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

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

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

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

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

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

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

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

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

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

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

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

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…

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…

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…

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

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)

Analog/Digital MUX Breakout. (2010) Analog/Digital MUX Breakout. (2010). Retrieved February 16, 2016, from SparkFun Electronics: http://www.sparkfun.com/commerce/product_info.php?products_id=9056   FingerTipMulti-Touch Screen Controller with Ultra-Low Power. (n.d.). Retrieved March 02, 2016, from http://www.st.com/web/catalog/sense_power/FM89/SC1717/SS990/PF251157 Operational Amplifier Basics - Op-amp tutorial. (2013). Retrieved February 27, 2016, from http://www.electronics-tutorials.ws/opamp/opamp_1.html Mancini, R. (2002, August). Op Amps For Everyone. Retrieved January 20, 2016, from Texas Instruments: http://focus.ti.com/lit/an/slod006b/slod006b.pdf Piezo Systems, I. (2008). Introduction of Piezo Transducers. Retrieved January 9, 2016, from Piezo.com: http://www.piezo.com/catalog7C.pdf%20files/Cat7C.20,21,22,23,60,61&62.pdf Stutz, M. (2001). Multiplexers. Retrieved February 16, 2016, from http://www.allaboutcircuits.com/textbook/digital/chpt-9/multiplexers/ References