SIDAC class of Hydrostatic Transmission Controls

In a transmission system with a diesel engine, a variable displacement pump, a fixed or variable displacement motor and a load unit, any control interface should handle the degrees of freedom of both engine and hydraulic units through proper generated pilot signals starting from the directives issued by a supervising level. A special class of controls (SIDAG) calls for a single directive and handles the power variables of the system, giving the transmission additional automatic capabilities, which makes them specially suited for the locomotion of wheeled vehicles. Two implementations are possible: primary controls (variable pump only) and secondary controls (variable pump and motor). After a summary of some candidate architectures of the former, a number of arrangements of the latter are introduced and compared in respect of their steadystate and dynamic characteristic. The peculiarities of secondary control arrangements are highlighted using a simple and consistent tool for further investigations.