High-precision steer-by-wire mechanism of composite mobile robot and steering method of high-precision steer-by-wire mechanism

Abstract

The invention relates to the technical field of steer-by-wire, in particular to a high-precision steer-by-wire mechanism of a composite mobile robot and a steering method thereof, the steering mechanism comprises a steering structure and a vehicle-mounted controller, and the steering structure comprises a left wheel set mechanism, a right wheel set mechanism and a steering mechanism. And the vehicle-mounted controller calculates the difference between the actual tire rotation angle and the theoretical rotation angle, and the optimized speed data processed by the optimization algorithm is fed back to the left wheel set mechanism, the right wheel set mechanism and the steering mechanism. By measuring the speed difference of the rear wheels, the actual steering angle of the wheels and the theoretical steering angle of the steering motor are calculated according to the mechanical characteristics of the steering system; a steering angle compensation mechanism and a wheel speed compensation mechanism are introduced, and the wheel speed and angle errors occurring in the steering process can be optimized through an algorithm; the dynamic errors are adjusted in real time through a motion compensation control algorithm, it is ensured that the speeds of the four wheels are accurately matched with the turning radius, and the precision of the steering process and the control stability of the vehicle are remarkably improved through the method.

Description

Technical Field

[0001] The invention relates to the technical field of wire-controlled steering, and in particular to a high-precision wire-controlled steering mechanism of a composite mobile robot and a steering method thereof. Background Art

[0002] Steering-by-wire is one of the important components of the steering-by-wire chassis. It refers to the steering function of the vehicle realized through an electronic control system, including the control of the steering angle and the adjustment of the steering force. The turning performance of the steering-by-wire chassis is mainly determined by its path tracking ability in automatic navigation. Under actual working conditions, the steering accuracy directly affects the performance of the steering-by-wire chassis in terms of turning passability and tracking navigation accuracy. Vehicles equipped with the steering-by-wire chassis are easily disturbed by road stimuli when driving in complex environments. Therefore, in practical applications, in order to alleviate the above-mentioned interference, the research on high-precision control methods for steering of the steering-by-wire chassis has received widespread attention.

[0003] Traditional steering designs mostly use rack and pinion steering systems combined with Ackerman steering geometry. They are widely used in many types of vehicles because of the driving accuracy and reliability they provide. However, they have the following disadvantages when used on medium and low speed drive-by-wire chassis:

[0004] 1. Complexity and space utilization. Compared with the more traditional bevel gear steering system, the rack and pinion steering system is more complex, which increases the manufacturing cost and requires a relatively straight space to accommodate the rack, which may limit the layout of other components in some vehicle designs, especially the highly integrated wire-controlled chassis.

[0005] 2. Ackerman geometry error: Although Ackerman geometry design can optimize tire movement during steering, it is difficult to achieve perfection in practical applications. Under different vehicle speeds or load conditions, the actual tire movement may not completely match the ideal Ackerman steering, resulting in tire wear and reduced steering efficiency.

[0006] 3. Steering stability. Irregularities in the road surface can bring multi-directional excitations to the vehicle. These excitations are mainly caused by the impact force caused by potholes and unevenness on the road surface. When these impact forces act on the tires, the tire position will change instantly, which will affect the performance of the entire steering system. This impact is manifested as a decrease in steering accuracy. Specifically, the vehicle's steering response may no longer be so sensitive or predictable, resulting in a decrease in navigation accuracy. In addition, frequent impacts may also cause accelerated wear of steering system components, such as steering linkages, ball heads, or gear racks, further reducing the vehicle's handling stability and safety.

[0007] Application number CN202210285181.1, this invention integrates the wire-controlled steering mechanism and the hydraulic system, and uses the rotation angle to control the left and right hydraulic cylinders. At the same time, the actual steering angle is monitored and fed back by the photoelectric sensor installed at the center of the front axle and the scale on the steering tie rod, so as to realize the automatic correction of the steering accuracy and form a closed-loop control system. This design improves the control accuracy of the traditional pure hydraulic steering system in the field of autonomous driving, and effectively solves the problem of insufficient accuracy of wire-controlled steering. However, in the application environment of medium and low-speed wire-controlled chassis, the continuous impact of dynamic road excitation on the steering system will have a continuous negative impact on the steering accuracy. The cumulative error caused by this impact may have a significant impact on the positioning and accuracy of the overall navigation system, thereby placing higher requirements on the reliability and accuracy of the automatic navigation function. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a high-precision wire-controlled steering mechanism and a steering method for a composite mobile robot.

[0009] A high-precision wire-controlled steering mechanism for a composite mobile robot comprises a steering structure and a vehicle-mounted controller, wherein the steering structure comprises a left wheel assembly mechanism, a right wheel assembly mechanism and a steering mechanism, and the vehicle-mounted controller establishes an independent closed-loop control circuit for the left wheel assembly mechanism, the right wheel assembly mechanism and the steering mechanism to achieve accurate monitoring and adjustment of each part; the vehicle-mounted controller calculates the difference between the actual tire turning angle and the theoretical turning angle, and then processes the data through an optimization algorithm to determine the optimal tire speed, and the optimized speed data is fed back to the left wheel assembly mechanism, the right wheel assembly mechanism and the steering mechanism for real-time adjustment to ensure continuous optimization of the tire speed and steering angle.

[0010] The left wheel assembly mechanism includes a left upper suspension swing arm and a left lower suspension swing arm respectively hinged to the front axle welded body arranged on the steering mechanism, a left steering cup is arranged between the left upper suspension swing arm and the left lower suspension swing arm, the upper part of the left steering cup is connected to the left upper suspension swing arm through the left upper L-shaped joint bearing, the lower part of the left steering cup is connected to the left lower suspension swing arm through the left lower L-shaped joint bearing, a left steering connecting rod is arranged on the left steering cup, a left wheel hub motor is connected to the left steering cup, a left shock absorber is also hingedly installed on the left lower suspension swing arm, and the other end of the left shock absorber is hinged to the front axle welded body arranged on the steering mechanism.

[0011] The right wheel assembly mechanism includes a right upper suspension swing arm and a right lower suspension swing arm hinged to a front axle welded body arranged on the steering mechanism; a right steering cup is arranged between the right upper suspension swing arm and the right lower suspension swing arm; the upper part of the right steering cup is connected to the right upper suspension swing arm through a right upper L-shaped joint bearing; the lower part of the right steering cup is connected to the right lower suspension swing arm through a right lower L-shaped joint bearing; a right steering connecting rod is arranged on the right steering cup; a right wheel hub motor is installed on the right steering cup; a right shock absorber is also hingedly installed on the right lower suspension swing arm; the other end of the right shock absorber is hinged to the front axle welded body arranged on the steering mechanism.

[0012] The steering mechanism also includes a motor mounting seat installed on the front axle frame, a slider mounting plate arranged on the front axle welding body, a slider 1 fixed on the slider mounting plate, a guide rail slidably matched with the slider 1 and arranged horizontally, a shift fork and a slide rail fixed on the guide rail, the slide rail is arranged vertically, and a slider 2 is slidably matched on the slide rail, and a left fisheye bearing 1 and a right fisheye bearing 1 are respectively provided on the left and right sides of the shift fork, the left fisheye bearing 1 is sequentially connected with a left steering rod and a left fisheye bearing 2, and the right fisheye bearing 1 is sequentially connected with a right steering rod and a right fisheye bearing 2, a steering motor is installed on the motor mounting seat, and the output shaft of the steering motor is connected with a motor rocker arm, and the motor rocker arm is connected to the slider 2 through a bearing, the left fisheye bearing 2 is connected to the left steering connecting rod on the left wheel group mechanism, and the right fisheye bearing 2 is connected to the right steering connecting rod on the right wheel group mechanism.

[0013] The left fisheye bearing and the right fisheye bearing are respectively connected to the left and right ends of the shift fork; the left steering rod is threadedly connected to the left fisheye bearing one, the right steering rod is threadedly connected to the right fisheye bearing one, the other end of the left steering rod is threadedly connected to the left fisheye bearing two, and the other end of the right steering rod is threadedly connected to the right fisheye bearing two.

[0014] A steering method for a high-precision wire-controlled steering mechanism of a composite mobile robot, the specific steps of which are as follows:

[0015] S1: The steering motor rotates to drive the motor rocker arm to rotate, so as to drive the slider 2 to slide along the slide rail, and the shift fork follows the guide rail and is guided by the slider 1 to make a linear motion along the horizontal direction relative to the front axle frame, thereby driving the left steering rod and the right steering rod to move;

[0016] S2: The left steering rod drives the movement of the left fisheye bearing 2, and drives the left steering cup to rotate through the left steering connecting rod. Similarly, the right steering rod drives the movement of the right fisheye bearing 2, and drives the right steering cup to rotate through the right steering connecting rod;

[0017] S3. During the rotation process, the on-board controller is used to calculate the steering compensation, steering angle and speed, speed error compensation, and angle error compensation, and the calculations are fed back to the left wheel hub motor, the right wheel hub motor, and the steering motor.

[0018] The logic formula of the steering parameter compensation of the steering compensation is:

[0019] Based on the known three-dimensional road excitation, the dynamic balance relationship between the steering torque of the steering motor and the road excitation is inferred:

[0020]

[0021] The steering angle and speed are: if the speeds of the left rear wheel and the right rear wheel are known, the steering angle and speed of the two front wheels can be calculated theoretically according to the speed difference of the rear wheels, which can be specifically expressed as:

[0022]

[0023] The speed error compensation is as follows: when the vehicle body turns left, the inner wheel, i.e. the left wheel, is used as the reference, the steering angle and tire speed of the left wheel are matched to the theoretical value, and the steering angle of the steering motor is calculated. Due to the limitation of the steering structure, the steering angle of the right wheel cannot be completely consistent with the actual angle, so the speed of the right wheel is adjusted to match the instantaneous speed center and turning radius of the vehicle body:

[0024] The optimized speed vδra of the right front wheel:

[0025]

[0026] The angle error compensation is as follows: after the three-dimensional road excitation is determined, the initial left front wheel and right front wheel speeds are given, and the steering motor angle at this moment can be calculated. When the initial speed values ​​of the left and right wheels are given, V li 、V ai , at this time, the initial value of the motor angle γi under the influence of road excitation is:

[0027] γi=f1(V li ,V ri )

[0028] At this moment, the kinematically optimized two-wheel expected speed V le 、V ae for:

[0029]

[0030] The beneficial effects of the present invention are as follows: the present invention measures the speed difference of the rear wheels and calculates the actual steering angle of the wheel and the theoretical steering angle of the steering motor according to the mechanical characteristics of the steering system; then by introducing the steering angle compensation and wheel speed compensation mechanisms, the algorithm can optimize the wheel speed and angle errors that occur during the steering process; the PID control algorithm is used to adjust these dynamic errors in real time to ensure the precise matching of the speed of the four wheels and the turning radius. This method significantly improves the accuracy of the steering process and the handling stability of the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0032] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0033] Figure 2 It is a schematic diagram of the three-dimensional structure of the steering structure of the present invention;

[0034] Figure 3 It is a three-dimensional structural schematic diagram of the left wheel assembly mechanism and the right wheel assembly mechanism of the present invention;

[0035] Figure 4 It is a three-dimensional structural schematic diagram of the steering mechanism of the present invention;

[0036] Figure 5 It is a control flow chart of the present invention;

[0037] Figure 6 It is a schematic diagram of steering compensation of the present invention;

[0038] Figure 7 It is a schematic diagram of the principle analysis of the steering angle and speed of the present invention;

[0039] Figure 8 It is a schematic diagram of the principle of speed error compensation of the present invention;

[0040] Fig. 9 It is a schematic diagram of the principle of angle error compensation of the present invention;

[0041] Figure numerals: Ⅰ, steering structure; Ⅱ, on-board controller; 1, left wheel assembly mechanism; 2, right wheel assembly mechanism; 3, steering mechanism; 101, left wheel hub motor; 102, left steering cup; 103, upper left L-shaped joint bearing; 104, left steering connecting rod; 105, upper left suspension swing arm; 106, left shock absorber; 107, lower left suspension swing arm; 108, lower left L-shaped joint bearing; 201, right shock absorber; 202, upper right suspension swing arm; 203, upper right L-shaped joint bearing; 204, right steering cup; 205, right wheel hub motor; 2 06, right steering rod; 207, right lower L-shaped spherical bearing; 208, right lower suspension swing arm; 301, front axle welding body; 302, slider 1; 303, fork; 304, slide rail; 305, right fisheye bearing 1; 306, right steering rod; 307, right fisheye bearing 2; 308, slider 2; 309, motor rocker arm; 310, motor mounting seat; 311, steering motor; 312, left fisheye bearing 1; 313, left steering rod; 314, left fisheye bearing 2; 315, slider mounting plate; 316, guide rail. DETAILED DESCRIPTION

[0042] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below.

[0043] like Figures 1 to 9 As shown, a high-precision wire-controlled steering mechanism of a composite mobile robot includes a steering structure I and a vehicle-mounted controller II. The steering structure I includes a left wheel assembly mechanism 1, a right wheel assembly mechanism 2, and a steering mechanism 3. The initial speed of the vehicle is input as the system reference data, and then the vehicle-mounted controller II establishes independent closed-loop control circuits for the left wheel assembly mechanism 1, the right wheel assembly mechanism 2, and the steering mechanism 3 to achieve accurate monitoring and adjustment of each part. For specific closed-loop control circuits, see the attached Figure 5 The wheel hub motor 1 and the wheel hub motor 2 correspond to the left wheel hub motor 101 and the right wheel hub motor 205 respectively, and the control of the steering motor of the steering mechanism 3 is located at Figure 5 middle position.

[0044] The on-board controller II can calculate the difference between the actual tire angle and the theoretical motor angle through high-precision sensors and algorithms, and then process these data through optimization algorithms to determine the optimal tire speed. The optimized speed data is fed back to the steering mechanism 3 for real-time adjustment to ensure continuous optimization of tire speed and steering angle.

[0045] The left wheel assembly mechanism 1 includes an upper left suspension arm 105 and a lower left suspension arm 107 respectively hinged to the front axle welded body 301 arranged on the steering mechanism 3, and a left steering cup 102 is arranged between the upper left suspension arm 105 and the lower left suspension arm 107. The upper part of the left steering cup 102 is connected to the upper left suspension arm 105 through an upper left L-shaped joint bearing 103, and the lower part of the left steering cup 102 is connected to the lower left suspension arm 107 through a lower left L-shaped joint bearing 108. A left steering connecting rod 104 is arranged on the left steering cup 102, and a left wheel hub motor 101 is connected to the left steering cup 102. A left shock absorber 106 is also hingedly installed on the lower left suspension arm 107, and the other end of the left shock absorber 106 is hinged to the front axle welded body 301 arranged on the steering mechanism 3.

[0046] The right wheel assembly mechanism 2 includes a right upper suspension swing arm 202 and a right lower suspension swing arm 208 which are hinged to a front axle welded body 301 arranged on the steering mechanism 3. A right steering cup 204 is arranged between the right upper suspension swing arm 202 and the right lower suspension swing arm 208. The upper part of the right steering cup 204 is connected to the right upper suspension swing arm 202 through a right upper L-shaped joint bearing 203. The lower part of the right steering cup 204 is connected to the right lower suspension swing arm 208 through a right lower L-shaped joint bearing 207. A right steering connecting rod 206 is arranged on the right steering cup 204. A right wheel hub motor 205 is installed on the right steering cup 204. A right shock absorber 201 is also hingedly installed on the right lower suspension swing arm 208. The other end of the right shock absorber 201 is hinged to the front axle welded body 301 arranged on the steering mechanism 3.

[0047] The steering mechanism 3 also includes a motor mounting seat 310 mounted on the front axle frame, a slider mounting plate 315 arranged on the front axle welded body 301, a slider 1 302 fixed on the slider mounting plate 315, a guide rail 316 slidably matched with the slider 1 302 and arranged horizontally, a shift fork 303 and a slide rail 304 fixed on the guide rail 316, the slide rail 304 is arranged vertically, and a slider 2 308 is slidably matched on the slide rail 304, and a left fisheye bearing 1 312 and a right fisheye bearing 1 305 are respectively provided on the left and right sides of the shift fork 303, and the left fisheye bearing 1 312 is sequentially connected with a left steering rod 313 and a left fisheye bearing 314, the right fisheye bearing 305 is sequentially connected with a right steering rod 306 and a right fisheye bearing 307, a steering motor 311 is mounted on the motor mounting seat 310, the output shaft of the steering motor 311 is connected with a motor rocker arm 309, the motor rocker arm 309 is connected to a slider 308 through a bearing, the left fisheye bearing 314 is connected to the left steering link 104 on the left wheel assembly mechanism 1, and the right fisheye bearing 307 is connected to the right steering link 206 on the right wheel assembly mechanism 2.

[0048] A single steering motor 311 is used to drive a slider rail mechanism, which is combined with the independent suspension of each wheel. The geometric relationship of the steering trapezoid is used to calculate the relationship between the dynamic change of the tire caused by road excitation and the motor angle and wheel angle.

[0049] In response to the possible torque imbalance at both ends of the steering motor 311, the on-board controller II uses a carefully calculated dynamic balance equation to make real-time adjustments to achieve dynamic balance of torque and ensure steering accuracy and vehicle stability.

[0050] The left fisheye bearing 1 312 and the right fisheye bearing 1 305 are respectively connected to the left and right ends of the fork 303; the left steering rod 313 is threadedly connected to the left fisheye bearing 1 312, the right steering rod 306 is threadedly connected to the right fisheye bearing 1 305, the other end of the left steering rod 313 is threadedly connected to the left fisheye bearing 2 314, and the other end of the right steering rod 306 is threadedly connected to the right fisheye bearing 2 307.

[0051] A steering method for a high-precision wire-controlled steering mechanism of a composite mobile robot, the specific steps of which are as follows:

[0052] S1: The steering motor 311 rotates to drive the motor rocker arm 309 to rotate, so as to drive the slider 2 308 to slide along the slide rail 304, and the fork 303 follows the guide rail 316 and is guided by the slider 1 302 to make a linear motion along the horizontal direction relative to the front axle frame, thereby driving the left steering rod 313 and the right steering rod 306 to move;

[0053] S2: The left steering rod 313 drives the movement of the left fisheye bearing 2 314, and drives the left steering cup 102 to rotate through the left steering link 104. Similarly, the right steering rod 306 drives the movement of the right fisheye bearing 2 307, and drives the right steering cup 204 to rotate through the right steering link 206.

[0054] S3. During the rotation process, the on-board controller II is used to calculate the steering compensation, steering angle and speed, speed error compensation, and angle error compensation, and feeds back to the left wheel hub motor 101, the right wheel hub motor 205, and the steering motor 311.

[0055] The steering compensation is as follows Figure 6 As shown, the logical formula for steering parameter compensation is:

[0056] Based on the known three-dimensional road excitation, the dynamic balance relationship between the steering torque of the steering motor and the road excitation is inferred:

[0057]

[0058] Among them, F wxl 、F wxrRespectively represent the lateral excitation of the left and right wheels; F wxl 、F wxr Respectively represent the longitudinal excitation of the left and right wheels; m w Indicates tire quality; v L , Respectively represent the speed and acceleration of the left wheel; v R , Respectively represent the speed and acceleration of the right wheel;

[0059] The steering angle and speed are as follows Figure 7 As shown: Given the speeds of the left rear wheel and the right rear wheel, the steering angle and speed of the two front wheels can be calculated theoretically based on the speed difference of the rear wheels, which can be specifically expressed as:

[0060]

[0061] v lf 、v rf are the translational speeds of the left and right rear wheels respectively; vlf and vrf are the rotational speeds of the two rear wheels; wheelbase H, wheelbase W, front wheel turning angle φ, and the rotation angle φ of the left and right front wheels la ,φ ra .

[0062] The speed error compensation is as follows Figure 8 As shown: when the vehicle body turns left, the inner wheel, i.e., the left wheel, is used as a reference, the steering angle of the left wheel and the tire speed are matched to the theoretical value, and the steering angle of the steering motor 311 is calculated. Due to the limitation of the steering structure, the steering angle of the right wheel cannot be completely consistent with the actual angle, so the speed of the right wheel is adjusted to match the instantaneous center of speed and the turning radius of the vehicle body:

[0063] The optimized speed vδra of the right front wheel:

[0064]

[0065] Among them, δr is the difference between the theoretical turning angle φra of the right wheel and the actual turning angle αr; R δr is the actual turning radius of the right wheel; v f is the virtual rear wheel linear speed; R f is the turning radius.

[0066] The angle error compensation is as follows Fig. 9 As shown, after the three-dimensional road excitation is determined, the initial rotation speeds of the left and right front wheels are given, and the steering angle of the steering motor 311 at this moment can be calculated. When the initial speed values ​​of the left and right wheels are given as V li 、V ri , at this time, the initial value of the motor angle γi under the influence of road excitation is:

[0067] γi=f1(Vli ,V ri )

[0068] Among them, f1 is the road friction coefficient.

[0069] At this moment, the kinematically optimized two-wheel expected speed V le 、V ae for:

[0070]

[0071] At a certain moment, when the road excitation is determined, the steering angle of the steering motor and the expected speed of the left and right front wheels can be calculated as long as the speed of the left and right wheels is given, thereby ensuring that the vehicle travels along the expected path.

[0072] The present invention measures the speed difference of the rear wheels and calculates the actual steering angle of the wheel and the theoretical steering angle of the steering motor according to the mechanical characteristics of the steering mechanism; then by introducing the steering angle compensation and wheel speed compensation mechanisms, the algorithm can optimize the wheel speed and angle errors that occur during the steering process; the PID control algorithm is used to adjust these dynamic errors in real time to ensure the precise matching of the speed of the four wheels and the turning radius. This method significantly improves the accuracy of the steering process and the handling stability of the vehicle.

[0073] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only describe the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A high-precision wire-controlled steering mechanism for a composite mobile robot, characterized in that: The invention comprises a steering structure (I) and a vehicle-mounted controller (II). The steering structure (I) comprises a left wheel assembly mechanism (1), a right wheel assembly mechanism (2) and a steering mechanism (3). The vehicle-mounted controller (II) establishes an independent closed-loop control circuit for the left wheel assembly mechanism (1), the right wheel assembly mechanism (2) and the steering mechanism (3) to achieve accurate monitoring and adjustment of each part. The vehicle-mounted controller (II) calculates the difference between the actual tire turning angle and the theoretical turning angle, and then processes the data through an optimization algorithm to determine the optimal tire speed. The optimized speed data is fed back to the left wheel assembly mechanism (1), the right wheel assembly mechanism (2) and the steering mechanism (3) for real-time adjustment to ensure continuous optimization of the tire speed and the steering angle.

2. The high-precision wire-controlled steering mechanism of a composite mobile robot according to claim 1, characterized in that: The left wheel assembly mechanism (1) comprises a left upper suspension swing arm (105) and a left lower suspension swing arm (107) respectively hinged to a front axle welding body (301) arranged on a steering mechanism (3); a left steering cup (102) is arranged between the left upper suspension swing arm (105) and the left lower suspension swing arm (107); the upper part of the left steering cup (102) is connected to the left upper suspension swing arm (105) via a left upper L-shaped joint bearing (103); and the left steering cup (102) is connected to the left upper suspension swing arm (105) via a left upper L-shaped joint bearing (103). 2) The lower part is connected to the left lower suspension swing arm (107) through a left lower L-shaped joint bearing (108); the left steering cup (102) is provided with a left steering link (104); the left steering cup (102) is connected with a left wheel hub motor (101); the left lower suspension swing arm (107) is also hingedly mounted with a left shock absorber (106); the other end of the left shock absorber (106) is hingedly connected to a front axle welding body (301) provided on the steering mechanism (3).

3. The high-precision wire-controlled steering mechanism of a composite mobile robot according to claim 2, characterized in that: The right wheel assembly mechanism (2) comprises a right upper suspension swing arm (202) and a right lower suspension swing arm (208) which are hinged to a front axle welding body (301) arranged on a steering mechanism (3); a right steering cup (204) is arranged between the right upper suspension swing arm (202) and the right lower suspension swing arm (208); the upper part of the right steering cup (204) is connected to the right upper suspension swing arm (202) via a right upper L-shaped joint bearing (203); and the right steering cup (204) is connected to the right upper suspension swing arm (202) via a right upper L-shaped joint bearing (203). The lower part of the right steering cup (204) is connected to the right lower suspension swing arm (208) through a right lower L-shaped joint bearing (207), the right steering cup (204) is provided with a right steering link (206), the right steering cup (204) is installed with a right wheel hub motor (205), the right lower suspension swing arm (208) is also hingedly installed with a right shock absorber (201), and the other end of the right shock absorber (201) is hingedly connected to a front axle welding body (301) arranged on the steering mechanism (3).

4. The high-precision wire-controlled steering mechanism of a composite mobile robot according to claim 3, characterized in that: The steering mechanism (3) further comprises a motor mounting seat (310) mounted on the front axle frame, a slider mounting plate (315) arranged on the front axle welded body (301), a slider 1 (302) fixed on the slider mounting plate (315), a guide rail (316) slidingly matched with the slider 1 (302) and arranged transversely, a shift fork (303) and a slide rail (304) fixed on the guide rail (316), the slide rail (304) being arranged vertically, a slider 2 (308) being slidingly matched on the slide rail (304), a left fisheye bearing 1 (312) and a right fisheye bearing 1 (305) being respectively arranged on the left and right sides of the shift fork (303), the left fisheye bearing 1 (312) and the right fisheye bearing 1 (305) being arranged on the right and left sides of the shift fork (303), the left fisheye bearing 1 (316) and the right fisheye bearing 1 (305) being arranged on the left and right sides of the shift fork (303), the left fisheye bearing 1 (316 ... The first fisheye bearing (305) is connected to a right steering rod (306) and a right fisheye bearing (307) in sequence; a steering motor (311) is installed on the motor mounting seat (310); the output shaft of the steering motor (311) is connected to a motor rocker arm (309); the motor rocker arm (309) is connected to a slider (308) through a bearing; the second fisheye bearing (314) is connected to a left steering rod (104) on the left wheel assembly mechanism (1); and the second fisheye bearing (307) is connected to a right steering rod (206) on the right wheel assembly mechanism (2).

5. A steering method using a high-precision wire-controlled steering mechanism of a composite mobile robot according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: S1: The steering motor (311) rotates to drive the motor rocker arm (309) to rotate, so as to drive the slider 2 (308) to slide along the slide rail (304), and the shift fork (303) follows the guide rail (316) and is guided by the slider 1 (302) to make a linear motion along the horizontal direction relative to the front axle frame, thereby driving the left steering rod (313) and the right steering rod (306) to move; S2: The left steering rod (313) drives the movement of the left fisheye bearing 2 (314), and drives the left steering cup (102) to rotate through the left steering connecting rod (104). Similarly, the right steering rod (306) drives the movement of the right fisheye bearing 2 (307), and drives the right steering cup (204) to rotate through the right steering connecting rod (206); S3. During the rotation process, the on-board controller (II) is used to calculate the steering compensation, steering angle and speed, speed error compensation, and angle error compensation, and the calculations are fed back to the left wheel hub motor (101), the right wheel hub motor (205), and the steering motor (311).

6. The steering method according to claim 5, characterized in that: The logic formula of the steering parameter compensation of the steering compensation is: Based on the known three-dimensional road excitation, the dynamic balance relationship between the steering torque of the steering motor and the road excitation is inferred:

7. The steering method according to claim 5, characterized in that: The steering angle and speed are: if the speeds of the left rear wheel and the right rear wheel are known, the steering angle and speed of the two front wheels can be calculated theoretically according to the speed difference of the rear wheels, which can be specifically expressed as:

8. The steering method according to claim 5, characterized in that: The speed error compensation is as follows: when the vehicle body turns left, the inner wheel, i.e., the left wheel, is used as a reference, the steering angle and tire speed of the left wheel are matched to the theoretical value, and the steering angle of the steering motor (311) is calculated. Due to the limitation of the steering structure, the steering angle of the right wheel cannot be completely consistent with the actual angle, so the speed of the right wheel is adjusted to match the instantaneous center of speed and the turning radius of the vehicle body: The optimized speed vδra of the right front wheel:

9. The steering method according to claim 5, characterized in that: The angle error compensation is as follows: after the three-dimensional road excitation is determined, the initial rotation speeds of the left front wheel and the right front wheel are given, and the rotation angle of the steering motor (311) at this moment can be calculated. When the initial speed values ​​of the left and right wheels are given as V li 、V ai , at this time, the initial value of the motor angle γi under the influence of road excitation is: γi=f1(V li ,V ri ) At this moment, the kinematically optimized two-wheel expected speed V le 、V ae for:

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