Start-Stop Gradeability simulation and methodology development for manual transmission vehicles

Grade climbing capacity establishes a vehicle's distinguishing attribute of handling uneven roads and terrains thereby enhancing its overall performance capability. Vehicle availability and the testing procedure to determine gradeability requires a lot of time and effort. Aiming for the prediction of maximum start-stop gradeability of a vehicle and reducing the testing time and resources, a methodology is established representing the test procedure. A vehicle model is developed in GT Suite having dedicated modules of engine, clutch, transmission, vehicle and a driver. The vehicle is having weight of 2999 kg and a 1499 cc of engine with 80 hp power and 210 Nm torque. In simulation, the driver targeted the engine's launching speed profile, which progressively engaged the clutch to prevent engine stalling. The target is to ascend a specified distance in a predetermined amount of time without stalling the engine. Upon reaching the maximum grade the vehicle can climb, the engine will not be able to provide enough torque to maintain required acceleration, resulting in the engine stalling. This process is repeated with different vehicle parameters for validation. The simulated results indicated the gradeability of 15.1° as compared to the measured gradeability of 15.0° on the same vehicle and intended loading configuration. This strong co-relation with delta <1% established the confidence to explore gradeability potential with further combinations of engine torque, gear ratio, clutch and transmission. This paper explains in detail how clutch modulation time plays an important role to explore the gradeability potential further.