Electromechanical Actuated Active Suspension Using Threadless Linear Transmission: Adjustable Stiffness and Damping

Active suspension systems using hydraulic actuators, air suspensions, or magnetorheological dampers, can enhance riding comfort and handling of vehicles by adapting ride height, stiffness, and damping according to driving style and road conditions. Because space and weight are critical considerations for choosing components of automobiles, brushless DC (BLDC) motors usually having high torque density might be an option chosen as the actuator of the active suspension. The controller of MIT Mini Cheetah actuators allows real-time modulation of stiffness and damping for achieving dynamic movement. This paper presents a novel design concept of active suspension applying a BLDC motor to create stiffness and damping for a double wishbone suspension system in addition to the intrinsic properties obtained from the mechanical spring and damper. The Roh'Lix linear transmission is introduced for converting the rotation of the motor to the spatial motion of the suspension arm resulting in vertical movement of the wheel knuckle. The Roh'Lix is operated with a threadless shaft instead of a conventional ball screw for achieving higher back-drivability. The scaled prototype of the suspension system was built from 3D printed parts with appropriate bearing support. The ODrive Pro motor controller with a magnetic encoder was applied to control the BLDC motor's stiffness and damping, as desired. The constant speed tests were conducted in both upward and downward directions to observe the effect of gravity, static friction, and intrinsic damping. The vibration tests were conducted by setting different values of stiffness and damping. The system inertia was estimated, and the modulation of stiffness and damping was validated experimentally.