Transition by head-on collision: mechanically mediated manoeuvres in cockroaches and small robots

Abstract

Exceptional performance is often considered to be elegant and free of ‘errors’ or missteps. During the most extreme escape behaviours, neural control can approach or exceed its operating limits in response time and bandwidth. Here we show that small, rapid running cockroaches with robust exoskeletons select head-on collisions with obstacles to maintain the fastest escape speeds possible to transition up a vertical wall. Instead of avoidance, animals use their passive body shape and compliance to negotiate challenging environments. Cockroaches running at over 1 m or 50 body lengths per second transition from the floor to a vertical wall within 75 ms by using their head like an automobile bumper, mechanically mediating the manoeuvre. Inspired by the animal's behaviour, we demonstrate a passive, high-speed, mechanically mediated vertical transitions with a small, palm-sized legged robot. By creating a collision model for animal and human materials, we suggest a size dependence favouring mechanical mediation below 1 kg that we term the ‘Haldane limit’. Relying on the mechanical control offered by soft exoskeletons represents a paradigm shift for understanding the control of small animals and the next generation of running, climbing and flying robots where the use of the body can off-load the demand for rapid sensing and actuation.

Vision does not impact walking performance in Argentine ants

“…Our observations that Argentine ants decelerate to slower speeds, but do not stop as 237 the mandible nears the step edge ( Fig. 5A) differs from maximally sprinting cockroaches that 238 collide with a tall vertical obstacle before climbing (Jayaram et al, 2018). Argentine ant workers 239 appear to decelerate of their own control rather than through interactions with an obstacle.…”

“…Cockroaches with occluded ocelli prefer to 259 tunnel under versus climb over an obstacle (Harley et al, 2009), while cockroaches with 260 occluded compound eyes collide more frequently with obstacles than when their vision is 261 unimpeded (Baba et al, 2010). To our knowledge, only two studies show no influence of vision: 262 cockroaches sprinting (approximately 25 body length/second) then transitioning to vertical 263 climbing (Jayaram et al, 2018) and a diurnal species of tiger beetle effectively "blinded" by 264 motion blur due to fast running speeds (up to 120 body lengths/second) (Zurek and Gilbert, 265 2014). Unlike these two examples, Argentine ant workers walk at moderate speeds 266 (approximately 10 body lengths/second) yet also maintain similar walking behavior between 267 light and dark conditions.…”

“…These data suggest that vision likely does not influence intra-stride walking 61 coordination but may inform obstacle avoidance at intermediate distances. However, few 62 studies have directly tested the impact of vision on step-to-step walking performance with 63 "effective blindness" presented as a novelty (Gilbert, 1997;Jayaram et al, 2018), whereas it 64 may be considerably widespread. 65…”

How Can Interfacial Phenomena in Nature Inspire Smaller Robots

“…Reproduced with permission. [ 164 ] Copyright 2018, Royal Society. c) Wave‐like trajectory of a running cockroach (left) and its prototype robot (right).…”

“…This mechanically mediated high‐speed transition strategy, rather than fine sensor‐based control, inspired a robot that is a few cm long and uses viscoelastic responses from structural pounding (Figure 6b). [ 164 ]…”