Hindawi Publishing Corporation Mathematical Problems in Engineering Volume 2010, Article ID 123751, 12 pages doi:10.1155/2010/123751 Research Article Stabilizability and Disturbance Rejection with State-Derivative Feedback Manoel R. Moreira, Edson I. Mainardi J ´ unior, Talita T. Esteves, Marcelo C. M. Teixeira, Rodrigo Cardim, Edvaldo Assunc ¸˜ ao, and Fl ´ avio A. Faria Departamento de Engenharia El´ etrica, Faculdade de Engenharia de Ilha Solteira, Universidade Estadual Paulista (UNESP), 15385-000 Ilha Solteira, SP, Brazil Correspondence should be addressed to Marcelo C. M. Teixeira, marcelo@dee.feis.unesp.br Received 23 September 2010; Accepted 9 December 2010 Academic Editor: Fernando Lobo Pereira Copyright q 2010 Manoel R. Moreira et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In some practical problems, for instance in the control of mechanical systems using accelerometers as sensors, it is easier to obtain the state-derivative signals than the state signals. This paper shows that i linear time-invariant plants given by the state-space model matrices {A, B, C, D} with output equal to the state-derivative vector are not observable and can not be stabilizable by using an output feedback if detA 0 and ii the rejection of a constant disturbance added to the input of the aforementioned plants, considering detA /  0, and a static output feedback controller is not possible. The proposed results can be useful in the analysis and design of control systems with state-derivative feedback. 1. Introduction There exist many results in the literature on the feedback control of systems described through state variables 1. State feedback or output feedback is usually used, but in some cases the state-derivative feedback can be very useful to achieve a desired performance 2. In the last years, the state-derivative feedback of linear systems has been studied by some researchers. In 3, the authors proposed a formula similar to the Ackermann formula, for the pole-placement design with a state-derivative feedback gain. In 4, 5,a linear quadratic regulator LQR controller design scheme for standard state-space systems was presented. The procedure described in 6 allows the design of state-derivative feedback control systems using state feedback design methods. Other results about the pole placement of multivariable system, with state-derivative feedback, can be found in 7–13.