Study on the control methods of a water hydraulic variable ballast system for submersible vehicles

The water hydraulics is a competitive mechanism to adjust the ballast water and also is the only choice for ultra-deep sea applications. In order to improve the control performance and reduce the energy consumption of the water hydraulic variable ballast system (WHVBS), a novel type WHVBS, which introduces a servo motor to drive the pump and uses four fast response direct-acting solenoid valves to control the water flow direction, has been proposed. The proposed WHVBS has two novel flow control modes: changing the speed of servo motors (pump controlled mode) or changing the opening time of solenoid valves (valve controlled mode). The mathematical model of WHVBS was built up for the purpose of predicting the flow rate under both control modes. A generalized predictive controller with forgetting factor recursive least square (FFRLSGPC) was proposed for WHVBS to improve the control performance. Finally, based on the tracing experiments performed on a WHVBS experiment platform, the comparative discussion of control performance and the analysis of energy efficiency were presented. The experimental results show that the mean tracing error can be maintained within 0.27% by the proposed FFRLSGPC in valve controlled mode and the pump controlled mode is an energy-efficient control method.