Development of motion models for writting of the Spanish alphabet on the humanoid bioloid robotic platform

Service Robotics (SR) is one of the main areas of research for the development of assistive and supportive technologies for humans. Nowadays there are many robotic platforms used for this purpose. Among them, the Bioloid is one of the most widely used platforms due to the flexibility of its structure (e.g., different types of robots can be built). Particularly, the Bioloid configured with humanoid structure is suitable for assistive tasks. Robot-assisted writting is among the most challenging tasks to implement given its complexity and required fine control. In this paper, the development of a set of motion models for the humanoid Bioloid for each character in the Spanish alphabet is presented. For the motion models, initially the ability of the Bioloid´s servomechanisms to achieve smooth and straight trajectories was evaluated under different conditions of speed rate, joint softness, and inertial force. Then, three approaches were considered to define the straight trajectories used to draw each alphabet character: continuous, segment-based, and point-based. In practice it was found that medium speed rate and inertial force with high softness led to straight trajectories. Also, the point-based approach performed better (generated highly defined alphabet characters) than the segment-based approach, and both performed better than the continuous approach. The resulting models can be used to evaluate the performance of trajectory planning techniques or continuous transcription of acoustic information.