MODELING AND DYNAMICS OF EPITROCHOID GENERATED ORBITAL ROTARY PISTON LSHT HYDRAULIC MOTOR - A BONDGRAPH APPROACH

In this paper the dynamics of epitrochoid generated Orbital 'rotary pi ston machine' (ROPIMA) type 'low speed high torque' (LSHT) hydrostatic unit are studied. The complex variation of the volume of a chamber of such a machine with shaft rotation along with dynamic characteristics of the rotary flow distributor valve, interchamber leakages, fluid co mpressibility, inertia of orbiting rotor, etc. demand a structured app roach to arrive at its mathematical model. In conventional approaches the system morphology gets obscured as the mathematical model is arriv ed at. Owing to the lack of modularity the errors in deduction of equa tions may remain eclipsed. Bondgraphs provide a structured approach to model engineering systems. The bondgraph model of the LSHT orbital mo tor is presented in this work. Relevant simulation results are discuss ed. The mathematical model was found to be stiff and its integrations were costly and time consuming. A tractable approach to estimate its s teady state behavior is suggested and validated. The authors believe t hat such an approach would be suitable in the initial stages of design of such machines and in the development of control systems where thes e machines are used as actuators.