The hydrostatic transmission in working and transport vehicles, e.g. wheel loaders, graders and fork-lift trucks has the task of transferring and converting the power of the combustion engine onto the wheels of the vehicle in an optimal manner.
This paper describes control and regulating systems of hydrostatic transmissions in closed loop with automatic torque conversion and power limitation. The driving operation is similar to that of an automobile with automatic transmission, with speed signal via the accelerator and an electrically operated switch for selection of forward or reverse. By the use of infinitely variable displacement pumps and motors, a greater speed range is achievable. The acceleration, production rate and fuel consumption can be optimized for any engine power output by carefully matching the control and engine characteristics. This can be achieved either by hydraulic or electronic control systems.
A vehicle with large drive speed conversion range is possible by combining an automotive type hydrostatic transmission system with a mechanical power shift transmission.
Development ideas for hydrostatic transmissions with energy regeneration also will be presented.