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ICRA 2015 Workshop onNext Generation of Space Robotic Servicing Technologies

May 26, 2012

Space Robotics Lab.Dept of Aerospace EngineeringTohoku University, Japan

Kazuya Yoshida

Recent results on contact dynamics controlfor capturing and handling a tumbling object

The Space Robotics Lab.Dept. of Aerospace Engineering

Tohoku University, JAPANDirected by Prof. Kazuya Yoshida

yoshida@astro.mech.tohoku.ac.jphttp://www.astro.mech.tohoku.ac.jp/home-e.html

Free-Flying Space Robot

Planetary Exploration Rovers Asteroid Sampling

Robotic Systems on ISS

The SPACE ROBOTICS

Lab.

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

Telerobotic Servicerin ARAMIS report, 1983

Satellite Servicing : Concept in early 80’s

SPACE APPLICATIONS OF AUTOMATION, ROBOTICS AND MACHINE INTELLIGENCE SYSTEMS (ARAMIS)-Phase II, By D. L. Akin, M. L. Minsky, E. D. Thiel, and C. R. Kurtzman, NASA-CR-3734, 1983

Satellite Servicing : Concept in early 80’s

Telerobotic Servicerin ARAMIS report, 1983

SPACE APPLICATIONS OF AUTOMATION, ROBOTICS AND MACHINE INTELLIGENCE SYSTEMS (ARAMIS)-Phase II, By D. L. Akin, M. L. Minsky, E. D. Thiel, and C. R. Kurtzman, NASA-CR-3734, 1983

Challenge to Satellite Servicing in Early Days of Space Shuttle Mission

STS-14(51A), 1984 Retrieval of malfunctioning Wester-6 satellite ©NASA

ETS-VII: Engineering Test Satellite forthe demonstration of RVD and

Space Robotic technologies1997-1999

Mission by National Space Development Agency, NASDA, Japan Purpose:

Study and demonstrate robotics capability for orbital missions and autonomous RVD technology

Feature:A 2m-long, 6 DOF manipulator arm is mounted on an unmanned base satellite. A sub-satellite is separated for the RVD experiments.

Mission:Launched on Nov. 28, 1997, the mission successfully completed bythe end of 1999.

► Orbital Express (2007, DARPA)was also successful in demonstrating RVD and robotics technology in space, including fuel transfer and target capture operation.

Dynamics and Control of Free-Flying Multibody Systems

Ground-based manipulator Free-flying manipulator

Control of Free-Floating Arms using Generalized Jacobian Matrix

(Umetani & Yoshida 1987, 1989) Expand conventional manipulator kinematics

by combining with the momentum equation.

xh = J*φ

φ = (J*)-1 xh

Technologies for Robotic Satellite Servicing

Rendezvous and Fly-around Orbital mechanics and control Proximity sensors, Visual inspection

Capture and Berthing Manipulator control Teleoperation, Latency, Bandwidth Reaction dynamics, Impact/contact dynamics

In-Orbit Servicing Tasks Refuel, Assemble, Exchange, Repair… De-orbit, Re-orbit

Robotic Satellite Servicing

ETS-VII / Orbital Express– A Milestone for Future Satellite Servicing– Success in capture & berthing of a

Cooperative target.– With a dedicated handle/gripper system,

and attitude stabilization of the target satellite.

Capture of a Non-Cooperative target is a key issue to the next step.

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

Impact/Contact:is a complex phenomenon that occurs when two or more bodies undergo a collision.

Impact/Contact/Collision

Object A Object B

Impact/Contact: occurs during a very short time. generates a large impulsive force. accompanies rapid energy loss and large

accelerations. sometimes changes mechanical properties

of the system

Two Modeling Approaches

discrete model continuous model

Real profile of the contact force

Example of measured contact normal force

High-Freq. Force

Low-Freq. Force

SPACE ROBOTICS, Jan. 14, 2015

Discrete model = impulse-momentum model

impact process is instantaneous. impact forces are impulsive. kinetic variables discontinuously change. other finite forces are negligible. collisions between rigid (very hard) bodies. single point contact occurs.

Assumption

Coefficient of RestitutionPoisson’s Model (momentum)

where,

compression part

total normal impulse

restitution part

Before Contact Contact After Contact

compression restitution

perfectlyelastic collision

perfectlyinelastic collision

Continuous model = force based model

impact process is a finite period of time. impact forces continuously change. bodies are deformable. impact forces depend on penetration depth. friction forces are also explicitly modeled.

Assumption

Contact Force Model

Before Contact Contact

Typical Normal Force during Contact:

coefficient

Contact Force Model

w/ damping w/o damping

linear damping nonlinear dampingHertz Model

Spring-DashpotModel

Impact-PairModel

Lee-WangModel

Hunt-CrossleyModel

Contact Dynamics in SpaceDyn

Hφ + c = τ + JTF

-F

F

Modeling of Contact Dynamics Dynamics of the system

Free-Flying Multibody Dynamics

＋

Modeling of Contact Force

ContactDynamics ＝

Contact force

Fn = kn(δn)s + dn(δn)t

Impact Dynamics: modeling

V1

V2

Rigid wall Mass point

Infinitesimal Contact

Impact Dynamics: modeling

V1

V2

Articulated rigid bodies Mass point

Impedance of articulated body system

Finite-time Contact

Stiffness + damping

Lumped mass system

Impact Dynamics: modeling

Dominant eigen-frequency is determined by lowest stiffness element

Insert soft element for longer contact duration and easy contact force control

Introduction of a low-stiffness element in the system

contact duration is prolonged. system’s eigen-frequency < force-control frequency contact-force control becomes possible. peak impulsive force becomes smaller. the continuous model is needed. the discrete model may be useful for approximation

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

Satellite Capture Model

絵

Impedance Control of a Space Robot

eiii FxKxDxM =∆+∆+∆

The equation of motion of a space robot

Ideal impedance characteristics

The joint torque to realize the ideal impedance characteristics

( ){ }{ } cFJMJH

xKxDMJJH

eT

i

iii

+−+

∆+∆+−=−−

−−

*11**

1*1** φτ

:::::::

*

*

xc

FJφ

Hτ

e

Joint torqueGeneralized inertia matrixJoint angleGeneralized Jacobean matrixExternal forceNonlinear velocity termHand position in the inertial frame

cFJH eT

+−= **φτ

The impedance characteristics Zas an evaluation index of impact

2sk

sdm ii

i ++≡Z

Uniaxial Satellite Capture Model

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

Impedance Matchingin contact-force control scenario

Kinetic energy of the target before the contact is fully absorbed by the chaser’s manipulator arm (under the impedance control)

Hard ImpactManipulator impedance is HighCoefficient of Restitution=1.0

Soft ImpactManipulator impedance is Low

“Impedance matching”Coefficient of Restitution=0.0

Contact Force Target Velocity

(Dr. Uyama’s thesis work)

Collaboration with Space Robotics Group, Tsukuba Space Center, NASDA

Nozzle of the Target：The motion of the target satellite is emulated based on the F/T sensor.

Capture Probe：Impedance Control

F/T Sensor

7DOF Robot Arm

F/T Sensor

A Case Study: Experiment

A Case Study: Target Model

DRTS Geostational SatelliteMass：1300 [kg] (EOL)Size of body：2.2 ×2.4 ×2.2 [m]Size of solar paddle：2.4 ×7.3 [m] (1 wing)

Size of nozzle coneφ296 [mm]×450 [mm]

X

Z

Impedance Matching

][

][

N/m50[N/(m/s)]500kg10

=

=

=

i

i

i

kdm

20 25 30 35 40 45-2

0

2

4

time [s]

forc

e [

N]

20 25 30 35 40 45-1.5

-1

-0.5

0

0.5

time [s]

forc

e [

N]

X方向

Z方向

*tim mZZ =≈

(Dr. Nakanisi’s thesis work)

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

Collision of two rigid bodies

Translational motion and rotational motion are coupled in general.

Case 1 Case 2

With a Sweet Spot contact, the rotational motion before the contact can be fully transferred to the translational motion.

•48

Model based simulation

Experimental result

𝑥𝑥

𝑦𝑦

Collision of two rigid bodies (Mr. Kobayashi’s thesis work)

With a flexible element in the system

Experimental result Model based simulation

(Mr. Kobayashi’s thesis work)

Technologies for Robotic Satellite Servicing

Rendezvous and Fly-around Orbital mechanics and control Proximity sensors, Visual inspection

Capture and Berthing Manipulator control Teleoperation, Latency, Bandwidth Reaction dynamics, Impact/contact dynamics

In-Orbit Servicing Tasks Refuel, Assemble, Exchange, Repair… De-orbit, Re-orbit

Agenda

Quick overview on motivation and previous developments

Contact modeling Contact control Impedance matching Contact with rotation

The Space Robotics Lab.Dept. of Aerospace Engineering

Tohoku University, JAPANDirected by Prof. Kazuya Yoshida

yoshida@astro.mech.tohoku.ac.jphttp://www.astro.mech.tohoku.ac.jp/home-e.html

Free-Flying Space Robot

Planetary Exploration Rovers Asteroid Sampling

Robotic Systems on ISS

The SPACE ROBOTICS

Lab.