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NAME
bldc - BLDC and AC-servo control component
SYNOPSIS
loadrt bldc cfg=qi6,aH
DESCRIPTION
This component is designed as an interface between the most common forms of three-phase
motor feedback devices and the corresponding types of drive. However there is no
requirement that the motor and drive should necessarily be of inherently compatible types.
Each instance of the component is defined by a group of letters describing the input and
output types. A comma separates individual instances of the component. For example loadrt
bldc cfg=qi6,aH
Tags
Input type definitions are all lower-case.
n No motor feedback. This mode could be used to drive AC induction motors, but is also
potentially useful for creating free-running motor simulators for drive testing.
h Hall sensor input. Brushless DC motors (electronically commutated permanent magnet
3-phase motors) typically use a set of three Hall sensors to measure the angular position
of the rotor. A lower-case h in the cfg string indicates that these should be used.
a Absolute encoder input. (Also possibly used by some forms of Resolver conversion
hardware). The presence of this tag over-rides all other inputs. Note that the component
still requires to be be connected to the rawcounts encoder pin to prevent loss of
commutation on index-reset.
q Incremental (quadrature) encoder input. If this input is used then the rotor will need
to be homed before the motor can be run.
i Use the index of an incremental encoder as a home reference.
f Use a 4-bit Gray-scale patttern to determine rotor alignment. This scheme is only used
on the Fanuc "Red Cap" motors. This mode could be used to control one of these motors
using a non-Fanuc drive.
Output type descriptions are all upper-case.
Defaults The component will always calculate rotor angle, phase angle and the absolute
value of the input value for interfacing with drives such as the Mesa 8i20. It will also
default to three individual, bipolar phase output values if no other output type modifiers
are used.
B Bit level outputs. Either 3 or 6 logic-level outputs indicating which high or low gate
drivers on an external drive should be used.
6 Create 6 rather than the default 3 outputs. In the case of numeric value outputs these
are separate positive and negative drive amplitudes. Both have positive magnitude.
H Emulated Hall sensor output. This mode can be used to control a drive which expects 3x
Hall signals, or to convert between a motor with one hall pattern and a drive which
expects a different one.
F Emulated Fanuc Red Cap Gray-code encoder output. This mode might be used to drive a non-
Fanuc motor using a Fanuc drive intended for the "Red-Cap" motors.
T Force Trapezoidal mode.
OPERATING MODES
The component can control a drive in either Trapezoidal or Sinusoidal mode, but will
always default to sinusoidal if the input and output modes allow it. This can be over-
ridden by the T tag. Sinusoidal commutation is significantly smoother (trapezoidal
commutation induces 13% torque ripple).
ROTOR HOMING.
To use an encoder for commutation a reference 0-degrees point must be found. The
component uses the convention that motor zero is the point that an unloaded motor aligns
to with a positive voltage on the A (or U) terminal and the B & C (or V and W) terminals
connected together and to -ve voltage. There will be two such positions on a 4-pole motor,
3 on a 6-pole and so on. They are all functionally equivalent as far as driving the motor
is concerned. If the motor has Hall sensors then the motor can be started in trapezoidal
commutation mode, and will switch to sinusoidal commutation when an alignment is found. If
the mode is qh then the first Hall state-transition will be used. If the mode is qhi then
the encoder index will be used. This gives a more accurate homing position if the distance
in encoder counts between motor zero and encoder index is known. To force homing to the
Hall edges instead simply omit the i.
Motors without Hall sensors may be homed in synchronous/direct mode. The better of these
options is to home to the encoder zero using the iq config parameter. When the init pin
goes high the motor will rotate (in a direction determined by the rev pin) until the
encoder indicates an index-latch (the servo thread runs too slowly to rely on detecting an
encoder index directly). If there is no encoder index or its location relative to motor
zero can not be found, then an alternative is to use magnetic homing using the q config.
In this mode the motor will go through an alignment sequence ending at motor zero when the
init pin goes high It will then set the final position as motor zero. Unfortunately the
motor is rather springy in this mode and so alignment is likely to be fairly sensitive to
load.
FUNCTIONS
bldc.N (requires a floating-point thread)
PINS
bldc.N.hall1 bit in [if personality & 0x01]
Hall sensor signal 1
bldc.N.hall2 bit in [if personality & 0x01]
Hall sensor signal 2
bldc.N.hall3 bit in [if personality & 0x01]
Hall sensor signal 3
bldc.N.hall-error bit out [if personality & 0x01]
Indicates that the selected hall pattern gives inconsistent rotor position data.
This can be due to the pattern being wrong for the motor, or one or more sensors
being unconnected or broken. A consistent pattern is not neceesarily valid, but an
inconsistent one can never be valid.
bldc.N.C1 bit in [if ( personality & 0x10 )]
Fanuc Gray-code bit 0 input
bldc.N.C2 bit in [if ( personality & 0x10 )]
Fanuc Gray-code bit 1 input
bldc.N.C4 bit in [if ( personality & 0x10 )]
Fanuc Gray-code bit 2 input
bldc.N.C8 bit in [if ( personality & 0x10 )]
Fanuc Gray-code bit 3 input
bldc.N.value float in
PWM master amplitude input
bldc.N.lead-angle float in [if personality & 0x06] (default: 90)
The phase lead between the electrical vector and the rotor position in degrees
bldc.N.rev bit in
Set this pin true to reverse the motor. Negative PWM amplitudes will also reverse
the motor and there will generally be a Hall pattern that runs the motor in each
direction too.
bldc.N.frequency float in [if ( personality & 0x0F ) == 0]
Frequency input for motors with no feedback at all, or those with only an index
(which is ignored)
bldc.N.initvalue float in [if personality & 0x04] (default: 0.2)
The current to be used for the homing sequence in applications where an incremental
encoder is used with no hall-sensor feedback
bldc.N.rawcounts s32 in [if personality & 0x06] (default: 0)
Encoder counts input. This must be linked to the encoder rawcounts pin or encoder
index resets will cause the motor commutation to fail
bldc.N.index-enable bit io [if personality & 0x08]
This pin should be connected to the associated encoder index-enable pin to zero the
encoder when it passes index This is only used indicate to the bldc control
component that an index has been seen
bldc.N.init bit in [if ( personality & 0x05 ) == 4]
A rising edge on this pin starts the motor alignment sequence. This pin should be
connected in such a way that the motors re-align any time that encoder monitoring
has been interrupted. Typically this will only be at machine power-off. The
alignment process involves powering the motor phases in such a way as to put the
motor in a known position. The encoder counts are then stored in the offset
parameter. The alignment process will tend to cause a following error if it is
triggered while the axis is enabled, so should be set before the matching
axis.N.enable pin. The complementary init-done pin can be used to handle the
required sequencing.
Both pins can be ignored if the encoder offset is known explicitly, such as is the
case with an absolute encoder. In that case the offset parameter can be set
directly in the HAL file
bldc.N.init-done bit out [if ( personality & 0x05 ) == 4] (default: 0)
Indicates homing sequence complete
bldc.N.A-value float out [if ( personality & 0xF00 ) == 0]
Output amplitude for phase A
bldc.N.B-value float out [if ( personality & 0xF00 ) == 0]
Output amplitude for phase B
bldc.N.C-value float out [if ( personality & 0xF00 ) == 0]
Output amplitude for phase C
bldc.N.A-on bit out [if ( personality & 0xF00 ) == 0x100]
Output bit for phase A
bldc.N.B-on bit out [if ( personality & 0xF00 ) == 0x100]
Output bit for phase B
bldc.N.C-on bit out [if ( personality & 0xF00 ) == 0x100]
Output bit for phase C
bldc.N.A-high float out [if ( personality & 0xF00 ) == 0x200]
High-side driver for phase A
bldc.N.B-high float out [if ( personality & 0xF00 ) == 0x200]
High-side driver for phase B
bldc.N.C-high float out [if ( personality & 0xF00 ) == 0x200]
High-side driver for phase C
bldc.N.A-low float out [if ( personality & 0xF00 ) == 0x200]
Low-side driver for phase A
bldc.N.B-low float out [if ( personality & 0xF00 ) == 0x200]
Low-side driver for phase B
bldc.N.C-low float out [if ( personality & 0xF00 ) == 0x200]
Low-side driver for phase C
bldc.N.A-high-on bit out [if ( personality & 0xF00 ) == 0x300]
High-side driver for phase A
bldc.N.B-high-on bit out [if ( personality & 0xF00 ) == 0x300]
High-side driver for phase B
bldc.N.C-high-on bit out [if ( personality & 0xF00 ) == 0x300]
High-side driver for phase C
bldc.N.A-low-on bit out [if ( personality & 0xF00 ) == 0x300]
Low-side driver for phase A
bldc.N.B-low-on bit out [if ( personality & 0xF00 ) == 0x300]
Low-side driver for phase B
bldc.N.C-low-on bit out [if ( personality & 0xF00 ) == 0x300]
Low-side driver for phase C
bldc.N.hall1-out bit out [if ( personality & 0x400 )]
Hall 1 output
bldc.N.hall2-out bit out [if ( personality & 0x400 )]
Hall 2 output
bldc.N.hall3-out bit out [if ( personality & 0x400 )]
Hall 3 output
bldc.N.C1-out bit out [if ( personality & 0x800 )]
Fanuc Gray-code bit 0 output
bldc.N.C2-out bit out [if ( personality & 0x800 )]
Fanuc Gray-code bit 1 output
bldc.N.C4-out bit out [if ( personality & 0x800 )]
Fanuc Gray-code bit 2 output
bldc.N.C8-out bit out [if ( personality & 0x800 )]
Fanuc Gray-code bit 3 output
bldc.N.phase-angle float out (default: 0)
Phase angle including lead/lag angle after encoder zeroing etc. Useful for
angle/current drives. This value has a range of 0 to 1 and measures electrical
revolutions. It will have two zeros for a 4 pole motor, three for a 6-pole etc
bldc.N.rotor-angle float out (default: 0)
Rotor angle after encoder zeroing etc. Useful for angle/current drives which add
their own phase offset such as the 8i20. This value has a range of 0 to 1 and
measures electrical revolutions. It will have two zeros for a 4 pole motor, three
for a 6-pole etc
bldc.N.out float out
Current output, including the effect of the dir pin and the alignment sequence
bldc.N.out-dir bit out
Direction output, high if /fBvalue/fR is negative XOR /fBrev/fR is true.
bldc.N.out-abs float out
Absolute value of the input value
PARAMETERS
bldc.N.in-type s32 r (default: -1)
state machine output, will probably hide after debug
bldc.N.out-type s32 r (default: -1)
state machine output, will probably hide after debug
bldc.N.scale s32 rw [if personality & 0x06] (default: 512)
The number of encoder counts per rotor revolution.
bldc.N.poles s32 rw [if personality & 0x06] (default: 4)
The number of motor poles. The encoder scale will be divided by this value to
determine the number of encoder counts per electrical revolution
bldc.N.encoder-offset s32 rw [if personality & 0x0A] (default: 0)
The offset, in encoder counts, between the motor electrical zero and the encoder
zero modulo the number of counts per electrical revolution
bldc.N.offset-measured s32 r [if personality & 0x04] (default: 0)
The encoder offset measured by the homing sequence (in certain modes)
bldc.N.drive-offset float rw (default: 0)
The angle, in degrees, applied to the commanded angle by the drive in degrees. This
value is only used during the homing sequence of drives with incremental encoder
feedback. It is used to back-calculate from commanded angle to actual phase angle.
It is only relevant to drives which expect rotor-angle input rather than phase-
angle demand. Should be 0 for most drives.
bldc.N.output-pattern u32 rw [if personality & 0x400] (default: 25)
Commutation pattern to be output in Hall Signal translation mode. See the
description of /fBpattern/fR for details
bldc.N.pattern u32 rw [if personality & 0x01] (default: 25)
Commutation pattern to use, from 0 to 47. Default is type 25. Every plausible
combination is included. The table shows the excitation pattern along the top, and
the pattern code on the left hand side. The table entries are the hall patterns in
H1, H2, H3 order. Common patterns are: 0 (30 degree commutation) and 26, its
reverse. 17 (120 degree). 18 (alternate 60 degree). 21 (300 degree, Bodine). 22
(240 degree). 25 (60 degree commutation).
Note that a number of incorrect commutations will have non-zero net torque which
might look as if they work, but don't really.
If your motor lacks documentation it might be worth trying every pattern.
┌────────────────────────────────────────┐
│ Phases, Source - Sink │
├────┬───────────────────────────────────┤
│pat │ B-A C-A C-B A-B A-C B-C │
├────┼───────────────────────────────────┤
│ 0 │ 000 001 011 111 110 100 │
│ 1 │ 001 000 010 110 111 101 │
│ 2 │ 000 010 011 111 101 100 │
│ 3 │ 001 011 010 110 100 101 │
│ 4 │ 010 011 001 101 100 110 │
│ 5 │ 011 010 000 100 101 111 │
│ 6 │ 010 000 001 101 111 110 │
│ 7 │ 011 001 000 100 110 111 │
│ 8 │ 000 001 101 111 110 010 │
│ 9 │ 001 000 100 110 111 011 │
│10 │ 000 010 110 111 101 001 │
│11 │ 001 011 111 110 100 000 │
│12 │ 010 011 111 101 100 000 │
│13 │ 011 010 110 100 101 001 │
│14 │ 010 000 100 101 111 011 │
│15 │ 011 001 101 100 110 010 │
│16 │ 000 100 101 111 011 010 │
│17 │ 001 101 100 110 010 011 │
│18 │ 000 100 110 111 011 001 │
│19 │ 001 101 111 110 010 000 │
│20 │ 010 110 111 101 001 000 │
│21 │ 011 111 110 100 000 001 │
│22 │ 010 110 100 101 001 011 │
│23 │ 011 111 101 100 000 010 │
│24 │ 100 101 111 011 010 000 │
│25 │ 101 100 110 010 011 001 │
│26 │ 100 110 111 011 001 000 │
│27 │ 101 111 110 010 000 001 │
│28 │ 110 111 101 001 000 010 │
│29 │ 111 110 100 000 001 011 │
│30 │ 110 100 101 001 011 010 │
│31 │ 111 101 100 000 010 011 │
│32 │ 100 101 001 011 010 110 │
│33 │ 101 100 000 010 011 111 │
│34 │ 100 110 010 011 001 101 │
│35 │ 101 111 011 010 000 100 │
│36 │ 110 111 011 001 000 100 │
│37 │ 111 110 010 000 001 101 │
│38 │ 110 100 000 001 011 111 │
│39 │ 111 101 001 000 010 110 │
│40 │ 100 000 001 011 111 110 │
│41 │ 101 001 000 010 110 111 │
│42 │ 100 000 010 011 111 101 │
│43 │ 101 001 011 010 110 100 │
│44 │ 110 010 011 001 101 100 │
│45 │ 111 011 010 000 100 101 │
│46 │ 110 010 000 001 101 111 │
│47 │ 111 011 001 000 100 110 │
└────┴───────────────────────────────────┘
AUTHOR
Andy Pugh
LICENSE
GPL