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Recursive Robot Dynamics Lecture 1 Prof. S.K. Saha ME Dept., IIT Delhi

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Page 1: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Recursive Robot Dynamics

Lecture 1

Prof. S.K. Saha ME Dept., IIT Delhi

Page 2: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

What is recursive?

1

#n

#1

#i

i

n

#1: vel., accn.

1: rate, accn

+ #0

#i: vel., accn.

#n: vel., accn.

#n: inertia force

n: torque

i: torque

#i inertia force

#1:inertia force

#0: vel., accn. = 0

1: torque

Page 3: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Why recursive?

• Efficient, i.e., less computations and CPU time

Compute jt. torque Compute jt. accn. (Inverse) (Forward)

0 5 10 15 20 25 30

0

2000

4000

6000

8000

10000

12000

14000

Total number of joints

Co

mp

uta

tio

na

l C

ou

nts

Equal number of 1-, 2- and 3-DOF joints

Proposed

Balafoutis

Featherstone

Angeles

0 5 10 15 20 25 30

0

0.5

1

1.5

2

2.5x 10

4

Total number of joints

Co

mp

uta

tio

na

l C

ou

nts

1-, 2- and 3-DOF joints

Proposed

Mohan and Saha

Lilly and Orin

Fetherstone

Ref. : Shah, S.,V. Saha, S.K., Dutt, J.K, Dynamics of Tree-type Robotic Systems, Springer, 2013

Page 4: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Why recursive? (contd.)

• Numerically stable Simulation is realistic Recursive Non-recursive (Forward) (Forward)

Ref. : Mohan, A., and Saha, S.K., A recursive, numerically stable, and efficient simulation algorithm for serial robots with flexible links, Multibody System Dyn., V. 21, N. 1,pp. 1—35.

Page 5: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Unrealistic: Constraint Violation

#0

#1

1

#2

#3

2

3 θ3

θ1 θ2

Page 6: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Review of Dynamic Formulations

• Euler-Lagrange (EL)

• Newton-Euler (NE) i i i

i i i i i i

m

v f

I ω ω I ω n

i

i i

d L L

dt q q

i i i i i i M t WM t w

, ,i i ii

i i i i

i i im

I O ω nω 1 ΟM W t ,w

O 1 v fΟ Ο

Starting point for the Recursive Dynamics (using the DeNOC matrices)

Page 7: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

DeNOC matrices

Newton-Euler to Euler-Lagrange

• Analytical expressions of vector and matrices,

Decomposition of inertia Matrix, Recursive algorithms,

Dynamics model simplifications, etc.

,

Decoupled form of the velocity transformation matrix

Minimal order Equations of motion

(Euler-Lagrange)

Newton-Euler Equations of

motion ×

Eliminate constraint forces and moments from the NE equations.

Rate of Independent coordinate θ.

Link velocities t (ω and v) = ×

DeN

OC

m

atri

ces

=

Page 8: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Example: A Moving Mass

: Vertical component Reaction

: Horizontal component Motion

Mass, m

Force,

f

fvf

vf

f

x

Page 9: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Equation of Motion

Newton’s 2nd law: Velocity constraint: NOC: Euler-Lagrange:

cff mce

x ][ic

][i

ef

[ ] [ ( ) ] [ ]T Tv cf f f mx f mx i i j i i

External force,

Mass, m

i

j

c

cfReaction,

Note that

[ ] ( )[ ] 0Tv cf f i j

Page 10: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Uncoupled NE Equations

• Newton-Euler (NE) equations for the ith rigid body

• NE equations in compact form

where

i

i i i i i i

i im

I ω ω I ω n

v f

i i i i i i M t WM t w

, , ,i i ii

i i i i

i i im

I O ω nω 1 ΟM t W w

O 1 v fΟ Ο

Page 11: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Uncoupled NE Equations

#0

1

#n

#1

#i

i

n

E C

i i i i i i i M t WM t w w

E C Mt WMt w w

1 2

1 2

diag [ ]

diag [ ]

n

n

M M M M

W W W W

• Separate the bodies n bodies

• 6n NE equations

Page 12: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Kinematic (Velocity) Constraints

Bij: the 6n 6n twist-propagation matrix

pi: the 6n-dimensional joint-rate propagation vector or twist generator

( )

ij

ij j i

c

1 O

B r d 1 1i

i

i i

ep

e d

Page 13: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

DeNOC Matrices

• NNlNd: the 6n n Decoupled Natural Orthogonal Complement

Page 14: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Coupled Equations of Motion

• Pre-multiplication by NT

• Equations in compact form

I : nn Generalized inertia matrix (GIM)

C : nn Matrix of convective inertia (MCI) terms

: n-dimensional vector of generalized forces due to driving torques/forces, and those resulting from the gravity, environment and dissipation.

Iθ Cθ τ

τ

)()( CETTwwNWMttMN

n coupled EL equations

- no partial differentiation T C N w 0

Page 15: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Generalized Inertia Matrix (GIM)

• Generalized inertia matrix (GIM)

where

• Each element of the GIM

• Mass matrix of composite body

15

T

ij i i ij ji p M B p

1, 1 1,

T

i i i i i i i M M B M B

Td dI N MN

l

T

l MNNM ~

Page 16: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Vector of Convective Inertia (VCI)

• Vector of Convective Inertia

where and

• Each element of h

'

1, 1

where , and

and

T

i i i

T

i i i i i n n

i i i i i i

h p w

w w B w w w

w M t W M t

'~wNθChT

d

)('~ WMtMt'Nw T

d θWNNt' )( ll

Page 17: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Generalized Force (Joint Torque)

• Generalized Force

where

• Each element is obtained recursively

1, 1

,

where , and

T E

i i i

E E T E E E

i i i i i n n

p w

w w B w w w

T Edτ N w

ET

l

EwNw ~

Page 18: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Example: One-link arm

11

2

( )

1

3

T

T T

I i

m ma

p Mp

e Ie (e d) (e d)

where and m

e I Op M M

e d O 1

;

TT asac ]02

1

2

1[][ ;]100[][ 11 de

20 0 0

[ ] 0 1 012

0 0 1

ma

2

I

2

22

0

[ ] [ ] 012

0 0 1

s s c

maT s c c1 2

I Q I Q

100

0

0

cs

sc

Q

Ref: “Introduction to Robotics” by Saha

Moment of inertia about O

Page 19: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

where

( )

[ )] 0

T

T

h

p MW WM p

e I(e e) (e Ie

f

ndeewN ])([1

TTET

l

TT mg ]00[][;]00[][ 11 fn

mgas2

11

Equation of motion: 21 1

3 2ma mgas

Page 20: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

1

#n

#1

#i

i

n

#0

1 1 1

2 2 2 1

1n n n n

α p

α p α

α p α

1 1 1 1 1 1

2 2 2 2 2 2

21 1 21 1

, 1 1 , 1 1

n n n n n n

n n n n n n

β p Ω p

β p Ω p

B β B α

β p Ω p

B β B α

Recursive Inverse Dynamics

1 1 1 1 1 1 , 1

1 1 1 1 1 1 21 2

n n n n n n

T

n n n n n n n n n

T

γ M β W M α

γ M β W M α B γ

γ M β W M α B γ

1 1 1

1 1 1

T

n n n

T

n n n

T

p γ

p γ

p γ

Page 21: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Recursive Robot Dynamics

Lecture 2

Prof. S.K. Saha ME Dept., IIT Delhi

Page 22: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Summary of Previous Lecture

• Why recursive?

• Define DeNOC (Decoupled Natural Orthogonal Complement) matrices from velocity constraints

• Derived NE EL equations (Constrained minimum set)

• Analytical expressions for the GIM, and other matrices

Page 23: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Equation of motion (Dynamic Model)

21 1

3 2ma mgas

One-link Arm

Page 24: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Chinese (PRC)

Spanish (Mexico)

RoboAnalyzer (Free: www.roboanalyzer.com)

Page 25: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

where

( ) [ )] 0T Th p MW WM p e I(e e) (e Ie

f

ndeewN ])([1

TTET

l

TT mg ]00[][;]00[][ 11 fn

mgas2

11

Equation of motion: 21 1

3 2ma mgas

2

11

1( )

3

T T TI i m ma p Mp e Ie (e d) (e d)

Verify the results using MATLAB’s symbolic tool (MuPAD)

Page 26: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Example: Two-link Manipulator ;

11 12 21 1 1

21 22 2 2

( ); ;

i i i h

i i h

I h Cθ τ

22 :ScalarTi 2 2 22 2p M B p

2222222222222 ][][][][][ ddeIeTT mi

22 : 6 6 identity matrix

1 OB

O 1

2

2

2 2

: 6-dim. vector

ep

e d

2

2 2

2

: 6 6 sym. matrixm

I OM M

O 1

X3

Y3

Page 27: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

2 2 2 2 2 2 2 21 1

[ ] [0 0 1] ; [ ] [ 0]2 2

T Ta c a s e d

2 2

2 2 2

0

0

0 0 1

c s

s c

Q

22 2 2

22

2 2 2 2 2 2 2

0

[ ] [ ] 02 3 120 0 1

T

s s c

mas c c

I Q I Q

2222222222222 ][][][][][ ddeIeTT mi

2 2 222 2 2 2 2 2 2

1 1 1

12 4 3i m a m a m a

X3

Y3

Page 28: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

;

21 12 1 1( ) :ScalarTi i 2 2 2p M B p

21 2 1 2 1 1 1 2 2 1 1 1 1 2 1[ ] [ ] [ ] [ ] ([ ] [ ] )T Ti m e I e d d r d

211 2

: 6 6 matrix( )

1 OB

r d 1 1

2 1 2 1 1 2 2 2 12 2 12

1 1 1 1 1 1 1 1 2 1

1 1[ ] 0 0 1 ; [ ] [ ] [ 0]

2 2

1 1[ ] [0 0 1] ; [ ] [ ] [ 0]

2 2

T T

T T

a c a s

a c a s

e d Q d

e d r

r1 1 1

1 1 1

0

0

0 0 1

c s

s c

Q

2 2 221 2 2 2 1 2 2 2 2 2 2 2 1 2 2

1 1 1 1 1

12 2 4 3 2i m a m a a c m a m a m a a c

1

1

1 1

: 6-dim. vector

ep

e d

Page 29: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

11 1 1 11 1 :ScalarTi p M B p

11 : 6 6 identity matrix

1 OB

O 1

1

1

1

: 6 6 sym. matrixm

I OM

O 1

X3

Y3

11δ

1δIBMBMM 2

11

11212111 ~

~~~

m

T

12 21

1 1 2 2 1 2 1

( )

( )m

c c

I I I r d δ 1

2121

~cδ m

211~ mmm

11 1 1 1 1 1 1 1 1 1 1

2 2 21 1 2 2 2 1 2 1 2 2

[ ] [ ] [ ] [ ] [ ]

1 ( )

3

T Ti m

m a m a m a m a a c

e I e d d

Page 30: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Vector of Convective Inertia

Link Joint ai

(m)

bi

(m)

i

(rad)

i

(rad)

1 r 0.3 0 0 JV [0]

2 r 0.25 0 0 JV [0]

22 2 2 2 1 2 2 1

1

2

Th m a a sθ θ p w 1 1 2 1 2 2 2 2 11

( )2

Th m a a sθ θ θ θ 1 p w

Link mi ri,x ri,y ri,z Ii,xx Ii,xy Ii,xz Ii,yy Ii,yz Ii,zz

(kg) (m) (kg-m2)

1 0.5 0.15 0 0 0 0 0 0.00375 0 0.00375

2 0.4 0.125 0 0 0 0 0 0.00208 0 0.00208

DH

an

d I

nert

ia p

ara

me

ters

Inverse Dynamics Results

Page 31: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Joint Torques

No gravity (horizontal)

With gravity (vertical

Page 32: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Equation of motion for one-link arm

21 1

3 2ma mgas

Forward Dynamics & Simulation

2

3 1( )

2mgas

ma Forward Dynamics:

Integration (numerical): 1 2

1 2

2 12

;

3 1( sin )

2

y y

y y

y mga yma

1st order form:

( , )ty f y

Integrate (say, numerically) to obtain y(t) using, e.g., Runge-Kutta method (ode45 of MATLAB)

Simulation

Page 34: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Recursive Forward Dynamics

θ

34

Step 2: UDUT Decomposition

, where andT T

Analytically

UDU θ I UDU τ Cθ

Equation of the motion

The joint accelerations are then solved as

1 1θ U D U

T

Hence forward dynamics requires three steps

Step 1: Computation of φ

Step 3: Recursive computation of

Iθ Cθ τ

Page 35: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Observations

• Derivations appear to be complex for the simpler manipulators

• It was for demonstration only

• The computations will be done algorithmically

• Due to recursive natures, calculations are fast

• The algorithm should be used for complex robotic systems like 6- or more-DOF robots

Page 36: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Recursive Robot Dynamics

Lecture 3

Prof. S.K. Saha ME Dept., IIT Delhi

Page 37: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Summary of Previous Lecture

• Use of RoboAnalyzer (RA) for inverse dynamics of one-link arm

• GIM for 2-link manipulator

• Inverse dynamics of KUKA robot

• Forward dynamics and simulation

• Use of RA for simulation

• Some observations for using recursive dynamics

Page 38: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Stew

art

Pla

tfo

rm

Parallel Manipulators

Page 39: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Four-bar Mechanism • Separate all links • Draw Free-body diagrams (FBD)

12 12

1 1 1 1 01 1 01 1 21 1 21

1 1 01 21 1 1 01 21;

x y

x y y x x y y x

x x x y y y

f f

I d f d f r f r f

m c f f m c f f

=

Equations of motion: 3 per link

Base, #0

#1

#3

C1

#2

f12

f21

f01

f32

f23

f03

d1

r1

#1

#2

a3

2

3

1

3 2

1 4

a2

a0

a1

Base, #0

#3

4

1

9 equations 13 – 4 (3rd law) = 9 unknowns

Page 40: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

11 1 1 1 1 1

01 1 1

01 1 1

122 2 2 2 2 2

12 2 2

23 2 2

233 3 3 3 3

03

03

1

1 1 0 '

1 1

1 1

1 1

0 ' 1 1

1 1

y x y x

x x

y x

xy x y x

x x

x y

yy x y x

x

y

d d r r I

fs m c

f m c

fd d r r I

f m c

f m c

fd d r r I

fs

f

3

3 3

3 3

: 9 9 matrix x : 9 1 : 9 1

x

y

m c

m c

A b

• Ghosh and Mallik, Theory of Machines and Mechanisms

1 (Forward); (Backward)y

x=A b LUx=b; Ly=b Ux=y

Disadv.: Need to calculate even the reactions for inv. dyn.

Page 41: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Three-link Serial with f03 as External • Join first three links form

Equations of motion

Base, #0

#1

#3

C1

#2

f12

f21

f01

f32

f23

f03

d1

r1

Base, #0

033 3

( ) ( )

: 3 eqs.T

T T T T E Cd l d l

E C

J f

N N Mt WMt N N w w

I θ Cθ τ τ0 1 2 3

2 3

0

a a a a 0 J θ 0

#1

#2

a3

2

3

1

3 2

1

a2

a1

#3 1

f03 a0

Page 42: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

• The DeNOC matrices for 3-link serial manipulator

Proof of C = JTf03

1 1 1

2 21 2 2

3 31 32 3 3

18 1 :18 18 :18 3 3 1

0' 0 '

0 '

l d

s s

s

N N

t 1 p

t B 1 p

t B B 1 p

32 21 31 21 32 31

2

1 21 2 32 3

21 31 1

32 2 2 32 3

3

3

( )

0 '

T T T

C

C T C T C

T T C

T C T C C T Cl

C

C

s

B B B B B B

w

w B w B w

1 B B w

N w 1 B w w B w

1 w

w

03 23 3 23 3 03

3

03 23

C

n n d f r fw

f f2 3

32

6 6

( )

0 '

T

s

1 r d 1B

1

f03

f23

r3

d3 n03

n23

C3

Page 43: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

23

23

32 12 2 12 2 32

2 2 32 3

32 126 1

03 23 3 23 3 03 2 3 03 23

03 23

( ) ( )

C C T C

n

f

n n d f r f

w w B wf f

n n d f r f r d f f +

f f

2

03 12 2 3 3 03 2 12

2

03 12

( )C

p

n n r d r f d f

w

f f

03 01 1 03 1 01

1

03 01

C

n n p f d fw

f f

C2

r3 2

3

1

3 2

1

r2

1

f03

p2

p1

d3

Page 44: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Constraint Torque 1 1

2 2

3 3

0 '

0 '

T C

T C T Cd

T C

s

s

p w

N w p w

p w

( 1,2,3)i

ii i

i

ep

e d

03 01 1 03 1 01

1 1 1 1 1 1

03 01

1 03 01 1 03 1 01

1 1 03 01

1 1 03 1 1 03

( )

( )

( ) ( )

( ) ( )

C T C T T

Scalar

T

T

T T

n n p f d fp w e e d

f f

= e n n p f d f

e d f f

= e ρ f e ρ f

2 2 2 2 2 03 2 2 03

3 3 3 3 3 03 2 3 03

( ) ( )

( ) ( )

C T C T T

C T C T T

p w e ρ f e ρ f

p w e a f e a f

C2

a3 2

3

1

3 2

1

r2

1

f03

p1

1

d2

Page 45: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Equations of Motion

*1 03[ ,0,0]:

T T

E C

known

J fτ

Iθ Cθ τ τ

3

1 1 2 2 3 3

a

J e ρ e ρ e ρ

*1 1 1 2 12 3 123 1 1 2 12 3 123 1*2 2 12 3 123 2 12 3 123 03

*3 123 3 123 033

:3 3 :3 1:3 1

1

0

0

x

y

a s a s a s a c a c a c

a s a s a c a c f

a s a c f

A xb

Adv.: Reduced size of 33 (instead of 99) for inverse dynamics

Page 46: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Subsystem Recursive Method • Cut-open in a suitable location • Make serial systems • Apply serial-chain methods

( )I I I I I C I I θ C θ τ τ

( )II II II II II C II I θ C θ τ τ

Subsystem equations

: 2 eqs., 2 (x, y)? [2R: done]

: 1 eq., 3 (, x, y)? [1R: done]

1 0 2 3 a a a a

#1 #3

4

3

1

1

Base, #0

#2

#1

#2

a3

2

3

1

3 2

1 4

a2

a0

a1

Base, #0

#3

4

1

4

f12 (-)

f21 ()

123

2-3

Page 47: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

I I II II J J θ

3 123 2 12 2 121 1

2 1 2 2 3 123 2 12 2 121 1

;

I I I II II IIen ln d en ln d

I II a s a s a sa s

a c a c a ca c

A N N A N N

J J

1 2 3 a a a

[0,0] ( )

( )T

II T

II II II II II C II

J λ

I θ C θ τ τ

1( )

( )T

I I I I I C II C

J λ

Subsystem II:

Subsystem I:

System + Motion

Solve

System + Motion Driving torque, 1

Adv.: Subsystem recursion.; Maximum size: 22 (not 99 or 33); Can use existing serial-chain dyn. algo.

123

3

1

1

2

;

II

I II

II

θ

Page 48: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Sub-system

(link) Mass (Kg)

Length (m)

I(#1) 1.5

0.038

II(#2) 5

0.2304

II(#3) 3

0.1152

0 0.5 1 1.50

50

100

150

200

250

300

350

400

Time (s)

Jo

int

an

gle

s (

de

g)

0 0.5 1 1.5-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

Time (s)

Dri

vin

g t

orq

ue

(N

m)

3

1

2

Free: http://www.redysim.co.nr/download

Page 49: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Recursive Robot Dynamics

Lecture 4

Prof. S.K. Saha ME Dept., IIT Delhi

International 2013

Int.: 2009 Indian: 2013

Page 50: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Summary of Previous Lecture

• Dynamics (classical way) of 4-bar mechanism using FBD

• Cut-open 3+0 constrained dynamics of 4-bar

• Cut-open 2+1 constrained dynamics of 4-bar

• Inverse dynamics using ReDySim

Page 51: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Forward Dynamics of 4-bar Mechanism

[0,0] ( )

( )T

II T

II II II II II C II

J λ

I θ C θ τ τ

11 ( )

( )T

I I I I I C II C

J λ

Constrained equations of motion:

1

:5 1:5 5 :5 1

)

0 ) -

I I T I I I

II II T II II II

I II I I II II

I C

xA b

O (J

I -(J θ C θ

J -J O λ -J J θ

0II II

II

J -J

0θVelocity constraints:

1x=A b

+ (jt. accn.) jt.

vel. & pos.

DAE [Diff. Algeb. Eqn.) formulation: System appr.]

Page 52: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

System-level Lagrange Multiplier Method

[0,0] ( )

( )T

II T

II II II II II C II

J λ

I θ C θ τ τ

Constrained equations of motion:

1

2

T

I J θ

J O λ

2

II II I I II II

II

J

θ

J -J -J J θθ

jt. vel. & pos. (jt. accn.)

1:3 1:3 3 :3 2

( )

0 ( )

T

I I TI I I I

II II TII II II II

I C

θI J

O J-λ

I Jθ τ -C θ

11 ( )

( )T

I I I I I C II C

J λ

Velocity constraints:

1 1 1

1 2

:2 2

( ) )T

I

λ JI J (JI

1

1( )T θ I J λ

Adv.: Inversions of smaller (33 and 22) matrices

Page 53: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Five-bar 2-DOF Manipulator

Base, #0

#1

2

1

2

1

a2

a0

a1 1

Cut

here

#1

2

1

2

1

a2

a0

a1 1

-

Base, #0

( )I θ C θ τ τI I I I I I

( )I θ C θ τ τII II II II II II

Subsystem equations

: 2 eqs., 1 (2 )? [2R done]

: 2 eqs., 3 (1, x, y)? [2R done]

Symmetric; Need to combine: 4 eqs., 4 (1, 2, x, y)?

2 2

Page 54: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Subsystem Recursion for 5-bar

Base, #0

#1

2

1

2

1

a2

a0

a1 1

Cut

here

#1

2

1

2

1

a2

a0

a1 1

-

Base, #0

( )I θ C θ τ τI I I I I I

( )I θ C θ τ τII II II II II II

Subsystem equations

: 1 eq., 1 (2 )? [1R done]

: 3 eqs., 3 (1, x, y)? [3R done]

No need to combine: Solved

2 2

Page 55: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Inverse Dynamics (w/o Gravity) Link lengths: 1 m; Mass of links: 6 kg

1 11 1

2[ sin( )]

2

f ii

T tt

T T

Page 56: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Inverse Dynamics (w/Gravity)

Page 57: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Two-DOF Parallel Manipulator

#0 O5

O3

#3 #2

#1

O4

F2

C2

C1

r2

c12

d1

O2

#4

F3

C3

C4

r3

c43

d4

O1

Cut here

P

x2

l1 l2

θ1

ao

1 2 0 l l a 0

Kinematic constraints

Link bi

(m)

θi

(m)

ai

(m)

αi

(m)

1 0 1 0 /2

2 b2 [JV] 0 0 0

Sliding velocity (constant): 0.1 m/sec.

Link mi

(kg)

ri,x, ri,y

(m)

ri,z Ii,xx, Ii,yy

(kg-m2)

1,2 655 0 .625 399

Two RP serial manipulators; Combined: 4 eqs., 4 (f1, f2, x, y)?

Page 58: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector
Page 59: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Three-DOF RRR Parallel Robot

Subsystem I: 5 eqs., 5 (D1, 2x, 2y, 7x, 7y )? Subsystem II: 1 eq.. 1 (D2)? Subsystem III: 1 eq.. 1 (D3)?

Page 60: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Inverse Dynamics of 3-DOF RRR Robot

Page 61: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Driving Torques (w/o gravity)

Page 62: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Driving Torques (w/gravity)

Page 63: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Six-DOF Parallel Robot: Stewart Platform

Page 64: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

#0

O1

O2

Subsystem I (3-DOF)

3 eqs.; 4 (x, y, x, f1)?

O1

O4

#3

#2

#1

O3

f λ

One particular limb

f1

fI

Moving platform

O2

#4

#5 O5

#3

#2

#1

O3

O4

O6 Cut joint

Dimensionless

links C3

C2

r3

c23

d2

C1

d23

d3 14

14

2I

T

1

T * g T λ

I I I I 2 I

TI 3

1I

*

0

( ) 0 +

1

f

e a

N w w = e a f

e

A A

f

Page 65: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

FBD of VII Subsystem

-fIλ -fII

λ

-fIIIλ

-fIVλ -fV

λ

-fVIλ

pp1 pp2

pp3

pp4 pp5

pp6

VII VII VII

c c c+ × =•

I ω ω I ω n

VII VII

cm =•

c f

VII

λ

I

c

p1 p6

λ

VI

f

n p 1 p 1

f

=

VII

c λ λ

I VI= f f f

Subsystem VII (6-DOF) 6 eqs.; Zero?

Page 66: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Inverse Dynamics Algorithm ;

VII

VII

6c

1 61 p1 p6

6c 1 6

VI:6 61

:6 1

:6 1

Ii

i

i

i

f

f

J

τ

h

n xs p s p

s sf y

1τ J h

;

Ref: Sadana, M., 2009, Dynamic Analysis of 6-DOF Motion Platform, M. Tech Project Report, IIT Delhi

Page 67: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Trajectory and actuating force

Using GUI

Page 68: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

More Robots using ReDySim

Planar biped

Waking leg (also used as carpet scrapping

mechanism)

Page 69: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Legged Robots

Spatial biped

Spatial quadruped

Page 70: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Flexible Rope using ReDySim

0

Ms

M1

Base

Mi Torsion

spring

Detail of the

module Mi

Page 71: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Conclusions • Purpose of Recursive Robot Dynamics

– Efficiency – Numerical stability

• DeNOC matrices for serial-chain • NE to EL derivations • Constrained equations of motion for serial-chain systems • Schemes for Inverse and Forward Dynamics (Simulation) • RoboAnalyzer software for robot dynamics • Parallel robot application • Four-bar mechanism from FBD • Cut-open system and subsystem recursion • ReDySim software • Five-bar, 3-DOF RRR, Stewart platform dynamics • Custom-made GUI for Stewart platform • Simulation of walking robots and rope using ReDySim

Page 72: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Acknowledgements

• Mr. Majid Koul

• Mr. Rajivlochana C.G.

• Dr. Suril V. Shah

• Mr. Mukesh Sadana

• Dr. Himanshu Chaudhary

• Students of IIT Delhi and other institutes who used the materials mentioned in the lectures and given feedbacks.

Page 73: Recursive Robot Dynamics - IIT Delhiweb.iitd.ac.in/~saha/mel416sudipto-rrd17-26apr2013.pdf · 2013. 4. 27. · Newton-Euler to Euler-Lagrange • Analytical expressions of vector

Thank you

For comments/questions:

[email protected]

http://web.iitd.ac.in/~saha