Copley Controls XEL-230-18, User Manual

Page: 17 / 167

Xenus Plus User Guide 16-01344 Rev 06
Copley Controls 17
2.2: Operating Modes
2.2.1: Commutation Modes
The drive supports three commutation modes to drive brush and brushless motors: brushless
sinusoidal, brushless trapezoidal, and DC brush.
Brushless motors driven with sinusoidal phase currents are commonly called AC brushless, while
those which commutate using only Hall feedback are called DC brushless motors. In DC brushless
motors, only two phases are driven at a time and the current between them is controlled to be DC.
AC brushless motors drive all three phases, each with sinusoidal currents and 120 degrees of phase
shift between them. In most applications, sinusoidal commutation is preferred over trapezoidal,
because it reduces torque ripple and offers the smoothest motion at any velocity or torque. In the
sinusoidal commutation mode, an encoder or a resolver are required for all modes of operation.
When driving a DC brush motor, the drive operates as a traditional H-Bridge drive using
only the U & V PWM outputs.
2.2.2: Position Feedback Types
Encoder and Resolver Support
The standard versions of the Xenus Plus drives support digital quadrature encoders, analog Sin/Cos
encoders, and a variety of serial and absolute encoder formats.
Resolver version
s, designated by “–R” in the model number, support standard, single speed,
transmit-type resolvers.
Digital quadrature and Sin/Cos
analog encoders are “incremental” types that typically use Hall
feedback for commutating brushless motors. Resolvers and absolute rotary encoders do not require
Halls for commutation because they provide the absolute feedback of the position of the motor rotor.
Multi-Mode Port
All versions support a multi-mode port. This interface can be configured to:
•
Provide a buffered digital encoder output based on the digital quadrature encoder input.
•
Provide a quadrature emulated output based on the analog encoder or resolver input.
•
Provide a quadrature emulated output from a serial encoder.
•
Provide a second digital encoder input to be used in the dual encoder position mode.
In this mode, an encoder attached to the load provides position loop feedback, and the
motor encoder or resolver provides velocity loop feedback.
2.2.3: Control Modes and Loops
Nesting of Control Loops and Modes
Copley Controls drives use up to three nested control loops - current, velocity, and position - to
control a motor in three associated operating modes.
Control Loops Illustration
In position mode, the drive uses all three loops. As shown below, the position loop drives the nested
velocity loop, which drives the nested current loop. In velocity mode, the velocity loop drives the
current loop. In current mode, the current loop is driven directly by external or internal current
commands.