Boilers Optimal Control for Maximum Load Change Rate

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Moustafa Elshafei ◽  
Mohamed A. Habib ◽  
Iyad Al-Zaharnah ◽  
Medhat A. Nemitallah
Keyword(s):  
Genetic Algorithm ◽  
Optimal Control ◽  
Thermal Stresses ◽  
Maximum Load ◽  
Steam Pressure ◽  
Control Loop ◽  
Optimization Scheme ◽  
Loop Optimization ◽  
Change Rate ◽  
Control Loops

In many cogeneration systems, one or more boilers are used in hot standby to meet the plant demand of steam in case of failure or upset in the cogeneration unit. Such boilers need to quickly respond to sudden and large steam load changes. However, fast changes in the firing rate cause transient changes in both the drum-boiler steam pressure and drum level, in addition to the potential of developing of thermal stresses in the walls of steam risers. A genetic algorithm (GA) based optimization scheme is proposed for tuning the conventional boiler control loops to maximize the ability of the boiler to respond to large steam demand while keeping the fluctuations in pressure, drum level, and feed rate within acceptable operation limits. A nonlinear model for an actual boiler is first built, validated, and then, it is used to demonstrate the performance of the boiler with the proposed control loop optimization.

Maximum load carrying capacity of mobile manipulators: optimal control approach

Robotica ◽  
2009 ◽  
Vol 27 (1) ◽  
pp. 147-159 ◽  
Author(s):  
M. H. Korayem ◽  
A. Nikoobin ◽  
V. Azimirad
Keyword(s):  
Optimal Control ◽  
Optimal Control Problem ◽  
Control Problem ◽  
Carrying Capacity ◽  
Nonholonomic Constraints ◽  
Maximum Load ◽  
Mobile Manipulators ◽  
Load Carrying Capacity ◽  
Maximum Payload ◽  
Load Carrying

SUMMARYIn this paper, finding the maximum load carrying capacity of mobile manipulators for a given two-end-point task is formulated as an optimal control problem. The solution methods of this problem are broadly classified as indirect and direct. This work is based on the indirect solution which solves the optimization problem explicitly. In fixed-base manipulators, the maximum allowable load is limited mainly by their joint actuator capacity constraints. But when the manipulators are mounted on the mobile bases, the redundancy resolution and nonholonomic constraints are added to the problem. The concept of holonomic and nonholonomic constraints is described, and the extended Jacobian matrix and additional kinematic constraints are used to solve the extra DOFs of the system. Using the Pontryagin's minimum principle, optimality conditions for carrying the maximum payload in point-to-point motion are obtained which leads to the bang-bang control. There are some difficulties in satisfying the obtained optimality conditions, so an approach is presented to improve the formulation which leads to the two-point boundary value problem (TPBVP) solvable with available commands in different softwares. Then, an algorithm is developed to find the maximum payload and corresponding optimal path on the basis of the solution of TPBVP. One advantage of the proposed method is obtaining the maximum payload trajectory for every considered objective function. It means that other objectives can be achieved in addition to maximize the payload. For the sake of comparison with previous results in the literature, simulation tests are performed for a two-link wheeled mobile manipulator. The reasonable agreement is observed between the results, and the superiority of the method is illustrated. Then, simulations are performed for a PUMA arm mounted on a linear tracked base and the results are discussed. Finally, the effect of final time on the maximum payload is investigated, and it is shown that the approach presented is also able to solve the time-optimal control problem successfully.

Heat Flux Distribution Over a Solar Central Receiver Using an Aiming Strategy Based on a Conventional Closed Control Loop

2017 ◽  
Author(s):  
Jesús García ◽  
Yen Chean Soo Too ◽  
Ricardo Vasquez Padilla ◽  
Rodrigo Barraza Vicencio ◽  
Andrew Beath ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flux Distribution ◽  
Thermal Stresses ◽  
Control Strategies ◽  
Multiple Input Multiple Output ◽  
Control Loop ◽  
Heat Flux Distribution ◽  
Input Multiple Output ◽  
Solar Receiver ◽  
Solar Field

Solar thermal towers are a maturing technology that have the potential to supply a significant part of energy requirements of the future. One of the issues that needs careful attention is the heat flux distribution over the central receiver’s surface. It is imperative to maintain receiver’s thermal stresses below the material limits. Therefore, an adequate aiming strategy for each mirror is crucial. Due to the large number of mirrors present in a solar field, most aiming strategies work using a data base that establishes an aiming point for each mirror depending on the relative position of the sun and heat flux models. This paper proposes a multiple-input multiple-output (MIMO) closed control loop based on a methodology that allows using conventional control strategies such as those based on Proportional Integral Derivative (PID) controllers. Results indicate that even this basic control loop can successfully distribute heat flux on the solar receiver.

Air Suspension Optimal Control Based on the Genetic Algorithm

2011 ◽  
Vol 467-469 ◽  
pp. 1066-1071
Author(s):  
Zhong Xin Li ◽  
Ji Wei Guo ◽  
Ming Hong Gao ◽  
Hong Jiang
Keyword(s):  
Genetic Algorithm ◽  
Optimal Control ◽  
Dynamic Model ◽  
Control Method ◽  
Control Model ◽  
Weight Matrix ◽  
Object A ◽  
Full Vehicle ◽  
Air Suspension ◽  
Optimal Control Method

Taking the full-vehicle eight-freedom dynamic model of a type of bus as the simulation object , a new optimal control method is introduced. This method is based on the genetic algorithm, and the full-vehicle optimal control model is built in the MatLab. The weight matrix of the optimal control is optimized through the genetic algorithm; then the outcome is compared with the artificially-set optimal control simulation, which shows that the genetic-algorithm based optimal control presents better performance, thereby creating a smoother ride and improving the steering stability of the vehicle.

Maximum load determination of nonholonomic mobile manipulator using hierarchical optimal control

Robotica ◽  
2011 ◽  
Vol 30 (1) ◽  
pp. 53-65 ◽  
Author(s):  
M. H. Korayem ◽  
V. Azimirad ◽  
H. Vatanjou ◽  
A. H. Korayem
Keyword(s):  
Optimal Control ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Maximum Load ◽  
Mobile Manipulator ◽  
Interaction Terms ◽  
Different Types ◽  
Interaction Variables ◽  
Maximum Allowable Dynamic Load

SUMMARYThis paper presents a new method using hierarchical optimal control for path planning and calculating maximum allowable dynamic load (MADL) of wheeled mobile manipulator (WMM). This method is useful for high degrees of freedom WMMs. First, the overall system is decoupled to a set of subsystems, and then, hierarchical optimal control is applied on them. The presented algorithm is a two-level hierarchical algorithm. In the first level, interaction terms between subsystems are fixed, and in the second level, the optimization problem for subsystems is solved. The results of second level are used for calculating new estimations of interaction variables in the first level. For calculating MADL, the load on the end effector is increased until actuators get into saturation. Given a large-scale robot, we show how the presenting in distributed hierarchy in optimal control helps to find MADL fast. Also, it enables us to treat with complicated cost functions that are generated by obstacle avoidance terms. The effectiveness of this approach on simulation case studies for different types of WMMs as well as an experiment for a mobile manipulator called Scout is shown.

scholarly journals Detection and diagnosis of Oscillation in Shell and Tube Heat Exchanger Process

2019 ◽  
Vol 8 (6) ◽  
pp. 2237-2241
Keyword(s):  
Heat Exchanger ◽  
Rejection Rate ◽  
Process Variable ◽  
Control Loop ◽  
Control Loops ◽  
Tube Heat Exchanger ◽  
Analysis Technique ◽  
Product Increase ◽  
Shell And Tube ◽  
Detection And Diagnosis

Oscillations found in process control loops are the visible indications of process deterioration. The presence of oscillation in an industrial control loop may reduce quality of the product; increase the rejection rate and energy consumption which may result in reduced profitability. Many techniques stated in the literature for oscillation diagnosis has their own benefits and limitations. Performance assessment of a single control loop is a valued procedure to spot suddenly rising faults and slowly emerging degradation. In this paper, the oscillations present in the process variable of a Shell and Tube Heat eXchanger (STHX) process are diagnosed using the Higher Order Spectral Analysis (HOSA) in MATLAB. From HOSA, bispectrum, modified bispectrum and bicoherence analysis technique is applied to the laboratory STHX process to spot the probable root cause for oscillations

A Novel SOFC Thermal Management Strategy of SOFC-GT Hybrid System With Anode and Cathode Control Loops

2020 ◽  
Author(s):  
Jinwei Chen ◽  
Yuanfu Li ◽  
Huisheng Zhang ◽  
Zhenhua Lu
Keyword(s):  
Thermal Management ◽  
Temperature Control ◽  
Management System ◽  
Management Strategy ◽  
Inlet Temperature ◽  
Control Performance ◽  
Control Loop ◽  
Control Loops ◽  
Thermal Management System ◽  
Cathode Temperature

Abstract The SOFC performance and lifetime highly depend on the operation condition, especially the SOFC operation temperature. The temperature fluctuation causes thermal stress in electrodes and electrolyte ceramics. On the other hand, it also needs to maintain a sufficiently high temperature to enable the efficient transport of oxygen ions across the electrolyte. Therefore, it is necessary to design an effective SOFC temperature management system to guarantee safe and efficient operation. In this paper, a two-side temperature control method is proposed to avoid the temperature difference between anode and cathode. Therefore, the SOFC thermal management system includes two control loops. The anode inlet temperature and cathode inlet temperature are controlled by blowers adjusting the recirculated flow rate. In addition, the control performance of the proposed SOFC thermal management system is compared with one-side temperature control systems. The results show that both anode control loop and cathode control loop are essential to get a better control performance. The SOFC would operate with less efficiency with only anode temperature control. On the other hand, the safety problem would occur with only cathode temperature control. The temperature gradient would be more than the upper limit at a part load condition. Therefore, the SOFC thermal management strategy with anode and cathode temperature control loops is feasible for the SOFC-GT system.

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