DETAILED DESIGN REVIEW

GROUP MEMBERS:Irma BocovaRob Bowman

Phetphouvanh “Awt” PhommahaxayKyle Pilote

Jeff RebmannChris Rowles

Faculty Guide: Dr. Elizabeth DeBartolo

November 6th , 2009

Mechanical Spine Test Platform

P10007

Agenda

Desired Outcomes – 11:00am Project Background – 11:05am Mechanical Design – 11:15am

Drawings/Schematics Feasibility Calculations

Electrical Design – 11:35pm Selection Accelerometer issues MicroStrain 3DM sensor

Output Design – 11:55pm Bill of Materials – 12:10pm Risks/Feasibility – 12:20pm Preliminary Test Plan – 12:40pm Next Steps

Desired Outcomes of Review

Receive input on selected conceptIdentify and discuss key risks:

Sensor interference

Discuss LabVIEW

Mission Statement

The intent of this project is to design and build a test platform that will mimic the actions of a human spine. This design will incorporate movements in three dimensions, while being able to independently measure the angles and linear adjustments. The purpose of developing this platform is to validate the data from an existing measuring device in use at the Nazareth Physical Therapy Clinic.

Project Description

Project Title: Project Title: Mechanical Spine Test Platform

Primary CustomerPrimary Customer Dr. Sara Gombatto

Professor at Nazareth College of Physical Therapy Dr. JJ Mowder-Tinney

Director of Clinical Education Nazareth College Department of Physical Therapy

Physical therapy patients

Secondary OpportunitiesSecondary Opportunities Further spinal iterations

Background/Application

Nazareth Physical Therapy Clinic motion capture system Allows motion capture of

PT patients in order to track progress

Validation of existing motion captures

Focus on spinal segments

Secondary Application: Portable Motion Tracking

System calibration Source: Source: http://seneludens.utdallas.edu/images/mocap.jpg

Customer Needs

Three tiered approach to group needs and limit scope Base Plan Aggressive Outstanding

Example Need: Must be moveable in distinct segments Base Plan – Two distinct sections (Lower & Upper

Lumbar) Aggressive – Three distinct sections (Lower & Upper

Lumbar, Thoracic) Outstanding – Divide Thoracic segment into multiple

segmentsHighest Ranked Needs – Base Plan

Needs to be able to measure angle deviations for all sections relative to the section below it

Use a tight tolerance for measurements

Provide measurements in all three planes of space (x, y, z)

Needs distinct sections of the spine to be able to move

Needs to be adjustable lengthwise in order to simulate different size spines

Movements needs to be lockable so that an accurate measurement can be read

The height of the device has to be the level of a spine of a person standing in an upright position

Needs to have a “zero” position for all sensors/joints

Engineering Specifications

Correspond to highest ranked Customer Needs:

Specification UnitsBase Plan

ValueAggressive Value

Outstanding Value

Must have a minimum tilt in all directions relative to the section below

degrees +/- 15

Angle tolerance degree +/- 1.0

Must have a tilt in all directions relative to the section below

planes 3 (sagittal, transverse,

frontal)

Must be movable in distinct sections and a fixed base (pelvis)

movable sections

2 (lower lumbar, upper

lumbar)

3 (thoracic) Divided thoracic

Should be able to fit all required ranges needed by customer vertically

millimeters

30 - 150 for each lumbar

segment

200 – 300 for thoracic segment

Joint holding strength N*m 0.13

Device must mimic a person standing in an upright position - Trochanterior Height

millimeters

750 - 1000

Device has mechanical "zero" position Yes/No Yes Yes Yes

System Architecture

Final Concept

Final Assembly Picture-Isometric View

Final Assembly Picture-Front View

Final Assembly Picture-Side View

Mechanical Calculations

Mechanical Calculations(cont’d)

Electrical Selection

Analog Devices- Adxl202 accelerometerMicroStrain’s- 3DM

Microstrain 3DM

Magnetometers and accelerometers are used to compute pitch, roll, and yaw.

Output provides raw magnetic field and accelerometer outputs, or pitch, roll, and yaw outputs.

Communication through a serial port.

MicroStrain 3DM Sensor Specifications

Range

Yaw: 180˚

Pitch: 90˚

Roll: 180˚

A/D Resolution 12 bits

Digital FilterInfinite Impulse Response (IIR)

User programmable weighted moving average

Angle Resolution (no digital filtering)

Pitch: 0.30˚ (typical)

Roll: 0.25˚ (typical)

Yaw: 0.50˚ (typical)

Angle Resolution (most aggressive digital filtering)

Pitch: < 0.1˚

Roll: < 0.1˚

Yaw: < 0.1˚

Resolution specs. taken during static motions

Accuracy

Pitch: 0.93˚ typical (yaw from 0 - 360˚ and roll=0˚)

Roll: 0.33˚ typical (yaw from 0 - 360˚ and pitch =0˚)

Yaw: 1.0˚ typical (pitch and roll=0˚)

Accuracy is defined as the square root of the sum of the errors squared (non-repeatability, temperature coefficients and nonlinearity).

MicroStrain 3DM Sensor SpecificationsAngle measurement nonlinearity (pitch

and roll)0.23% F.S.

Angle measurement repeatability

Pitch: 0.07˚ (typical)

Roll: 0.07˚ (typical)

Yaw: 0.26˚ (typical)

Update rate (angle mode)45 Hz/3 channels (maximum) 

30 Hz/3 channels (typical)

Update rate is specified with a maximum and typical value since it depends on how many points the A/D converter averages.

Update rate (raw mode) 70 Hz/ 6 channels

Output modesRaw accelerometers and magnetometers, Euler angles, matrix, accelerometers and

magnetometers vector

Output format RS-232 serial

Transmission Rate 9600 bits/sec

Supply voltage +5.2 VDC min., +12 VDC max.

Supply current 50 milliamps/node @ standard speed

Connectors Sensor: RJ11 type power: min. coaxial jack

Operating Temperature - 25˚C to 70˚C

Temperature Drift (%/˚ C)   Pitch: +/- 0.025%/deg C 0.009 0.008

(mean, std.dev.)  Roll: +/- 0.083%/deg C 0.033 0.025

   Yaw: +/- 0.057%/deg C 0.019 0.019

Module size 1.7" wide, 2.5" long, 0.7 " thick

Weight 75.0 gr. with enclosure, 26.9 gr. without enclosure

3DM® enclosure (.pdf file) 3.5" wide x 2.5" long x 1.0"

Calculations

The sensor outputs the orientation information in 3 different forms: 1) Euler Angles2) Quaternion3) 3x3 Rotational Matrix

Orientation in the form of Rotational Matrix is given in the form:

Orientation in the form of Euler Angles is derived from the rotational matrix. (Calculated using “aircraft”)

Elevation (pitch)

Bank (roll)

Heading (yaw)

)sin( 13MArc

)sin(33

23M

MArc

)tan( 1112 MMArc

Calculations

The rotational matrix can be calculated from a set of Euler angles using the equation below:

Process

Estimated times are given for each task in the process. This allows for an estimated total process time as well as expected maximum and minimum times.

LabVIEW

Interface will allow user to see the angular displacement of the pitch, roll, and yaw of the Lower Lumbar and Upper Lumbar segments based on output from the sensors

Customer will download free LabVIEW Run-Time Engine Output will run as an executable program application

User can only use the application, not change coding

Bill of Materials

BOM

Risk Assessment (Mechnical)

Risk Assessment (Electrical)

Preliminary Test Plan(Mechnical)

Spine Size Verification TestThis test is designed to verify the dimensional constraints of the spine model.

Specifications Tested:1.1, 1.2 2

Visual Inspection TestThe purpose of this test is to verify all non-measureable traits of the spine model. These are specifications that do not have associated dimensions, tolerances or values, but simply are present or are not.

Specifications Tested:3, 4, 5, 22

IR Interference TestThe purpose of this test is to verify that the material finish of the spine model is non-reflective and does not interfere with the customers IR camera system.

Specifications Tested:7

Joint Holding Strength TestThe purpose of this test is to verify that the adjustable ball joint is capable of locking in any given position and can support the weight of a fully articulated spine model.

Specifications Tested:17,22

Preliminary Test Plan (Cont’d)

Durability/Wear TestThe purpose of this test is to test the wear and functionality of the joints and adjustable member sections after repeated use.

Specifications Tested:18

Overall Weight TestThe purpose of this test is to measure the overall weight of the device, which is part of the usability.

Specifications Tested:19

Marker Placement TestThe purpose of this test is verify that the customer is able to mount the reflective markers in the proper location.

Specifications Tested:20

Mechanical Zero TestThe purpose of this test is verify that the mechanical zero device is properly calibrated.

Specifications Tested:21

Preliminary Test Plan (Electrical)

Sensor Measurement Verification This test will verify the digital measurement

with the physical measurement of the mechanical spine. The test will also verify whether the sensor accuracy meets the customer’s needs.

Specification Tested:6, 12

Next Steps…

Implement action items from Detailed Design Review

Actively test ball joint drillingOrder long lead time partsUpdate EDGE with latest informationCreate MSD II schedule