Hybrid kinematic model applied to the under-actuated robotic hand prosthesis ProMain-I and experimental evaluation

Upon the appearance of nylons, silicon, tendons, smart and soft materials, wearable robotics is going closer to the human body, leading robotics and biomechanics to provide us new physical rehabilitations and improvements. In the area that concerns soft robotic prosthesis, the main challenge is the design of well sized mechatronic limbs and smart controllers that should help people to achieve desired movements. As a consequence, we present a hybrid model that allows different ways of representing hand poses, according to special interactions that arise from soft robotics chains. Our hybrid model uses the positions of finger's parts computed with the Denavit-Hartenberg (DH) method mixed with the quaternions representation to avoid singularities and to reduce the number of DH parameters. Kinematic and dynamic of finger motions are evaluated using an experimental setup with mechanical parts produced by 3D printing and different actuators. Finally, experimental results are compared with the theoretical values and demonstrate the accuracy of our model.