Submitted To:
Dr. B.C. Chang
Dr. Wei Sun
Dr. Moshe Kam
Dr. Leonid Hrebien
Pramod Abichandani
Chirag Jagadish
Problem Background
Surgical Techniques
Open
Minimally Invasive (MIS)
Laparoscopic
Minimally Invasive Robotic Surgery (MIRS)
Traditional Laparoscopic
Instruments manipulated by hand through small incision
Endoscope used to view operating space
Laparoscopic limitations
“chopstick effect”
2D representation on monitor
Minimally Invasive Robotic Surgery
(MIRS)
Robotic systems were developed to overcome the
awkward hand
-
eye coordination involved in laparoscopic
procedures [1]
Intuitive Surgical’s
daVinci®
system is most popular for
minimally invasive robotic surgery (MIRS)
Approved by the FDA in July of 2000 [2]
860 units sold and more than 70,000 surgeries performed
each year [3, 4]
The
da Vinci
Surgical System
[5]
[6]
Strengths and Drawbacks
of MIRS
MIRS strengths
Geometric accuracy
Free from tremors and fatigue
Sterile
Resistant to infection
MIRS drawbacks
Current systems lack realistic, continuous force feedback [7]
Training is expensive and time consuming
Inexperienced surgeons take longer using MIRS than
conventional methods
MIRS Statistics
Taken from “Clinical Efficacy
-
Comparison of Open
Prostatectomy, Laparoscopic and da Vinci Prostatectomy” [8]
Open
Laparoscopic
da Vinci
MIRS
Patients
100
50
100
Operative Time (Min.)
164
248
140
Blood Loss (mL)
900
380
<100
Cancer Remaining
24%
24%
5%
Complications
15%
10%
5%
Catheter, Days
15
8
7
Hospitalization (Days)
3.5
1.3
1.2
Problem Statement
Current minimally invasive robotic surgical systems lack realistic
force feedback
Tactile sense is one of the most important tools for surgeons
Surgeons rely on tactile sense in order to characterize tissue and
make intra
-
operative decisions [9].
Surgeons must rely on visual cues only, which requires
significant experience [1].
Lack of realistic force feedback can lead to tissue damage or
other mistakes
Without force feedback in blunt dissection, the number of errors
resulting in tissue damage increased by over a factor of 3 [10]
Increased operating time and cost
Force Feedback
Preliminary research shows that force feedback improves
on the gains made by MIRS over conventional techniques
Possible to tie tighter, more consistent sutures [7]
Improves arterial dissection by reducing unintentional
transections [12]
Reduces learning curve for surgeons with little or no
experience using MIRS [13]
Design Objective
Prototypic slave
-
master surgical robotic system
Sense force at the slave (surgical manipulator)
Generate force at the master (user controls)
Microprocessor communication between master
controller and slave gripper allows us to:
Control gripper angle
Reproduce gripper forces at the surgeon user control
Translate the
EndoWrist
in two axes
Method of Solution
System Components
Two electromechanical systems in a slave
-
master
configuration
Master includes custom user controls, force feedback
actuator, and microprocessor
Slave includes
EndoWrist®
, x
-
y stage, and microprocessor
Host computer to display important information and set
system parameters
The
EndoWrist
Precision surgical manipulator
developed by Intuitive Surgical for the
da Vinci
Surgical System
Offers 7 degrees
-
of
-
freedom
Complex movements made possible
using four control knobs
EndoWrist
Control Knobs
Slave Interface to
EndoWrist
Three components:
Base includes four holes into which DC motors can be
mounted
Cylindrical adapter can be used to attach a motor shaft to an
EndoWrist
control knob or to hold control knob in place
Clamp used to attach the base to the
EndoWrist
Modular
–
Additional motors can be added if needed
Base of Slave Interface
Top View
Bottom View
Adapter for Slave Interface
Top View
Bottom View
Force Sensing
Motors will be controlled using PWM controlled H
-
bridge
circuits
To sense force, a current sensor will be placed in series
with the
EndoWrist
’s drive motor
Does not require any physical modifications to the
EndoWrist
x
-
y Stage
The
EndoWrist
and the mechanical interface assembly will
be mounted on an x
-
y stage
The stage will be positioned vertically to allow to allow the
user to grip, lift, and pull a sample placed beneath the
EndoWrist
Slave Processor
The slave processor will:
Execute control algorithms for the
EndoWrist
and the x
-
y
stage
Collect and transmit force measurements to the master
processor
A second, less powerful processor (the “stage controller”)
will drive the motors for the x
-
y stage
Master Grip Controller
Two gripper levers onto
which plastic finger
splints will be placed
Levers will rotate the
shaft of a DC motor
Optical encoder will
measure shaft position
Drive motor to provide
force feedback
Translation Controller
Used to control the movement of the x
-
y stage
Will be integrated with the grip controller
Possible options:
Joystick controller
Translation sensor (e.g. optical mouse sensor)
Master Processor
The master processor will:
Receive force measurements from the slave processor
Transmit position data to the slave processor
Execute a position
-
force control algorithm to create a
realistic sense of touch
Transmit data to the host computer via USB
Host Computer
Connected to the master processor via USB
A graphical user interface (GUI) will display information
about system operation to the user
May include real time graphs of force and position
GUI will also be used to set system parameters (e.g.
scaling ratios)
Deliverables
The design should meet the following criteria:
The user will command grip and 2D translational motion of
the
EndoWrist
The user will be able to sense an object in the grasp of the
EndoWrist
Alternative Solutions
Alternative Solutions
Two key components to any force feedback solution
Instrumentation Design
-
Placement of sensors
Sensing Method
-
Measure force
The key components are interdependent
–
certain methods of
sensing force require specific placements for sensors
Based on the selection of the key components, it’s possible to
choose a control algorithm
Two common force feedback control algorithms are:
Force
-
Position
Position
-
Error
Alternative Solutions (Cont’d)
For force feedback, the force sensing elements placed at
the slave, on the laparoscopic instrument
Laparoscopic instrument is inserted into the body through
an insertion which is 3
-
12mm in diameter
Particular sensors may have limitations on feasible
locations
Placement of Sensors
1.
At the joint actuation unit
2.
Shaft portion outside abdominal wall
3.
Shaft portion inside abdominal wall
4.
End effector's articulated joints
[14]
Methods of Sensing Force
1.
Displacement
2.
Current
3.
Pressure
4.
Resistive
5.
Capacitive
6.
Piezoelectric
7.
Vibration
8.
Optical
Sensor and Placement Selections
Current
-
based sensing
Exploits the relationship between shaft torque and armature
current, which is linear in the region of interest
Placed at the joint actuation unit
Four motor driver knobs to control gripper orientation and
actuation
Advantages of Selections
Minimizes redesign of
da Vinci
Allows the
EndoWrist
to be used without redesign
Known to be comparatively simple approach
Calibration and experimentation can be used in lieu of
system modeling to determine erroneous forces
No need for sterilizability and biocompatibility
Lower recurring cost to end user than internally placed
sensor
-
no need to be cleaned or replaced after each
operation
Disadvantages of Selections
Measurements may be inaccurate due to approximations
which are based on torque
-
current curve
Force signal may have magnitude and phase distortions
Mechanical linkages introduce error due to:
Friction
Backlash
Inertia
Mechanical moments
Final Analysis of Key
Component Selections
Inexpensive
Low complexity
Adaptable to existing robotic surgery systems
Alternative methods may require redesign of the
laparoscopic instrument
Feasible using available senior design resources
Design Constraints
Cost and time
Limited funding
Must be completed within next two terms
Complexity limited by funding and duration
FDA regulations specify that the slave surgical
manipulator must be biocompatible and sterilizable [15]
Constraint is met by placing sensors outside the body
Design Constraints (Cont’d)
Geometry
Ability of instrument to be
inserted through trocar
Induced Master Motion
Stability is compromised by
allowing force feedback
signal to influence position
Gains are limited to values
that ensure system stability
Trocar
Skin
[1]
Project Management
Gantt Chart
Task Tree
Industry Budget
a.
Includes cost of H
-
bridge, current sensor, and quadrature decoder
b.
Includes cost of Pro
-
E and SolidWorks
c.
Cost of Labor:4 junior engineers, $55K salary, 15 hrs/week, 36 weeks
d
. Overhead: 50% of total Cost of Labor
Economic Analysis
Dr. B.C. Chang provided
EndoWrist
and 2 DC motors with
encoders for free
Manufacturing provided at Olympic Tool’s expense
Freescale Semiconductor provided 2 microcontroller
development boards for free by sponsorship agreement
Engineering software available
Not considering labor and overhead costs
Out
-
of
-
Pocket Costs
Description
Cost
Quantity
Total Cost
Translation (x
-
y) Stage
$1,274.00
1
$1,274.00
Digital Motor Controller
Board
$400.00
2
$800.00
Total
$2,074.00
Societal and Environmental Impact
Implementation of force feedback will allow more delicate surgeries
For example, Mitral Valve Repair (MVR) is significantly less dangerous
when MIRS is used [16]
2001 STS Nat’l Database
Sternotomy MVR
da Vinci
Trial
Patients
893
112
Mortality
2.2%
0%
Major Complications
12.1%
9.8%
Neurological Complications
2.4%
0%
Hospitalization (Days)
8.5
4.7
Societal and Environmental Impact
(Cont’d)
Improvements to MIRS should further reduce:
Complications
Supplemental surgeries to correct complications
Hospital stay times
Operation time
Cost of surgery may be decreased
Implementation of force feedback in surgical robotics
should have a minimal impact on the environment
Reduction in number of operations and operation time will
minimize the amount of electricity used in the operating
room
Conclusion
Statistics indicate that use of MIRS will continue to grow
Prototype of slave
-
master surgical robotic system with
grip force feedback
Current
-
based force sensing
Custom designed user controls,
EndoWrist
interface
Surgeon controls grip and 2D translation of
EndoWrist
Beneficial impact on the evolution of medical robotics
Questions?
References
[1] K. Seibold, U.and Bernhard and G. Hirzinger. Prototypic force feedback instrument for
minimally invasive robotic surgery. In V. Bozovic, editor, Medical Robotics, page 526. I
-
Tech
Education and Publishing, Vienna, Austria, 2008.
[2] M. Meadows. Robots lend a helping hand to surgeons. FDA Consum, 36(3):10
–
5, 2002.
[3]
www.intuitivesurgical.com/corporate/newsroom/mediakit/da_Vinci_Surgical_System_FAQ.p
df
[4] www.pacrimrobotics.com/forms/orangecounty_reg.pdf
[5] http://www.childrenshospital.org/clinicalservices/Site1860/Images/robotics(E).jpg
[6] http://www.healthaffairs.uci.edu/urology/prostate/daVinci.html
[7] http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1283126
[8] Menon M. Robotic radical retropubic prostatectomy. BJU Int. 2003 Feb;91(3):175
-
180.
[9] G. Tholey. A teleoperativehaptic feedback framework for computer
-
aided minimally
invasive surgery. PhD thesis, Drexel University, 2007.
References (Cont’d)
[10] C.R. Wagner, N. Stylopoulos, and R.D. Howe. The role of force feedback in surgery:
analysis of blunt dissection. In Haptic Interfaces for Virtual Environment and Teleoperator
Systems, 2002. HAPTICS 2002. Proceedings. 10th Symposium on, pages 68
-
74, 2002.
[11] http://www.ingentaconnect.com/content/klu/11548/2008/00000003/F0020003/00000228
[12] Deml, B. “Minimally Invasive Surgery: Empirical Comparison of Manual and Robot
Assisted Force Feedback Surgery” Proceedings of EuroHaptics 2004, Munich Germany, June
5
-
7, 2004.
[13] Reiley, C. “Effects of visual force feedback on robot
-
assisted surgical task performance”
The Journal of Thoracic and Cardiovascular Surgery, January 2008.
[14] P. Puangmali, K. Althoefer, L.D. Seneviratne, D. Murphy, and P. Dasgupta. State
-
of
-
the
-
Art in Force and Tactile Sensing for Minimally Invasive Surgery. Sensors Journal, IEEE,
8(4):371
–
381, 2008.
[15] Allison M. Okamura. Haptic feedback in robot
-
assisted minimally invasive surgery.
Submitted to Current Opinion in Urology, August 2008.
[16] http://www.sts.org/2003webcast/shows/tatooles/tatooles.html
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