Field experiments on motion control systems of the towed vehicle 'flying fish'

A high speed towed vehicle 'Flying Fish' is being developed to measure chemical and physical properties of the ocean. The motion control system is based on the PID (proportional integral differential) control method or the LQI (linear quadratic integral) control method. LQI control system required an accurate mathematical model of the vehicle's motion, and the model therefore, was improved through field experiments. Field experiments were carried out in the summer of 1997 in the Japan Sea. The hydrodynamic coefficients were estimated using the measured vehicle's motion, ship's motion and tension of the towing cable. Results of the field experiment were compared with numerical simulations to research the accuracy of the model used in the design stage of the control system. The results of numerical simulation using the hydrodynamic coefficients obtained from the field experiment show good agreement with the field experiment. Some problems on the design of the motion control system are also discussed.