Potential Of Real-time Control Research Articles

Comparison of Linear and Nonlinear Model Predictive Control in Path Following of Underactuated Unmanned Surface Vehicles

Model predictive control (MPC), an extensively developed rolling optimization control method, is widely utilized in the industrial field. While some researchers have incorporated predictive control into underactuated unmanned surface vehicles (USVs), most of these approaches rely primarily on theoretical simulation research, emphasizing simulation outcomes. A noticeable gap exists regarding whether predictive control adequately aligns with the practical application conditions of underactuated USVs, particularly in addressing real-time challenges. This paper aims to fill this void by focusing on the application of MPC in the path following of USVs. Using the hydrodynamic model of USVs, we examine the details of both linear MPC (LMPC) and nonlinear MPC (NMPC). Several different paths are designed to compare and analyze the simulation results and time consumption. To address the real-time challenges of MPC, the calculation time under different solvers, CPUs, and programming languages is detailed through simulation. The results demonstrate that NMPC exhibits superior control accuracy and real-time control potential. Finally, we introduce an enhanced A* algorithm and use it to plan a global path. NMPC is then employed to follow that path, showing its effectiveness in tracking a common path. In contrast to some literature studies using the LMPC method to control underactuated USVs, this paper presents a different viewpoint based on a large number of simulation results, suggesting that LMPC is not fit for controlling underactuated USVs.

Opto-electronic feedback control of membrane potential for real-time control of action potentials

To unlock new research possibilities by acquiring control of action potential (AP) morphologies in excitable cells, we developed an opto-electronic feedback loop-based system integrating cellular electrophysiology, real-time computing, and optogenetic approaches and applied it to monolayers of heart muscle cells. This allowed accurate restoration and preservation of cardiac AP morphologies in the presence of electrical perturbations of different origin in an unsupervised, self-regulatory manner, without any prior knowledge of the disturbance. Moreover, arbitrary AP waveforms could be enforced onto these cells. Collectively, these results set the stage for the refinement and application of opto-electronic control systems to enable in-depth investigation into the regulatory role of membrane potential in health and disease.

Phase identification despite amplitude variation in a coherent beam combination using deep learning

Coherent beam combination offers the potential for surpassing the power limit of a single fibre laser, as well as achieving agile far-field beam-shaping. However, the spatial beam profile of the combined beam is significantly dependent on the phase of each fibre. Recent results have shown that deep learning can be used to extract phase information from a far-field intensity profile, hence unlocking the potential for real-time control. However, the far-field intensity profile is also dependent on the amplitude of each fibre, and therefore phase identification may also need to occur whilst the fibre amplitudes are not equal. Here, it is shown that a neural network trained to identify phase when all fibres have equal amplitudes can also identify phase values when the amplitudes are not equal, without requiring additional training data.

Optimal sizing and learning-based energy management strategy of NCR/LTO hybrid battery system for electric taxis

This paper proposes an offline sizing method and an online energy management strategy for the electric vehicle with semi-active hybrid battery system (HBS). The semi-active HBS is composed by Nickel Cobalt Rechargeable (NCR) and lithium titanate (LTO) batteries with a bi-directional DC/DC converter. First, the vehicle dynamics and the HBS are modelled. Second, a hierarchical optimal sizing method is proposed to minimize the distance-based cost (DBC) of electric taxi in a variety of driving cycles. The lower layer optimizes the energy management strategy (EMS) with dynamic programming (DP), while the upper layer optimizes the sizes of HBS for minimum DBC. Based on the sizing results, the DBC decreases firstly and then increases with the increasing LTO size. In addition, the results of DP indicate the SOC of the LTO batteries works between 50% and 80% for optimal NCR lifespan. Third, by using the rule extracted from DP, a learning-based EMS, i.e., deep deterministic policy gradient (DDPG), is proposed with excellent real-time control potential. Finally, the simulation results show that the proposed DDPG EMS achieves the improved performance than fuzzy logic control EMS and closed result with what can be achieved through DP, yet the computation time is much less.

Quantifying the true potential of Real Time Control in urban drainage systems

ABSTRACT To evaluate the performance of Real Time Control (RTC) of urban drainage systems (UDS) a comparison is made with the pre-RTC situation, making the RTC performance dependent on the functioning of the UDS prior to implementation. To standardise things, a generalised baseline is formulated here as the operation with optimal static settings of the UDS. Two maximum theoretical potential performances are then calculated, one including and one excluding system limitations. These are combined with the generalised baseline to form Realised Potential Indicators (RPIs), objective values which indicate the proximity of the RTC strategy to its maximum potential. The proposed methodology was demonstrated on the case study of Eindhoven, the Netherlands. The results obtained show that using RPIs allows for a more objective assessment and improved understanding of the efficacy of different RTC procedures. Additionally, the RPIs can provide an indication if RTC is sufficient to achieve the desired UDS performance.

A Methodology for the Design of RTC Strategies for Combined Sewer Networks

While real-time control (RTC) is considered an established means of performance improvement for existing urban drainage networks, practical applications are frequently only documented for large case studies, and many operators are still reluctant to adopt RTC into their own systems. The purpose of the presented study is to highlight the potential of RTC also for smaller networks by the example of five representative catchments in Flanders, Belgium, and to demonstrate a novel methodology for the automated design of control strategies. This method analyses a given sewer network for the identification of suitable existing and new control locations. The gathered information is used in a second step for the design of control algorithms according to generic control concepts documented in the literature, such as e.g., “Equal Filling Degree”. The resulting RTC strategy uses sensible default parameters, and can form a starting point for further refinement through optimization or manual tuning. With a modelled total combined sewer overflow volume reduction of 20% to 50%, the created strategies showed generally good performance for the tested catchments. The method proved to be applicable for all tested networks. Its use for the real-life implementation of RTC is currently under way for 10 other Flemish cases.

Optimal and real-time control potential of a diesel-electric powertrain

Real-time control strategies and their performance related to the optimal control trajectories for a diesel-electric powertrain in transient operation are studied. The considered transients are steps from idle to target power. A non-linear four state-three input mean value engine model, incorporating the important turbocharger dynamics, is used for this study. The strategies are implemented using the SAE J1939-standard for engine control and evaluated compared to both the optimal solution and the solution when the engine is restricted to follow its stationary optimal line. It is shown that with the control parameters tuned for a specific criteria both engine control strategies in the SAE J1939-standard, speed control and load control, can achieve almost optimal results, where engine load controlled shows a better trade-off between fuel economy and duration. The controllers are then extended and it is shown that it is possible to control the powertrain in a close to optimal way using the SAE J1939-standard, both with the engine speed and load controlled. However the mode where the engine is load controlled is seen to be more robust.

Modelling real-time control options on virtual sewer systems

The study presents a benchmarking methodology to assess the performance of sewer systems and to evaluate the performance of real-time control (RTC) strategies by model simulation. The methodology is presented as a general stepwise approach. Two virtual sewer systems were modelled under four climate conditions. Catchment A represents a small system with medium RTC potential, while catchment B represents a large system with large potential according to PASST guidelines. The rain data represented Oceanic, Continental, Alpine and Mediterranean situations. Annual precipitation data was used. Tests included operation without RTC, and with two classic RTC strategies, aiming at, respectively, equal filling of storage tanks (“average filling”), and aiming at avoiding spilling just upstream of the treatment plant (“WWTP load”). The results have shown that similar RTC strategies perform differently under various climatic conditions and in sewer systems. The presented benchmarking methodology can be used to test the impacts of various climate scenarios on sewer systems that suffer from the limitations of static design.

Sewer system real-time control supported by the M180 guideline document

Recently, the Working Group ‘Real-time control’ of the German Association for Water, Wastewater and Waste (DWA, formerly: ATV-DVWK) has prepared a guideline document on planning of real-time control (RTC) systems for urban drainage catchments. The document was published in December 2005 as guideline document DWA M 180; arrangements are being made for its publication in English. The current paper summarises its main issues in a comprehensive way. The guidelines will assist consultant engineers, wastewater system operators and authorities in estimating the RTC potential for their system and in planning and developing RTC systems in a structured way.

Screening for real-time control potential of urban wastewater systems

The paper describes the application of the model SYNOPSIS to the integrated modelling of urban wastewater systems. The aim was to develop a screening procedure to establish the real-time control potential (RTC) of an urban catchment without the necessity of carrying out a detailed modelling assessment procedure. SYNOPSIS was applied to a series of ‘related’ catchments (with and without real-time control) that were similar in most respects but had differences in key parameters such as total storage volume and river dilution. It was found feasible to linearly regress control potential based on a river minimum dissolved oxygen concentration with the magnitude of these parameters. Extending the application of the procedure showed that optimisation for DO performance did not necessarily reduce river ammonia concentrations and could in fact increase them. Widening the parameter space was shown to reduce the simplicity of the procedure and the correlation coefficients in the regressions. The procedure was successfully applied to a range of real catchments and managed to identify sites with existing RTC as having high potential.

Practical Perspective on Real-Time Control

Abstract Environmental regulation is evolving and will require billions of dollars in investments to improve the operation of wastewater systems and to control the wet-weather pollution. The optimization of existing facilities before building new ones has been emphasized as a preferred strategy and, consequently, municipalities are learning that they can avoid costly and unnecessary capital improvement projects. Real-time control is a technology that serves to optimize the operation of wastewater systems. However, it is still not widely used, although it is gaining acceptance in the municipal engineering community. More and more municipalities are evaluating the potential of real-time control for their systems. Nevertheless, there are relatively few examples of actual real-time control applications or publications on this topic. Many issues still need to be addressed, ranging from the evaluation of real-time control to its implementation. Some of the criteria that favour the implementation of real-time control systems are presented, including safety, reliability, adaptability and flexibility, and such a presentation is complemented by case studies of operational real-time control systems illustrating these characteristics.

Screening for real-time control potential of urban wastewater systems

The paper describes the application of the model SYNOPSIS to the integrated modelling of urban wastewater systems. The aim was to develop a screening procedure to establish the real-time control potential (RTC) of an urban catchment without the necessity of carrying out a detailed modelling assessment procedure. SYNOPSIS was applied to a series of ‘related’ catchments (with and without real-time control) that were similar in most respects but had differences in key parameters such as total storage volume and river dilution. It was found feasible to linearly regress control potential based on a river minimum dissolved oxygen concentration with the magnitude of these parameters. Extending the application of the procedure showed that optimisation for DO performance did not necessarily reduce river ammonia concentrations and could in fact increase them. Widening the parameter space was shown to reduce the simplicity of the procedure and the correlation coefficients in the regressions. The procedure was successfully applied to a range of real catchments and managed to identify sites with existing RTC as having high potential.

A methodology for assessing the operational potential of the urban wastewater system using integrated modelling

Application of real-time control (RTC) is one possible measure to increase the performance of the urban wastewater system. However, the potential and the benefits of control depend strongly on the characteristics of the individual site under question. Conventionally, RTC potential is evaluated by performing a detailed feasibility study, which in some cases may conclude that for the given site real-time control does not have any significant potential. This can result in spending considerable precious resources for a detailed feasibility study only to identify the non-feasibility of RTC in the system. It would therefore be desirable to have a methodology that allows simple, and cost-effective, screening of sites for which the analysis of real-time control may be beneficial. Earlier research has led to the provision of an easy-to-apply scoring system allowing a quick assessment of the RTC potential of controlling flow in sewer systems. However, as this procedure does not take into account water quality aspects, nor the treatment plant or the receiving water body, it cannot be used for assessing the potential of RTC of the complete system. This paper describes the work of an on-going project aimed at establishing an enhanced procedure for assessing the real-time control potential for the entire urban wastewater system. This entails simulating many (partly hypothetical) case studies (varying several key parameters of the wastewater system) using the simulation tool SYNOPSIS. For each of these sites, several real-time control algorithms are developed and optimised, following a general procedure, which allows for local, global and integrated scenarios to be considered. Analysis of the results reveals those system parameters which are of particular significance to the RTC potential of urban wastewater systems. Furthermore, it is recognised that there is considerable uncertainty associated with modelling of such a large and diverse system and a framework is developed for incorporating this in the RTC potential screening tool. Finally, further work is currently underway in broadening the number of case study simulations and developing more complex approaches to quantifying and propagating uncertainty in the model.

Criteria for assessment of the operational potential of the urban wastewater system

Application of real-time control (RTC) is one possible measure to increase the performance of the urban wastewater system. However, the potential and the benefits of control depend strongly on the characteristics of the individual site under question. Conventionally, to evaluate this potential, a detailed feasibility study had to be carried out. In some cases, such a study may well conclude that, for the given site, real-time control does not have any significant potential, thus resulting in unnecessarily having spent precious resources for a detailed study. It would be desirable to have a methodology that allows simple, and cost-effective, screening of sites for which the analysis of real-time control may be beneficial. Earlier research led to the provision of an easy-to-apply scoring system which allows a quick assessment of the RTC potential of controlling flow in sewer systems. However, since this procedure does not take into account water quality aspects, or the treatment plant or the receiving water body, it cannot be used for assessing the potential of RTC of the complete system, let alone for integrated RTC. This paper describes the first part of an on-going project which aims at establishing an enhanced procedure for assessing the real-time control potential for the entire urban wastewater system. After providing a definition of the term "RTC potential", a large number of (partly hypothetical) case studies (varying a number of key parameters of the wastewater system) is simulated, using the simulation tool SYNOPSIS. For each of these sites, a number of real-time control algorithms are developed and optimised, following a general procedure, which allows for local, global and integrated scenarios to be considered. Analysis of the results reveals those system parameters which are of particular significance to the RTC potential of urban wastewater systems. These are discussed and assessed in this paper. Furthermore, the results of a simulation study are provided which indicate a clear potential of integrated control even for many case studies for which local control provides hardly any benefits. Subsequent studies will complement the simulation study by comparison with a number of real case studies in various countries.

On-line arithmetic for real-time control of microsystems

The integration of microcontrollers within mechanical systems is a current trend. However, decreasing the size of the system and satisfying higher precision requirements make it necessary to reevaluate the common signal processing techniques for controller implementations, because limited controller size, computation speed, and power consumption become major topics. In this paper, we demonstrate that serial computations with the most significant digits first, that is, online arithmetic, offer an important potential for real-time control. They enable a combination of traditional functions, such as analog-to-digital converters and control data computations. This leads to very efficient controller implementations with small size, high speed, and low power consumption. After a brief description of the requirements and challenges of microsystem controller design, the use of online arithmetic for real-time control is proposed. A short introduction to online arithmetic is given and control-specific implementation guidelines are presented and finally applied to a simple test system.

The Potential of Real Time Control to reduce Combined Sewer Overflow

The potential of Real Time Control (RTC) to reduce the overflow volume from a combined sewer system has been investigated for a catchment in Copenhagen, named Strandvaenget. The results have been compared with the alternative of increasing the storage volume of the system. The RTC strategy has been derived using a mathematical optimization and a rule based method. As the only objective is to reduce the Combined Sewer Overflow (CSO), the developed rule based control algorithm can achieve almost the same results as the optimization method. From the results of time series calculations, it can be concluded that the introduction of RTC appears very promising when the mean yearly CSO volume has to be reduced. In this research, the potential of RTC is investigated for an increasing amount of storage volume and for an increasing demand for reduction of CSO volume.

A Model to Assess the Performance of Controlled Urban Drainage Systems

The LOCUS modelling package, which has been designed to assess the performance of an urban drainage system that is controlled in real time is presented. Besides the simulation of 'optimal' controlled systems, LOCUS offers the possibility to simulate local (or static) controlled systems as well (i.e. the present way of operation of most urban drainage systems). Since an identical system description is used in both cases, the difference between the results is only due to the way the system is operated and hence the effects of real time control can be quantified by comparing the results. The use of the model is illustrated by a simple example, which shows that it is worth investigating the potential of real time control before constructing extra storage in the system. For a small fictitious system with limited storage capacity at the downstream section it is shown that this potential is comparable to increasing the storage capacity by 1.5 mm at this particular section.

On the Potential of Real Time Control of Urban Drainage Systems

The conventional solution to urban drainage problems employs a system with a certain storage, transport and treatment capacity. The limited efficiency of this solution is due to the lack in flexibility in operating the system under dynamic loading. Optimal systems performance can only be achieved by means of real time control (RTC) of the system. The potential of RTC should be considered not only after the system has been constructed, but in the design phase of the system as well, as it will influence the required capacities of the system elements. A model is presented that can be used to assess this potential on the basis of simulation of time series of rain events. For a simple fictitious system it is shown that by means of RTC considerable savings can be achieved. These are expressed in terms of extra storage or discharge capacity that would have been required in an uncontrolled system to reach the same overflow volume as when RTC is applied. Besides it is demonstrated that currently monitored process data provide sufficient information to operate the system in a proper way. Inflow forecasts may be useful but they are not absolutely necessary to derive a suitable operation strategy.

The Importance of Rainfall Distribution in Urban Drainage Operation

A control simulation model, called LOCUS, is used to investigate the effects of spatially distributed rain and the possibilities to benefit from this phenomenon by means of real time control. The study is undertaken for a catchment in Copenhagen, where rainfall is measured with a network of 8 rain gauges. Simulation of a single rain event, which is assumed to be homogeneous, i.e. using one rain gauge for the whole catchment, leads to large over- and underestimates of the systems output variables. Therefore, when analyzing a single event the highest possible degree of rainfall information may be desired. Time-series simulations are performed for both an uncontrolled and a controlled system. It is shown that from a statistical point of view, rainfall distribution is NOT significant concerning the probability of occurrence of an overflow. The main contributing factor to the potential of real time control, concerning minimizing overflows, is to be found in the system itself, i.e. the distribution of available storage and discharge capacity. When other operational objectives are involved, e.g., to minimize peak flows to the treatment plant, rainfall distribution may be an important factor.