A vehicle hill driving dynamics characteristic simulation test system

Abstract

The application discloses a kind of vehicle slope driving dynamics characteristic simulation test systems, including mechanical executive mechanism and measurement and control system;Mechanical executive mechanism includes six degrees of freedom platform, conveyor belt and Ackerman steering electric drive car model;Conveyor belt is fixed to six degrees of freedom platform, and Ackerman steering electric drive car model is placed on conveyor belt;Six degrees of freedom platform is used to simulate slope terrain;Measurement and control system includes inclination simulation drive subsystem, conveyor belt measurement and control subsystem and electric drive car model vehicle-mounted control subsystem, respectively for the control and monitoring of six degrees of freedom platform, conveyor belt and Ackerman steering electric drive car model, realize vehicle slope driving dynamics characteristic simulation test.The application adopts six degrees of freedom platform, conveyor belt and Ackerman steering electric drive vehicle model to form experimental platform, can test full slope terrain, flexibly simulate slope of different angles, substantially reduce real physical environment experiment cost.

Description

Technical Field

[0001] This invention belongs to the field of intelligent agricultural machinery technology, specifically relating to a vehicle slope driving dynamics simulation test system. Background Technology

[0002] In predominantly plain areas, BeiDou-assisted driving systems for agricultural machinery have been widely adopted and achieved good application results. However, in areas with many hills and slopes, the application effect needs to be improved. Agricultural machinery operation requires flat or load-bearing ground, but hilly terrain often lacks such conditions. In hilly and sloping operations, the lateral deviation fluctuation of the automatic driving system increases, and the control process becomes unstable, leading to decreased operation quality, reduced land utilization, and increased wear and tear on tractors and supporting equipment. To improve navigation and control performance in sloping environments, it is necessary to analyze the vehicle's dynamic characteristics on slopes through a large amount of test data. However, analyzing the vehicle's dynamic characteristics on slopes using real vehicles is costly in terms of fuel consumption and wear, inefficient, and cannot be conducted for extended periods. Therefore, it is necessary to design a simulation test platform to effectively reproduce and analyze the working conditions of tractors operating on slopes.

[0003] Studying the variation of tire vertical load and steering response characteristics by constructing a dynamic model of a tractor on a slope is an effective method. However, hilly terrain is not limited to straight driving on flat slopes. Factors causing changes in tire vertical load include acceleration and deceleration, turning, and driving on curved surfaces. Existing studies on hill steering dynamics only consider the influence of gravity and do not comprehensively consider the influence of acceleration in complex working conditions. Summary of the Invention

[0004] The main objective of this invention is to overcome the shortcomings and deficiencies of the prior art and to propose a vehicle slope driving dynamics simulation test system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A vehicle slope driving dynamics simulation test system includes a mechanical actuator and a measurement and control system;

[0007] The mechanical actuator includes a six-degree-of-freedom platform, a conveyor belt, and an Ackerman steering electric vehicle model; the conveyor belt is fixed to the six-degree-of-freedom platform, and the Ackerman steering electric vehicle model is placed on the conveyor belt; the six-degree-of-freedom platform is used to simulate sloping terrain.

[0008] The measurement and control system includes a tilt angle simulation drive subsystem, a conveyor belt measurement and control subsystem, and an electric vehicle model on-board control subsystem, which are used for the control and monitoring of the six-degree-of-freedom platform, the conveyor belt, and the Ackerman steering electric vehicle model, respectively, to realize the simulation test of the vehicle's dynamic characteristics when driving on slopes.

[0009] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0010] 1. This invention innovatively proposes to use a six-degree-of-freedom platform combined with a conveyor belt and an electric-driven vehicle model to test the vehicle's slope dynamics characteristics, which is more convenient than traditional experiments; the designed base connector is connected to the universal joint at a certain angle, which can make the entire platform more stable, and make the electric telescopic push rod have a stronger load-bearing capacity and higher efficiency.

[0011] 2. Compared with traditional vehicle slope dynamics testing methods, the present invention has lower experimental costs, saves more time and effort, can test all slope terrains and can conduct 24-hour uninterrupted testing; it uses outdoor satellite positioning and indoor lidar positioning, which reduces the requirements for the test site and makes the experiment more convenient; the system structure is simple, easy to install, and has high practicality. Attached Figure Description

[0012] Figure 1 This is an overall schematic diagram of the system of the present invention.

[0013] Figure 2 This is a schematic diagram of the mechanical actuator in this invention.

[0014] Figure 3 This is a schematic diagram of the connector and universal joint in this invention.

[0015] Figure 4 This is an overall framework diagram of the measurement and control system in this invention.

[0016] Figure 5 This is a schematic diagram of the pure tracking model of the electric vehicle model in this invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0018] Examples; such as Figure 1 As shown, a vehicle slope driving dynamics simulation test system includes a mechanical actuator and a measurement and control system;

[0019] The mechanical actuator includes a six-degree-of-freedom platform, a conveyor belt, and an Ackerman steering electric vehicle model; the conveyor belt is fixed to the six-degree-of-freedom platform, and the Ackerman steering electric vehicle model is placed on the conveyor belt; the six-degree-of-freedom platform is used to simulate sloping terrain.

[0020] The measurement and control system includes a tilt angle simulation drive subsystem, a conveyor belt measurement and control subsystem, and an electric vehicle model on-board control subsystem, which are used for the control and monitoring of the six-degree-of-freedom platform, the conveyor belt, and the Ackerman steering electric vehicle model, respectively, to realize the simulation test of the vehicle's dynamic characteristics when driving on slopes.

[0021] like Figure 2 As shown, the six-degree-of-freedom platform specifically includes casters, a lower platform, an upper platform, connectors, universal joints, and an electric telescopic push rod;

[0022] There are four casters, fixed to the lower platform, used to move the six-degree-of-freedom platform; both the upper and lower platforms are fixed with connecting parts; there are six electric telescopic push rods, located between the upper and lower platforms, with both ends of the electric telescopic push rods connected to the connecting parts via universal joints; in this embodiment, the upper and lower platforms are made of aluminum alloy plates; the required thickness of the lower platform is analyzed through static stress simulation to meet the standard of being able to bear the weight required for the experiment.

[0023] like Figure 3 As shown, the connector and the universal joint are connected by a copper column. The side of the connector that connects to the universal joint has a protrusion that forms a certain angle. The universal joint is located on the protrusion. This design allows the bottom of the electric telescopic push rod to have a certain slope, making the overall structure stronger and the bottom more stable.

[0024] In this embodiment, as Figure 4 As shown, the conveyor belt monitoring and control subsystem specifically includes:

[0025] The system includes a central control ECU, a lidar, an encoder, and a collision switch. The lidar is connected to the central control ECU via a serial port to collect vehicle pose data. The encoder is used to detect the conveyor belt speed. The central control ECU transmits the pose and speed data to the electric drive vehicle model's onboard control subsystem via wireless communication.

[0026] The electric vehicle model's onboard control subsystem specifically includes:

[0027] The vehicle includes an onboard controller, an onboard ECU, a front wheel servo, a rear wheel drive, and a data storage module. After receiving wireless data, the onboard controller runs a navigation algorithm to control the front wheel servo and the rear wheel drive. The electric-drive vehicle model is equipped with a TF card storage module.

[0028] The angle simulation drive subsystem is used to receive control commands and drive the six-degree-of-freedom platform to achieve the target attitude via serial port. Specifically:

[0029] The tilt simulation drive subsystem is connected to the six-degree-of-freedom platform. By performing inverse kinematics on the six-degree-of-freedom platform and programming, the extension of the six electric telescopic push rods is calculated. Commands are sent to control the raising and lowering of the electric telescopic push rods, thereby realizing the roll, pitch, and translation of the upper platform. The height of the four corners of the conveyor belt is adjusted to simulate various sloping terrains and achieve the target posture.

[0030] When performing simulation tests on the dynamic characteristics of vehicle driving on slopes using the system in this embodiment, the following steps are included:

[0031] The attitude is initialized, and the tilt angle simulation drive subsystem adjusts the electric telescopic push rod so that the six-degree-of-freedom platform reaches the target slope attitude.

[0032] Start the conveyor belt, monitor the position and posture of the Ackerman steering electric drive vehicle model in real time, and the encoder detects the conveyor belt speed and transmits it wirelessly.

[0033] The Ackerman steering electric vehicle model simulates driving a long slope on a conveyor belt;

[0034] Closed-loop control is implemented. The Ackerman steering electric drive vehicle model controls steering and speed based on the control algorithm to maintain the target position and record the status. The roll angle, pitch angle, heading deviation and lateral deviation information of the vehicle model are recorded in real time for subsequent analysis of slope dynamic characteristics.

[0035] In this embodiment, the pose of the Ackerman steering electric vehicle model is detected in real time, and it is divided into an outdoor positioning method and an indoor positioning method.

[0036] The outdoor positioning method is as follows:

[0037] When in an open outdoor environment, the electric-drive vehicle model is equipped with a high-precision Beidou satellite antenna; the host computer receives satellite positioning data (including latitude and longitude) in real time through a serial port, and converts it into local plane rectangular coordinate system coordinates with the center of the conveyor belt as the origin through a Gaussian projection coordinate transformation algorithm, thereby determining the absolute position of the electric-drive vehicle model on the transmission belt.

[0038] The specific indoor positioning method is as follows:

[0039] First, data collection is performed by fixing the 2D LiDAR in the middle of the side of the conveyor belt so that its scanning plane covers the area where the car model travels above the conveyor belt.

[0040] The point cloud is preprocessed by filtering the raw point cloud data collected by the lidar to remove background noise interference. By cropping the region of interest, only the point cloud data reflected by the electric vehicle model is retained.

[0041] Feature fitting and pose calculation are performed, and the least squares method is used to fit straight lines to the retained vehicle body point cloud data; assuming the vehicle body side point cloud set is as follows. The fitted straight line equation is By minimizing the sum of squared errors The straight line parameters are calculated, and the angle between the electric vehicle model and the central axis of the conveyor belt is calculated based on the slope of the fitted straight line, which is the vehicle heading angle θ. The midpoint or specific feature point of the fitted straight line segment is extracted, and its distance and angle to the origin of the lidar coordinate system are read. Then, the position (x, y) of the center of the electric vehicle model set in the platform coordinate system is calculated.

[0042] In this embodiment, the Ackerman steering electric drive vehicle model simulates driving on a long slope on a conveyor belt. It is necessary to keep the vehicle traveling along the center line of the conveyor belt and match the speed, including lateral tracking control and longitudinal speed synchronization control.

[0043] Lateral tracking control specifically includes:

[0044] Define the target path and coordinate system, such as Figure 5 As shown, a local coordinate system is established with the center of the rear axle of the electric vehicle model as the origin. The central axis of the conveyor belt is set as the desired driving path. Point P(x,y) is the pre-aiming target point selected by the measurement and control system on the central axis of the conveyor belt. x represents the lateral deviation distance of the current position of the vehicle model from the center line of the conveyor belt.

[0045] Set aiming distance (Right now Figure 5 The straight-line distance from the center of the rear axle of the vehicle to point P is dynamically adjusted according to the speed of the conveyor belt. The faster the conveyor belt speed, the more stable the conveyor belt becomes. The larger the value, the more stable the control.

[0046] Calculate steering control inputs, read vehicle pose in real time, and obtain real-time lateral deviation x; use a pure tracking algorithm to calculate the required steering angle for the front wheels of the model vehicle. :

[0047]

[0048] Where L is the wheelbase of the electric vehicle model;

[0049] Finally, the calculated steering angle It is converted into a corresponding PWM pulse width signal to control the front wheel servo of the electric-drive vehicle model.

[0050] The longitudinal speed synchronization control is specifically as follows:

[0051] The electric vehicle model controller receives the conveyor belt speed signal from the encoder and controls the speed of the rear wheel drive motor to keep the electric vehicle model's speed the same as the conveyor belt speed, thus achieving long-distance simulated driving while relatively stationary.

[0052] It should also be noted that, in this specification, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vehicle slope driving dynamics simulation test system, characterized in that, Including mechanical actuators and measurement and control systems; The mechanical actuator includes a six-degree-of-freedom platform, a conveyor belt, and an Ackerman steering electric vehicle model; the conveyor belt is fixed to the six-degree-of-freedom platform, and the Ackerman steering electric vehicle model is placed on the conveyor belt; the six-degree-of-freedom platform is used to simulate sloping terrain. The measurement and control system includes a tilt angle simulation drive subsystem, a conveyor belt measurement and control subsystem, and an electric vehicle model on-board control subsystem, which are used for the control and monitoring of the six-degree-of-freedom platform, the conveyor belt, and the Ackerman steering electric vehicle model, respectively, to realize the simulation test of the vehicle's dynamic characteristics when driving on slopes.

2. The vehicle slope driving dynamics simulation test system according to claim 1, characterized in that, The six-degree-of-freedom platform specifically includes casters, a lower platform, an upper platform, connectors, universal joints, and an electric telescopic push rod; Casters are fixed to the lower platform to enable the movement of the six-degree-of-freedom platform; both the upper and lower platforms are fixed with connecting parts; multiple electric telescopic push rods are provided, located between the upper and lower platforms, and both ends of the electric telescopic push rods are connected to the connecting parts through universal joints; The connector is connected to the universal joint via a copper post. The side of the connector that connects to the universal joint has a protrusion that forms a certain angle, and the universal joint is located on the protrusion.

3. The vehicle slope driving dynamics simulation test system according to claim 2, characterized in that, The conveyor belt monitoring and control subsystem specifically includes: The system includes a central control ECU, a lidar, an encoder, and a collision switch. The lidar is connected to the central control ECU via a serial port to collect vehicle pose data. The encoder is used to detect the conveyor belt speed. The central control ECU transmits the pose and speed data to the electric drive vehicle model's onboard control subsystem via wireless communication. The electric vehicle model's onboard control subsystem specifically includes: The vehicle includes an onboard controller, an onboard ECU, a front wheel servo motor, a rear wheel drive, and a data storage module. After receiving wireless data, the onboard controller runs a navigation algorithm to control the front wheel servo motor and the rear wheel drive. The Ackerman electric steering vehicle model is equipped with a TF card storage module.

4. The vehicle slope driving dynamics simulation test system according to claim 3, characterized in that, The tilt simulation drive subsystem receives control commands and drives the six-degree-of-freedom platform to achieve the target attitude via a serial port. Specifically: The tilt simulation drive subsystem is connected to the six-degree-of-freedom platform. By performing inverse kinematics on the six-degree-of-freedom platform and programming, the extension of each electric telescopic push rod is calculated. Commands are sent to control the raising and lowering of the electric telescopic push rods, thereby realizing the roll, pitch, and translation of the upper platform. The height of the four corners of the conveyor belt is adjusted to simulate various sloping terrains to achieve the target posture.

5. The vehicle slope driving dynamics simulation test system according to claim 4, characterized in that, The vehicle slope driving dynamics simulation test system includes the following steps when conducting simulation tests on the vehicle slope driving dynamics characteristics: The attitude is initialized, and the tilt angle simulation drive subsystem adjusts the electric telescopic push rod so that the six-degree-of-freedom platform reaches the target slope attitude. Start the conveyor belt, monitor the position and posture of the Ackerman steering electric drive vehicle model in real time, and the encoder detects the conveyor belt speed and transmits it wirelessly. The Ackerman steering electric vehicle model simulates driving a long slope on a conveyor belt; Closed-loop control is implemented. The Ackerman steering electric drive vehicle model controls steering and speed based on the control algorithm to maintain the target position and record the status. The roll angle, pitch angle, heading deviation and lateral deviation information of the vehicle model are recorded in real time for subsequent analysis of slope dynamic characteristics.

6. The vehicle slope driving dynamics simulation test system according to claim 5, characterized in that, Real-time detection of the Ackerman steering electric drive vehicle model's position and posture is divided into outdoor positioning methods and indoor positioning methods.

7. The vehicle slope driving dynamics simulation test system according to claim 6, characterized in that, The outdoor positioning method is as follows: When in an open outdoor environment, the electric-drive vehicle model is equipped with a high-precision Beidou satellite antenna; the host computer receives satellite positioning data in real time through a serial port, and converts it into local Cartesian coordinates with the center of the conveyor belt as the origin through a Gaussian projection coordinate transformation algorithm, thereby determining the absolute position of the electric-drive vehicle model on the transmission belt.

8. The vehicle slope driving dynamics simulation test system according to claim 6, characterized in that, The specific indoor positioning method is as follows: First, data collection is performed by fixing the 2D LiDAR in the middle of the side of the conveyor belt so that its scanning plane covers the area where the car model travels above the conveyor belt. The point cloud is preprocessed by filtering the raw point cloud data collected by the lidar to remove background noise interference. By cropping the region of interest, only the point cloud data reflected by the electric vehicle model is retained. Feature fitting and pose calculation are performed, and the least squares method is used to fit a straight line to the retained vehicle body point cloud data; assuming the set of point clouds on the side of the vehicle model is as follows. The fitted straight line equation is By minimizing the sum of squared errors The straight line parameters are calculated, and the angle between the electric vehicle model and the central axis of the conveyor belt is calculated based on the slope of the fitted straight line, which is the vehicle heading angle θ. The midpoint or specific feature point of the fitted straight line segment is extracted, and its distance and angle to the origin of the lidar coordinate system are read. Then, the position (x, y) of the center of the electric vehicle model set in the platform coordinate system is calculated.

9. A vehicle slope driving dynamics simulation test system according to claim 5, characterized in that, The Ackerman steering electric vehicle model simulates driving on a long slope on a conveyor belt. It is necessary to keep the vehicle traveling along the center line of the conveyor belt and match the speed, including lateral tracking control and longitudinal speed synchronization control. Lateral tracking control specifically includes: Define the target path and coordinate system. Establish a local coordinate system with the center of the rear axle of the electric vehicle model as the origin. Set the central axis of the conveyor belt as the desired driving path. Let point P(x,y) be the target point selected by the measurement and control system on the central axis of the conveyor belt. x represents the lateral deviation distance of the current position of the vehicle model from the center line of the conveyor belt. Set aiming distance This distance is dynamically adjusted based on the conveyor belt's operating speed; the faster the conveyor belt runs, the more stable it becomes. The larger the value, the more stable the control. Calculate steering control inputs, read vehicle pose in real time, and obtain real-time lateral deviation x; use a pure tracking algorithm to calculate the required steering angle for the front wheels of the model vehicle. : Where L is the wheelbase of the electric vehicle model; Finally, the calculated steering angle It is converted into a corresponding PWM pulse width signal to control the front wheel servo of the electric-drive vehicle model.

10. A vehicle slope driving dynamics simulation test system according to claim 9, characterized in that, The longitudinal speed synchronization control is specifically as follows: The electric vehicle model controller receives the conveyor belt speed signal from the encoder and controls the speed of the rear wheel drive motor to keep the electric vehicle model's speed the same as the conveyor belt speed, thus achieving long-distance simulated driving while relatively stationary.

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