MAE126B - PROJECT E5

M-BEAM PROJECT PROCEDURES

UPDATED April 15, 2016

Description This project looks to research, analyze, and develop a modular battery exchange system for an electric vehicle. The

exchange of light-weight autonomous battery modules will allow depleted modules to be swapped for full ones manually.

By allowing the batteries to be exchangeable and replaceable manually, EV drivers can be alleviated with range anxiety

and can allow their vehicles to be driven with far ranges without having to stop to recharge.

Main Tasks & Goals ● Demonstrate feasibility of a swappable modular battery solution in an EV

● Test drive the vehicle and collect data

● Based on measurements, predict efficiency/range and ways to improve them

● Predict pit stops for a cross country drive

Week 1 Procedures Meet with Professor and get an overview of what the project entails.

Week 2 Procedures First, understand the math and physics behind the measurements that will be necessary in analyzing the vehicle’s

efficiency.

A. Determine the factors and variables that play a role in mechanical power of the vehicle.

B. Draw necessary free body diagrams of the vehicle to see all of the forces acting on the vehicle.

C. Determine which measurements can be found and which ones need to be calculated.

D. Go over equations with Professor Callafon and Xin.

Additional Questions

1. What assumptions can be made to simplify some of the equations? Why can we make such assumptions?

Discussion

1. Discuss ways to measure the different forces acting on the vehicle.

Week 3 Procedures Develop a step by step plan on how we are going to go about measuring the unknown measurements. Also create a

weekly plan for the next steps for the project. From the meeting, the team determined equation of mechanical power as:

+ + or simplified as + + , and(c mgPm =   r + AρVc21d

 w2 in(α)mgs V )m ′c ∙V c (c mgPm =   r + Vcd

 w2 in(α)mgs V )m ′c ∙V c

now there are several variables the team needs to find out through experiment.

A. Calibration calculation of vehicle acceleration ??V ′c

B. Verify ᵳ� calculations

a. Constant speed test

If = 0 (no acceleration) then = V ′c α ( )tan−1 z′′x′′

b. Acceleration test

If (car is accelerating) then = =V ′c / 0 α ( )tan−1 z′′x −V′′ ′c

C. Determine the coefficient of drag in rolling force equationcr

D. Determine if coefficient of drag is dependent on velocity

E. Determine weight of the vehicle gm

F. Determine best location for pitot tube for accurate measurement

G. Determine relationship between pitot tube measurement and wind velocity

H. Determine constant coefficient of drag force term c Aρ 21d

Test plan:

Experiment A: verify calculation for incline slope

a. Flat road, constant velocity

1. Using GIS, determine a location where there is a long stretch of flat road ( =0). Data on theα

topography of San Diego- and more specifically La Jolla- is available from the SanGIS Data Warehouse.

From SanGIS a shapefile containing all major roads in San Diego county can also be downloaded and

imposed upon the topography data. Using the measure tool, a stretch of

2. Drive the car so that a constant speed is maintained with no acceleration, drive for 30 seconds or so

with constant velocity. Possibly use cruise control to keep speed at constant.

3. Ideally, under these conditions, . Verify that this is accurate; if not, determine if  tan(0)  0z′′x′′ =   =  

there’s a relationship between and α z′′x′′

b. Flat road, with acceleration

1. On the same stretch of flat road, drive for 30 seconds with varying acceleration of __m/s^2

2. Measure ay (from myrio)

3. Calibrate

4. Now use the equation = or = to verify the accuracy of this equationα ( )tan−1 z′′x −V′′ ′c α ( )sin−1 g

V −x′c ′′

5. Ideally, = 0, and =1z′′x −V′′ ′c

gV −x′c ′′

6. Calibrate the equations = and = α ( )tan−1 z′′x −V′′ ′c α ( )sin−1 g

V −x′c ′′

c. Sloped road, no acceleration

1. Using GIS data, determine a location where there is a long stretch of road with constant incline

2. Drive the car by maintaining constant velocity, obtain data for 30 seconds of driving with no

acceleration

3. Plot , and verify that it is the constant angle the road is estimated to be from GIS data( )tan−1 z′′x′′

d. Sloped road, with acceleration

1. On the same road, drive the car at constant acceleration for 10-30 seconds, and plot vs( )tan−1 z′′x −V′′ ′c

time, and vs time. These plots should have constant straight line where y value is hill( )sin−1 gV −x′c ′′

slope

Additional Questions

1. How can you obtain constant acceleration on car? How can you obtain real time acceleration within the car?

a. Implement labview acceleration calculation to be displayed real time in myRIO and on the tablet in the

car

2. Is there cruise control feature on the car?

3. Constant air density assumption? Is it accurate, do we need an experiment to verify?

Discussion (Meeting with Professor)

- Measuring acceleration frequency of 10Hz

- Making sure that the controls (MyRio) needs to be perfectly aligned with the car to ensure that its measuring in the same direction as the car is moving

- Sensors measure in G’s

- Finding a road that has a constant slope is more important (highway 8)

- GPS receiver shows the exact coordinates of the car

- Check where the car was during the drive, before the drive and after

Week 4 Procedures Develop a step by step plan in order to find the rolling coefficient and dependency on Velocity.

Experiment B: Rolling coefficient and dependency on Velocity

a. Flat road, constant velocity

1. Using the GIS, find a flat residential road

2. Drive at a constant 5mph (or less) in gear 1 for 30 seconds

1. Try to keep at slow speed and then try to keep gas pedal constant

3. Neglect drag, slope, and acceleration forces for these conditions

4. Use the modified mechanical power equation =Pm mgVcr c

1. Assuming 100% efficiency

5. Assume 100% efficiency so that = and =Pm Pe mgVcr c IV b b

1. Calibrate voltage measurement (talk to Lou)

6. Solve for cr

Additional Questions

1.

Discussion

Week 5 Procedures Develop a step by step plan on how to optimize using the pitot tube.

Experiment C: Pitot tube optimization, relationship between voltage measurement and wind velocity*

a. Must be done on a not windy day or at a location (La Jolla is not the most ideal) where winds are minimal

1. Test locations on car where pitot tube gives a relatively stable voltage measurement reading at some

constant test velocities (20, 30, 40mph)

a. Under the car

b. On top of the roof of the car

c. On top of the hood of the car

d. On the side (driver or passenger door)

e.

2. With pitot tube location set, collect data of voltage measurement readings at test velocities (20, 30, 40,

50, 60, 70mph)

a. Expected to have a nonlinear relationship between wind velocity and voltage measurements

b. Plot polynomial and exponential fits to determine which trend is most reflective of actual

measurements

c. Find coefficients of fit so we can simply enter a voltage reading and the fit can return a wind

velocity

*assume wind velocity is negligible; therefore, car velocity is wind velocity

Additional Questions

1.

Discussion

Week 6 Procedures Develop a step by step plan on how to find the wind drag coefficient.

Experiment D: Wind drag coefficient =cd c Aρ 21d

a. Flat road, constant velocities

3. Make sure it is not a windy day

4. Use the road from Experiment A

5. Drive the car at regularly spaced, higher constant speeds for 30 seconds

a. 50mph

b. 55mph

c. 60mph

d. 65mph

e. 70mph

f. 75mph

g. 80mph (?)

6. Neglect rolling, slope, and acceleration forces for these conditions

7. Use modified mechanical power equation =Pm Vcd w2

8. Assume 100% efficiency so that = and =Pm Pe Vcd w2 IV b b

9. Solve for at each speedcd

Additional Questions

1.

Discussion

1.

Week 8~ Procedures Create pit stop for cross country drive.