1. Assessment of Applications of Force Sensing Materials in Robotics
Southeastern Louisiana University

2. Andrew Allemond Mechanical Engineering Technology Blake Dufour Mechanical Engineering Technology
ET-493_01
Senior Design I
Instructors: Dr. Cris Koutsougeras / Dr. Junkun Ma
Advisor: Dr. Mohammad Saadeh
Spring 2016

3. Background Previous Technology Sensor Force Sensing Resistor
Provides a range of data about the measurement, such as the magnitude of a force value relative to a known measurement.
Material whose resistance changes when a force or pressure is applied
Nonlinear
Accuracy issues
Background
Previous Technology

4. Purpose CHOOSING THE BEST FIT TECHNOLOGY FOR SENSING DYNAMIC FORCES
Research and Analyze:
Piezoelectric Sensors
Piezoresistive Sensors
Piezocapacitive Sensors
MEMS Capacitive Sensors
Perform Data Acquisition
Purpose

5. Alternative Sensing Technology
Piezoelectric Effect
The ability of certain materials to generate an electric charge in response to applied mechanical pressure or force.
The Piezoelectric Effect is linear.
The amount of charge generated is proportional to the amount of stress placed upon the Piezo material.
Alternative Sensing Technology

6. Sensor Technology Research Results
Piezoelectric/resistive
Pros:
Simple wiring and Programming
Very precise sensibility
Return quickly to original state
Low price
Cons:
Charge leakage
Brittle material
Capacitive Sensor
Pros:
Simple wiring
Reliable sensibility
Fast sensing ability
Can sense continuous loads
Cons:
Charge Leakage
Complicated Programming
More expensive
Sensor Technology Research Results

7. Alternative Sensing Technology
Capacitive Flexible Sensor
(Planned / Removed)
FDT Series Piezo Film
(Added)
Rectangle elements of piezo film with silver ink screen printed electrodes.
Mesh / Screen of capacitive sensors placed on top of a deformable flexible substrate
Similar to Touchscreen on Phones
Uses a dedicated capacitance-to-voltage acquisition engine to implement the touch sensing
Alternative Sensing Technology

8. FDT Series Sensor Technology Results
FDT Sensor
Pros:
Flexible leads
Very accurate as a strain gauge
Cons:
Strain induces voltage
Large
Expensive
Features:
Thin piezo film sensor
Flexible leads give flat profile to the sensor
Dynamic strain sensing with a high output
Typical interface to a 1 or 10 MΩ input impedance
Output Voltage dependent on Force applied 10 mV to 100V
FDT Series Sensor Technology Results

9. Methodology I---Choose the best sensor candidates for our needs
II---Code Arduino to Read Sensors Output
III---Apply Mechanical Load / Force on Material
IV---Perform Data acquisition and Analysis
V---Compare sensors to make a final choice
Methodology

10. Materials Acquired Piezo Ceramic Discs FDT Piezo Film Sensors
3 types - photos on left
FDT Piezo Film Sensors
FLDT1-028K
FLDT1-052K
Soldering Kit
2% Silver Lead-Free Solder
Liquid Flux
Arduino Uno Microcontroller
Operational Amplifiers
Capacitive
Diaphragm
Ceramic
FDT Series
Materials Acquired

11. A simple program we wrote to read the analog voltage input by the sensor and display it in real time for testing purposes
This voltage displayed can easily be converted to force.
Sampling Program

12. Sampling Sensors Wheatstone Bridge
Uses ratio of 3 known resistors to find a 4th resistance.
When a voltage is applied to the circuit and the voltage at the bridge=0, the ratio below can be used.
By changing resistors and adjusting a variable resistor, we can tare the circuit allowing more precise sampling
Sampling Sensors

13. Sampling Sensors cont…
Piezoresistive Sensor
The piezoresistive sensor reading in the wheatstone bridge circuit is shown left.
The sensor only spiked when a force was applied.
We need to read dynamic force so we decided to move on to piezoelectric.
Piezoresistive Sensor Sampling #1
Sampling Sensors cont…

14. Sampling Sensors Cont…
Piezoelectric Sensor
This sensor’s output is obviously very volatile and noisy.
The voltage output was also too low to capture with precision.
To fix this problem we decided an operational amplifier should be used.
Piezoelectric Sensor Sample #1
Sampling Sensors Cont…

15. Sampling Sensors Cont…
Circuits with Op Amp
After trying multiple amplifiers, we found that the TL032CP worked best. With a max voltage near 5V, it gave fairly stable readings of the + and – voltage from the sensor. Applying forces from 0N-20N then releasing and recording data in excel gave the graph left.
Piezoelectric sensor with Op Amp
Sampling Sensors Cont…

16. Data Processing Processing: Open source programming
can create images, animations, and interactions from Arduino.
Enables viewing the data from each sensor in real-time.
Multitude of tutorials on processing the data are available.
Data Processing

17. Status Of Deliverables
Task:
Dates:
Progress:
Research Piezo Electric and MEMS Sensors
2/10/2016
Completed
Research Method For Sampling Multiple Sensors
2/17/2016 
Research Data Acquisition Method
Order Materials For Testing Purposes
3/4/2016
In Progress
Research Piezo Electric Equations
3/4/2015
Code Microcontroller For Sampling Sensors
3/12/2016
Receiving Materials
3/21/2016
Sample Sensors For Quality Assurance
3/28/2016 
Perform Data Analysis of Sensors
4/7/2016
Create Graphical Display of Sensor Data Analysis
4/17/2016
Research Live-Feed Software For Graphical Display
4/21/2016
Code Software For Live-Feed Display
TBD
Status Of Deliverables
(Dates and Tasks Are Subject To Change)

19. Analog/Digital MUX Breakout. (2010)
Analog/Digital MUX Breakout. (2010). Retrieved February 16, 2016, from SparkFun Electronics:
FingerTipMulti-Touch Screen Controller with Ultra-Low Power. (n.d.). Retrieved March 02, 2016, from
Operational Amplifier Basics - Op-amp tutorial. (2013). Retrieved February 27, 2016, from
Mancini, R. (2002, August). Op Amps For Everyone. Retrieved January 20, 2016, from Texas
Instruments:
Piezo Systems, I. (2008). Introduction of Piezo Transducers. Retrieved January 9, 2016, from Piezo.com:
Stutz, M. (2001). Multiplexers. Retrieved February 16, 2016, from
References