Design of an Unobtrusive Reaction Force Measurement and Its Application on Treadmills

Treadmills are frequently used training devices; however, inappropriate jogging habits may result in chronic sports injuries. This paper proposes a reaction-force-measuring system and realizes it on constructing treadmills to measure users´ feet reaction forces during their exercise period. The proposed reaction-force-aware treadmill can measure reaction forces of jogging subjects at speeds ranging from 1 to 16 km/h, without requiring the subjects to wear any measuring equipment. The feet-reaction-force-measuring system is mainly composed of load cell sensors, signal-amplifying circuits, and low-pass-filtering circuits. This measuring system cooperates with other components, i.e., a central controller, motors, and a liquid-crystal-display-based user interface to form the whole treadmill system. The electrical signals sensed by the load cells are transmitted to an 8052-based central controller through analog-to-digital converters. Then, the central controller transforms the electrical signals into force values. Apart from the literatures, the proposed work possesses three attractive features: 1) measuring reaction forces of users unobtrusively; 2) realizing all the required circuits as a highly integrated embedded system to achieve high efficiency and flexibility; and 3) providing a novel interactive interface between treadmills and users in terms of reaction force monitoring. From the experimental results, we can know that the measuring accuracy of the proposed work is within 1% due to the flexibility in adjusting the amplifying ratio for signal conversion. This work provides a precise, reliable, and economic reaction-force-measuring scheme for treadmill users. Such reaction force measurement enables users to be aware of the reaction forces exerted to them in terms of quantitative data and therefore keep themselves from related sport injuries in advance.