Active-passive motion compensation systems for marine towing

The dynamic behaviour of an active-passive motion compensation system for handling towed marine vehicles is examined, and a mathematical model developed. In the analysis, the passive system considered is pneumatic, while the active system is electro-hydraulic. The towed body is assumed to be a point mass subjected to hydrodynamic drag, and attached to the motion compensator by means of a linear spring representing the cable. It is not intended, in this project, to model the towed body in greater detail. The equations of the passive, active, and towed body systems are derived, and linearized to permit a relatively simple frequency-domain solution. A time simulation based on the nonlinear equations, including Coulomb friction in the compensator, is developed for use on an IBM Systeis/370 computer. A laboratory model is used to conduct experiments at three frequencies, and the results indicate good agreement between the linear, simulation, and real models. Extension of the equations to cover multi-frequency inputs, two-dircensiona1 towing cables, and slow-acting servovalves is also discussed to facilitate application to marine systems.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat