Functional electrical stimulation is an assistive technique used to produce functional movements in patients suffering from neurological impairments. However, existing open-loop clinical FES systems are not adequately equipped to compensate for the nonlinear, time-varying behaviour of the muscles. On the other hand, closed-loop FES systems can compensate for the aforementioned effects by regulating the stimulation to induce desired contractions. Therefore, this work aims to present an approach to implement a closed-loop FES system to enable angular positional control during wrist flexion. First, a Wiener model describing the response of the wrist flexor to pulse width modulated stimulation was identified for two healthy volunteers. Second, a nonlinear PID controller (subject-specific) was designed based on the identified models to enable angular positional control during wrist flexion. Subsequently, the controller was implemented in real-time and was tested against two reference angles on healthy volunteers. This study shows promise that the presented closed-loop FES approach can be implemented to control the angular position during wrist flexion or a novelty of the work when compared with the existing work.