This paper presents an efficient and systematic approach to designing a feedback controller and an observer for non-redundant linear multi-degrees of freedom mechanical systems including actuator dynamics. Taking into account the system symmetries, four block canonical forms are introduced. The submatrices of the block normal forms produce two matrix polynomials. Based on them, the pole placement method can be successfully applied to design both the state feed-back controller and the observer. To implement the controller and observer designed, symbolic computation is used.