Fig 1.
Demonstration of the hitting process of table tennis on racket.
The bottom line shows the interaction of racket and ball with different rotation. The out-of-plane rotation generated force is worked on sensors on a line getting across the hitting position, while the in-plane rotation causes the generated signal not only on a row or in a column.
Fig 2.
Demonstration of the existing point array design and proposed row-column piezoelectric sensing array design.
The bottom figure is cross-section demonstration of the layered sensing structures on table tennis racket.
Fig 3.
The picture of the fabricated on-racket hit sensing system.
Fig 4.
Demonstration of the force-generated signal calibration test and the captured signal from top and bottom layer.
Fig 5.
Illustration of the structure of the sensor array applied in the real monitoring (left) and its ability for multipixel detection.
The array contains 5 × 5 sensors, which is able to monitor 25 sensing positions. The pressure stimuli (top right) and the corresponding real-time signal (bottom right, unit: V) from the sensor array show four hits from table tennis at different time, marked with different colors.
Fig 6.
Simulated z-direction volume stress distribution on an elastic material (rubber) with out-of-plane force and in-plane force as input: A. demonstration of the decomposed out-of-plane input rotation force.
B. demonstration of the decomposed in-plane input rotation force. C. volume stress distribution with out-of-plane force input. D. volume stress distribution with in-plane force input.
Table 1.
Comparison of the different reported works for sport monitoring, especially table tennis monitoring.
Fig 7.
Experimental time-dependent electronic signal and extracted peak-peak value of the rotated table tennis ball hitting test.
Three hits are recorded, where the first one is an out-of-plane rotation and the other two are in-plane rotation hitting.