Abstract
This paper deals with lumped parameter approximation of pipeline dynamics in a hydraulic servosystem for lossless and steady laminar friction models. The pipeline length valid for the approximations is investigated to reduce CPU time of simulation. An excellent approximation can be done by an asymmetrical π-type lumped circuit whose admittance is divided appropriately into the control valve and cylinder sides to fit the critical point of stability for the lumped system with that for the distributed one. The optimum dividing ratios is essentially constant regardless of change in the pipe radius or the load mass, if so small pipe is not used.
