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# H. Kazerooni Human Engineering Laboratory (HEL) University of California at Berkeley - PowerPoint PPT Presentation

ONR Site Visit August 9, 2000. H. Kazerooni Human Engineering Laboratory (HEL) University of California at Berkeley. Topics 1. Ground Reaction Force Control 2. Frequency Matching Control. EXAMPLE. f. g. b. c. a. d. Path Generation. Power Terrain. One motor powers all legs. 2. 4.

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ONR Site VisitAugust 9, 2000

H. Kazerooni

Human Engineering Laboratory (HEL)

University of California at Berkeley

Topics1. Ground Reaction Force Control2. Frequency Matching Control

f

g

b

c

a

d

• One motor powers all legs

4

3

2

1

1

2

4

3

4

3

Flexible Feet Construction

• Shape Deposition Modeling (SDM)

• Simple Spring Legs

Control system is embedded in hardware

(Elasticity, Damping, and Mass of Legs)

Frequency Matching

• Inverse Pendulum Model

• Frequency of Walking (pendulum) α

Natural Frequency of Leg (spring)

• In fact, for cockroach,

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

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

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

Large Ground Reaction Forces lead to large acceleration and large speed

Infinitely Rigid Ground

Ground Reaction forces = f (T1, T2)

A leg during swing phase does

not contribute to motion of the

machine.

Zero Stiffness Ground

Ground Reaction forces = 0

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.

Actual Ground

Ground Reaction Forces = f ( T1, T2 and K)

W Walking Machine

ηW

The Horizontal Ground Reaction

Forces are controlled to be larger than ηW

Electronic Schematic Walking Machine

Inclined Maneuvers Walking Machine

ηW Cos () +W Sin ()

The Ground Reaction Forces must be controlled

to be larger than ηW Cos () +W Sin ()