Delta Thales, a novel architecture for an orientating device with fixed RCM (remote center of movement) and linear movement in direction of the RCM

A new 3 degrees of freedom (dof) structure is presented. It features rotation on two axes with a fixed remote center of motion (RCM) i.e. it always aims at the same point. The third axis is a linear movement in direction of the fixed point. This type of kinematics is useful for many applications where a parasitic translational movement during the rotation is undesirable. The kinematics is based on the well known Delta robot. It is in fact composed of two Deltas mounted on the same command arms, which are linked to the rotary actuators. Therefore the two Delta robots move in the same manner except that the one fixed at the end of the bars moves of a bigger amount than one fixed closer to the actuators. The two nacelles are then connected through a sliding universal joint and a ball-and-socket joint to the output. This connection represents the output of the robot. To guarantee a perfect RCM there needs to be a certain ratio between some geometric parameters of the machine. This ratio is based on the Thales theorem and will be explained in details in this article. The paper will also present the detailed kinematics and its optimization, some construction details of the prototype and geometric model. At the end we will propose some applications as well as the needed modifications to guarantee application specific performance.