In order to improve the accuracy in motion control of mechanical systems based on experimentally identified relations between inputs and outputs at a finite number of discretely specified points in the state space (each point is called a lattice point), this paper proposes two identification methods of the parameters describing the input and output relations at every lattice point : the state-estimation method and the method based on least squares. A unique set of parameters is selected at every lattice point by comparing two sets identified by the two methods with each other in terms of errors in the identified relations between inputs and outputs. In order to realize the estimation of control accuracy when the identified parameters of the lattice points are used, a method is also presented in which the identified parameters and experimental data are used. The results of computer simulations and experiments are presented, which confirm the effectiveness of the proposed methods.