Robust physics-based locomotion using low-dimensional planning

Abstract

Figure 1: Interactive locomotion control over varied terrain. Gait, footsteps, and transitions are automatically generated, based on userspecified goals, such as direction, step length, and step duration. In the above example, a user steers the biped across uneven terrain with gaps, steps, and inclines. AbstractThis paper presents a physics-based locomotion controller based on online planning. At each time-step, a planner optimizes locomotion over multiple phases of gait. Stance dynamics are modeled using a simplified Spring-Load Inverted (SLIP) model, while flight dynamics are modeled using projectile motion equations. Full-body control at each instant is optimized to match the instantaneous plan values, while also maintaining balance. Different types of gaits, including walking, running, and jumping, emerge automatically, as do transitions between different gaits. The controllers can traverse challenging terrain and withstand large external disturbances, while following high-level user commands at interactive rates.

Optimizing locomotion controllers using biologically-based actuators and objectives

“…A natural extension is to investigate whether our control parameterization and effort term can be combined with the popular task-space controllers [Coros et al 2010; de Lasa et al 2010; Wu and Popović 2010] and higher-level planning [Coros et al 2009; Mordatch et al 2010] to create humanlike motions on uneven terrains [Wu and Popović 2010] or obstacle courses [Mordatch et al 2010; Ye and Liu 2010]—scenarios that have only been addressed using purely joint-actuated characters.…”

“…Figure 6a shows the hip, knee, and ankle angles of walking data generated by our 1.0 m/s controller ( swalk ) compared to controllers of similar speeds presented by previous contributions [Coros et al 2009; Mordatch et al 2010; Wang et al 2010], as well as human data at 1.0 m/s. A major artifact from all of the previous works is the lack of hip extension during mid-gait, which does not occur in our result.…”

“…A major artifact from all of the previous works is the lack of hip extension during mid-gait, which does not occur in our result. The feature-based controller of Mordatch et al [2010] is robust and flexible, but their basic walking gait shows an obvious crouch. Our result also exhibits a range of knee motion more similar to humans compared to previous works.…”

“…Likely due to our modeling of human-like torque generation and activation delays, our controllers cannot tolerate nearly as much external force as recently developed controllers for purely joint-actuated characters [Mordatch et al 2010; Wang et al 2010]. However, we can still follow Wang et al [2010] and optimize explicitly for controllers that can deal with external forces.…”

“…One important recent contribution is SIMBICON [Yin et al 2007], a remarkably robust 3D humanoid locomotion controller based on the balance control of Raibert and Hodgins [1991]. A number of projects have since focused on expanding the controller repertoire for simulated bipeds [Jain et al 2009; Coros et al 2010; de Lasa et al 2010] and on locomotion in complex environments [Mordatch et al 2010; Wu and Popović 2010]. …”