Series Active Variable Geometry Suspension: Full-Car Prototyping and Road Testing

In this article, a full-car prototype of the recently proposed mechatronic suspension, series active variable geometry suspension (SAVGS), is developed for the on-road driving experimental proof of concept, aiming to be adopted by suspension original equipment manufacturers as an alternative solution to fully active suspensions. Particularly, mechanical modifications are performed to both corners of the front double-wishbone suspension of a production car with active single link attached to the upper ends of the spring–damper units, while both corners of the rear suspension remain in the original (passive) configurations. The mechanical modifications involve innovatively designed parts to enable the desired suspension performance improvements while maintaining ride harshness at the conventional levels. A real-time embedded system is further developed to primarily implement power supply, data acquisition, and measurements of the vehicle dynamics-related variables, and robust control application for the ride comfort and road holding enhancement, which is based on a derived linearized model of the full-car dynamics and a newly synthesized H-infinity control scheme. The results obtained from the on-road driving experiments are in essential agreement with numerical simulation results also produced. Overall, the full-car prototype of SAVGS demonstrates promising suspension performance with an average 3 dB attenuation (or equivalently 30% reduction) of the chassis vertical acceleration at around the human-sensitive frequencies (2–5 Hz), as compared with the original vehicle with the passive suspension system. More importantly, the prototype also indicates the practicality of the solution, as the SAVGS retrofit to a real car is achieved by simple mechanical modifications, compact actuator packaging, small mass increment (21.5 kg increase with respect to the original vehicle), limited power usage (an average value of 134 W in dc batteries with a Class D random road), and acceptable economic cost.