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

Part

Support

Deposit (part)

Shape

MURI

Fabrication

Shape Deposition Manufacturing

• Embed Components in mid-process• Critical Geometry, Properties

Deposit (part)

Shape

EmbedDeposit (support)

Shape

Embedded Component

Part

Support

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