Abstract
In this paper, a soft-switching proximate time-optimal control (PTOC) is proposed based on the model-compensation extended state observer (ESO) and Takagi-Sugeno fuzzy switching, for the fast set-heading tracking of underactuated autonomous underwater vehicle (AUV). First, based on Pontryagin's maximum principle, a time-optimal control (TOC) law is derived for the first-order Nomoto model of the underactuated AUV. Then, a model-compensation active disturbance rejection control (ADRC) is developed; the outstanding characteristic is that the nonlinear heading dynamic model is compensated to a first-order Nomoto model rather than by a double integral system through implementing a model-compensation ESO (MC-ESO). The regular ESO is replaced with a reduced-order ESO (RESO) to reduce complexity, and the model-compensation RESO (MC-RESO) is designed by adding the known partial model to RESO. Based on the controller scaling method, a parameter self-tuning strategy is proposed for model-compensation ADRC (MC-ADRC) with changed plant parameters at different velocities. Finally, the soft-switching PTOC is developed for heading control, and the MC-RESO is adopted to estimate the unmeasured velocity and unknown total disturbances for feedback and compensation. The TOC with an unsaturated region (RTOC) is employed to enhance the robustness by using a switching region to replace the switching curve, and a soft-switching strategy between ADRC (near the origin) and RTOC (far from origin) is designed based on the Takagi-Sugeno fuzzy mode. Several simulations are carried out, the effectiveness of self-tuning MC-ADRC is verified, and the proposed soft-switching PTOC shows better performance compared with MC-ADRC.
Highlights
Autonomous Underwater Vehicle (AUV) has been widely used in marine development
In order to enhance the practical application of time-optimal control (TOC), soft-switching proximate time-optimal control (PTOC) is proposed for the heading control of underactuated autonomous underwater vehicle (AUV) with unmodeled dynamics and external disturbances
SELF-TUNING MODEL-COMPENSATION active disturbance rejection control (ADRC) According to reference [22], we propose a modelcompensation ADRC (MC-ADRC) for heading control
Summary
Autonomous Underwater Vehicle (AUV) has been widely used in marine development. AUV play an important role in many fields, such as ocean salvage, deep sea resources exploration, ocean hydrological observation, ocean surveying, and submarine pipeline maintenance, and have broad application prospects in the military field [1]. The existing studies on time-optimal heading control of AUV only have some applications lacking strict theoretical deduction, and the switching of control signal is based on the set threshold rather than the TOC switching curve. In order to provide theoretical support, the time-optimal heading control law is, to our knowledge, the first to be derived for the underactuated AUV heading with a first-order Nomoto model based on Pontryagin’s maximum principle. 3. In order to enhance the practical application of TOC, soft-switching PTOC is proposed for the heading control of underactuated AUV with unmodeled dynamics and external disturbances. B. TOC FOR FIRST-ORDER NOMOTO MODEL According to (4), the problem of time-optimal control for heading motion can be described as follows: tf. The system state can arrive at the origin with the similar control procedures when the initial state is within region S−
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