AUTOMATIC LOAD CONTROL SYSTEM FOR HYDRAULIC ROTARY POWER ABSORBERS

An automatic load control system is described for controlling the retarding force characteristics of a rotary power absorber such as a dynamometer in which the absorbed torque varies with the level of fill of the working fluid. The load control system includes a speed signal generator such as a tachometer coupled to the dynamometer for generating a speed signal representative of the rotational speed. A torque signal generator in the form of a strain gauge or other transducer is connected to the dynamometer to provide a torque signal representative of the absorbed torque. Load and unload control mechanisms such as electrically operated valves are connected between the power absorber and a source and sink for controlling the flow of working fluid into and out of the absorber and thereby the value of the absorbed torque. A flow control means controls the valves in accordance with the values of the speed and/or torque signals to thereby control the level of working fluid within the absorber to cause the absorbed torque to vary in a predetermined manner, e.g., as the square of the speed changes. An adjustable torque means is coupled to the flow control means for adjusting the absorbed torque to a selected value at a given speed. The dynamometer may also be provided with a plurality of flywheels and electrically operated means for selectively engaging one or more flywheels with the absorber rotor to simulate the inertia on an engine or vehicle under test.