On-off Control Strategy Research Articles

Economic viability of under floor heating system: a case study in Beirut climate

This paper explores the economic feasibility of the underfloor heating system for the climatic conditions of Beirut. A case study of a typical residential room (150 m2 ) is selected to compare its heating energy requirement when using either the conventional convective heating system or the underfloor heating system at similar comfort and indoor air quality conditions. Two mathematical models are developed, a steady space thermal model to establish the energy consumption at the peak load and a transient simulation model to find the energy consumption during the winter heating season. In addition, the economic feasibility of the underfloor heating system is assesd when integrated with solar energy. Based on the steady space model, the calculated peak heating load is reduced by 20% when the test space is heated by the underfloor heating system and a thermal comfort level of PPD 18.3% is achieved for a floor temperature of 27.4 ºC. The simulation results of the transient space model indicates that the seasonal heating energy consumption is reduced by 18% and that the yearly energy savings is $104 for an on-off control strategy that maintains a PMV comfort level greater than -0.5. The pay back period of the underfloor heating system is 10 years for an initial incremental cost of $850. When integrated with 10 solar collector units, the yearly energy savings of the integrated system is increased to $350 and the pay back period is 14 years.

An ON-OFF Closed-Loop Control of Photoelectric Actuator Based on PLZT Ceramic

PLZT (lanthanum-doped lead zirconate titanate) ceramic with outstanding photostrictive effect has been widely used in the micro precision drive field. In this article, a new closed-loop control method with ON-OFF control strategy is proposed for the photoelectric actuator based on PLZT ceramic. The closed-loop control model under driving voltage control strategy is established, and the parameters are identified by a series of experiments. Then, the control equations of driving voltage and output displacement of the photoelectric actuator are derived on the basis of the closed-loop control model during the light on and light off phases. After that, the numerical simulation analysis is carried out when the driving voltage and output displacement are taken as control objects respectively. According to the analysis results, the output displacement of the photoelectric actuator can be successfully controlled at a specific target value, and the proposed control method has excellent control effect, the feasibility and effectiveness of the control method are verified. Relevant conclusions can lay a foundation and provide theoretical guidance for the practical application of the photoelectric actuator in the field of active control.

Modulation Methods for Balancing the Capacitor Voltages of N-Level Diode-Clamped Converters

Diode-clamped converters (DCCs) suffer from the inherent capacitor voltage imbalance problem. Most software-based voltage-balancing methods fall into the space-vector-modulation (SVM) category and the carrier-based pulse-width-modulation (CB-PWM) category. Despite their effectiveness for the three-level DCCs, it is not easy to extend them to a general <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level topology. In this paper, a new modulation method of a category called good-switching (GS) PWM is proposed for balancing the capacitor voltages. The proposed method requires no parameter-tuning effort and is extremely simple to design even for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level topology regardless of the number of phases. It is also potentially applicable to other multilevel converters. The principle, the implementation, and the stability analysis of GS-PWM are elaborated for a generic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -level DCC. A modified GS-PWM scheme and an on-off control scheme are proposed to reduce the switching transitions for further realizing the advantages of the GS-PWM. Particularly, the on-off control can be extended to many other voltage-balancing methods. Simulation and experiments with a five-level DCC validate the proposed methods.

A GM-Based Energy Management Strategy of Hybrid Power System for Hydrogen Fuel Cell Buses

Hydrogen energy is a clean, carbon-free, flexible, efficient, and widely used secondary energy source, which is an ideal alternative to promote the clean and efficient use of traditional fossil fuels. Hydrogen fuel cell bus has the advantages of a high-energy conversion rate, absolute pollution-free, sufficient raw materials, and convenient filling. The hybrid power system, composed of fuel cell and auxiliary energy source, is one of the key technologies to promote the development of hydrogen fuel cell vehicle. This study aims to propose an energy management strategy by analyzing the output characteristics and power allocation of fuel cell and power battery in the hybrid power mode with fuel cell as the main and battery as the auxiliary. A GM (1, N) power prediction strategy was proposed and compared with other strategies as an on-off control strategy and logical threshold value strategy in this study. The variation curves of the battery SOC and fuel cell output power under two working conditions of CCBC and real vehicle conditions were analyzed by using these three strategies, when the initial SOC of power battery is 30%, 70%, and 90%, respectively. Results showed that the power prediction strategy based on GM (1, N) has a better performance in output efficiency and fuel economy when compared to the other two strategies by analyzing the aspects of the battery in the SOC variation and equivalent hydrogen consumption and the fuel cell in the output power variation and hydrogen consumption. This research can be helpful to provide the suggested solution for energy management of the hybrid power system for hydrogen fuel cell buses.

A Physics-Based Modelling and Control of Greenhouse System Air Temperature Aided by IoT Technology

The need to reduce energy consumption in greenhouse production has grown. Thermal heating demand alone accounts for 80% of conventional greenhouse energy consumption; this significantly reduces production profit. Since microclimate affects crop metabolic processes and output, it is essential to monitor and control it to achieve both quantity and quality production with minimum energy consumption for maximum profit. The Internet of Things (IoT) is an evolving technology for monitoring and controlling environments that have recently been adopted to boost greenhouse efficiency in many applications by integrating hardware and software solutions; therefore, its adoption is thus critical in enabling greenhouse energy consumption minimisation. The first objective of this study is to improve and validate a greenhouse dynamic air temperature model required to simulate or predict indoor temperature. To achieve the first objective, therefore, an existing model was enhanced and a closed loop test experimental data from the IoT cloud-based control system platform deployed in the prototype greenhouse built in Cranfield University was used to validate the model using an optimisation-based model fitting approach. The second goal is to control the greenhouse air temperature in simulation using relatively simple PI and on-off control strategies to maintain the grower’s desired setpoint irrespective of the inevitable disturbances and to verify the potential of the controllers in minimising the total energy input to the greenhouse. For the second objective, the simulation results showed that the two controllers maintained the desired setpoint; however, the on-off strategy retained a sustainable oscillation, and the tuned PI effectively maintained the desired temperature, although the average energy used by the controllers is the same.

Rule-Based On-Off Traffic Control Strategy for CAVs on Motorway Networks: Assessing Cooperation Level and Driving Homogeneity

Connected and automated vehicles (CAVs) attract much attention due to their unique behavioral characteristics and the promise to transform road transport systems as we know them today. However, the behavior of such vehicles on the road is not homogeneous since each manufacturer offers different implementations. Cooperation is essential to homogenize the traffic flow of CAVs and prevent delays on congested networks with high demand. This work proposes a rule-based decentralized on-off cooperation strategy at merging locations on freeway networks using CAVs as mobile actuators. The proposed strategy handles bilateral conflicts at on-ramps between vehicles with conflicting trajectories, taking actions at the vehicle level in a lateral or longitudinal direction, to minimize the disturbance for the following vehicles. Furthermore, heterogeneity among such vehicles is assessed through different parameter distributions among CAVs to demonstrate the importance of ensuring homogeneous dynamics in the vehicle operation design. Microscopic simulation is used to demonstrate the robustness of the proposed strategy and the value of homogeneous dynamics. The results show that the average network delay time decreased by up to 46%. Homogeneous driving behavior amplifies the benefit of the cooperative strategy significantly.

Investigation of the Series Hybrid Electric Powertrain Architecture with Wankel Engine as a Range Extender

In this study, a conventional vehicle is converted into a series hybrid electric vehicle. Electric motor power, battery pack capacity, range extender operating condition is determined; a computational model of the vehicle is built and simulations are conducted using Worldwide Harmonized Light Vehicles Test Procedure (WLTP). Power rating of the electric motor is calculated as 120 kW for the same acceleration performance. Wankel engine data available in the Automotive Laboratory of Istanbul Technical University are used. Energy capacity of battery pack is determined according to the daily driving distance of the WLTP. Engine on-off control strategy is used to control range extender operation. Wankel engine is operated at a speed of 4000 rpm and load of 5.15 bar, hence it is tuned to deliver an output power of 22.3 kW. Simulation results show that the performance of Wankel engine is validated as range extender by using engine on-off control strategy. State of charge of battery pack is set as minimum (30%) at the beginning of simulation and the state of charge of the battery pack charged by the range extender is assumed to be approximately 50% at the end of the cycle. For comparison, performance of Wankel engine is compared to the range extender of a mass-produced series hybrid electric vehicle, which has a battery pack capacity of 18.8 kWh. In conclusion, it is shown that a more compact range extender unit with a battery pack of 35 kWh is advantageous from the perspective of the packaging of the battery pack.

Feedback-controlled laser ablation for cancer treatment: comparison of On-Off and PID control strategies.

Laser ablation is a rising technique used to induce a localized temperature increment for tumor ablation. The outcomes of the therapy depend on the tissue thermal history. Monitoring devices help to assess the tissue thermal response, and their combination with a control strategy can be used to promptly address unexpected temperature changes and thus reduce unwanted thermal effects. In this application, numerical simulations can drive the selection of the laser control settings (i.e., laser power and gain parameters) and allow evaluating the thermal effects of the control strategies. In this study, the influence of different control strategies (On-Off and PID-based controls) is quantified considering the treatment time and the thermal effect on the tissue. Finite element model-based simulations were implemented to model the laser-tissue interaction, the heat-transfer, and the consequent thermal damage in liver tissue with tumor. The laser power was modulated based on the temperature feedback provided within the tumor safety margin. Results show that the chosen control strategy does not have a major influence on the extent of thermal damage but on the treatment duration; the percentage of necrosis within the tumor domain is 100% with both strategies, while the treatment duration is 630 s and 786 s for On-Off and PID, respectively. The choice of the control strategy is a trade-off between treatment duration and unwanted temperature overshoot during closed-loop laser ablation. Clinical Relevance-This work establishes that different temperature-based control of the laser ablation procedure does not have a major influence on the extent of thermal damage but on the duration of treatment.

Quantitative Evaluation of the Impacts of the Time Headway of Adaptive Cruise Control Systems on Congested Urban Freeways Using Different Car Following Models and Early Control Results

The impact of driving automation and adaptive cruise control (ACC) on traffic performance has been increasingly studied in recent years. This paper focuses on two widely used ACC car following models and investigates the impact of the time headway parameter on traffic operation and performance on one of the busiest freeway corridors in Ontario, Canada. Using Aimsun microsimulation, we compare two commonly used ACC car following models; the intelligent driver model (IDM) and Shladover’s model which has been recently adopted in Aimsun Next 20. Several experiments have been conducted to evaluate the freeway performance for different desired headway settings and market penetration rates of ACC-equipped vehicles. Simulations results confirm the reported IDM drawbacks of having a slow response leading to headway errors which are less pronounced with Shladover’s model thereby leading to more accurate quantification by the latter. This study further presents a simple on-off ACC-based traffic control strategy which aims to adapt in real time the driving behavior of ACC-equipped vehicles to the prevailing traffic conditions so that freeway performance is improved. The simulation results demonstrate that, even for low penetration rates of ACC vehicles, the proposed control concept improves the average network throughput, delay, and speed compared to the case of only manually driven or uncontrolled ACC vehicles.

Control and experimental study of 6-DOF vibration isolation platform with magnetorheological damper

Vibration is an inevitable excitation in the operation of the mechanical system, which reduces its reliability and service life. Therefore, a heavy-duty 6-DOF semi-active vibration isolation system (VIS) with magnetorheological (MR) damper was proposed in this paper. Firstly, A MR damper with large output force of 27 kN was designed. The properties test results showed that the dynamic range (the adjustable multiple of damping force) of the damper is as high as 15, which has excellent dynamic performance. And a Bouc-Wen model which can accurately describe the mechanical behavior of the MR damper was established. Secondly, the prototype of the MR 6-DOF vibration isolation platform (VIP) with cubic structure was developed. Thirdly, a on-off semi-active control strategy was proposed for the MR 6-DOF VIP. The numerical simulation results showed that the semi-active VIS can effectively isolate vibration in the working frequency domain. Finally, the vibration experiment on shaking table was carried out. The test results showed that the designed heavy-duty MR 6-DOF semi-active VIP can control the load's attitude in real-time according to the system state. Compared with the current of 0 A, the vibration isolation effect of the on-off control is improved by 63.27% in the resonance region. The MR 6-DOF VIP can effectively reduce the vibration transmitted to the isolated system through the platform.

Design and Research of Semiactive Quasi-Zero Stiffness Vibration Isolation System for Vehicles

The vehicle-mounted equipment is easy to be disturbed by external vibration excitations during transportation, which is harmful to the measurement accuracy and performance of the equipment. Aiming at the vibration isolation of the vehicle-mounted equipment, a semiactively controlled quasi-zero stiffness (QZS) vibration isolator with positive and negative stiffness is proposed. The vertical spring is paralleled with a magnetorheological (MR) damper, and the semiactive on-off control scheme is adopted to control the vibration. The analytical expression of the isolator’s displacement transmissibility is derived via the averaging method. Then, the vibration isolation performance under different road excitations and different driving speeds is simulated and compared with the uncontrolled passive QZS vibration isolator. In addition, the mechanical structure of the semiactive QZS isolator is designed and manufactured, and the test system is built by LabVIEW software and PXI embedded system. The isolation effect of the semiactive QZS isolator is verified through test data. It is found that the proposed semiactive QZS isolator shows excellent vibration isolation performance under various road excitations, while the passive QZS isolator is effective only under harmonic excitations. The vertical acceleration of vehicle-mounted device can be decreased over 70% after isolation, and the vibration isolation effect is remarkable. The design idea and research results of the semiactive QZS isolator may provide theoretical guidance and engineering reference for vibration isolation.

DYNAMICAL ANALYSIS ON A KIND OF SEMI-ACTIVE VIBRATION ISOLATION SYSTEMS WITH DAMPING CONTROL 1)

A series of single-degree-of-freedom semi-active nonlinear vibration isolation system with cubic stiffness based on relative velocity feedback on-off control is studied. By using the averaging method, the approximate analytical solutions of the primary resonance of the system are obtained, which is controlled by the acceleration and relative velocity based acceleration drive damping control, the velocity and relative velocity based sky-hook damping control, and the displacement and relative velocity based ground-hook damping control, respectively. A further comparison between the numerical solutions and the approximate analytical solutions under different control strategies is fulfilled. And such comparison results suggest that the approximate analytical results are quite consistent with the numerical solutions, which verifies the effectiveness of the approximate analytical solutions. Moreover, the stability conditions of the steady-state solution of the system under different control strategies are analyzed by Lyapunov theory, and the influences of system parameters on the control effect are discussed. In order to compare the control performances in the three different control approaches, the amplitude-frequency response equation is conducted. The results show that the similar expressions can be found in the switching conditions in the process of the analytical analysis of the three relative velocity feedback control strategies. In the aspect of suppressing resonance response amplitude, the sky-hook damping control strategy based on velocity and relative velocity feedback has the best damping effect in low frequency band, while the acceleration drive damping control strategy based on acceleration and relative velocity feedback has the best damping effect in high frequency band. The sky-hook damping control strategy also shows good performance in reducing the amplitude response of transient response. This analytical research method can also be applied to the system with other semi-active on-off control strategies, and it provides an effective way for the control strategy research of semi-active vibration isolation system.

Power Management For A Series Hybrid Electrical Vehicle Via On-off Control Strategy

Hybrid electric vehicles (HEV) powered by internal combustion engine (ICE) and energy storage device are now being given more and more attention because of their inherent advantages over the conventional vehicles (i.e. increased fuel economy, reduced harmful emissions and better vehicle performance). Most common HEV types are series hybrid electrical vehicles (SHEV) and parallel hybrid electrical vehicles (PHEV). As the HEV improvement highly depends on the management of power flow between the different parts of the vehicle, an attempt will be made through this paper to study the on-off control strategy for a SHEV with the help of Matlab/Simulink. In the on-off control strategy, the IEC is operated at its optimal operating point which is based on minimization of fuel consumption or minimization of emissions or even a compromise on both. The overall efficiency of the SHEV under the on-off control strategy will be investigated and the effect of the initial state of charge (SOC) of the battery on the overall efficiency will be considered.

Enhancing Friction Pendulum Isolation Systems Using Passive and Semi-Active Dampers

Friction pendulum systems (FPSs) are a common solution for isolating civil engineering structures under ground movements. The result is a base-isolated structure in which the base exhibits low shear stiffness in such a way that the input energy of the earthquake is concentrated and dissipated into it, leaving the superstructure free of damage. As a consequence, large displacements of the FPS may be demanded depending on the earthquake intensity and the fundamental period of the FPS. To accommodate these displacements, large-size isolators with high friction coefficients are usually required. However, the FPS will then exhibit poor re-centering capacity and the risk of future shocks will increase due to previous residual displacements, especially for low-intensity earthquakes. An alternative solution is to include a semi-active damper to the FPS, keeping the friction coefficient low and achieving both, limited base displacement under high-intensity earthquakes and good re-centering capacity under low-intensity ones. Thus, this work presents a design methodology for base isolators formed by an FPS with a damper added. The design methodology is applied to an FPS with a passive damper and to an FPS with a semi-active damper. Two ON-OFF control strategies are studied: (i) a fairly simple phase control, and (ii), a mechanical energy-predictive based algorithm. The advantages of semi-active FPSs with low friction coefficients with respect to FPS with high friction coefficients are demonstrated. The results with the designed semi-active FPS are compared with the single FPS and the FPS with a passive damper. Finally, the use of semi-active FPS allows us to enhance the FPS performance as the isolator size can be reduced while keeping the capacity to cope with low and high-intensity earthquakes without residual displacements.

On-Off Control Strategy in a BWRO System under Variable Power and Feedwater Concentration Conditions

Although reverse osmosis (RO) is the technology of choice for solving water shortage problems, it is a process that consumes large amounts of energy. Brackish water (BW) desalination is more efficient than seawater desalination due to the lower salinity of the feedwater source. This makes coupling renewable energy sources with BWRO systems attractive. The operation of this type of systems is complex and requires the design of control strategies to obtain optimal operation. The novelty of this work was to propose a simple on-off control strategy for operating a BWRO system that can work with one and two stages and with different configurations considering six spiral wound membrane elements per pressure vessel (PV). The feedwater quality variations of a real groundwater well were used together with a computational tool to simulate the response of the different configurations with the purpose of selecting the most appropriate depending on the input power to the BWRO system. The most suitable configurations were found to be 1:0, 2:1 and 3:2 (PV first stage:PV second stage). It was additionally found that increased feedwater concentrations resulted in shorter operating ranges to maximize permeate water production for the 1:0 and 2:1 configurations, and that the 3:2 configuration was the most suitable for most of the operating range.

Mitigation of vortex-induced vibration lock-in using time-delay closed-loop control

We investigate the closed-loop control of a circular cylinder showing lock-in phenomena due to vortex-induced vibrations (VIV). The control action was implemented by a sampled-data proportional-integral-derivative (PID) controller to suppress the large amplitudes due to lock-in. The controller was first applied to a linearized system to observe its stability characteristics based on the eigenvalues of the system. Another method was also proposed, which employs a novel, time-dependent Lyapunov function that is positive definite at sampling times but not necessarily between the sampling times. A new set of sufficient conditions in terms of linear matrix inequalities is derived to obtain the sampled-data PID control gains for the VIV system. The PID controller tuned with these gains for various delays was applied to control the nonlinear responses of the circular cylinder during the lock-in. The results showed that the PID controller significantly reduced the rise in lock-in amplitude compared to only proportional control and for certain delays was able to completely mitigate the effects of lock-in. It was also observed that for delays ranging from 0.1 to 0.14 s, the nonlinear system was destabilized with increasing proportional gains as indicated by the eigenvalue analysis of the linearized system. Even under such situations, properly tuned integral and derivative gains could significantly reduce the amplitude rise otherwise observed due to lock-in of the uncontrolled system. Finally, an on-off control scheme was also proposed, which, if optimized properly, can restrict the lock-in amplitude to some prescribed limit by only using the control for some fraction of the total operational time. Thus, it can potentially save control power.

An Optimal Air-Conditioner On-Off Control Scheme under Extremely Hot Weather Conditions

Being reliant on Air Conditioning (AC) throughout the majority of the year, desert countries with extremely hot weather conditions such as Qatar are facing challenges in lowering weariness cost due to AC On-Off switching while maintaining an adequate level of comfort under a wide-range of ambient temperature variations. To address these challenges, this paper investigates an optimal On-Off control strategy to improve the AC utilization process. To overcome complexities of online optimization, a Elman Neural Networks (NN)-based estimator is proposed to estimate real values of the outdoor temperature, and make off-line optimization available. By looking up the optimum values solved from an off-line optimization scheme, the proposed control solutions can adaptively regulate the indoor temperature regardless of outdoor temperature variations. In addition, a cost function of multiple objectives, which consider both Coefficient of Performance (COP), and AC compressor weariness due to On-Off switching, is designed for the optimization target of minimum cost. Unlike conventional On-Off control methodologies, the proposed On-Off control technique can respond adaptively to match large-range (up to 20 ∘ C) ambient temperature variations while overcoming the drawbacks of long-time online optimization due to heavy computational load. Finally, the Elman NN based outdoor temperature estimator is validated with an acceptable accuracy and various validations for AC control optimization under Qatar’s real outdoor temperature conditions, which include three hot seasons, are conducted and analyzed. The results demonstrate the effectiveness and robustness of the proposed optimal On-Off control solution.

A New Hybrid Unit Operation for Gas Separation Membranes Application

An innovative membrane-based process for the separation of gaseous streams has been developed and tested at lab-scale. The new process can be conveniently carried out on the same modules currently employed for conventional gas separation membrane systems, and it relies on periodic swing of the downstream pressure, while upstream conditions are kept constant. Such new unit operation is run with no need of switching streams, and it allows to process constant flow rate and composition of both feed and retentate, while permeate is collected at assigned frequency, resulting in an overall on-average steady state process. An on-off control strategy over time of permeate collection produces alternate sorption/desorption steps in the membrane, associated to increase/decrease cycles of downstream pressure in the process, in a similar fashion to pressure swing adsorption (PSA). Indeed, consistently with the hybrid nature of the new process, the specific dynamic control of downstream pressure allows the exploitation of both resistive (permeation) and capacitive (adsorption) properties of the membrane, and the associated characteristics in terms of selectivity. By changing the duration of pressure swing period, the resistive or capacitive properties of the membrane can be conveniently tuned in order to explore different performances of the process, in terms of key component recovery and separation factor.

Implementation of Pneumatic Air Muscle for Actuating Knee Exoskeleton Using Four-Bar Linkage

The knee exoskeleton is a device that assists users with weak knees to walk. It consists of a mechanical construction put around the human knee which is equipped with an actuator for movement. One mechanism that can be used to mimic movement of the real knee is the four-bar linkage. This research explores the possibility of using pneumatic air muscles as actuators for a knee exoskeleton with four-bar linkage implementation. A pneumatic air muscle is a single-acting linear actuator that contracts when filled with pressurized air, mimicking muscle contraction. It is much lighter than electrical motors, but—according to characterization done in this research—is difficult to control due to its inconsistent torque output. Nevertheless, this research shows that simple gait movements can be simulated using a knee exoskeleton actuated by pneumatic air muscles with an on-off control scheme.

Development of a Monitoring and Control System for Timber’s Drying Process

Abstract The timber’s drying process is very important in reducing the wood losses and in improving the quality of the final products made of wood. Taking into consideration that the quality of the timber is directly related to the moisture content of the wood, the main problem refers to the control of the temperature and relative moisture in the drying chamber. Therefore, in order to fulfill these requirements, the automatic control strategies are needed, including the reducing of the energy consumption. The present paper highlights the components of the timber’s drying system, the design and the implementation of the On-Off control strategy and the monitoring interface.