On Thu, 21 Feb 2013, Klemen Dovrtel wrote:
Date: Thu, 21 Feb 2013 00:12:21 -0800 (PST)
From: Klemen Dovrtel <klemen_dovr...@yahoo.com>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: [Emc-users] hal - bldc - linear motor
Hello everybody,
I would like to control the linear ac motor using bldc hal component.?
1. I am not sure how should i set the:
bldc.N.scale s32 rw =?The number of encoder counts per rotor revolution.
bldc.N.poles s32 rw =?The number of motor poles. The encoder scale will be
divided by this value to determine the number of encoder counts per
electrical revolution
I attached motor schematics. So if I understand this correctly, the motor has
4 poles and the number of encoder counts per rotor revolution is
length_of_the_motor/encoder_resolution? The length_of_the_motor equals the
length of 4 magnetic poles?
Yes that sounds right
2. I am using the quadrature encoder with index signal for homing. I am
monitoring the encoder position using fpga that stores the position_value.
The position_value is set to 0 when fpga detects the index signal. I zero the
position value inside the fpga because the emc runs too slow to detect index
signal. So the problem is that this is somehow mixed quadrature and absolute
encoder. Is there a way to use the existing hal bldc component for homing my
motor. I can not use the "i Input type" because the emc should not offset the
encoder value and i can not use "a Input type" because i still have to home
the motor.
If the index is handled in the normal LinuxCNC way it should be OK, but
clearing the counter may cause problems as you dont want any change in
the raw-counts that are used for commutation while homing. I think most of the
LinuxCNC encoder counters (both the software and various hardware counters)
_latch_ the count at index rather than clearing the count for 2 reasons:
1. Not losing the raw counts value and 2. not messing up the velocity
estimation
Regards
Klemen
Peter Wallace
Mesa Electronics
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