1. P16221 – FSAE Shock Dynamometer Preliminary Detailed Design Review
November 17, 2015

2. P16221 – MSD Team Aung Toe – EE Jim Holmes – EE Sal Fava – ME
Project Manager
Sal Fava – ME
Chief Engineer
Chris Batorski – ME
Facilitator
Andrew Dodd – ISE

3. Agenda Address concerns from System Level DR
System Level Design Flowchart Updates
Engineering Spec Updates
Current Bill of Materials
Safety Considerations
User Interface (software)
Model Overview
Mechanical Systems Analysis
Electrical Schematics
Risk Management
Project Plan

4. Background: Problem Statement
The goal of this project
Design a device to characterize dampers
Capable of supplying a displacement input profile in time and measuring force, displacement, and temperature responses of a damper

5. Resolved Issues from Sub-system Level DR
Maintenance interval concerns
Based on purchased components and fatigue life. For example, bearing life.
Will develop a maintenance and assembly guide
Safety enclosure really necessary?
Yes, designed to keep fingers out of pinch points as well as protect from shrapnel in the event that something breaks
Potential racking issue
Assembly is very symmetrical
Connecting rod introduces less than 200lbf out of plane

6. Issues from Sub-system Level DR
Rust concerns on stand
Steel components will be painted
Potentially make mast out of aluminum
How did you arrive at the selected board and microprocessor
Based on data transfer needs, ADC resolution and 32 bit processing power
Frame deflection
Low priority-will investigate for DDR

7. Issues from Sub-system Level DR
Magnetic vs optical isolators
Optical isolators offer sufficient speed
Hire electrician for 208V
Need to finish motor circuit to request a quote
Test plans using function generator for data transfer
Will define after software is written
Start to outline rotary design
Design is now based on rotary design
Never got a definitive answer on ball screw actuator

8. Open Issues From Last Review
What will keep the dyno from “walking across the floor” while it is running?
Initial estimate and calculations complete
Develop an Engineering Analysis vs. Risk vs. Verification Test metric to make sure everything is covered.
Still in progress, has been started
Any function in the system functional block diagram with only one child should be combined into one block
Low priority, still in progress

9. Engineering Requirements

10. BOM

11. Predicted Costs

12. System Level Design Flowchart

13. Subsystem Design Safety
Goals of sub-system:
Protect user from serious damper failure
Not impede user activities within working zone
Low cost
Important features
Enclosure
Emergency Stop Switch
Safety Door Lock
Safety Circuit

14. Safety Sub-System Overview
Major Components
Interfaces
Aluminum Extrusion Frame
Minitec 45x45 F
Plastic Shielding
Polycarbonate sheeting
Door
Safety Latch
Safety Circuit
test plan
Test stand base
Bolted to base
Work Area
Surrounds the masts and test area
Emergency Stop Switch
Will be mounted to the frame

15. Safety System Enclosure Design
Overall Dimensions
Height: 48 in
Depth: 12 in
Width: 36 in
Bolted to table
8X 5/16-18 Bolts
Held together with custom designed brackets
An effort to reduce cost of the system

16. Safety System Door Design
Overall Dimensions
Height: 46 in
Depth: 12 in
Width: 32 in
Currently Designed with Standard MiniTec hinges and handles
Could replace with custom parts

17. Safety System Custom Plates
Top Plate
Used to hold top of enclosure to the uprights
Thickness: ¼ in
Material: Aluminum
Bottom Plate
Bolts the enclosure assembly to the test stand
Thickness: 7/16 in

18. Safety System Door Interlock
Used to lock the enclosure when test is being run
IDEM 16.5mm Mount
Safety Switch: $29.50
Actuator Key: $11.50
Available from Automation Direct

19. Subsystem Design Software Interface
Goals of Subsystem
Provide user with a way to control and program the test stand
Post processes the raw data and saves it in .csv format
Important Features
Car Parameter Inputs
Track Data/Profile Selection
Post Processing
Graph Display

20. Software Interface
Efficiency (83%): Took 6 hours to perform this task as it stands.
Would take approximately 5 hours to redo.

21. Software Interface Calculations
Equations
Variables
𝐾 𝑤 = 𝑘 𝑠 ∗ 𝑀𝑅 2
𝐾 𝑟 = 𝑘 𝑡 ∗ 𝐾 𝑤 𝑘 𝑡 + 𝐾 𝑤
𝜔 𝑠 = 1 2𝜋 𝐾 𝑤 𝑚 𝑠
𝜔 𝑢𝑠 = 1 2𝜋 𝐾 𝑤 + 𝐾 𝑡 𝑚 𝑢𝑠
𝑐 𝑐𝑟𝑠 =2 𝐾 𝑤 + 𝑚 𝑠
𝑐 𝑐𝑐𝑢𝑠 =2 𝐾 𝑤 + 𝐾 𝑡 ∗ 𝑚 𝑢𝑠
Kw = Wheel Rate
Ks = Spring Rate
MR = Motion Ratio
ωs/us = Natural Frequency (sprung/unsprung mass)
ms/us = Mass (sprung/unsprung)
ccrs/us = Critical Damping (sprung/unsprung mass)

22. Software Interface Results (Characterization)

23. Overall System Geometry
From SSLDR

24. Load Cases/Constraints
350lb marginal, 500lb ideal vertical force through the actuator, damper and into the crossbar
FOS of 2 used in all calculations
Design for stress levels under the endurance limit, infinite fatigue life
Welded structure Knockdowns
Aluminum weld-area strength= 0.5 base material
Steel weld-area strength= 0.8 base material
Ideally every component in a system would have Margin=0
Positive = over-designed
Negative = under designed

25. Analysis: Isolator Sizing
Efficiency: Isolator Sizing – Initially took 1 evening, could repeat in 1 hour.

26. Analysis: Mast Sizing

27. Analysis: Clamp Load

28. System Forces

29. Gearmotor Selection
Efficiency: Gearmotor Selection - Initially took 3 days; could repeat in an hour. Efficiency (3%)

30. Gearmotor Selection

31. Actuation Assy
Efficiency ~5%

32. Interfaces/Clearances
Over 1.5in between damper and slider
Small clearance between clevis and damper

33. Forces

34. Shoulder Bolt Sizing
Determine the min diameter shoulder bolts that can be used in each location

35. Impulse High Impulse load of 1800 lbf Shear Pin needed
Efficiency 37.5%:
Took about 4 hours
Could repeat in 1.5 hours

36. Preliminary Bearing Selection
SKF NU 202 ECPHA
Far exceed dynamic load rating
Fatigue rating needs to be further evaluated

37. Arduino Dataflow

38. TI ISO124 Analog Isolator

39. VISHAY CNY17 Digital Isolator

40. Electrical System Schematic

41. Electrical Wiring Schematic

42. Power Management

43. Power Management

44. Serial Interface Test

45. Proof of Concept: Testing so far
IR sensor test
𝑇𝑒𝑚𝑝(𝐶)= 𝐴𝐷𝐶𝑟𝑒𝑎𝑑𝑖𝑛𝑔(𝐷𝐸𝐶)∗ 𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 𝑣𝑜𝑙𝑡𝑎𝑔𝑒 𝑚𝑉 2 𝑛 −𝑜𝑓𝑓𝑠𝑒𝑡(𝑚𝑉) 𝑆𝑒𝑛𝑠𝑖𝑡𝑖𝑣𝑖𝑡𝑦 ( 𝑚𝑉 𝐶 )
= 348∗ − =0.82𝐶
Additional testing required for higher temperature

46. Tests Planned Analog Isolation Digital Isolation Safety loop test
UART and PC interface test

47. Theoretical Models: Serial Interface (UART)
Serial Speed Analysis
Inputs
Memory Requirements (64 bits of data in 0.002s)
Output
32,000 bits/s
Conclusion- feasible baud rates:
38,400
56,000
115200

48. Risk Assessment

49. Risk Assessment

50. Updated Project Plan

51. Questions?