Parametric Contact Model (PCM) Development Plan MilestoneDateSoftware GoalExperimental Goal – Purchase DE (Dynamics Engine by Arachi) 10/1/03 (11/1/03) Revised Estimate – Identification of initial PCM for development 10/1/03 (10/17/03) Revised Estimate Have PCM Development Plan Characterized stage 1 PCM – PCM design review 10/31/03 (11/7/03) Revised Estimate Stage 1 implemented in DE Characterized stages 2-4 Have experimental goals and plan in place for gecko, roach, and robot feet – PCM prototype v0.1 to be exercised by users 12/2/03Stage 2 implemented in DETest facilities in place and operating – PCM v1.02/2/04Stage 3 implemented in DEFirst batch of experimental results on various feet. Begin matching to Stage 3 parameters.

Stage 1 - Simple Contact Model Description: Rigid foot when in contact, free when not Contact is event driven Release is time based Leg has linear and rotational spring/damper at the foot Questions Model Can Answer: Measure reaction forces to evaluate leg trajectories and foot compliance, How much does leg squeezing reduce reaction forces? Is 2.5kg excessive? How much do we gain/pay for changing mass? What leg trajectories minimize adhesion forces? How much adhesion will feet need to provide? And for how long? Model Complexity: Only 1 PCM parameter – T r the time of release Geometry of foot is a simple sphere with appropriate springs/dampers at the ankle Rx Ry

Stage 2 - Simple Contact with time/random effects Model Description: Rigid foot when in contact, free when not Contact is state driven with random element Release is time based or load based (including time-dependencies) Model Complexity: Additional PCM parameters: Slip force thresholds, time dependence, % chance of finding/losing a foothold, sliding friction Geometry of foot is a simple sphere with spring/dampers in leg Rx < Limit Ry < Limit Questions Model Can Answer: Evaluate gait strategies, foot-hold finding strategies, role of redundancy, Determine if gait is too fast (can’t find a foot-hold) or too slow (begin to slip), Evaluate how inhomogeneous surfaces affect getting a foot-hold Model could be extended to handle foot slip, with no motion until force limit is exceeded, then planer sliding with simple friction rule Friction

Stage 3 - Non-trivial Geometry Model Description: Foot with multiple toes (claws & sticky pads) Toes with different contact properties Compliance between toes Model Complexity: Additional PCM parameters: Pad friction model, claw adhesion model Geometry is a set of simple shapes with spring/dampers between Claw Pad Questions Model Can Answer: Foot Design strategies: How many toes? What arraignment? How much compliance between toes? How many claws/pads? We can begin to match experimental data for claws, setae, prototype feet

Stage 4 - Non-trivial Geometry on Surfaces Model Description: Foot with multiple toes (claws & sticky pads) Toes with different contact properties Compliance between toes Details of surface interaction including: Viscoelastic/plastic impact Time dependent friction Statistical surface properties Model Complexity: Additional PCM parameters: Time dependent adhesion or friction, Surface deformation properties, More complex pad and claw models, Velocity dependent impact and friction Geometry is a set of simple shapes with spring/dampers between Claw Pad Questions Model Can Answer: Foot & Behavior designs for finding holds on different surfaces Feed-forward vs. feed-back foothold finding algorithms. We can better match experimental data for claws, setae, prototype feet