Adaptive Autopilot Control for Stable GPS Track Keeping
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Solution Overview
Problem
Conventional autopilot systems for mobile structures, such as watercraft and aircraft, face instability and inaccuracies due to phase lag issues in cross track error feedback loops, exacerbated by noise and delay in GPS signals and variable vehicle responses, leading to sluggish and unpredictable track keeping, especially during large turns. Additionally, these systems often require extensive configuration for each vehicle type, making them costly and inefficient for multiple applications.
Innovation Solution
An adaptive directional control system utilizing high-quality turn rate signals and GPS data to generate high-bandwidth cross track signals, combined with an adaptive nominal vehicle model-based controller, which includes orientation, acceleration, and position sensors to provide accurate and stable directional control. This system adjusts steering actuator operations based on real-time feedback, limiting control signals within actuator rate limits and integrating with user interfaces for responsive control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional reference path tracking algorithms adjust heading as a function of cross track error, then the system can provide automated directional control, but the system becomes inherently unstable due to double integration causing 180° phase lag
Solution Approach 1:
The patent implements a feedback mechanism that uses high-quality turn rate signals and GPS data to generate high-bandwidth cross track signals. The adaptive controller continuously adjusts the control signal based on real-time feedback from sensors, compensating for phase lag and maintaining stability through dynamic adjustment of control parameters.
Solution Approach 2:
The system employs an adaptive nominal vehicle model-based controller that dynamically changes control parameters based on real-time vehicle state and environmental conditions. This allows the controller to adapt to varying vehicle responses and maintain optimal performance across different operating conditions, resolving the stability issue caused by fixed-parameter conventional algorithms.
2Loss of information
If GPS data is used for position feedback, then the system can provide navigation capability, but the system suffers from high noise levels and signal delays of 5 seconds or more
Solution Approach 1:
The patent introduces high-quality turn rate signals and acceleration sensors as intermediary measurement devices that provide more accurate and timely data about vehicle motion. These sensors act as mediators between the GPS position data and the control system, filling in the gaps during GPS update intervals and filtering out noise through high-bandwidth signal generation.
Solution Approach 2:
The system replaces reliance on noisy GPS position measurements with direct mechanical sensing through turn rate gyros and acceleration sensors. This substitution provides higher bandwidth and lower noise measurements of vehicle motion, eliminating the 5-second delay inherent in GPS processing and filtering.
3Reliability
If the autopilot system is designed for a particular vehicle type, then it can provide optimized control for that vehicle, but manufacturing costs increase due to extensive testing and adjustment procedures for each vehicle
Solution Approach 1:
The patent implements a dynamic adaptive controller that automatically adjusts its parameters based on real-time vehicle response characteristics. Instead of requiring static configuration for each vehicle type, the system dynamically learns and adapts to the specific vehicle's behavior during operation, eliminating the need for extensive manual testing and adjustment for each vehicle while maintaining optimized control.
Solution Approach 2:
The adaptive nominal vehicle model-based controller performs self-configuration by automatically identifying vehicle parameters and optimizing control gains based on observed vehicle responses. This self-service capability eliminates the need for external testing and adjustment procedures, allowing the same controller hardware to be efficiently manufactured and deployed across multiple vehicle types without increasing manufacturing complexity or cost.
Data Source
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AI summary
Autopilot systems and related techniques are provided to improve the ability of mobile structures to maintain a desired reference path (e.g., to keep a desired track and/or to follow a desired contour). In various embodiments, a high quality turn rate signal and GPS based signals are used to generate high bandwidth cross track/contour errors and other associated signals. An adaptive controller uses the generated cross track/contour signals to provide robust track keeping and/or contour following in the directional control of a mobile structure. Techniques are also provided for systems and methods to provide directional control for mobile structures.