Robust stabilization of high speed oscillations in single track vehicles

Design configuration (wheelbase, rake angle, trail, location of center of gravity, etc.) of high speed motorcycles is generally a compromise. Some underdamped oscillatory behavior at high speeds must be tolerated to make motorcycles maneuverable with reasonable rider effort. Two well known oscillations are the weave and wobble modes. To analyze the problem the authors have employed a mathematical model of motorcycles to describe the motions in straight running, steady state turning, and transitory maneuvers. This model also includes the dynamics of the engine, as it is attached to the frame by elastic mounts. The model is nonlinear and has 18 states, including tire dynamics, engine dynamics, and important structural properties of the frame. The authors have proposed a multi-input multi-output feedback control system to effectively control oscillatory motion of motorcycles at speeds. Measured signals can be roll rate and yaw rate or alternatively, steering angle and lateral acceleration of the vehicle. Controller outputs are signals to active engine mounts. By feedback control of engine´s orientation with respect to the frame, this controller stabilizes the vehicle in a wide range of speed well beyond the current speed record for single-track vehicles. Special challenges in design of the controller are that the engine displacement relative to frame must remain small, and the controller must be robust with respect to significant variations in vehicle´s forward speed.