Development and analysis of a suspension control logic for motorcycling application

The genesis of intelligent suspensions can be traced back to the latter part of the last century when the concept of isolating oscillations was applied to automotive suspensions. This sparked a wave of research and development focused on creating suspensions capable of providing controlled responses. Differently from the automobile industry, motorcycle makers and OEMs have shown interest towards active suspension systems only in recent years, limited by the technological challenges that the implementation of these systems presents in the motorcycle field. Foremost among these are weight, space, and energy constraints. Therefore, the mass production of motorbikes equipped with live-tunable suspension settings is restricted to the so-called semi-active suspension layouts. Differently from an active suspension system, a semi-active prototype requires a considerably lower amount of energy, but on the other hand, is limited by the passivity constrain. In the current thesis project, pre-existing control logics applied to semi-active suspension layouts are investigated and compared. The principal observation will point out the conflict between comfort and handling, a limiting factor of the traditional passive systems and semi-active suspension control strategies. In recent years, more sophisticated control rationales able to minimize such dispute have been presented. The more and more dynamic environment of premium motorcycles opting for semi-active suspension schemes, motivates the research of an alternative solution to control semi-active suspension systems for 2-wheeled vehicles. In the current thesis project, the author focused on the possibility of designing a simpler control logic based on a blend of pre-existed control rationales able to minimize the handling-comfort duality. The backbone of the control logic is represented by two separate control logics; one able to master the handling, and a second capable of maximising comfort indexes. The suspension control unit will be finally responsible for identifying the motorcycle riding condition and thus, select to which extent to focus the orientation of the controller towards comfort to the detriment of the handling, or vice-versa. From this perspective, such 'Hybrid' control logic is indeed able to overcome the comfort-handling conflict. Different indexes exploited in the literature to measure comfort and road-holding are presented and used to measure coherently the performance of the Hybrid control logic. The design of the controller will be pursued through the simulation of the suspension through a quarter-car model in a Matlab-Simulink environment. Successively the control rationale is optimized in a 4DOF motorcycle model and the resulting performances are shown. To conclude the thesis project a test and validation of the controller is performed via the IPG MotorcycleMaker vehicle simulator.