Dimitri Mahayana

Robust chattering free adaptive neuro sliding mode control for SVC system

Recently, there has been a surge of interest in the development and use of Flexible AC Transmission Systems (FACTS) controllers in power transmission systems. The most popular type of FACTS devices in terms of application is the Static Var Compensator (SVC). In FACTS, there are many uncertainties such as sudden load shedding, generation tripping, occurrence of faults, change of parameters, and network configuration. Traditional linear controllers have many difficulties in treating these uncertainties. To overcome this problem, sliding mode control (SMC) has been widely used as one of the precise and robust algorithms. Although classical SMC is a powerful scheme for nonlinear systems with uncertainty, this control scheme has important drawbacks limiting its practical applicability, such as chattering and excessive control action. To alleviate the problems, the discontinuous part of the control signal in the classical SMC is substituted by neural network to eliminate the chattering phenomenon. The neuro sliding mode proposed in this paper consist of a one layered neural network whose activation functions are linear. The main working principle of the controller is minimizing a cost function which is determined from the requirements of the Lyapunov stability criteria and sliding mode control theory. Simulation results show the significant improvement of transient response which practically enables the use of a neuro sliding mode controller in FACTS.

Static anti-windup compensator design of linear Sliding Mode Control for input saturated systems

A feedback control system involving a linear Sliding Mode Controller (SMC) and an input saturated linear plant is considered here. The linear SMC is designed for linear plant without saturation on its input. The resulting feedback system will not necessarily show an intended performance if the control input to the plant is saturated. In addition, a directionality problem for multivariable input systems may occur during the saturation. As a result, transient response performance could be degraded and its control signals may not be stabilizing the feedback system anymore. In this case, a directionality compensator may be designed to overcome the problem while optimizing its performance.

Robust adaptive control for robotic manipulator based on chattering free variable structure system

In robotic manipulators there are many uncertainties such as dynamic parameters (eg., inertia and payload conditions), dynamical effects (e.g., complex nonlinear frictions), and unmodeled dynamics. Traditional linear controllers have many difficulties in treating these uncertainties. To overcome this problem, a robust adaptive control for robotic manipulator based on chattering free variable structure system is proposed. Conventional variable structure control (VSC) has important drawbacks limiting its practical applicability, such as chattering and excessive control energy. To alleviate the problems, the discontinuous part of the control signals in the conventional VSC are substituted by adaptive gain. Within this scheme, the adaptive gain are employed to approximate the unknown systems uncertainties. The key feature of the controller is that prior knowledge of the system uncertainties is not required to guarantee the stability. Moreover, a theoretical proof of the stability and convergence of the proposed scheme using Lyapunov method is presented. To demonstrate the effectiveness of the proposed approach, a practical situation in robot control is simulated.

On applicability of chaos game method for block cipher randomness analysis

Block cipher can be considered as a random permutation function which maps a set of plaintext character P to a set of ciphertext character C. Block cipher is designed in a way that the effort to distinguish it from a random permutation function will be very difficult or computationally infeasible. It this paper, block cipher randomness analysis is performed by using chaos game method. The method treats block cipher as a mapping function of a discrete time dynamical system. The system is used to generate a random sequence. Next, chaos game method analyzes the sequesnce in order to reveal its characteristics or regularities. The applicability of the method to reveal some characteristics of a block cipher is verified by using it for comparing the randomness of three-round and four-round SPN-network and distinguishing them from each other. So, the method can role as a distinguisher.

Design and implementation of density sensor with flow rate as disturbance

In distillation process, density sensor that can overcome the flow rate is very important. This paper represents design and implementation of density sensor with flow rate as a disturbance. The fluid density experiments were carried out using several mixtures of alcohol and water that flew in various percentages. In this design, the density of the fluid is affected by the distance, the height displacement of the hydrometer is measured by the ultrasonic, and the ultrasonic oscillations are ± 1.5 mm which was caused by echo characteristics of the ultrasonic sensor. The problem has been solved with pulse-echo mode with 500 sampling data and 1 ms of sampling time, hence the ultrasonic reading is steady. When the height displacement is greater, the alcohol concentration in the water is higher. The correlation between the height displacements to concentration is non-linear. Various methods of relation model from a distance to concentration have been shown and compared. The best model was acquired by using power equation with a Root-Mean-Square-Error (RMSE), and the result was 2.945. The volume flow rate characteristic has been studied and considered in order to eliminate disruption to concentration readings. The Linear model approach was applied to avoid the influence of the volume flow rate with Root-Mean-Square-Error (RMSE), and the result was 1.095. Minimum flow rate is 0.2 L/m, and maximum flow rate is 0.75 L/m.

Brushed DC motor controller using robust indirect adaptive control

Electric motors play an important role in industry as well as our day-to-day life. They are used to generate electrical power in power plants and provide mechanical work in industries. They are also an indispensable part of our daily lives. Electric motors are very important pieces of equipment in our everyday lives. The brushed dc motor is considered to be basic electric motors.