Abstract
This study proposes and experimentally validates an optimal integrated system to control the automotive continuously variable transmission (CVT) by Model Predictive Control (MPC) to achieve its expected transmission efficiency range. The control system framework consists of top and bottom layers. In the top layer, a driving intention recognition system is designed on the basis of fuzzy control strategy to determine the relationship between the driver intention and CVT target ratio at the corresponding time. In the bottom layer, a new slip state dynamic equation is obtained considering slip characteristics and its related constraints, and a clamping force bench is established. Innovatively, a joint controller based on model predictive control (MPC) is designed taking internal combustion engine torque and slip between the metal belt and pulley as optimization dual targets. A cycle is attained by solving the optimization target to achieve optimum engine torque and the input slip in real-time. Moreover, the new controller provides good robustness. Finally, performance is tested by actual CVT vehicles. Results show that compared with traditional control, the proposed control improves vehicle transmission efficiency by approximately 9.12%–9.35% with high accuracy.
Highlights
Over the past decade, improving transmission efficiency and optimizing power matching have become the main development trend of automatic transmission technology worldwide [1]
When the vehicle throttle opening is constant, the ratio is precisely controlled to ensure that the engine output power and running resistance can be optimally matched according to the driver intention in real time
4.5 Simulation and Analysis of Control System On the basis of robust performance test analysis, the controller designed based on the model predictive control strategy and the safety factor method control strategy is compared and tested under New European Driving Cycle (NEDC) cycle conditions to ensure reliability and consistency
Summary
Over the past decade, improving transmission efficiency and optimizing power matching have become the main development trend of automatic transmission technology worldwide [1]. A certain degree of slip does not damage the metal belt and increases the friction factor, effectively reduces the clamping force, improves the transmission efficiency, and extends the service life of the CVT (Figure 2) [10]. The optimization effect can be improved, which is by determining the target speed ratio based on the accelerator pedal opening degree representing the driver intent, tracking control is added and the driving experience is verified according to different types of drivers [22,23,24,25] This optimization method improves the transmission efficiency to a certain extent, but ignores the CVT advantages that can be combined with the engine to achieve joint optimization control and dramatically improve the transmission. The diagram of overall control strategy is shown in the Figure 3
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