This thesis examines various control strategies aimed at optimising the steady-state operation of engine-transmission systems for heavy commercial vehicles in order to achieve minimum fuel consumption. The work includes three stages: i) the analysis and synthesis of the problems associated with the control of propulsion plants, ii) the mathematical optimisation of multi-variable systems and iii) the optimisation of an engine shunt-transmission system. The control of propulsion plants for heavy commercial vehicles is examined by reviewing the prime movers and transmissions in use or likely to be used in the near future. The parameters specially highlighted include the external controls and the alterations which can be made to improve component matching. The problem of optimising multi-variable systems is set out. The mathematical optimisation of multi-variable systems involves techniques for the maximization of a n-variable function specific to propulsion plants. The function maximized is not known analytically and can only be evaluated at discrete points. A large number of searching procedures are reviewed and developed to minimize the number of evaluations. The engine transmission system optimised comprises a diesel engine driving a hydro-mechanical transmission of the shunt type. The hydrostatic drive is made up of two variable-displacement units. The external controls are the fuel rack position and the two unit swash displacements. The characteristics of the system are investigated theoretically. Various optimisers, scheduled and on-line, are proposed and one has been fitted on a test rig and will be tested shortly.
|Date of Award