State variable approach to the function of the muscular system supporting the hip joint during normal walking

Analogue computer system for the evaluation of hip joint moments during normal walking

Hip joint moments were determined by analogue computer techniques, using as inputs the angles formed by body segments during normal walking. The control algorithm was based on the division of the walking cycle into six stages; each activated by contact of heel, mid-foot and fore-foot. The problem of the accuracy of double differentiation was overcome by means of two filters which amplify the gain at the basic frequency of the walking cycle, while reducing it above 10 Hz. The analogue model gave reasonable results, suggesting that it could be used as an input to a real time microcomputer-based adaptive control system for the maintenance of hip joint balance in an amputee during walking.