Sensory Interfaces for an Intelligent

Surgical Box Trainer

Joshua ClemensSarah SengKrystal York

Western Michigan University

Contents1. Background

2. Need Statement

3. Box Trainer and Set-Up

4. Specifications

5. Hardware

Discovery Board

Force Sensor

Grasper Tools

Accelerometer

Push Button

Non-Conductive Enclosure

Schematics

6. Calibrations

7. Software

8. Testing Procedure

9. Testing Performance

10. Results

11. Recommendations

12. Questions

Background• Fundamentals of Laparoscopic Surgery (FLS)

program was created to educate and test surgical residents and practicing surgeons

• Students must perform a physical test using an intelligent surgical box trainer

• Laparoscopic surgery is a form of minimally invasive surgery with a variety of benefits:o Smaller scarso Shorter recovery timeo Shorter hospital stays for patients

https://assets.limbsandthings.com/products/fls_simcart_and_

trainer_720x720_72_RGB.jpg

Need StatementVarious sensory interfaces need to be

implemented to improve the FLS

(Fundamentals of Laparoscopic Surgery)

Trainer System. Sensors are needed to

measure the applied force of the grasper tool,

measure wrist orientation, and measure the

time it takes for the test to be completed. This

information needs to interface with a

microcontroller to upload the data to a

computer. This will supply performance

feedback to surgical students so they can

further improve their laparoscopic surgery

skills.

Box Trainer and Set-Up• Different laparoscopic tasks performed using box trainer:

o Peg transfer

o Precision cutting

o Ligating loop

o Suture with extracorporeal knot

o Suture with intracorporeal knot

https://www.youtube.com/watch?v=H5DZst68mMc&t=2s

SpecificationsSpecification R, G, or P

Sensor able to accurately measure pressure from 0.1 to 4 PSI R

Sensor able to accurately measure a radial orientation range of 210º R

Sensor able to mark the beginning and ending of an FLS Trainer test R

All sensors must weigh less than 1 oz R

Discernable analog or digital signals from sensors to microcontroller R

Microcontroller system

STM32F4 Discovery Board

R

P

5 VDC power source R

Key:

R: RequirementG: GoalP: Preference

Specifications

C programming R

Serial connection required from microcontroller to PC R

Data stored in accessible format

Excel file

R

P

The microcontroller and other auxiliary electronics should be contained in a

nonconductive enclosure

R

The enclosure should be mounted on the FLS Trainer cart R

The enclosure should weigh less than 1 lb G

Components should ideally require 3.3 VDC or 5 VDC power G

Specification R, G, or P

Hardware

M ichelle Valent e

Discovery Board• STM32F407VG Discovery Board

microcontroller• ARM Cortex-M4 processor• ST-Link: embedded debugger & programmer

o Sensor data tracking and storage

• 14 timers, 40 channelso Tracking test duration

• 3 analog to digital converters (ADC), 15 channels eacho Accelerometer signals

• 3 I2C Interfaceso Force sensor signals

• Sensors hardwired to GPIO pins using multi-

conductor 24 AWG signal cable

Force Sensor & Interface Board• SingleTact tactile capacitive force sensor• Measures up to 22 pounds of force

across an 8 mm surface• Sensor applied to the handle of each

grasper tool• Generates an analog signal between 0

and 2 V in response to force and accepts supply voltages between 3.7 and 12 Vo This analog signal will run to I2C interface

board

http://www.robotshop.com/media/f iles/pdf/SingleTact_Manual.pdf

• Interface boardo Supplies power to the sensoro Reads analog signalo Converts sensor analog output to a 10-

bit digital valueo Stores digital value to internal memory

• I2C compatible serial interface• 140 Hz refresh rate

SingleTact CapacitiveForce Sensor

Single TactInterface Board

Grasper Tools• Capacitive force sensors attached to handles of grasper tools

• The force applied at the handle is used calculate the applied force on tissue at the end of the tool

o Force must be measured on handle so it does not interfere with smaller grasper end

https://www.fls-products.com/products/maryland-dissector-fls-approved

Measure

force here

To find force

applied here

Accelerometer• Acceleration measured in three

directions is used to calculate position

of sensor

• Attached to band on user’s wrist to

minimize interference with test taking

• Three independent, non-proportional

analog outputs for x-, y-, and z-

acceleration

https://cdn.sparkfun.com//assets/parts/2/7/6/8/09269-01.jpg

https://www.dfrobot.com/wiki/index.php/How_to_Use_a_Three-

Axis_Accelerometer_for_Tilt_Sensing

Push Button• Start switch sends signal to

initialize the collection of data

• Push button operates timer input

to track test duration

• Needs to be pushed by user

inside the box with the grasper

tool

○ Printed using 3D printer in ECE Senior

Design Lab

http://www.ckswitches.com/media/1269/pts645.png

Non-Conductive Enclosure• Modeled in AutoCAD

o Capable of designing an enclosure that met our

specific needs

i. Big enough to hold the microcontroller and

circuit board

ii. Small enough to fit comfortably inside the

box trainer

iii. House all electronics except external sensors

• 3D printer used to print out design

o Printer available in ECE Senior Design Lab

o ABS and PLA plastics both used to make

enclosure

i. Typical plastics used with 3D printing

ii. Both are non-conductive

Schematic

Software• Timer and Push Button

o Timer 5: 32-bit timer

o Triggers every millisecond

o Translates timer counter iterations to a

clock format (minutes: seconds:

milliseconds)

• Accelerometer

o Three ADC modules

o Conversions stored in array for averaging

o Averager output normalized

o Normalized magnitudes converted to

• Force Sensor

o Both force sensors on the same I2C bus

o Bus consists of two lines (clock and data)

o The Discovery Board communicates by

toggling the data pin in sync with the clock

o Each force sensor is assigned a different 7-bit

address

o Discovery Board can instruct force sensors to

output memory contents on the data line of

the I2C bus

• Communication with the PC

o STMStudio

Software Block Diagram

Calibration & Verification• Push Button

o Internal clocks with specified

frequencies

o Verified with stopwatch

• Force Sensor

o Pre-calibrated interface board that

matches with their sensor

o Verified with digital scale

• Accelerometer

o X, Y, and Z signals were conditioned to

proportional to one another

o Reconfigurable upon system startup

o Verified with protractor

Testing Procedure1. Put on wristband

2. Flip power switch to “On” position (LED on switch will light up)

3. Hold wrist in base position shown in figure to the right

4. Press button labeled “X” to calibrate x-axis base positions

5. Press button labeled “Y” to calibrate y-axis base positions

6. Press button labeled “Z” to calibrate z-azis base positions

7. Grab both grasper tools

8. Press the start/stop button on top of the

enclosure (green LED will light up when timer begins)

9. Perform necessary tasks

10.Press the start/stop button on top of the

enclosure (green LED will turn off when the timer ends)

Test Performance Video

Test Performance Video

Specification ResultsSpecification R, G, or P Completed

Sensor able to accurately measure pressure from 0.1

to 4 PSI R✔

Sensor able to accurately measure a radial orientation

range of 210º R ✔

Sensor able to mark the beginning and ending of an

FLS Trainer test R ✔

All sensors must weigh less than 1 ozR ✔

Discernable analog or digital signals from sensors to

microcontroller R ✔

Microcontroller system

STM32F4 Discovery Board

R

P

✔

✔

5 VDC power sourceR ✔

Key:

R: RequirementG: GoalP: Preference

Specification ResultsC programming R ✔Serial connection required from microcontroller to

PC R ✔Data stored in accessible format

Excel fileR

P

✔✔

The microcontroller and other auxiliary electronics

should be contained in a nonconductive enclosure R ✔The enclosure should be mounted on the FLS Trainer

cart R ✔The enclosure should weigh less than 1 lb G ✔Components should ideally require 3.3 VDC or 5

VDC power G ✔

All specifications attempted and completed. Project is 100% complete.

Specification R, G, or P Completed

Results• Successfully programmed microcontroller to gather and coordinate

sensor interfaces

• Successfully implemented capacitive force sensor and interface board in

accurately measuring force on grasper tool

• Successfully converted accelerometer data to wrist orientation

information

• Used STMStudio to read and record sensor interface information

o Modified original plan for UART communication with local PC

Bill of MaterialsItem Quantity Part Number Cost

Accelerometer 3 ADXL335 $44.85

Force Sensor 2 S8-100N $149.90

Discovery Board

Microcontroller1 STM32F407VG $19.90

8 Pin Male DIN

Connectors3 CP-1080-ND $4.20

8 Pin Female DIN

Connector3 CP-3180-ND $4.11

O Ring Kit 1 $8.00

Push Buttons 100 PTS645 $10.41

Total $241.37

Recommendations• Several improvements can be made to improve performance and

usefulness:

o Use both an accelerometer & gyroscope, or inclinometer

to accurately monitor wrist orientation

o Have accelerometer and force sensor wirelessly

communicate with microcontroller

o Develop a more intuitive user interface for

computer set up

o Implement a self-test and calibration board to

make setup easier and faster

o Determine a more robust relationship between

force applied at handle and at grasper

Thank You

WMU ECE Department

Dr. Janos Grantner

Aous Hammad Kurdi

Mohammed Yasser O Muhieldeen Al Gailani

Bob Makin

Questions?