Measurement System and Method for Minimum Turning Diameter and Minimum Turning Passage Circle of Automobile

Abstract

This invention belongs to the field of automotive testing, specifically relating to a measurement system and method for the minimum turning diameter and minimum turning circle of a vehicle. It includes multiple lidar sensors, a retractable bracket for mounting and adjusting the height of the lidar sensors, and a central control unit. The lidar sensors include a laser ranging module for measuring target position, a rotating module for driving the laser ranging module, and a control module. The laser ranging module is driven by a motor with an encoder disk mounted on the rotating module. The control module controls the motor drive and receives data from the laser ranging module. The control module and the central control unit are wirelessly connected. The central control unit controls the lidar operation, processes the received data, and outputs the results. This method utilizes lidar ranging and wireless transmission technology, resulting in a high degree of system automation, fast testing speed, and minimal environmental impact, effectively improving the measurement accuracy and efficiency of the minimum turning diameter and minimum turning circle of a vehicle.

Description

Technical Field

[0001] This invention belongs to the field of automotive testing, specifically relating to a measurement system and method for the minimum turning diameter and minimum turning lane circle of an automobile. Background Technology

[0002] The minimum turning diameter of a car refers to the diameter of the circle traced by the center plane of the outer steering wheel on the supporting plane when the steering wheel is turned to its limit and the car is turning at its lowest stable speed. The minimum turning circle is the channel circle formed by the smallest outer circle and the largest inner circle, where all points on the car body project onto a flat surface when the steering wheel is turned to its limit and the car is turning at its lowest stable speed. The minimum turning diameter and minimum turning circle are important indicators for evaluating vehicle maneuverability, largely characterizing the car's ability to navigate narrow, winding areas or bypass insurmountable obstacles. The smaller the turning radius and the wider the turning channel, the better the car's maneuverability.

[0003] With the development of society and the economy, people have placed higher demands on the passability and safety of automobiles. The measurement of minimum turning diameter and minimum turning lane circle diameter has become one of the basic items in automobile type approval testing. Faced with increasing testing needs, GB / T 12540-2009 specifies the test methods, but it has not yet clearly defined the vehicle trajectory display device within those methods. Currently, in the minimum turning diameter measurement test, methods such as dripping water or drawing with a pen are used. The main test involves manually measuring the trajectory diameter by tracking the turning trajectory of the vehicle tires. These test methods have high requirements for the test site, poor repeatability of the test results, and still require manual measurement, resulting in low testing efficiency.

[0004] LiDAR (Light Detection and Ranging) is characterized by high measurement accuracy, small size, and high data rate, and its application is becoming increasingly widespread in various industries. The working process of a LiDAR involves its internal laser ranging module emitting laser pulses, which are then distributed in various directions at set angular intervals by a rotating mechanism, and finally reflected by the target to the receiving module. Summary of the Invention

[0005] The purpose of this invention is to provide a measurement system and method for the minimum turning diameter and minimum turning channel circle of a car, which improves measurement efficiency while achieving accurate measurement of the minimum turning diameter and minimum turning channel circle of a car.

[0006] The technical solution to achieve the purpose of this invention is: a measurement system for the minimum turning diameter and minimum turning channel circle of an automobile, including multiple lidars, a retractable bracket for mounting the lidars and adjusting their height, and a central control unit;

[0007] The lidar includes a laser ranging module for measuring the target position, a rotation module for driving the laser ranging module to rotate, and a control module;

[0008] The laser ranging module is driven by a motor with an encoder disk mounted on the rotating module. The control module is used to control the motor drive and receive data from the laser ranging module. The control module and the central control unit are connected wirelessly.

[0009] The central control unit is used to control the radar operation, process the received data, and output the results.

[0010] Furthermore, the laser ranging module includes a laser emitter and a receiver; a lidar has multiple laser emitters arranged on the same emitting surface, the laser source being generated by a semiconductor laser with a wavelength of 905nm; and multiple receivers arranged on the same receiving surface;

[0011] The rotating module includes a rotating mechanism, a mounting base, and an encoder disk. The rotating module is driven by a motor, which is placed on the mounting base and drives the rotating mechanism through a rotating shaft. The laser ranging module is located above the rotating mechanism. An encoder disk is installed at the tail of the motor to detect the rotation angle of the laser emitter. The encoder disk transmits signals to the control unit.

[0012] The control module includes a control unit and a wireless module. The control unit is mounted on the FPGA development board and is used to control the motor drive and receive data transmitted by the laser ranging module. The wireless module is used for data transmission with the computer.

[0013] Furthermore, the mounting base has threaded holes at the bottom, and the telescopic bracket includes a triangular stabilizing bracket and a fixing platform. The fixing platform has a stud at its center that mates with the threaded holes of the mounting base.

[0014] A method for measuring the minimum turning diameter of a vehicle using the above-mentioned measurement system includes the following steps:

[0015] Step (1): Measure and calculate the minimum estimated turning diameter, which is the estimated circle;

[0016] Step (2): Determine the location of the lidar: Set up four lidars on the outer perimeter of the estimated circle. The line connecting the four lidars forms a rectangle, and the minimum turning diameter circle of the car is located inside the rectangle. Take one lidar as the origin, and take the two sides of the rectangle passing through that point as the x-axis and y-axis, respectively, to determine the coordinates of the four lidars (x1, y2), (x2, y2), (x3, y3), (x4, y4), where x1 = 0, y1 = 0;

[0017] Step (3): Adjust the lidar: Adjust the height of the lidar using the telescopic bracket so that the laser beam is at the same level as the lower edge of the outer side of the car tire;

[0018] Step (4): Turn on the central control unit, establish communication with the lidar, and input the tire width and the coordinate values ​​of the four lidars obtained in step (2);

[0019] Step (5): Put the car being measured in the lowest forward gear, then turn the steering wheel of the car clockwise to the limit position and keep it there. After stabilizing, drive the car at low speed for one revolution, then drive the car out of the measurement area and mark the position where the car drove out of the measurement area; turn the car around and enter the measurement area from the marked position, and drive counterclockwise in the same way. After the measurement is completed, drive the car out of the measurement area.

[0020] Step (6): During the measurement process in step (5), the lidar receiver receives the laser reflected back from the tire, processes it to obtain the distance from the point to the car tire, and the radar transmits the distance value to the data processing module of the central control unit in real time.

[0021] Step (7): The data processing module processes and obtains the minimum distance between the four radars and the car tires. Based on the four minimum values ​​and the initial coordinate values ​​of the four radars, the module calculates the minimum turning diameter of the car.

[0022] Further, step (1) specifically involves measuring the width H of the car tire;

[0023] The car under test is driven into the test area, the steering wheel is turned to its limit, and the car is driven in the lowest gear at a low speed for one revolution. After the revolution, the steering wheel is straightened and the engine is turned off. The approximate range of the minimum turning diameter circle of the car is determined, which is the estimated circle.

[0024] Further, step (7) specifically involves: within the time it takes for the car to turn once with the minimum turning diameter, the data processing module takes the minimum value of the radar transmission distance by comparing the size, and records the minimum values ​​corresponding to lidar I, lidar II, lidar III, and lidar N as a, b, c, and d, respectively.

[0025] Assuming the center of the car's minimum turning circle is (x0, y0) and the radius is r, the data processing module calculates the car's minimum turning diameter R by combining three minimum values ​​and the corresponding initial coordinate values ​​of the three radars. The formulas for calculating the minimum turning diameter R using LiDAR I, LiDAR II, and LiDAR III are as follows:

[0026] (x1-x0) 2 +(y1-y0) 2 =(a+r) 2

[0027] (x2-x0) 2 +(y2-y0) 2 =(b+r) 2

[0028] (x3-x0) 2 +(y3-y0) 2 =(c+r) 2

[0029] R = 2 × (rH).

[0030] Furthermore, the car starts driving from position radar I. When the car passes the positions of lidar I, lidar II, and lidar III, the data processing module calculates the diameter of the minimum turning diameter arc of the car corresponding to the three lidars.

[0031] After the data processing module obtains the minimum distance values ​​of radars II, III, and IV, it will recalculate to obtain the diameter of the minimum turning diameter arc of the car corresponding to the three radars.

[0032] After the car has completed a full circle, the data processing module recalculates based on the minimum distance values ​​of LiDAR III, IV, and I.

[0033] The system takes the maximum value from the three calculations as the minimum turning diameter of the car.

[0034] A method for measuring the minimum turning radius of a car using the above-mentioned measurement system includes the following steps:

[0035] Step (1): Measure and calculate the minimum estimated turning diameter, which is the estimated circle;

[0036] Step (2): Determine the location of the lidar: Set up four lidars on the outer perimeter of the estimated circle, and connect the four lidars to form a rectangle, so that the minimum turning diameter circle of the car is located inside the rectangle. Take one of the lidars as the origin, and take the two sides of the rectangle passing through that point as the x-axis and y-axis, respectively, to determine the coordinates of the four lidars (x1, y2), (x2, y2), (x3, y3), (x4, y4), where x1 = 0, y1 = 0; Place lidar V and lidar VI in the inner circle of the car turning channel, so that the angle between the radii of lidar V and lidar VI is 90°.

[0037] Step (3): Adjust the height of the lidar using the telescopic bracket so that the height of lidar I, lidar II, lidar III, and lidar IV is such that the rays illuminate the outermost point of the car body, and the height of lidar V and lidar VI is such that the rays illuminate the innermost point of the car body.

[0038] Step (4): Turn on the central control unit, establish communication with the lidar, and input the tire width and the coordinate values ​​of the six lidars obtained in step (2);

[0039] Step (5): Put the car being measured in the lowest forward gear, then turn the steering wheel of the car clockwise to the limit position and keep it there. After stabilizing, drive the car at low speed for one revolution, then drive the car out of the measurement area and mark the position where the car drove out of the measurement area; turn the car around and enter the measurement area from the marked position, and drive counterclockwise in the same way. After the measurement is completed, drive the car out of the measurement area.

[0040] Step (6): During the measurement process in step (5), the lidar receivers I to IV receive the laser reflected back from the outermost point of the car body, and after processing, the distance from that point to the outermost point of the car body is obtained. The lidar receivers V to VI receive the laser reflected back from the innermost point of the car body, and after processing, the distance from that point to the innermost point of the car body is obtained. The lidar transmits the distance value to the data processing module of the central control unit in real time.

[0041] Step (7): The data processing module processes the received data from LiDAR I, LiDAR II, LiDAR III, and LiDAR IV to calculate the outer diameter of the turning channel;

[0042] The data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel;

[0043] The outer diameter of the turning channel and the inner diameter of the turning channel form the minimum turning channel circle for a car. Half of the difference between the diameters of the two circles gives the maximum turning channel width for a car.

[0044] Furthermore, the specific method for "the data processing module processing the received data from LiDAR I, LiDAR II, LiDAR III, and LiDAR IV to calculate the outer diameter of the turning channel" in step (7) is as follows:

[0045] Within the time it takes for the car to make one turn with the minimum turning diameter, the data processing module takes the minimum value of the radar return distance by comparing the magnitudes. The minimum values ​​corresponding to lidar I, lidar II, lidar III, and lidar IV are denoted as a′, b′, c′, and d′, respectively.

[0046] Assuming the center of the minimum turning circle of the car is (x0, y0), and the outer radius of the minimum turning channel is r′, the data processing module calculates the outer diameter R′ of the minimum turning channel by combining the three minimum values ​​and the corresponding initial coordinate values ​​of the three radars. The formulas for calculating the outer diameter R′ of the minimum turning channel using LiDAR I, LiDAR II, and LiDAR III are as follows:

[0047] (x1-x0) 2 +(y1-y0) 2 =(a′+r′) 2

[0048] (x1-x0) 2 +(y1-y0) 2 = (b′+r′) 2

[0049] (x1-x0) 2 +(y1-y0) 2 =(c′+r′) 2

[0050] R′=2r′.

[0051] Furthermore, in step (7), "the data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel" specifically means: the data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel and take the average value.

[0052] Furthermore, the data processing module processes the data received by LiDAR V and LiDAR VI in the same way, as follows:

[0053] Step (71): The data processing module receives data Q1 at time T1 and saves Q1;

[0054] Step (72): Receive data Q2 at time T2. If Q2 > Q1, save Q2 and enter the program to find the maximum value. n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n >Q n-1 The system saves Q. n If Q n <Q n-1 The system saves Q. n-1 Let the maximum value be Q. n-1 The program for finding the maximum value ends;

[0055] If Q2 < Q1, the system saves Q1 and enters the program to find the minimum distance, at T n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n <Q n-1 The system saves Q. n If Q n >Q n-1 The system saves Q. n-1 Let the minimum value be Q. n-1 The program for finding the minimum value ends;

[0056] Step (73): After the program for finding the maximum value finishes, the system enters the program for finding the minimum value, at T n+1 Receive data Q at all times n+1 According to vehicle driving rules, Q n+1 <Q n The system saves Q. n In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m >Q n+m-1 The system saves Q. n+m-1 Let the minimum value be Q. n+m-1 The program for finding the minimum value ends;

[0057] After the minimum value finding program finishes, the system enters the maximum value finding program, at T n+1 Receive data Q at all times n+1 According to vehicle driving rules, Q n+1 >Q n The system saves Q. n+1 In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m <Q n+m-1 The system saves Q. n+m-1 Let the maximum value be Q. n+m-1 The program for finding the maximum value ends;

[0058] Step (74): Define the sum of the maximum and minimum values ​​as the inner diameter of the car turning channel and output it.

[0059] Compared with the prior art, the significant advantages of this invention are:

[0060] 1. The system uses the principle of lidar ranging to measure the minimum turning diameter of a car, and the test results are highly accurate. The system is highly modular and integrated.

[0061] 2. The system automates data acquisition and processing during operation, ensuring a safe and efficient measurement process;

[0062] 3. The system is less affected by environmental factors, requires fewer testing resources, and has high testing efficiency;

[0063] 4. The system is highly versatile and adaptable to different vehicle heights by adjusting the telescopic bracket. Attached Figure Description

[0064] Figure 1This is a schematic diagram of the minimum turning diameter measurement system for automobiles based on lidar according to the present invention;

[0065] Figure 2 This is a top view of the LiDAR-based vehicle minimum turning diameter measurement system of the present invention;

[0066] Figure 3 This is a top view of the LiDAR-based automotive minimum turning circle measurement system of the present invention;

[0067] Figure 4 This is a schematic diagram of the retractable support structure of the present invention;

[0068] Figure 5 This is a schematic diagram of the lidar structure of the present invention;

[0069] Figure 6 This is a schematic diagram illustrating the calculation of the minimum turning diameter of a car according to the present invention;

[0070] Figure 7 This is a schematic diagram illustrating the calculation of the minimum turning radius for automobiles according to the present invention.

[0071] Explanation of reference numerals in the attached figures:

[0072] 1-LiDAR I, 2-LiDAR II, 3-LiDAR III, 4-LiDAR IV, 5-Vehicle under test, 6-Laser, 7-Extendable bracket, 8-Minimum turning diameter circle of the vehicle, 9-Inner circle of the minimum turning channel of the vehicle, 10-Triangular stabilizer bracket, 11-Fixing platform, 12-Screw, 13-Mounting base, 14-LiDAR V, 15-LiDAR VI, 16-Outer circle of the minimum turning channel of the vehicle. Detailed Implementation

[0073] The present invention will now be described in further detail with reference to the accompanying drawings.

[0074] The minimum turning diameter measurement system for automobiles in this embodiment includes a lidar, a retractable bracket 7, and a computer. The bottom of the lidar is fixed to the retractable bracket 7. By adjusting the height of the retractable bracket, the lidar can illuminate the upper edge of the automobile tire. The four retractable brackets are placed on the ground, and the rectangle formed can surround the minimum turning circle of the automobile.

[0075] Furthermore, the lidar includes a laser ranging module, a rotation module, and a control module.

[0076] A laser ranging module includes a laser transmitter and receivers. A single lidar unit contains multiple laser transmitters arranged on the same emitting surface. The laser source is generated by a semiconductor laser with a wavelength of 905nm. Each laser transmitter contains multiple receivers arranged on the same receiving surface to receive the laser light reflected back from the target object. The receivers use the direct time-of-flight (dToF) method to calculate the time from laser emission to reception to obtain the distance to the target location.

[0077] The rotating module includes a rotating mechanism, a mounting base, and an encoder disk. The rotating module is driven by a motor; the reduction ratio and maximum speed are selected according to measurement requirements. The motor is placed on the mounting base and drives the rotating mechanism via a rotating shaft. The laser ranging module is located above the rotating mechanism. An encoder disk is mounted at the rear of the motor to detect the rotation angle of the laser emitter. The encoder disk transmits signals to the control unit.

[0078] The control module includes a control unit and a wireless module. The control unit is mounted on the FPGA development board and is used to control the motor drive and receive data transmitted by the laser ranging module. The wireless module is used for data transmission with the computer.

[0079] Specifically, the mounting base is located below the rotating mechanism and is used to support and fix the motor. The bottom of the mounting base has threads and can be connected to the telescopic bracket by screws.

[0080] The telescopic support consists of a triangular stabilizing bracket and a fixed platform. The height of the platform can be adjusted by opening and closing the triangular stabilizing bracket, and the base is fixed to the center of the fixed platform with screws.

[0081] Specifically, the circuitry of a lidar system mainly consists of a stator PCB and a rotor PCB. The stator PCB is responsible for powering the rotation and control modules, and mainly comprises a motor drive circuit, a power supply circuit, and an FPGA interface circuit. An external 12V power supply is input to the power circuit through a DC connector, and the motor drive voltage is 12V. The rotor PCB is responsible for powering the laser ranging module, which has a 5V power supply voltage, transmitted from the stator PCB to the rotor PCB via conductive slip rings.

[0082] Specifically, the stator PCB communicates with the FPGA development board via ribbon cables.

[0083] The computer is equipped with a main control system and a front-end display interface, including a radar control module and a data processing module. The radar control module communicates with the lidar via WiFi, and the data processing module receives data transmitted by the radar via WiFi. It has an embedded data processing algorithm to process the received data and output the results. The WiFi at the test site is generated by a wireless router.

[0084] The method for measuring the minimum turning diameter of a car in this embodiment includes the following steps:

[0085] Step 1: Drive the car to be tested into the test area, turn the steering wheel to the limit, use the lowest gear and drive at low speed for one revolution to determine the approximate range of the minimum turning diameter circle of the car, turn off the car and stop in place, return the steering wheel to the normal position, and use a tape measure to measure the width of the car tires.

[0086] Step 2: Based on the approximate range of the estimated minimum turning diameter circle, place four retractable brackets around the estimated circle and fix the LiDARs to the retractable brackets. The lines connecting the coordinates of the four LiDARs should form a rectangle. Assign the LiDAR in the northwest corner as LiDAR 1, and the remaining LiDARs as LiDAR 2, 3, and 4 in a clockwise direction. The lines connecting the coordinates of LiDAR 1 and LiDAR 2 should run east-west, and the lines connecting the coordinates of LiDAR 1 and LiDAR 4 should run north-south. Use a measuring tape to measure the distance between adjacent LiDARs to ensure that the minimum turning diameter circle of the vehicle is within the rectangle.

[0087] Step 3: After fixing the position of the telescopic bracket, turn on the lidar and adjust the height of the telescopic bracket so that the laser beam is at the same level as the lower edge of the outer side of the car tire.

[0088] Step 4: After confirming that the radar is working properly, turn on the computer and open the main control system. Communicate with the four lidars via wireless network. Once communication is successful, input the distances of the four radars measured with a measuring tape into the main control system in coordinate form. The coordinates of radar 1 are (0, 0), radar 2 are (X2, Y2), radar 3 are (X3, Y3), and radar 4 are (X4, Y4). The positions of these four radars were measured in Step 2. Assume the center of the minimum turning circle of the car is (X0, Y0), and the radius of the circle is r. Simultaneously, input the tire width H into the system.

[0089] Step 5: After confirming that the system is in normal condition, put the test vehicle in the lowest forward gear and drive at a low speed according to the method of GB / T 12540-2009. Then turn the steering wheel of the vehicle clockwise to the limit and keep it there. After stabilizing, drive the vehicle one revolution. Then drive the vehicle out of the measurement area and mark the position where the vehicle left the measurement area. Turn the vehicle around and enter the measurement area from the marked position. Drive counterclockwise in the same way. After the measurement is completed, drive the vehicle out of the measurement area.

[0090] Step 6: During the measurement process, the receiver receives the laser reflected back from the tire, processes it to obtain the distance from the point where the lidar is located to the car tire, and the radar's wireless module transmits the distance value to the data processing module of the main control system in real time.

[0091] Step 7: Within the time it takes for the car to make one complete turn with the minimum turning diameter, the data processing module calculates the minimum radar return distance by comparing the values. Let the minimum values ​​for lidars 1, 2, 3, and 4 be a, b, c, and d, respectively. The data processing module combines these three minimum values ​​with the corresponding initial coordinates of the three lidars to calculate the car's minimum turning diameter R. Taking lidars 1, 2, and 3 as an example, the calculation formula is as follows:

[0092] (x1-x0) 2 +(y1-y0) 2 =(a+r) 2

[0093] (x2-x0) 2 +(y2-y0) 2 =(b+r) 2

[0094] (x3-x0) 2 +(y3-y0) 2 =(c+r) 2

[0095] R = 2 × (rH)

[0096] It is important to note that the formula only requires three points to calculate the minimum turning diameter of a car. Assuming the car starts from position 1, as the car passes positions 1, 2, and 3, the data processing module can calculate the diameter of the minimum turning diameter arc corresponding to positions 1, 2, and 3. Considering the influence of tire deformation and ground friction when the car turns with the minimum turning diameter, the center and diameter will change slightly. To ensure the accuracy of the system measurement and the integrity of the data acquisition, the data processing module will recalculate after obtaining the minimum distance values ​​of positions 2, 3, and 4 to obtain the diameter of the minimum turning diameter arc corresponding to positions 2, 3, and 4. After the car has completed one full circle, the data processing module will recalculate based on the minimum distance values ​​of positions 3, 4, and 1. The system takes the maximum value of the three calculations as the minimum turning diameter of the car.

[0097] The advantages of this invention are: 1. The system uses the laser radar ranging principle to measure the minimum turning diameter of a car, resulting in high accuracy and a high degree of modularity and integration; 2. The system's data acquisition and processing are automated during operation, ensuring a safe and efficient measurement process; 3. The system is less affected by environmental factors, requires fewer testing resources, and has high testing efficiency; 4. The system can adapt to different vehicle heights by adjusting the telescopic bracket, resulting in a high degree of versatility.

[0098] It should be noted that this system is applicable to automobiles and automobile trains, and can be used to measure the minimum turning diameter and minimum turning circle.

[0099] When measuring the minimum turning circle of a car, LiDARs 14 and 15 need to be placed inside the turning circle. LiDARs 1, 2, 3, and 4 are adjusted in height via a telescopic bracket. The height of LiDARs 1, 2, 3, and 4 is such that they can illuminate the outermost point of the car body (the point whose projection on the flat ground is outside the turning circle, excluding the rearview mirror, lower mirror, and antenna). The height of LiDARs 14 and 15 is such that they can illuminate the innermost point of the car body (the point whose projection on the flat ground is outside the inner circle of the turning circle, excluding the rearview mirror, lower mirror, and antenna). The working principle of LiDARs 14 and 15 is the same as that of LiDARs 1, 2, 3, and 4.

[0100] Specifically, the data processing module handles the data from lidars 14 and 15 differently than lidars 1, 2, 3, and 4. Taking lidar 14 as an example, the data processing flow of the data module is as follows:

[0101] Step (71): The data processing module receives data Q1 at time T1 and saves Q1;

[0102] Step (72): Receive data Q2 at time T2. If Q2 > Q1, save Q2 and enter the program to find the maximum value. n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n >Q n-1 The system saves Q. n If Q n <Q n-1 The system saves Q. n-1 Let the maximum value be Q. n-1 The program for finding the maximum value ends;

[0103] If Q2 < Q1, the system saves Q1 and enters the program to find the minimum distance, at T n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n <Q n-1 The system saves Q. n If Q n >Q n-1 The system saves Q. n-1 Let the minimum value be Q. n-1 The program for finding the minimum value ends;

[0104] Step (73): After the program for finding the maximum value finishes, the system enters the program for finding the minimum value, at T n+1 Receive data Q at all times n+1 According to vehicle driving rules, Qn+1 <Q n The system saves Q. n In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m >Q n+m-1 The system saves Q. n+m-1 Let the minimum value be Q. n+m-1 The program for finding the minimum value ends;

[0105] After the minimum value finding program finishes, the system enters the maximum value finding program, at T n+1 Receive data Q at all times n+1 According to vehicle driving rules, Q n+1 >Q n The system saves Q. n+1 In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m <Q n+m-1 The system saves Q. n+m-1 Let the maximum value be Q. n+m-1 The program for finding the maximum value ends;

[0106] Step (74): Define the sum of the maximum and minimum values ​​as the inner diameter of the car turning channel and output it.

Claims

1. A system for measuring the minimum turning diameter and minimum turning lane circle of a car, characterized in that, Includes multiple lidar units, a retractable bracket for mounting and adjusting the height of the lidar units, and a central control unit; The lidar includes a laser ranging module for measuring the target position, a rotation module for driving the laser ranging module to rotate, and a control module; The laser ranging module is driven by a motor with an encoder disk mounted on the rotating module. The control module is used to control the motor drive and receive data from the laser ranging module. The control module and the central control unit are connected wirelessly. The central control unit is used to control the radar operation, process the received data, and output the results; Four lidar sensors, I to IV, are placed on the outer perimeter of the estimated circle. The line connecting the four lidar sensors I to IV forms a rectangle, and the minimum turning diameter circle of the car is located within the rectangle. Taking one of the lidar sensors as the origin, the coordinates of the four lidar sensors (x1, y2), (x2, y2), (x3, y3), and (x4, y4) are determined by the two sides of the rectangle passing through that point as the x-axis and y-axis, respectively, where x1=0 and y1=0. Lidar sensors V and VI are placed in the inner circle of the car turning channel, such that the angle between the radii of lidar sensors V and VI is 90°. When measuring the minimum turning diameter of a car, the lidar receivers I to IV receive the laser reflected back from the tires, and after processing, obtain the distance from that point to the car tires; When measuring the minimum turning radius of a car, LiDAR receivers I to IV receive the laser reflected from the outermost point of the car body, and after processing, obtain the distance from that point to the outermost point of the car body. LiDAR receivers V to VI receive the laser reflected from the innermost point of the car body, and after processing, obtain the distance from that point to the innermost point of the car body.

2. The measurement system according to claim 1, characterized in that, The laser ranging module includes a laser transmitter and a receiver; a lidar has multiple laser transmitters arranged on the same emitting surface, the laser source is generated by a semiconductor laser with a wavelength of 905nm; and multiple receivers arranged on the same receiving surface. The rotating module includes a rotating mechanism, a mounting base, and an encoder disk. The rotating module is driven by a motor, which is placed on the mounting base and drives the rotating mechanism through a rotating shaft. The laser ranging module is located above the rotating mechanism. An encoder disk is installed at the tail of the motor to detect the rotation angle of the laser emitter. The encoder disk transmits signals to the control unit. The control module includes a control unit and a wireless module. The control unit is mounted on the FPGA development board and is used to control the motor drive and receive data transmitted by the laser ranging module. The wireless module is used for data transmission with the computer.

3. The measurement system according to claim 2, characterized in that, The mounting base has threaded holes at the bottom. The telescopic bracket includes a triangular stabilizing bracket and a fixing platform. The fixing platform has a stud at the center that mates with the threaded holes of the mounting base.

4. A method for measuring the minimum turning diameter of a vehicle using the measurement system according to any one of claims 1-3, characterized in that, Includes the following steps: Step (1): Measure and calculate the minimum estimated turning diameter, which is the estimated circle; Step (2): Determine the location of the lidar; Step (3): Adjust the lidar: Adjust the height of the lidar using the telescopic bracket so that the laser beam is at the same level as the lower edge of the outer side of the car tire. Step (4): Turn on the central control unit, establish communication with the lidar, and input the tire width and the coordinate values ​​of the four lidars obtained in step (2); Step (5): Put the car being measured in the lowest forward gear, then turn the steering wheel of the car clockwise to the limit position and keep it there. After stabilizing, drive the car at low speed for one revolution, then drive the car out of the measurement area and mark the position where the car drove out of the measurement area; turn the car around and enter the measurement area from the marked position, and drive counterclockwise in the same way. After the measurement is completed, drive the car out of the measurement area. Step (6): During the measurement process in step (5), the lidar receivers I to IV receive the laser reflected back from the tire, and after processing, the distance from the point to the car tire is obtained. The lidar transmits the distance value to the data processing module of the central control unit in real time. Step (7): The data processing module processes and obtains the minimum distance between the four radars and the car tires. Based on the four minimum values ​​and the initial coordinate values ​​of the four radars, the module calculates the minimum turning diameter of the car.

5. The method according to claim 4, characterized in that, Step (1) specifically involves measuring the width H of the car tire; The car under test is driven into the test area, the steering wheel is turned to its limit, and the car is driven in the lowest gear at a low speed for one revolution. After the revolution, the steering wheel is straightened and the engine is turned off. The approximate range of the minimum turning diameter circle of the car is determined, which is the estimated circle.

6. The method according to claim 5, characterized in that, Step (7) is as follows: within the time it takes for the car to turn once with the minimum turning diameter, the data processing module takes the minimum value of the radar return distance by comparing the size. The minimum values ​​corresponding to lidar I, lidar II, lidar III, and lidar IV are a, b, c, and d, respectively. Assuming the center of the car's minimum turning circle is (x0, y0) and the radius is r, the data processing module calculates the car's minimum turning diameter R by combining three minimum values ​​and the corresponding initial coordinate values ​​of the three radars. The formulas for calculating the minimum turning diameter R using LiDAR I, LiDAR II, and LiDAR III are as follows: ， ， ， 。 7. The method according to claim 6, characterized in that, The car starts moving from position radar I. When the car passes the positions of lidar I, lidar II, and lidar III, the data processing module calculates the diameter of the minimum turning diameter arc corresponding to the three lidars. After the data processing module obtains the minimum distance values ​​of radars II, III, and IV, it will recalculate to obtain the diameter of the minimum turning diameter arc of the car corresponding to the three radars. After the car has completed one full lap, the data processing module recalculates based on the minimum distance values ​​of LiDAR III, IV, and I. The system takes the maximum value from the three calculations as the minimum turning diameter of the car.

8. A method for measuring the minimum turning circle of a vehicle using the measurement system according to any one of claims 1-3, characterized in that, Includes the following steps: Step (1): Measure and calculate the minimum estimated turning diameter, which is the estimated circle; Step (2): Determine the location of the lidar; Step (3): Adjust the height of the lidar using the telescopic bracket so that the height of lidar I, lidar II, lidar III, and lidar IV is such that the rays illuminate the outermost point of the car body, and the height of lidar V and lidar VI is such that the rays illuminate the innermost point of the car body. Step (4): Turn on the central control unit, establish communication with the lidar, and input the tire width and the coordinate values ​​of the six lidars obtained in step (2); Step (5): Put the car being measured in the lowest forward gear, then turn the steering wheel of the car clockwise to the limit position and keep it there. After stabilizing, drive the car at low speed for one revolution, then drive the car out of the measurement area and mark the position where the car drove out of the measurement area; turn the car around and enter the measurement area from the marked position, and drive counterclockwise in the same way. After the measurement is completed, drive the car out of the measurement area. Step (6): During the measurement process in step (5), the lidar receivers I to IV receive the laser reflected back from the outermost point of the car body, and after processing, the distance from that point to the outermost point of the car body is obtained. The lidar receivers V to VI receive the laser reflected back from the innermost point of the car body, and after processing, the distance from that point to the innermost point of the car body is obtained. The lidar transmits the distance value to the data processing module of the central control unit in real time. Step (7): The data processing module processes the received data from LiDAR I, LiDAR II, LiDAR III, and LiDAR IV to calculate the outer diameter of the turning channel; The data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel; The outer diameter of the turning channel and the inner diameter of the turning channel form the minimum turning channel circle for a car. Half of the difference between the diameters of the two circles gives the maximum turning channel width for a car.

9. The method according to claim 8, characterized in that, The specific method for "the data processing module processes the received data from LiDAR I, LiDAR II, LiDAR III, and LiDAR IV to calculate the outer diameter of the turning channel" in step (7) is as follows: Within the time it takes for the car to make one complete turn with the minimum turning diameter, the data processing module determines the minimum radar return distance by comparing the values. The minimum values ​​for LiDAR I, LiDAR II, LiDAR III, and LiDAR IV are denoted as follows: , , , ; Assume the center of the minimum turning circle for the car is (x0, y0), and the radius of the outer circle of the minimum turning channel for the car is... The data processing module combines the three minimum values ​​and the corresponding three radar initial coordinate values ​​to calculate the minimum outer diameter of the car's turning channel. Calculate the minimum outer diameter of the turning channel using LiDAR I, LiDAR II, and LiDAR III. The formula is as follows: ， ， ， 。 10. The method according to claim 9, characterized in that, In step (7), "the data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel" specifically means: the data processing module processes the data received by LiDAR V and LiDAR VI to calculate the inner diameter of the car turning channel and take the average value; the process of processing the data received by LiDAR V and LiDAR VI is the same, and the specific process is as follows: Step (71): The data processing module receives data Q1 at time T1 and saves Q1; Step (72): Receive data Q2 at time T2. If Q2 > Q1, save Q2 and enter the program to find the maximum value. n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n >Q n-1 The system saves Q. n If Q n <Q n-1 The system saves Q. n-1 Let the maximum value be Q. n-1 The program for finding the maximum value ends; If Q2 < Q1, the system saves Q1 and enters the program to find the minimum distance, at T n-1 Receive data Q at all times n-1 In T n Receive data Q at all times n If Q n <Q n-1 The system saves Q. n If Q n >Q n-1 The system saves Q. n-1 Let the minimum value be Q. n-1 The program for finding the minimum value ends; Step (73): After the program for finding the maximum value finishes, the system enters the program for finding the minimum value, at T n+1 Receive data Q at all times n+1 According to vehicle driving rules, Q n+1 <Q n The system saves Q. n In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m >Q n+m-1 The system saves Q. n+m-1 Let the minimum value be Q. n+m-1 The program for finding the minimum value ends; After the minimum value finding program finishes, the system enters the maximum value finding program, at T. n+1 Receive data Q at all times n+1 According to vehicle driving rules, Q n+1 >Q n The system saves Q. n+1 In T n+m-1 Receive data Q at all times n+m-1 In T n+m Receive data Q at all times n+m If Q n+m <Q n+m-1 The system saves Q. n+m-1 Let the maximum value be Q. n+m-1 The program for finding the maximum value ends; Step (74): Define the sum of the maximum and minimum values ​​as the inner diameter of the car turning channel and output it.

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