PSSEARCH provides predictive sea state estimation, coupled with closedloop feedback control for automated ride control. It enables a manned or unmanned watercraft to determine the 3D map and sea state conditions in its vicinity in real time. Adaptive path-planning/ replanning software and a control surface management system will then use this information to choose the best settings and heading relative to the seas for the watercraft.
PSSEARCH looks ahead and anticipates potential impact of waves on the boat and is used in a tight control loop to adjust trim tabs, course, and throttle settings. The software uses sensory inputs including IMU (Inertial Measurement Unit), stereo, radar, etc. to determine the sea state and wave conditions (wave height, frequency, wave direction) in the vicinity of a rapidly moving boat. This information can then be used to plot a “safe” path through the oncoming waves.
The main issues in determining a safe path for sea surface navigation are: (1) deriving a 3D map of the surrounding environment, (2) extracting hazards and sea state surface state from the imaging sensors/map, and (3) planning a path and control surface settings that avoid the hazards, accomplish the mission navigation goals, and mitigate crew injuries from excessive heave, pitch, and roll accelerations while taking into account the dynamics of the sea surface state. The first part is solved using a wide baseline stereo system, where 3D structure is determined from two calibrated pairs of visual imagers.
Once the 3D map is derived, anything above the sea surface is classified as a potential hazard and a surface analysis gives a static snapshot of the waves. Dynamics of the wave features are obtained from a frequency analysis of motion vectors derived from the orientation of the waves during a sequence of inputs. Fusion of the dynamic wave patterns with the 3D maps and the IMU outputs is used for efficient safe path planning.
This work was done by Terrance L. Huntsberger, Andrew B. Howard, Hrand Aghazarian, and Arturo L. Rankin of Caltech for NASA’s Jet Propulsion Laboratory.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
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NPO-47533
This Brief includes a Technical Support Package (TSP).
Predictive Sea State Estimation for Automated Ride Control and Handling — PSSEARCH
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Overview
The document outlines the research and development of the Predictive Sea State Estimation for Automated Ride Control and Handling (PSSEARCH) system, conducted by the Jet Propulsion Laboratory (JPL) under NASA's sponsorship. The primary goal of PSSEARCH is to enhance the navigation and control of high-speed watercraft, particularly unmanned surface vehicles (USVs), in varying sea states.
The research focuses on the implementation of a wide baseline stereo imaging system that has been extensively tested in diverse sea conditions at speeds up to 35 knots. This system utilizes a stereo algorithm developed by JPL to generate a three-dimensional (3-D) map of the environment in real-time, updating at a rate of 10 Hz. The 3-D mapping is crucial for predictive sea state estimation, allowing for the fusion of data from the stereo system with outputs from an Inertial Navigation System (INS) and other sensors, such as KA-band radar.
Key components of the PSSEARCH system include the derivation of a 3-D map, hazard extraction, and path planning. The 3-D map identifies potential hazards above the sea surface, while a surface analysis provides a static snapshot of wave conditions. The dynamics of wave features are analyzed through motion vector frequency analysis, which aids in understanding the sea state. This information is then integrated to create a dynamic traversability map that informs control surface settings for safe navigation.
The document emphasizes the importance of mitigating crew injuries caused by excessive heave, pitch, and roll accelerations during navigation. By employing advanced algorithms and real-time data processing, the PSSEARCH system aims to ensure safer and more efficient operations for high-speed vessels in challenging maritime environments.
Overall, the PSSEARCH initiative represents a significant advancement in maritime technology, combining sophisticated imaging and data fusion techniques to improve automated ride control and handling. The research findings have broader implications for various applications in aerospace and maritime industries, showcasing the potential for enhanced safety and operational efficiency in high-speed watercraft navigation.
