Parametric Contact Model (PCM) Development Plan

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Parametric Contact Model (PCM) Development Plan
Milestone Date Software Goal Experimental Goal
4.1.2.1 Purchase DE (Dynamics Engine by Arachi) 10/1/03 (11/1/03) Revised Estimate
4.1.2.3 Identification of initial PCM for development 10/1/03 (10/17/03) Revised Estimate Have PCM Development Plan Characterized stage 1 PCM
4.1.2.5 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.
4.1.2.7 PCM prototype v0.1 to be exercised by users 12/2/03 Stage 2 implemented in DE Test facilities in place and operating.
4.1.2.10 PCM v1.0 2/2/04 Stage 3 implemented in DE First batch of experimental results on various feet. Begin matching to Stage 3 parameters.
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Stage 1 - Simple Contact
Ry
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
Rx
Model Complexity Only 1 PCM parameter Tr the
time of release Geometry of foot is a simple
sphere with appropriate springs/dampers at the
ankle
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?
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Stage 2 - Simple Contact with time/random effects
Ry lt Limit
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)
Rx lt Limit
Model could be extended to handle foot slip, with
no motion until force limit is exceeded, then
planer sliding with simple friction rule
Friction
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
Questions Model Can Answer Evaluate gait
strategies, foot-hold finding strategies, role of
redundancy, Determine if gait is too fast
(cant find a foot-hold) or too slow (begin to
slip), Evaluate how inhomogeneous surfaces
affect getting a foot-hold
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Stage 3 - Non-trivial Geometry
Model Description Foot with multiple toes
(claws sticky pads) Toes with different
contact properties Compliance between toes
Claw
Pad
Model Complexity Additional PCM parameters Pad
friction model, claw adhesion model Geometry is
a set of simple shapes with spring/dampers
between
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
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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
Claw
Pad
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
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