Toward an improved understanding of thruster dynamics for underwater vehicles

TLDR

These small, rapidly responsive ROVs and AUVs require precise motion control, highlighting a need for deeper understanding of thruster performance. The paper proposes a novel approach to modeling the four‑quadrant dynamic response of thrusters for ROV and AUV motion control. The model maps propeller blade lift and drag forces across four quadrants and couples them with motor and fluid dynamics, validated by experiments with triangular and square wave inputs. The model matches experimental data, predicts force overshoots during rapid command changes, and can improve dynamic thrust control on these vehicles.

Abstract

This paper proposes a novel approach to modeling the four quadrant dynamic response of thrusters as used for the motion control of ROV and AUV underwater vehicles. The significance is that these vehicles are small in size and respond quickly to commands. Precision in motion control will require further understanding of thruster performance than is currently available. The model includes a four quadrant mapping of the propeller blades lift and drag forces and is coupled with motor and fluid system dynamics. A series of experiments is described for both long and short period triangular, as well as square wave inputs. The model is compared favorably with experimental data for a variety of differing conditions and predicts that force overshoots are observed under conditions of rapid command changes. Use of the model will improve the control of dynamic thrust on these vehicles.