The dynamic controls of a hydraulic press by controlling the pump motor
Because of the need to control power, a research project to control a 25 ton Walbash hydraulic press was undertaken. A pump-motor control scheme was selected to control this press, after considering adaptability, cost, and time response of the system, over a servo valve control system. The analytical analysis of the pump-motor control scheme assumed linear characteristics for the press and motor which lead to a differential equation to describe the system: J/K nd V r(t)/dt-(K iK pK l/R a-K i???/R aK n r(t) = K iK p/R a(t)  where J is the inertia, R ais the armature resistance, K iis the stall torque of the motor. K nis the proportionality constant of the press, K pis the motor controller constant, K 1is the position transducer constant V ris the velocity of the ram, and e(t) is the input signal to the control system. The actual control system was installed on the Walbash press using analog to digital and digital to analog converters for computer linking. The control system produced a completely computer controlled press, except for the extra functions of the press, such as temperature control, which were not disturbed. The control system worked satisfactory but not without a number of problems: numerical differentiation errors, magnitude of the velocity instabilities, and hydraulic inconsistencies. The press's futures is dependent on the user's tolerance to these errors.
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:hydraulic press pump motor walbash
Date of Publication:01/01/1987