Parallel Active Link Suspension: A Quarter-Car Experimental Study

In this paper, a novel electromechanical active suspension for cars, the parallel active link suspension ( PALS) is proposed and then experimentally studied. PALS involves the introduction of a rotary-actuator-driven rocker-pushrod mechanism in parallel with the conventional passive suspension assembly, to exert an additional controlled force between the chassis and the wheel. The PALS geometric arrangement is designed and optimized to maximize the rocker torque propagation onto the tire load increment. A quarter-car test rig with double wishbone suspension is utilized for the PALS physical implementation. Based on a linear equivalent model of the PALS quarter car, a conservative and an aggressive robust H-infinity control schemes are synthesized separately to improve the ride comfort and the road holding, with different levels of control effort allowed in each of the control schemes. Simulations with a theoretical nonlinear model of the PALS quarter car are performed to evaluate the potential in suspension performance enhancement and power demand in the rocker actuator. Experiments with a harmonic road, a smoothed bump and hole, and swept frequency are conducted with the quarter-car test rig to validate the practical feasibility of the novel PALS, the ride comfort enhancement, and the accuracy of the theoretical model and of a further nonlinear model in which practical features existing in the test rig are identified and included.