Asymmetric Energy Harvesting and Hydraulically Interconnected Suspension: Modeling and Validations

Traditional vehicle suspension system is equipped with isolated shock absorbers that can only dissipate energy by themselves. Hydraulic interconnected suspension uses hydraulic circuits to connect each shock absorber, so that the energized hydraulic fluid can be utilized to counter unwanted body motion to improve the overall dynamic performance. The hydraulic interconnected suspension is a proven concept that has shown good potential in controlling body rolling and decoupling the warp mode from other dynamic modes. Hydraulic interconnected suspension is still passive and lack of adaptivity, while some active or semi-active suspension technologies allow the shock absorbers to counter the road disturbances using external power input. Active suspensions such as electro-magnetic shock absorbers use the variable viscosity of magnetofluid to alter the damping characteristics of the suspension to adapt to quickly changing road conditions. The energy demand from an active suspension can reach the level of kilowatts in certain cases, which results in lowered fuel efficiency of the vehicle. To find a balanced solution to dynamic performance and energy efficiency, this paper introduces a new form of energy-harvesting suspension that is integrated in a hydraulically interconnected suspension (HIS) system. The combined energy-harvesting and hydraulic interconnection features provide improved energy efficiency and vehicle dynamics performance. A single cylinder model is built in AMESim for preliminary study and validated in a bench test. The bench test results proved the authenticity of the theoretical model, and the model is then used to predict the system performance and guide the hardware construction. Based on the proven single cylinder model, and a full car model are developed to validate the effectiveness of the overall system design. Different dynamic input scenarios are used for model simulation, which includes single-wheel sinusoidal input, braking test and double lane change test. In the double lane change test, the EHHIS sees averagely 70% improved in roll angle relative to a conventional suspension, and averagely 22% improvement relative to simple hydraulically interconnected suspension. The power generated is found to reach maximum at 4 Ω external resistance and the highest average power generated is more than 70 watts at 2 hz 20 mm sinusoidal input. A road test of a half vehicle EHHIS system is done. From the road test results, the EHHIS meets the expectations of reducing roll angles. The riding comfort is evaluated with the RMS value of the vertical acceleration and is found to have minimum compromise from the greater damping coefficient.