Abstract
Optimization of gear ratio with the objectives of fuel consumption reduction and vehicle longitudinal performance improvement has been the subject of many studies for years. Finding a strategy for changing gears with specific control objectives, especially in the design of vehicles equipped with Continuously Variable Transition system (CVT), which has advantage of arbitrary selection of gear ratio, has been the aim of some recent researches. Optimal control theory has rarely been used in the previous control approaches applied to such systems due to the limitations in the use of fast computational systems. The aim of this study is to design the aforementioned gear ratio change strategy and related control rules on the basis of optimal control. A driver model is also designed for the simulation of driving cycle using MATLAB Simulink Toolbar. Results of implementing optimal control rules in vehicle longitudinal movement simulation with the aim of fuel consumption reduction are finally represented. The presented method has the remarkable advantage of considerable fuel consumption reduction in comparison to other proposed approaches for gear ratio change strategies.
Highlights
Variable transmission (CVT) is an attractive technology and has become more practical with recent improvements in the technology
Torque convertor is locked in this state, governing variables are engine speed and continuously variable transmissions (CVT) ratio and control input is desired CVT ratio that must be followed by CVT first-order system
There exists a need to investigate the fuel-optimal control solution and how much fuel consumption can be improved, because the classical control approaches are based on heuristic deliberations only
Summary
Variable transmission (CVT) is an attractive technology and has become more practical with recent improvements in the technology. CVT is effective in achieving continuously smooth shifting and enables the engine to operate in its most efficient state. Appropriate performance of the system is usually introduced by some characteristics such as rising time, settling time, and overshoot or with some frequency characteristics such as phase margin, gain margin, and band width. With this method for multi-input multioutput systems, different criteria or performance characteristics for achieving the technological requirements are needed. A direct method for introducing these complex systems is called optimal control and it has been a practical solution using digital computers. The objective of optimal control is to determine the control signals which satisfy mechanical constrains and maximize or minimize performance or special criteria
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