Foot Position Estimation During Standing Balance Using a Cane with Millimeter Wave Radar

Abstract

It is estimated that around 30% of the elderly fall each year worldwide. The use of assistive devices such as canes or walkers increases the stability of the elderly by increasing the area of the Base of Support. However, the fall rate of assistive device users is similar or even higher than of non-device users. Feet position while standing has been found to be a relevant indicator of postural instability in elderly patients. Therefore, the objective of this research is to develop a sensor system that can measure the feet position of cane users during standing balance. The proposed system could be used for balance training of cane users by providing feedback about their stability level in real time. Previous studies used pressure plates or camera-based systems, such as using the Microsoft Kinect, to estimate the position of the feet during standing balance. However, these systems have various limitations. On the one hand, pressure plates are not affordable due to its high price. On the other hand, current camera-based systems do not work well for assistive device users because these systems cannot detect the position of the assistive devices. In this research, we present an instrumented cane with a millimeter wave radar (AWR1642, Texas Instruments) that can estimate the position of the feet with respect to the position of the tip of the cane. The system was tested in an experiment where 2 young subjects stand for 3 seconds while using a cane in 9 different foot positions. The proposed system was able to estimate the foot position with an RMSE value of 29.92 mm. Although this result is better than the 10 cm average error obtained in similar studies using the Microsoft Kinect, the proposed system requires further improvement to also measure the foot position for other activities such as walking or sit to stand motion.