Principle of operation

The principle of the PAD technology rests upon the conversion of the periodic elongation of powerful multilayer actuators into precise rotation of a motor shaft. To improve the performance of the PAD even further, a newly developed micromechanical interlock between the motor ring and the motor shaft was applied, increasing torque and precision while avoiding backlash and slippage.

The approach, as shown in the figure below, is an arrangement of two orthogonally orientated piezo multilayer stacks attached to a motor ring covering a motor shaft, the diameter of the shaft being slightly smaller than the internal diameter of the ring.

Thanks to the innovative design, the PAD drive uses very few components compared to servo-‐controlled drive systems, allowing a more straightforward, compact and reliable design.

The same principle can be applied with smaller actuators such as plate benders or stacks of larger cross-section. By doing so, the power output of a PAD system can be scaled.

Furthermore, the internal gearing can be modified. This allows different speed/torque characteristics with sensibly the same power capability.