Composite Control Structure Research Articles

Design and Control of a Middle Vessel Batch Distillation Process for Separating the Methyl Formate/Methanol/Water Ternary System

The middle vessel batch distillation process for separating the methyl formate/methanol/water ternary system was simulated using Aspen Plus and Aspen Plus Dynamics. The composition control structure (CCS) and temperature control structure (TCS) were studied in a dynamic simulation based on the results of a steady-state simulation. Two temperature control structures, one the traditional TCS and the other TCS with high selectors, show better control performances than CCS. The two control structures can stably control the product purities and liquid holdups in the product vessels at the end of the batch. The results show that TCS with high selectors is better than traditional TCS in terms of the liquid holdups. The performance of the TCS with high selectors is assessed, and controllability is demonstrated.

A Method for Controlling the Permanent Magnet Linear Motor with the Counterweight by Pneumatic Cylinder

In the control model of the permanent magnet linear motor (PMLM), if the pneumatic cylinder is used to balance the weight, the pressure dynamic variation of both suction chamber and discharge chamber can affect the load force of model. The dynamic model of pneumatic cylinder is analyzed, and the equation of impedimental force caused by the single acting pneumatic cylinder is given out. With the combination of PMLM model, the system’s kinetics equation is established. A modified 3-tier composite control structure based on nonlinear force observer is put forward. The nonlinear part of the system is compensated effectively. The the experiment results demonstrate the practical applicability and efficiency of the proposed method.

A Novel and Simple Hybrid Fuzzy/PI Controller for Brushless DC Motor Drives

A novel speed controller for the trapezoidal three—phase Brushless DC (BLDC) Motor Drive is proposed using a hybrid fuzzy logic/proportional plus integral (PI) control. The structure of the fuzzy logic controller is different from conventional fuzzy logic implementations such that it only uses three simple rules based on speed error being either in the positive, negative or zero regions. The controller outputs a reference current, that is enforced through the motor phases by pulsewidth modulation (PWM) control. The proposed fuzzy logic controller can be used individually in applications requiring lower computation load and tolerating small steady state offset. For high performance applications requiring offset free tracking, a PI controller is augmented with the fuzzy logic controller and a simple switching scheme is devised based on error variance to select the active controller based on operating conditions. The response of the drive system under the proposed composite control structure is compared with the conventional PI based and the sliding mode controllers to demonstrate its improved performance. Simulations studies using detailed models in MATLAB/Simulink's SimPowerSystems toolbox are carried out to show the validity of proposed control.

Research on the Composite Control Scheme for the Stabilized Loop of Inertial Stabilized Platform

A composite control scheme is proposed to solve the problems of friction toque and carrier disturbance lag in the stabilized loop of inertial stabilized platform. Based on analysis of composite control structure, the performance of single rate loop, double rate loop and composite control in the inhibition of carrier disturbance, friction torque and sensor noise are compared. In order to further verify the composite control method, an experimental setup is built. The experimental results show that: when the disturbance is 1deg-1Hz sinusoidal signal, the peak value of residual error of the single rate loop is 0.055 deg, the double rate loop is 0.031deg, and the composite control is the 0.0188deg, so the performance of isolation carrier disturbance of platform is effectively improved.

Comparison of Two Types of Control Structures for Benzene Chlorine Reactive Distillation Systems

The “neat” operation of the two-reactant reactive distillation column has better steady-state economics, while it presents a challenge for design, optimization, and control of the process. Based on the optimal economic design, the dual-composition control structure and dual-temperature control structure are designed respectively for the benzene chlorine consecutive reactive distillation process. The effectiveness and robustness are analyzed comparably for the disturbance resistance in terms of changes of production rate and feed composition. Results show that dual-temperature control with propose selection of tray temperatures and the optimal profile of the set point can provide better transient process performance than the composition control structure.

Control system design of a multivectored thrust stratospheric airship

Given their hovering ability, static lift airships, such as airships and balloons, are proposed as stratospheric platforms flying at a high altitude of 20 km. The shape of the envelope has a major influence on the lift and drag efficiency of an airship. Furthermore, the efficiency of a conventional actuator, such as an aerodynamic control surface for stratospheric platforms, is decreased by the low-atmospheric density and flight speed. Thus, a new type of effector configuration must be proposed. A new multivectored thrust airship called flat peach is proposed in this paper. The name is attributed to the shape of the airship, which resembles a flat peach that is a cross between a ball and a water droplet. Thus, this airship has a smaller drag coefficient than the spherical airship and higher lift efficiency than a conventional airship. A control allocation strategy among the multivectored thrusters is proposed, and a composite control structure is designed for the airship to realize accurate position control and to decrease energy consumption.

Economic model predictive control of nonlinear singularly perturbed systems

We focus on the development of a Lyapunov-based economic model predictive control (LEMPC) method for nonlinear singularly perturbed systems in standard form arising naturally in the modeling of two-time-scale chemical processes. A composite control structure is proposed in which, a “fast” Lyapunov-based model predictive controller (LMPC) using a quadratic cost function which penalizes the deviation of the fast states from their equilibrium slow manifold and the corresponding manipulated inputs, is used to stabilize the fast dynamics while a two-mode “slow” LEMPC design is used on the slow subsystem that addresses economic considerations as well as desired closed-loop stability properties by utilizing an economic (typically non-quadratic) cost function in its formulation and possibly dictating a time-varying process operation. Through a multirate measurement sampling scheme, fast sampling of the fast state variables is used in the fast LMPC while slow-sampling of the slow state variables is used in the slow LEMPC. Appropriate stabilizability assumptions are made and suitable constraints are imposed on the proposed control scheme to guarantee the closed-loop stability and singular perturbation theory is used to analyze the closed-loop system. The proposed control method is demonstrated through a nonlinear chemical process example.

A Stepping out Prevention Strategy For Permanent Magnet Linear Motor Based on Genetic and Fuzzy Neural Network Algorithm

For the problem of vertical-moved and discontinuous stator resulting from disturbance, this paper proposes an dual mode composite control structure for permanent magnet linear motor to prevent stepping out. The composite controller is designed containing fuzzy control, neural network control and genetic algorithm. The mechanism of the control and parameter optimization method for fuzzy neural network is given. It is shown that the proposed control strategy is effective for enhancing stability and safety of the vertical-moved, discontinuous stator winding permanent magnet linear motor and drive systems.

Fuzzy Adaptive Internal Model Control Schemes for PMSM Speed-Regulation System

In this paper, the speed regulation problem for permanent magnet synchronous motor (PMSM) system under vector control framework is studied. First, a speed regulation scheme based on standard internal model control (IMC) method is designed. For the speed loop, a standard internal model controller is first designed based on a first-order model of PMSM by analyzing the relationship between reference quadrature axis current and speed. For the two current loops, PI algorithms are employed respectively. Second, considering the disadvantages that the standard IMC method is sensitive to control input saturation and may lead to poor speed tracking and load disturbance rejection performances, a modified IMC scheme is developed based on a two-port IMC method, where a feedback control term is added to form a composite control structure. Third, considering the case of large variations of load inertia, two adaptive IMC schemes with two different adaptive laws are proposed. A method based on disturbance observer is adopted to identify the inertia of PMSM and its load. Then a linear adaptive law is developed by analyzing the relationship between the internal model and identified inertia. Considering the control input saturation in practical applications, a fuzzy adaptive law based IMC scheme is developed based on apriori experimental tests and experiences, where a fuzzy inferencer based supervisor is designed to automatically tune the parameter of speed controller according to the identified inertia. The effectiveness of the proposed methods have been verified by Matlab simulation and TMS320F2808 DSP experimental results.

Modified Internal Model Control of PMSM Speed-regulation System

AbstractIn this paper, the speed-regulation problem for permanent magnet synchronous motor (PMSM) system under vector control framework is studied. For the speed loop, a standard internal model controller is first designed based on a first-order model of PMSM by analyzing the relationship between reference quadrature axis current and speed. Considering the disadvantages that the standard IMC method is sensitive to control input saturation and provides a poor load disturbance rejection performance, a modified IMC is introduced where a feedback control term is added to form a composite control structure. For the two current-loops, PI algorithms are employed respectively. Simulation and experimental results show the effectiveness of the proposed control method.

Control of reactive distillation columns for amyl acetate production using dilute acetic acid

This work explores the feasibility of recovery of acetic acid from aqueous solutions with different acid concentrations. Instead of separating acid from water using azeotropic distillation, acetic acid is converted to acetate via esterification. A range of acetic acid concentrations is explored, varying from 100 wt%, to 75 wt%, to 50 wt%, and then to 30 wt%. The Total Annual Cost (TAC) analysis shows that a standalone reactive distillation is more economical than a flowsheet with a pre‐treatment unit. Process characteristics have been explored and the results show significant nonlinearity associated with reactive distillation columns for all four different acid concentrations. A systematic design procedure is devised to control reactive distillation columns by temperature control. Reasonable control performance can be achieved. A further improvement can be made by incorporating feedforward control for feed flow disturbance. Finally, one‐temperature‐one composition control structure is also examined. Acceptable control performance can be obtained while maintaining acetate composition.

Force ripple suppression in iron-core permanent magnet linear motors using an adaptive dither

This paper presents the design and realization of an adaptive dither to reduce the force ripple in an iron-core permanent magnet linear motor (PMLM). A composite control structure is used, consisting of three components: a simple feedforward component, a PID feedback component and an adaptive feedforward compensator (AFC). The first two components are designed based on a dominant linear model of the motor. The AFC generates a dither signal with the motivation to eliminate or suppress the inherent force ripple, thus facilitating smooth precise motion while uncompromising on the maximum force achievable. An analysis is given in the paper to show the parameter convergence. Computer simulations and real-time experimental results verify the effectiveness of the proposed scheme for high precision motion trajectory tracking using the PMLM.

Reactor/separator processes with recycles-2. Design for composition control

This paper considers the plantwide control structure design for improved disturbance rejection. The balanced control scheme of ‘Comput. Chem. Eng. 20 (1996) 1291’ has the advantage of alleviating the snowball effect for plants with recycles by changing condition in several units in the process so as to distribute the work evenly among process units as production rate changes. However, the balanced scheme may lead to rather complex control configurations, especially for composition control. Based on steady-state disturbance sensitivity analyses, we are able to simplify the control structure by eliminating some of the compositions loops and still maintain a balanced partial composition control structure. More importantly, this is achieved with minimal process information, i.e., material balances and characteristics of the balanced scheme. For a simple recycle plant, results show that only one composition loop is sufficient to keep all three compositions near set points. A number of single composition control alternatives are explored. Two attractive alternatives are: (1) letting the reactor level uncontrolled or (2) using a proportional only reactor level controller. Nonlinear simulations show that effective composition control can be obtained with rather simple control structures.

Feedforward suppression of force ripple based on a simplex-optimized dither signal

Abstract This paper presents the design and realization of a feedforward dither signal to reduce the force ripple in an iron-core permanent magnet linear motor (PMLM). A composite control structure is used, consisting of three components: a simple feedforward component, a PID feedback component, and a ripple compensator (RC). The first two components are designed based on a dominant linear model of the motor. The dither signal is generated based on a signal model which is identified using a multidimensional simplex downhill method. In this way, a simple approach is available to eliminate or suppress the inherent force ripple, thus facilitating smooth precise motion while uncompromising on the maximum force achievable. Real-time experimental results verify the effectiveness of the proposed scheme for high precision motion trajectory tracking.

Learning-enhanced PI control of ram velocity in injection molding machines

This paper presents the development of a new learning enhanced PI control method for cyclical control of the ram velocity in injection molding machines. The overall structure of the control consists of a feedback and a feedforward component. The PI feedback control stabilizes the system, and the feedforward component incorporates an iterative learning control (ILC) algorithm to compensate for nonlinear/unknown dynamics and disturbances, thereby enhancing the performance achievable with feedback control alone. A simple and effective tuning method is further developed for the composite control structure which yields both the PI and ILC gains given only a first-order model. A nonlinear physical model derived for the process serves as the basis for the simulation study of the proposed control scheme. A comparison of the performance achieved with an optimally tuned PI control is also provided to highlight the advantages of the proposed control scheme.