Meeting Abstract

43.5  Saturday, Jan. 5  A Clock-Controlled Hip-Torqued Model for Locomotion SEIPEL, Justin*; FULL, Robert J; Univ. of California, Berkeley jseipel@berkeley.edu

Simple spring-mass models have been used to describe net center of mass forces and motions of a diverse array of animals and robots. For ranges of behavior realistic to animals and robots, classic uncontrolled and underactuated Spring-Loaded Inverted Pendulum (SLIP) models have small domains of stability or are entirely unstable. We developed a simple dynamical model for legged locomotion inspired from insects that extends the SLIP model to capture the robustly stable dynamics of many running animals and robots. The model is composed of a clock-controlled hip torque with proportional derivative, proprioceptive feedback at the hip and a passive, axial leg spring. We found that this clock-torqued extension of SLIP (CT-SLIP) was robust to perturbations due to damping within the leg and clock-controlled forcing at the hip which can introduce a corrective force perpendicular to the axial leg-spring. Stability was increased further by adding slipping between ground and foot. Robustness was preserved when we simplified the torque to be constant during stance, suggesting that proprioception may be only necessary during swing to reset legs to a desired phase. CT-SLIP reproduced the dynamic accelerations performed by a hexapedal robot (RHex). Further, CT-SLIP explained the dynamics of fast running cockroaches perturbed by a sudden decrease in ground stiffness by active adjustments without exteroceptive sensing. The model suggests that passive-dynamic mechanical systems entrained to feedforward clock signals with simple control of hip torque can provide the basis for the highly robust stability seen in many animals.