multiple force platform

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Presentation Description

Force platform is a platform used to quantify the ground reaction forces exerted on it. It is widely for gait analysis, rehabilitation, anomalies detection. Each platform has a dimension of 480mm x 540mm x 15mm and consists of 144 force sensitive resistor (FSR). These two force platforms can be combined into one to provide a larger movement area for test subjects.

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Presentation Transcript

“Multiple Force Platform Using Ethernet DAQ Device” :

“Multiple Force Platform Using Ethernet DAQ Device” Introduction Objectives Force Platform Switching Circuit Data Acquisition Future Improvement Conclusion Q & A

Introduction:

Introduction The project is based on a device used to analyze the movement pattern of a test subject and jumping performances of an athlete. Analysis of human movement/gait will help improve current understanding in sports and medicine. (orthopedics, prosthetics) This will be accomplished by means of two Force Platforms each consisting of force sensor arrays

Objectives:

Objectives Construct force platforms to evaluate movement and jumping performance of athletes. Integrate the two platforms to function as one Improve current hardware design Develop DAQ system to integrate the LabJack device and the Force Platform Increase Force Platform accuracy Increase the portability of device

Analysis of Previous Designs:

Analysis of Previous Designs Need to identify the deficiencies in the preceding designs Implement improvements to overcome deficiencies

Previous Designs:

Previous Designs Design 1 (1 st Generation)

Slide 7:

Previous Designs Design 2 (2 nd Generation)

Drawbacks From Previous Designs:

Drawbacks From Previous Designs Base material Yoga Mat Soft Does not imitate Real-life flooring Wooden Board Harder than Yoga mat Fragile

Drawbacks From Previous Designs:

Drawbacks From Previous Designs Use of wires to connect sensors Harder to troubleshoot Unnecessary Complications Bulky Board

Drawbacks From Previous Designs:

Drawbacks From Previous Designs Circuit Design 1 st Generation Used Breadboards and wires Harder to troubleshoot Higher Error Ratio

Drawbacks From Previous Designs:

Drawbacks From Previous Designs Circuit Design 2 nd Generation Extensive use of jumper wires Complications in building the circuit

Force Platform :

Force Platform The platform is designed to house the force sensors To withstand the jumping force of an average person To enable the easy replacement of damaged sensors Be aesthetically pleasing and potentially marketable

Force Platform :

Force Platform Layers in the platform design: Acrylic layers Top layer Second layer Bottom layer Tracks layer Padding layer

Force Platform :

Force Platform Acrylic layers-Top Layer Total dimensions 480 x540 mm 144 x 20mm diameter holes 53 x M4 counter sunk screw holes FSR sensor used Light flexible

Force Platform :

Force Platform Acrylic layers-Second Layer Position where the force sensor “legs “ will connect to the Copper Board below. Placement of force sensors on the second layer Different placement of sensors enable seamless integration of multiple boards

Force Platform :

Force Platform Acrylic layers-Bottom Layer M4 screw holes Purpose to cover the bottom part of the platform and enclose it. Nuts will be fastened to the M4 bolts to secure the board in place

Force Platform :

Force Platform Tracks layer (copper board) +5V connection for sensors Individual signal connection from each sensor Connection to the 40 way cable Cable connected to 40 way male connector Sensor “legs” attached to SIL connectors on reverse side

Force Platform :

Force Platform Padding Layer Yellow sponge layer added to absorb applied force Padding also protects circuitry

Force Platform:

Force Platform Completed Board Complete dimension: 480mm x 540mm x 15mm

Switching Circuit:

Switching Circuit Output Resistance from sensors need to be converted to Voltages before it can be sampled. LabJack device unable to sample 288 outputs simultaneously. Therefore multiplexing is necessary

Slide 21:

Switching Circuit Contains Voltage Divider LM324 Opamp 10K Resistor Multiplexing CD4051 8 channel multiplexer Switching Circuit

Switching Circuit:

PCB Drawing for 1 Quadrant Output +5V ABC Circuit 2 Circuit 1 - 5V Multiplexer OPAMP 10 Way Connector Resistor 40 Way Sub Circuit Switching Circuit Multiplexer

Switching Circuit:

Full Platform 4 Quadrants 144 sensors 4 Outputs to the Labjack 2 BOARDS 8 Outputs to the Labjack Switching Circuit

Switching Circuit:

Finished Circuit 1 Quadrant 4 boards for 1 platform Switching Circuit

Data Acquisition & Processing:

Data Acquisition & Processing To acquire data from the Force Platform To transmit acquired data reliably To process acquired data to usable information To display information in a GUI

Introduction to LabVIEW :

Introduction to LabVIEW LabVIEW is a graphical language that uses icons instead of lines of text to create applications Build a user interface by using a set of tool and objects LabVIEW programs are called virtual instruments, or VI.

Program Algorithm:

Program Algorithm Start Replay Simulation End Prompt User for input parameters Scanning and Force Conversion Display Force Information Compute Specific Activity Parameters

Force Conversion:

Force Conversion Voltage value Voltage > 0.88? Force = 0 Force = 0.9907V – 0.4836 No Yes Save into an Array

Slide 29:

Run Simulation Front Panel

Slide 30:

Replay Simulation Front Panel

Future Improvement :

Future Improvement Adapt FPGA for switching purposes Multiple layer PCB design Reduce components size

Future Improvement :

Future Improvement Use Wi-Fi instead of Ethernet connection DAQ device with higher sampling rate

Conclusion:

Conclusion Two force platforms were fabricated and tested. They are significantly improved in terms of aesthetics. Device portability is increased with the use of smaller control boxes. The two platforms can be seamlessly combined into one.

Questions and Answers:

Questions and Answers

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