Backstepping Sliding Mode Control for Inverted Pendulum System with Disturbance and Parameter Uncertainty

The inverted pendulum system is highly popular in control system applications and has the characteristics of unstable, nonlinear, and fast dynamics. A nonlinear controller is needed to control a system with these characteristics. In addition, there are disturbances and parameter uncertainty issues to be solved in the inverted pendulum system. Therefore, this study uses a nonlinear controller, which is the backstepping sliding mode control. The controller is robust to parameter uncertainty and disturbances so that it is suitable for controlling an inverted pendulum system. Based on testing with step and sine reference signals without interference, the controller can stabilize the system well and has a fast response. In testing with disturbances and mass uncertainty, the backstepping sliding mode controller is robust against these changes and able to make the system reach the reference value. Compared with sliding mode control, backstepping sliding mode control has a better and more robust response to disturbances and parameter uncertainty

Optimizing the Parameters of Sliding Mode Controllers for Stepper Motor through Simulink Response Optimizer Application

This paper will focus on optimizing parameters of sliding mode controllers (SMC) for hybrid stepper motor models simulated in Matlab/Simulink. The main objective is to achieve a smooth transient and robust, steady-state to track reference rotor position when the stepper motor is subjected to load disturbances. Two different structures of SMC controllers will be studied, which are based on the flat system concept that is applicable to the stepper motor model. The hassle to determine controller parameters will be optimized using the Simulink Response Optimizer application.  The performance of the controllers will be evaluated by considering load torque and variation in the model parameters. Although the results showed that an open-loop controller could move the rotor to the desired position, however, the transient response had undesired oscillations before the output settled at the steady state. The response was improved by optimizing SMC controllers’ parameters to meet the desire step response requirement. Despite both SMC methods have successfully tracked the reference, there are some challenges to deal with each method in regard to the state measurements, the number of optimized controllers’ parameters, and the scattering of control inputs

A Survey of Control Methods for Quadrotor UAV

Flight control design of unmanned aerial vehicles UAVs is becoming increasingly important due to advances in computational power of computers with lower cost. The control algorithms are mainly employed for the attitude and position control of the UAVs. In the past decades, quadrotors have become the most popular UAVs, their adaptability and small size. They are employed to carry out tasks such as delivery, exploration,  fumigation, mapping, surveillance, rescue mission, traffic monitoring, and so on. While carrying out these tasks, quadrotor UAVs face various challenges, such as environmental disturbances, obstacles, and parametric and non-parametric perturbations. Therefore, they require robust and effective control to stabilize them and enhance their performance. This paper provides a survey of recent developments in control algorithms applied to attitude and position loops of quadrotor UAVs. In addition, the limitations of the previous control approaches are presented. In order to overcome the relative drawbacks of the previous control techniques and enhance the performance of the quadrotor, researchers are combining various control approaches to obtain the hybrid control architecture. In this study, a review of the recent hybrid control schemes is presented

An Adaptive Sliding Mode Control for Single Machine Infinite Bus System under Unknown Uncertainties

The inherent uncertainties in a Single Machine Infinite Bus System (SMIBS) are governed by unmodeled dynamics or large disturbances such as the system's faults. The existence of these uncertainties demands robust controllers to guarantee the system's asymptotic stability under such exacting conditions. In this work, we propose an Adaptive Sliding Mode Control (ASMC) design implemented on a fifth-order nonlinear SMIBS to handle those uncertainties without prior knowledge about its upper bounds. We develop the ASMC with gains of two nested adaptive layers to asymptotically stabilize the system's internal states, the machine's terminal voltage, and power angle within a region of unknown bounded uncertainties while mitigating the chattering phenomena associated with conventional Sliding Mode Control (SMC). To verify the design's effectiveness and prove the conducted Lyapunov theoretical stability analysis, we simulate the occurrence of a large disturbance represented by a 3-phase fault at the system's universal bus. The results show that the ASMC can successfully achieve asymptotic stable output errors and stabilizing the SMIBS internal states after the clearance of the fault. Moreover, the ASMC noticeably outperforms the SMC in chattering mitigation, where the ASMC's signal is significantly smoother than that of the SMC

Iterative Learning Control for Load Frequency in Cyber-Attacked Multi-Area Power Systems

Sustaining the performance of the power grid at a desired operating point is a challenge in an uncertain environment. As a result of the environment’s dynamic and unpredictable nature, the multi-area-linked power system is impacted by communication limitations and load variance. Due to the widespread nature of electricity, several power regions share information inside a communication network. In complex networks, connectivity restrictions, which include time delays, information loss, and restricted bandwidth, may impair the dependability and scalability of the control method. Variations in the load can affect the stability of the power systems. Due to the active load change and the dynamic environment and uncertainty, a model-free controller is a suitable technique that can maintain reliable performance in this condition. The online adaptive policy control scheme is proposed for load frequency control (LFC) challenges in single and multi-area power grids. The proposed scheme uses an optimal control approach through a modified Bellman equation and two neural networks, one to approximate the proposed solving value function and the second one to approximate the optimal control. The performance of the proposed model free adaptive control is compared with that of the model predictive control

A New Septum in the Female Breast

Background Understanding the female breast fascial system is of paramount importance in breast surgery. Little was written about breast ligaments. Most articles refer to Cooper's work without further anatomical studies. Lately, a horizontal septum has been described conveying nerves and vessels to the nipple areola complex. Methods During the surgical dissection of the lower part of the breast, in supero-medial technique for breast reduction operations, a fascial septum between the lower two quadrants was detected. This fibrous septum was studied through anatomic dissection of breast tissues during routine breast reshaping procedures that was done on 30 female patients. Magnetic resonance imaging (MRI) was performed preoperatively in all cases and correlated with the intraoperative findings. In the other five cases, outside the clinical study, the imaging was done during routine investigation for breast swellings. Results A vertical septum was identified in the lower part of the breast, lying at the breast meridian between the two lower quadrants. It is a tough bi-laminated structure that extends from the middle of the infra-mammary crease caudally to nipple-areola complex cranially and from the pectoral fascia posteriorly to the overlying skin anteriorly. This was proved by MRI findings. Conclusions This study describes a new inferior vertical septum which separates the lower half of the breast into two definite anatomical compartments: medial and lateral