CDHD Operat ion
User Manual 183
4 . Set the desired bandwidth. It is recommended to begin with a low value
(1 0 Hz), and gradually increase it .
5 . Set the load inertia ratio to zero: LM JR 0 .
The load inertia value LMJR is expressed as a percentage of the rotor inertia.
The range for LMJR is 0 t o 10,000. I t represents a range of load: rot or
inertia ratios ranging from 0: 1 to 100:1. For example, to set a 10: 1 ratio
between the load inertia and the motor inertia, use the com mand LMJR
1000. At this point the step response should have the maximum overshoot ,
but the control loop should be stable (low gains).
6 . Activate the recording mechanism to record t he velocity comm and, the
current com m and, and the actual (feedback) velocity:
RECORD 1 1 0 2 4 “VCMD I CMD V
7 . Jog the motor at a constant low speed: J [ v a lu e 1 ]
For example, start with the command J 1 5 0
8 . Activat e the recording trigger: RECTRI G VCMD [ v a lu e 2 ] 2 0 1 .
value2 should be greater than value1 in the previous step; for exam ple:
RECTRIG VCMD 200 20 1.
9 . Jog the motor at a value higher than specified in the RECTRI G command.
This is actually the step comm and. The higher the step, the better the
results. The step should not be less than 300 (rpm) . For example: J 5 0 0 .
1 0 . The recording takes about half a second. After this period, reduce the m otor
speed.
1 1 . Verify that the recording process is term inated: RECD ON E
1 2 . Display the recorded data by dumping to the serial port: GET
1 3 . Analyze the results.
If the current comm and is saturated (gets absolute values of ILIM) during
the process, reduce the step or reduce the bandwidth, and return to Step 6.
1 4 . I nspect the feedback velocity:
I f t here is an undershoot or oscillations, reduce LMJR t o t he mean
value of the present LMJR and the last LMJR which had an overshoot,
and return to step 6.
I f there is an overshoot, increase LMJR by 100, and return to Step 6.
Repeat the process until the overshoot is reduced to a m inimum
(The estim at ed load inertia m ay be queried by LMJR.)
8 .5 Position Ope ra tion
8 .5 .1 Ser ial Posit ioning Oper at ion M ode
The CDHD has a dedicat ed mode of operation (
OPMODE 8) for sim ple positioning
applications over the serial port. Serial comm ands are transm itted from a host
com puter through the serial port. The comm and specifies the target position and
the cruise velocity, while additional m otion profile inform ation (such as
acceleration, deceleration and profile type) is set up using explicit variables.
In the ServoStudio Motion task screen, select Oper at ion Mode 8 –
Posit ion ing to modify and test parameters.
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