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The paper discusses a fuzzy supervisor for ensuring co-operation between clutch and engine control reference values during standing starts and gear shifts in a vehicle equipped with a servoactuated transmission. A mathematical model of the powertrain was developed to identify the optimal control strategy for different clutch friction characteristics and operating conditions. The powertrain is modeled as a six d.o.f. dynamic system, consisting of the engine and flywheel assembly, clutch disk, mainshaft and countershaft, transmission shaft with differential and hub, front wheels, tires and car body with rear wheels. The engine is described by its experimental mechanical characteristic. The model considers lumped parameters, and springiness of the shafts is neglected. A large number of simulations was carried out in order to identify control strategies which minimize dissipated power and judder and prevent engine stalling during standing starts.

A crucial problem in designing a servoactuated manual transmission is posed by the clutch torque variations which depend on operating conditions with equal clutch pedal position and clutch slip. An experimental study of the phenomena that determine torque variations can be particularly useful in coping with this problem. To this end, the authors developed a powertrain test bench. The bench makes it possible to measure the main magnitudes (disc temperature, clutch slip, clamp load and clutch disc displacement) which can influence transmitted torque. Test bench layout is described. Some experimental results are presented and discussed, with particular attention to the problems connected with clutch controller design.