P16221 – FSAE Shock DynamometerPreliminary Detailed Design Review

November 13, 2015

• Aung Toe – EE• Jim Holmes – EE– Project Manager

• Sal Fava – ME– Chief Engineer

• Chris Batorski – ME– Facilitator

• Andrew Dodd – ISE

P16221 – MSD Team

• 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• Team Efficiency

Agenda

• Concerned about quantity of data transferred– Put two micros in: one for sensor read and one for dyno

control– Sample only important sections of track data

• Add internal frames to the energy chart that shows the internal resistances to energy transfers

• Verify that the load cell will not measure its own internal deflection, just the force applied to it– Verified by spec sheet

• Track the severity chart sum over time to show progress– Chart created and updated weekly (owned by Jim)

Resolved Issues From Previous Review

• Keep verification testing in mind during the design process to make testing easier at the end– Developing test plans now

• Customer movement metric needs to be better defined– Complete. See engineering specs

• Due to the dynamic nature of the dyno, a timing diagram should be created– Timing Diagram

• Need a reasonable life expectancy of the dyno and write a spec on it– See engineering specs for life cycle and maintenance interval

Resolved Issues From Previous Review (Cont.)

• What will keep the dyno from “walking across the floor” while it is running?– Open issue. Will need to perform isolation analysis from

dyno to floor

• Develop an Engineering Analysis vs. Risk vs. Verification Test metric to make sure everything is covered.– Still in progress

• Any function in the system functional block diagram with only one child should be combined into one block– Low priority, still in progress

Open Issues From Last Review

Engineering Requirements

BOM

Predicted Costs

System Level DesignFlowchart

• 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

Subsystem DesignSafety

Major Components• Aluminum Extrusion Frame

– Minitec 45x45 F

• Plastic Shielding– Polycarbonate sheeting

• Door• Safety Latch• Safety Circuit

Interfaces• Test stand base

– Bolted to base

• Work Area– Surrounds the masts and test

area

• Emergency Stop Switch– Will be mounted to the frame

Safety Sub-SystemOverview

• 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

Subsystem DesignSoftware Interface

Software InterfaceProposed Input Display

Total Vehicle Weight 235 kg Front Rear%F Weight Dist 48 % Wheel Rate Kw (N/mm) 21.7 28.9

F Unsprung (by Corner) 6.85 kg Ride Rate Kr (N/mm) 17.6 22.0R Unsprung (by Corner) 7.12 kg

F Spring rate 26.3 N/mmF Motion Ratio 0.909 shock/wheel Sprung Mass ωn(s) (Hz) 2.996 ccr(s) (Ns/mm) 2.282R Spring Rate 35 N/mm Unsprung Mass ωn(us) (Hz) 13.320 ccr(us) (Ns/mm) 1.799

R Motion Ratio 0.909 shock/wheel Sprung Mass ωn(s) (Hz) 3.214 ccr(s) (Ns/mm) 2.180F Tire Spring Rate 91.8 N/mm Unsprung Mass ωn(us) (Hz) 15.086 ccr(us) (Ns/mm) 1.901R Tire Spring Rate 91.8 N/mm

Front 25.40 Low Speed High Speed Ns/mm N at 25.4 mm/s Ns/mm N at 25.4 mm/sRear 25.40 Front 3.00 1.25 Front 6.85 173.87 4.56 115.92

Rear 2.50 1.13 Rear 5.45 138.42 3.63 92.28

Rebound CompressionFront 1.00 1.50Rear 1.00 1.50 Ns/mm N at 254 mm/sec Ns/mmN at 254 mm/secFront 0.65 1.00 Front 2.25 571.17 1.46 371.26Rear 0.70 1.00 Rear 2.14 543.17 1.50 380.22

High Speed

Rear

ResultsDecisions Low Speed

Knee Speed (mm/s) Desired Damping Ratio (c/c crit) Compression Rebound

Compression/Rebound RatioHigh Speed

Low SpeedCompression Rebound

Damper CalculationsCar Parameters Calculations

Resonant Frequency Critical Damping

Front

Equations Variables

• 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)

Software InterfaceCalculations

Software InterfaceResults (Characterization)

Software InterfaceResults (Track Data)

• Large components placed in the model

• Safety enclosure not shown

Model Overview

• Overview of some simple design practices

Mechanical Design

• Forced on arm at Given locations

• Determine if there are any points of concern

Motion Ratio Arm

• Determine the min diameter shoulder bolts that can be used in each location

Shoulder Bolt Sizing

• Buckling Calculation

Hand CalculationsMast Sizing

Crossbar Clamping Calculation

Electrical System Schematic

Electrical System Schematic

Proof of Concept:Controller

• Safety Circuit Loop • Force sensor/ Potentiometer resolution test• IR sensor safety circuit test• UART and PC interface test

Proof of Concept:Testing to be done

• IR sensor test

Proof of Concept:Testing so far

=

• Additional testing required for higher temperature

• 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

Theoretical Models: Serial Interface (UART)

Theoretical Models: Data Flow

Risk Assessment

Risk Assessment

Updated Project Plan

• Atmel Temperature Sensor Test: Initially took 3 days; could repeat in an hour. Efficiency (3%)

• 3-D Model: Initially took 2 team members about 6 hours a piece; probably could repeat in about half of the time. Efficiency (50%)– Note: Still in progress

• Source Ball screw that will meet our needs: Initially took a few weeks; could repeat in an hour. Efficiency (1%)

Team Efficiency

Questions?