Towards Pareto Optimization of Performance of a Generic Synchronizer of Transmission Systems

Abstract

Manual transmissions for passenger cars and trucks are equipped with synchronizer mechanisms. A synchronizer mechanism as a key component of a transmission system must be able to prevent transmission gears from shocking, reduce the noise and it has a great impact on driving comfort and transmission efficiency. Gear shifting improvement with respect to smooth, quick and energy efficient synchronizer’s performance is still an important issue for automotive industry. A synchronization process comprises several phases within which presynchronization, main synchronization, pre-engagement and engagement phases can be recognized. Aiming an understanding of internal dynamics and existing possibilities for optimization of synchronization processes in transmission systems during the main synchronization phase an engineering model of a generic synchronizer mechanism is proposed. The synchronizer mechanism is modeled by a contacting triple-body system consisting of the selector sleeve, the blocker ring and the gearwheel. The algorithm has developed to solve the direct dynamics synchronization problem for the generic synchronizer mechanism. By using the developed algorithm the rotational motion of the contacting triple-body system and the synchronizing torques between contacting interfaces are determined for given vehicle resistance torque, the drag torque, and the control torque applied to the selector sleeve that all together satisfy the equations of motion and guarantee synchronization of the rotational speeds of the sleeve, the blocker ring and the gearwheel for the final time. It is shown that the solution to the direct dynamics synchronization problem for the generic synchronizer mechanism is not unique and it allows formulation different optimization problems. Mathematical statement of multi-objective Pareto optimal control problem for synchronizer mechanism is given. Within the proposed model of the generic synchronizer mechanism the time-comfort Pareto optimal control problem is considered. Assuming that the resistance torque on the synchronizer owing to the vehicle inertia, the drag torque, and the synchronizing torques at the contacting interfaces are substantially constant during the main phase of a synchronization process, the solution to the time-comfort Pareto optimal control problem has been obtained. It was shown that there exist the external control torque (or shift force) applied to the selector sleeve such that the synchronization of rotational speeds of the sleeve, the blocker ring and the gearwheel is guaranteed and the synchronization process is optimal both with respect to minimal possible synchronization time as well as lowest possible inertial load acting on the synchronizer mechanism. Analysis of the obtained Pareto solution is presented.