Enhanced disturbance observer-based robust yaw servo control for ROVs with multi-vector propulsion

Purpose A novel proportional integral derivative-extended state disturbance observer-based control (PID-ESDOBC) algorithm is proposed to solve the nonlinear hydrodynamics, parameters perturbation and external disturbance in yaw control of remote operated vehicles (ROVs). The effectiveness of PID-ESDOBC is verified through the experiments and the results indicate that the proposed method can effectively track the desired attitude and attenuate the external disturbance. Design/methodology/approach This study fully investigates the hydrodynamic model of ROVs and proposes a control-oriented hydrodynamic state space model of ROVs in yaw direction. Based on this, this study designs the PID-ESDOBC controller, whose stability is also analyzed through Kharitonov theorem and Mikhailov criterion. The conventional proportional-integral-derivative (PID) and active disturbance rejection control (ADRC) are compared with our method in our experiment. Findings In this paper, the authors address the nonlinear hydrodynamics, parameters perturbation and external disturbance problems of ROVs with multi-vector propulsion by using PID-ESDOBC control scheme. The advantage is that the nonlinearities and external disturbance can be estimated accurately and attenuate promptly without requiring the precise model of ROVs. Compared to PID and ADRC, both in overshoot and settling time, the improvement is 2X on average compared to conventional PID and ADRC in the pool experiment. Research limitations/implications The delays occurred in the control process can be solved in the future work. Practical implications The attitude control is a kernel problem for ROVs. A precise kinematic and dynamic model for ROVs and an advanced control system are the key factors to obtain the better maneuverability in attitude control. The PID-ESDOBC method proposed in this paper can effectively attenuate nonlinearities and external disturbance, which leads to a quick response and good tracking performance to baseline controller. Social implications The PID-ESDOBC algorithm proposed in this paper can be ensure the precise and fast maneuverability in attitude control of ROVs or other underwater equipment operating in the complex underwater environment. In this way, the robot can better perform undersea work and tasks. Originality/value The dynamics of the ROV and the nominal control model are investigated. A novel control scheme PID-ESDOBC is proposed to achieve rapidly yaw attitude tracking and effectively reject the external disturbance. The robustness of the controller is also analyzed which provides parameters tuning guidelines. The effectiveness of the proposed controller is experimental verified with a comparison by conventional PID, ADRC.

A practical robust yaw servo architecture of ROVs by multi-vector propulsion and nonlinear controller

Multi-vector arrangement is a novel propulsion architecture for remotely operated vehicles (ROV) because of its high manoeuvrability and efficiency, but the influence on the ROV dynamics and attitude servo control has not yet been clearly evaluated. This study fully investigated the kinematic behaviours of a hexagonal multi-vector propulsion ROV with communication delay constraint and reduced the complex model for precision control system design. An enhanced model-based PI robust controller (EMPRC) based on the nominal model is proposed to solve the nonlinear hydrodynamics and communication problems with high performance yaw control, whose stability is also analysed. The conventional proportional-integral-derivative (PID) and integral separation PID are used in the experiments for comparison. The results indicate that the proposed EMPRC can effectively track the desired attitude and reject the external disturbances, while the conventional ones are limited by the nonlinear dynamics and communication delays. The improvement is 3x on average in terms of overshoot, settling time and anti-disturbance recovery time compared to conventional algorithms and proves this proposed novel EMPRC is a practical solution for multi-vector propulsion ROVs.