Simple Control Algorithm Research Articles

Study and Analysis of New Three-Phase Modular Multilevel Inverter

This paper proposes a new three-phase modular multilevel inverter ( MMLI ). The proposed inverter consists of repeated modular primary cells that are connected in series configuration. Therefore, the proposed topology can be extended to get more output voltage levels by adding additional cells without increasing voltage stresses across power switches. Both sinusoidal pulsewidth modulation ( SPWM ) and staircase modulation are successfully applied to the proposed inverter. The proposed inverter features many advantages such as reduced number of semiconductor power switches, driver circuits, dc-voltage sources, simplified control algorithm, and reduced voltage stresses across the switches independent of output voltage level. Furthermore, the performance of the proposed inverter is studied under both open-loop and closed-loop operations for highly inductive load. Beside the obtained simulation results, a laboratory prototype has been carried out and tested to verify the control techniques and performances of the topology. Simulation and experimental results are compared together to highlight the similarity and consistence of them.

Multi-flow management for mobile data offloading

Abstract Cellular networks are facing explosive growth of mobile data traffic due to the proliferation of smart devices and traffic-intensive applications. As a cost-effective solution, delayed Wi-Fi offloading was introduced to shift the delay-tolerant traffic from cellular to Wi-Fi networks by trading additional delays. Our paper studies a multi-flow rate control problem where each flow has different traffic load and a deadline. To maximize user satisfaction defined as offloading efficiency minus disutility caused by deadline violation, we propose a dynamic programming-based rate control algorithm. Moreover, to reduce the computation and memory, we propose a simple threshold-based rate control algorithm.

A simple control algorithm for controlling biped dynamic walking with stopping ability based on the footed inverted pendulum model

In biped walking, dynamic balance ability is an important evaluation index. Zero-moment-point-based trajectory control is a common method for biped dynamic walking, but it requires complex control mechanisms that limit its applications. With the help of passive dynamics, the biped walking based on the inverted pendulum model can achieve dynamic walking in a simple way; however, it has no stopping ability, which is necessary for practical use. To solve this problem, this article proposes a footed inverted pendulum model and develops a simple three-part decomposition control algorithm for controlling biped dynamic walking based on the model. In the control algorithm, the biped walking is decomposed into three separate control parts: body posture, body height, and body velocity. Body posture is controlled by the stance hip, body height is controlled by the stance knee, and body velocity is controlled by the stance ankle and swing foot placement simultaneously. A simulation is presented to analyze the foot’s effect on the inverted pendulum model. Two hardware experiments exploring velocity control and balance are described, with the results showing that the biped can achieve dynamic walking with stopping ability by using the simple control algorithm based on the footed inverted pendulum model.

Comparison of Active Power Decoupling Methods for High-Power-Density Single-Phase Inverters Using Wide-Bandgap FETs for Google Little Box Challenge

This paper presents a comparison between mitigation techniques for double line frequency ripples in single-phase microinverters based on wide-bandgap FETs. A topology based on an auxiliary dc–ac stage is adopted based on optimizing both power density and efficiency to achieve the pressing needs of the next generation of microinverters as announced by Google’s little box challenge. An accurate yet simple control algorithm is proposed that provides a ripple-free dc current. Experimental results demonstrate the effectiveness of the presented topology and control algorithm in achieving a high-power-density microinverter rated at 2 kW.

SOFC Anode Process Characterization By Means of a Novel Spot-Sampling Set-up for in-Operando Gas Analysis

The development and operation of an innovative experimental setup is presented for in-depth, in-operando characterization of anode processes of Solid Oxide Fuel Cells.The idea behind this project is to realize a setup enabling the measurement of temperature and gas compositions using eleven points of sampling distributed over the anode surface. Simultaneous temperature measurement and gas chromatography are employed to detect the variation of thermodynamic and chemical conditions across the anode surface in steady state and in real time. The particular location of each sampling point is chosen in such a way as to minimize interference in the flow pattern across the anode but maximizing the spatial information of the measurements taken. Thus, it is possible to investigate the evolution of chemical reactions occurring during the operation of the cell, identified with a spatial resolution covering the whole surface of the anode in order to distinguish edge effects from bulk processes. Sampling settings are tailored to analyse representative specimens of anode gas without altering local conditions. Moreover, the novel housing allows for full simultaneous (bulk) electrochemical characterization through polarization curves and electrochemical impedance spectroscopy (EIS), maximizing the data output from a given experiment without significantly affecting the cell response during the characterization.This experimental setup is particularly important for the direct fuelling of SOFCs with natural gas, biogas or syngas, where the dynamic processes of internal reforming can create severe local gradients of temperature and gas compositions, inducing stresses and possible carbon deposition. Single cell tests have been carried out on intermediate-temperature, commercial SOFCs fed with simple hydrogen and selected syngas compositions to assess the thermochemical response of the SOFC at different current densities and create a detailed spatial mapping of critical hotspots correlated with operating conditions and inlet gas compositions. It is thus possible to identify areas within the operational space that are conducive to better uniformity of conditions, presumed to enhance SOFC durability, allowing to provide recommendations for fuel pre-conditioning processes as well as SOFC operation modes. Ultimately, it is envisaged to establish simplified but effective control algorithms based upon the correlation of the detailed, real-time spatial mapping with key parameters that are easily monitored in a real SOFC system.Experimental data will be useful to investigate phenomena occurring on the cell plane also with the help of a model based on finite element method that can simulate locally the behavior of the cell in order to validate the experimental map of temperature and composition of gases on the cell.

Development of Autonomous Robot with Simple Navigation System for Tsukuba Challenge 2015

[abstFig src='/00280004/01.jpg' width='300' text='MercuryMega (SICKLaser-Model)' ] This paper introduces the robot that was developed for Tsukuba Challenge 2015. One of the team’s design goals was to implement a simple sensor configuration and control algorithm. For example, the robot’s laser range finders (LRF) were of fixed type, and localization was accomplished using only a single LRF and no other sensor. Environment map matching was achieved using an algorithm that processed pyramid images using binary image processing to reduce computational cost. Shape information from the LRF and color information from a camera were combined to detect a signboard placed near a person. During an actual test in rainy weather, the robot ran the entire course and, detected two, out of a possible four, number of target persons.

Selection and implementation of optimal magnetorheological brake design for a variable impedance exoskeleton robot joint

Next-generation exoskeleton and humanoid robots are expected to behave similar to the human neuro-muscular system to perform stable, flexible, and biomimetic movements. To achieve this goal, the variable stiffness actuators have been widely used in various robots. Using variable damping actuators along with variable stiffness actuators will be extremely beneficial for wide range of stable movements. Magnetorheological (MR) brakes are one of the most promising electromagnetic structures that can provide such variable damping in a relatively small actuator volume. In this paper, we focused on the design, characterization, selection and implementation of T-shaped, inner coil and outer coil multi-pole MR brakes to the ankle of an exoskeleton robot. Analytical models are developed using the magnetic circuit analysis to determine the braking torque. Then, magnetic finite element models are developed and coupled with an optimization algorithm to determine the optimal set of parameters of each MR brake design. Prototypes are manufactured in same size and tested experimentally to characterize the actuators’ torque-to-volume ratio, transient response, hysteresis, torque tracking, energy consumption, and damping performances. The performance comparison of the brakes showed T-shaped multi-pole MR brake design has superior characteristics compared to two other designs. Therefore, T-shaped multi-pole MR brake design is coupled with a variable stiffness actuator and implemented in an ankle joint of an exoskeleton robot and experimentally tested. The results show that the developed new hybrid robot joint is capable of stable movement with a simple control algorithm by changing its stiffness and damping independently.

An efficient artificial bee colony algorithm with application to nonlinear predictive control

In this paper a constrained nonlinear predictive control algorithm, that uses the artificial bee colony (ABC) algorithm to solve the optimization problem, is proposed. The main objective is to derive a simple and efficient control algorithm that can solve the nonlinear constrained optimization problem with minimal computational time. Indeed, a modified version, enhancing the exploring and the exploitation capabilities, of the ABC algorithm is proposed and used to design a nonlinear constrained predictive controller. This version allows addressing the premature and the slow convergence drawbacks of the standard ABC algorithm, using a modified search equation, a well-known organized distribution mechanism for the initial population and a new equation for the limit parameter. A convergence statistical analysis of the proposed algorithm, using some well-known benchmark functions is presented and compared with several other variants of the ABC algorithm. To demonstrate the efficiency of the proposed algorithm in solving engineering problems, the constrained nonlinear predictive control of the model of a Multi-Input Multi-Output industrial boiler is considered. The control performances of the proposed ABC algorithm-based controller are also compared to those obtained using some variants of the ABC algorithms.

A Single-Sensor-Based MPPT Controller for Wind-Driven Induction Generators Supplying DC Microgrid

In this paper, a simple method of tracking the maximum power (MP) available in the wind energy conversion system (WECS) for dc microgrid application is proposed. A three-phase diode bridge rectifier along with a dc–dc converter has been employed between the terminals of a wind-driven induction generator and dc microgrid. Induction generator is being operated in self-excited mode with excitation capacitor at stator. The output current of the dc–dc converter, i.e., dc-grid current is considered as a control variable to track the MP in the proposed WECS. Thus, the proposed algorithm for maximum power point tracking (MPPT) is independent of the machine and wind-turbine parameters. This algorithm has been implemented using dsPIC30F4011 controller. Furthermore, a method has been developed for determining the duty ratio of the dc–dc converter for operating the proposed system in MPPT condition using wind-turbine characteristics, steady-state equivalent circuit of a induction generator, and power balance in power converters. Circuit simplicity and simple control algorithm are the major advantages of the proposed configuration for supplying power to the dc microgrid from the proposed small-scale WECS. The successful working of the proposed algorithm for MPPT has been demonstrated with extensive experimental results along with the simulated values.

Development of a Control and Vision Interface for an AR.Drone

The AR.Drone is a remote controlled quadcopter which is low cost, and readily available for consumers. Therefore it represents a simple test-bed on which control and vision research may be conducted. However, interfacing with the AR.Drone can be a challenge for new researchers as the AR.Drone's application programming interface (API) is built on low-level, bit-wise, C instructions. Therefore, this paper will demonstrate the use of an additional layer of abstraction on the AR.Drone’s API via the Robot Operating System (ROS). Using ROS, the construction of a high-level graphical user interface (GUI) will be demonstrated, with the explicit aim of assisting new researchers in developing simple control and vision algorithms to interface with the AR.Drone. The GUI, formally known as the Control and Vision Interface (CVI) is currently used to research and develop computer vision, simultaneous localisation and mapping (SLAM), and path planning algorithms by a number of postgraduate and undergraduate students at the school of Aeronautical, Mechanical, and Mechatronics Engineering (AMME) in The University of Sydney.

A dynamic trajectory control algorithm for improving the communication throughput and delay in UAV-aided networks

Recently, the UAS has been extensively exploited for data collection from remote and dangerous or inaccessible areas. While most of its existing applications have been directed toward surveillance and monitoring tasks, the UAS can play a significant role as a communication network facilitator. For example, the UAS may effectively extend communication capability to disaster-affected people (who have lost cellular and Internet communication infrastructures on the ground) by quickly constructing a communication relay system among a number of UAVs. However, the distance between the centers of trajectories of two neighboring UAVs, referred to as IUD, plays an important role in the communication delay and throughput. For instance, the communication delay increases rapidly while the throughput is degraded when the IUD increases. In order to address this issue, in this article, we propose a simple but effective dynamic trajectory control algorithm for UAVs. Our proposed algorithm considers that UAVs with queue occupancy above a threshold are experiencing congestion resulting in communication delay. To alleviate the congestion at UAVs, our proposal adjusts their center coordinates and also, if needed, the radius of their trajectory. The performance of our proposal is evaluated through computer-based simulations. In addition, we conduct several field experiments in order to verify the effectiveness of UAV-aided networks.

Controlled Environment Agriculture for Effective Plant Production Systems in a Semiarid Greenhouse

of water, respectively. The air relative humidity for fog cooling was slightly higher than that for pad-and-fan cooling, at approximately 35%. An English version of Visual VETH (ventilation-evapotranspiration-temperature-humidity) software was also developed. A cooling strategy devised for semiarid greenhouses found that the air relative humidity inside a greenhouse decreased with an increase in ventilation rate as expected from simulation based on steady-state energy balance equations, while the water use for fog cooling increased. A simple and unique control algorithm for fogging and ventilation inlet openings demonstrated the possibility of maintaining relative humidity and air temperature simultaneously within a desirable range while reducing the water use for fog cooling. The tomato plant canopy transpiration rate and the water balance relative to the natural ventilation rate in a fog-cooled greenhouse were also investigated. The transpiration rate increased linearly with an increase in vapor pressure deficit (VPD) of the air. At a lower ventilation rate made possible by reducing the ventilation inlet openings, total water use in the greenhouse decreased by 13% and relative humidity increased as was expected from the steady-state energy balance simulation. The decrease in canopy transpiration resulted from the decrease in VPD, and was at a magnitude greater than that of the fog evaporation rate under similar experimental conditions with relatively high humidity in the range of 70-94%. By optimizing the natural ventilation rate, the greenhouse could be effectively cooled with less water use. Arizona can be considered a model analogous to many other semiarid climate conditions. Due to the long history of greenhouse technology development, the application of greenhouse crop production to an area with excessive radiation and dry air remains a relatively new effort. We believe that our efforts will contribute not only to the American Southwest but also to enhancing the application of greenhouse technology for crop production in these climate regions worldwide, including Mexico, China, the Middle East and Africa.

A Simplified Motion Isolated Load Control for Multi-Channel Syncro-Loading System

For the multi-channel syncro-loading (MCSL) test, the specimen may be driven by a particular motion of another position channel, representing an in-service duty cycle. The loading accuracy is largely affected by the specimen motion. To reduce the cross coupling from the motion, the cross coupling characteristics between multi-channels is analyzed, and a simplified motion isolation load control (MILC) algorithm is provided, in which the velocity and acceleration of the specimen, measured by the accelerometer, are added into the forward path of the loading control channel in order to drive the actuator to match the motion of the specimen. The test results indicate that the MILC algorithm can significantly improve the loading accuracy compared with the conventional loading control method.

衝撃的荷重負荷に対する冗長多関節ロボットの安定姿勢と位置決め復帰動作の実現

This paper proposes a simple control algorithm to realize stable position of a multi-jointed robotic arm with absorbing impact force exerted on the tip of the redundant robotic arm. Also, recovery motion to a previous orientation maintained prior to the impact is easily realized by a present control algorithm. This control method is based on virtual desired trajectory technique mentioned on our previous research, which is formed by an integral controller that accumulates state-steady error of the tip positions of the robot. The impact force absorption can be realized by temporal stop of the integral controller and instant increase of differential gains utilized at PD controller for the robot motion, resulting in a hold of the virtual desired trajectory of joint angles and in the inhibition of back action against collisional obstacles. This method can be applied to conventional motor-driven mechanism, as a result, we can show that this proposed control algorithm can be applied without any change for the motor-driven structure, as well as an antagonistic wire-driven mechanism. Finally, we verify effectiveness and availability of the impact force absorption method by numerical analysis.

A Simple Copper Loss Minimization Control Algorithm for a Grid Connected Squirrel-Cage Induction Generator Through Indirect Flux Optimization

This article proposes a simple copper loss minimization control algorithm to minimize copper losses of a squirrel-cage induction generator based wind energy conversion system to improve efficiency at low wind speeds. The proposed scheme does not necessitate rotor position information and an encoder. The proposed algorithm is used to find the optimum slip and stator voltage such that efficiency of the squirrel-cage induction generator is increased by minimizing the copper loss. This is particularly useful in extracting the power at low speeds, where losses form a higher percentage of input power when flux is maintained at the rated value. Especially at low wind speeds, the total copper loss can be minimized by decreasing the flux. The proposed algorithm is a simple scalar control that has the potential to reduce losses, and this has been attempted considering voltage and flux saturation limits. To validate the performance of the scheme, a comparison is made with an indirect field-oriented control scheme, in which rotor flux is maintained constant. Simulations are carried out on a typical 2-MW squirrel-cage induction generator in a MATLAB/Simulink environment (The MathWorks, Natick, Massachusetts, USA). Experimentations on 2.3-kW laboratory test setup further validate the efficacy of the proposed scheme.

유압실린더의 위치제어를 위한 시스템 인식을 통한 FRF 기반의 제어기 설계 방법

In this study, we have focused on the design of a controller and an operating program for the operation of the hydraulic actuators used in a shaker. To control the motion of the shaker accurately, the position of each hydraulic cylinder should be controlled precisely even under an uncertain environment. For this purpose, we have suggested a control algorithm using an FRF (frequency response function) based control which senses the behavior of the actuator in advance, calculates a transfer function through the system identification method, and provides the final control input. The experimental results on the performance of this system were compared with that of a simple PID control algorithm.

Sensorimotor Model of Obstacle Avoidance in Echolocating Bats.

Bat echolocation is an ability consisting of many subtasks such as navigation, prey detection and object recognition. Understanding the echolocation capabilities of bats comes down to isolating the minimal set of acoustic cues needed to complete each task. For some tasks, the minimal cues have already been identified. However, while a number of possible cues have been suggested, little is known about the minimal cues supporting obstacle avoidance in echolocating bats. In this paper, we propose that the Interaural Intensity Difference (IID) and travel time of the first millisecond of the echo train are sufficient cues for obstacle avoidance. We describe a simple control algorithm based on the use of these cues in combination with alternating ear positions modeled after the constant frequency bat Rhinolophus rouxii. Using spatial simulations (2D and 3D), we show that simple phonotaxis can steer a bat clear from obstacles without performing a reconstruction of the 3D layout of the scene. As such, this paper presents the first computationally explicit explanation for obstacle avoidance validated in complex simulated environments. Based on additional simulations modelling the FM bat Phyllostomus discolor, we conjecture that the proposed cues can be exploited by constant frequency (CF) bats and frequency modulated (FM) bats alike. We hypothesize that using a low level yet robust cue for obstacle avoidance allows bats to comply with the hard real-time constraints of this basic behaviour.

Predictive control of an activated sludge process: An application to the Viikinmäki wastewater treatment plant

In this work, we discuss the application of multivariable predictive control for the activated sludge process in a full-scale municipal wastewater treatment plant. Emphasis is given to the selection of a control configuration that contributes to minimising the economic costs while improving the removal efficiency of the nitrogen compounds. For this task, a simple dynamic matrix control algorithm is favoured for controlling the nitrogen concentrations at the end of the biological process. The behaviour of the activated sludge process is reproduced in a commercial simulator that acts as a real-time testing platform and that is also used for identifying the multivariable input–output models for the predictive controller. For demonstrating the effectiveness of the proposed approach, different control configurations are considered and compared against the aeration control strategies currently used at the plant. Based on the simulation results, this work shows the potentiality of the dynamic matrix control which is able to decrease the energy consumption costs and, at the same time, reduce the ammonia peaks and nitrate concentration in the effluent.

Efficient distributed algorithm of dynamic task assignment for swarm robotics

Dynamic task allocation in a robotic swarm is a necessary process for proper management of the swarm. It allows the distribution of the identified tasks to be performed, among the swarm of robots, in such a way that a pre-defined proportion of execution of those tasks is achieved. In this context, there is no central figure to take care of the task allocation. So any algorithm proposal must be distributed, allowing every and each robot in the swarm to identify the task it must perform. This paper proposes a simple yet efficient distributed control algorithm to implement dynamic task allocation in a robotic swarm. In this algorithm, each robot that integrates the swarm runs the algorithm whenever it senses a change in the environment. The algorithm was implemented and extensively tested in different size swarms of robots. The corresponding performance and effectiveness are promising, as shown in the presented results and comparison. The swarm robot used is Elisa-III.

A PLL-Less Scheme for Single-Phase Grid Interfaced Load Compensating Solar PV Generation System

This paper proposes a single-phase double-stage scheme for grid interfaced load compensating solar photovoltaic (PV) generating system. The scheme serves twofold objectives of alleviating power quality issues such as power factor correction and harmonics mitigation, while simultaneously extracting the maximum power generated by the PV unit. A simple notch-filtering control algorithm is designed to facilitate extraction of the real component of load current, exempting the services of a phase locked loop (PLL). The absence of a PLL reduces the system dependence on the proportional-integral (PI) controller tuning, which in turn improves the dynamic response and makes the system quite robust. The proposed solar PV generation system retains its ability of mitigating harmonics on cloudy days and also provides opportunity for night time utilization of available resources. The system has been analyzed under both linear and nonlinear varying loads using and an experimental verification of the results is carried out on a developed prototype of the system.