The steering system produces stick-slip vibration and noise due to the relative rotational friction between various components, resulting in unsmooth steering. To solve this problem, this paper studies the practical problems of stick-slip caused by worm gear deceleration mechanism of steering gear. The source of the problems are identified through tests, and the relevant influencing factors are determined by establishing a theoretical force model and CAE simulation analysis model. The torque anti-drop function MSP (Mechanical Stuck Prevention) of the steering gear is developed simultaneously. The software functional architecture and module interfaces are designed and the activation parameters are set through the debugging and optimization of the software functions. Finally, the output square wave signal of the motor torque 0.03 N·m is locked, which satisfies the software real-time control requirement, and improves the handing comfort of the vehicle.

Based on the study of the three parameter control objectives of Pedal Map, a calibration control program for Pedal Map of electric vehicle is designed, and effective control of three parameter objectives are realized through MATLAB traversal interpolation. Simulation calculations and real vehicle testing results verify that the control objective based on the three parameters can effectively achieve the calibration and control of the pedal characteristics of electric vehicle. The experimental and simulation comparison results of the longitudinal acceleration curve show that the control program can accurately achieve the calibration control objective requirements and successfully achieve automatic calibration.

In order to efficiently realize the measurement of vehicle wheel brows, a non-contact vehicle wheel fender clearance measurement system is designed based on image processing technology, and corresponding measurement software is created with the Graphical User Interface (GUI) of MATLAB. The verification results show that for actual clearance of at least 15 mm, the error of the wheel fender clearance calculated by the system under different shooting distance conditions is controlled within 2%, which exhibiting a high degree of measurement accuracy.

In order to improve the accuracy, stability and flexibility of the vehicle chassis geometric parameter detection system, a vehicle chassis geometric parameter measurement system consisting of LED type 3D surface measurement sensors is designed based on stereo photogrammetry, using a structured LED light source to form a “spatial measurement area” based on the entire wheel side surface and wheel cover edge. By using 3D photography technology to obtain point cloud data under dynamic measurement, and combining with x-line software, a 3D wheel hub model is established to analyze and calculate the front toe camber angle of the chassis, the linearity and repeatability of the measurement system. The results show that linearity error of this measurement system is 1.528', repeatability error of front toe angle and camber angle are ±0.03' and ±0.05' respectively, verifying stability and reliability of the measurement system.

In order to analyze the influence of random and impulse road surface on the smoothness of commercial vehicles, a commercial vehicle is taken as the research object to construct the vehicle dynamics model containing front and rear suspension, tire, body, steering system and human body-seat system by using the ADAMS/Car software. The smoothness analysis of impulse and random input is carried out for the vehicle, and simulation results show that the smoothness of the vehicle increases after increasing the vehicle speed under the excitation of pulse road surface; the effect of smoothness is more significant on Class C road compared with Class B road under the random road surface input condition, which is more effective in the evaluation and improvement of driving comfort of commercial vehicles.

In order to improve the vehicle driving range of a pure electric light commercial vehicle, this paper proposes to reduce the electric power consumption per 100 kilometers by reducing power consumption and increasing coasting energy recovery power. Firstly, for ECO energy-saving mode, the paper proposes the energy-saving control technology based on different vehicle usage scenarios and working conditions, which significantly reduces the energy consumption of the vehicle in the whole scenario. Secondly, in the view of the coasting energy recovery deceleration of commercial vehicles with empty and full load varies greatly, the paper proposes the energy recovery control based on the vehicle mass to achieve the same coasting deceleration under different loads to recover more energy. Then, for the problem that coasting energy recovery is usually designed with low adhesion coefficient road surface, the paper proposes adaptive adjustment of coasting energy recovery based on road adhesion coefficient. Finally, the pure electric light truck is tested on real road. The results show that the ECO mode reduces the electricity consumption per 100 kilometers by 2.9%, and by 2.1% for scenarios of turning on the air conditioning and opening the car door. The energy recovery strategy based on the vehicle’s mass shows a 2.7% reduction in electricity consumption per 100 kilometers.

In order to realize automatic test and effectiveness verification of Automatic Mechanical Transmission (AMT), an automatic testing sequence is constructed based on the Hardware-in-the-Loop (HiL) testing system and automated testing software for the low gear shifting stuck fault of AMT front auxiliary gearbox. The fault diagnosis response is tested, and the test results show that the fault diagnosis response meets expectations, verifying the accuracy of the test sequence and fault diagnosis. Based on the test sequence, the normal gear shifting at high speed, gear shifting without fault and the low gear shifting of the front auxiliary gearbox under fault response are established. Test results show that the Transmission Control Unit (TCU) recognizes and responds in time when the front auxiliary gearbox low gear shift stuck fault occurs. The response is in line with expectations, and it also can keep the vehicle running normally under the fault diagnosis response, which verifies the effectiveness of the fault diagnosis response.