@TechReport{	  it:2005-009,
  author	= {Claes Olsson},
  title		= {Disturbance Observer-Based Automotive Engine Vibration
		  Isolation Dealing with Non-Linear Dynamics and Transient
		  Excitation},
  institution	= {Department of Information Technology, Uppsala University},
  department	= {Division of Systems and Control},
  year		= {2005},
  number	= {2005-009},
  month		= apr,
  abstract	= {Active automotive engine vibration isolation is considered
		  where both stationary and transient engine-induced
		  excitations as well as plant non-linearity are considered.
		  
		  The adopted control strategy targets the dominating
		  spectral components of the excitation and achieves narrow
		  band vibration isolation using feedback of disturbance
		  states estimates. Time-varying gain-scheduled observer
		  design, including investigations of closed-loop
		  characteristics, is based on a linear parameter varying
		  (LPV) approximation of the considered non-linear engine and
		  subframe suspension system. To generate this
		  representation, an approach of dividing the non-linear
		  system into its linear and non-linear components where the
		  latter is represented using a parameter dependent
		  non-linear function is proposed. Parameter dependent
		  quadratic stability analysis has been made tractable using
		  an affine closed-loop system representation.
		  
		  High vibration isolation performance is demonstrated using
		  co-simulations incorporating a detailed non-linear plant
		  model and measured engine excitations. This is also
		  achieved for engine operating conditions corresponding to
		  rapid car accelerations, whereas the system exhibits
		  non-linear characteristics and the fundamental frequency of
		  the harmonic disturbance undergoes rapid time variations.
		  Parameter dependent closed-loop quadratic stability is
		  being shown assuming plant linearity. Yet, in the
		  non-linear plant case, stability is guaranteed but only for
		  limited intervals of the parameters and their time
		  derivatives.}
}