Bidirectional inchworm motors and two-DOF robot leg operation

We have demonstrated a bidirectional inchworm motor that produces equivalent forces in both directions. This motor uses an additional set of gap-closing-actuator arrays to pre-bias the drive frame. To obtain the highest force densities possible, the motors are designed close to the limiting resolution of the process. We describe the inequalities relating the lateral etch depth to the actuator gap spacing and tooth width of the inchworm motors. In addition, we have demonstrated a two degree-of-freedom (DOF) robot leg operated with an external controller. The leg, 1 mm in length, was fabricated in a planarized SOI/2-poly process and was operated by two electrostatic inchworm motors. Each joint of the leg has demonstrated at least 90/spl deg/ of static angular deflection, and each inchworm motor has demonstrated a shuttle displacement of 400 /spl mu/m with speeds up to 6.8 mm/s. This corresponds to a robot foot speed of over 0.75 m/s and over 4 full steps per second. Endurance tests have shown that the shuttle and leg are visually undamaged after 60,000 full leg sweeps for 16.5 hours of operation (/spl sim/10 million inchworm cycles).