TMS320F28027F: Lab 9 Field Weakening ,How to turn off Field Weakening,and start speed control

the Lab 9 can run,but if I want to slow the Speed and turn off Field Weakening.the Speed is always at the Field Weakening Speed. Can not slow down.

what need i to do?

if I use below code before I clear the flag of Field Weakening,Speed can slow,but there will have overshoot of bus voltage.

FW_setOutput(fwHandle, _IQ(0.0));