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Experiment 1
• Begin thinking about Experiment 1 processWhat tests might you run to determinebattery/motor parameters?
Outer vs. Inner Rotor
• Traditional motors are inner rotor• On e bike, need hub to remain stationary and outer wheel to spin
Motor Teeth/Poles Example
Shaping Back EMF
• Earlier, assumed f( r) = sin( r) resulting insinusoidal back EMF
• Ways to achieve:1. Sinusoidal distribution of windings2. Altering slot/pole/phase
• #2 is used in our motor
0 5 10 15 20 25 30-8
-6
-4
-2
0
2
4
6
8
theta [deg]
Nor
mal
ized
Cou
pled
Flu
x [T
esla
*coi
l]
0 5 10 15 20 25 30-8
-6
-4
-2
0
2
4
6
8
theta [deg]
Nor
mal
ized
Cou
pled
Flu
x [T
esla
*coi
l]
• 33 Teeth, 22 Poles• Teeth/Pole/Phase = 0.5
• 36 Teeth, 22 Poles• Teeth/Pole/Phase = 0.5455
ABC
S N
stator
rotor
Shape of Back EMF
Motor Driver: Trapezoidal Control
Torque Ripple
Example Front Wheel Hub Motor
E bike hub (stator) Single phase wound per tooth
56 pole63 teeth
Stator Winding
Complete winding of Phase A Complete winding of all phases
Rotor and Poles
• Outer rotor (to which spokes/wheel areattached)
• Magnets alternate N S
Experiment 2
• Experiment 3 will build synchronous boostconverter
• To operate open loop, need gate drive signals• Experiment 2: brief introduction to MSPprogramming – Generate voltage controlledPWM signals
Microprocessor: MSP430 Launchpad
• MSP430 microprocessorsfrom Texas Instruments
• Programmable in C or ASM• Ultra low power (not afocus here)
• On board USB bootloader• Two LEDs, one switch• Two timers, one 5 channel 10 bit ADC• System clock up to 16 MHz
High Resolution PWM
MSP430G2553:• 16 MHz clock
Max PWM resolution is 62.5ns
MSP430F2172:• PWM 16x clock multiplier
Max PWM resolution is 4ns• Final decision TBD; same programmingapproach applies in either case
Notes on Launchpad• P1.1 and P1.2 are used as part of the digitalcommunication for the debugger
• P1.0 and P1.6 can be tied to on board LEDs forvisual debugging
• Do not apply power to Vcc; it is generated onboard
• Launchpad does not break out all pins on MSPUser guide lists all functionality in familyMake sure to take note of what your chip can do
• Documentation contains both assembly and Ccode
MSP430 Documentation
• User’s Guidehttp://www.ti.com/lit/ug/slau144j/slau144j.pdf
• Datasheethttp://www.ti.com/lit/ds/symlink/msp430g2553.pdf
• Erratahttp://www.ti.com/lit/er/slaz440g/slaz440g.pdf
Example Today
• General Purpose I/O• System Clock• TimerA• Interrupts
MSP430 Internal Block Diagram
Pin Assignments
Digital I/O Registers
Clock Module
Clock Registers (1/2)
Clock Registers (2/2)
Timer A Block Diagram
Timer A Operation – Up/Down Mode
Timer A Registers (1/2)
Timer A Registers (2/2)
Interrupts
