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 () of the AEV’s velocity () and the propeller speed (): sys f (v, RPM) Propulsion Efficiency: (, ) 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 (, ) can be reduced from two variables to one variable denoted by : sys f (v, RPM) f ( 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 for AEV: ~(0.15 - 0.40). A larger the value of 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 is, we need to determine what the function () 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?