Zesch Wolfgang, Roland Büchi, Alain Codourey, Roland Siegwart
Presented at the SPIE Conf. on Microrobots and Micromechanical Systems, p80-88, October 1995, Philadelphia, PA, USA.
inertial drive, impact drive, micropositioning, piezo-electric, positioning table, micromotor
In micro or nanorobotics, high precision movement in two or more degrees of freedom is one of the main problems. Firstly, the positional precision has to be increased (< 10 nm) as the object sizes decrease. On the other hand, the workspace has to have macroscopic dimensions (1 cm3) to give high manoeuvrability to the system and to allow suitable handling at the micro/macro-world interface. As basic driving mechanisms for the ETHZ NanoRobot Project, two new piezoelectric devices have been developed. "Abalone" is a 3-dof system that relies on the impact drive principle. The 38 mm x 33 mm x 9 mm slider can be moved to each position and orientation in a horizontal plane within a theoretically infinite workspace. In the stepping mode it achieves a speed of 1 mm/s in translation and 7 deg/s in rotation. Within the actuator's local range of 6 m fine positioning is possible with a resolution better than 10 nm. "NanoCrab" is a bearingless rotational micromotor relying on the stick-slip effect. This 10 mm x 7 mm x 7 mm motor has the advantage of a relatively high torque at low rotational speed and an excellent runout. While the maximum velocity is 60 rpm, it reaches its highest torque of 0.3 mNm at 2 rpm. Another benefit is the powerless holding torque of 0.9 mNm. With a typical step of 0.1 mrad and a local resolution 3 orders of magnitude better than the step angle, NanoCrab can be very precisely adjusted. Design and measurements of the characteristics of these two mechanisms will be presented and compared with the theoretical analysis of inertial drives presented in a companion paper. Finally their integration into the Nanorobot system will be discussed.
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