User guide Owner's manual

User manual for the ZEN 3-channel X-LMS controller Soft dB inc.
3.0 Detailed Control Algorithm
The control algorithm running on the DSP board is an X-LMS feed-forward algorithm
with filtered reference. The X-LMS optimization is done in real time for an optimization
frequency that is selectable between 78.125 Hz and 78.125 kHz. The main sampling
frequency is fixed at 78.125 kHz and the user can adjust the optimization rate by
specifying a decimation factor.
When the controller is used in coupled mode, the secondary cross-paths (see section 3.2
for details) are taken into account during LMS optimization. In uncoupled mode, the
control system acts like three separate mono-channel controllers.
The maximum number of coefficients for the control filters depends on many factors: the
optimization frequency, the number of channels and the number of coefficients for the
control path filters. For example, a 3-channel case with an optimization frequency of
15.6 kHz (main frequency at 78.125 kHz and decimation factor of 5), the controller can
optimize up to 256 coefficients in coupled mode. In uncoupled mode, 909 coefficients
can be optimized in real time. In both cases, the number of coefficients for primary and
secondary control paths is 400.
The next sections describe in-detail the control algorithm running on the DSP board.
Coupled and uncoupled modes will be explained. Then, the technique used to identify the
primary and secondary control paths will be presented.
3.1 Uncoupled Algorithm Description
3.1.1 General Description
Figure 5 shows a schematic of the algorithm for the uncoupled case.
ZEN User Manual p. 9