POWER TRANSMISSION

An electro-hydraulic servo control system which has N dynamic state variables and includes a servo actuator adapted to variably position a load mass. An actuator control system includes sensors coupled to the actuator for providing indications of X measured state variables, such as actuator position and/or velocity, and a digital observer responsive to the X measured actuator variables for estimating the remaining N-X variables at the actuator such as velocity and/or acceleration. Signals indicative of measured and estimated state variables are fed to a comparator together with a state command signal, for obtaining a difference or error signal to provide a control input to the actuator. The observer electronics include digital computation means suitably programmed to estimate N state variables as solutions to N linear equations for N unknowns. Equation constants, which are functions of actuator and driven mass physical characteristics, are entered through operator-adjustable resistors or are down-loaded from a remote system into storage registers.