User Manual

Table Of Contents
Field Oriented Control (FOC) mode Operation
Advanced Digital Motor Controller User Manual 133
Rs
Stator
Resistance
Lls
Stator
Leakage
Inductance
Rr
Rotor
Resistance
Llr
Rotor
Leakage
Inductance
Lm
Mutual
Inductance
These parameters include per phase rotor resistance ‘Rr’, rotor leakage inductance ‘Llr,
mutual inductance ‘Lm’ and rotor leakage inductance ‘Llr. Usually, motor manufacturer will
provide you an equivalent circuit of the induction motor that contains Rr, Rs, Lm, Llr, Lls
In FOC, therefore, rotor flux and motor torque can be individually controlled regardless
of load and speed. FOC offers better dynamic performance, accurate current control and
ensures maximum efficiency, unlike traditional scalar control methods such as Open Loop
VpH and Constant Slip Control.
Under FOC operation, AC induction motors can be run in either FOC torque mode or FOC
speed mode. FOC torque mode allows users to command a torque to a motor in terms of
Amps. While FOC speed will regulate the speed at the command/desired value.
Configuring FOC Torque Mode
To configure FOC mode, first set the controller in Open Loop (Volts per Hertz) mode as
described in one of the previous sections. Verify that the motor is spinning in the desired
direction and that encoder is working and is counting with the correct polarity. See Testing
the Encoder section above.
Once the encoder is verified to work and the motor spins in the open loop, follow these
steps. Using the Roborun PC utility:
Enter the motor parameters under the section “Motor Parameters” in RoboRun
configuration. Usually, motor manufacturer will provide you an equivalent circuit of the
induction motor that contains Rr, Rs, Lm, Llr, Lls.
Set the Flux Amps. In order to find the optimal flux amps, run the motor in Volts per
Hertz (VpH) mode with small/no load using the motor’s rated VpH ratio. Then watch the
flux amps in the PC utility. Enter this value in the configuration. This flux amps can be
increased for low speed/high torque requirement and can be decreased (Field Weaken-
ing) for high speed/ low torque requirement.
Set the operating mode to FOC torque. Set Amps limit according to the applications
need but do not exceed the motor specifications.
Save the settings to the controller.
Next step is to tune FOC (Flux and Torque) PID. Start with low proportional gain e.g.
0.1, and then set some Integral gain. Integral gain is more important in this case.
Alternatively use the method as described in chapter “FOC Gains Tuning” in Section 8,
using the Stator Resistance (Rs) and the Stator Inductance (Ls).