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Benjamin Stephens - PPT Presentation

Carnegie Mellon University 9 th IEEERAS International Conference on Humanoid Robots December 8 2009 Modeling and Control of Periodic Humanoid Balance Using the Linear Biped Model Introduction ID: 174067

balance control force humanoid control balance humanoid force biped linear robot model support periodic dynamics double controlled mass simple feet swaying motion

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Slide1

Benjamin StephensCarnegie Mellon University9th IEEE-RAS International Conference on Humanoid RobotsDecember 8, 2009

Modeling and Control of Periodic Humanoid Balance Using the Linear Biped ModelSlide2

Introduction2Slide3

Motivation3

Simple models for complex systemsMake complex robot control easier

Models for human balance control

Achieve stable balance on force-controlled robotSlide4

Force Controlled Balance4

How to handle perturbations when using low-impedance control on a torque-controlled humanoid robotSlide5

Force Controlled Balance5

How to handle perturbations when using low-impedance control on a torque-controlled humanoid robotSlide6

Sarcos Humanoid Robot6

Hydraulic ActuatorsForce Feedback Joint Controllers33 major DOFs (Lower body = 14)

Total mass 94kg

Off-board pump (3000 psi)

Sarcos

Hydraulic Humanoid RobotSlide7

Contributions7

Linear biped model for force control of balanceSimple description of periodic balance control

Application of model to estimation and control of Humanoid robotSlide8

OutlineModeling BalanceControlling BalanceApplications to Humanoid Robot ControlConclusion

8Slide9

Modeling Balance

9Slide10

General Biped BalanceAssumptions:Zero vertical accelerationNo torque about COM

Constraints:COP within the baseof support

10

REFERENCE:

Kajita

, S.;

Tani

, K., "Study of dynamic biped locomotion on rugged terrain-derivation and application of the linear inverted pendulum mode,"

ICRA 1991Slide11

General Biped Balance Stability11

COM Position

COM Velocity

Linear constraints on the COP define a linear stability region for which the ankle strategy is stable

REFERENCE:

Stephens, “Humanoid Push Recovery,” Humanoids 2007Slide12

The Linear Biped ModelContact force is distributed linearly to the two feet.

12Slide13

The Linear Biped ModelBiped dynamics resemble two superimposed linear inverted pendulums.

13Slide14

The Double Support Region14

We define the “Double Support Region” as a fixed fraction of the stance width.Slide15

Dynamics of Double Support15

The dynamics during double support simplify to a simple harmonic oscillator

LIPM DynamicsSlide16

Controlling Balance

16Slide17

Phase Space of LiBM

Location of feet

Double Support Region

17Slide18

Periodic BalanceGoal: Balance while moving in a cyclic motion, returning to the cycle if perturbed.

18

Slow Swaying

Fast Swaying

Marching in Place or WalkingSlide19

Orbital Energy ControlOrbital Energy:Solution is a simple harmonic oscillator:We control the energy:

19Slide20

20Slide21

Energy Control Trajectories

21Slide22

22Slide23

23Slide24

Application to Humanoid Balance

24Slide25

Humanoid Applications25

Linear Biped Model predicts gross body motion and determines a set of forces that can produce that motion

State Estimation

Combine sensors to predict important features, like center of mass motion.

Feed-Forward Control

Perform force control to generate the desired ground contact forces.Slide26

Center of Mass Filtering26

A (linear) Kalman Filter can combine multiple measurements to give improved position and velocity center of mass estimates.

Joint Kinematics

Hip

Accelerometer

Feet

Force Sensors

Kalman

Filter

Periodic Humanoid Balance

CoM

StateSlide27

27Slide28

Feed-Forward Force Control28

LiBM can be used for feedforward control of a complex biped system.

Full-body inverse dynamics can be reduced

to force control of the COM with respect

to each foot

Additional controls are applied to bias

towards a home pose and to keep the

torso vertical.Slide29

29Slide30

30Slide31

31Slide32

32

Impulsive Push

Limit CycleSlide33

Robot Experiments33Slide34

Future Work34

3D Linear Biped ModelRobot BehaviorsFoot PlacementPush Recovery

Walking

Robust Control/Estimation

Push Force Estimation

Robust control of

LiBMSlide35

Conclusion35

Linear biped model for force control of balanceSimple description of periodic behaviors and balance control

Applied to estimation and control of humanoid robot

Slow Swaying

Fast Swaying

Marching in Place or Walking

Joint Kinematics

Hip

Accel

Force Sensors

Kalman

Filter

Periodic Humanoid Balance

CoM

State

Thank you. Questions?Slide36

Thank you36

Questions?Special thanks to supporters:National Science Foundation

Quality of Life Technology Engineering Research CenterSlide37

The Linear Biped ModelContact force is distributed linearly to the two feet.

37