1. A method of configuring a controller for a plant using a sliding-mode control scheme, the method comprising: obtaining a measured observation data sequence by an open-loop control measurement of the plant; describing a state space equation of the plant by a system identification technique based on the measured value, and designing a switching hyperplane for a sliding-mode control model; calculating a third-order statistic and a fourth-order statistic on a difference between an output of a linear model on the hyperplane and an output of the sliding-mode control model in the observation data sequence; calculating a nonlinear control input term based on a fourth-order moment if either of the third-order statistic and the fourth-order statistic is larger than a predetermined threshold, and configuring a controller by a sum of a control input term of the linear model on the hyperplane and the nonlinear control input term; and configuring a linear controller with a linear control input on the hyperplane if both the third-order statistics and the fourth-order statistics are smaller than the predetermined threshold.