Effects of unsteady lift and cable tension on design of a control system of a towed vehicle

A high speed towed vehicle, "Flying Fish" is being developed to measure chemical and physical properties of the ocean. To design a motion control system for the vehicle an accurate mathematical model of motion of the towing cable is essential because the cable length must be very long to meet safety requirements and to expand the observation area. We report a technique for design of a motion controller which uses a mathematical model based on mode expansion by eigenfunctions. This provides an accurate mathematical model of the cable motion which has fewer parameters than other methods. This simple cable model enables us to apply an advanced control theory to the motion control. Numerical simulations by the lumped mass model and by the new method are compared and difference of the cable model is discussed. Furthermore, unsteady effect on lift of the wings is investigated. Numerical simulation is carried out which includes the unsteady effect and problems in the design of a motion controller are discussed.