CANopen Programmer's Manual - Maccon.de

9: Cyclic Synchronous Modes CANopen Programmer’s Manual
Coordinated Motion
Interpolated position mode is used to control multiple coordinated axes or a single axis with the
need for time-interpolation of setpoint data. In interpolated position mode, the trajectory is
calculated by the CANopen master and passed to the amplifier’s interpolated position buffer as a
set of points. The amplifier reads the points from the buffer and performs linear or cubic
interpolation between them.
Copley Controls CANopen amplifiers support three interpolation sub-modes: linear interpolation
with constant time, linear interpolation with variable time, and cubic polynomial interpolation, which
is also known as position, velocity, and time (PVT) interpolation. The amplifier can switch between
linear and PVT interpolation on the fly.
Linear Interpolation with a Constant Time
In this mode, trajectory position points are assumed to be spaced at a fixed time interval. The
amplifier drives the axis smoothly between two points within the fixed time.
Linear Interpolation with Variable Time
In this linear interpolation mode, each trajectory segment can have a different time interval.
Cubic Polynomial (PVT) Interpolation
In PVT mode, the CANopen master describes the trajectory points as a position, velocity, and time
until the next point.
Given two such points, the amplifier can interpolate smoothly between them by calculating a cubic
polynomial function, and evaluating it repeatedly until the next point is encountered.
Cubic polynomial interpolation produces much smoother curves than linear interpolation. Thus it
can describe a complex profile with many fewer reference points. This allows a profile to be
compressed into a small number of reference points which can be sent over the CAN bus using
only a small amount of its total bandwidth.
Standard and Copley Custom Objects for Interpolated Position Mode
Copley Controls CANopen amplifiers provide two sets of objects for performing IP moves:
The CANopen DSP-402 profile standard IP move objects: 0x60C0, 0x60C1, and 0x60C2.
The Copley Controls alternative objects for PVT and linear interpolation with variable time:
0x 2010, 0x 2011, 0x 2012, and 0x 2013. These objects use bandwidth in a more efficient
manner, and feature an integrity counter to identify lost packets.
208 Copley Controls