BLDC(9)

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 pattern 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 alsoreverse 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 value is negative XOR rev 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 pattern 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 below 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.
Pattern | Phases, Source - Sink
 | 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