Meeting Abstract
Rapid and agile animal locomotion has inspired generations of rapid running legged robots. We present, the Harvard Ambulatory MicroRobot (HAMR) – an insect scale (45 mm long, 1.43 g) quadrapedal robot capable of high speed locomotion up to 50 cms-1 (>10 BLs-1) on level ground, making it one of the smallest yet fastest terrestrial robots. HAMR has 8 actuators in total, 2 for each leg to independently control vertical and fore-aft motions. By commanding the phase between actuators, the robot can execute desired leg trajectories resulting in six gaits over a range of frequencies (0-60 Hz) without need for stride control. Few biological counterparts (mites and tiger beetles) exhibit such a broad range of stride frequencies. While higher actuation frequencies allow HAMR to run faster, they also excite the leg transmission resonances making foot trajectories highly susceptible to parasitic phase shifts from desired gaits, and therefore, not suitable for locomotion. Unpredictable ground contacts make rapid running further challenging. These observations led us to design new sensing mechanisms to estimate leg actuator positions and detect ground contact. Preliminary experiments with a single leg robot prototype predict atleast 3-fold increase in stride length while operating at higher stride frequencies suggesting a significant improvement in running performance. Such a locomotion strategy draws parallels with the American cockroach Periplaneta americana, which initially increases stride frequency to increase speed and subsequently stride lengths via gait change (hexapedal to quadrapedal to bipedal). With easily adjustable morphological features like tail or posture or additional legs, we believe that HAMR is a unique and powerful platform for testing locomotion hypotheses in biological systems at scale.
