Ball Spin Estimation Using Aerodynamic Trajectory Matching
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Solution Overview
Problem
Existing methods for estimating the rotational velocity of a ball in table tennis systems, such as those described in Non-Patent Documents 1 and 2, face challenges in predicting the ball's trajectory with precision using a simple configuration, particularly when the ball is applied with spin, and require specialized equipment like high-speed cameras and marked balls.
Innovation Solution
A rotation estimation device and method that acquires state information including position and velocity of the ball, solves an aerodynamic model to predict future positions and velocities for various provisional rotational velocities, and selects the estimated rotational velocity minimizing the difference between predicted and measured positions, allowing for precise trajectory prediction without specialized balls or equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-speed camera and marked ball are used to measure rotational velocity, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/optical measurement system (high-speed camera tracking marked balls) with an aerodynamic model-based computational system. The rotation estimation section solves aerodynamic equations using measured position and velocity data to calculate rotational velocity, eliminating the need for physical markers and high-speed imaging equipment.
Solution Approach 2:
The patent introduces an aerodynamic model as an intermediary between the measured ball state (position, velocity) and the rotational velocity. Instead of directly measuring rotation, the system uses the aerodynamic interaction between the spinning ball and air flow to infer rotational velocity from trajectory deviations, acting as a mathematical mediator that connects observable quantities to the desired parameter.
2Device complexity
If aerodynamic modeling is performed with simple configuration, then device complexity is reduced, but trajectory prediction precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the rotation estimation section continuously refines the rotational velocity estimate by comparing predicted trajectory (from aerodynamic model) with actual measured trajectory. The system adjusts the rotational velocity parameter to minimize the difference between predicted and observed ball positions, achieving high precision through iterative optimization rather than complex hardware.
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
Enables accurate estimation of rotational velocity and precise prediction of the ball's trajectory using a simple configuration, capable of handling balls with spin, without the need for specialized balls or equipment.
Implementation Method 1
aerodynamic model
Implementation Method 2
aerodynamic model based on the measured position and the measured velocity of the ball at a first time point and on a provisional rotational velocity so as to perform processing to find a predicted position and a predicted velocity of the ball
Data Source
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AI summary
A rotational velocity of an incoming ball can be estimated using a simple configuration that does not require the use of a specialized ball, and a trajectory of a ball applied with spin can also be predicted with good precision using a simple configuration. A rotation estimation device 31 includes an acquisition section 33 and a rotation estimation section 34. The acquisition section 33 is configured to acquire state information including a measured position and a measured velocity of an incoming ball. The rotation estimation section 34 is configured to solve an aerodynamic model based on the measured position and the measured velocity of the ball at a first time point and on a provisional rotational velocity so as to perform processing to find a predicted position and a predicted velocity of the ball at a second time point different from the first time point for plural of the provisional rotational velocities, and so as to compute as an estimated rotational velocity either the provisional rotational velocity minimizing a difference between the predicted position at the second time point and the measured position at the second time point or a predicted rotational velocity at the second time point corresponding to the provisional rotational velocity minimizing the difference.