This paper is focused on the motion control problem for a laparoscopic surgery robot assistant with an actuated wrist. These assistants may apply non-desired efforts through the patient abdomen. Therefore, this article studies these efforts, which have been measured by a force sensor located between the wrist and the endoscope, and how to remove gravity and friction actions in order to obtain the abdominal efforts. The measure of these efforts indicates if the movements are done accordingly to the fulcrum point. To achieve this goal, a new control strategy, based on the emulation of passive wrists behavior, is proposed. Such methodology allows the assistant to minimize efforts over the patient. Finally, this work presents the advantages of actuated wrists for possible future applications.

1. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
ACTIVE WRISTS ENDOSCOPE NAVIGATION
IN ROBOTIZED LAPAROSCOPIC SURGERY
Enrique Bauzano Núñez, Dr. Víctor Muñoz Martínez
Dra. Isabel García Morales, Belén Estebanez Campos
Dpto. Ingeniería de Sistemas y Automática
http://www.isa.uma.es
Universidad de Málaga (Spain)

2. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
OUTLINE
I. Introduction
II. Laparoscopic Navigation on Active Wrists
III.Force Interaction Model
IV.Control Strategy
V. Implantation and Experiments
VI.Conclusions and Future Works

3. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
I. INTRODUCTION

4. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
I. Introduction
Laparoscopic Surgery: “Accessing
to the abdominal cavity with especial
long instruments.”
LAPAROSCOPIC SURGERY
Advantages
 Lessen recovery time
 Limit post-operative complications
 Lower scars
Constraints
 Movement limitations
 Loss of touch and 3D perception
 Hand-eye coordination problems

5. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
I. Introduction
Proposal: “Solve the motion problem
for a laparoscopic surgery robot
assistant with an actuated wrist.”
GLOBE-SHAPED MOVEMENTS
{I} Fulcrum point
 Orientation angle
 Altitude angle
 External distance

6. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
ROBOTIC WRISTS COMPARATIVE
•  Null forces on abdomen
•  Precision depends on fulcrum
accuracy
•  Null forces on abdomen
•  Special instruments needed
•  Previous calibration
•  Voluminous mechanisms
•  No additional mechanisms on wrist
•  No special instruments needed
•  Low volume
•  May apply forces on abdomen
I. Introduction

7. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
II. LAPAROSCOPIC NAVIGATION
ON ACTIVE WRISTS

8. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
NAVIGATION PROBLEM
I

XI
ZI
C
C
e
A
B
es
Navigation Problem: Move the
endoscope from A to B an
altitude angle .
I0
I0 Initial fulcrum (desired)
I Actual fulcrum
C Estimated fulcrum
e External distance error
es Separation error
II. Laparoscopic Navigation on Active Wrists

9. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
ERROR ANALYSIS
Separation Error: When estimated
fulcrum C differs from real location I0,
external distance error e forces a
fulcrum displacement es over the
abdomen, which can be
geometrically analyzed.
0 10 20 30 40 50 60 70 80 90
5
10
15
20
25
30
35
40
45
50
Altitude  (degrees)
SeparationErrores
(mm)
es
= e'
tan
50
25
10
e'

= 5 tanees 
II. Laparoscopic Navigation on Active Wrists

10. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
III. FORCE INTERACTION MODEL

11. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
ENDOSCOPE-ABDOMEN INTERACTION MODEL
XI
ZI
Fr
III. Force Interaction Model
rs FFgF  m
 A
Cmg
I0
Fs
I
B

12. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
FORCES MODEL
Stiffness Coefficient
0 0.5 1 1.5
-3
-2
-1
0
1
2
3
4
Time (seconds)
Elasticity(N/mm)
Real 
Estimated 
-20
0
20
0
0.5
1
1.5
2
0
2
4
6
8
10
Altitude  (degrees)Time (seconds)
FrictionFr
(Newton)
ss eF  NFr 
III. Force Interaction Model
Friction Coefficient

13. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
IV. CONTROL STRATEGY

14. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
NAVIGATION STRATEGY
1. Rotate around estimated fulcrum
Fulcrum displacement over the abdomen
2. Passive Wrist Behavior
Endoscope rotation over the wrist to reduce
fulcrum displacement
3. Altitude angle correction
Recover desired altitude angle
I
L1
L3
XI
ZI
C
IV. Control Strategy

15. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
PASSIVE WRIST BEHAVIOR (I)
IV. Control Strategy
Planner Robot
Abdomen
Interaction
Force
Sensor
Separation
estimator
External Distance
estimator
K
Friction + Weight
Filtering
CorrectionAngle
Planned Movement
Followed Altitude 
Abdomen
Force Fs Force F
Planned
Altitude p

16. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
PASSIVE WRIST BEHAVIOR (II)
IV. Control Strategy
 Planner
– Calculates the required trajectory with a first order system behavior
– Acts faster than correction angle loop
Robot: Performs the controlled movement
Endoscope-Abdomen Interaction: Generates abdominal forces
Force Sensor: Measurement of forces
Separation Estimator
– Depends on the stiffness estimation
– Its value remains the same if Fs < Fthreshold
External Distance Estimator
– Result of Force-Torque balance
– Its value remains the same if Fs < Fthreshold
r
T
s
T
s LekLekL )1()()1(  

e
s
s
F
e


Ce  


sρ
s
Fu
M

17. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
SPHERICAL CONTROL LOOP
IV. Control Strategy
Passive Wrist
Behavior Robot
Followed Altitude 
Control PI
+
-
Desired
Altitude d
Planned
Altitude p
Controlled
Altitude c

18. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
V. IMPLANTATION AND EXPERIMENTS

19. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
IMPLANTATION (I)
V. Implantation and Experiments
Movement
Command
Virtual-PA10
simulator (Matlab)
Matlab-C++
DLL Library
linker
C++ Library PA-10 Controller
PA-10 Robot

20. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
IMPLANTATION (II)
V. Implantation and Experiments

21. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
EXPERIMENTAL RESULTS
0 2 4 6 8 10
0
0.5
1
1.5
2
2.5
3
3.5
Time (seconds)
SeparationErroreS
(mm)
V. Implantation and Experiments
0 2 4 6 8 10
266
268
270
272
274
276
278
Time (seconds)
ExternalDistancee
(mm)
Estimated
Real
0 1 2 3 4 5 6
-49
-48
-47
-46
-45
-44
-43
-42
-41
-40
Time (seconds)
Altitude(degrees)
 Desired
 Followed

22. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
VI. CONCLUSIONS AND FUTURE WORKS

23. SystemEngineeringand
AutomationDepartment
Enrique Bauzano Nuñez
ebauzano@uma.es
Active Wrists Endoscope Navigation in Robotized Laparoscopic Surgery
FUTURE WORKS
Active tasks during an intervention
Development of semi-autonomous robotic
surgeon assistants
Like remote-centered wrists, useful on tele-
surgery fields
CURRENT STATUS
System does not depend on friction force
Stiffness can be now measured on-line, not model needed