The effect of control to the efficiency of the hydrostatic transmission

This study deals with the effect of the control to the efficiency of the hydrostatic transmission (HST). The control of HST consists of two levels : The control of individual components The control of the whole system Traditionally we know the efficiencies of hydraulic pump and motor as a function speed, pressure and displacement separately. In this research work statistical methods have been used to analyze the effects of the earlier mentioned variables and their interactions to the efficiencies of hydraulic pump and motor. In the paper the efficiency behaviour of hydraulic pump and motor is compared. The studied hydraulic pumps and motors are closed loop circuit components. As a result it can be said that the efficiency behaviours of the hydraulic pump and motor are not similar. Pressure level, speed and displacement of the unit have in some cases remarkable interactions to the efficiencies of pump and motor. The control of individual components (diesel engine, hydraulic pump and motor) has to be adaptive if the smooth and fast step response of the units is the goal. In this study the controllers of the units are represented. The control is in this case purely dynamic. The second stage of the control is the whole system control. This controller gives the command values to the unit controllers. With this whole system control one can effected to the efficiency of the whole system. ht least this strategy can affect to the efficiency of the system at partly loaded cases dramatically. The efficiency can be raised from 30 % to 60 %. The control is in this case both dynamic and static. In this paper the effect of the control strategy to the efficiency of the HST system will be shown. The study is done through simulations.