Research On Constraint System Of Steady-state Braking Testing Of All-wheel-drive Vehicle On Bench

The vehicle braking performance, which is directly related to the safety of automobiledriving, is one of the necessary test items. And it is the key performance of the automobilesafely driving. The braking performance test is always finished with the braking bench.However, the testing mechanism is commonly used to test the FWD-forward wheel drivevehicle or RWD-rear wheel drive without the condition of testing the all-wheel-drivevehicles. The all-wheel-drive vehicles can’t be tested in the common braking bench.Currently, the all-wheel-drive vehicles are popular with the family, and gradually used inthose industries, such as Military, mining and oil field. Therefore, it is necessary to realizethe study on the all-wheel-drive vehicles braking test on bench.Currently, the test line widely used anti-force roller brake tester. The testing wheels areon the bench, and the non-testing wheels are on the ground in the common vehicle test.Because the ground adhesion is the horizontal restrain of the testing wheel. When therestraint force is large enough, the test result is close to the ability of the brake capability.For the full drive brake test, the testing wheels are on the bench, and the non-testing wheelsare free to rotate. Therefore, the testing wheels will be out of the drum, climb roll back, andeven slip out of the test bench because of lack of adhesion. Therefore, the external forcemust be imposed to realize the brake force stably tested and improve the braking testcapacity for the all-wheel-drive vehicles test.On the basis of the existing roller brake tester, analyzed the horizontal binding effecton the braking performance test, Studied a set of constraint system for all-wheel-drivevehicle, it can satisfy the whole drive car in steady state on the bench when testing thebraking performance. This paper mainly do research in the following work:1. According to the structure and working principle of the reaction force roller brakestation,analyzed the factors of braking performance.Established the brake testing mechanicsmodel without additional level constraints. It shows that when testing the brakingperformance of the all-wheel-drive vehicle, it must apply horizontal binding, which canrealize the braking performance of detection.2. Established the brake testing mechanics model with additional level constraints.According to the variation of the maximum braking force of the vehicle in a steady state andnon-steady state, Analysis the influence of the level of binding on bench testing capabilities, and put forward the wheel way constraints the location of the different size influence onmaximum braking force test，raise the best position of the force on horizontal restraint.3. According to the theoretical analysis, put forward the design request of the machinesof the horizontal resistant system. According to the design request, confirm the designscheme, using roller to constrain the Wheels, and using the hydraulic cylinder as theactuator to drive the drum of constraints in place. At last, used the hydraulic cylinder toreplace the swimming arm to realize the Lateral and longitudinal motion of the constrainedroller.4. put forward the control theory of the system with the control algorithm of theincremental PID to realize synchronous and in-place control of the hydraulic cylinder,according to the structure of the machine and the hydraulic system. The control system is atthe control center of SCM AT89S5. Finish the hardware and software design on thehorizontal constraint control system. The hardware design includes analog signal collectionand processing, serial communication, electromagnetic relay control, and signal controlvehicles in place. The software design includes start and stop control flow in the hydraulicsystem, A/D and D/A conversion control process and synchronization control process in thehydraulic system.5. According to the test condition, work out the test plan, including the test objective,the installation and design of the test device and the test procedure. The test scheme has thesame design idea with the constraint system and design scheme of the paper. Use theoutside non-binding force, the front-suspension pull, and the front-wheel limit respectivelyto carry out the testing of Brake performance. The front-suspension pull is imposing thewheel-radius-position and horizontal binding on tested wheel. Using the roller to constrainthe front wheel, the roller has the normal force to the wheels on the contact position,resolved the horizontal and vertical force. Analyze the test data, and conclude that thebraking bench test capacity with the outside binding is bigger than that with the outsidenon-binding force, and that the braking bench test capacity with the front-suspension pull isbigger than that with the front-wheel limit and can better reflect the braking capacity of thebrake during the vehicle test. Analyze the binding position of the roller front-wheel limit. Itconfirms the horizontal resistant force has effects on the braking test.