Swing Plane Reference Frame for Baseball Sensor Data Analysis
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Solution Overview
Problem
Current methods for analyzing baseball swings using motion sensors face challenges in interpreting sensor data due to the rotational symmetry of the bat, which complicates the transformation of data into a meaningful reference frame, leading to a lack of detailed and physically relevant metrics for swing analysis.
Innovation Solution
The method transforms sensor data from a local reference frame to a swing plane reference frame, defined by the bat's longitudinal axis, impact velocity vector, and orthogonal axis, allowing for the calculation of detailed swing metrics such as swing plane speed, time to contact, and swing tempo, and enables the creation of a database for performance rating and classification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sensor data is analyzed in the local sensor reference frame, then the data capture is simple and direct, but the interpretation becomes complex due to rotational symmetry and changing orientation
Solution Approach 1:
The patent applies the dynamics principle by transforming from a static sensor reference frame to a dynamic swing plane reference frame that adapts to the bat's changing orientation during the swing. The reference frame is dynamically adjusted based on the bat's longitudinal axis and impact velocity vector, allowing the system to maintain meaningful measurements despite rotational changes. This resolves the contradiction by making the reference frame flexible rather than fixed, enabling both simple data capture and meaningful interpretation.
Solution Approach 2:
The patent changes the reference frame parameters from a fixed sensor-based coordinate system to a swing-plane-based coordinate system defined by the bat's longitudinal axis and impact velocity vector. This parameter transformation allows the same sensor data to be interpreted in a physically meaningful way that accounts for the bat's rotational symmetry and changing orientation during the swing, resolving the interpretation difficulty while preserving the simplicity of sensor data capture.
2Reliability
If vector magnitudes are used to define swing metrics, then the metrics are invariant to rotations in the sensor reference frame, but the metrics lack detailed and physically meaningful information
Solution Approach 1:
The patent transitions from using only scalar vector magnitudes to using directional components along carefully chosen transformed axes in the swing plane reference frame. By introducing directional dimensions (along the bat's longitudinal axis, perpendicular to it in the swing plane, and orthogonal to the swing plane), the system recovers detailed physical information about the swing while maintaining invariance through the proper transformation to the swing plane frame. This resolves the contradiction by adding dimensional information without sacrificing reliability.
3Loss of information
If a swing plane reference frame is implemented, then detailed and physically meaningful swing metrics can be obtained, but the system complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining the swing plane reference frame based on the bat's longitudinal axis and the impact velocity vector before analyzing the swing metrics. This preliminary establishment of the reference frame simplifies subsequent measurements, as all sensor data can be projected onto this pre-established coordinate system. The reference frame is set up in advance based on known geometric relationships, reducing the complexity of real-time transformations while preserving detailed physical information.
Data Source
AI summary
A method for analyzing sensor data from baseball swings (or swings in similar sports) that transforms data into a reference frame defined by the bat orientation and velocity at impact. The swing plane defined by these two axes provides a natural and robust reference frame for physically relevant measurements of swing characteristics. Illustrative swing metrics derived from swing plane reference frame data include: swing speed, defined as a rotational rate within the swing plane; total swing angle, defined as the angular change within the swing plane; and swing tempo, defined as the percentage of peak swing speed achieved halfway through the swing. Analyzing these metrics from multiple swings across multiple users identifies factors that contribute to peak performance. Metrics may be combined into multidimensional feature vectors that characterize a swing; these feature vectors may be used to group swings into swing styles or to match swings against similar players.