|Thesis abstract: |
The thesis addresses the identification and control of automatic transmission systems in two-wheeled vehicles. As a matter of fact, an active control of the vehicle powertrain makes it possible to regulate the vehicle dynamical behaviour so as to achieve prescribed comfort and performance levels.
In the scientific literature, several investigations of vehicle transmissions system were presented, proposing different mechanical solutions and active control systems. Most of them, however, are tailored to cars, trucks and other heavy vehicles, while applications in the two-wheeled vehicles field are still largely unexplored. In this context, the present research aims to expand the current state of the art considering the latter class of vehicles, developing novel analysis tools and control laws able to properly manage an automatic transmission system in two-wheeled vehicles. To this purpose, two vehicle classes have been considered: (1) high-performance motorcycles and (2) conventional bicycles for city usage.
As apparent, the system analysis and the control objectives for the two classes of vehicles are different, thus needing ad-hoc solutions for each of them. However, they also share a common methodological pathway that can be summarised into three main goals: (1) derive consistent control-oriented models of the two vehicles powertrain systems and validate them through experimental tests on the vehicles; (2) design of suitable controllers for the transmission components, able to ensure prescribed performance levels; (3) design of vehicle-level controllers that, using the controlled-transmission system as main actuator, allow to achieve high-level objectives, managing e.g., comfort and safety aspects or regulating the vehicle energy flows.
The high-performance motorcycle powertrain is a complex system, constituted by the connection of several components, such as the engine, the clutch, the gearbox and all the additional equipment indispensable to make the system electronically controllable. The main powertrain actuator is the clutch, thus the first step concern its control. Then, a proper and coordinated use of the clutch, gearbox and engine allows to manage vehicle-level operations, such as the launch manoeuvre and the gear shifting. Finally, suitable quality indexes are proposed to assess the quality of different vehicle-level control strategies, quantitatively evaluating both the performance and the comfort levels achievable according to different control logics.
Turning to the bicycle application, the automatic transmission system is a continuously variable transmission (CVT) system. For such a system, a proper control architecture is firstly proposed so as to effectively control the transmission ratio between the pedal and the vehicle velocities. Then, such a transmission ratio is the control variable of the vehicle-level controller. As a matter of fact, in bicycles the source of power, i.e. the human body, is a (very) low power engine and the efficient use of its energetic resources is the nodal point to considerably improve the whole system efficiency. To this purpose, the identification of a control-oriented bio-physical model of the rider is needed to gather the necessary information to relate her/his physical strain to the produced power. Based on this model, a vehicle-level control law can be designed to actively control the rider strain. Finally, the proposed controllers have been experimentally tested, thereby confirming the suitability of the proposed approach.