Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
For this phase, our team's plan was to:
- create a preliminary Bill of Materials
- investigate mitigation of risks defined in previous phases
- test for the force required to strike a key
- perform solenoid tests to confirm our solenoid selection
- update Pugh charts and finalize other evaluations for our design to be efficient and logical
- continue our preliminary CAD models and drawings
- begin work on parsing a MIDI file
- produce electrical schematic
- CAD model
- Preliminary BOM
- Demonstrated proof of concept
- Investiated requirements to ensure on track to meet important ones.
- Created documents for testing and confirming engineering requirements
- Adequate review of design
- Final Detailed Design Review: 12/7/2016
- All major subsystems will be adequately reviewed and designed
- Finalized Bill of Materials to begin purchasing
- Expected results of device compared to engineering requirements
- Testing plan for each requirement
- MSD II Action Plan
- Gate Review: Week of 12/12/2016
- Final Go-No Go for MSD II
- All outstanding questions, design problems will be addressed
- The team, guide and customer will sit down and confirm that current design will meet all customer expectations going into MSD II and how any concerns will be addressed.
Prototyping, Engineering Analysis, Simulation
Engineering Requirements Update:
- Green represents requirements addressed in this phase with positive results while yellow and red represent more negative results
- The importance of each requirement was also updated to reflect the customer requirements
- All high importance requirements addressed
Began preliminary testing components of our system.
- confirmed our solenoid choice has enough force to actuate a key
- confirmed repeated hits from the plunger is sufficiently fast
- confirmed through 3D modeling that space for array of solenoids is sufficient
Feasibility: Prototyping, Analysis, Simulation
The following snap shots from the CAD model prove that space is sufficient for a 1" wide solenoid.
This mounting technique will mitigate any damage to existing piano. It is a circular rubber mount on a slider pin which slides into the dowel rod and is pushed outward by a nut to tighten. The following picture shows the nut visible while the next one after that shows the dowel with out the nut.
This is the plunger cap that will be secured to the end of the plunger of each solenoid. It is secured by a rod running though the plunger hole. The hole on the top of the cap is threaded and the wire will be secured by tightening it with the screw.
This allows for the tension of the wire to be easily adjusted instead of the location of the solenoid.
Drawings, Schematics, Flow Charts, Simulations
Bill of Material (BOM)
PurposeConfirm that all expenses and contingencies are afforded by the project financial allocation
PurposeTo test different solenoid types for use on the automated piano.
Solenoid 4 Driver Schematic
Alpha Prototype Electrical Schematic
Force TestingIn order to determine if the solenoids would be powerful enough to actuate a piano key, we must first know how much force it will take to do so. This was done via use of a force varying resistor. The resistor was place between the lever of the piano and a block held in place. The picture below shows the model of the sensor and holding block.
When the given key was actuated it the resistance of the force sensor would change. Through use of a voltage divider and ADC on the uController the resistance value could be determined. The circuit used to connect to the uController is shown below.
Once that was determined a chart provided in the datasheet of the sensor provided the force value. The chart is shown below.
Solenoid TestingOnce the force required was determined the solenoid test fixture could be calibrated. This was done with a pretension-ed spring. A picture of this fixture is shown below.
The distance to tension the spring was found by initially calculating the spring constant. This was done with a basic weight vs. distance analysis. A more in depth view of this process is found in the test procedure document. Once the constant was found the basic Hook's law equation was used to get the distance to tension the spring to. The device was setup and ready to test.
A mounting was designed for each solenoid to be tested. The picture below shows the basic setup.
The solenoid was then connected electrically to the testing circuit. This circuit controlled the solenoid through a PWM signal and a power transistor. The schematic and actualized circuit are shown below.
With each subsystem combined into one test fixture the design verifies most of our largest concerns and is a great starting point to model how the system as a whole will function. A picture of the completed assembly is shown below.
A detailed process including all equations and data values can be found in the link below.
Design and FlowchartsThe updated flowchart is shown below. The red boxes show which portions were constructed and tested during this phase.
Risk AssessmentGreen risks are currently being mitigated while the red signifies that the risk is out of scope. The white risks don't have a specific mitigation method but are a culmination of methods through out the document.
Design Review Materials
Plans for next phase
Team Plans for next phase
- Finalize mechanical designs (CAD Model)
- Finalize electrical designs (Schematics)
- Determine remaining risk mitigation plans(s)
- Finalize Bill of Materials
- Determine vendors to order from
- Design initial cable management layout
- Further refine software UI
- Test latency due to communication methods
Individual Goals for next phase
- Matthew Mack
- Design schematic and code for temp. testing with thermistors
- Construct initial timing diagrams for uController
- Serial communication from Pi
- "Writing" values to solenoids
- Read temperatures from thermistor circuit
- Interrupt/Poll key detection
- Copy existing code to MSP432
- Tyler LeGracy
- Finalize electrical schematic
- Notes played feedback system design
- Finalize Bill of Materials
- Ben Parnas
- Continue testing solenoid with PWM curves/frequencies
- Experiment with different MOSFET technologies
- Verify low-noise operation and dampening methods
- Formulate Key-press circuit
- Work on PCB schematic/layout for solenoid driving
- Scott Porter
- Determine basic layout of wire harness/PCB locations
- Investigate solenoid heat mitigation methods
- Determine method for actuating pedals
- Further develop Detailed Design schedule
- Tim Doores
- Help with cable management
- Finalize design - solenoid placement/ rod adjustment
- Help dampen solenoid noise
- Assist testing system (piano background)
- Michael Riola
- Finalize mechanical design and make prints
- Build prototype in piano
- Dampen solenoid noise
- Help with heat management
- Translate JSON output to serial output from pi
- Polish UI and interface
- Work with Danny to split the MIDI in to left and right hands
- Split contents of MIDI into left and right hands
- Research possible RTOS implementations on the microcontrollers
- Begin looking into note dynamics based off player feedback