Tensor-based type-2 random vector functional link network
Guoliang Zhao
1,2
,WeiWu
1
1. School of Mathematical Sciences, Dalian University of Technology, Dalian 116024, Peoples Republic of China
E-mail: guoliangzhao@imu.edu.cn
2. College of Electronic Information Engineering, Inner Mongolia University, Hohhot 010021, Peoples Republic of China
Abstract: In the paper, random vector functional link (RVFL) network is extended by the tensor structure,
and the enhancement nodes are replaced by type-2 fuzzy sets. Two versions of RVFL network are proposed,
one is the interval type-2 RVFL network, and the other is the tensor-based type-2 RVFL network. The interval
type-2 RVFL network is similar to the original RVFL, the only difference is that the outputs of enhancement
nodes are the defuzzification results of the uncertainty weight method. The tensor-based type-2 RVFL net-
work adopts the defuzzification results of the uncertainty weight method, together with values of the lower
membership functions and values of upper membership functions, a 4-dimensional tensor is then formed
based on the three components; then, Moore-Penrose inverse of even-order tensor which is implemented via
Einstein product is used for solving the tensor equation. Moreover, the weighting vector is obtained via a
balance weighting factor, which is resulted from a weighted average of the weighting vector of RVFL network
and the weighting vector of the solution to the abovementioned tensor equation. Finally, the proposed algo-
rithms are verified on three nonlinear benchmark functions, a nonlinear system identification problem, and
four regression problems.
Key Words: Functional-link network (FLN), Random vector functional link (RVFL) network, Tensor equation,
Interval type-2 RVFL (IT2-RVFL), Tensor-based type-2 RVFL (TT2-RVFL)
1 INTRODUCTION
FLNs are single-layered neural networks that impose
nonlinearity on input layer using many kinds of non-
linear functions [1]. FLNs can be categorized into two
groups based on the type of weighting factors: RVFL
network and functional-based FLN depending on the
usage of various types of function basis. With ran-
domly generated weights between input and hidden
layers, RVFL network is a universal approximator for
continuous functions on compact sets with fast learn-
ing property [2]. RVFL network exploits connection
between the input layer and the output layer through
orthogonal functions [3]. The orthogonal polynomial-
based RVFL network is proposed by utilizing advan-
tages from expansion of the input vector and ran-
dom determination of the input weights. A parsimo-
nious RVFL is proposed [4] to endorse the network
with self-organizing property. Furthermore, FLN is
also modified and trained by artificial bee colony,
and the drawback of BP-learning scheme is overcame
by the intelligent algorithm [5]. Moreover, the ef-
fect of input-output connections of the solar power
data of Sydney is studied, and it is found out that
RVFL performs better than other random weight sin-
gle shrouded layer feed-forward neural networks and
single shrouded layer feed-forward neural networks
[6]. Based on the learning strategy that uses privi-
This work is supported by National Nature Science Foundation
of China under Grant 61603126 and 61773088.
leged information paradigm, an alternative way to
train RVFL networks is provided, which is named
as RVFL+ network [7]. An RVFL network ensemble
is introduced by employing ”perturb and combine”
strategies, and the proposed RVFL network ensem-
ble also outperforms all neural network-based meth-
ods used in the experiments [8]. To serve as general
guidelines for designing RVFL networks-based clas-
sifiers, Zhang and Suganthan [9] studied five factors,
that is, output layer’s bias, direct links, activation
function type, scaling of parameter and the solution
procedure of the RVFL, which effect the classification
ability of RVFL networks.
To the FLNs, a functional link-based novel recur-
rent fuzzy neural network is applied for the static
synchronous compensator to reduce the power fluc-
tuations, the proposed controller can achieve better
damping characteristics and effectively stabilize the
network under unstable conditions [10]. A func-
tional link-based recurrent FNN for the variable-
speed switched reluctance generator control has been
studied by Hong and Huang, and the node connect-
ing weights of the net are trained online by back-
propagation algorithms [11]. Functional link least
square principle has been used to solve robust regres-
sion problems [12]. An interactively recurrent self-
evolving FNN which employs an FLN to the con-
sequent part of fuzzy rules is proposed for predic-
tion and identification of dynamic systems [13], and
the mapping ability and the performance results of
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2019 IEEE