In this paper, we present an approach for ball speed and spin estimation in table tennis based on a single racket-mounted inertial sensor. We conducted a research study comprising eight subjects performing different stroke types resulting in various ball speeds and spins. All ball-racket impacts were recorded with a high-speed camera for further evaluation. Firstly, several assumptions and simplifications of the unknown initial ball properties and the movements of player and racket had to be made. Secondly, the racket blade velocity right after impact was calculated. This was combined with a rebound model between the ball and the rubber to predict the speed and spin of the ball. Overall, the ball speed of strokes with forward spin could be estimated with an accuracy of 79.4% and for strokes with backward spin with an accuracy of 87.4%. The spin was estimated with an accuracy of 73.5% and 75.0%, respectively. To our knowledge, this contribution is the first attempt to estimate characteristics of rebounded balls with a single racket-mounted inertial sensor considering unknown initial conditions and constraints.
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