A dynamic electrical performance test bench for automobile braking system

Abstract

The present invention proposes a test bench for dynamic electrical performance of automobile brake system, including a software system and a hardware system, wherein the hardware system includes a wheel speed simulation component, a braking force measurement component and a measurement and control component, wherein the wheel speed simulation component and the braking force measurement component are both connected to the actual vehicle to be tested, and the wheel speed simulation component and the braking force measurement component are both connected to the measurement and control component, and the software system is arranged in the measurement and control component. The present invention can comprehensively test the dynamic electrical performance of automobile brake system in the laboratory, and is safe, reliable and efficient, and solves the technical problems of difficult and high cost of dynamic electrical performance testing. At the same time, the present invention has strong versatility, and improves the reliability and authenticity of the test results of dynamic electrical performance of automobile brake system. The present invention can arbitrarily select the existing typical cycle driving conditions or customize them according to the needs of test evaluation during testing, and has strong flexibility, and ensures the typicality, representativeness and extensibility of the test conditions.

Description

Technical Field

[0001] The invention relates to the technical field of automobile testing, and in particular to a dynamic electrical performance testing bench for an automobile braking system. Background Art

[0002] The electrical system is the blood vessels and nerves of the car, and is related to the reliability of the entire vehicle. In particular, the braking system is related to driving safety. The Antilock Brake System (ABS) has become popular, and its reliability directly affects the safety of the car during emergency braking. In the process of new car development, especially in the prototype trial production stage, comprehensive testing and evaluation of its electrical performance, especially dynamic electrical performance, is an important part of automobile development.

[0003] The driving conditions of automobiles are extremely complex during use. In order to fully test and evaluate the electrical performance of the automobile braking system, it is usually necessary to build a test track that occupies a huge area and is very expensive. In addition, there are many potential safety hazards in the development stage of new cars, and direct road tests are very risky. In the laboratory, the static electrical performance of the braking system can only be tested through simple braking operations when the car is stationary, and the dynamic electrical performance of the braking system cannot be fully evaluated.

[0004] For example, the application number CN111649958A discloses a bench used for automobile brake system performance testing, including a base, a motor is fixedly installed on one side of the top of the base, one side of the motor is fixedly connected to the middle of one side of the silent industrial dust collector, the other side of the motor is fixedly connected to the middle of one side of the electrical cabinet, and the other side of the electrical cabinet is fixedly connected to one side of the control cabinet. The invention installs the motor, the clutch device, the tooling equipment, the torque test device, the environmental test chamber, etc. on the base, and the electrical components (PLC controller, inverter, etc.) are installed in the electrical cabinet. The control cabinet is equipped with a control computer, and the control computer is programmed using LabVIEW, so that the device has the function of multiple project testing, which can not only be used for brake detection but also for brake pads and brake discs, solving the waste of resources and property caused by excessive equipment investment, and at the same time, the equipment utilization rate is higher and the operation of personnel is more convenient. However, the bench mainly drives the brake disc to rotate by the motor to simulate the movement of the car. In the high-speed performance test, only the temperature and the grinding of the brake pads and brake discs during the braking process of the car are detected, and the dynamic electrical performance of the automobile braking system is not fully evaluated. Summary of the invention

[0005] In view of the technical problems that the existing performance test benches cannot comprehensively evaluate the dynamic electrical performance of the braking system and the testing process is costly, the present invention proposes a dynamic electrical performance test bench for an automobile braking system, which improves the reliability and safety of the dynamic electrical performance of the automobile braking system, solves the technical problems of the difficulty and high cost of dynamic electrical performance testing, and improves the testing efficiency.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is implemented as follows: a dynamic electrical performance test bench for automobile braking system, including a wheel speed simulation component, a braking force measuring component and a measurement and control component, the wheel speed simulation component and the braking force measuring component are both connected to the actual vehicle to be tested, the wheel speed simulation component is connected to the wheel speed sensor of the actual vehicle to be tested, the braking force measuring component is matched with the brake caliper housing of the actual vehicle to be tested, and the wheel speed simulation component and the braking force measuring component are both connected to the measurement and control component.

[0007] The wheel speed simulation component includes a speed measuring ring gear and a control motor. The speed measuring ring gear is fixedly connected to the output shaft of the control motor. The control motor is connected to a motor drive controller. The motor drive controller is connected to the measurement and control component. The speed measuring ring gear is connected to the wheel speed sensor of the actual vehicle to be tested.

[0008] The braking force testing component includes a conditioner, a force sensor, an adjusting block and a feeler gauge. The force sensor is connected to the conditioner, and the conditioner is connected to the measurement and control component. The adjusting block is arranged on the top of the bellows, and the force sensor is arranged inside the bellows. The bottom of the force sensor and the bellows are both arranged on the top of the base. The feeler gauge is movably arranged between the adjusting block and the brake caliper piston. A shim group is arranged at the bottom of the base. The adjusting block is arranged on the lower side of the brake caliper piston of the actual vehicle to be tested, and the shim group is arranged on the lower side of the inside of the brake caliper housing of the actual vehicle to be tested.

[0009] The gasket set includes at least two gaskets which are arranged up and down and have different thicknesses.

[0010] The feeler gauge comprises a large feeler gauge and a small feeler gauge, and the large feeler gauge and the small feeler gauge have different thicknesses.

[0011] A hemispherical notch is arranged at the bottom center of the regulating block, a ball head of the force sensor is arranged in the hemispherical notch, and the bellows is arranged coaxially with the force sensor.

[0012] The measurement and control component comprises a computer and a data acquisition controller. The computer, the motor drive controller and the conditioner are all connected to the data acquisition controller, and the data acquisition controller is connected to the computer.

[0013] Step S1: remove the brake caliper of the actual vehicle to be tested and disassemble the friction plate;

[0014] Step S2: selecting a shim assembly from the shim set according to the size of the brake caliper housing and placing the shim assembly at the bottom of the base;

[0015] Step S3: placing the force sensor, the gasket set, and the adjustment block in order from bottom to top inside the brake caliper housing of the actual vehicle to be tested, with the end surface of the brake caliper piston parallel to the upper plane of the adjustment block;

[0016] Step S4: starting the actual vehicle to be tested, and having the driver perform a braking operation, obtaining the vehicle braking force through the force sensor, and transmitting the vehicle braking force to the computer through the data acquisition controller;

[0017] Step S5: The computer calculates the wheel speed in real time according to the braking force of the vehicle, adjusts and controls the motor through the data acquisition controller and the motor drive controller to control the speed of the speed measuring ring gear, and uses the wheel speed sensor to measure the speed of the speed measuring ring gear in real time.

[0018] In step S2, two conditions must be met when selecting shims from the shim group: condition T1: the number of shims is minimum; condition T2: the gap between the adjustment block and the brake caliper piston meets the gap condition; the gap condition is: the small feeler gauge can pass through the gap, and the large feeler gauge cannot pass through the gap.

[0019] In step S5, the method for the computer to calculate the wheel speed in real time according to the braking force of the vehicle is: assuming that the number of teeth of the speed measuring ring gear is Z 1. The number of teeth on the speed ring of the actual vehicle to be tested is Z 2. The wheel speed is N 2, then the speed of the speed ring gear is N 1Should meet:

[0020] Z 1 N 1= Z 2 N 2,

[0021] The speed of the speed measuring ring gear is:

[0022] N 1= Z 2 N 2 / Z 1.

[0023] The beneficial effects of the present invention are:

[0024] (1) The automotive brake system dynamic electrical performance test bench provided by the present invention can comprehensively test the dynamic electrical performance of the automotive brake system in the laboratory. It is safe, reliable and efficient, and solves the technical problems of difficult and high cost in dynamic electrical performance testing.

[0025] (2) The automotive brake system dynamic electrical performance test bench provided by the present invention has strong versatility and does not need to consider the differences and similarities between different vehicle controllers and brake system control systems, thus effectively avoiding the black box problem of a large number of subsystems of the actual vehicle to be tested;

[0026] (3) The dynamic electrical performance test bench for the automobile braking system provided by the present invention directly uses the speed sensor of the actual vehicle to be tested to measure the ABS speed, and converts the braking pressure originally applied to the brake disc into the braking force measurement component provided by the present invention, combining virtual and real to ensure the reliability and authenticity of the test results;

[0027] (4) The vehicle brake system dynamic electrical performance test bench provided by the present invention can arbitrarily select existing typical cycle driving conditions or customize the operating conditions of the actual vehicle to be tested according to the needs of test evaluation, which has strong flexibility and ensures the typicality, representativeness and expandability of the test conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a principle block diagram of the present invention.

[0030] Figure 2 It is a schematic diagram of the structure of the present invention.

[0031] In the figure, 1 is a wheel speed simulation component, 2 is a braking force measuring component, 3 is a measurement and control component, 4 is a real vehicle to be tested, 11 is a speed measuring ring gear, 12 is a control motor, 13 is a motor drive controller, 21 is a conditioner, 22 is a force sensor, 23 is a gasket set, 24 is an adjustment block, 25 is a feeler gauge, 26 is a bellows, 27 is a base, 251 is a large feeler gauge, 252 is a small feeler gauge, 31 is a computer, 32 is a data acquisition controller, 41 is a brake caliper housing, 42 is a brake caliper piston, 43 is an oil pipe, and 44 is a wheel speed sensor. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, a dynamic electrical performance test bench for automobile brake system includes a wheel speed simulation component 1, a braking force measuring component 2 and a measurement and control component 3. The wheel speed simulation component 1 and the braking force measuring component 2 are both connected to a real vehicle 4 to be tested. The wheel speed simulation component 1 is connected to a wheel speed sensor 44 of the real vehicle 4 to be tested. The braking force measuring component 2 matches the brake caliper housing 41 of the real vehicle 4 to be tested. The wheel speed simulation component 1 and the braking force measuring component 2 are both connected to the measurement and control component 3. The main function of the software system A is to process the data collected by the wheel speed simulation component 1 and the braking force measuring component 2, calculate the vehicle wheel speed in real time, and adjust the simulated wheel speed in the wheel speed simulation component 1 in real time through the measurement and control component 3 to test the dynamic braking performance of the vehicle.

[0034] Among them, the wheel speed simulation component 1 includes a speed ring gear 11, a control motor 12 and a motor drive controller 13. The speed ring gear 11 is fixedly connected to the output shaft of the control motor 12, the control motor 12 is connected to the motor drive controller 13, the motor drive controller 13 is connected to the measurement and control component 3, and the speed ring gear 11 is connected to the wheel speed sensor 44. The speed ring gear 11 is simulated and equivalent to the speed ring gear of the car, and the speed ring gear 11 has a fixed number of teeth. The main function of the control motor 12 is to drive the speed ring gear 11 to rotate under the action of the motor drive controller 13, and the main function of the motor drive controller 13 is to drive the control motor 12 according to the command of the computer 31. The present invention uses the rotation tooth number equivalence method to simulate the equivalent speed ring gear of the car. Assume that the number of teeth of the speed ring gear 11 is Z 1. The number of teeth on the speed ring of the actual vehicle 4 to be tested is Z 2. The wheel speed is N 2, then the speed of the speed ring gear 11 is N 1Should meet:

[0035] Z 1 N 1= Z 2 N 2,

[0036] Then the speed of the speed measuring ring gear 11 is:

[0037] N 1= Z 2 N 2 / Z 1.

[0038] During the test, the tester calls the motor drive controller 13 through the computer 31 to drive the motor 12, so that the test gear ring 11 rotates at a set speed, thereby stimulating the required speed signal in the wheel speed sensor 44 of the actual vehicle 4 to be tested, and inputting it to the ABS system of the actual vehicle 4 to be tested, so that the ABS system works, thereby measuring the electrical performance of the ABS system. The wheel speed sensor 44 of the ABS is divided into Hall type and magnetic resistance type, the difference is that the magnetic characteristics of the speed measuring gear ring 11 are different; in the specific use process, it is only necessary to replace the corresponding speed measuring gear ring 11 according to the type of wheel speed sensor 44.

[0039] The braking force test component 2 includes a conditioner 21, a force sensor 22, an adjustment block 24 and a feeler gauge 25. The force sensor 22 is connected to the conditioner 21, and the conditioner 21 is connected to the measurement and control component 3. The adjustment block 24 is arranged on the top of the bellows 26, and the force sensor 22 is arranged inside the bellows 26. The bottoms of the force sensor 22 and the bellows 26 are both arranged on the top of the base 27. The feeler gauge 25 is movably arranged between the adjustment block 24 and the brake caliper piston 42. A shim group 23 is arranged at the bottom of the base 27. The adjustment block 24 is arranged on the lower side of the brake caliper piston 42 of the actual vehicle 4 to be tested, and the shim group 23 is arranged on the lower side of the brake caliper housing 41 of the actual vehicle 4 to be tested. The main function of the conditioner 21 is to collect the braking test data collected by the force sensor 22 and transmit the braking test data to the data acquisition controller 32. The shim set 23 includes at least two shims of different thicknesses. During the test, one or more shims need to be selected from the shim set according to the size of the brake caliper housing 41 and placed under the base 27. The shim set 23 includes at least one shim with a working size of 0.05 mm. The main function of the adjustment block 24 is that a hemispherical notch is provided at the bottom center of the adjustment block 24, and the ball head of the force sensor 22 is provided in the hemispherical notch. There is a gap between the lower side of the adjustment block 24 and the upper surface of the force sensor 22. The bellows 26 is coaxially arranged with the force sensor 22, and a hole is provided on the bellows 26. The force sensor 22 is connected to the regulator 21 through the hole. The main function of the feeler gauge 25 is to measure the gap distance between the adjustment block 24 and the brake caliper piston 42. The feeler gauge 25 includes a large feeler gauge 251 and a small feeler gauge 252. The thickness of the large feeler gauge 251 is 0.15 mm, and the thickness of the small feeler gauge 252 is 0.05 mm. The bellows 26 is elastic and is mainly used to support the adjusting block 24 and buffer the impact of the adjusting block 24 on the ball head of the force sensor 22 during the test. When the car is not in the braking state, there is usually a gap of 0.05-0.15mm between the friction pad and the brake disc. When braking, the friction pad is squeezed against the brake disc under the push of the brake caliper piston 42. Before the test, the gap between the force sensor 22 and the adjusting block 24 is 0.05-0.15mm by selecting a suitable shim from the shim group 23, and the gap is detected by the feeler gauge 25. When the gap between the force sensor 22 and the adjusting block 24 can pass the small feeler gauge 252, but cannot pass the large feeler gauge 251, the gap is qualified and the next test can be carried out. During the test, the brake caliper piston 42 pushes the adjustment block 24 to squeeze the force sensor 22. The force sensor 22 collects the force data, which is the braking pressure of the brake caliper on the brake disc during the braking process, and transmits the received data to the conditioner 21 for further processing. The conditioner 21 transmits the processed data to the data acquisition controller 32, and sends the data to the computer 31 for processing. The braking pressure is multiplied by the friction coefficient to obtain the braking force, which can be used to dynamically calculate the wheel speed in combination with parameters such as the braking radius.

[0040] The measurement and control component 3 includes a computer 31 and a data acquisition controller 32. The computer 31, the motor drive controller 13 and the conditioner 21 are all connected to the data acquisition controller 32. The software system A is set in the computer 31. The computer 31 is mainly used to analyze the force data collected by the force sensor 22. According to the parameters such as the mass and equivalent wind resistance of the car, the longitudinal dynamic equation of the car is used to calculate the rotation speed of the wheel. The data acquisition controller 32 is mainly used to collect the force data transmitted by the force sensor 22, and at the same time, according to the wheel speed calculated by the computer 31, the motor drive controller 13 is controlled to adjust the rotation speed of the speed measuring gear ring 11. This test bench can comprehensively test the dynamic electrical performance of the automobile braking system in the laboratory. It is safe, reliable and efficient. It solves the technical problems of difficult and high cost of dynamic electrical performance testing. At the same time, this test bench has strong versatility and does not need to consider the differences and similarities between different automobile controllers and brake system control systems, effectively avoiding the black box problem of a large number of subsystems of the actual vehicle to be tested.

[0041] The testing method of the present invention is as follows: Step S1: removing the brake caliper of the actual vehicle 4 to be tested and disassembling the friction plate.

[0042] Step S2: According to the size of the brake caliper housing 41, a shim assembly is selected from the shim set 23 and placed at the bottom of the base 27, so that the gap between the adjustment block 24 and the force sensor 22 is consistent with the gap between the automobile brake disc and the friction pad. When selecting shims from the shim set 23, two conditions must be met: 1. The gap between the adjustment block 24 and the force sensor 22 should be large enough for the small feeler gauge 252 to pass through, but not the large feeler gauge 251; 2. The number of shims used should be minimized.

[0043] Step S3: The force sensor 22, the shim set 23, and the adjustment block 24 are placed inside the brake caliper housing 41, and the end surface of the brake caliper piston 42 is parallel to the upper plane of the adjustment block 24. A hemispherical notch is provided on the lower side of the adjustment block 24, and the ball head of the force sensor 22 is arranged in the hemispherical notch. At the same time, a bellows 26 is provided on the outer side of the force sensor 22 to support the adjustment block 24 and prevent the force sensor 22 from being damaged.

[0044] Step S4: Start the actual vehicle 4 to be tested, and the driver performs the braking operation. The brake caliper piston 42 moves downward to contact the adjustment block 24. The adjustment block 24 gives the force sensor 22 a downward force, which is the braking force of the car. The force sensor 22 collects the braking force of the car in real time and transmits the braking force data to the computer 31 through the data acquisition controller 32.

[0045] Step S5: The computer 31 calculates the wheel speed in real time based on the braking force of the vehicle and the dynamics of the vehicle system. At the same time, the computer 31 uses the rotational tooth number equivalent method to set the number of teeth of the speed measuring gear ring 11 to Z1. The number of teeth on the speed ring of the actual vehicle 4 to be tested is Z 2. The wheel speed is N 2, then the speed of the speed ring gear 11 is N 1Should meet:

[0046] Z 1 N 1= Z 2 N 2,

[0047] The rotation speed of the speed measuring gear ring 11 is obtained as:

[0048] N 1= Z 2 N 2 / Z 1.

[0049] The rotation speed of the motor 12 is adjusted and controlled by the data acquisition controller 32 and the motor drive controller 13, and the rotation speed of the speed measuring ring gear 11 is monitored in real time by the wheel speed sensor 44, so as to complete the test of the dynamic electrical performance of the braking system of the actual vehicle 4 to be tested.

[0050] The test bench uses the braking force measuring component 2 to test the real braking force of the automobile, and uses the wheel speed sensor of the actual vehicle 4 to be tested to test the wheel speed simulated by the speed measuring gear ring 11. In the test of the real braking force of the automobile, the control system, braking system and other physical objects of the actual vehicle 4 to be tested are directly used. At the same time, the simulated wheel speed is used to replace the driving wheel speed test that is difficult to complete in the laboratory, which reduces the difficulty of the test, combines the virtual and the real, and ensures the reliability and authenticity of the test results. The dynamic electrical performance test bench of the automobile braking system provided by the present invention can arbitrarily select the existing typical cycle driving conditions or customize the operating conditions of the actual vehicle 4 to be tested according to the needs of the test evaluation, which has strong flexibility and ensures the typicality, representativeness and extensibility of the test conditions.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A dynamic electrical performance test bench for automobile braking system, characterized in that: The invention comprises a wheel speed simulation component (1), a braking force measurement component (2) and a measurement and control component (3), wherein the wheel speed simulation component (1) and the braking force measurement component (2) are both connected to a real vehicle (4) to be tested, the wheel speed simulation component (1) is connected to a wheel speed sensor (44) of the real vehicle (4) to be tested, the braking force measurement component (2) matches a brake caliper housing (41) of the real vehicle (4) to be tested, and the wheel speed simulation component (1) and the braking force measurement component (2) are both connected to the measurement and control component (3); The braking force measuring component (2) comprises a conditioner (21), a force sensor (22), an adjusting block (24) and a feeler gauge (25); the force sensor (22) is connected to the conditioner (21); the conditioner (21) is connected to the measuring and controlling component (3); the adjusting block (24) is arranged on the top of the bellows (26); the force sensor (22) is arranged inside the bellows (26); the bottoms of the force sensor (22) and the bellows (26) are both arranged on the top of a base (27); the feeler gauge (25) is movably arranged between the adjusting block (24) and the brake caliper piston (42); a shim group (23) is arranged at the bottom of the base (27); the adjusting block (24) is arranged on the lower side of the brake caliper piston (42) of the actual vehicle (4) to be tested; and the shim group (23) is arranged on the lower side of the brake caliper housing (41) of the actual vehicle (4) to be tested.

2. The vehicle brake system dynamic electrical performance test bench according to claim 1, characterized in that: The wheel speed simulation component (1) comprises a speed measuring ring gear (11) and a control motor (12); the speed measuring ring gear (11) is fixedly connected to an output shaft of the control motor (12); the control motor (12) is connected to a motor drive controller (13); the motor drive controller (13) is connected to the measurement and control component (3); and the speed measuring ring gear (11) is connected to a wheel speed sensor (44) of a real vehicle (4) to be measured.

3. The vehicle brake system dynamic electrical performance test bench according to claim 1 or 2, characterized in that: The gasket set (23) comprises at least two gaskets arranged one above the other and having different thicknesses.

4. The vehicle brake system dynamic electrical performance test bench according to claim 3 is characterized in that: The feeler gauge (25) comprises a large feeler gauge (251) and a small feeler gauge (252), and the large feeler gauge (251) and the small feeler gauge (252) have different thicknesses.

5. The vehicle brake system dynamic electrical performance test bench according to claim 3, characterized in that: A hemispherical notch is provided at the bottom center of the adjustment block (24), a ball head of the force sensor (22) is arranged in the hemispherical notch, and the bellows (26) is coaxially arranged with the force sensor (22).

6. The vehicle brake system dynamic electrical performance test bench according to claim 4, characterized in that: The measurement and control component (3) comprises a computer (31) and a data acquisition controller (32); the computer (31), the motor drive controller (13) and the conditioner (21) are all connected to the data acquisition controller (32); and the data acquisition controller (32) is connected to the computer (31).

7. The testing method of the vehicle brake system dynamic electrical performance test bench according to claim 6, characterized in that: Step S1: remove the brake caliper of the actual vehicle to be tested (4) and disassemble the friction plate; Step S2: selecting a gasket combination from the gasket set (23) according to the size of the brake caliper housing (41) and placing the combination under the base (27); Step S3: placing the force sensor (22), the gasket assembly (23), and the adjustment block (24) in order from bottom to top inside the brake caliper housing (41) of the actual vehicle to be tested (4), with the end surface of the brake caliper piston (42) being parallel to the upper plane of the adjustment block (24); Step S4: starting the actual vehicle to be tested (4), and having the driver perform a braking operation, obtaining the vehicle braking force through the force sensor (22), and transmitting the vehicle braking force to the computer (31) through the data acquisition controller (32); Step S5: The computer (31) calculates the wheel speed in real time according to the braking force of the vehicle, adjusts and controls the motor (12) through the data acquisition controller (32) and the motor drive controller (13) to control the rotation speed of the speed measuring ring gear (11), and uses the wheel speed sensor (44) to measure the speed of the speed measuring ring gear (11) in real time.

8. The testing method of the vehicle brake system dynamic electrical performance test bench according to claim 7, characterized in that: In step S2, two conditions must be met when selecting shims from the shim group (23): condition T1: the number of shims is minimal; condition T2: the gap between the adjustment block (24) and the brake caliper piston (42) satisfies a gap condition; the gap condition is: the small feeler gauge (252) can pass through the gap, but the large feeler gauge (251) cannot pass through the gap.

9. The testing method of the vehicle brake system dynamic electrical performance test bench according to claim 8, characterized in that: In step S5, the method by which the computer (31) calculates the wheel speed in real time according to the braking force of the vehicle is: assuming that the number of teeth of the speed measuring ring gear (11) is Z 1. The number of teeth on the speed ring of the actual vehicle (4) to be tested is Z 2. The wheel speed is N 2, then the speed of the speed measuring ring gear (11) is N 1Should meet: Z 1 N 1= Z 2 N 2， Then the speed of the speed measuring ring gear (11) is: N 1= Z 2 N 2 / Z 1。

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