h. kazerooni human engineering laboratory (hel) university of california at berkeley

MURI

Fabrication

Biomimetic Robots - ONR Site Visit - August 9, 2000

H. Kazerooni

Human Engineering Laboratory (HEL)

University of California at Berkeley

ONR Site VisitAugust 9, 2000

MURI

Fabrication


Topics

1. Ground Reaction Force Control2. Frequency Matching Control

EXAMPLE

a

b c

d

f

g

Path Generation

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Power Terrain

• One motor powers all legs

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Flexible Feet Construction

• Shape Deposition Modeling (SDM)

• Simple Spring Legs Control system is embedded in hardware (Elasticity, Damping, and Mass of Legs)

2

34

1

2

3

4

1 2

3

4

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Frequency Matching

• Inverse Pendulum Model• Frequency of Walking (pendulum) α

Natural Frequency of Leg (spring)• In fact, for cockroach,

Freq. of Walking ≈ fn of 3 legs / 3 ≈ 14Hz

Trajectory of center of mass

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Mechanical Walker

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Ground Reaction Force Control

The only external force on a walking machine is imparted by the ground.

Large Ground Reaction Forces lead to large acceleration and large speed

Considering Newtonian Mechanics, zero Ground Reaction Forces lead to zero motion (f = m α)

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Infinitely Rigid GroundGround Reaction forces = f (T1, T2)

A leg during stance phase

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Zero Stiffness GroundGround Reaction forces = 0

A leg during swing phase

A leg during swing phase does not contribute to motion of the machine.

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Actual GroundGround Reaction Forces = f ( T1, T2 and K)

A leg during stance phase

The fundamental method of creating locomotion for the

walking machine is the generation of appropriate

ground reaction forces on the machine leg that is in contact with the ground, not the leg

which is swinging; in fact, the leg during the swing phase

should not be powered to save

energy.

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Fabrication


The Ground Reaction Forces are the “Actuators” of a Walking Machine

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W

ηW

The Horizontal Ground Reaction Forces are controlled to be larger than ηW

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Electronic Schematic

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ηW C

os () +

W Sin (

)

The Ground Reaction Forces must be controlled

to be larger than ηW Cos () +W Sin ()

Inclined Maneuvers

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h. kazerooni human engineering laboratory (hel) university of california at berkeley

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