Bilateral Control

2

Contents

Bilateral Control

Requirements

Problems

Velocity Measurement

Force Measurement

Acceleration Control

Bilateral Control Scheme

Experimental Results

3

Bilateral Control

Bilateral Control Operating at a distant environment without actually being there.

Two robots named master & slave

MASTER SLAVE

OPERATOR ENVIRONMENT

mxhumm

humD

humKmf

mm

mD sD

sx sm envm

sf envK

envD

4

Bilateral Control - Requirements

Bilateral Control

Telepresence Vivid tactile sensation

Transparency

Stability

MASTER SLAVE

OPERATOR ENVIRONMENT

mxhumm

humD

humKmf

mm

mD sD

sx sm envm

sf envK

envD

First mechanical bilateral controller by goertz A bilateral control system currently in the market (hmw.com) da Vinci minimal invasive surgical robot from intuitivesurgical.com

5

Bilateral Control - Problems

MASTER SLAVE

OPERATOR ENVIRONMENT

mxhumm

humD

humKmf

mm

mD sD

sx sm envm

sf envK

envD

6

Measurement – Quadrature Encoder

7

Measurement - Force

END

EFFECTOR

FORCE

SENSOR

ROBOT

ARM

d es

)(sCF)(aCF)(eCF

ROBOT

ARM

)(tx

)(tf

sk

sc

END

EFFECTORFORCE

SENSOR

Strain Gauge Force Measurement Instability due to flexible dynamic structure

Narrow measurement bandwidth

8

Velocity Measurement

Force Measurement

Robust Control

Control Architecture

9

Velocity Measurement

10

Velocity Measurement – S Method

1 1.2 1.4 1.6 1.8 2 2.2 2.4

0

5

10

15

20

25

time (sec)

Velo

city (

rad)

M Method

S Method

11

Velocity Measurement – S Method

1.9 2 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8

30

31

32

33

34

35

36

37

38

time (sec)

Velo

city (

rad)

M Method

S Method

12

Velocity Measurement – S Method

3.6 3.7 3.8 3.9 4 4.1 4.2

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

time (sec)

Velo

city (

rad)

M Method

S Method

13

Velocity Measurement – S Method

2.464 2.466 2.468 2.47 2.472 2.474 2.476 2.478 2.48 2.482 2.4840.24

0.26

0.28

0.3

0.32

0.34

0.36

0.38

0.4

0.42

time (sec)

Velo

city (

rad)

M Method (filtered)

S Method (filtered)

14

Disturbance Observer

tK1

J

1

s

1

s

1

Current

Controller

tKri

dis t

nJ stnK

dis t

15

Disturbance Observer

tK1

J

1

s

1

s

1

Current

Controller

tKri

tnK

dis t

nJ s

g

s g

dist

dist

ngJ

g

s g

ngJ

16

Disturbance Observer

tK1

J

1

s

1

s

1

Current

Controller

tKri

tnK

dis t

dist

ngJ

g

s g

ngJ

1

tnK

sin( )A Bt

- Experiments

0

0.5

1

1

nJ s

dist

tK 1

s

ref

ai

s

s g

17

Disturbance Observer - Experiments dist

tK1

J

1

s

1

s

1

Current

Controller

tKri

tnK

dist

ngJ

g

s g

ngJ

1

tnK

sin( )A Bt

dist

dist

tKtK1

J

1

J

1

s

1

s

1

s

1

s

11

Current

Controller

tKtKri

tnKtnK

dist

ngJngJ

g

s g

g

s g

ngJngJ

1

tnK

1

tnK

sin( )A Btsin( )A Bt

0 1 0.5

1,10 referencemA

18

tK1

J

1

s

1

s

1

Current

Controller

tKri

tnK

dist

ngJ

g

s g

ngJ

int

ref

t

dF B J K i

dt

t

Reaction Torque Observer

reactiont

int

ref

dis ext t

dF B J K i

dt

t t t

19

Reaction Torque Observer - identification

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

0

0.1

0.2

0.3

Friction varying with absolute position

Time (sec)

Dis

turb

ance (

Am

p)

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

2

4

6

Time (sec)

Positio

n (

rad)

Absolute Shaft Position

Disturbance

0.1*sin(pos+1)+0.15

20

Ideal Response is defined as

Same position response

Equal force response

Bilateral Control Architecture

TF=1

m s

m st t

p m s

F m s t t

, 0P F

(1)

(2)

(3)

21

Bilateral Control Architecture

dis

m m m m

dis ext

s s s s s

J

J

t t

t t t

1

1

disdismn m m m

dis

dis extdissn s s s s

dis

gJ

s g

gJ

s g

t t

t t t

(4)

(5)

(6)

mn m m

ext

sn s s s s

J

J

t

t t t

(With disturbance rejection)

22

Bilateral Control Architecture

m s

m s

(7)

(8)

(9)

2

2

m s

m s

m

m

t t t

t t t

t t t

t tt

(if Jm=Js) by ading and subtracting eqn. in 6

(Define new variables)

any controller can be used to make , zero.

control inputs , can be distributed as

t t

2

2

m s

m s

s

s

t t t

t t t

t t t

t tt

m s m s

m s m s

t t t

t t t

23

Bilateral Control Architecture

(7)

(8)

(9)

cmd

mt

cmd

m

res

m

disgs

s

2

1

sJ mn

cc KsD 2

res

s

res

m

dis

mt

hZ

cmd

s

cmd

m tt

res

m

cmd

st

cmd

s

res

scc KsD

2

res

s

res

m

disgs

s

dis

st

hZ

ob

ob

gs

g

res

s

ob

ob

gs

g

2

1 cmd

s

cmd

m

ref

s

ref

m

cM

1

PC

PC

cM

1

mnJ

snJ 2

1

sJ sn

24

What if Jm≠ Js

1 1

m sm s

mn sn

m s

mn sn

J J

J J

t t

t t

(10)

22

22

m s

mn sn

m s

mn sn

mm mn

mn

ss sn

sn

J J

J J

JJ

JJ

t t

t t

t t

t t

any controller can be used to make , zero.

control inputs , can be distributed as

(8) rewritten with different inertias.

(11)

25

Bilateral Control- Experimental Results

Maxon EC-40

400 watts

BLDC motor

Maxon EC-40

400 watts

BLDC motor

MASTER SLAVE

10000 ppr

Encoder

Maxon Des 70/10

Current Regulator

10000 ppr

Encoder

Object

dSPACE 1103 Real-time

Controller

Quadrature

Encoder

Interface

Po

we

rPC

40

0 M

HZ

pro

ce

sso

r ru

nn

ing

at 1

& 1

0 k

Hz r

ate

s

DAC output

Slave’s

Encoder

Master’s

Encoder

Analog current reference

Maxon Des 70/10

Current Regulator

26

Free Motion

(a) position response of master and slave sides

(b) External forces measured by Force observer

(c) Position error between master and slave sides

27

Soft Environment (sponge)

(a) position response of master and slave sides (b) External forces measured by Force observer

(c) Position error between master and slave sides (d) Sum of torques at master and slave sides

28

Hard Environment (Metal plate)

(a) position response of master and slave sides (b) External forces measured by Force observer

(d) Sum of torques at master and slave sides (c) Position error between master and slave sides

29

Soft & Hard Environments

(a) position response of master and slave sides (b) External forces measured by Force observer

(d) Sum of torques at master and slave sides (c) Position error between master and slave sides