Tank Robot Self-Positioning Using Acoustic Shell Ranging
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Solution Overview
Problem
Existing methods for positioning robotic vehicles in cylindrical tanks require external transponders, which are cumbersome and prone to errors due to acoustic multipath and obstacles, and rely on inaccurate odometry for navigation.
Innovation Solution
The vehicle uses acoustic travel time data to determine its position within the tank by fitting a circle to measurements taken at different headings, combined with Doppler Velocity Log and inertial data for accurate dead reckoning, eliminating the need for external hardware and improving positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external transponders are used for positioning, then position determination can be achieved, but device complexity and operational constraints increase
Solution Approach 1:
The invention extracts the positioning function from the external transponder system and implements it using only the vehicle's own acoustic transceivers. The vehicle determines its position by measuring acoustic travel times to the tank shell and using the known tank geometry, eliminating the need for external transponders entirely.
Solution Approach 2:
The vehicle performs self-positioning using its own acoustic transceivers and the known geometry of the tank. The system is self-contained, requiring no external positioning infrastructure, and can independently determine its position and heading through acoustic ranging to the tank shell.
2Measurement precision
If transponders are installed around the tank, then positioning is enabled, but installation and recovery operations become cumbersome
Solution Approach 1:
The invention removes the transponder installation requirement entirely by using the vehicle's own transceivers and the tank's existing geometry. No external hardware installation or recovery operations are needed.
Solution Approach 2:
The tank shell itself serves as the positioning reference, eliminating the need for specialized transponder installation. The same tank structure that contains the liquid also provides the geometric reference for positioning.
3Measurement precision
If acoustic transponders are used, then position can be determined, but acoustic multipath and obstacles reduce reliability
Solution Approach 1:
The vehicle performs multiple acoustic ranging measurements to different points on the tank shell and uses a least-squares optimization approach. By taking more measurements than the minimum required and using optimization, the system achieves robust position determination that is resilient to individual noisy or obstructed measurements.
Solution Approach 2:
The system uses an optimization algorithm that iteratively refines the position estimate by minimizing the difference between measured acoustic travel times and those predicted from the known tank geometry. This feedback loop continuously improves position accuracy despite acoustic disturbances.
4Productivity
If encoder-based odometry is used for navigation, then position can be tracked, but accuracy is reduced due to slippage and calibration errors
Solution Approach 1:
The invention replaces the mechanical encoder-based odometry system with an acoustic ranging-based positioning system. Instead of relying on wheel encoders that are subject to slippage and calibration errors, the system uses acoustic travel time measurements to the tank shell, which are not affected by mechanical imperfections.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise positioning of the vehicle within the tank without external equipment, reducing complexity and operational constraints, and maintaining accurate navigation even in challenging acoustic environments.
Implementation Method 1
matching acoustic travel time data measured between the vehicle and the shell to this known geometry in order to determine the vehicle's position in the tank
Implementation Method 2
combined with Doppler Velocity Log and inertial data for accurate dead reckoning
Data Source
AI summary
A method and apparatus for positioning a mobile robot inside a vertical cylindrical Aboveground Storage Tank filled with a liquid is described. No additional hardware is needed other than the robot itself. The only piece of information needed is the tank's diameter which is known by construction. The robot carries proprioceptive sensors needed to propagate its position estimate as well as exteroceptive sensors needed to control the dead reckoning positional drift. Proprioceptive and exteroceptive data are merged using data fusion algorithms adapted to the sensor suite integrated in the vehicle, which can take different forms.