Curvature control of soft orthotics via low cost solid-state optics

A soft orthotic with position control enabled via embedded optical fiber is presented. The design, manufacture, and integration of both the pneumatically powered actuators and optical sensors are described. This orthotic actuator-sensor pair is self-contained and worn on a human finger. When un-powered, the elastomeric actuator allows facile movement and, when pneumatically actuated, the orthotic causes bending of the wearer's finger. Position control is achieved by measurement of signal intensity from a light-emitting diode (LED) input traveling through an embedded optical fiber—greater curvature results in increased light intensity. Both the static and dynamic states are monitored via the optical sensor and the prescribed curvatures are achieved accurately and with stability by a gain-scheduled proportional-integral-derivative (PID) controller implemented by applying pulse-width-modulation (PWM) signals to a solenoid valve to adjust the internal pressure of the actuator.