Delta Tau PMAC2 PCI Manual de usuario descargar pdf (Pagina 31)

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PMAC2 User Manual

Setting Up PMAC2 for Direct PWM Control 23

For commutation with digital current loops, the proper setting of Ix72 is unrelated to the polarity of the

encoder counter. This is different from commutation with an analog current loops, in which the polarity

of Ix72 (less than or greater than 128) must match the encoder counter polarity. With the digital current

loop, the polarity of the encoder counter must be set for proper servo operation; with the analog current

loop, once the Ix72 polarity match has been made for commutation, the servo loop polarity match is

guaranteed.

Commutation Feedback Address: Ix83

Ix83 specifies the address of the register used for the commutation position feedback. Usually, this is the

address of the encoder phase position register for Channel n in PMAC2’s gate array IC, where n=x. This

address is the default value for Ix83. Usually the values used are:

Note:

When commutating across the MACRO ring with Type 0 protocol, the number of

counts per revolution must be multiplied by 256 before setting Ix70 and Ix71.

When commutating across the MACRO ring with Type 1 protocol, the number of

counts per revolution must be multiplied by 32 before setting Ix70 and Ix71.

Chan # 1 2 3 4 5 6 7 8

Hex

$C001 $C009 $C011 $C019 $C021 $C029 $C031 $C039

When performing direct PWM control over the MACRO ring, Ix83 points to the position feedback

used are dependent on whether MACRO Type 0 or Type 1 protocol is employed for the node:

Node # 0 1 4 5 8 9 12 13

Type 0

$8C0A3 $8C0A7 $8C0AB $8C0AF $8C0B3 $8C0B7 $8C0BB $8C0BF

Type 1

$8C0A0 $8C0A4 $8C0A8 $8C0AC $8C0B0 $8C0B4 $8C0B8 $8C0BC

Using Direct PWM for Brush Motor Control

It is possible to use PMAC2’s direct PWM and digital current loop for control of DC brush motors, both

those with permanent-magnet fields, and those with wound fields. Because PMAC2’s digital current loop

and commutation algorithms are combined, it is still necessary to activate PMAC2’s commutation

algorithm for the motor, even though it is not really commutating the motor.

The sine-wave commutation is effectively disabled in this technique by telling PMAC2 that the motor has

a commutation cycle of 1 count. Each count received causes a 360

e phase increment, leaving the phase

angle constant at all times for DC control. With the phase angle always at zero, PMAC2’s quadrature, or

torque-producing, output voltage and feedback current are always equivalent to the motor’s rotor, or

armature, voltage and current. PMAC2’s direct, or magnetization field, voltage and current are always

equivalent to the motor’s stator, or wound field, voltage and current (if any).

Hardware Connection

In this technique, the rotor (armature) current is commanded by PMAC2 phases A and C. The motor

armature leads should be connected between the two half-bridges of the amplifier driven by PMAC2

phases A and C, together forming a full H-bridge.

The armature current sensor should feed an A/D converter that is connected to one of the serial ADC

inputs for the channel on PMAC2. If there is a wound field, the armature current reading must be fed into

ADC A, and the field current reading must be fed into ADC B.

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Delta Tau PMAC2 PCI Manual de usuario Pagina 31

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