Pid_Reg3 - Texas Instruments TMS320C2000 User Manual

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Figure 15. Build Level II - Inverter Test and ADC Calibration
set_value
RC
MACRO
rmp_offset
trgt_value
eq. flag
Speed_Ref
watch window
DacPtr 1
Ta PWMDAC
MACRO
DacPtr 2
Tb
Tc DacPtr 3
Tb-Tc DacPtr 4
2.4.3 Closed Current Loop Operation - Build Level 3
Assuming the previous section is completed successfully, this section verifies the dq-axis current
regulation performed by PID_REG3 modules, QEP drv and speed measurement modules.
• Current regulator (PID modules) test and tuning: 3-phase motor control mainly consists of two main
control loops: a current loop and a speed loop. At this level, current control PIDs will be tested and
tuned if needed. After a successful tuning, the user should make sure that the feedback currents
precisely follow the Id and Iq current references. While testing the PIDs, the dc bus voltage should not
be too low; otherwise the outputs of the PID modules saturate which might introduce unwanted glitches
on the current waveforms or unstable operation. Once a stable set of PID coefficients is found, the
transient response of the PIDs should be examined by changing Iq and Id references (IqRef and IdRef
respectively). This has to be repeated for various load and speed conditions. Most of the time a single
set of coefficients does not perform well at all operating points; therefore an operating point dependent
PID coefficient look-up table may be used to improve performance.
• QEP drv test: Build 3 also implements the angular position sensor feedback path, based on the QEP
driver module which outputs both the mechanical and electrical angles. The optical position sensor and
QEP interface driver are operating correctly when, while the motor is spinning, variable theta_elec can
be viewed on the scope. Its output waveform should correspond in shape to the stimulus theta angle
generated by the RAMP_GEN module. This indicates that position information is being measured
correctly.
• Speed measurement module test: The speed measurement module, SPEED_FRQ, is in the
feedback path and can also be validated at this stage. The speed measurement is dependent on motor
shaft rotation, and the SPEED_FRQ module is driven from the theta_mech output of QEP module.
Since its output value should be constant, i.e. the motor is running at constant synchronous speed, the
calculated speed, speed_frq, can be viewed via a watch window instead of on the scope. The
RAMP_GEN frequency can be increased slowly up or down to check whether the speed measurement
varies appropriately.
• Calibration angle detection: In level 3, a simple calibration angle detection subroutine is added into
the code to measure the initial angle offset. This is necessary because the exact rotor position
information is needed for precise field orientation. The detected offset angle is basically the angle
between the locked rotor (zero) position and the position where the first index signal is received.
SPRUGI6 – September 2010
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watch window
rmp_freq
VdTesting
RG
IPARK
MACRO
MACRO
rmp_out
Theta
VqTesting
rmp_gain
park_D
PARK
MACRO
park_Q
DAC 1
DAC 2
DAC 3
DAC 4
C
R
Copyright © 2010, Texas Instruments Incorporated
Ta Mfunc_c1
Ipark_q Valpha
SVG
END
QMACRO Mfunc_c2
Tb
Ipark_d
Vbeta
Tc Mfunc_c3
park_d clarke_d
CLARKE
clarke_a
AdcRslt0
MACRO
theta
clarke_b
AdcRslt1
park_q clarke_q
DLOG
Dlog 1
MACRO
Ta
Dlog 2
Tb Dlog 3
Tc Dlog 4
TMS320C2000 Motor Control Primer
Software Tools
PWM1A
PWM1B 3-Phase
Inverter
PWM2A
PWM
EV
DRV
PWM2B
MACRO
HW
PWM3A
PWM3B
Ia
EV
ADC
Ib
DRV HW
Vdc
Motor
PMSM
19