MODELING OF CYCLIC GEARSHIFTS IN AUTOMATIC TRANSMISSIONS FOR VEHICLES.

One of the most effective ways to improve the efficiency of vehicles is to reduce the engine operating range by increasing the number of overall gear ratios in automatic transmissions. In this case, the step between the gear ratios decreases. It leads to decreasing the difference between program values of speeds, at which the gearshifts occur. It is one of the reasons for cyclic gearshifts (oscillating shifts) between two adjacent gear ratios, which leads to passenger discomfort, reduced transmission resource and increased loads on the transmission elements. High-frequency oscillating gearshifts can occur in the case of self-oscillation of the output shaft of the gearbox caused by gearshifts. With significant amplitude of speed fluctuations, the control system will shift to the previous gear. Low-frequency oscillating gearshifts are associated with the inability to maintain the selected speed of the vehicle in the zone, where its values are close to the values of speeds shifting to the adjacent gear ratios. Such wrong gearshifts occur due to frequent changes in external traffic conditions, for example, on hilly or winding roads. The article is devoted to the analysis of these dynamic processes and their simulation. The dynamic model of the automatic transmission is considered. The model reflects the most essential properties of the transmission: inertia of the transmission elements, stiffness and damping, program values of the gearbox output shaft speeds, at which gearshifts occur. The results of dynamics simulation of simplified transmission models with automatic transmission are presented. The dynamic model can be used to develop intelligent control systems for automatic transmissions, for simulation of various driving conditions of the vehicle and to calibrate the engine and transmission. [ABSTRACT FROM AUTHOR]