Modeling uncertainty in the form of additional gain and phase and calculating robustness margins based on them is one of the standard methods in designing robust control systems and comparing their robustness. On the other hand, one of the prevalent methods of robust control in the frequency domain is “Quantitative Feedback Theory”, which, due to modeling uncertainty in the form of parametric uncertainty with a specified range, faces challenges such as the inability to compare controllers and non-automated design. Additionally, the system's conditions for parametric uncertainty values outside the design range are unknown. This research addresses these issues using uncertainty modeling in the form of gain and phase within the quantitative feedback theory method. To this end, a combined margin consisting of gain and phase is introduced and calculated using a modified Nichols chart and inequalities related to design criteria in the quantitative feedback theory method. The position control of a DC motor is selected as a case study, and an optimal and robust proportional-derivative controller is designed for it. The results are examined both numerically and experimentally which show that the proposed method effectively overcomes the shortcomings of the quantitative feedback theory method. The controller designed in this manner gains more favorable results than the controller designed using the conventional quantitative feedback theory method and even maintains its performance better for parametric uncertainty values higher than the design range.

Nonlinearity is one of the main behaviors of systems in the real world. Therefore, it seems necessary to introduce a method to determine the stability margin of these systems. Although the gain and phase margins are established criteria for the analysis of linear systems, finding a specific way to determine the true value of these margins in nonlinear systems in general is an ongoing research in the literature. The main goal of this paper is to introduce a new method to determine these margins more precisely for particular type of nonlinearities. Based on Lyapunov theorem, stability conditions are obtained and the stability margins of Lur'e systems are determined by applying the extended circle criterion. By providing numerical examples, the correctness of the obtained results is checked and by comparing them with other methods, the accuracy of the obtained results is evaluated.

This article presents a fuzzy robust Mixed - Sensitivity gain - Scheduled H¥ controller based on the Loop -Shaping methodology for a class of MIMO uncertain nonlinear Time - Varying systems. In order to design this controller, the nonlinear parameter - dependent plant is first modeled as a set of linear subsystems by Takagi and Sugeno’s (T - S) fuzzy approach. Both Loop - Shaping methodology and Mixed - Sensitivity problem are then introduced to formulate the frequency - domain specifications. Furthermore, a Regular Weights Selection Method (RWSM) is used to devise a systematic design for choosing properly the weighting matrices. Afterwards, for each linear subsystem, an H¥ controller is designed via linear matrix inequality (LMI) approach. Such controllers are said to be scheduled by the Time - Varying parameter measurements in real time. The Parallel Distributed Compensation (PDC) is then used to design the controller for the overall system and the total linear system is also obtained through using the weighted sum of the local linear subsystems. Several results show that the proposed method can effectively meet the performance requirements like robustness, good load disturbance rejection and tracking responses, and fast transient responses for the 3 - phase interior permanent magnet synchronous motor (IPMSM). Finally, the superiority of the proposed control scheme is approved in comparison with the feedback linearization controller, the H2/H¥ Controller and the H¥ Mixed - Sensitivity controller methods.

In this paper, a Low Noise Variable gain Amplifier in Ka-frequency band is designed. This amplifier is digitally controlled by using switching transistors which change the gain with an accuracy of 5-bit resolution (32 steps). The output phase shift should be minimized within a Dynamic Range of 15 dB. The proposed structure includes a Low Noise Amplifier and a Variable gain Amplifier, with common-source structure and degenerative inductor. In the proposed structure, the main gain is achieved by LNA and the switching control bits are used in two stages of the VGA. Simulation illustrates a Noise Figure of 5. 6 dB; bandwidth of 5. 34 GHz; S11, S22 less than-14 dB and Dynamic Range of 15 dB. By using a “ compensating inductor” in the source of switching transistors, the amount of phase shift was reduced, such that within the bandwidth of 1. 5 GHz it is less than 5 degrees. The post-layout simulation results, show a Dynamic Range of 18. 7 dB; a bandwidth of 2. 5 GHz; Noise Figure of 6. 4 dB and return losses less than-10 dB. In addition to it, In EM analysis, all inductors and major RF paths are evaluated by “ Sonnet” software.

This paper presents a new high step-up DC-DC switched-mode converter in which not only the input and output ports can be connected to a common ground, but also the service time of the input source is extended due to continuous current injection to the proposed power converter. Furthermore, the fast dynamic response is offered by minimum phase characteristics. This key feature is achieved by making the proposed converter’s control to output transfer function, free from the right half plane zero (RHPZ). Full description of the operation principles, theoretical analysis related to steady-state operation, and also the small-signal modelling derivation of the proposed converter, are presented in this paper. In the end, to confirm all the merits of the proposed converter and accuracy of theoretical analysis, a sample 25 V - 100 V laboratory prototype DC-DC converter with 100W output power has been implemented, and the main experimental results have also been outlined.

In this paper, a new analytical method to find a near-optimal high gain controller for the non-minimum phase affine nonlinear systems is introduced. This controller is derived based on the closed form solution of the Hamilton-Jacobi-Bellman (HJB) equation associated with the cheap control problem. This methodology employs an algebraic equation with parametric coefficients for the systems with scalar internal dynamics and a differential equation for those systems with the internal dynamics of order higher than one. It is shown that 1) if the system starts from different initial conditions located in the close proximity of the origin the regulation error of the closed-loop system with the proposed controller is less than that of the closed-loop system with the high gain LQR, which is surely designed for the linearized system around the origin, 2). for the initial conditions located in a region far from the origin, the proposed controller significantly outperforms the LQR controller.

Background: Objective structured Practical examination (OSPE) is one of the methods to minimize the variations in subjectivity, thus enhancing objectivity. Currently, OSPE is used for formative assessment during internal examinations in many institutes as universities have still not incorporated it. This study is designed concerning the perception of teachers and phase III part 1MBBS students regarding OSPE and traditional Practical examination Methods for phase III part 1MBBS students. Methods: An analytical cross-sectional study as a part of educational research was done at a government medical institute in India to explore the perception of students and teachers of OSPE. Students were assessed on the traditional system and also on OSPE. The perception of the students and teachers was taken on a Likert scale-based questionnaire. The scores were also compared between the two groups. Results: In the present study a total of 92 students have participated in the OSPE and a total of 88 students have participated in the Traditional Practical examination. A greater number (18) of students could gain marks between 75%-99% by the OSPE method in comparison to the Traditional Practical examination(6). Almost half of the students (50. 9%) agreed to the statement that OPSE is a fair mean of examination in comparison to traditional Practical examination and are satisfied with the difficulty level (59. 6%) and believe that it is an effective and valid tool to assess knowledge (54. 4%). Maximum faculty (66. 7%) agreed and 33. 3% of faculty strongly agreed that OSPE is an effective tool for assessment, is a well-organized system and covers most of the topics from the syllabus. Conclusion: This study showed there was a significant difference in scores obtained in OSPE, in comparison with conventional Practical examination. Hence, OSPE is a more effective and valid assessment tool as inter-examiner variation and bias will be eliminated.

This paper presents a wide input voltage range negative impedance converter (NIC) circuit operating in weak inversion. A small signal analysis has been performed, resulting in a circuit model that characterises the input impedance function, Zin(s). A boosted folded cascode (BFC) OTA is presented using the proposed NIC. Incorporating the proposed NIC at the output node of a folded cascode (FC) OTA, the output impedance is increased, resulting in a noticeable improvement in the overall voltage gain without phase margin (PM) degrading. Post-layout simulation is performed using standard 180nm CMOS technology, while the two essential large resistors of the proposed NIC are considered off-chip components. The boosted OTA exhibits a DC gain improvement of 17 dB with no PM degradation over a conventional FC OTA at the expense of 1.5% more power consumption. The proposed NIC circuit can be incorporated easily into any boosted OTA realized by alternative methods. Based on this concept, a double-boosted OTA is also introduced.

Architecture experience is among educational strategies widely used in architectural teaching. One area wherein this strategy can be adopted is the gaining of Practical knowledge of design, since observing architectural works has a major impact on improving the mental skills of an architect which would come to use later in the creation of architectural works. Experience of architectural examples with such a design-oriented approach would prove effective in promoting the Practical knowledge of an architect in the design phase when the cognitive impacts and visual perceptions of that experience come to use as mental preconceptions in the visualization process. This essay aims to introduce a solution that would make such quality experience possible. The proposed solution is described as the “ active experience model. ” The research findings, which are based on the logical analysis of data from library sources, demonstrate the fact that a quality architecture experience would include the successful completion of verbal attention and visual processing. These two stages are pillars of the “ active experience model” whose effectiveness was evaluated through a field study involving several students from the Art and Architecture Faculty at Yazd University. The results prove that the relationship between successful active experience and both the quantity and quality of retrieving visual information perceived during that experience is statistically significant in comparison to simple observing.