Abstract
Underwater thermal vehicles, as ocean observation tools, are frequently affected by environment disturbances such as waves and currents, which may cause degradation of the observation accuracy of the vehicles. Consequently, it is important to design a controller for a vehicle that can resist ocean disturbance. In this study, an underwater thermal vehicle principle is introduced, and the mathematical model is established in the vertical plane motion. On this basis, an adaptive digital disturbance suppression control method is proposed. For known disturbance parameters, this controller could compensate for external disturbances by pre-setting control parameters using the internal model principle and parameterizations method. For the case where the disturbance parameters are unknown, disturbance parameter estimation method based on forgetting factor least-squares method is proposed to transform the unknown parameter disturbance into a disturbance with known parameters, which is then suppressed by the adaptive digital disturbance rejection control approach. This solution could effectively solve the challenges caused by parameter uncertainty and unknown time-varying ocean external disturbances. Finally, simulations are carried out for the Petrel underwater thermal glider as an example. The simulation results show the proposed control method’s superiority and inherent robustness.
Highlights
The ocean plays the very important role in maintaining the ecological environment of the earth
V1 and v3 respectively represent the axial, longitudinal velocity of underwater vehicle, m f 1, m f 3 are added mass and slider mass, ms3 is the stationary body mass of vehicle, PP3 is the vertical moment of inertia. s and r are the position of vehicle in the vertical plane, in which the slider is fixed in the axial movement position, so r can be set as a constant. g is gravity acceleration, u is the power for the axial movement of the slider, which is obtained from the motor driving the movement of the slider
An adaptive control strategy based on the internal model principle was proposed for the ocean thermal underwater vehicle’s pitch angle control problem
Summary
The ocean plays the very important role in maintaining the ecological environment of the earth. Huang et al [15] proposed a self-optimal control method This controller can be used to effectively compensate for external disturbances, which may adversely affect the underwater thermal vehicle’s pitching attitude maintenance or switching. Compared to adaptive frequency estimators [19,37,38,39] and adaptive observers [40,41,42], the robust digital controller approach based on parameter identification is easier to deal with random signals and un-modeled dynamics in real-time for multiple frequencies. It can be applied in the application of underwater vehicle disturbances rejection.
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