Figure 4

Sinusoidal synergy controller block diagram. PID sliding mode control diagram for the sinusoidal synergy controller. A, b, and ϕ are the joint amplitudes, position offsets, and phase offsets, of the sinusoids in the controller, respectively. These sinusoids are used to drive each joint of the Shadow Hand individually using only a single EMG input. ν is the slope of the sliding manifold. Two different EMG mapping methods were evaluated by five individuals with a hand absence as the input to the synergy controller, E _M . With the Rhythmic EMG mapping method, E _M  = E _R , and a switching function δ determines whether the EMG signals are mapped to the contact or return strokes of the synergy (8), Figure 3. δ is dependent upon the position of the reference joint, x_{F 2} (Table 1). In the Threshold method, E _M  = E _T , and when either the EDC or FCR muscles are above a predetermined threshold, γ, E _M within the family of sinusoids (5) is incremented or decremented to produce screwing or unscrewing motions as shown in Figures 6 and 7. The speed of the synergy is constant and determined solely by ω for the Threshold method. For the Rhythmic method, the speed of the synergy is affected by ω and also by the rate of operators’ muscle contractions.