Xing Xu

Experimental and simulation study on the vibration isolation and torsion elimination performances of interconnected air suspensions

This paper extends recent research on the dynamic performance of an interconnected air suspension. Although some aspects of the dynamic performance of such suspension systems have been studied, little attention has yet been paid to the torsion elimination performance or to the way in which the form of interconnection influences the interconnecting effectiveness. A model car test bench equipped with interconnected air spring suspensions is constructed and the vibration isolation performances of different interconnections are compared. The test results show that the r.m.s. acceleration value of the vehicle body is reduced by 1.2–6.1% using a lateral interconnection, while it is reduced by 0.1–3.3% using a longitudinal interconnection, because of the longer interconnecting pipes. Further research proves that laterally interconnected air suspensions can gain interconnecting effectiveness by using shorter and thinner interconnecting pipes, and this means that they are more suitable for small- and medium-sized vehicles. When the deformation of the vehicle body is considered, a new eight-degree-of-freedom mathematical model is designed and verified by test examination. This model is used to study the torsion elimination performance, the roll performance and the pitch performance of a laterally interconnected air suspension. It shows that the peak torsional load of the vehicle body under step examination is reduced by 6.68–17.65% on interconnection and, after entering the steady state, the torsional load is almost eliminated. The body roll angle which is caused by the road roughness is reduced by around 6%, while the pitch angle shows little change.

Research on Modeling and Characteristics of Two-Stage Pressure Hydro-Pneumatic Spring

The structure and principle of the two-stage pressure hydro-pneumatic spring were introduced. the physical and dynamic vehicle models with it were established under AMESim environment. Static characteristic curves of the two-stage pressure hydro-pneumatic spring were drawn. A single chamber hydro-pneumatic spring was used to compare the suspension dynamic travel and body vertical acceleration of the vehicles equipped with two-stage pressure hydro-pneumatic spring. The results show that two-stage pressure hydro-pneumatic spring can effectively enhance the vehicle riding comfort by decreasing body vibration.

Study on Torsion-Eliminating Performance of Laterally Interconnected Air Suspension

Laterally interconnected air suspension combines the right and left air springs with pneumatic pipes, which can protect the auto-body parts from fatigue damage and increase the service life of vehicles. The mathematical model of full vehicle with laterally interconnected air suspension was established based on the analysis of its working principle, and a test bench was built. The simulation and experimental results show that, laterally interconnected air suspension can reduce the peak of dynamic body torsion load effectively, especially for steady state conditions, in which the body torsion load caused by the spring force can be nearly eliminated.

Modeling and Validation of Air Suspension with Auxiliary Chamber Based on Electromechanical Analogy Theory

In order to effectively avoid the complexity and difficulty in analyzing the differential equations during the modeling process of air suspensions with auxiliary air chambers, electromechanical similarity theories were introduced, an equivalent electrical model was developed by analyzing parameters interaction relationship of the parts between electromechanical systems and mechanical system. The electrical model was verified and validated through comparisons and analysis between characteristic tests towards air suspension with auxiliary air chamber and simulation of equivalent electrical model.

Plumpness Analysis of Indicator Diagram for Vehicle Damper

According to the indicator diagram of damper, the indicator diagram plumpness was proposed as a quantitative index, and its mathematical relationships with the sprung mass acceleration, suspension dynamic travel and tire dynamic load were built. Moreover, the influence of the total area on suspension characteristics was analyzed in time domain and frequency domain. The results show that, the increase of the indicator diagram plumpness can effectively restrain the variation of suspension dynamic travel and tire dynamic load, meanwhile, the body acceleration will be enlarged. Excessive indicator diagram plumpness also affects the dynamic tire load distribution in frequency domain, and it will decrease the driving security. Therefore, it should be reasonably selected from the performance indicators, which is based on the requirement of vehicle demand in the design process.

Slow On-Off Control of Two-State Damping for Electrically Controlled Air Suspension Based on Extended Kalman Filter

To improve riding performance of the bus with air suspension, the half-car nonlinear model of air suspension was created with the help of analyzing nonlinear character of spring-pneumatic. Slow on-off control of two-state damping was proposed according to the tire deformation and suspension deflection, and the shock absorber with two-state damping was designed by opening and closing the orifice of throttle. It was difficult to obtain the tire deformation directly, and the state-observer of air suspension was proposed based on Extended Kalman Filtering (EKF) algorithm, namely the tire deformation was estimated by the suspension deflection and its relative changing speed. Simulation shows EKF algorithm can estimate the running states well, and the estimating error of RMS is below 10% in 3 seconds and the whole vehicle testing validate that the slow on-off control can enhance the capability of air suspension.

Ride Height Control of Trucks with Electrically Controlled Air Suspension Based on PID/PWM Algorithm

The truck with Electrically Controlled Air Suspension(ECAS) could reduce the loss of goods by setting running height when transporting, and to enhance the loading &unloading efficiency, a height modulating model was built by combining the theories of thermodynamics of variable-mass charging-discharging system and the vehicle kinetics. To solve such problems as “over-charging”, “over-discharging” and surging, a height control strategy of variable integral PID/PWM was proposed and its controller was developed base on the Freescale single chip. Finally the semi-physical rig was built for simulating the truck with the height controller, and the testing results show that the designed control system satisfies the requirement of height modulation.