The development of an electro-optical goniometric sensor for tracking articulated hand motion

The study of hand kinematics has developed into an important research area. Several techniques have been proposed for recording hand movements, however the majority suffer from poor accuracy and limited functionality. To overcome these limitations, this research aims to develop a novel goniometric sensor for tracking articulated hand motion. This research is the first attempt to use Malus’ law as a sensing principle for monitoring human hand kinematics. Three distinct electro-optical sensors (sensor#1, sensor#2, and sensor#3) with compact configurations are developed. They are coupled with the rotation of the finger joints and detect angular motion by analysing the attenuation of light transmitted through linear polarising films. The three goniometric sensors are designed with different measurement capabilities to suit different types of finger articulation. Sensor#1 has a single rotation axis and a measuring range of 0◦ to 90◦, which can be used for the distal interphalangeal joints. Sensor#2 can measure the movements spanning 180◦ with an improved sensitivity in a single plane; this is ideal for the proximal interphalangeal joints. Sensor#3 consists of two measurement axes, each having a measurement range up to 180◦. These properties make sensor#3 suitable for monitoring the finger joints with two degrees of freedom (DOFs), e.g. the metacarpophalangeal joints; this is unique in designing a single sensor for monitoring the two-DOF finger joints. In comparison with a commonly used commercial bend sensor, the electro-optical sensors demonstrate higher measurement accuracy (mean absolute error: ≤0.28◦) and faster response time under laboratory conditions. Furthermore, the developed sensors all successfully tracked the dynamic finger motion when attached to human finger joints. This work verifies that the developed electro-optical sensors offer a viable sensing technique for tracking articulated human motion directly with high measurement accuracy