To properly position the PATS strongback all the 5 custom made actuators shall be controlled, synchronously, in such a way that the prescribed reference frame is always moving by following a predefined trajectory. The whole strongback assembly is inserted in cryostat where the temperature is held cryogenic during the working time. This makes problematic the motion control of the whole assembly with the standard actuation methods historically used for such devices (cams). A new solutions has been proposed where the strongback is suspended from top-mounted actuators. The link is made through invar connecting rods. The 5 degree of freedom that shall be controlled are:
The actuators are linked to the end effector (strongback) through rods, joints and links. The involved kinematics is then a complex nonlinear problem that must be solved either for the direct and the inverse problem.
The DIRECT kinematics links the actual actuators position with the 5 DOF previously defined. At each point in time, the actuator positions defines a specific orientation and and position of the strongback in the space. Due to absence of absolute feedback systems on the strongback, the only available mechanism to know its position and orientation is through the direct kinematics. All the actuators provides an absolute position feedback.
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Initially the idea was not to use any additional external feedback to properly locate the position of the quadrupole's center. During the PHASE 1 testing, came out the need of using an accurate external measurement system to properly track the position and orientation of the quadrupole's reference frame.
