S1-3.8 Jan. 5 Towards a realistic model of insect locomotion KUKILLAYA, R.P.*; HOLMES, P.J.; Princeton University, New Jersey; Princeton University, New Jersey firstname.lastname@example.org
We develop a hexapedal model to describe insect locomotion in the horizontal (ground) plane. The head-thorax-body is modeled as a single rigid body, and leg masses and inertias and joint dissipation are ignored. As in earlier work by Seipel, Holmes and Full (2004), we employ six actuated legs, but the legs, with `hip' and `knee' joints, better represent insect morphology. As an initial simple model, the muscles are represented as joint torsional springs. Actuation is provided via nominal angle inputs at each joint, corresponding to zero torques in the hip and knee springs. The inputs are determined from estimates of foot forces in the cockroach Blaberus discoidalis via an inverse problem. The resulting three degree-of-freedom dynamical system, subject to feedforward joint inputs, exhibits stable periodic gaits that compare well with observations over the insect's typical speed range. The model's response to impulsive perturbations also matches that of freely-running cockroaches (Jindrich and Full, 2002), and stability is maintained in the face of random foot touchdowns representative of running on rough terrain. Further, working towards our goal to develop a neuromechanical model, we introduce more realistic Hill-type muscles which actuate each joint in an agonist-antagonist pair. We study the stability properties of periodic gaits of this model driven by spike-train inputs, obtained from experimental data. Incorporation of a central pattern generator in such a model would provide an integrated description of locomotion, and ultimately permit the study of proprioceptive feedback pathways involving leg force and joint angle sensing.