Model reduction of linear time-varying systems with applications for   moving loads
  In this paper we consider different model reduction techniques for systems with moving loads. Due to the time-dependency of the input and output matrices, the application of time-varying projection matrices for the reduction offers new degrees of freedom, which also come along with some challenges. This paper deals with both simple methods for the reduction of particular linear time-varying systems, as well as with a more advanced technique considering the emerging time derivatives. 
Maria Cruz Varona and Boris Lohmann
math.DS cs.SY