Anticipatory control using substrate manipulation enables trajectory control of legged locomotion on heterogeneous granular media

Abstract

Legged robots must traverse complex terrain consisting of particles of varying size, shape and texture. While much is known about how robots can effectively locomote on hard ground and increasingly on homogeneous granular media, principles of locomotion over heterogeneous granular substrates are relatively unexplored. To systematically discover how substrate heterogeneity affects ambulatory locomotion, we investigate how the presence of a single boulder (3D printed convex objects of different geometries) embedded in fine granular media affects the trajectory of a small (150 g) six legged robot. Using an automated system to collect thousands of locomotion trials, we observed that trajectories were straight before the interaction with the boulder, and scattered to different angles after the interaction depending on the leg-boulder contact positions. However, this dependence of scattering angle upon contact zone was relatively insensitive to boulder shape, orientation and roughness. 1 Inspired by this insensitivity, here we develop an anticipatory control scheme which uses the scattering information in coordination with a tail induced substrate jamming. Our scheme allows the robot to "envision" outcomes of the interaction such that the robot can prevent trajectory deviation before the scattering occurs. We hypothesize that (particularly during rapid running or in the presence of noisy sensors) appropriate substrate manipulation can allow a robot to remain in a favorable locomotor configuration and avoid catastrophic interactions.

An obstacle disturbance selection framework: emergent robot steady states under repeated collisions

“…Gibson (1979) proposed the notion of environmental affordance as an agent’s acting to exploit an environmental structure in a manner favorable to some desired outcome. In the past few decades, there have been a number of biomechanics (Gart et al, 2019; Li et al, 2015; McInroe et al, 2016; Sane and Dickinson, 2001; Schiebel et al, 2019; Winter et al, 2012) and robotics (Arslan and Saranli, 2012; Bayraktaroglu and Blazevic, 2005; Byl and Tedrake, 2009; Curet et al, 2010; Kim et al, 2008; Qian and Goldman, 2015a; Qian et al, 2013; Rieser et al, 2019; Transeth et al, 2008; Winter et al, 2014) studies that began to reveal a wide variety of environmental affordances (Gibson, 1979) for locomotion, and how different locomotor morphology and kinematics allows exploitation of such affordances to effectively move through complex environments.…”

Mechanical Performances of Typical Robot Feet Intruding into Sands

“…This compression results in the jamming of constitutive particles, so the granular media also behave like solids [6,7]. Granular media are highly heterogeneous [8] due to the variations in size, shape, compactness, friction coefficient of particles and inner moisture [5]. All these characteristics impact the physical properties of granular media, such as loading ability, angle of stability and bulk density [9], some of which are quantifiable indoors or in the field.…”

The dynamics of legged locomotion in heterogeneous terrain: universality in scattering and sensitivity to initial conditions

“…of different locomotion modes. In this manner robots could choose locomotion maneuvers to traverse challenging terrain, or perform successful anticipatory control [10] before the disturbance to avoid fatal failure and course deviation.…”