Integrated Guidance Control for Underactuated Vehicle Stability
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Solution Overview
Problem
Unmanned vehicles lack nonlinear stability and robust autonomous attitude control, especially in beyond visual-line-of-sight operations, which can lead to failure and crashes due to external disturbances like wind.
Innovation Solution
A control system for underactuated vehicles with multiple thrusters, providing nonlinear stability and autonomous attitude control. The system includes a controller that determines a thrust vector and direction to track a position trajectory, and calculates a control torque for attitude control, ensuring robustness and easy computerized integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional control systems are used for unmanned vehicles, then the system is simpler to implement, but the vehicle lacks nonlinear stability and robustness to external disturbances
Solution Approach 1:
The control system is segmented into distinct functional modules: a guidance module that generates desired trajectories, an attitude control module that processes attitude errors, and a thrust allocation module that distributes control efforts. This modular segmentation maintains nonlinear stability while making the complex control system more manageable and implementable.
Solution Approach 2:
The control system employs feedback mechanisms where the current attitude and angular velocity are continuously measured and compared with desired values. The attitude error and angular velocity error are fed back through control laws that guarantee nonlinear stability, allowing the system to robustly reject external disturbances while maintaining reliability.
2Adaptability or versatility
If the vehicle operates in beyond visual-line-of-sight conditions, then the operational range is extended, but the vehicle becomes more vulnerable to external disturbances like wind
Solution Approach 1:
The control system applies preliminary anti-action by using the nonlinearly stable control laws to anticipate and counteract external disturbances before they significantly affect the vehicle. The control torques are designed to proactively compensate for wind and other environmental factors, enabling reliable beyond visual-line-of-sight operations despite the increased vulnerability to disturbances.
Solution Approach 2:
The control system provides beforehand cushioning through its robust nonlinear stability properties, creating a protective buffer against external disturbances. The control laws are designed to maintain stability margins that cushion the vehicle from the full impact of wind and other environmental factors during extended operations.
3Manufacturing precision
If the controller continuously adjusts thrust vectors and attitude trajectories, then the vehicle can accurately track desired paths, but the control inputs may become unbounded or discontinuous
Solution Approach 1:
The control system employs dynamic adjustment strategies where the thrust vector and attitude trajectory are continuously adapted based on current state errors. The control laws ensure that these dynamic adjustments remain bounded and continuous by using smooth functions of the tracking errors, achieving both precise trajectory tracking and stable control input composition.
Solution Approach 2:
The controller changes parameters smoothly by using continuous functions of the position and attitude errors to generate control commands. The thrust magnitude and direction are adjusted through parameter transformations that ensure continuity and boundedness, maintaining both tracking precision and control stability simultaneously.
Data Source
AI summary
An integrated guidance and feedback control scheme for steering an underactuated vehicle through desired waypoints in three-dimensional space. The guidance and control algorithm takes as an input the desired trajectory for the translational motion that passes through the given waypoints, and autonomously generates the desired trajectory for the attitude based on the desired thrust direction to achieve the translational motion trajectory. A feedback control law is obtained to steer the underactuated vehicle towards the desired trajectories in translation and rotation.