Customer Handoff & Final Project Documentation
Team Vision for Final Demo and HandoffThe goal of this phase was to continue to narrow down the root cause of the issue with the Wheatstone Bridges. The team was able to successfully get about a 1.1mV signal from the bridges, allowing a demonstration to be performed at ImagineRIT.
What we planned on doing
- Detach strain gauges and re-mount them.
- Discover root cause of underlying issue.
- Complete Tech Paper.
- Complete Poster.
- Prepare for ImagineRIT.
What was accomplished
- No changes in strain gauge placement.
- Varied gain on amplification side so voltage change is visible on oscilloscope.
- Narrowed root cause to structure and Wheatstone Bridges. Structure dominated by a bending moment.
- Completed Poster and majority of Tech Paper.
- Developed rig for ImagineRIT.
- Final hand-off of all deliverables and documentation to the customer completed.
- Final MSD deliverables completed.
Final Bill of Materials
Indented Bill of MaterialsThe Indented Bill of Materials provides documentation of all assemblies and sub-assemblies delivered for the project. Each sub-assembly and their components have links documenting either their purchase location or their design (CAD models, Engineering Drawings, etc.), as well as the quantity and materials they are composed of.
Purchasing Bill of Materials
Test Results Summary
Bridge 2 CalibrationThe functional Wheatstone Bridge, Bridge 2, was calibrated in order to determine the equivalent for a given output voltage. This was done in the same manner as the deflection verification test, with the device placed in a 7/8” collet in a mill, with a steel cable threaded through a test tip and a pulley system. Set weights of increasing weight were placed on a mass hanger attached to the end of the cable to apply a transverse load to the tip of the structure, replicating the transverse loading condition it would experience during a machining process. Plotting the applied load versus the differential output voltage of the Wheatstone bridge and fitting the curve with a 2nd-order polynomial function allowed the development of a calibration formula. With this, the user can interpret the voltage readings from the device to get the transverse load it is currently experiencing.
Full Summary of TestingThe Testing Summary document provides a detailed summary and analysis of all tests ran during this project's span. Links are provided to individual tests' sections on their respective EDGE pages, as well as the actual documentation of each test.
The link below shows the individual summaries of each of the tests ran during the Integrated System Build & Test phase.
This document outlines the successes and short comings of the final device compared to the engineering requirements.
Risk and Problem Tracking
- The team setup a pulley and a cable with a spring scale such that when the cable is pulled the measurement structure experiences a force which can be measured by the spring scale.
- An oscilloscope was attached to the measurement structure to show the output signal due to the force.
- Overall, the exhibit ended up being a success! The children in attendance enjoyed trying to find out "how strong they are!"
Final Project Documentation
Mechanical AssemblyThe assembly of the mechanical structure is as follows:
- Acquire the tool being used for the task
- Find appropriate DA180 style collet size for the tool
- Insert tool into collet and insert collet+tool assembly into tool holder
- Place tool holder into a holding block and tighten with a 1.25" wrench
- Insert tool holder into adapter and align cutouts with two posts sticking out of the adapter
- Tighten tool holder in place with a 1/2-13 bolt
- Attach the lower assembly to the structure using the 4 1/4-20 bolts and threaded holes
Electrical AssemblyThe assembly of the electronics of the system is as follows:
- On the measurement structure, connect the wires labeled 2/1 (white), 9/13 (yellow), and 17/21 (green) to 3.3 volts.
- On the measurement structure, connect the wires lableded 7/4 (white), 16/12 (yellow). and 20/24 (green) to ground.
- Connect the following differential pairs to
individual amplifiers on amplifier boards:
- 6/3 (white) to negative and 5/8 (white) to positive
- 11/14 (yellow) to negative and 15/10 (yellow) to positive
- 23/22 (green) to negative and 19/18 (green) to positive
- Connect positive power rail of amplifier to 3.3V and negative power rail of amplifier to ground.
- Connect VCC and GND pin of MSP430 to 3.3V and ground respectively.
- Connect TX pin of MSP430 to RX pin on bluetooth transmitter.
- Connect VCC and GND pin of bluetooth transmitter to 3.3V and ground respectively.
- The circuit should now be functioning. A serial port communication program such as RealTerm can now be used to obtain the data.
Circuitry PlacementThe order of placement of the circuitry into the housing:
- Place MSP430 into the respective slot
- Place the MS430 bracket over the MSP430
- Use square nuts size 3M and corresponding screws and then do the same for PCB boards
- Slip square nut size ¼ in for battery lid and
counter weight lid into the corresponding hole
- This hole is harder to see clearly, the hole is square and is along the wall of the battery compartment and counter weight compartment
- The hole intersects the screw hole of the battery compartment and counter weight compartment
- Once these screws are in place they shouldn’t be removed unless there is a serious problem with the circuit.
- Solder the wires to the MSP430, Bluetooth, battery, and amplifying circuit while they are setup in the 3D housing.
- The Bluetooth antenna can be glued to its slot to better secure it.
- The wires coming off the separate Wheatstone bridges
plug into one of the PCB boards and then gets connected
to the amplifying circuit.
- The PCB board that the Wheatstone bridge connects to should be wired up before attaching to the 3D housing.
- Carefully insert the wired components into the housing.
Electrical HousingThese documents provide the drawings and specs in order to recreate the 3D Printed electrical housing.
The team has compiled all items from both workspaces (EE Lab and Dr Liu's Lab) and has placed it in a single box in Dr. Liu's Lab. Major items in the box are:
- The measurement structure with toolholder acceptor & adapter
- 3D printed measurement structure mock-up
- Excess strain gauges team did not use
- 2 MSP430 Launchpads
- Amplifier Circuit soldered onto breadboard
- Additional INA122 amplifiers for testing
- 3D printed housings
- 2 Serial Bluetooth Modules
- Trustfire batteries with charger
- ImagineRIT Exhibit Items
- Spring Scale
- Cable with clamps
Recommendations for future workThe following are excerpts from the technical paper outlining recommendations for future teams that may try to tackle this project:
 “National Instruments Software License Agreement”, National Instruments Software License Agreement – National Instruments, Addendum E-Academic Licenses, May 2015. [Online] Available: http://www.ni.com/pdf/legal/us/software_license_agreement.pdf [Accessed: 10-May-2017].
 "Free 6-Month Evaluation of LabVIEW Student Edition for At-home Learning." Free 6-Month Evaluation of LabVIEW Student Edition for At-home Learning - Discussion Forums - National Instruments. National Instruments, 20 Mar. 2017. Web. 11 May 2017.
- Use shielded wire for to decrease noise in voltage signals.
- Pre-filter and condition signal before amplification on the hardware side for a more reliable output.
- Possibly find a dedicated wireless DAQ device already out in the market.
- Use a PCB board for the amplification circuit for a smaller footprint.
- Add a negative rail to the power for amplifier.
- Use precision offset resistors to zero out the Wheatstone bridge circuits.
- Increasing the diameter in some of the iterations
caused the deflection to increase; this is likely a
result of the initial deformation occurring at the shaft
of the structure.
- The increase in diameter should open up the potential for easier strain gage mounting and a greater distance for the strain to act over.
- Design the structure with a shorter distance between
where it attaches to the mill and the tooltip to decrease
- Finding a better way to attached the tool-holder to the measurement structure would drastically reduce the overall length of the device.
- This will result in a subsequent decrease in strain experienced in the legs, which will need to be addressed to keep strain within safely measurable orders (10-6 to 10-2).
- Decrease leg cross-sections to maximize strain in the
legs with a minimal increase in overall deflection.
- Performing optimization routines on square cross-sections and rectangular cross-sections would be beneficial in determining the optimal cross-sectional area for a maximum strain and a minimal deflection.
- Appropriate use of structural chamfers, rounds, and
radii to form uniform areas of strains in the legs of the
measurement structure will ensure the strain gauges will
measure a uniform amount of strain.
- An iterative analysis performing changes to CAD models, then running the updated models through ANSYS is time-consuming and tedious.
- Consulting a textbook on structural design may be a better solution.
- Decrease the shaft diameter down from the 7/8”
that it currently is to something closer to
¾”, keeping in mind the nominal 5C collet
- This will increase the amount of strain seen in the legs of the measurement structure, but will also result in higher amounts of tool-tip deflection.
- With a shorter overall length of the structure, this increase in deflection will be minimal due to the decrease moment arm.
- The Construct at RIT was incredibly beneficial for 3D printing the housing and should be utilized to the full extent of their capabilities.
- The Construct also has 3D scanners available for use
which may be helpful to mock up design of the device.
- If a new electrical housing is desired, then use the 3D scanners to fit the cad model to make changes to the electrical housing.
- Due to the low tolerances of 3D printing, some
sanding or finishing may be needed to get parts to fit
- Rough grit sandpaper proved to be the most effective when sanding down 3D printed materials.
- The current design of the structure is not
load-bearing and the top part of the counter-weight side
is very fragile and susceptible to pressure applied to
- This particular section was broken twice during the project, once from excessive force used to fit the pieces together, and once from falling off of a table.
- A redesign of this particular area may be useful to reduce its fragility.
- Although the structure is easily damaged by high-impact loads, it should be able to perform its function of containing the electrical components during rotation of the device.
- Careful attention should be applied to the dominating
load for the structure, that is the load with the
greatest order of magnitude of resulting strain.
- Both the magnitude and sign (compressive or tensile) of this strain will be very important when determining the optimal way to configure the Wheatstone bridges on the device.
- Proper orientation of the strain gauges is also very
important in order to measure the correct direction of
- A placement guide for strain gauges should be consulted based off of the dominating load, in order to ensure that all gauges will be properly aligned to detect the resulting strain.
- Although linear strain gauges were used for this project, multi-directional strain gauges may be more cost-effective by reducing the overall number of gauges needed.
- The FEA for this project was performed using a
research license for ANSYS which allowed a significantly
greater number of nodes and elements to be used in the
- It is recommended that subsequent team members be chosen from the Formula team due to their access to this license
- This project requires an in-depth knowledge of
Strengths of Materials as well as machining.
- Sourcing future team-members from student workers in the machine shop, members of the Formula or Mini-Baja team, or grad students with a focus in Strengths would be very beneficial
Functional Demo Materials
- Wire cable + wire clamps
- Oscilloscope + probe
- Spring Scale + handle
- Power Supply for 3.3V to Yellow Wheatstone Bridge
Plans for Wrap-up
- EDGE Website Completion.
- Work Space cleanup in Dr. Liu's Lab and EE Senior Lab.
- Self-assessment for norms/values.
- Peer Reviews.
- Lessons Learned
- MSD Recommendations for Gate Review
- Lightning Presentation
Post MortemThis document highlights the objective analyses throughout the year of MSD I and II, as well as the assessment of the team vs. the norms and values.
|Project||Validation/Analysis||Mechanical Design||Electrical Design||Academic|