super twisting algorithm

In this study, a super-twisting algorithm, using the sliding surface as a fractional-order non-singular terminal sliding mode (NTSM), is presented. In robust control, one of the important problem is the reduction of system error and reduce the chattering. One of the most common applications of sliding mode controllers is about the reduction of chattering. Also, utilizing the fractional calculus in controller design brings more accuracy and reduces system errors. Utilizing a higher-order sliding mode controller using the super-twisting algorithm and the fractional-order non-single terminal sliding mode for the two-link serial robot is the novelty of the presented research. The design of the suggested controller is such that it is independent of the robotic manipulators model and is based on the system errors. Stability analysis of the close-loop system has performed using Lyapunov's method. The simulation results show high accuracy, fast convergence, and high robustness of the proposed fractional-order super-twisting nonsingular terminal sliding mode control.

Vehicle stability control is one of the most important subjects in control engineering field. Many research activities have been done to develop more comfort and safe travel for passengers. In this paper, vehicle mixed stability in longitudinal and lateral motion has been investigated. Full model of vehicle (4 wheel) is considered to extract the dynamic equations. Dugoff’s nonlinear model has been used to simulate the behavior of tyres and road, and Cho’s engine model with two state variables has been used for vehicle power system simulation, so it makes the input torque to wheels to be more realistic. Because of the good robustness properties of sliding mode control the second order sliding mode with super-twisting algorithm has been used for calculation of control inputs. This method is proved to be so appropriate and useful in the case of uncertainty in complicated vehicle dynamic model and multiple disturbances in vehicle motion. Engine throttle angle and yaw moment have been considered as longitudinal system and lateral system control inputs respectively. Longitudinal slip coefficient and yaw rate are considered as system output. Simulation results shows the effectiveness of the proposed method.

In this paper, the performance of two robust control algorithms, µ-synthesis and high order sliding mode are evaluated on a spacecraft attitude control subsystem simulator as the hardware in the loop. This tabular simulator is placed on a spherical air bearing to validate real-time environment. All actuators and sensors on the platform of spacecraft simulator prepare real conditions as attitude control test bed. Beginning, both designed controllers are simulated by Matlab software, next they are applied on the subsystem. At first, µ-synthesis robust controller is designed for simulator. In this method, weighting matrix are chosen such that the controller becomes robust in combined uncertain condition such as system uncertainties, environmental disturbances and sensor noises. Uncertainty, performance, actuator saturation, disturbance and noise weighting functions are designed based on the dynamics and environmental platform properties. At least high order sliding mode controller based on super twisting algorithm is designed to reduce chattering effects. Contrary to the other second order sliding mode algorithms, in the super twisting method sliding surface derivatives are not used. The Computer and experimental hard ware in the loop simulations are compared together.