Microprocessor-Based Biofeedback Cane System

A Microprocessor-Based Biofeedback Cane System

Patrick Moran, Khomeshwari Acharya, Hongsheng Zhu*, Jacqueline J. Wertsch*, Gerald F. Harris Dept. Biomedical Engineering, Marquette University 1515 W. Wisconsin Ave., Milwaukee, WI 53233 and*: Dept. Physical Medicine and Rehabilitation, Medical College of Wisconsin Milwaukee, WI

ABSTRACT - A system has been developed to measure vertical forces between a cane and ground while walking. An audio alarm sounds when applied forces are not within pre-determined limits. The system employs two types of sensors attached to the cane, a force sensing resistor (FSR, Interlink, Santa Barbara, CA.) and a strain gage bridge (Mlcromeasurements Group, Rallegh, NC.). The sensors provide input to the portable data acquisition circuit which is designed to perform analog to digital conversion and store the The force data using a calibrated look-up table. alarm is controlled on the basis of look-up table values. Thresholds for the alarm are set as a ratio of subject weight which is input to the system prior to use. High-speed CMOS technology and the Motorola 68HC11 microcontroller were used in the design to limit power consumption.

Audio Feedback

St rain Gages FSR

Weight Input

I. INTRODUCTION Canes are often used as rehabilitative aids to redistribute forces during ambulation. Proper prescription of the assistive device and correct training in its use are paramount to the rehabilitative process. Unfortunately little quantitative information is available on cane loading. Force interactions at the hip and knee, Cane with cane use, have been studied [1-2]. have also been measured using pressures instrumented canes or force plates [3]. None of these systems included a feedback system to the patient, however. Such feedback, with proper training, could help insure more optimal cane loading. Other feedback systems have been developed previously, although these systems used cane torque for the feedback signal [4] or limited weight...