What is sliding mode control in the context of dc-dc converter?4 answersSliding mode control (SMC) is a robust control technique applied in DC-DC converters to regulate voltage effectively. Different approaches like indirect SMC and second-order SMC are utilized for improved performance. Indirect SMC simplifies implementation by using input current error for sliding surface determination, ensuring stable output voltage regulation with a PI controller. On the other hand, second-order SMC eliminates chattering and relative degree restrictions, employing algorithms like prescribed convergence law, twisting, and super twisting algorithms for enhanced control. By integrating SMC with DC-DC converters, these methods enhance voltage regulation, stability, and performance under varying load and input voltage conditions, as demonstrated through simulations in Matlab/Simulink environments.
What is terminal sliding mode control and non-singular terminal sliding mode control?5 answersTerminal sliding mode control (TSMC) is a control strategy that aims to drive the system's state variables to a sliding surface in finite time and maintain them on this surface thereafter. It is designed to handle uncertainties and disturbances efficiently. Non-singular terminal sliding mode control (NTSMC) is an enhanced version that eliminates singularity and chattering issues associated with traditional TSMC. NTSMC ensures finite-time convergence to an equilibrium point without encountering singularities. Both TSMC and NTSMC have been successfully applied in various systems like exoskeletons for gait tracking, multi-motor position synchronization control, and chaotic 3-bus power system dynamics control. These control methods offer improved stability, robustness, and performance compared to conventional sliding mode control approaches.
What are the challenges of using a unified control center for transit?5 answersA unified control center for transit faces several challenges. These challenges include the need to ensure consistency between user-related information and right-related information of each service system. Another challenge is the coordination and integration of different functional partitions within the system, which requires a unified software control capable of transferring calls and directing communications. Additionally, there are institutional, operational, and technical barriers that need to be addressed in order to achieve the goals of integration in transit systems. The migration to a distributed client-server architecture also presents challenges in optimizing resources and ensuring efficient data processing. Finally, the development of a power control center faces challenges related to the evolving power sector and the need for more refined management and industry convergence.
How can sliding mode control be implemented in hardware?5 answersSliding mode control can be implemented in hardware by designing a sliding surface or switching curve that guides the system's states. The sliding surface can be non-linear and time-varying to ensure robustness to external disturbances and finite regulation time. For nonlinear semi-Markovian switching systems with quantization, a mode-independent sliding surface is designed to avoid repetitive jumping effects, and a sliding mode control law is used to force the system states onto the sliding surface. In the case of linear systems, the unit sliding mode control design methodology can be used, and control parameters can be tuned based on known perturbation magnitudes. For underactuated systems like a bridge crane, a variable structure sliding mode controller can be designed to achieve rapid positioning and prevent load swing. An adaptive sliding mode disturbance observer can also be used to actively counteract disturbances, and an output feedback sliding mode controller can be constructed for continuous-time linear systems with unknown external disturbances.
What are drawbacks of ARM method?3 answersThe drawbacks of the ARM method include the need for arbitrage-free option prices, the identification of the closest arbitrage-free approximation in the presence of noise, and the potential for inconsistencies in quoted option prices for longer durations. Additionally, the ARM problem is computationally hard to solve, requiring critical design choices in the data analysis workflow. In the context of cache consistency, the implementation of the active refresh method (ARM) can pose challenges. Furthermore, when using arm images for biometric recognition, motion blur can degrade image quality and hinder vein information recovery.
What are limitations of PID?4 answersPID control has limitations, particularly when dealing with unstable processes. One major limitation is the introduction of a close-to-the-origin zero, which can undermine damping and cause excessive overshoot. To address this, an alternative configuration called I-PD control can be used. In this configuration, the PD part is placed in parallel to the process (inner loop), while the I part is left in cascade (outer loop). This I-PD configuration stabilizes the process and achieves the desired transient response without introducing unwanted zeros. It has been shown that I-PD control guarantees full controllability, robustness, and asymptotic tracking and disturbance rejection for second-order processes, whether they are stable, integral, or unstable.