The Development Of Auxiliary Device For Bench Test Of Braking Performance Of All-wheel-drive Vehicles

With the development of the automotive industry,the number of vehicles in our country is increasing rapidly.Car safety is highly valued by the government and all the traffic participants.As the braking performance is directly related to driving safety,the braking performance must be checked annually.Although the detection of the braking force can be achieved by the road test method,in order to improve the detection efficiency,the testing facilities generally use the bench method to test the vehicle's braking force.Compared with the ordinary two-wheel drive vehicles,the full-time AWD vehicles have greater traction while driving on the roads,thus the number of AWD vehicles increases gradually recently.However,due to the unique power transmission system of the full-time AWD vehicles,its wheels of front and rear axle always rotate together,therefore the braking force of full-time AWD vehicles can't be detected by the general single-axis reaction roller brake test bench.In order to achieve the detection of braking force of full-time AWD vehicles,it's necessary to develop an auxiliary device.The braking force of the full-time AWD vehicles can't be detected by the normal reaction roller brake test bench.Consequently,this paper proposes and develops an auxiliary device,which is easy and reliable,to achieve the bench test of full-time AWD vehicles.The research work mainly includes the following aspects:(1)This paper analyzes the reason why the braking force of the AWD vehicles can't be tested by the normal reaction drum brake tester,and proposes a new method that the non-detected wheels are placed on the free rollers and use a horizontal roller to constraint the detected wheels.Through the theoretical analysis,it is concluded that both increasing the preload between the restraining roller and detected wheels and reducing the angle between the preload and the horizontal direction can improve the testing capability of brake test bench.(2)According to the theoretical analysis results,the scheme of the auxiliary detection device is determined,and the design of the mechanical structure and the hydraulic system is also completed.Besides,the strength of the crucial mechanical structure is checked by the finite element method.The control system with three control modes is designed to realize the bench test of the braking force of all wheel drive vehicles with different parameters.(3)In order to verify the effectiveness of the auxiliary device,a test with a real car carried out after the completion of installation and commissioning of the auxiliary device.The test results of a time-sharing AWD vehicle at two drive modes show that the auxiliary device developed by this project not only realizes the braking performance bench test of the ordinary two drive vehicles,but also effectively detect the braking force of AWD vehicles.Moreover,this paper verifies the conclusion that increasing the preload between the restraining roller and detected wheels and reducing the angle between the preload and the horizontal direction can improve the capability of brake test bench.