Closed-loop Control Technique Research Articles

Real-time analysis of voltage and frequency regulation of self-excited induction generator based micro hydro plant using generalized impedance controller

– The self-excited induction generator (SEIG) is well accepted for application in micro hydropower plants. However, in the edge-of-grid application it exhibits a limitation in its capacity to sustain the desired terminal voltage along with the frequency of variations in the prime mover's speed and load. Terminal voltage and frequency regulation are significant concerns for such schemes, and many such techniques are available to regulate the same. This paper presents a closed-loop control technique based on a generalized impedance controller (GIC) responsible for the impedance-controlled functioning of the pulse width variation voltage source converter (PWM-VSC) to regulate frequency and terminal voltage of machine with various loading conditions. A coupling transformer is connected between GIC and SEIG, and the ratings of GIC and transformer should be the same as SEIG, as GIC must compensate for the entire SEIG output. Three phase, 2.2 kW, 415 V, 4.8 A, 50 Hz SEIG, and a three IGBT-based voltage-sourced inverter with coupling transformer, are modelled in MATLAB environment. SEIG frequency and voltage effects in response to the GIC modulation index and phase angle are investigated in the real-time environment using the OPAL-RT (ver. OP4510) environment. The voltage and frequency are controlled using the proposed SEIG-GIC scheme, and the simulation results achieved from MATLAB/Simulink were validated with real-time observations.

Real-Time Implementation for the Robust Controller of the Switched Boost Inverter within an Autonomous Modified Nanogrid

SBI stands for switched-boost inverter and is a single-stage power converter used to connect low-power sources, such as solar photovoltaic (PV) arrays within a modified nanogrid, to loads. Despite its many benefits, such as the fact that it does not require expensive sophisticated dead-time circuitry, its duty ratio is limited to between 0 and 0.5. As a result, this publication is a contribution towards improving the SBI's performance for use in a modified nanogrid. Furthermore, it also presents a revolutionary strategy for a simple closed-loop control technique that overcomes the majority of inverter shortcomings and system nonlinearity. The suggested robust controller uses a metaheuristic optimization technique, called gorilla troops optimization (GTO), to optimize the performance of this controller. The robustness of the suggested controller is tested against the sudden change of the nanogrid input voltage (i.e., PV-voltage), modulation index of the inverter, and the step-change in DC-link output voltage of the inverter. The test results obtained from Matlab/Simulink software are compared with particle swarm optimization (PSO) – as another optimization algorithm. Furthermore, the proposed system is experimentally implemented with OPAL RT-4510v real-time hardware in the loop (HIL), rapid control prototyping, OP-8660 HIL controller and data acquisition platform.

An Active Power Decoupling-Integrated Reduced-Switch Current-Fed Switched Inverter

In recent literature, high-gain dc–ac inverters are employed in grid-connected photovoltaic (PV) systems. These inverters can have several features, such as shoot-through immunization and buck/boost capabilities achieving a wide range of operations with reliability and minimum distortion. One such example is the single-phase reduced-switch current-fed switched inverter (RSCFSI). This article proposes the enhanced boost control-based pulsewidth modulation (EBC-PWM) strategy for RSCFSI to improve the inverter’s dc–ac gain. Being a single-phase inverter, RSCFSI suffers from the double-line frequency ripple problem. However, a low-frequency (LF) ripple analysis reveals that the RSCFSI is also plagued with fundamental frequency ripple, which poses additional challenges for the active power decoupling (APD) integration and corresponding closed-loop controllers. Although both LF ripples can be alleviated using markedly large passive elements, the power density and reliability of the inverter worsen. In this article, an APD-integrated RSCFSI (APDRSCFSI) is introduced as a solution that deflects the aforementioned LF ripple energy to an auxiliary capacitor without adding more active switches. As a result, the inverter can employ smaller passive elements. In addition, the EBC-PWM strategy is also extended for APDRSCFSI, improving its dc–ac voltage gain and voltage stress. A closed-loop control technique that combines output voltage control and APD functionality is also illustrated. A hardware prototype is used to corroborate the advantages of APDRSCFSI.

An active swing suppression control scheme of overhead cranes based on input shaping model predictive control

An input shaper-based model predictive control scheme is proposed for an overhead crane to suppress the swing of the payload. A control-oriented mathematical model of the crane is firstly derived based on the small angle hypothesis. Furthermore, three kinds of commonly used shapers are discussed and a zero vibration derivative shaper is selected for the crane. Then, a model predictive swing suppression controller is designed for the crane based on the selected shaper. Constraints on the control input and its slew rate are respected. Besides, the constraint on the swing angle of the payload is also respected as an output constraint. The constrained solution is given in the form of standard quadratic programming. The designed control scheme combines open-loop and closed-loop control techniques, achieving accurate positioning of the trolley and good swing suppression of the payload. A series of simulation demonstrates the effectiveness and advantages of the proposed scheme.

Non Linear Control System for Humanoid Robot to Perform Body Language Movements.

In social robotics, especially with regard to direct interactions between robots and humans, the robotic movements of the body, arms and head must make an adequate displacement to guarantee an adequate interaction, both from a functional and social point of view. To achieve this, the use of closed-loop control techniques that consider the complex nonlinear dynamics and disturbances inherent in these systems is required. In this paper, an implementation of a nonlinear controller for the tracking of trajectories and a profile of speeds that execute the movements of the arms and head of a humanoid robot based on the mathematical model is proposed. First, the design and implementation of the arms and head are initially presented, then the mathematical model via kinematic and dynamic analysis was performed. With the above, the design of nonlinear controllers such as nonlinear proportional derivative control with gravity compensation, Backstepping control, Sliding Mode control and the application of each of them to the robotic system are presented. A comparative analysis based on a frequency analysis, the efficiency in polynomial trajectories and the implementation requirements allowed selecting the non-linear Backstepping control technique to be implemented. Then, for the implementation, a centralized control architecture is considered, which uses a central microcontroller in the external loop and an internal microcontroller (as internal loop) for each of the actuators. With the above, the selected controller was validated through experiments performed in real time on the implemented humanoid robot, demonstrating proper path tracking of established trajectories for performing body language movements.

Adaptive Support Ventilation – A way different from traditional ventilation

Adaptive support ventilation (ASV) is a dual control mode of ventilation, which uses a closed loop control technique. This mode delivers controlled, time triggered and time cycled breaths when a patient is not breathing. If the patient has spontaneous breaths, it delivers flow cycled breaths and allows the patient to trigger and breathe spontaneously, either in between the controlled breaths or fully spontaneously. This mode is pressure limited for control, assist control and spontaneous breath. The pressure will vary depending on the target tidal volume and uses autoflow throughout the cycle. IntelliVent(R) is a closed loop mode of ventilation, an advance over the ASV mode where the ventilator automatically adjusts settings and optimises ventilation depending on the target settings and physiological information from the patient.

Performance Analysis and Comparison of Non-Inverting Buck-Boost Converter Using PI, OCC, and Hybrid OCC-PI Control

The study compares and analyses the performance of the one-cycle control (OCC), hybrid one-cycle-proportional integral control (OCC-PI), and the conventional PI control method applied to the non-inverting buck-boost converter. The hybrid OCC-PI control method combines the OCC and PI control techniques to provide a hybrid non-linear closed-loop control technique for regulating the buck-boost converter. The MATLAB/Simulink equivalent system model was simulated with design parameter variations using a wide input voltage range of 9 – 36 V, a nominal output voltage of 28 V, and a fixed switching frequency of 250 kHz to validate the control response speed, reliability, and robustness of the proposed control technique. The simulation results due to input voltage, output voltage, and load variations were carried out whiles recording the settling time, overshoots, efficiency, output voltage, and inductor current ripples due to each applied control technique. The simulation results indicated that the Hybrid OCC-PI control provides better response speed and a lower output voltage overshoot relative to the PI. It also provides better reference voltage tracking compared to the OCC control method.

Hybrid MLI Topology Using Open-End Windings for Active Power Filter Applications

Different multilevel converter topologies have been presented for achieving more output voltage steps, hence improving system performance and lowering costs. In this paper, a hybrid multilevel inverter (MLI) topology is proposed for active-power-filter applications. The proposed MLI is a combination of two standard topologies: the cascaded H-bridge and the three-phase cascaded voltage source inverter. This configuration enhances the voltage levels of the proposed MLI while using fewer switches than typical MLI topologies. The proposed MLI was developed in the MATLAB/Simulink environment, and a closed-loop control technique was used to achieve a unity power factor connection of the PV modules to the grid, as well as to compensate for harmonics caused by nonlinear loads. To demonstrate that the configuration was working correctly and that the control was precise, the proposed MLI was constructed in a laboratory. A MicroLabBox real-time controller handled data acquisition and switch gating. The proposed topology was experimentally connected to the grid and the MLI was experimentally used as an active power filter to compensate for the harmonics generated due to nonlinear loads. This control technique was able to generating a sinusoidal grid current that was in phase with the grid voltage, and the grid current’s total harmonic distortion was within acceptable limits. To validate the practicability of the proposed MLI, both simulation and experimental results are presented.

An improved platform for cultured neuronal network electrophysiology: multichannel optogenetics integrated with MEAs.

Cultured neuronal networks (CNNs) are powerful tools for studying how neuronal representation and adaptation emerge in networks of controlled populations of neurons. To ensure the interaction of a CNN and an artificial setting, reliable operation in both open and closed loops should be provided. In this study, we integrated optogenetic stimulation with microelectrode array (MEA) recordings using a digital micromirror device and developed an improved research tool with a 64-channel interface for neuronal network control and data acquisition. We determined the ideal stimulation parameters including light intensity, frequency, and duty cycle for our configuration. This resulted in robust and reproducible neuronal responses. We also demonstrated both open and closed loop configurations in the new platform involving multiple bidirectional channels. Unlike previous approaches that combined optogenetic stimulation and MEA recordings, we did not use binary grid patterns, but assigned an adjustable-size, non-binary optical spot to each electrode. This approach allowed simultaneous use of multiple input-output channels and facilitated adaptation of the stimulation parameters. Hence, we advanced a 64-channel interface in that each channel can be controlled individually in both directions simultaneously without any interference or interrupts. The presented setup meets the requirements of research in neuronal plasticity, network encoding and representation, closed-loop control of firing rate and synchronization. Researchers who develop closed-loop control techniques and adaptive stimulation strategies for network activity will benefit much from this novel setup.

Adaptive under-actuated control for capacitive micro-machined ultrasonic transducer based on an accurate nonlinear modeling

A capacitive micromachined ultrasonic transducer (CMUT) due to many benefits is being considered as an imaging and therapeutic technology recently. The critical challenge is to stabilize the system beyond the pull-in voltage considering imposed perturbations. The CMUT system, on the other hand, has a low range of movement and it is intrinsically unstable, which can result in a pull-in phenomenon. Consequently, in order to use the CMUT systems in a variety of medical applications that require high tuning ratio, a closed-loop control technique has been designed for these systems aims at increasing the maximum capacitance and enhancing tunability as well. In this study, using the closed-loop control, the resistance of micro-plate against the pull-in phenomenon has been examined. Also, in the description of the system a more accurate nonlinear modeling has been considered in the presence of an under-actuated sliding model control strategy with finite convergence time. Besides, adaptive protocols with unknown upper bounds have been designed to compensate the effects of uncertainty, unmodeled dynamics and external disturbances. The performance of controller in terms of improving output pressure, stabilizing the CMUT and its robustness to imposed perturbations have been investigated. Finally, numerical simulations are presented to verify the usefulness and applicability of the proposed control strategy.

Soft switched DC-DC converter for hybrid power generation photo voltaic panels using fuzzy logic controller

Maximum Power Point Tracking (MPPT) with a Z source cascaded inverter based on Fuzzy Logic Control (FLC) is proposed in this research for a hybrid photo-voltaic (PV) and wind turbine (WT) system. In the absence of PV or WT power generation, the suggested system offers an uninterrupted power supply to the grid. PV functions as a current source and creates maximum power at maximum power point (MPP), supplying just the deficiency power. This FLC-integrated technique minimises the complexity of typical PID controllers while also improving overall performance. To reduce switching losses, current, and voltage switching stress, a traditional dc/dc boost converter with soft switching has been introduced. To reduce switching stress, a boost converter with zero voltage switching is used. This research focuses on a Zero Voltage Switching (ZVS) technique that uses fuzzy logic control to meet the PV system's MPPT and output voltage regulation requirements. All these PV and wind hybrid systems, a Z-Source network, and a five-level cascaded inverter are part of the proposed topology. The advantages of a Z-source inverter outweigh the disadvantages of a traditional voltage-source inverter. The required stepped output voltage is achieved by boosting the DC link voltage from the PV system using a shoot through state. The suggested system has been simulated with MATLAB/SIMULINK, and the closed loop control technique has been investigated and verified.

Ant colony optimization algorithm and fuzzy logic for switched reluctance generator control

<abstract> <p>This article discusses two methods to control the output voltage of switched reluctance generators (SRGs) used in wind generator systems. To reduce the ripple of the SRG output voltage, a closed-loop voltage control technique has been designed. In the first method, a proportional-integral (PI) controller is used. The parameters of the PI controller are tuned based on the voltage variation. The SRG is generally characterized by strong nonlinearities. However, finding appropriate values for the PI controller is not an easy task. To overcome this problem and simplify the process of tuning the PI controller parameters, a solution based on the ant colony optimization algorithm (ACO) was developed. To settle the PI parameters, several cost functions are used in the implementation of the ACO algorithm. To control the SRG output voltage, a second method was developed based on the fuzzy logic controller. Unlike several previous works, the proposed methods, ACO and fuzzy logic control, are easy to implement and can solve numerous optimization problems. To check the best approach, a comparison between the two methods was performed. Finally, to show the effectiveness of this study, we present examples of simulations that entail the use of a three-phase SRG with a 12/8 structure and SIMULINK tools.</p> </abstract>

Dynamic control for LMD processes using sensor fusion and edge computing

The quality of an LMD manufactured object highly depends on different process parameters such as the speed of powder deposition, the applied laser power, the powder feed rate, and other physical parameters such as the substrate temperature, resulting in a complex process. Consequently, applying corrections to the process parameters can be critical to improving the properties of the manufactured part. Some control approaches rely on open-loop techniques that use physical models and expert knowledge to adjust the tool path program in advance to compensate for deviations from the theoretical 3D model. Other approaches apply closed-loop control techniques to either control the melt pool during the process or adjust the tool path between layer depositions. This work presents a closed-loop control algorithm that dynamically controls three critical process parameters: the melt pool size, deposition speed, and standoff distance, combining data from a laser line profiler and a high-speed infrared camera.

Is It Possible to Obtain Benefits by Reducing the Contribution of the Digital Signal Processing Techniques to the Control of the Active Power Filter?

This paper presents a simple yet efficient control method for active power filters that can be used to improve power quality. Applying this method can open the way towards limiting the hardware and computational expenditure, which are needed for control of the active filter, while maintaining its required performance. The method is based on the indirect approach of obtaining reference signals combined with the closed-loop current control technique. Monitoring of changes of energy stored in reactance elements of the active filter is the base for obtaining reference signals for compensation. The active filter can perform classical compensation and, additionally, can perform some extra functionality for managing of active power in the system. In particular, it can stabilize the supplying source power, enable energy exchange between loads connected on DC and AC sides of the active filter, and—in a case of generating loads—enable their energy storage and redistribution amongst consuming loads. The presented method can be useful for voltage-source as current-source inverter based active filters, and for DC systems as well as for AC single- or three-phase ones.

High-bandwidth nanopositioning via active control of system resonance

Typically, the achievable positioning bandwidth for piezo-actuated nanopositioners is severely limited by the first, lightly-damped resonance. To overcome this issue, a variety of open- and closed-loop control techniques that commonly combine damping and tracking actions, have been reported in literature. However, in almost all these cases, the achievable closed-loop bandwidth is still limited by the original open-loop resonant frequency of the respective positioning axis. Shifting this resonance to a higher frequency would undoubtedly result in a wider bandwidth. However, such a shift typically entails a major mechanical redesign of the nanopositioner. The integral resonant control (IRC) has been reported earlier to demonstrate the significant performance enhancement, robustness to parameter uncertainty, guaranteed stability and design flexibility it affords. To further exploit the IRC scheme’s capabilities, this paper presents a method of actively shifting the resonant frequency of a nanopositioner’s axis, thereby delivering a wider closed-loop positioning bandwidth when controlled with the IRC scheme. The IRC damping control is augmented with a standard integral tracking controller to improve positioning accuracy. And both damping and tracking control parameters are analytically optimized to result in a Butterworth Filter mimicking pole-placement—maximally flat passband response. Experiments are conducted on a nanopositioner’s axis with an open-loop resonance at 508 Hz. It is shown that by employing the active resonance shifting, the closed-loop positioning bandwidth is increased from 73 to 576 Hz. Consequently, the root-mean-square tracking errors for a 100 Hz triangular trajectory are reduced by 93%.

Control of Brushless DC Motor by Voice Command Implementing Machine Learning

This paper deals with the speed control of BLDC motor drive in a closed loop control technique. Node-MCU is used as a microcontroller where machine learning program is implemented. According to the desired speed given by the user via voice command, the motor will run at the exact speed. Instead of using speed sensor, the stator back - emf is used to estimate the rotor speed.

Design and closed-loop control of a piezoelectric actuator

Piezoelectric elements can produce a high displacement resolution with high force outputs but exhibits large hysteresis nonlinearities. An efficient way to compensate for nonlinearities is using a closed loop control technique. Another limitation for many applications is their relatively short displacement ranges. One method to avoid the above-mentioned shortcoming is to integrate a piezoelectric element with a mechanical displacement amplifier based on a compliant mechanism. This paper presents the design and closed-loop control of such a piezoelectric actuator. Using the integrated strain gauge sensors, a PI controller was designed and tested.

Modelling and control strategies for a motorized wheelchair with hybrid locomotion systems

Several kinematic and dynamic models of conventional motorized wheelchairs in the literature presume the wheelchair movement only on flat surfaces, disregarding the effects of gravitational forces and rolling friction. In addition, there are no many studies clearly describing how the dynamic properties of a conventional wheelchair and stair-climbing wheelchair with a track mechanism are formulated. However, the design of a good controller generally involves the formulation of a comprehensive wheelchair model. This work contributes to the modelling of the motorized wheelchair with hybrid locomotion systems (MWHLSs), which have wheel and track mechanisms to move the wheelchair, regarding the formulation of kinematic and dynamic models for each locomotion system, considering the effects of gravitational forces and rolling friction, on flat and inclined surfaces and climbing stairs. From the mathematical model for each locomotion system, the gearmotor torque control is used, since the torque provides smooth and precise driving. Thus, the open-loop and closed-loop control techniques, such as control Lyapunov function, Backstepping control, and Proportional-Integral-Derivative controller, are designed due to their well-known characteristics. The robustness analysis of these controllers, taking into account the occurrence of external disturbances, indicates which one best assists wheelchair users, providing a safer and more efficient navigation with the MWHLS.

Cooperative Automatic Control for the Canopy Posture of a Four-Leg Hydraulic Support

The contact state between the canopy and roof of a hydraulic support considerably influences the bearing capacity and stability of the support. To ensure a secure contact between the canopy and roof in the setting stage, this paper proposes a cooperative double closed-loop automatic control technique for the canopy posture, with MATLAB used to simulate the canopy posture under different roof conditions. First, a cooperative double closed-loop automatic control model was established. Second, the method to determine the target value of the canopy posture and constraint conditions of the rising process were formulated. Finally, by simulating the canopy posture under three roof conditions, the response curve of the canopy posture and the leg length were obtained. The results show that the front and rear legs can rise through either synchronous or asynchronous coordination, and the canopy posture can approach the target value. The presented findings can guide the realization of the automatic control of the canopy posture of hydraulic support.

Closed‐loop control of a single‐stage switched‐boost inverter in modified DC‐interconnected nanogrids

Switched-boost inverter (SBI) is a single-stage power converter suitable for interfacing between photovoltaic (PV) arrays and loads. Although, it has many advantages such as it's not requiring an expensive complex dead-time circuitry, yet its duty ratio is limited between 0 and 0.5. This means that it has some difficulties in increasing both the DC-link output voltage and its AC-output voltage. So, most researchers proposed it for low-voltage power applications or using with step-up transformers. Accordingly, this study contributes towards improving the performance of the SBI for being used in the modified nanogrid within an open energy system. It introduces a novel approach closed-loop control technique to overcome most of the inverter drawbacks. Also, it enhances both the DC-link and the transformer-less rated AC output voltages to a sufficient value suitable for feeding domestic loads. And in the same time, the proposed robust controller utilizes a hysteresis band for balancing between voltage stability and PV-maximum power achievement. This research also includes a more sophisticated fast-charging slow-discharging control strategy for the battery energy management system that depends on a bidirectional buck-boost converter. Test results ensure the robustness of the proposed controller against sensitivity, nonlinearity, and time-variant parameters of the overall system.