User`s manual

CHAPTER 5.0 Functional Overview 5-45
CDS7324 (FORMERLY LSF-0819)
Rev. A INSTALLATION & USER’S MANUAL
The table below lists parameter or signals that can be monitored by the GUI, and can be useful during loop
tuning.
Field
Number
Name Type Units Comment
1096 current_d-axis_observer f32 Amps id
1097 current_q-axis_observer f32 Amps iq
1098 current_d-axis_demand f32 Amps idd
1099 current_q-axis_demand f32 Amps iqd
1104 current_phase_A_demand s16 Amps iad
1105 current_phase_B_demand s16 Amps ibd
1069 current_phase_A_feedback s16 see note 1 dspias
1070 current_phase_B_feedback s16 see note 1 dspibs
1287 current_loop_q-axis_error f32 Amps qcomp.error
1286 current_loop_d-axis_error f32 Amps dcomp.error
1298 current_loop_alpha_observer_error f32 Amps oacomp.error
1299 current_loop_beta_observer_error f32 Amps obcomp.error
1119 current_actual f32 Amps iqact
Table 5.32 List of Current Loop Signal Parameters
5.11.3.2 Motor Velocity Loop Sample Rate
The motor velocity loop sample period can be set to any multiple of the current loop sample period (~100us) using
the parameter motor_velocity_loop_rate_divider
(1144).
5.11.3.3 Motor Velocity feedback filter
A low-pass first order filter is also included on the motor feedback velocity. The motor feedback velocity is held in
the parameter motor_velocity_actual (1152), with the low-pass filtered velocity held in a parameter called
motor_velocity_filtered (1163). It is this filtered velocity variable that is used to limit the motor velocity.
The filter is a simple Euler approximation filter, characterised by two filter coefficients. The filter cut-off is specified
with a filter cut-off factor (FCF), held in a parameter called motor_velocity_filter_cutoff_factor
(1162). The two
filter coefficients (a
1
and b
0
) are computed in the embedded software each time the user writes to the cut-off factor
a
1
= 1 / (1 + 2*π* motor_velocity_filter_cutoff_factor);
b
0
= 2*π*motor_velocity_filter_cutoff_factor / (1 + 2*π* motor_velocity_filter_cutoff_factor);
Setting motor_velocity_filter_cutoff_factor to 0.5 sets the filter cut-off to half the motor velocity loop sample rate.
Hence, the default motor speed cut-off factor of 0.25 will set the filter cut-off to 625Hz, when the velocity sample
rate is 2.5KHz.
WARNING:- DANGER OF UNCONTROLLED MOTOR ACCELERATION
The DS2110 has specialised motor current compensation. For optimum performance the DS2110 operates a software
model of the current loop. The correct motor electrical parameters are required for this software model. Large errors in
the motor parameters can result in uncontrolled motion.
Small torque commands can result in a continuous motor acceleration. The velocity of the motor can increase in an
uncontrolled way if no counter-balancing torque is present. The user's control system should ensure that the speed of
the motor is monitored, and that a compensating torque command is applied to control the motor speed if necessary.