Model-Based Simulation Approach to Reduce Jerk Issue in Power Shuttle Transmission (PST) Tractor

Nowadays, tractors are frequently used with front-end loaders, dozers and backhoes to cater to various non-agricultural and construction application needs. These applications require frequent shifting of gears due to the constant need for a tractor's forward/reverse direction of motion. Hence, the tractors are fitted with a power shuttle transmission (PST) to cater this need. Power-shuttle transmission (PST) development is a design process that incorporates multiple disciplines such as mechanical, hydraulics, controls and electronics. This paper presents a simulation-based approach to model the power shuttle transmission of the tractor. Firstly, individual components of PST are modelled in detail and then integrated with the complete tractor model. For this, GT-Suite has been used as a simulation platform. The main objective of this simulation was to optimize pressure modulation curves (valve opening and closing characteristics of PST valve) to have less jerk (better drive-ability), which otherwise would require trial and error method tractor testing. This trial and error method of testing is more time-consuming and costly. The developed simulation model is used to study wet clutch characteristics and acceleration (jerk) values during motion reversal operation. Results of the modelled tractor are compared with actual test results by validating them with the data received from an actual instrumented tractor. Study shows that modelled tractor acceleration behaviour during motion reversal operation resembles an actual instrumented tractor's acceleration behaviour with more than 80% accuracy. Iterations were performed on a validated model to optimize pressure modulation curves of the PST system, thereby reducing acceleration (jerk) of the tractor during forward/reverse motion reversal operation. Also, the study presented in this paper is beneficial for the component sizing of the PST system used in the tractors. Also, the need for tractor testing was minimized.