Underwater Vehicle Depth Tracking With Hierarchical Disturbance Rejection
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Solution Overview
Problem
Underactuated autonomous underwater vehicles face challenges in maintaining depth tracking accuracy due to underactuation, model nonlinearity, strong motion coupling, and external environment disturbances, making it difficult to reject disturbances effectively.
Innovation Solution
A method and system for hierarchical disturbance rejection depth tracking control, which involves determining navigation information, converting depth tracking errors into desired pitch angles using an adaptive line-of-sight guidance law, and employing an active disturbance rejection-sliding mode pitch tracking control law with an extended state observer and sliding mode feedback control to calculate an elevator angle, thereby overcoming observation errors and improving depth tracking accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional depth tracking control methods are used, then the control system is simple, but depth tracking accuracy deteriorates due to disturbances
Solution Approach 1:
The control system is segmented into multiple independent modules: extended state observer for disturbance estimation, adaptive line-of-sight guidance for trajectory generation, and sliding mode control for execution. Each module handles specific functions, allowing complex disturbance rejection without overwhelming system complexity.
Solution Approach 2:
The extended state observer acts as an intermediary that estimates composite disturbances (including model uncertainties and external disturbances) and feeds this information to the sliding mode controller, enabling accurate disturbance compensation without direct measurement of all disturbance components.
2Ease of manufacture
If underactuated vehicle structure is used, then manufacturing simplicity is improved, but depth tracking reliability deteriorates due to limited control authority
Solution Approach 1:
The control approach changes parameters dynamically through adaptive line-of-sight guidance that adjusts the look-ahead distance based on vehicle speed and depth error, allowing the underactuated vehicle to achieve reliable depth tracking by optimizing control parameters rather than adding actuators.
Solution Approach 2:
The extended state observer continuously monitors depth errors and estimates disturbances, providing real-time feedback to the sliding mode controller. This feedback mechanism compensates for the limited control authority of underactuated vehicles, maintaining reliable depth tracking without additional actuators.
3Object-affected harmful factors
If adaptive line-of-sight guidance with adaptive parameter is used, then motion disturbance rejection is improved, but calculation complexity increases
Solution Approach 1:
The adaptive parameter in the line-of-sight guidance law changes dynamically based on vehicle speed and depth error magnitude. This dynamic adaptation allows the guidance law to reject motion disturbances effectively while keeping calculations manageable by adjusting complexity according to operational conditions.
4Measurement precision
If extended state observer with observation error compensation is used, then disturbance observation accuracy is improved, but control law design complexity increases
Solution Approach 1:
The extended state observer performs preliminary disturbance estimation before the sliding mode controller executes correction. By pre-estimating composite disturbances including observation errors, the control law design is simplified as it only needs to handle the residual errors rather than all uncertainties from scratch.
Data Source
AI summary
The disclosure provides a method and system for hierarchical disturbance rejection depth tracking control of an underactuated underwater vehicle, and the depth tracking of the underactuated underwater vehicle is divided into kinematic layer guidance and dynamic layer pitch tracking. Adaptive line of sight guidance is used in the kinematic layer to convert a depth error into a desired pitch angle and to estimate and compensate an angle of attack to reject disturbance introduced by an unmeasurable true angle of attack. Based on the above, in the dynamic layer, the active disturbance rejection sliding mode pitch tracking method is used to observe a composite disturbance including an unknown dynamic model and an environmental disturbance by using the active disturbance rejection framework. The model is compensated as a unified integral series type, a sliding mode control law is finally designed to resist an observation error, and a control elevator angle is calculated.