Modeling of Sawyer planar sensor and motor dependence on planar yaw angle rotation

Planar motion systems based on commercial Sawyer motors provide uniform performance over their entire workspace, offering fairly high speeds (1.5 m/sec), accelerations (30 m/sec/sup 2/), and precision (sub-micron resolution). Using multiple motors over a common plateau provides an excellent basis for an agile table top, very high resolution, manufacturing system. Sawyer motors have 3 planar degrees-of-freedom X-Y-Yaw (rotation in the plane). The motor is very sensitive to yaw rotation, its force decreases rapidly, and it can lose synchronisation. This paper develops an analytical model of the motor, provides guidelines for the design and a real-time compensation method for errors resulting from yaw rotation. The model applies to magnetic, capacitive and optical position sensing using the platen as a reference grid.