Development of an Active Compliance Chamber to Enhance the Performance of Hydraulic Bushings

With the new improvements in the fuel economy engines and to enhance the passenger’s comfort, the topic of active vibration cancellation has received a lot of attention recently by both the automotive industry and researchers. Engine mounts and bushings are the devices used to suppress the transverse and tensional vibrations of engines, respectively. Engine mounts and bushings are primarily designed for the first order vibration of engine. Higher order vibrations, however, are neglected due to their lower amplitudes. Although lots of research has been focused on the improvement of the design and performance of engine mounts, engine bushings has not been addressed well in the literature. This paper focuses on the modeling and design of an active bushing, which addresses the higher order vibrations in engines. Such a bushing has a significant advantage in the ride quality of the newly commercialized variable displacement engine (VDE), where the amplitude of vibration induced by switching is higher than normal engines. For VDEs the higher amplitude of vibration makes the higher orders sensible. Isolation of these vibrations is beyond the capabilities of the passive hydraulic bushings. In this paper the design of a novel active chamber is proposed, which is ultimately utilized to control the fluid pressure inside the bushing. It is evident that the fluid pressure significantly contributes to the dynamic performance of the hydraulic bushing. The active chamber described in this paper utilizes a magnetic actuator, excited by electrical current signal, which is fed to a solenoid coil. The pulses produced by the magnetic actuator are used to adjust the pressure at any specific frequency. This feature enables the active chamber not only to alter the frequency response characteristic of the hydraulic bushing, but also to generate complex pressure frequency responses. A mathematical linear model for the magnetic actuator, and the active bushing assembly, is provided and then verified experimentally. The experimental results confirm that the active hydraulic bushing can well address the sophisticated vibration isolation requirements particular to the VDE systems.