Figure 3.

Iterative learning control scheme used for ES showing model of the combined human arm and mechanical support used in the controllers. The subscript ‘k’ denotes the iteration number, $\Phi (t)$ is the vector of human arm joint angles, ${\Phi }^{*}(t)$ is the vector of joint angles that the arm is required to follow, u(t) is the vector of stimulation pulsewidths applied to each muscle, and v(t) is the signal calculated by ILC to enforce tracking of ${\Phi }^{*}(t)$ by $\Phi (t)$ (ILC also adjusts parameters in the feedback controller). The remaining parameters are described in the text, with full details given in [22]. Note that patient’s voluntary effort can be included as an external disturbance [36].