Automatic starting control of tractor with a novel power-shift transmission

In this paper, a novel power-shift transmission using hydro-viscous drive (HVD) technology is proposed to improve starting comfort without affecting the drivetrain service life of a tractor. The tractor equipped with this novel power-shift transmission can realize stepless speed-regulation crawling. The structure of the tractor drivetrain, transmission scheme, gear ratios, and parameters of the HVD device are designed based on the operation requirements. The dynamical model of the drivetrain for tractor starting is established, and the control strategy for automatic starting of the tractor is developed to match this novel power-shift transmission. To verify the availability and effectiveness of this novel transmission in tractor automatic starting, a simulation model is established and the automatic starting processes under various driver's intentions are simulated. Accordingly, the simulation results show that this novel power-shift transmission cooperated with reasonable automatic control strategy can achieve a better starting effect. The tractor can realise 'soft starting' with small jerk as well as high comfort under starting intention of the driver. Moreover, the HVD device only works in the stage of hydro-viscous friction, which can prevent the failure of transmission caused by large temperature increase and contact friction.