| dc.description.abstract | The sliding mode controller (SMC) is a type of variable structure control system
(VSCS), which is an authoritative tool for dealing with uncertainty, variations in
parameter systems, nonlinear systems and external disturbances. Although significant
advantages are associated with SMC such as robustness, the conventional sliding mode
controller (CSMC) does not cover most of the requirements of the system, especially
near the equilibrium point because of the high chattering which occurs as a result of
high-speed switching (high frequencies of control signal near sliding line). This thesis is concerned with developing a novel controller and algorithms to reduce the effect of the chattering phenomenon, in order to achieve an efficient system performance. It includes
three novel sliding mode concepts; sliding mode with state feedback controller
(SMSFC), pre-programmed exponential sliding mode controller (PPESMC), and
combination of nonlinear functions with sliding mode controller (CNFSMC). These are
based on the SMC concept.The SMSFC is designed to reduce the effect of the
chattering phenomenon that is present with the use of CSMC when noise and
uncertainties occur. This is accomplished by refining the gain amplitude of CSMC,
obtaining the convergence states properties of the system. The state feedback controller
reformats and combines seamlessly with the CSMC to produce an integrated controller
called a sliding mode with state feedback controller (SMSCF), whereas PPESMC relies
on the value of an error signal and generates an exponential gain which is proportional
to the error signal. Finally, a combination of nonlinear functions with sliding mode
controller (CNFSMC) can be constructed from a combination of SMSFC and PPESMC.
This method depends on two interrelated and nonlinear state-exponential properties.
These new controllers have proved to be a robust and effective integrated control
strategy for uncertain, varied-parameter, linear, and nonlinear systems, in addition to
reducing the effect of the chattering phenomenon. Performance evaluations,
comparisons, and analysis for the three methods (SMSFC, PPESMC and CNFSMC) for
the SMC system are presented in this thesis, and their performance compared with the
super-twisting (STW), boundary layer sliding mode (BLSMC) and low pass filter
(LPFSMC) with SMC methods respectively when applied to a DC motor and robotics.
The main conclusion drawn in this thesis was that the SMSFC as developed and
implemented exhibited robust and high performance and trajectory tracking control
given modeling uncertainties and noise. The evaluation and analysis were performed for
different performance indexes and under different operational conditions. The results
showed that under various external loads, external noise, and variations in system
parameters SMSFC, PPESMC, CNFSMC, STW, BLSMC and LPFSMC with respect to
reduction of the effect of the chattering phenomenon by 95%, 94%, 97%, 68%, 78% and
89% respectively. | en_US |
