Engineering and Technology Journal

Sliding Mode Controller (SMC) is a simple and effective method to recognize a robust controller for nonlinear system. It is a strong mathematical tool which gives a nonlinear robust controller with acceptable performance. The chattering phenomenon is the major drawback that sliding mode control suffers from. This phenomenon causes a zigzag motion along the sliding surface. In this work to design SMC, the Saturation function (i.e., boundary layer) has been used instead of the Sign function that was used in classical sliding mode controller in order to reduce the chattering phenomena which are appearing in the sliding mode phase. The genetic algorithms have also been proposed in this work for the parameter selection method of Sliding Mode Controller and the results showed a high speed of the system state for reaching the sliding surface during the reaching phase and a chattering reduction during the sliding phase. A pendulum system has been used for testing the designed sliding mode controller. The simulation results showed good validity of the suggested method. Matlab programming and simulink were adopted for the simulation results.

Sliding mode control algorithm that uses fuzzy saturation function is designed in
this paper for nonlinear system. The fuzzy saturation function is suggested to improve
the accuracy and the robustness of the sliding mode control which are partially lost
when using a fixed boundary layer. The fuzzy saturation function is simple, in the
sense that both the membership functions and the rule base are simple. The overall
control algorithm has stability assurance for the closed-loop controlled system;
therefore, it may be applied to control different systems, in this paper this algorithm is
applied on nonlinear SISO system with 10%parameter uncertainty and nonlinear
disturbance. Simulation results show that the developed algorithm has good control
performance with negligible chattering.

Sliding Mode Controller design provides a systematic approach to the
problem of maintaining stability and consistent performance in the face of modeling imprecision. The major drawback that sliding mode control suffers from is the chattering phenomenon, which is a zigzag motion along the sliding surface caused by the high frequency motion on the sliding surface. This phenomenon is an undesirable property since it excites unmodeled dynamics and results in tear and wears in the mechanical systems. In this work several methods are proposed to
reduce the chattering. One of these methods is to use the boundary layer solution to smooth the hard switching signal. This solution is compared to another one represented by involving the intelligent systems to enhance the performance of the sliding mode controller system like involving the Genetic Algorithm (GA) and the
fuzzy tuning technique. GA has proved its efficient ability to attenuate chattering and reduce the hitting time compared to other methods.

The race toward new heights has led to the construction of tall flexible buildings
with low inherent structural damping. As buildings get taller their sensitivity to wind
excitations increases which threaten their integrity and serviceability. Therefore the control
of gust responses of tall buildings has gained worldwide attention. In this work an adaptive
Sliding Mode Control (SMC) driven Magneto Rheological (MR) fluid damper is proposed
for the vibration control problem of a wind excited tall building. The equivalent control part
proposed in this work is based on filtering the overall discontinuous control signal for a
better satisfaction of the reachability condition on one hand, and to heal the chattering
phenomenon on the other which is further reduced by replacing the hard switching sign
function by the sigmoid-like function. The adaptive tactic is based on using 3 second time
average variations of the gust speed to estimate the wind loading on the structure by
utilizing the theory of quasi-steady aerodynamics.