Improved leg tracking based on estimated body direction using a laser range sensor

Abstract

Falling is a common problem in the growing elderly population and fall-risk assessment systems are needed for community-based fall prevention programs. In particular, the timed up and go test (TUG) is the clinical test most often used to evaluate elderly individual functional mobility in many clinical institutions or local communities. To evaluate the functional mobility during the TUG, some walking parameters such as stride length, step length and step width have to be measured. This paper presents a gait measurement system using a laser range sensor (LRS) (Laser-TUG system) for evaluating functional mobility in the TUG. The system tracks both legs and measures the foot contact positions to obtain walking parameters. However, both legs might be close to each other and one leg might be hidden from the sensor. This is especially the case during the turning motion in the TUG, where the time that a leg is hidden from the LRS is longer than that during straight walking and the moving direction rapidly changes. These situations are likely to lead to false tracking and deteriorate the measurement accuracy of the leg positions. To solve these problems, a novel data association method considering gait phase and body direction is proposed. We verify the proposed method for TUG tests with elderly people.