Published in IET Signal Processing
Received on 24th July 2013
Revised on 11th March 2014
Accepted on 28th March 2014
doi: 10.1049/iet-spr.2013.0296
ISSN 1751-9675
Fast-rate residual generator based on multiple
slow-rate sensors
Hang Geng, Yan Liang, Xiaojing Zhang, Feng Yang
School of Automation, Northwestern Polytechnical University, Xi’an, People’s Republic of China
E-mail: liangyan@nwpu.edu.cn
Abstract: This study puts forward the problem of fast-rate fault detection based on multiple slow-rate sensors. A fast-rate residual
generator with casuality constraint is established from the multi-sensor model. Parameters of the residual generator are determined
via disturbance-decoupling based on left eigenvector assignment. It is found that the condition of disturbance-decoupling is
related to the multi-rate sensor sampling nature. A numerical example is given to illustrate the effectiveness of the proposed
residual generator.
Nomenclature
x state vector
y output vector
r residual vector
d disturbance vector
I identity matrix
0 zero matrix
K gain matrix
T casuality constraint matrix
diag {·} a block diagonal matrix
superscript u, d, f refer to the control, disturbance and
fault, respectively
subscript i refers to the ith sensor
superscript −1 refers to the inverse operation
superscript T refers to the transpose operation
1 Introduction
Since the beginning of the 1970s, research on fault diagnosis
has gained increasing consideration world-wide in both
theory and applications [1–4]. The development was (and
still is) mainly stimulated by the trend of automation
towards more complexity and the growing demand for
higher availability and security of control systems [5–8].
In many complex systems, it is often unrealistic or
sometimes impossible to guarantee all physical signals
operating at one single-rate [9]. In this regard, standard
single-rate residual generators based on parity space and
observers were extended to the multi-rate case [10, 11].
Through converting a multi-rate sampled-data (MSD)
system into a linear time-invariant model with a slow
sampling rate, a residual generator was presented based on
parity space [12]. A residual generator for multi-rate
sampled-data systems was considered and the derived
performance index reflected the compromise between
sensitivity to faults and robustness to the unknown inputs
[13]. However, above the methods output the slow-rate
residual, which is not desirable in fast fault detection.
Considering the multi-rate sensor fault detection, a bank of
single-rate observers are derived, where the ith observer is
dedicated to the ith sensor [14]. The resultant detectability
condition seems too stringent by the fact that detecting the
ith sensor faults is just based on the ith sensor
measurements, instead of all sensors’ measurements. In
[15], an observer-based fault detection scheme was
designed for periodically time-varying systems (including
the multi-rate sampled-data system as a special case) based
on H
2
estimation approach. By optimising the predefined
performance index, a fast-rate scheme for fault detection
was given to obtain an optimal parity space based residual
generator [16]. Later, the fast-rate residual generator was
achieved by optimising the performance index in H
∞
sense
under the causality constraint [17]. In [18], a unified fault
detection and isolation approach was modified to solve the
problem of residual generation to obtain a slow-rate residual
generator with causality constraint and an inverse lifting
operation was implemented for fast-rate residual generation.
However, to our best knowledge, a still open problem is
how to design a fast-rate fault residual decoupling with the
unknown disturbance based on multiple slow-rate sensors.
In this paper, a fast-rate residual generator based on
multiple slow-rate sensors is proposed. By lifting the
multi-rate multi-sensor model to a single-rate one, a residual
generator with causality constraint is obtained, whose
parameters are determined through decoupling the residual
with the disturbance based on the left eigenvector
assignment. It is found that the resultant decoupling
condition is related to the casuality constraint because of
the multi-rate nature.
The rest of this paper is organised as follows. The problem
under investigation is formulated in Section 2. The fast-rate
residual generator is established in Section 3. The
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The Institution of Engineering and Technology 2014
IET Signal Process., 2014, Vol. 8, Iss. 8, pp. 878–884
doi: 10.1049/iet-spr.2013.0296