High-LevelControlMURI
Low-LevelControl
Fabrication
How do we build robust biomimetic structures and systems?Shape deposition manufacturing of integrated parts, with embedded actuators and sensors (Stanford)
How do we build-in tailored compliance and damping?
Effects of Compliance in simple running machine (Stanford, Berkeley ME)
Structures with functionally graded material properties (Stanford)
Guiding questionsGuiding questions
MURI
Fabrication
Biomimetic Structures• Increase Robustness• Integrated Sensing and Actuation• Tailored Structural Properties
Body frame Lift pot
Knee pot
Hip pot
Abduct pressuresensor
Lift pressuresensor Extend pressure
sensor
Gears
Actuators
Boadicea Leg Design(MIT 1995)
Contoured Multi-material Prototype
MURI
Fabrication
Shape Deposition Manufacturing• Cycle of Material Deposition and Removal• Complex 3D Geometry, Multi-materials
PartSupport
Deposit (part)
Shape
MURI
Fabrication
Shape Deposition Manufacturing• Embed Components in mid-process• Critical Geometry, Properties
Deposit (part)
Shape
EmbedDeposit (support)
Shape
Embedded Component
PartSupport
MURI
Fabrication
Design-by-Composition Interface
Part Compacts Support CompactsPrimitives
Primitive A Primitive B
Result Primitive
Library Components Merged by Designer
MURI
Fabrication
Design-by-Composition Interface
Part Compacts Support CompactsPrimitives
Primitive A Primitive B
Result Primitive
CompactList A
CompactList B
Result Compact List
Manufacturing Plans MergedBy Algorithm
a3
a2
a1
b3
b2
b1
Library Components Merged by Designer
MURI
Fabrication
Embedded Components
• Pneumatically-actuated Linkage• Piston, Valve, Pressure Sensor, Fittings
Steel leaf-spring
Piston
Sensor and circuit
Spacer
Valves
Tubing Connector
Design Interface Process Planning
MURI
Fabrication
Embedded Components
• Issues in Embedded Components (Cham et. al.)– Fixturing, Retaining Functionality, Tolerances
Steel leaf-spring
Piston
Sensor and circuit
Valves
MURI
Fabrication
Electrical Connectors
AirConnector
Embedded Components• Reduction of Transport Volumes - Higher Bandwidth• SDM moved us to new Control Regime
4 inches
MURI
Fabrication
Biomimetic Structures
• Multi-Materials Parts with different properties• Arbitrary Geometry, Graded Materials• Biological Inspiration
Contoured-Shaped Multi-Material Prototype
MURI
Fabrication
Graded Materials• Graded Materials Very
Common Nature• Few Examples of
Functionally Graded Materials in Man-Made Assemblies
MURI
Fabrication
Graded Materials• SDM Allows Variability in
Compliance and Damping throughout a Candidate Design
MURI
Fabrication
Process Plan
Graded Materials• SDM Allows Control of Material
Location and Property in a 3D space
Fabrication Cycle
MURI
Fabrication
Graded Materials• Un-Actuated Five-Bar Leg Mechanism Illustrates Benefits
of Heterogeneous Material Properties• Flexure Joints Replace Pin-Joints to Add Compliance and
Damping
MURI
Fabrication
Graded Materials• Desired Performance of Structural and Flexural Regions
Very Different• Fabricating With Single Material Would Result In
Compliant Structural Regions or Brittle, Failure Prone Flexures
• Ideal Solution Requires Varying Material Properties Between Different Regions of the Part
MURI
Fabrication
Graded Materials• Graded Interface Increases Surface Area, Resulting in
Increased Bonding• Mixing in Arbitrary Ratios Not Possible• Function Needs to Be Applied To Discretize the Graded
Regions Based Upon a Specified Tolerance Parameter
MURI
Fabrication
Compliance for 1 DOF Machine• Berkeley 1 DOF Walking Machine• Four-Bar Linkages Represent Practical Application
Well Suited to Use of Graded Materials
MURI
Fabrication
Compliance for 1 DOF Machine• Reduce Assembly Complexity, Increase Robustness• Four-Bar Mechanism Utilizes Two Rotary Joints and Two Rocker Joints
Original Design(Berkeley)
SDM Re-Design
MURI
Fabrication
Compliance for 1 DOF Machine
Original Design SDM Re-Design
•Rocker Pin Joints Replaced With Flexural Regions to Introduce Compliance and Damping
MURI
Fabrication
Compliance for 1 DOF Machine
• New Design Features With SDM
• Geometry: Constant Ground Contact
• Replaced Pin Joints With Flexural Region: Introduced Compliance & Damping
• Leg Preflexes Defines by Build Orientation
• Future Analysis and Experiments to Tune Compliance to Locomotion
Wrap up
• Status• Programmatic issues• Plans• Feedback
Status -- one year ago: 9.10.98
• “Building block” design/fabrication environment being tested and first components with embedded sensors, electronics fabricated
• Meetings among SU, SRI, UCB to determine biomimetic actuators for fabrication and testing at each site
• Designed and built apparatus for leg stiffness and perturbation experiments
• Test-bed for compliance manipulation control set up.• Experimental results on human adaptive control suggest a specific
design for manipulation• Modeling and system I.D. applied to capture human walking on hills.
The results have been used to develop two-legged machines. Comparison with biological models is underway.
Status (today: 9.2.99)• Detailed characterization of passive (fixed) and active components
(adjustable) of preflexes in cockroach.• Gecko foot adhesion characterized using new micromachined sensors.
Sensors for insect leg forces being designed.• SDM* environment used to create small robot limbs with embedded
sensing and actuation and functionally graded material properties.• SDM robot limbs and compliant non-SDM robot undergoing testing
and comparison with results from insect legs.• Compliant whole-arm-manipulator test-bed and minimum impedance
control strategies demonstrated. Human impedance testing in progress.• Model of human motor control learning tested and validated.• Fast walker with biomimetic foot trajectory designed and tested; SDM
compliant limb retrofit underway.
*Shape Deposition Manufacturing
Plans (see project structure chart)
Low-LevelControl
High-LevelControl
MURI
BiomimeticRobots
2nd generation SDM robots with sensing and preflexes
