Constant power-continuously variable transmission (CP-CVT) : optimisation and simulation

摘要

A novel continuously variable transmission has previously been designed that is capable of addressing a number of concerns within the automotive industry such as reduced emissions. At the commencement of this research, the design was in the early stages of development and little attempt had been previously made to optimise the design to meet specific measurable targets. This thesis utilises and modifies several design approaches to take the design from the concept stage to a usable product. Several optimisation techniques are adapted and created to analyse the CVT from both a design and tribological prospective. A specially designed optimisation algorithm has been created that is capable of quickly improving each critical component dimension in parallel to fulfil multiple objectives. This algorithm can be easily adapted for alternative applications and objectives. The validity of the optimised design is demonstrated through a simulation-tool that has been created in order to model the behaviour of the CVT in a real automotive environment using multiple fundamental theories and models including tire friction and traction behaviour. This powerful simulation tool is capable of predicting transmission and vehicular behaviour, and demonstrates a very good correlation with real-world data. A design critique is then performed that assesses the current state of the CVT design, and looks to address some of the concerns that have been found through the various methods used. A specific prototype design is also presented, based on the optimisation techniques developed, although the actual creation of a prototype is not presented here. Additional complementary research looks at the accuracy of the tire friction models through the use of a specially design tire friction test rig. Furthermore, a monitoring system is proposed for this particular CVT design (and similar) that is capable of continuously checking the contact film thickness between adjacent elements to ensure that there is sufficient lubricant to avoid metal-on-metal contact. The system, which is based around capacitance, requires the knowledge of the behaviour of the lubricant’s permittivity at increased pressure. This behaviour is studied through the use of a specially-designed experimental test rig.