Design of a linear motor-based shaker rig for testing driver's perceived ride comfort

In autonomous vehicles the driver will become a passenger. By ensuring a high level of ride comfort through active suspensions, the driver's ability to perform various tasks such as reading, drawing and texting can be enhanced. A high-performance shaker rig can conveniently be used to test the ride comfort improvement by means of various active suspensions under laboratory conditions. The paper deals with the design of such a rig, which employs a linear electric servomotor to impose accurately controlled vertical vibrations of driver seat. The reference time profiles of seat acceleration, velocity and displacement are generated off-line by using a half-car vehicle model and LQR control with a road preview option. The selection of linear motor comes from assessment of three characteristic shaker rig drive designs (hydraulic and two electric ones). To ensure high-precision seat motion, the proposed shaker control system includes: acceleration feedforward and feedback control loops, a state controller-like compensator of accelerometer offset to prevent drift of seat position and velocity, and feedforward compensation of linear motor cogging force mode. The designed shaker rig application is demonstrated through a case study related to ride comfort evaluation of various active suspension configurations and a drawing task. The drawing task results are employed to determine the root-mean-square vertical seat acceleration threshold, below which the active suspension drawing task performance remains similar to that obtained under standstill conditions.