User Manual

Sinusoidal Commutation
Advanced Digital Motor Controller User Manual 123
FOC Testing and Troubleshooting
Verify that FOC is operating correctly by monitoring the following values with the PC
Utility:
FIGURE 8-27. FOC performance monitoring
Optimal performance is achieved when:
• FOC Quadrature Amps are close to 0.
• Motor Amps and FOC Torque Amps values are close.
• FOC Angle Correction is stable for stable motor Power (output voltage amplitude).
Check also when changing motor power how fast FOC Flux Amps is corrected to zero.
Tune FOC PI as necessary.
Unstable FOC correction is generally a sign of imperfections of the angle sensing (noise,
non-linearity, bad calibration, ...). Bad angle sensing causes the wrong values of Id and Iq
to be measured, which the FOC algorithm falsely attempts to correct, worsening the cur-
rent stability.
Field Weakening
Field weakening is a technique that is used to achieve faster motor rotation speed. This
is done by having some Flux (Id) current, even though this also introduces some waste.
Field Weakening is therefore possible on Roboteq controller by loading a non-zero set
point for the Flux current. This can be done from the console, the serial port, or from a Mi-
croBasic script with the command:
!GID ch Amps*10
The amount of Flux current should be different at low and high speed, typically starting
with zero, and increasing after a given RPM threshold is reached. Below is an example of
a MicroBasic script that changes the Flux set point according to such a rule
top:
Speed = abs(getvalue(_S, 1)) ‘ Read motor speed from Encoders
if (Speed > 5000) ‘ check if above 5000 RPM
FluxSetpoint = (Speed – 5000) / 100 ‘ 1A per 100 RPM above 5000
else
FluxSetpoint = 0 ‘ No Flux current below 5000 RPM
end if