The identification of time series models of lower extremity EMG for the control of prostheses using Box-Jenkins criteria

The Box-Jenkins method of model identification and diagnostic checking was used on the EMG of the posterio-lateral thigh while contraction level, electrode position, and limb function were varied. Models remained exclusively autoregressive (AR) of order typically less than five for isometric contractions ranging from 25 to 50% of the maximum voluntary knee flexions and extensions, and for recording sites located within 30 mm of the original electrode position. Diagnostics performed on the residuals from AR(4) models indicate that a fourth-order model is adequate for myoelectric control applications under many circumstances.