Innovative strain measuring device with flex sensor for twisted and coiled actuator and dexterous hand application

The displacement of twisted and coiled polymer (TCP) actuators, a key physical characteristic, can be measured using a lightweight method, thereby improving the TCP responses and applications in the robot control. This work presents a strain measurement device based on the flex sensor and the hinge links applied in the displacement measuring of the TCP. The bent angle from the sensor affixed to the hinge is converted to the displacement value of the TCP based on the angle-strain model. Compared to the laser sensor, the calculated displacement of the device shows a good tracking effect within the 95 % confidence interval. In the dexterous hand prototype, finger trajectory and joint angles are smoother under a PID controller compared to a non-PID controller, demonstrating the effectiveness of feedback control involving displacement and tension. Finally, the device can cover an extensive range of TCP strains and be applied in more TCP-driven bionic robots.