Movement Error Based Control for a Firm Touch of a Soft Somatosensitive Actuator

We propose a control architecture with the aim of providing a firm touch of a soft somatosensitive actuator (SSA) finger with an object. The two main components of the architecture are a reference tracking curvature controller and a force controller. The first one sets the finger in motion which is blocked if the finger comes into contact with an object. The result of such an event is that the finger bending is constrained, and the tracking error of the curvature controller increases. Once the error exceeds a predetermined threshold value, there is a switch from the reference tracking to the force controller, which maintains the finger in contact with the object. Therefore, the proposed architecture accounts not only for sensory data, but also for the error of the movement towards the touch. The proposed control architecture is illustrated with numerical simulations.