Development of a Robust Adaptive, Model-Based Nonlinear Control Strategy for an Automotive Powertrain, 03-R9466Printer Friendly Version
Inclusive Dates: 04/01/04 04/01/06
Background - Emerging markets in Asia and South America have production lines that are tooled for manual transmissions. In North America, the truck and heavy vehicle industry has also used manual transmissions in their drive trains. The current direction in these markets is to preserve the manual transmission and retrofit an actuator-controller package to make them automated manual transmissions (AMTs). This process not only allows the suppliers to manage business risk but also preserves the fuel economy benefit when compared to torque converter type automatics. The cost of AMTs is also lower than CVTs or torque converter based automatics. The wear in AMTs is lower than manual transmissions, resulting in longer transmission life. The technology developed by SwRI is also useful in controlling dual clutch type AMTs.
After development of an actuator package, the technical challenge for smooth operation of AMTs lies in the development of a clutch control system. Clutch control is especially challenging during launch of the vehicle from zero speed, end of shift engagement, and engagement when vehicle is traveling on grades. The purpose of this project is to develop a control strategy to automatically execute the gearshift and clutch disengagement/engagement using actuators and sensors developed specifically for this application. The goal is to minimize the shift time while emulating the smoothness of a professional driver. SwRI has developed a basic control package to automate a manual transmission (Autoshifter 1.0) under a cooperative R&D program with an industrial sponsor. This internal research effort resulted in development of Autoshifter 2.0, with an ability to launch, shift, and account for grades.
Approach - The development of algorithms and mechanism was managed between two test platforms. A new clutch actuation mechanism has been developed with modification of the OEM master cylinder and additional valving. This development has been carried out on Platform 1, a Chevrolet S-10 light duty truck. The truck transmission shifters have been modified to shift with an H-gate type actuation. In parallel, an electric clutch mechanism and straight configuration shifters have been designed and installed in a test cell (Platform 2) with appropriate torque and speed instrumentation to measure shift shock and launch shock. This infrastructure has been developed in collaboration with an industrial sponsor. The vehicle inertia was simulated with a flywheel and road load with a DC dynamometer. Control algorithms have been developed (Autoshifter 2.0) on this platform for launching the vehicle on grades, level ground, and up shift/down shift during an urban drive cycle. The algorithms used a model-based feed forward component along with gain-scheduled PID structure for clutch position tracking. Calibration tables have been formulated taking into account driver pedal and power train information to allow adaptation to grade and power train aging.