Content related to this node is located in the Detailed Design Documents directory.
Team Vision for Detailed Design Phase
During this phase, the team...
- Continued to increase detail in device design and CAD model.
- Performed experiments with electromagnetic brake set up from last year.
- Used left over materials from P17044 to create a hand component prototype.
- Used left over materials from P17044 to create a test rig so that control logic can be tested at the beginning of MSD II.
- Stuck to the phase 4 project plan because we were very limited for time.
- Discovered new risks for our current design that need to be addressed.
- Ordered critical build materials.
Progress ReportCurrent Status (11/20/17):
- Specific device design (in progress)
- BOM near completion
- Draft of test plans
To be complete for end of semester (as a group):
- Completed design
- Answering key phase 4 questions
- Completed test plans
- Purchasing of critical items
- Defining specific EE needs for rest of phase and for MSD II
Specific tasks for when we get back from the holiday ( please see phase 4 project plan on edge for more task break downs):
- Planning / obtaining materials for heat generation per brake test and experimental strength per brake testing (to be completed in class 11/27)
- Getting test rig ready for 1D testing of control logic
- Control logic in 1D
- Researching feasible heat sink options
- Researching magnetic brake optimization/ modeling , potentially implement model
- Determine feasible method to automate 'tremoring' of test rig
- Increase detail in CAD model
Prototyping, Engineering Analysis, Simulation
Heat Generation Test
Purpose: To determine the temperature output of the magnet while a brake is engaged for a long period of time.
- Test began with magnet at room temperature.
- Current draw of 225 mA.
- Temperature of magnet was taken with an infrared thermometer 2 inches from the engaged magnetic brake. Note that a piece of masking tape was placed on the surface of the magnet so that the thermometer still worked accurately.
- Temperature was recorded at 30 second intervals for ten minutes, 1 minute intervals for 5 minutes, 5 minute intervals for 20 minutes, and then 10 minute intervals for 30 minutes.
- Magnet temperature does not significantly exceed body temperature in this use case.
- When circuit is optimized, a temperature test for a longer period of time can be performed with the magnet switching on and off at a frequency within the range of Essential Tremor frequency to simulate temperature of the magnet in a more relevant use case.
- As of now, we believe that the brake housings (aluminum) will provide enough surface area to safely dissipate heat, bottom of brake housing will be insulated to protect the wearer from exposure.
Control Logic Test
Purpose: Determine the maximum force one electromagnet brake can withstand and compare to theoretical value (25 N).
- Test setup as shown in image below
- The electromagnet was supplied with 225 mA.
- Weights were hung on the cable until the brake slipped.
Mean slip force: 14.1 N, Standard Deviation 1.78 N
- Experimental value was 56.4% percent of theoretical value.
- If the force required to cause the brake slip is determined to be inadequate during testing, the following changes can be made during building.
- Magnets can be doubled up per brake line (Feasibility - High)
- Frictional coefficient of brake material can be increased. (Feasibility - Moderate)
- Thickness of air gap can be decreased. (Feasibility - Low).
- Current feeding magnets can be increased. (Feasibility - Moderate).
Power Draw Calculations
V = 8.8V
R = 40Ω
I = 8.8/4 = .22A
P = 1.936W
I = 1.1A
P = 9.68W
Drawings, Schematics, Flow Charts, Simulations
Updated CAD Drawing
Alternate CAD Models
Updated Control Logic Flowchart
Bill of Material (BOM)
Design Review Materials
Plans for next phaseGoals for rest of semester to be prepared for MSD II:
- Documentation for gate review.
- Gate review.
- Agree on meeting schedule for MSD II.
- Remain in contact with our new EE, make sure he will be up to speed before semester begins.
- Order remaining long lead items.