toward controlled passive actuationrobotics.estec.esa.int/.../astra2013/presentations/... ·...

Toward Controlled Passive Actuation

Douwe Dresscher

ASTRA 2013

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What can you expect (I)

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20 minutes presentation (a lot of me)

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5 minutes of Q&A and discussion afterwards (a lot of you)

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---------------------------------------- +

2




---------------------------------------- +25 minutes total

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What can you expect (II)

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• Context

3


• Context

• Problem

3


• Context

• Problem

• Solution

3


• Context

• Problem

• Solution

• Wrap-up

3


• Context

• Problem

• Solution

• Wrap-up

• Questions

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Context: the short version

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5

RObotic SEnsors project

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RObotic SEnsors projectLocomotion

Rocks/stones

Loose sand

Steep slopes

Roads

Energy consumption (potential)

Environmental footprint

ESA - AOES Medialab Mattracks FZI Research Centerfor Information TechnologyImage courtesy of:

The problem(s)(Challanges if you wish)

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High number of actuators compared to tracked and

wheeled vehiclesActuators are heavy

Mass has to be supported by the legs

Low payload-to-weight ratio

Low energy-efficiency

Energy lost at impact scales with mass

Relatively high system mass

Impact at every step

System suffers increased mechanical

stress

AND AND

AND

Based on literature8










stress

AND AND

AND

Based on literature

“It seems unrealistic to acount the low energy efficiency to impact only”

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Motion profile

0 1 2 3 4 5 6time {s}

-0.05

0

0.05

0.1Position setpoint {m}Velocity setpoint {m/s}

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Energy

0 1 2 3 4 5 6time {s}

-10

0

10

20

30

40

Supplied Energy {J}Dissipated Energy {J}Stored Energy {J}

10

Energy

0 1 2 3 4 5 6time {s}

-10

0

10

20

30

40

Dissipated Energy {J} - Motor electrical resistance Dissipated Energy {J} - SoilDissipated Energy {J} - GearboxDissipated Energy {J} - Total

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Energy

0 1 2 3 4 5 6time {s}

-10

0

10

20

30

40

Dissipated Energy {J} - Motor electrical resistance Dissipated Energy {J} - SoilDissipated Energy {J} - GearboxDissipated Energy {J} - Total

76%

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stress

AND AND

AND

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stress

AND AND

AND

Additional movement in the legs compared

to wheeled and tracked vehicles

Servo-motors are very energy-inefficient in start

stop behavior and providing constant torque

Significant losses in actuatorsAND AND

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The proposed solution(How we are approaching it)

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Ploss = (1-efficiency) * Pin

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We cant do anything about that

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But we can try to do something about that

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But we can try to do something about that

Minimize the energy flow trough the actuators

14











Significant losses in actuators




stress

AND AND

AND

AND AND

15















stress

AND AND

AND

AND AND

Reduce the number and/of size of actuatorsAbsorb the impact energyPassive gravity

compensation

Minimize the energy flow trough actuators

15















stress

AND AND

AND

AND AND

Reduce the number and/of size of actuatorsAbsorb the impact energyPassive gravity

compensation

Minimize the energy flow trough actuators

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✓ ✓

✓ ✓

✓

What will we use to achieve this

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Controlled passive actuation

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Controlled passive actuation Position

-1 0 1 2 3 4 5 6

-1

0

1

2

3

Actual position {m}Position setpoint {m}

y

x

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19


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1.Actuation forces are delivered by the spring

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➡Actuators only used for reconfiguration

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➡Actuators can be (much) smaller

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➡Minimal energy flow trough actuators

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2.Intrinsic gravity compensation

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2.Intrinsic gravity compensation

3.Enables absorbtion and re-use of impact energy

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Impact absorption

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Energy

0 0.1 0.2 0.3 0.4 0.5 0.6time {s}

0

5

10

15

Kinetic energy {J}Mass potential energy {J}Spring potential energy {J}

Forces

0 0.1 0.2 0.3 0.4 0.5 0.6time {s}

-400

-300

-200

-100

0

100

Internal force {N}

Energy

0 0.1 0.2 0.3 0.4 0.5 0.6time {s}

0

5

10

15

Kinetic energy {J}Mass potential energy {J}

Forces

0 0.1 0.2 0.3 0.4 0.5 0.6

time {s}

-40000

-30000

-20000

-10000

0

Internal Force {N}

Without impact absorption With impact absorption

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Wrap-up

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Thank you!

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toward controlled passive actuationrobotics.estec.esa.int/.../astra2013/presentations/... ·...

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