P19095: LiveAbility Lab
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Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

During the subsystem build and test phase the team planned on assembling each individual subsystem of our design. Following assembly, the plan was for each subsystem to be evaluated. The evaluation would allow the PCB to be ordered. In reality we were able to get each subsystem: location sensing, force sensing, power management, and data calculation working. The next steps are polishing the data we collect (coordinate vs distance and force vs voltage), integrating into one package, and testing.

Updated Customer Requirements

Updated Customer Requirements

Updated Customer Requirements

Design and Build Progress

PCB

PCB Layout

PCB Layout

Link to other PCB pictures.

Packaging

The packaging was created using Creo Parametric CAD software and 3D printed using ABS plastic at the RIT Construct. The electrical components that will be housed in this packaging are the raspberry pi and juicebox (grey), DWM module (green), accelerometer (red), battery (pink), and PCB (not pictured - will sit on top of DWM). Spacers are used to attach electrical components to the packaging and to each other.
Packaging Design

Packaging Design

Test Results Summary

Force Sensor Calibration

The Tekscan A301 force sensor included a guide on how to calibrate and integrate the sensor into an OEM. The guide was followed but some adjustments were needed. First, the circuit seen below was built on a breadboard.

A301 Circuit Schematic

A301 Circuit Schematic

The OP-AMP chip used has four OP-AMPs which share a VDD and VSS.
MCP6004 Pinout

MCP6004 Pinout

The circuit with variable resistors was brought to the mechanical engineering material science lab. The voltage divider was kept constant with R1 = 270 and R2 = 1000. The force sensor was placed under a controlled force which was varied along with the feedback resistor. For each combination, the output voltage is recorded.
Force sensor calibration

Force sensor calibration

The output plot with the most linear plot is selected. The feedback resistor value of that plot is chosen as that for the circuit. This limits clipping/clamping OP-AMP effects as well as sensitivity issues. The chosen value was 200kohms.
Feedback Resistor Selection

Feedback Resistor Selection

Using the equation from the linear fit, the voltage can be converted to a force.
Voltage to Force conversion

Voltage to Force conversion

Force Sensor Calibration

Decawave Data Gathering

Decawave Data Gathering

Above is the data that the pi receives via UART from the decawave. The tag communicates with all of the anchors and returns the distance from each unit.
Location Calculation Method

Location Calculation Method

We are currently finalizing the location code that will return the XYZ location instead of just the distances. However, this triangulation method is the idea that we are trying to replicate. Notice, the four different points and circles. This is all the data that we have, and we need to use the intersections and centroids to find the most likely location of the tag.
Location Calculation Accuracy

Location Calculation Accuracy

This precise example shows the estimated best location via triangulation vs. the actual location. The error is around 4 inches when the tags are 25 ft. apart. This already meets the requirements and will most likely get better as we fine tune the functions.

Sensor Communication Overview

Software Architecture

Software Architecture

Risk and Problem Tracking

Risk Management Document

Risk Management Document

Link to our Risk Management Document.

Problem Tracker Document

Problem Tracker Document

Link to our Problem Tracking Document.

Plans for next phase

Individual Responsibilities to Achieve Team Goals

Martine Bosch
Nick Petreikis
Matthew Devic
John LeBrun
Hrishikesh Moholkar

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