A Method for Sensing Passive Joints of Robotic Extra Fingers for Trajectory Tracking

In the practical implementation of Robotic Sixth Fingers to restore grasping abilities in individuals with mobility impairments, accurately tracking the trajectory is crucial for ensuring proper object manipulation. Hence, there is a need for lightweight, durable, and cost-effective solutions to monitor the movement of finger segments. This study proposes sensor-equipped flexible joints capable of measuring the angle between the segments comprising the robotic finger. Initially, these joints were simulated to assess their mechanical behaviour and feasibility for accommodating strain gauges to measure the differential strain correlated with the angle measurement. Based on the simulation outcomes, two different types of sensor joints were developed, each with distinct mechanical properties. These joints underwent testing using a custom-built setup, and their performance was compared against accelerometers, which served as a reference for angle measurement. The test results demonstrated that the resolution of the sensor joints is enough for the envisaged application, while offering advantages in terms of weight and simplicity compared to alternative systems. Resulting RMSEs are lower than 13° for the first joint and less than 3° for the second one.