Partial internal control recovery on 1-D Klein-Gordon systems

In this exposition,a technique to recover internal control on a distributed parameter system is reported. the system is described by 1-d klein- gordon partial differential equation with a time-varying parameter. we would like to recover the internal control applied to the system if we know some limited information about the output. we use a method called sentinel method to recover the internal control. it involves some construction of a linear functional,and we show that this construction relates closely to the exact controllability problem.