Retrieving a file binder from a bookshelf using pseudo-curved trajectory generation for a foldable robotic hand

Human-assistive robots need to perform trajectory making for and control of a robotic hand along the many rotating mechanisms in our living spaces. If such trajectory control can be performed without high-cost sensors, certainly a significant cost reduction in building the robot will be achieved. This paper describes a method of retrieving a file binder by generating a pseudo-curved trajectory for tilting it using a simple system. A simple claw mechanism with a switch sensor to grasp an object was designed and 3D-printed, and it was attached to a 6-DOF foldable robotic hand developed by the authors. A method for generating a pseudo-curved trajectory using the switch sensor was developed, and the robotic hand was successfully moved along this trajectory to tilt and grasp a file binder to retrieve it from a bookshelf. Experiments to clarify the success rate were also conducted, and it was found that the results depend on the rotational speed of manipulator links and the vibration of the claw mechanism link. A rubber sponge was added to give flexibility to the claw mechanism, which significantly improved the success rate. Furthermore, a control system to recover from tilting failure was constructed, and its effectiveness was validated by experiments.