1. InstaSPIN-FOC Code Functionality
Navigating through the InstaSPIN-FOC Code
Rev. 0.2
continue
Dave Wilson

4. PI Series Form

5. PI Parallel Form

6. Amplitude Invariant Forward Clarke Transform
CLARKE_run( ) 2 + -
1/3 A
alpha + B + -
beta C
Amplitude Invariant Forward Clarke Transform
numSensors = 3

107. Amplitude Invariant Forward Clarke Transform
CLARKE_run() 2 + -
1/3 A
alpha + B + -
beta C
Amplitude Invariant Forward Clarke Transform
numSensors = 3

109. Inverse Park Transform
IPARK_run( ) Vd + -
Valpha
Cos +
Vbeta Vq
angle
Sin
Inverse Park Transform

110. Vd Vq
Valpha
Vbeta

111. 2 2
Vq_max = Vbus - Vd

113. Inverse Clarke Transform

114. Vmax Vcom Vmin pT -> value[0] pT -> value[1] pT -> value[2]
This SVM technique is nice for overmodulation, as the clipping occurs naturally when the gain is increased.

115. Angle Compensation
PROBLEM: The output voltages from the FOC algorithm are calculated assuming a specific angle of the rotor flux. When the PWM values are placed into the PWM registers, they don’t affect the PWM pins until the next PWM cycle due to the double-buffered nature of the PWM module. By this time, the rotor flux angle has changed by an amount that is directly proportional to the speed of the flux vector rotation and inversely proportional to the PWM frequency. As a result, the applied voltages are incorrect in relation to the new rotor flux angle.
SOLUTION: Based on the PWM frequency and speed at the time that the voltages are calculated, predict what the angle will be when the calculated voltages will appear on the motor windings. Then use this angle prediction for the inverse Park transform.
I_Park_angle = calculated_angle + electrical speed * PWM period * compensation_factor
If the sampling frequency is equal to the PWM frequency, then the compensation_factor is equal to However, the compensation_factor changes as the relationship between PWM frequency and sampling frequency changes (next slide…)

116. Compensation Factor changes as a function of
USER_NUM_PWM_TICKS_PER_ISR_TICK
The Compensation factor is the number of PWM periods (T) from when the ADC samples used to calculate a given angle are acquired until the average time that the PWM values resulting from that angle calculation appear on the motor windings.
Example 1
PWM Ticks / ISR Ticks = 1 q1 q2 q3 q4 q5 q6 q7 q8 q9
q10
q11
q12
Compensation Factor = 1.5
PWM Values V1 V2 V3 V4 V5 V6 V7 V8 V9
V10
V11
V12
Example 2
PWM Ticks / ISR Ticks = 3 q1 q2 q3 q4 q5 q6
Compensation Factor = 2.5
PWM Values V1 V2 V3 V4 V5 V6 T
T = PWM period
Compensated angle = Uncompensated angle + speed * T * Compensation Factor

126. Page 1

132. Thank You!
…for using
InstaSPIN-FOC