Characteristic analysis of electro-slag remelting system model and multi-loop PID control

The grain structure of Electroslag Remelting (ESR) ingot has the significant effect on the mechanical properties of die or tool steel. A numerical model has been developed to simulate the grain structure of ESR ingot using the cellular automata method, which builds the continuous nucleation model based on the Gaussian distribution and growth model. A calculation domain was divided into macro-grid finite element to compute temperature field; then grid was divided into more detailed and uniform cells for the calculation of the nucleation and growth using cellular automaton method in solidification processes. The results show there is a vertical columnar grain zone and an inverted V-shaped columnar grain zone appeared in the main section of the ESR ingot. Effect of some parameters such as the electrode melting rate, slag pool temperature, average nucleation undercooling and maximum grain density on structure are examined.

There are many design methods for the multiloop control system, but a method to exactly evaluate the stability margin for multiloop control systems has not been established yet. It is very important for the designers to exactly know the stability margin of the flight control system, because it directly comes to bear on flight safety. Previous research has proposed the “-1/ξ locus” analysis method for the exact evaluation of the stability margin of multiloop flight control systems. -1/ξ is an open loop transfer function of multiloop control systems that is considered as an extension of that for single-loop control systems. In this paper, the relation between the response of the closed loop and the stability margin is considered by using the -1/ξ locus. Lateral-directional flight control system was taken for instance, important points to pay attention to use the -1/ξ locus method for designing the flight control system are presented.

Multiloop fractional order PID controller is tuned using Bat algorithm for two interacting conical tank process. Two interacting conical tank process is modelled using mass balance equations. Two Interacting Conical Tank process is a complex system involving tedious interaction. Straight forward multiloop PID controller design involves various steps to design the controller. Due to easy implementation and quick convergence, Bat algorithm is used in recent past for solving continuous non-linear optimization problems to achieve global optimal solution. Bat algorithm, a swarm intelligence technique will be attempted to tune the multiloop fractional order PID controller for two interacting conical tank process. The multi objective optimized multiloop fractional PID controller is tested for tracking, disturbance rejection for minimum Integral time absolute error.

We are thrilled to present twenty-five (25) contributed research papers selected from the proceedings of the International Symposium on Liquid Metal Processing and Casting (LMPC) 2024, held in Leoben, Austria, from September 22-25, 2024. This year’s event marks a significant milestone in the ongoing success of the LMPC symposium series, which has long been a cornerstone in advancing the field of liquid metal processing. The LMPC symposium continues to serve as a premier platform for fostering dynamic collaboration between industrial and academic leaders, providing a unique opportunity to explore cutting-edge developments in the melting, refining, and casting of special metals and alloys. The papers compiled in this volume reflect the breadth and depth of research in this vital field, covering critical topics such as electro-slag remelting (ESR), vacuum arc remelting (VAR), process modeling, innovative casting techniques, segregation phenomena, and the treatment and refining of liquid metals. This collection includes papers presented in oral sessions, and the contributions are organized into five key thematic areas: Electro-Slag Remelting, Vacuum Remelting, Plasma Applications, Castings and AOD, and “solidification and properties”. List of Review Committee Members for the LMPC2024 Conference: is available in this PDF.

The problem of restricted-structure benchmarking for multi-input, multi-output (MIMO) systems controlled by multi-loop PID controllers is formulated in state space. The particular criterion shown in this paper is that for a linear quadratic generalised predictive controller, which combines the properties of linear quadratic Gaussian with those of generalized predictive control. (5 pages)

This work is devoted to the technique of solving the problem of structural-parametric synthesis of typical controllers in a multiloop cascade automatic control system, which is developed on the basis of the alternance method of parametric optimization that provides the maximum degree of invariance of local control loops relative to external perturbations with given limitations on the peak of amplitude-frequency characteristics of closed loops of the synthesized automatic control system. The task of optimizing the subsystem for controlling the fuel oil temperature in a multiloop control system of primary oil refining on an atmospheric and vacuum crude distillation unit is considered as an example, which is of independent interest.

The superalloys are characterised by a strong tendency to form segregation defects during solidification and consequently have been the subject of much attention in the development of suitable melting and casting techniques. Processes such as vacuum arc remelting and electroslag remelting are now mature technologies and have well developed strategies for minimising segregation defects in the ingots produced. However, as the process control systems have gradually become more complex and automated, the need for control logic and a good understanding of it has become pronounced. Here, the underlying technical reasons for adopting particular process control methodologies are considered. The role of process parameters in controlling slag temperature and flow patterns in the electroslag remelting process and the metal pool thermal regime in the vacuum arc remelting process is reviewed in the context of ingot solidification, with particular attention being paid to electrode position, dimensions and the need for parameter stability. It is concluded that the equipment designs presently available for these processes are fundamentally correct, but that the control systems must be instructed carefully in order to produce the desired results.

Age-of-information (AoI) is a metric quantifying information freshness at the receiver. Since AoI combines packet generation frequency, packet loss, and delay into a single metric, it has received a lot of research attention as an interface between communication network and application. In this work, we apply AoI to the problem of wireless scheduling for multi-loop networked control systems (NCS), i.e., feedback control loops closed over a shared wireless network. We model the scheduling problem as a Markov decision process (MDP) with AoI as its observable states and derive a relation of control system error and AoI. We further derive a stationary scheduling policy to minimize control error over an infinite horizon. We show that our scheduler outperforms the state-of-the-art scheduling policies for NCS. To the best of our knowledge, this is the first work proposing an AoI-based wireless scheduling policy that minimizes the control error over an infinite horizon for multi-loop NCS.

In this paper, an approach for online relay automatic tuning of multi-loop PI controllers is described for multivariable processes. In the absence of significant inter-loop cross-coupling, only one closed-loop experiment may be necessary to tune the controllers to achieve specified closed-loop characteristics. When the inter-loop interaction is significant, multiple relay experiments can be conducted to derive a process model, based on which both the decoupler and the multi-loop controllers can be designed. Simulation examples (on two-inputs-two-outputs (TITO) processes) and areal-time experiment are provided to illustrate the practical appeal of the proposed method. The performance is compared to multi-loop control design based on the Biggest Log Modulus (BLT) method.

A three-inch diameter Micro Autonomous Underwater Vehicle(Micro AUV) control system was designed and developed, of which the hardware and software control platform based on the MOOS System and BeagleBone Black as the core microcontroller was built. Based on the structure and navigation features of the Micro AUV, a cascade PID controller was designed for the Micro AUV to sail underwater with a certain heading and depth. Finally, the validity and reliability of the control system and controller were verified by the underwater experiments in the lake.

A high-stability air temperature control system

This paper investigates the application of a multi-loop PID controller in an automated treadmill exercise machine. The approach is to design a computer-controlled treadmill control system for the regulation of heart rate (HR) during treadmill exercise. A single-input and multiple-output (SIMO) controller was implemented to fast track a given heart rate profile in treadmill exercise. Two separate single-input and single-output (SISO) PID control systems are initially implemented to modify either the treadmill speed or its angle of inclination in order to achieve a desired HR. The purpose of this paper is to apply a SIMO control system by implementing a control algorithm which includes the two PID controllers working simultaneously to track the desired HR profile. The performance of the SIMO and SISO control systems are compared through the closed loop responses recorded during experimentation. This would also help future development of safe treadmill exercise system.

The comparison of different multi-loop control structures for a basic triangular system is the focus of the present paper. The idea is originated from game theory, where information is an essential component. Hence, the game-theoretic view of controller design in multi-loop control systems allows the question, how unequally distributed or incomplete information affects the control structure and the selection of the playerspsila strategies. Additionally, if constraints on the control signals are considered, the strategy set of each player is bounded. Thus, the solution of each game provides different Pareto-optimal sets depending on different bounded strategy sets. In the present paper, an asymmetric triangular multi-loop control structure of a reverse osmosis desalination plant was chosen as basis to study and discuss the effects of different information sets, due to the control structure, to the solution of each game.

Design of a Multi-loop Self-Tuning PID Controller based on the augmented output and its application.

Three-Spool Marine Gas Turbine Multi-Objective Switching Control System Design and Optimization