Stabilization of the Cart–Inverted-Pendulum System Using State-Feedback Pole-Independent MPC Controllers

In this paper, a pole-independent, single-input, multi-output explicit linear MPC controller is proposed to stabilize the fourth-order cart–inverted-pendulum system around the desired equilibrium points. To circumvent an obvious stability problem, a generalized prediction model is proposed that yields an MPC controller with four tuning parameters. The first two parameters, namely the horizon time and the relative cart–pendulum weight factor, are automatically adjusted to ensure a priori prescribed system gain margin and fast pendulum response while the remaining two parameters, namely the pendulum and cart velocity weight factors, are maintained as free tuning parameters. The comparison of the proposed method with some optimal control methods in the absence of disturbance input shows an obvious advantage in the average peak efficiency in favor of the proposed SIMO MPC controller at the price of slightly reduced speed efficiency. Additionally, none of the compared controllers can achieve a system gain margin greater than 1.63, while the proposed one can go beyond that limit at the price of additional degradation in the speed efficiency.

In-Pixel CTIA & Readout Circuitry for an Active CMOS Image Sensor

This work aims to design and simulate an in-pixel Capacitive Transimpedance Amplifier (CTIA) and peripheral circuitry that ensures pixel reading. Each pixel circuit is composed of four transistors using 90nm CMOS technology with a supply voltage of 1.8 V and is part of an array of pixels that make up a CMOS image sensor with peripheral circuitry. Pixel output is sent to a delta difference sampling (DDS) circuit to filter reset voltages. The Gain Margin achieved for the in-pixel CTIA is 44dB and 91dB for the Phase Margin. We also present measured pixel parameters and give a comparison with prior work. The timing and readout circuitry is also described.

Simplified cascade multiphase DC-DC buck power converter for low voltage large current applications: part II --- output current controller

<span lang="EN-US">This paper proposes a control method for new simplified cascade multiphase direct current-direct current (DC-DC) buck power converters used for low-voltage large-current applications such as cathodic protection. To control the proposed converter, a proportional-integral (PI) controller is used to regulate the output current of the converter. The control scheme analysis is carried out by linearizing the small-signal model of the proposed converter to form the output current transfer functions. This transfer function will be analyzed by using phase and gain margin approach to obtain the control parameters (Kp, Ki, and Ti). Simulation and experiment results are included to show the validity of the proposed concept.</span>

Model-based feedforward control for suppressing torque oscillation of electric power steering system

Oscillation suppression is essential for the stability design of electric power steering (EPS) systems. The stability controller module in EPS controller is the key to solve the stability control problem of EPS system. This paper proposes a new method of stability analysis and stability controller module design for EPS systems. Furthermore, the dynamic characteristics of the EPS system are analyzed, and two critical factors on the resulting EPS stability, that is, large assist and variable assist gain are investigated experimentally. The transfer function from steering torque to sensor torque is redefined. A new transfer function is proposed for measuring the effect of variable assist gain on system performance. Based on the above factors and transfer functions, constraints on the stability controller design are proposed. Then the optimal parameters in the controller are obtained by maximizing an objective function including phase margin, gain margin, and crossover frequency. It is concluded from simulations and bench tests that the proposed stability controller can significantly reduce the torque oscillation of the EPS system.

Turbojet Thrust Augmentation through a Variable Exhaust Nozzle with Active Disturbance Rejection Control

Turbojets require variable exhaust nozzles to fit high-demanding applications; however, few reports on nozzle control are available. The purpose of this paper is to investigate the possible advantages of an exhaust gas control through a variable exhaust nozzle. The control design method combines successful linear active disturbance rejection control (LADRC) capabilities with a loop shaping controller (LSC) to: (i) allow designing the closed-loop characteristics in terms of gain margin, phase margin and bandwidth, and (ii) increase the LSC disturbance rejection capabilities with an extended state observer. A representation of the nozzle dynamics is obtained from first principles and adapted to achieve a stream-velocity-based control loop. The results show that the resulting controller allows improving the expansion of the exhaust gas to the ambient pressure for the whole operating range of the turbojet, increasing the estimated thrust by 14.23% during the tests with experimental data.

Design of voltage and current controller parameters using small signal model-based pole-zero cancellation method for improved transient response in microgrids

Microgrids are supposed to provide stable power for seamless utility-grid interaction under all conditions as stated by IEEE-1547 standard. But, the use of power electronic inverter makes the microgrid sensitive to transients than synchronous generator-based plants. This degrades the voltage/frequency responses during transients, which can lead to transient stability problem if not controlled properly. Hence, the design of effective closed-loop voltage and current (V/I) controllers is highly desired to control the inverter output against the disturbances. The V/I controllers are based on PI (proportional-cum-integral) formulas. Thus, the effectiveness of V/I controllers relies on how accurate that their gain parameters are tuned. Many PI-tuning methods have been developed in the literature, but, it is yet difficult to identify a suitable method for an application. Also, only a few researchers have focused on the microgrids due to the complexity involved in its controller design by the presence of V/I cascaded dual-loop. Hence, to address this problem, this paper proposes a novel way of designing V/I controller parameters by using pole-zero cancellation method. This method is implemented by deriving the microgrid’s small-signal model. This improves the transient response through reduced system order and/or alleviated sluggish/marginal-stable/unstable poles by adding zeros at same places where those poles are laid, to in effect cancel them. The efficacy of the proposed method over existing methods is assessed by plotting frequency and voltage responses under different test conditions. From the simulation results, it is witnessed that the proposed method relatively improved the transient characteristics of microgrids. Article Highlights Analyzes the applicability of conventional PI tuning methods for microgrid controllers’ design. Proposes a novel small signal model based pole-zero cancellation method for the design of microgrid controllers. Enhances the gain margin, which improves the stabilization capacity of the system when subjected to disturbances. Improves the transient behavior of frequency and voltage responses, which ensure the safety of sensitive loads.

Synthesis of a High-Precision Missile Homing System with an Permissible Stability Margin of the Normal Acceleration Stabilization System

The proportional guidance method-based missile homing systems (MHS) have been widely used the real-world environments. In these systems, in order to destroy the targets at different altitudes, a normal acceleration stabilization system (NASS) is often utilized. Therefore, the MHS are complex and the synthesis of these systems are a complex task. However, it is necessary to synthesize NASS during the synthesis of the MHS. To simplify the synthesis process, a linear model of the NASS is used. In addition, we make use of the available commands in Control System Toolbox in MATLAB. Because the Toolbox has the commands to describe the transfer function, determine the stability gain margin, and the values of the transient respond of the linear automatic systems. Thus, this article presents two methods for synthesizing the missile homing systems, including (i) a method for synthesizing the MHS while ensuring the permissible stability gain margin of the NASS, and (ii) a method for synthesizing the MHS while ensuring the permissible stability margin of the NASS by overshoot. These techniques are very easy to implement using MATLAB commands. The synthesis of the proposed MHS is carried out by the parametric optimization method. To validate the performance of the proposed techniques, we compare them withthe MHS synthesized by ensuring the stability margin of the NASS bythe oscillation index. The results show that, two our proposed methods and the existing method provide the same results in terms of high-precision. Nevertheless, the proposed methods are simple and faster than the conventional method. The article also investigates the effect of gravity, longitudinal acceleration of the rocket, andblinding of the homing head on the accuracy of the synthesized MHS. The results illustrate that they have a little effect on its accuracy.

Design and implementation of decoupled periodic control scheme for a laboratory-based quadruple-tank process

It is well known that linear time-invariant controllers fail to provide desired robustness margins (e.g. gain margin, phase margin) for plants with non-minimum phase zeros. Attempts have been made in literature to alleviate this problem using high-frequency periodic controllers. But because of high frequency in nature, real-time implementation of these controllers is very challenging. In fact, no practical applications of such controllers for multivariable plants have been reported in literature till date. This article considers a laboratory-based, two-input–two-output, quadruple-tank process with a non-minimum phase zero for real-time implementation of the above periodic controller. To design the controller, first, a minimal pre-compensator is used to decouple the plant in open loop. Then the resulting single-input–single-output units are compensated using periodic controllers. It is shown through simulations and real-time experiments that owing to arbitrary loop-zero placement capability of periodic controllers, the above decoupled periodic control scheme provides much improved robustness against multi-channel output gain variations as compared to its linear time-invariant counterpart. It is also shown that in spite of this improved robustness, the nominal performances such as tracking and disturbance attenuation remain almost the same. A comparison with [Formula: see text]-linear time-invariant controllers is also carried out to show superiority of the proposed scheme.

Robust Compensating Function Scheme for Adequate Electrical Power System Stabilization

This work centers on robust compensating function scheme for adequate electrical power system stabilization. There has been high level of disturbances in the power line and lack of adequate compensation technique to cancel the effects of the resultant instability which has caused power failures. The problem was addressed by the consideration of disturbances in the power line during the design of the compensating function for the improvement of the power system performance and stability. H-Infinity synthesis robust compensating function design method was used to design an adequate compensator that can improve the performance and stability of the power system. From the results, the H-infinity Synthesis Controlled Generating Plant (HCGP) recorded an overshoot of 0%, settling time of 1.04 seconds, tracking error of 0dB, gain margin of 21.7dB and phase margin of 79.6 degrees. The simulation was repeated by varying the value to k to -0.3, and the generating plant produced same results. This shows that the system can maintain performance and stability equilibrium even when there is change in its parameters. Since the HCGP satisfied the performance and stability robustness, therefore it was concluded that power system robust compensating function scheme for improved performance and stability robustness was achieved using H-Infinity synthesis method.