Simulating Balance Recovery Responses to Trips Based on Biomechanical Principles Takaaki Shiratori 1,2 Rakié Cham 3 Brooke Coley 3 Jessica K. Hodgins 1,2

Simulating Balance Recovery Responses to Trips Based on Biomechanical Principles

Takaaki Shiratori1,2

Rakié Cham3

Brooke Coley3

Jessica K. Hodgins1,2

31 2

Physical Simulation for Human Characters

Steady-state behaviors.

Reactive responses required.

Yin et al., 2007 Muico et al., 2009

1 http://lh6.ggpht.com/_UAku2WOHdSE/SlP6lTodsMI/AAAAAAAADOU/BFQRfrvySDM/

Interaction

1

Clear obstacle.

Reactive Response to Trips

Collision with obstacle. Recover balance.Obstacle

Motion capture data Simulation

Biomechanical Principles

Synthesize reactive responses.

Prior Work

Kudoh et al., 2002 Zordan et al., 2002

Simulation-based method

Ye et al., 2008

Biomechanics-based method

Not applicable to tripping.

Not for human characters.

Macchietto et al., 2009Komura et al., 2004

Trip and slip for bipedal robots.

Boone et al., 1997

Strategies

Clearancewith tripped leg

Clearance withnon-tripped leg

Flight phase ordouble support

Flight phase ordouble support

Touchdown

Touchdown

Push-offreaction

Push-offreaction

Strategy selection

Collision in late swing

(40-75% of entire swing)

Collision in early swing(5-50% of entire swing)

Elevating strategy

Lowering strategy

[Eng et al. 1994, Schillings et al. 2000, Pijnappels et al. 2004, 2005]

Leg swap

Ground reaction force vector passes anteriorly to the COM.

Push-off Reaction

[Pijnappels et al. 2005]

Reduce forward angular velocity.

Increase moment of inertia to reduce angular acceleration.

Arm ipsilateral to tripped legmoves in sideward direction.

Arm contralateral to tripped legmoves in forward direction.

Protect head/chest.

Arm Motions

[Roos et al. 2008, Pijnappels et al. 2008]

Subjects must not know when/where tripping occurs.

Capturing Tripping Motion

Trip machine

Harness

Semi-rigid shoe

Trip slide

Look here

Elev.-DS Elev.-FL Lower.-DS Lower.-FL

# subjects 4 3 4 3

Speed [m/s](SD)

1.15(0.146)

1.44(0.0751)

0.942(0.191)

1.44(0.232)

Motion Capture Dataset

(DS: double support FL: flight phase)

Elevating Lowering

Faster walking speeds tend to lead to Flight Phase.

Elev.-DS Elev.-FL Lower.-DS Lower.-FL

# subjects 4 3 4 3

Speed [m/s](SD)

1.15(0.146)

1.44(0.0751)

0.942(0.191)

1.44(0.232)

Human Model

Create a 3D skin model from ~400 optical markers. Calculate mass and moment of inertia from volume.

[Park and Hodgins 2006]

42 DOFsin total

96 contact pointsper foot.

Finite state machine with Proportional Derivative (PD) servo.

Controller Overview

Yes

Collision PassiveReaction Clearance FlightSingle Support

After Trip

DoubleSupportFall

Muscle activities

start.

Leading legcontactsground.


Trailing leg leaves ground.

No

Leg Swap

Flight phase?Strategy?

COM startsfalling.

Tripped legtouches ground.

Elevating

Lowering

Controller for Tripping Reactions

ElevatingYes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Lowering


COM startsfalling.


Baseline walkingPlayback of motion capture data.

SimulationInitialized with tripping forces just before trip occurs.

Simulation initialization


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap


COM startsfalling.


Observed tripping forces. Vertical: sine function Fore-aft: Gaussian function[Pijnappels, et al., 2004]

100

50

0

-50

-100

-150

-2000 0.020.040.060.080.10

Force [N]

Time [sec]

Fore-aft (x)Vertical (z)

x

z

Elevating

Lowering

Simulation initialization


Yes

Collision Clearance FlightSingle Support

After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Support legControl attitude of upper body.

Swing leg Moving forward like walking.Target angles: motion capture data of walking.

PassiveReaction

Elevating

Lowering

Knee torque


Yes

Collision Clearance FlightSingle Support

After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


PassiveReaction

Muscle activities

start.

Elevating

Vastus lateralis

Rectus femoris Transit: touch sensor brain muscle

Muscle recruitment (40 msec)

[Schillings et al. 2000][Pijnappels et al. 2005]

[Ralston et al. 1976]

Lowering

Support knee

0: tripping instant

Controller for Elevating Strategy

Yes

Collision FlightSingle Support

After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Elevatingstrategy?

COM startsfalling.


PassiveReaction

Muscle activities

start.Strategy?

Clearance

Support legPush-off reaction: Extend all joints.Compensation torque to ankle for COM.

)( zdzcc vvk

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Elevatingstrategy?

COM startsfalling.


Muscle activities

start.Strategy?

Clearance

Swing legClear the obstacle.Target angles:motion capture data.

Motion capture Simulation

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance

Flight phase?

Flight

Leading legExtended for touchdown.Target angles:motion capture data.

Trailing legStart flexion. Motion capture Simulation

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance Flight


Single SupportAfter Trip

Leading legControl attitude of upper body.

Trailing legMove forward for the next step.

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance

Flight phase?

COM startsfalling.

Leading legExtended for the next stepTarget angles:motion capture data.

Trailing legControl attitude of upper body.Keep extension. Motion capture Simulation

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance


DoubleSupport

Leading legControl attitude of upper body and extend knee.

Trailing legControl attitude of upper body .Plantar-flex ankle for the next step.

Elevating

Lowering


Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance

DoubleSupport


Single SupportAfter Trip

Leading legControl attitude of upper body.

Trailing legMove forward for the next step.

Elevating

Lowering

Controller for Lowering Strategy

Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Flight phase?

PassiveReaction

Elevatingstrategy?

COM startsfalling.


PassiveReaction

Muscle activities

start.Strategy?

Clearance

Leg SwapLeg Swap

Swing leg (tripped)Extended for touchdown immediately.

Elevating

Lowering

Controller for Lowering Strategy

Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance

Leg Swap

Swing leg (tripped)Extended for touchdown immediately.

Support leg (non-tripped)Leaves ground after swing leg touchdown.Clear the obstacle.


Leg Swap

Clearance

Elevating

Lowering

Start reaction.Timing: 100 msec

Target angles:motion capture data.

Control of Arm Motion

Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


Clearance

Leg Swap

Clearance

Motion capture Simulation

[Pijnappels et al. 2008]

Elevating

Lowering

Control of Arm Motion

Yes


After Trip

DoubleSupportFall

Muscle activities

start.




No

Leg Swap

Flight phase?

PassiveReaction

Strategy?

COM startsfalling.


ClearanceSingle Support

After Trip

Back to motion in normal walking.

Motion capture(walking)

Simulation

Elevating

Lowering

Elevating strategy with double support.Input walking speed: 1.0 m/s

Simulation Result

Elevating Lowering

DS FL DS FL

Elevating strategy with flight phase.Input walking speed: 1.4 m/s

Simulation Result

Elevating Lowering

DS FL DS FL

Lowering strategy with double support.Input walking speed: 0.75 m/s

Simulation Result

Elevating Lowering

DS FL DS FL

Lowering strategy with flight phase.Input walking speed: 1.1 m/s

Simulation Result

Elevating Lowering

DS FL DS FL

Elevating strategy with flight phase.

Comparison with Motion Capture Data

-100

-80

-60

-40

-20

0

20

-0.5 0 0.5 1.0

Pitch [deg]

Time [sec]-20

0

20

40

60

80

100

120

-0.5 0 0.5 1.0

Pitch [deg]

Time [sec]

Hip Knee

: tripping instant : simulation result : motion capture data

Elevating strategy with flight phase.

Comparison with Motion Capture Data

Foot trajectory Pelvis-10-5 0 5

10 15 20 25 30 35 40 45

-0.5 0 0.5 1.0

Pitch [deg]

Time [sec]0

0.1

0.2

0.3

0.4

0.5

0 0.5 1.0

Height [m]

Length [m]

: tripping instant : simulation result : motion capture data

Root mean square errors Unit: [deg/frame] (frame rate = 120 Hz)

Quantitative Comparison

Recovery with multiple steps.

Discussion

Better contact model Many force plates. Larger marker set for feet. More precise model of tripping forces.

Discussion

Push-off reaction Tripping forces.

Controllers for strategies of balance recovery responses to trips.

GraphicsIntegrate walking controllers.Other reactive responses.

Biomechanics applicationAnswer “what if” questions.Improve training and rehabilitation systems.

Summary

1 2

3

2 http://www.yamakai.org/profiles/marriott.html 1 http://www.youtube.com/watch?v=LVStmLCoH30

3 http://www.treadmilladviser.com/landice-l7-rehabilitation-treadmill.html

Adam Bargteil for help with calculating mass and moment of inertia.

Moshe Mahler for rendering animation. Justin Macey for the human model. Subjects for participation in the experiments.

NSF -0540865 Quality of Life Technology Engineering Research Center

F31 AG025684-03 NIH Ruth L. Kirschstein Award Autodesk for Maya donation.

Acknowledgements

Documents

Simulating Balance Recovery Responses to Trips Based on Biomechanical Principles Takaaki Shiratori 1,2 Rakié Cham 3 Brooke Coley 3 Jessica K. Hodgins 1,2