Transcript Lab 6 AEV System Analysis 2

Advanced Energy Vehicle (AEV)
Lab 06: AEV System Analysis 2
AEV Project Objective
(Problem Definition)
INITIAL CONCEPTS
(Brainstorming)
EXPERIMENTAL RESEARCH
(Programming)
(System Analysis)
PT 1
PT 2
PT 3
PT 4
FINAL DESIGN
Present AEV Design
Learning Objectives
 Download data from the automatic control
system.
 Convert EEProm Arduino data readouts to
physical engineering parameters such as
distance traveled and velocity.
 Calculate the performance characteristics of the
AEV.
Recap – System Analysis 1
 In System Analysis 1, we downloaded data from the
automatic control system to calculate:
 Time
 Current
 Voltage
Input Power,
Incremental Energy,
Total Energy,
Pin  V  I
Pi  Pi 1
 ti 1  ti 
2
ET  sum( Ei )
Ei 
System Analysis 2
 Now we’re going to make use of the wheel counts recorded by
the AEV and compute the following:
s = distance (meters)
s  0.0124 * Marks
• Distance
s  si 1 
 i
t i  t i 1 
• Velocity
vi
• Kinetic Energy
KE 
1
mv 2
2
v = velocity (meters/seconds)
s = distance (meters)
t = time (seconds)
KE = Kinetic Energy (joules)
m = Mass (kilograms)
v = velocity(meters/second)
System Analysis 2:
AEV Performance Characteristics
 The system efficiency (denoted by  sys ) is composed of both
the propeller and the electric motor:
 sys   propeller &  motor
 The efficiency of the propulsion system is a function (𝑓) of the
AEV’s velocity (𝑣) and the propeller speed (𝑅𝑃𝑀):
sys  f (v, RPM)
Propulsion Efficiency: 𝑓(𝑣, 𝑅𝑃𝑀)
 AEV velocity can be easily computed.
 The propeller RPM is a function of the current being supplied
to the motor by the command inputs.
 The following are sample equations for RPM*:
RPM 3inch  64.59 I 2  1927.25 I  84.58
RPM 2.5inch  17.64 I 2  690.375I  99.77
*We will revisit the RPM curves in System Analysis 3 and update the equations above.
The Advance Ratio
 The function inputs (𝑣, 𝑅𝑃𝑀) can be reduced from two
variables to one variable denoted by 𝐽:
sys  f (v, RPM)  f ( J )
 𝐽 above is known as the Propeller Advance Ratio which is
given by:
RPM = Revolutions per Minute
v
J
v = velocity(meters/second)
( RPM 60)  D
D = Propeller Diameter (meters)
The Advance Ratio
 The advance ratio is used in Aerospace Engineering.
 It is the ratio of forward speed to the speed of the propeller.
• i.e., The distance traveled per revolution of the propeller.
 Typical range of 𝐽 for AEV: ~(0.15 - 0.40).
 A larger the value of 𝐽 can mean the vehicle is requiring little
work from the motor thus operating well with low input power.
Some Advance Ratio Limits
 At low motor speeds (~10% or lower) the propeller RPM
becomes difficult to measure. To filter out bad data,
constraints are used when computing the Advance Ratio.
 First, compute advance ratio: J 
 Second, apply constraints:
v
( RPM 60)  D
0 for J  0.15 with no power
J 
0.15 for J  0.15 with power
Propeller Efficiency
 Now that we’ve learned what 𝐽 is, we need to determine what
the function 𝑓(𝐽) is. This requires wind tunnel testing! (Next
weeks lab)
 For now, you are provided a sample propeller efficiency
equation*:
  1205J 3  1033J 2  179.4J  17.91
* We will revisit the propeller efficiency in System Analysis 3 and update the equation above.
Questions?