2
SHIMOYAMA et al. [9] and Jun Zheng, Xinyu Shao, Liang Gao
et al. [10] proposed Kriging and RBF mixed response surface
methods for highly nonlinear functions, which RBF neural
network is approximated low-frequency terms and Kriging
interpolation is approximated high-frequency term. Kriging
interpolation is used the cross-validation method to fit the high-
frequency characteristics of the function, but which can require
a lot of computation time. In order to reduce the calculation time,
it is necessary to reduce the amount of data used in this part,
which will lead to the final accuracy of the compositing function
is not high enough. This article mainly deals the variation of the
generalized regression neural network in the fitting, and uses
Kriging interpolation to fit this fluctuation error.
Aiming at the fluctuation of the prediction accuracy of the
generalized regressive neural network when dealing with
complex problems [11], this article constructs a generalized
regression neural network surrogate model construction method
based on the Kriging interpolation fitting deviation (Kriging-
GRNN,KGRNN).This method through the different training
sets, the fluctuation deviation generated by the generalized
regression neural network in the fitting is extracted, and the
fluctuation deviation is approximated as a multivariate normal
distribution. Then, the Kriging interpolation is used to fit the
multivariate normal distribution function in the fitting interval,
and the multivariate normal distribution solved by Kriging
interpolation is subtracted from the trained generalized
regression neural network. Finally, the method is validated by
using different test functions and engineering examples.
2. GENERALIZED REGRESSION NEURAL NETWORK
AND KRIGING INTERPOLATION ALGORITHM
DESCRIPTION
2.1 The working principle of GRNN
Generalized Regression Neural Network is a four-layer
neural network, including input layer, pattern recognition layer
(radial-based neurons), linear summation layer and output layer.
As shown in FIGURE 1.
FIGURE 1: Structure of generalized regression neural network
the number of processing units in the input layer R is equal
to the number of components of the input vector, the number N
of neurons in the intermediate pattern recognition layer is equal
to the number of learning samples. Generally, the number of
neurons in the summation layer is two, which used to calculate
the weighted output sum of the neurons of the pattern recognition
layer S and the pattern recognition layer unweighted output D.
The activation function of the pattern recognition layer neurons
is as shown in equation (1).
(1)
The output of the pattern recognition layer neuron i is an
exponential form of the square of the Euclid distance between
the input variable and it’s corresponds sample X. X is the
network input variable;
is the sample of the learning
corresponding to the i-th neuron.
The summation formulas of the two neurons in the
summation layer are:
(2)
(3)
In the above formula,
is the weight that connects the i-th
neuron of the recognition layer to the summation layer, and σ is
the smoothing factor.
Generalized Regression Neural Networks is a powerful tool
for nonlinear regression analysis. For the input vector X, the
output Y of the generalized regression neural network is
calculated by the following function:
(4)
Generalized regressive neural network is a variation of RBF
neural network and often used for function approximation [12].
The generalized regression neural network can adjust the number
of hidden layer neurons. The more neurons in the hidden layer,
the more accurately the approximation is. Therefore, generalized
regression neural networks have more advantages than the
ordinary RBF neural networks.
2.2 The principle of Kriging interpolation
Kriging predicts the value of a function at a given point by
calculating the weight average of the values of the sample points
of the function in the neighborhood of the point. Kriging
interpolation is a linear undeviationed optimal estimation
interpolation method, which not only considers the positional
relationship between the observation point and the estimation
point fully, but also considers the spatial relationship [13].
According to the principle of Kriging interpolation, if there
has the known noise N (0, σ
2
) in the simulated model, the known
...
X
1
X
2
X
R
S
D
Y
Input layer Pattern Layer
Summation layer
Output layer
...
G
1
G
2
G
3
G
N-1
G
N