. Currently, four-wheel independent steering chassis mainly use two drive methods for the drive wheels: hub / wheel-side motors and hydraulic motors. Their advantages include compact structure, flexible layout, and high transmission efficiency. However, both require power cables or hydraulic lines to be directly connected to the drive wheel components. When the drive wheels rotate, the power cables or hydraulic lines can become entangled with the drive wheel frame, causing the drive wheels to rotate only within a certain angle range, and 360° full rotation is not yet possible. Existing four-wheel independent steering chassis primarily employ passive suspension mechanisms. While some research reports on active air suspension adjustment mechanisms exist, they are constrained by damper travel. When the chassis travels on uneven terrain, the vertical wheel bounce is significant, potentially exceeding the damper's travel range. This prevents the damper from functioning effectively and hinders stable and reliable ground contouring. Therefore, this paper proposes a mechanical four-wheel independent full-rotation chassis structure. Its four drive wheels are unconstrained by the structure, enabling wireless full-rotation. A tandem active and passive suspension system is designed for active contouring attitude control, and a control method is proposed. The aim is to improve the chassis's driving stability in unstructured agricultural terrain. The designed chassis system has broad application prospects in inspection and transportation operations in hilly and mountainous areas and complex fields, providing a reference for the development of intelligent agricultural equipment. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a four-wheel independent drive full-rotation contour-following chassis and its posture stability control method. The chassis's steering and travel components employ a two-input, two-output independent differential wheel train structure, enabling various travel and steering motion modes. Its series active suspension system achieves ground contour-following and posture stability control. Based on the chassis's 11-DOF vertical dynamics model, this invention designs a linear quadratic regulator (LQR), integrating feedback information from the inertial measurement unit (IMU) and displacement sensors to achieve active adjustment of the suspension, thereby improving the chassis's stability in complex terrain.

[0004] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0005] A four-wheel independent drive full-rotation contour-following chassis includes:

[0006] Chassis frame;

[0007] Four steering and traveling components are mounted symmetrically in a rectangle at the four ends of the chassis frame, with the chassis geometric center as the center of symmetry.

[0008] Each of the steering and traveling components includes:

[0009] Upper rack,

[0010] The lower rack can rotate 360° relative to the upper rack around its vertical axis.

[0011] Wheels, mounted on the lower frame, and

[0012] The drive unit is used to independently drive the rotation of the wheels and the full rotation of the lower frame;

[0013] Four contouring adjustment components, each of which is connected to the upper frame of one of the steering and traveling components and the chassis frame, are used to actively adjust the vertical position of the steering and traveling component relative to the chassis frame.

[0014] An inertial measurement unit, fixedly mounted on the chassis frame, is used to measure the pitch angle θ and roll angle φ of the chassis frame; and

[0015] The control system is electrically connected to the drive units of the four steering and walking components and the four contour adjustment components. It is used to control the walking and full-turn steering movements of the chassis, and based on the measurement data of the inertial measurement unit, to perform active stability control on the position and posture of the chassis frame through the contour adjustment components.

[0016] In the above scheme, the steering and traveling component is vertically and slidably connected to the chassis frame through a guide mechanism;

[0017] The guiding mechanism includes a guide shaft support mounted on the chassis frame and a guide shaft sleeve mounted on the steering and traveling component, as well as a guide shaft that is slidably fitted between the guide shaft support and the guide shaft sleeve.

[0018] The drive unit includes a servo motor one and a servo motor two mounted on the upper frame of the steering and walking component. The servo motor one drives the wheel to rotate, and the servo motor two drives the lower frame to rotate in a full rotation.

[0019] The contouring adjustment component includes a slide base mounted on the upper frame, a lead screw rotatably mounted on the slide base, a slider cooperating with the lead screw, a servo motor driving the lead screw, and a spring damper connected between the slider and the chassis frame. It also includes a displacement sensor for measuring the displacement of the slider.

[0020] In the above scheme, the steering and traveling component is a two-degree-of-freedom differential gear train structure, and its input is the rotational speed of servo motor one. and the speed of servo motor 2 The output is the rotational speed of the wheel around the axis of the wheel bearing housing. and the steering speed about the vertical axis of the steering travel component And satisfy:

[0021]

[0022] in, This represents the transmission ratio between the driving gear and the driven gear. This represents the transmission ratio of the right-angle bevel gearbox.

[0023] In the above scheme, the control system includes an intelligent controller and a programmable controller;

[0024] The intelligent controller integrates a motion mode control model, which is used to calculate the desired linear velocity and desired turning angle of the four wheels based on the received motion mode signal and motion parameter signal, and drive the corresponding servo motor one and servo motor two through the programmable controller to realize various motion modes such as differential motion, Ackerman motion, crab motion, four-wheel steering and stationary turning.

[0025] Furthermore, the intelligent controller also integrates a pose stability control model, which is used to determine the pitch angle measured by the inertial measurement unit. and roll angle The displacement sensor measures the slider displacement, calculates the road surface excitation, and performs active stability control on the chassis frame's pose based on the road surface excitation.

[0026] The above solution also includes an encoder, which is coaxially arranged with the rotation axis of the steering and traveling component, and is used to measure the rotation angle value of the wheel in real time.

[0027] A method for position and posture stability control of the four-wheel independent drive full-rotation contoured chassis includes the following steps: Step S1: The control system acquires the chassis frame pitch angle measured by the inertial measurement unit in real time. and roll angle Step S2: Establish a dynamic model of the chassis's pose stability and transform the state-space equation of the 11-DOF continuous system. The state-space equation uses the slider displacement as the control input and the pitch and roll angles as the controlled outputs. Step S3: Based on the linear quadratic regulator (LQR) algorithm, construct an optimal LQR controller with the target performance index J, which includes state error and control energy consumption, as the objective function. Step S4: Solve the Riccati equation to obtain the state feedback gain matrix K, and calculate the optimal control law that minimizes the performance index J, outputting the target displacement of the four sliders. Step S5: Drive the servo motor three to make the four sliders reach the target displacement, realizing active stabilization control of the chassis frame's pitch and roll angles.

[0028] In the above scheme, the target performance index J is defined as:

[0029]

[0030] In the formula, , , , These represent the corresponding displacements of the four sliders. This represents the average displacement of the four sliders. As a performance indicator, it is adjusted to maintain a constant ground clearance of the chassis. , , , , These are the state weighting coefficients for pitch angle, pitch rate, roll angle, roll rate, and average displacement of the slide, respectively. , , , These are the control weight coefficients for the outputs of the four slides.

[0031] Furthermore, the state-space equation is:

[0032] Among them, state variables , Represents a column vector of 22*1 dimensions;

[0033] Input variables , Represents a 4x1 dimension column vector;

[0034] Output vector , Represents a column vector of 3*1 dimensions;

[0035] perturbation vector , Represents a 4x1 dimension column vector;

[0036] ,

[0037] State matrix A is derived from a 22-dimensional state vector x, where, Indicates the speed at the center of gravity of the chassis; This indicates the displacement and velocity at the chassis center of gravity; This indicates the pitch rate of the chassis; Indicates the chassis pitch angle; This indicates the roll rate of the chassis; Indicates the chassis roll angle; This indicates the vertical speed of the left front wheel of the chassis; This indicates the vertical speed of the right front wheel of the chassis; This indicates the vertical speed of the left rear wheel of the chassis; This indicates the vertical speed of the right rear wheel of the chassis; This indicates the vertical displacement of the left front wheel of the chassis; This indicates the vertical displacement of the right front wheel of the chassis; This indicates the vertical displacement of the left rear wheel of the chassis; This indicates the vertical displacement of the right rear wheel of the chassis; This indicates the speed of the left front wheel slider; This indicates the speed of the right front wheel slider; This indicates the speed of the left rear wheel slider; This indicates the speed of the right rear wheel slider; This indicates the displacement of the left front wheel slider; This indicates the displacement of the right front wheel slider; This indicates the displacement of the left rear wheel slider; This indicates the displacement of the right rear wheel slider;

[0038] Similarly, the input matrix B is derived from the 4-dimensional input vector u, where, This indicates the displacement of the slider in the left front wheel tandem active suspension system. This indicates the displacement of the slider in the right front wheel tandem active suspension system. This indicates the displacement of the slider in the left rear wheel tandem active suspension system. This indicates the displacement of the slider in the right rear wheel tandem active suspension system;

[0039] The output matrix C is listed based on the 3D output vector y, where, Indicates pitch angle, Indicates the roll angle. This represents the average displacement of the four sliders.

[0040] Furthermore, the road surface excitation input Calculated using the following formula:

[0041]

[0042]

[0043]

[0044]

[0045] in, This indicates the road's effect on the left front wheel; This indicates the road's stimulus to the right front wheel; This indicates the road's effect on the left rear wheel; This indicates the excitation of the road surface onto the right rear wheel; Indicates the distance between the front axle and the geometric center of the chassis; This indicates the distance between the rear axle and the geometric center of the chassis. Indicates the front wheel track width; Indicates the rear wheel track width; This represents the vehicle pitch angle measured by the IMU; This represents the vehicle body roll angle measured by the IMU; This represents the value measured by the displacement sensor for the left front wheel tandem active suspension system. This represents the value measured by the displacement sensor for the right front wheel tandem active suspension system. This represents the value of the left rear wheel tandem active suspension system measured by the displacement sensor; This represents the value of the right rear wheel tandem active suspension system measured by the displacement sensor.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] This invention employs a two-degree-of-freedom differential wheel train structure for the steering and travel components, independently driven by servo motor one and servo motor two. This decouples wheel rotation from steering, avoiding cable entanglement and enabling 360° full rotation of the wheels. Based on this, a four-wheel independently driven, full-rotation contour-following chassis is designed. Each steering and travel component is connected to the chassis frame via a series active suspension system. This system includes a contour-following adjustment component, an inertial measurement unit, a displacement sensor, and servo motor three. The spring damping of the contour-following adjustment component passively absorbs road impacts, while servo motor three actively adjusts the slider position based on feedback signals from the inertial measurement unit and displacement sensor. Based on the chassis's 11-degree-of-freedom vertical dynamics model, a linear quadratic regulator (LQR) is used to actively control the slider position, achieving active vibration reduction and ground contouring of the chassis frame. This effectively improves the stability and passability of the chassis in complex terrain. Attached Figure Description

[0048] Figure 1 This is an overall structure and assembly drawing of the chassis according to one embodiment of the present invention;

[0049] Figure 2 This is an overall structure and assembly drawing of a steering and walking component according to an embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the chassis motion transmission principle according to one embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram illustrating the chassis motion principle according to an embodiment of the present invention, wherein, Figure 4 (a) is a schematic diagram of differential motion. Figure 4 (b) is a diagram of Ackermann's motion principle. Figure 4 (c) is a diagram of the four-wheel steering principle. Figure 4 (d) is a diagram illustrating the principle of crab-like movement. Figure 4 (e) is a schematic diagram of the principle of turning in place;

[0052] Figure 5 This is a dynamic model of the chassis posture stability according to one embodiment of the present invention;

[0053] Figure 6 This is a schematic diagram of the chassis LQR pose stability control principle according to one embodiment of the present invention;

[0054] Figure 7 This is a schematic diagram of the chassis motion and posture stability measurement and control system according to one embodiment of the present invention.

[0055] Figure 8 This is an example of chassis motion and posture stability control under road surface excitation by a single-sided trapezoidal boss according to an embodiment of the present invention, wherein... Figure 8 (a) is a curve showing the pitch angle variation under the excitation of a single-sided trapezoidal protrusion road surface. Figure 8 (b) is a curve showing the change in side tilt angle under the excitation of a single-sided trapezoidal protrusion pavement. Figure 8 (c) is the slider displacement curve under the road surface excitation of a single-sided trapezoidal boss;

[0056] Figure 9 This is an example result of chassis motion and posture stability control under unilateral sinusoidal undulating road surface excitation according to an embodiment of the present invention, wherein, Figure 9 (a) is a curve showing the pitch angle variation under unilateral sinusoidal undulating road surface excitation. Figure 9 (b) is a curve showing the change in roll angle under unilateral sinusoidal undulating road surface excitation. Figure 9 (c) is the slider displacement curve under unilateral sinusoidal undulating road surface excitation;

[0057] Figure 10This is an example of chassis motion and posture stability control under the excitation of a sinusoidal undulating road surface with opposite phases on both sides, according to an embodiment of the present invention. Figure 10 (a) is a curve showing the pitch angle variation under the excitation of sinusoidal undulating road surfaces with different phases on both sides. Figure 10 (b) is a curve showing the change in roll angle under the excitation of sinusoidal undulating road surfaces with different phases on both sides. Figure 10 (c) is a slider displacement curve under the excitation of the sinusoidal undulating road surface with different phases on both sides.

[0058] In the diagram: 1. Steering and traveling component; 2. Guide bushing; 3. Guide bushing mounting plate; 4. Guide shaft; 5. Guide shaft support; 6. Support mounting plate; 7. Inertial measurement unit; 8. Chassis frame; 9. Wheel axle; 10. Sprocket 1; 11. Chain; 12. Sprocket 2; 13. Pressure sensor; 14. Slider; 15. Slide base; 16. Wheel; 17. Support arm; 18. Drive gear; 19. Driven gear; 20. Frame 2; 21. U-shaped bearing housing; 22. Beveled flange bearing housing; 23. Linkage. 24. Shaft 1, 25. Coupling 2, 26. Spring damper, 27. Lead screw, 28. Displacement sensor, 29. Servo motor 3, 30. Servo motor 1, 31. Servo motor 2, 32. Encoder, 33. Steering power transmission shaft, 34. Circular flange sleeve, 35. Flange bearing support, 36. Thrust bearing housing, 37. Frame 1, 38. Right angle bevel gearbox, 39. Wheel bearing housing, 40. Intelligent controller, 41. Motion control remote controller, 42. Programmable controller, 43. HIM human-machine interface. Detailed Implementation

[0059] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0060] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "front," "rear," "left," "right," "upper," "lower," "axial," "radial," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0061] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0062] Figure 1 The figure shown is a preferred embodiment of the four-wheel independent drive full-rotation contouring chassis of the present invention. The four-wheel independent drive full-rotation contouring chassis includes a chassis frame 8, four steering and walking components 1, four contouring adjustment components, an inertial measurement unit 7, and a control system.

[0063] Four steering and traveling components 1 are installed in a rectangular symmetrical manner at the four ends of the chassis frame 8 with the chassis geometric center as the center of symmetry;

[0064] Each of the steering and traveling components 1 includes: an upper frame 20, a lower frame 36, wheels 16, and a drive unit; the lower frame 36 is capable of 360° full rotation relative to the upper frame 20 about a vertical axis; the wheels 16 are mounted on the lower frame 36; the drive unit is used to independently drive the rotation of the wheels 16 and the full rotation of the lower frame 36;

[0065] Each of the contouring adjustment components is connected to the upper frame 20 of one of the steering and walking components 1 and the chassis frame 8, for actively adjusting the vertical position of the steering and walking component 1 relative to the chassis frame 8;

[0066] An inertial measurement unit 7 is fixedly installed on the chassis frame 8 and is used to measure the pitch angle θ and roll angle φ of the chassis frame 8.

[0067] The control system is electrically connected to the drive units of the four steering and walking components 1 and the four contour adjustment components, respectively, to control the walking and full-turn steering movements of the chassis, and to perform active stability control of the position and posture of the chassis frame 8 through the contour adjustment components based on the measurement data of the inertial measurement unit 7.

[0068] Four identical sets of steering and traveling components 1 are symmetrically mounted in a rectangular shape at the four ends of the chassis frame 8. The specific installation method is as follows:

[0069] In one specific embodiment of the present invention, four support mounting plates 6 are symmetrically fixedly mounted on the chassis frame 8 in a rectangular plane, ensuring that the four support mounting plates 6 are on the same plane. Three guide shaft supports 5 are symmetrically fixedly mounted on each support mounting plate 6. Three guide shaft sleeves 2 are fixedly mounted on the guide shaft sleeve mounting plate 3 of each steering and traveling component 1, and the number and distribution of the guide shaft sleeves 2 should be consistent with the guide shaft supports 5. The top end of the guide shaft 4 is fixedly mounted to the guide shaft support 5, and the guide shaft 4 passes through the guide shaft sleeve 2. The three guide shafts 4 can slide freely and synchronously within the corresponding three guide shaft sleeves 2, thus achieving vertical sliding between each steering and traveling component 1 and the chassis frame 8. The four identical sets of steering and traveling components 1 are connected to the chassis frame 8 in the same way, and each set of steering and traveling components 1 can achieve independent vertical sliding.

[0070] The inertial measurement unit 7 is fixedly installed on the center of the chassis frame 8 and is used to measure the chassis's pitch angle θ and roll angle φ.

[0071] The steering and traveling component 1 is vertically and slidably connected to the chassis frame 8 via a guide mechanism. The guide mechanism includes a guide shaft support 5 installed on the chassis frame 8 and a guide shaft sleeve 2 installed on the steering and traveling component 1, as well as a guide shaft 4 slidably engaged between the guide shaft support 5 and the guide shaft sleeve 2. The drive unit includes a servo motor 29 and a servo motor 30 installed on the upper frame 20 of the steering and traveling component 1. The servo motor 29 drives the wheel 16 to rotate, and the servo motor 30 drives the lower frame 36 to rotate at full 360 degrees. The contour adjustment component includes a slide base 15 installed on the upper frame 20, a lead screw 26 rotatably installed on the slide base 15, a slider 14 cooperating with the lead screw 26, a servo motor 28 driving the lead screw 26, and a spring damper 25 connected between the slider 14 and the chassis frame 8. It also includes a displacement sensor 27 for measuring the displacement of the slider 14.

[0072] Please refer to the structure and assembly method of the steering and walking components. Figure 2 :

[0073] In one specific embodiment of the present invention, the steering and traveling component 1 generally presents a double-layer structure. The guide bushing mounting plate 3 is fixedly connected to the cuboid frame 20, forming the upper layer mechanism, and the cuboid frame 36 is the lower layer mechanism. A servo motor 29 is fixedly mounted on the guide bushing mounting plate 3, and the center of the output shaft of the servo motor 29 is aligned with the axis of the steering and traveling component 1. A right-angle bevel gearbox 37 is fixedly mounted on the lower base plate of the cuboid frame 36, keeping the vertical input shaft aligned with the axis of the steering and traveling component 1. The output shaft of the servo motor 29 is fixedly connected to the vertical input shaft of the right-angle bevel gearbox 37 via a rigid coupling 23 to achieve power transmission. A servo motor 30 is fixedly mounted on the guide bushing mounting plate 3, and the center of the output shaft of the servo motor 30 is parallel to the axis of the steering and traveling component 1. The output shaft of the servo motor 30 is fixedly connected to the top end of the steering power transmission shaft 32 via a rigid coupling 24. The steering power transmission shaft 32 passes through the flange bearing support 34 and transmits power to the drive gear 18. The flange bearing support 34 is fixedly installed on the base plate of the cuboid frame 20 to improve the installation stability of the drive gear 18. The circular flange sleeve 33 passes through the lower base plate of the frame 20 and is fixed to the frame 20 via the thrust bearing seat 35. The driven gear 19 is fixedly connected to the circular flange sleeve 33 by bolts, and the lower end of the circular flange sleeve 33 is fixedly connected to the frame 1 36 to maintain synchronous rotation. The drive gear 18 meshes with the driven gear 19 to transmit power, thereby driving the rotation of the circular flange sleeve 33 and the frame 1 36. The support arms 17 are welded and fixed to both sides of the frame 1 36. The mounting plate of the U-shaped bearing seat 21 is fixed to the frame 20, and the chamfered flange bearing seat 22 is fixedly connected to the U-shaped bearing seat 21 by bolts to increase the stability of the circular flange sleeve 33.

[0074] It also includes an encoder 31, which is coaxially arranged with the rotation axis of the steering and traveling component 1. Specifically, the encoder 31 passes through the circular flange sleeve 33 to measure the rotation angle value of the steering and traveling component 1 in real time.

[0075] The output end of the right-angle bevel gearbox 37 is fixed to sprocket two 12, which is engaged with sprocket one 10 via chain 11. Sprocket one 10 is fixedly connected to wheel axle 9, which is fixed to support arm 17 via wheel bearing seat 38. When sprocket one 10 rotates, it drives wheel axle 9 to rotate, thereby enabling wheel 16 to move forward or backward.

[0076] A set of contour adjustment components is fixedly connected to the side of the cuboid frame 20 of the steering and walking component 1. The contour adjustment components mainly include a slide base 15, a lead screw 26, a slider 14, and a servo motor 28. The specific structure is as follows:

[0077] The slide base 15 is vertically fixed to the side of the cuboid frame 20. The lead screw 26 is installed on the center line of the slide base 15, and after installation, the lead screw 26 is kept parallel to the axis of the steering and traveling component 1. The lead screw 26 and the slider 14 are engaged by threaded transmission. Driven by the servo motor 28, the slider 14 moves linearly along the lead screw 26.

[0078] The bottom end of the pressure sensor 13 is fixedly mounted on the slider 14, and the top end of the pressure sensor 13 is fixedly connected in series with the bottom end of the spring damper 25. It is used to measure the pressure of the slider 14 and provide data support for wheel contact status monitoring, load analysis and subsequent research.

[0079] The top of the spring damper 25 is fixedly installed on the chassis frame 8, and after installation, the axis of the spring damper 25 is kept parallel to the axis of the steering and traveling component 1.

[0080] The displacement sensor 27 is fixedly installed on the slide base 15, and the measuring end is fixedly connected to the slider 14 for measuring the position of the slider 14.

[0081] For the transmission principle of the steering and traveling components, please refer to [link / reference needed]. Figure 3 :

[0082] Driven by servo motor 29 and servo motor 30, wheel 16 can achieve two degrees of freedom of rotation around the axis of steering and walking component 1 and the axis of wheel bearing seat 38.

[0083] The steering and traveling component 1 is a two-degree-of-freedom differential wheel system structure, that is, the two inputs are the rotational speeds of servo motor 29 and servo motor 30, respectively, and the outputs are the rotational speed of wheel 16 around the axis of wheel bearing seat 38 and the steering speed around the axis of steering and traveling component 1.

[0084] Assuming n1 and n2 are the rotational speeds of servo motor 30 and servo motor 29, respectively, the rotational speed of wheel 16 around the axis of wheel bearing housing 38 can be calculated. and the steering speed about the vertical axis of the steering travel component 1 They are respectively

[0085]

[0086] In the formula, i1 is the transmission ratio between the driving gear 18 and the driven gear 19, and i2 is the transmission ratio of the right bevel gearbox 37.

[0087] Steering and walking component 1 active and passive contouring process:

[0088] The steering and traveling component 1 is fixedly connected to the chassis frame 8 via a series connection of a slide base 15, a slider 14, a pressure sensor 13, and a spring damper 25.

[0089] When at rest, the spring damper 25 compresses under the gravity of the chassis frame 8, producing a fixed static deflection.

[0090] During chassis operation, it will be affected by ground undulations. If the slider 14 remains in the same position on the slide base 15, the ground undulations will cause the spring damper 25 to deform, thereby affecting the pitch angle θ and roll angle θ of the chassis frame 8. When a change occurs, it becomes passive ground contouring. Upon detecting ground undulations, servo motor 28 drives slider 14 to move linearly along lead screw 26, actively adjusting the position of slider 14 on the slide base 15 to reduce the pitch angle of the chassis frame 8. Left and right horizontal roll angles The area affected by the change is the active ground contouring. During this process, pressure sensor 13 collects real-time force data on the slider to monitor the ground contact pressure of each wheel and the operating status of the suspension system.

[0091] The control system includes an intelligent controller 39 and a programmable controller 41;

[0092] The intelligent controller 39 integrates a motion mode control model, which is used to calculate the desired linear velocity and desired turning angle of the four wheels 16 based on the received motion mode signal and motion parameter signal, and drive the corresponding servo motor 29 and servo motor 30 through the programmable controller 41 to realize various motion modes such as differential motion, Ackerman motion, crab motion, four-wheel steering and stationary turning.

[0093] The intelligent controller 39 also integrates a pose stability control model, which is used to determine the pitch angle θ and roll angle measured by the inertial measurement unit 7. The displacement sensor 27 measures the slider displacement, calculates the road surface excitation, and performs active stability control on the position and orientation of the chassis frame 8 based on the road surface excitation.

[0094] Please refer to the chassis motion mode and control principle. Figure 4 :

[0095] By coordinating the rotation speed of the four wheels 16 and steering speed Differential motion can be achieved ( Figure 4 (a) Ackermann Movement ( Figure 4 (b) Crab-like movement ( Figure 4 (c) Four-wheel steering Figure 4 (d) and turning in place ( Figure 4 (e) and five other different movement patterns.

[0096] A unified instantaneous center of gravity is crucial for ensuring consistent four-wheel motion and preventing tire slippage and wear, and it is also the foundation of chassis motion control. Assume the left and right wheelbases are... The front and rear track width is Parameters that characterize the motion state of the chassis , , For control input, the linear velocity of the four wheels is 16. , , , and rotation angle , , , To control the output.

[0097] Define the global coordinate system as Local coordinate system The control equations for the five motion modes are as follows:

[0098] (1) Differential motion:

[0099]

[0100]

[0101]

[0102]

[0103] (2) Ackermann Movement:

[0104]

[0105]

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] (3) Crab-like movement:

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119] (4) Four-wheel steering:

[0120]

[0121]

[0122]

[0123] (5) Turning in place:

[0124]

[0125]

[0126]

[0127]

[0128]

[0129] A method for attitude stability control of a four-wheel independent drive full-rotation contoured chassis includes the following steps: Step S1: The control system acquires the pitch angle θ and roll angle φ of the chassis frame 8 measured by the inertial measurement unit 7 in real time, and the displacement of the four sliders 14 measured by the displacement sensor 27; Step S2: Establish the attitude stability dynamic model of the chassis, and transform the state space equation of the 11-DOF continuous system, wherein the state space equation takes the slider displacement as the control input and the pitch angle and roll angle as the controlled output; Step S3: Based on the linear quadratic regulator (LQR) algorithm, construct an optimal LQR controller with the target performance index J, which includes state error and control energy consumption, as the objective function; Step S4: Solve the Riccati equation to obtain the state feedback gain matrix K, and calculate the optimal control law that minimizes the performance index J, and output the target displacement of the four sliders 14; Step S5: Drive the servo motor 28 to make the four sliders 14 reach the target displacement, thereby realizing active stability control of the pitch angle and roll angle of the chassis frame 8.

[0130] like Figure 5 and Figure 6 As shown, chassis posture stability control is achieved by adjusting the displacement of four sliders 14. To control the object, use the pitch angle yaw angle The average displacement of the four sliders 14 The control objective is to approach 0. The specific method is as follows:

[0131] Based on the dynamic model of chassis posture stability, the state-space equations of the 11-DOF continuous system are established:

[0132]

[0133] Among them, state variables R 22 This represents a 22*1 dimension column vector, including the vertical displacement and velocity of the chassis center of mass, pitch angle and angular velocity, roll angle and angular velocity, vertical displacement and velocity of the four wheels, and displacement and velocity of the four sliders.

[0134] Input variables , This represents a 4x1 column vector, which represents the displacement of the four sliders;

[0135] Output vector , This represents a 3*1 dimension column vector, consisting of pitch angle, roll angle, and average slider displacement;

[0136] perturbation vector , This represents a 4*1 dimensional column vector, which is the road surface excitation at the four wheels;

[0137] ,

[0138] State matrix A is derived from a 22-dimensional state vector x, where, Indicates the speed at the center of gravity of the chassis; This indicates the displacement and velocity at the chassis center of gravity; This indicates the pitch rate of the chassis; Indicates the chassis pitch angle; This indicates the roll rate of the chassis; Indicates the chassis roll angle; This indicates the vertical speed of the left front wheel of the chassis; This indicates the vertical speed of the right front wheel of the chassis; This indicates the vertical speed of the left rear wheel of the chassis; This indicates the vertical speed of the right rear wheel of the chassis; This indicates the vertical displacement of the left front wheel of the chassis; This indicates the vertical displacement of the right front wheel of the chassis; This indicates the vertical displacement of the left rear wheel of the chassis; This indicates the vertical displacement of the right rear wheel of the chassis; This indicates the speed of the left front wheel slider; This indicates the speed of the right front wheel slider; This indicates the speed of the left rear wheel slider; This indicates the speed of the right rear wheel slider; This indicates the displacement of the left front wheel slider; This indicates the displacement of the right front wheel slider; This indicates the displacement of the left rear wheel slider; This indicates the displacement of the right rear wheel slider;

[0139] Similarly, the input matrix B is derived from the 4-dimensional input vector u, where, This indicates the displacement of the slider in the left front wheel tandem active suspension system. This indicates the displacement of the slider in the right front wheel tandem active suspension system. This indicates the displacement of the slider in the left rear wheel tandem active suspension system. This indicates the displacement of the slider in the right rear wheel tandem active suspension system;

[0140] The output matrix C is listed based on the 3D output vector y, where, Indicates pitch angle, Indicates the roll angle. This represents the average displacement of the four sliders.

[0141] These three parameters are state observations of the system and can be selected according to the system being designed.

[0142] The road surface excitation input Calculated using the following formula:

[0143]

[0144]

[0145]

[0146]

[0147] in, This indicates the road's effect on the left front wheel; This indicates the road's stimulus to the right front wheel; This indicates the road's effect on the left rear wheel; This indicates the excitation of the road surface onto the right rear wheel; Indicates the distance between the front axle and the geometric center of the chassis; This indicates the distance between the rear axle and the geometric center of the chassis. Indicates the front wheel track width; Indicates the rear wheel track width; This represents the vehicle pitch angle measured by the IMU; This represents the vehicle body roll angle measured by the IMU; This represents the value measured by the displacement sensor for the left front wheel tandem active suspension system. This represents the value measured by the displacement sensor for the right front wheel tandem active suspension system. This represents the value of the left rear wheel tandem active suspension system measured by the displacement sensor; This represents the value of the right rear wheel tandem active suspension system measured by the displacement sensor.

[0148] The control method is as follows:

[0149] The optimal control method based on LQR (Linear Quadratic Regulator) state feedback obtains the optimal control law by minimizing a quadratic cost function that includes state error and control cost. A state matrix A describing chassis pose changes, an input matrix B reflecting the dynamic response of the lead screw and slide, and an output matrix C describing the output vector are established. By adjusting the ratio of the state weight matrix Q to the control weight matrix R, the convergence speed of the state and the energy consumption constraints of the control input are flexibly balanced. Based on the system state-space output equation, the target performance index J of the LQR controller design is defined as:

[0150]

[0151] In the formula, , , , These represent the corresponding displacements of the four sliders (14). This represents the average displacement of the four sliders (14). As a performance indicator, it is adjusted to maintain a constant ground clearance of the chassis. , , , , These are the state weighting coefficients for pitch angle, pitch rate, roll angle, roll rate, and average displacement of the slide, respectively. , , , These are the control weight coefficients for the outputs of the four slides.

[0152] The optimal weight coefficient matrix was obtained by repeatedly adjusting the matrix. , , , , , The effect is better at that time.

[0153] The optimal control rate is obtained by solving for the minimum value of the objective function. Controlling the displacement of the four sliders 14 accordingly, so that the pitch angle yaw angle and average displacement of the slide It approaches a value of 0.

[0154] Please refer to the principle and process of chassis motion and posture stability measurement and control system. Figure 7 :

[0155] The measurement and control system is based on the intelligent controller 39, which integrates the chassis's motion mode control model and posture stability control model.

[0156] The chassis movement is controlled by a motion control remote controller 40. The motion control remote controller 40 outputs chassis movement mode signals and chassis movement parameter signals, including center velocity v and rotational angular velocity n. r .

[0157] The motion control remote controller 40 outputs a signal to the intelligent controller 39, which calculates the linear velocity of the four wheels 16 based on the motion mode control model. , , , and rotation angle , , , The result is sent to the programmable controller 41, which directly drives the four sets of servo motors 29 and 30 to rotate, thereby changing the rotation speed of the four wheels 16. Steering speed This enables the chassis to move.

[0158] While the chassis is moving, the intelligent controller 39 collects the output signals from the pressure sensor 13, displacement sensor 27, and inertial measurement unit 7 in real time. The data from the displacement sensor 27 and inertial measurement unit 7 are used to calculate the posture stability control model, while the data from the pressure sensor 13 is used to monitor the ground contact pressure of each steering and walking component 1, providing a basis for system status monitoring and subsequent analysis.

[0159] The intelligent controller 39 calculates the desired displacement of the four sets of sliders 14 based on the pose stability control model and outputs the result to the programmable controller 41.

[0160] The programmable controller 41 directly drives four sets of servo motors 28 to rotate, thereby driving four sets of sliders 14 to reach the corresponding displacement state and increasing the pitch angle of the frame 8. yaw angle Stability.

[0161] The chassis motion and positional stability control process is displayed in real time through the HIM human-machine interface 42.

[0162] The experiment used 0.35×1.00×0.05 m rubber-plastic herringbone speed bumps to construct three types of test terrain excitations: a single-sided trapezoidal raised surface, a single-sided undulating surface, and a double-sided undulating surface with different phases. The speed bumps on the undulating surface were spaced 0.03 m apart. The sampling frequency was 2 Hz. The vehicle speed was 0.5 m / s.

[0163] Please refer to the example results of chassis motion and posture stability control. Figure 8-10 :

[0164] Set weighting coefficients: , , , , , .

[0165] The chassis passes over a single-sided trapezoidal raised road surface. Figure 8 ), single-sided sinusoidal undulating road surface ( Figure 9 ), and the road surface with different phases and sinusoidal undulations on both sides ( Figure 10 Taking the pitch angle of rack 8 as an example... yaw angle The root mean square value of the changes is used as the evaluation index, and the chassis attitude stability is controlled through LQR. Based on road surface excitation, the sliders are controlled to move in the opposite direction to ensure that the displacement, pitch angle, and roll angle at the chassis center of gravity are all zero. This is compared with passive attitude stability control (where four sets of sliders 14 remain in constant position), specifically the pitch angle... yaw angle The reduction in the root mean square value of the changes all exceeded 68%, fully demonstrating the effectiveness and superiority of the proposed pose stability control.

[0166] Specifically, Figure 8 (a) is a curve showing the pitch angle variation under the excitation of a single-sided trapezoidal protrusion road surface. Figure 8 (b) is a curve showing the change in side tilt angle under the excitation of a single-sided trapezoidal protrusion pavement. Figure 8 (c) is the slider displacement curve under the road surface excitation of a single-sided trapezoidal boss; Figure 9 (a) is a curve showing the pitch angle variation under unilateral sinusoidal undulating road surface excitation. Figure 9 (b) is a curve showing the change in roll angle under unilateral sinusoidal undulating road surface excitation. Figure 9 (c) is the slider displacement curve under unilateral sinusoidal undulating road surface excitation; Figure 10(a) is a curve showing the pitch angle variation under the excitation of sinusoidal undulating road surfaces with different phases on both sides. Figure 10 (b) is a curve showing the change in roll angle under the excitation of sinusoidal undulating road surfaces with different phases on both sides. Figure 10 (c) is the slider displacement curve under the excitation of sinusoidal undulating road surface with different phases on both sides. The root mean square values ​​of the experimental data of the passive contouring control and the LQR active contouring control of the chassis are summarized in Table 1 under the three designed test terrain conditions.

[0167] Table 1 Comparison of experimental results for contour-following attitude control

[0168]

[0169] The test results show that, compared to the passive suspension system, the proposed LQR contour-following attitude control strategy exhibits superior control performance under various complex terrains. Under conditions of a single-sided trapezoidal boss, single-sided undulations, and undulations with opposite phases on both sides, the root mean square (RMS) values ​​of the vehicle's pitch and roll angles significantly decreased. Specifically, the maximum reduction in the RMS value of the pitch angle reached 88.89%, and the maximum reduction in the roll angle reached 86.96%, with the attitude angle fluctuation reduction remaining above 69% under all test conditions. Furthermore, from... Figure 8 , Figure 9 , Figure 10 It can be seen that the sliding stage control input displacement under the three terrain conditions is within ±40 mm, which is less than the design range. The test verifies the effectiveness of the designed active control strategy in improving the contour-following performance and driving stability of the agricultural chassis.

[0170] The steering and traveling component 1 of the chassis of this invention adopts a two-input, two-output independent differential wheel system structure, independently driven by servo motor 29 and servo motor 30, realizing continuous movement and 360° infinite steering of the wheels 16, avoiding the steering constraints caused by hydraulic pipes or cables; through coordinated control of each servo motor, it can realize multiple motion modes such as Ackerman steering, four-wheel steering, crab steering, and stationary steering. Each steering and traveling component 1 is equipped with an independent series active suspension system, which consists of a slide base 15, a lead screw 26, a slider 14, and a spring damper 25 connected in series, and is equipped with a displacement sensor 27 and a pressure sensor 13 for real-time measurement of the position and force state of the slider 14. An inertial measurement unit 7 is fixedly installed on the chassis frame 8 to acquire the attitude information of the chassis frame 8. Based on the 11-DOF dynamic model of the chassis frame 8, a linear quadratic regulator LQR position controller was designed to realize the active adjustment of the position of slider 14, thereby effectively improving the steering flexibility and driving stability of the chassis under complex working conditions such as uneven roads or hilly terrain.

[0171] It should be understood that although this specification describes various embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other implementation methods that can be understood by those skilled in the art. The series of detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and they are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A four-wheel independent drive full-rotation contour-following chassis, characterized in that, include: Chassis frame (8); Four steering and walking components (1) are installed in a rectangular symmetrical manner at the four ends of the chassis frame (8), with the chassis geometric center as the center of symmetry. Each of the steering and traveling components (1) includes: Upper rack (20) The lower frame (36) can rotate 360° relative to the upper frame (20) about its vertical axis. Wheels (16) are mounted on the lower frame (36), and A drive unit is used to independently drive the rotation of the wheels (16) and the full rotation of the lower frame (36); Four contouring adjustment components, each of which is connected to the upper frame (20) of one of the steering and walking components (1) and the chassis frame (8), are used to actively adjust the vertical position of the steering and walking component (1) relative to the chassis frame (8); An inertial measurement unit (7) is fixedly mounted on the chassis frame (8) and is used to measure the pitch angle of the chassis frame (8). and roll angle ; as well as The control system is electrically connected to the drive units of the four steering and walking components (1) and the four contour adjustment components. It is used to control the walking and full-turn steering motion of the chassis, and to perform active stability control of the position and posture of the chassis frame (8) through the contour adjustment components based on the measurement data of the inertial measurement unit (7).

2. The four-wheel independent drive full-rotation contour chassis according to claim 1, characterized in that, The steering and walking component (1) is vertically and slidably connected to the chassis frame (8) through a guide mechanism; The guiding mechanism includes a guide shaft support (5) mounted on the chassis frame (8) and a guide shaft sleeve (2) mounted on the steering and traveling component (1), as well as a guide shaft (4) that is slidably fitted between the guide shaft support (5) and the guide shaft sleeve (2). The drive unit includes a servo motor one (29) and a servo motor two (30) installed on the upper frame (20) of the steering and walking component (1). The servo motor one (29) drives the wheel (16) to rotate, and the servo motor two (30) drives the lower frame (36) to rotate in a full rotation. The contouring adjustment component includes a slide base (15) mounted on the upper frame (20), a lead screw (26) rotatably mounted on the slide base (15), a slider (14) cooperating with the lead screw (26), a servo motor (28) driving the lead screw (26), and a spring damper (25) connected between the slider (14) and the chassis frame (8). It also includes a displacement sensor (27) for measuring the displacement of the slider (14).

3. The four-wheel independent drive full-rotation contour chassis according to claim 1, characterized in that, The steering and walking component (1) is a two-degree-of-freedom differential gear train structure, and its input is the rotational speed of servo motor (29). and the rotational speed of servo motor 2 (30) The output is the rotational speed of the wheel (16) around the axis of the wheel bearing seat (38). and the steering speed around the axis of rotation of the steering travel component (1) And satisfy: in, The transmission ratio between the driving gear (18) and the driven gear (19) is given. The transmission ratio of the right-angle bevel gearbox (37) is given.

4. The four-wheel independent drive full-rotation contour-following chassis according to claim 1, characterized in that, The control system includes an intelligent controller (39) and a programmable controller (41). The intelligent controller (39) integrates a motion mode control model, which is used to calculate the desired linear velocity and desired turning angle of the four wheels (16) based on the received motion mode signal and motion parameter signal, and drive the corresponding servo motor one (29) and servo motor two (30) through the programmable controller (41) to realize various motion modes such as differential motion, Ackerman motion, crab motion, four-wheel steering and stationary turning.

5. The four-wheel independent drive full-rotation contour-following chassis according to claim 4, characterized in that, The intelligent controller (39) also integrates a pose stability control model, which is used to determine the pitch angle measured by the inertial measurement unit (7). and roll angle The road surface excitation is calculated based on the displacement of the slider measured by the displacement sensor (27), and the target displacement of the four sliders (14) is calculated based on the road surface excitation in order to perform active stability control on the position of the chassis frame (8).

6. The four-wheel independent drive full-rotation contour chassis according to claim 1, characterized in that, It also includes an encoder (31), which is coaxially arranged with the rotation axis of the steering and travel component (1) and is used to measure the rotation angle value of the wheel (16) in real time.

7. A method for controlling the posture stability of a four-wheel independent drive full-rotation contoured chassis as described in any one of claims 1 to 6, characterized in that, The process includes the following steps: Step S1: The control system collects the pitch angle θ and roll angle φ of the chassis frame (8) measured by the inertial measurement unit (7) in real time, as well as the displacement of the four sliders (14) measured by the displacement sensor (27); Step S2: Establish the dynamic model of the chassis posture stability and transform the state space equation of the 11-degree-of-freedom continuous system. The state space equation takes the slider displacement as the control input and the pitch angle and roll angle as the controlled output; Step S3: Based on the linear quadratic regulator LQR algorithm, construct the optimal LQR controller with the target performance index J containing state error and control energy consumption as the objective function; Step S4: Solve the Riccati equation to obtain the state feedback gain matrix K, and calculate the optimal control law that minimizes the performance index J, and output the target displacement of the four sliders (14); Step S5: Drive the servo motor three (28) to make the four sliders (14) reach the target displacement, and realize the active stabilization control of the pitch angle and roll angle of the chassis frame (8).

8. The method for controlling the position and posture stability of a four-wheel independent drive full-rotation contoured chassis according to claim 7, characterized in that... It lies in, The target performance index J is defined as follows: In the formula, , , , These represent the corresponding displacements of the four sliders (14). This represents the average displacement of the four sliders (14). As a performance indicator, it is adjusted to maintain the ground clearance of the entire chassis. , , , , These are the state weighting coefficients for pitch angle, pitch rate, roll angle, roll rate, and average displacement of the slide, respectively. , , , These are the control weight coefficients for the outputs of the four slides.

9. The pose stability control method according to claim 8, characterized in that, The state-space equation is: Among them, state variables , Represents a column vector of 22*1 dimensions; Input variables , Represents a 4x1 dimension column vector; Output vector , Represents a column vector of 3*1 dimensions; perturbation vector , Represents a 4x1 dimension column vector; ， State matrix A is derived from a 22-dimensional state vector x, where, Indicates the speed at the center of gravity of the chassis; This indicates the displacement and velocity at the chassis center of gravity; This indicates the pitch rate of the chassis; Indicates the chassis pitch angle; This indicates the roll rate of the chassis; Indicates the chassis roll angle; This indicates the vertical speed of the left front wheel of the chassis; This indicates the vertical speed of the right front wheel of the chassis; This indicates the vertical speed of the left rear wheel of the chassis; This indicates the vertical speed of the right rear wheel of the chassis; This indicates the vertical displacement of the left front wheel of the chassis; This indicates the vertical displacement of the right front wheel of the chassis; This indicates the vertical displacement of the left rear wheel of the chassis; This indicates the vertical displacement of the right rear wheel of the chassis; This indicates the speed of the left front wheel slider; This indicates the speed of the right front wheel slider; This indicates the speed of the left rear wheel slider; This indicates the speed of the right rear wheel slider; This indicates the displacement of the left front wheel slider; This indicates the displacement of the right front wheel slider; This indicates the displacement of the left rear wheel slider; This indicates the displacement of the right rear wheel slider; Similarly, the input matrix B is derived from the 4-dimensional input vector u, where, This indicates the displacement of the slider in the left front wheel tandem active suspension system. This indicates the displacement of the slider in the right front wheel tandem active suspension system. This indicates the displacement of the slider in the left rear wheel tandem active suspension system. This indicates the displacement of the slider in the right rear wheel tandem active suspension system; The output matrix C is listed based on the 3D output vector y, where, Indicates pitch angle, Indicates the roll angle. This represents the average displacement of the four sliders.

10. The method for controlling the posture stability of a four-wheel independent drive full-rotation contoured chassis according to claim 9, characterized in that, The road surface excitation input Calculated using the following formula: in, This indicates the road's effect on the left front wheel; This indicates the road's stimulus to the right front wheel; This indicates the stimulus from the road surface to the left rear wheel; This indicates the excitation of the road surface onto the right rear wheel; Indicates the distance between the front axle and the geometric center of the chassis; This indicates the distance between the rear axle and the geometric center of the chassis. Indicates the front wheel track width; Indicates the rear wheel track width; This represents the vehicle pitch angle measured by the IMU; This represents the vehicle body roll angle measured by the IMU; This represents the value measured by the displacement sensor for the left front wheel tandem active suspension system. This represents the value measured by the displacement sensor for the right front wheel tandem active suspension system. This represents the value of the left rear wheel tandem active suspension system measured by the displacement sensor; This represents the value of the right rear wheel tandem active suspension system measured by the displacement sensor.

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