In this paper a method is proposed to estimate the unknown parameters of nonlinear map based on the second-order discrete variational method. On the basis of adjoint equations and gradient expressions of cost functional derived from variational method, the second-order adjoint equations and the exact formulas for the Hessian-vector product are educed using the second-order discrete variational method. A new algorithm is given for estimating the unknown parameters of nonlinear maps. The numerical simulations show that all unknown physical parameters of Hyperhen´on map and two-dimensional parabolic map are estimated successfully and precisely. Simulation results also demonstrate the validity and advantages of second-order discrete variational method of estimating the parameters of the discrete chaotic systems.% 提出一种估计非线性映射未知参数的二阶离散变分方法。首先针对非线性离散混沌系统，利用变分方法导出了伴随方程和目标泛函梯度，以此为基础利用二阶离散变分方法给出了二阶伴随方程和精确计算Hessian矩阵-向量乘积的显式表达式；其次设计了估计非线性映射未知参数的新算法，并以此对Hyperhen´on映射和二维抛物映射中的未知参数进行了精确的估计。数值仿真结果表明了该方法的有效性和优点。
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