| Abstract | A method and apparatus for multi-channel control of a multiple input,
multiple output, servo-driven plant utilizes finite impulse response (FIR)
filters to model the inverse of the plant. Each channel includes a servo
FIR filter that generates a servo command to drive the plant's servo
controller, a valve current FIR filter that bypasses the PID stage of the
servo controller to avoid undesirable effects of the PID loop, and a cross
FIR filter for each of the remaining channels that compensates for
physical coupling in the plant between the channels. The servo FIR filter
is calculated by an adaption routine that involves applying an
identification signal to the plant, applying the plant's response to the
filter and then updating the filter's coefficients using the error that
exists between the identification signal and the filter output. To reduce
the convergence time, the identification signal is separated into parts in
accordance with the amplitude spectral response of the plant and the parts
are applied sequentially. The valve current and cross FIR filters are
calculated using a forward drive adaption routine in which the
identification signal is applied to the filter and the filter output to
the plant. The forward drive adaption routine utilizes the phase response
of the plant which is provided by way of another FIR filter that includes
the inverse a plitude frequency response of the plant. Non-linear error
correction is provided via an error store that provides an error
correction that is added to the desired command. |
