Cascade Control Strategy Research Articles

Improved Self-Sensing Speed Control of IPMSM Drive Based on Cascaded Nonlinear Control

This paper presents a nonlinear cascaded control design that has been developed to (1) improve the self-sensing speed control performance of an interior permanent magnet synchronous motor (IPMSM) drive by reducing its speed and torque ripples and its phase current harmonic distortion and (2) attain the maximum torque while utilizing the minimum drive current. The nonlinear cascaded control system consists of two nonlinear controls for the speed and current control loop. A fuzzy logic controller (FLC) is employed for the outer speed control loop to regulate the rotor shaft speed. Model predictive current control (MPCC) is utilized for the inner current control loop to regulate the drive phase currents. The nonlinear equation for the dq reference current is derived to implement the maximum torque per armature (MTPA) control to achieve the maximum torque while using the minimum current values. The model reference adaptive system (MRAS) was employed for the speed self-sensing mechanism. The self-sensing speed control performance of the IPMSM motor drive was compared with that of the traditional cascaded control schemes. The stability of the sensorless mechanism was studied using the pole placement method. The proposed nonlinear cascaded control was verified based on the simulation results. The robustness of the control design was ensured under various loads and in a wide speed range. The dynamic performance of the motor drive is improved while circumventing the need to tune the proportional-integral (PI) controller. The self-sensing speed control performance of the IPMSM drive was enhanced significantly by the designed cascaded control model.

Thrust vector control of constrained multibody systems

This paper presents a general control framework for the constrained control of multibody systems actuated by vectorized thrusters. A cascade control scheme augmented with a constraint-enforcement unit is proposed to stabilize the system while ensuring constraint satisfaction at all times. The cascade controller consists of an inner loop and an outer loop that are interconnected by a suitable mapping. The inner loop is tasked to control the attitude of the vectorized thrusters. The outer loop is designed to steer the task configuration of the system to a desired pose, while providing to the inner loop the desired attitude through a mapping. To prove the stability of the interconnected system, input-to-state stability (ISS) and small gain arguments are used. All stability properties are derived in the absence of constraints and are shown to be local. Hence, the control scheme is augmented with a Reference Governor (RG) to enforce constraints at all times. Simulations on an unmanned tiltrotor docked to a stationary platform for a refueling operation are carried out to demonstrate the effectiveness of the proposed control framework.

Cascade ADRC Speed Control Base on FCS-MPC for Permanent Magnet Synchronous Motor

Due to the complication control structure and heavy burden in computation of the Permanent Magnet Synchronous Motor (PMSM) control strategy, a new cascade control strategy is proposed, which is combined with advanced control algorithm of Active Disturbance Rejection Control (ADRC), Finite Control Set Model Predictive Control (FCS-MPC) and Kalman filtering. ADRC is designed in detail for speed control, in order to reduce the burden of Extended State Observer (ESO) in ADRC, a Kalman filter is designed to simultaneously observe load disturbance and back Electromotive Force (EMF), which can also reduce influence of the noise. While the estimated EMF is used for the current loop FCS-MPC control, it is improved with a method of best vector selection and duty cycle optimization. The proposed combined control scheme is verified in MATLAB simulation environment, through detailed analysis, it shows both good performance in steady state and dynamic response.

Magnetic tweezers with magnetic flux density feedback control.

In this work, we present a single-pole magnetic tweezers (MT) device designed for integration with substrate deformation tracking microscopy and/or traction force microscopy experiments intended to explore extracellular matrix rheology and human epidermal keratinocyte mechanobiology. Assembled from commercially available off-the-shelf electronics hardware and software, the MT device is amenable to replication in the basic biology laboratory. In contrast to conventional solenoid current-controlled MT devices, operation of this instrument is based on real-time feedback control of the magnetic flux density emanating from the blunt end of the needle core using a cascade control scheme and a digital proportional-integral-derivative (PID) controller. Algorithms that compensate for a spatially non-uniform remnant magnetization of the needle core that develops during actuation are implemented into the feedback control scheme. Through optimization of PID gain scheduling, the MT device exhibits magnetization and demagnetization response times of less than 100ms without overshoot over a wide range of magnetic flux density setpoints. Compared to current-based control, magnetic flux density-based control allows for more accurate and precise magnetic actuation forces by compensating for temperature increases within the needle core due to heat generated by the applied solenoid currents. Near field calibrations validate the ability of the MT device to actuate 4.5 μm-diameter superparamagnetic beads with forces up to 25 nN with maximum relative uncertainties of ±30% for beads positioned between 2.5 and 40 µm from the needle tip.

Effective semicontinuous distillation design for separating normal alkanes via multi-objective optimization and control

As a process intensification technology, semicontinuous distillation uses less equipment to achieve the separation of multiple components. However, there is still a lack of systematic guidance for the design of semicontinuous distillation. In this paper, we propose a new method to guide the design of semicontinuous distillation via multi-objective optimization (MOO) and control. Conventional continuous distillation, dividing wall column (DWC) distillation and semicontinuous distillation for separation of n-alkanes are optimized through multi-objective genetic algorithm (MOGA). Several different control schemes are proposed for semicontinuous distillation, and the temperature-concentration cascade control scheme CS5 is selected as the optimal control scheme. The economic benefits of semicontinuous distillation based on dynamic simulation are evaluated by the comparison with the conventional continuous distillation and DWC under a series of throughput. It is found that the total annual cost (TAC) of the semicontinuous distillation is smaller than that of conventional continuous distillation when the annual throughput is less than 7.73 × 104 kmol/yr. And the TAC of the semicontinuous distillation is less than that of DWC when the annual throughput is less than 5.29 × 104 kmol/yr. Therefore, we can conclude that the semicontinuous distillation has better economic benefits than the other two configurations within the smaller annual throughput.

Virtual Synchronous Generator and SMC-Based Cascaded Control for Voltage-Source Grid-Supporting Inverters

The voltage-source grid-supporting inverters (GSIs) are important to establish and support the frequency and voltage of a microgrid (MG) in both islanded and grid-connected modes. Traditionally, a cascaded control strategy that includes an external droop-based control loop and an inner proportional-integral (PI)-based voltage and current control loop is adopted to control a GSI, which barely shows inertia and limited control performance. In this article, a novel cascaded control strategy is proposed for a GSI. In the external loop, a VSG-based control strategy is adopted to increase the frequency stability of the MG, and a novel synchronization control method that does not use a complex PLL unit is proposed to satisfy the plug-and-play requirements of a GSI. In the inner voltage and current control loop, this article proposes an SMC-based vector control strategy which uses the fixed switching frequency and inherits the robustness and fast response speed of the SMC control. Both simulation and experiments demonstrate the effectiveness and improved performance of the proposed control strategy.

Enhancing rotor angle stability of power systems using marine predator algorithm based cascaded PID control

In this paper, the cascaded control scheme is introduced for the first time to the rotor stability problem. Cascaded excitation and governing control schemes are introduced to damp rotor oscillations. PID cascaded control is used for its popularity and effectiveness. These controllers will be fine-tuned using a novel metaheuristic optimization technique, namely the Marine Predator Algorithm; which mimics the movement of marine predators when foraging. This technique is popular for always converging to a constant stable point. Our study will be performed on two systems, the simple single machine to infinite bus power system and the popular IEEE-39 bus system to study both local and global oscillations, respectively. Results show the effectiveness of the new proposed cascaded control scheme compared to the conventional scheme in improving the damping of the rotor oscillations without the need of a power system stabilizer. Results are provided as time domain simulation via MATLAB/SIMULINK.

An intelligent two‐level control of Ultrabattery for improved automatic generation control of a multi‐source deregulated power system

This article studies automatic generation control (AGC) problem of a realistic, multi-source deregulated power system with thyristor controlled phase shifter (TCPS) in the tie-line for damping the inter-area power oscillations. In this direction, an intelligent integration of a commercially available, relatively low rating efficient energy storage system in the form of Ultrabattery for AGC enhancement is proposed. Herein, a two-level supervisory cascade control scheme is designed. The supervisory controller comprises of a genetically tuned fuzzy logic controller which ensures the operation of Ultrabattery within its regime of operation while supervising a conventional main controller in the inner loop. The exchange of desired power between the power system and Ultrabattery is governed by the main controller whose parameters are tuned offline using optimization toolbox in MATLAB. To make the power system model realistic, effects of generation rate constraint, governor dead band, boiler dynamics, and communication time delay have been incorporated. Extensive simulation studies conducted on a well-known benchmark two-area power system under various market scenarios demonstrate the effectiveness of the proposed scheme. The results obtained illustrate a substantial mitigation of low magnitude oscillations with TCPS in the tie-line. Following the introduction of an Ultrabattery rated at just 1% of the area capacity in coordination with TCPS, an improvement of at least 87% in the system performance index is achieved. Finally, a sensitivity analysis validates the robustness of the proposed scheme under varying system parameters and market scenarios.

Modeling and Simulation of Three Phase Power Factor Correctors with Fast Dynamic Response based on Fixed PWM and Bang-Bang control Techniques using DC-DC SEPIC Converter Modules

The main concerns of the power supply industry is to obtain a single stage converter with a low-cost for achieving power factor correction (PFC) complying with required harmonic standards and regulated output voltage simultaneously for three-phase applications. This paper presents the modelling and simulation of single stage three phase power factor correctors using DC-DC SEPIC converter modules based on cascade control strategy. It uses outer loop using proportional-integral (PI) controller to regulate the output voltage and three inner fixed PWM/bang-bang controllers to shape the source current. PI controller parameters are determined by using TYREUS-LUYBEN tuning method. Performance analysis has been made for the two proposed approaches by comparing the simulation results. Results reveal that the proposed scheme provides the power factor close to unity, low % total harmonic distortion (THD), regulated output voltage for load variations and effective set point tracking. Experimental results using fixed PWM technique is also presented.

Nonlinear Observer Based on Linear Matrix Inequalities for Sensorless Grid-tied Single-stage Photovoltaic System

The objective of this work is to design a Nonlinear Observer used in a Cascade Control scheme for Maximum Power Point Tracking goals of a grid-tied single-phase photovoltaic inverter. ...

LAMDA Control Approaches Applied to Trajectory Tracking for Mobile Robots

This paper presents the application of different approaches of intelligent controllers based on LAMDA (Learning Algorithm for Multivariate Data Analysis) to perform the trajectory tracking task of a mobile robot Pioneer 3-DX simulated in the Virtual Robot Experimentation Platform V-REP environment. The paper proposes the design of a cascade control strategy composed of two controllers, the external controller based on a feedback linearization for the robot kinematics and the internal controller applied to the robot dynamics where the LAMDA approaches are applied. In this work, it is considered an uncertain dynamic model. Thus, its identification and control are based on a reduced-order model for designing purposes. Finally, the dynamic controller is designed using different controllers based on LAMDA, such as LAMDA-PID, LAMDA-Sliding Mode Control, and Adaptive LAMDA. To perform a comparative analysis between them that includes a conventional PID, SMC, and Fuzzy-PID, different trajectories are examined to evaluate the methods. The obtained results are compared qualitatively and quantitatively to determine which proposal performs the most accurate control and presents the best results in terms of performance.

Multi-model cascade control strategy design based on gap metric for nonlinear processes

ABSTRACT A multi-model control system in cascade configuration using hard and soft switching for the nonlinear process is addressed in this research. Cascade control is a widely known strategy in process plants to improve control performance in the presence of disturbances. It has been found that the incorporation of conventional cascade controllers was ineffective when applied to nonlinear processes. Multi-model control schemes are capable of providing enhanced performance when compared to the conventional control schemes for nonlinear systems. This paper presents the multi-model approach (MMA) in the cascade control strategy by using hard and soft switching for selection of the controller. Simulation studies are demonstrated on nonlinear processes (isothermal CSTR, conical tank and spherical tank) and experimentally applied on the conical tank process. The performance of the cascade multi-model control strategy is superior when compared to the classical multi-model control strategy. It is observed that the cascade multi-model control strategy has provided faster response and improved disturbance rejection.

An Anti-wind Modeling Method of Quadrotor Aircraft and Cascade Controller Design Based on Improved Extended State Observer

Wind disturbance may significantly reduce the flight control performance of quadrotors when flying. In order to meet high performance flight control requirements, this paper presents a quadrotor anti-wind model (QAWM) and a flight control scheme for quadrotors. The QAWM takes the influence of aerodynamic effects on the propeller, gyroscopic effect and wind disturbance into account. The model can represent more flight states including not only hovering but also flight in windy conditions even maneuver flight. A cascade control scheme with an improved extended state observer (IESO) is adopted to decompose the quadrotor flight control problem into position control loop and attitude control loop. In the attitude control loop, the IESO is used to estimate the unmodeled dynamics, parameter uncertainties and external disturbances, as well as compensate the angular velocity control. In addition, the stability of IESO and the closed loop system are proved. Simulation and experimental results show the effectiveness of the nonlinear quadrotor model and control scheme, and the control scheme can effectively improve the flight performance of quadrotors under wind disturbance even maneuver flight.

The algorithm of adaptive control for active suspension systems using pole assign and cascade design method

This paper presents the active suspension system (ASS) control method using the adaptive cascade control scheme. The control scheme is implemented by two control loops, the inner control loop and outer control loop are designed respectively. The inner control loop uses the pole assignment method in order to move the poles of the original system to desired poles respect to the required performance of the suspension system. To design the controller in the inner loop, the model without the noise caused by the road profile and velocity of the car is used. The outer control loop then designed with an adaptive mechanism calculates the active control force to compensate for the vibrations caused by the road profile and velocity of the car. The control force is determined by the error between states of the reference model and states of suspension systems, the reference model is the model of closed-loop with inner control loop without the noise. The simulation results implemented by using the practice date of the road profile show that the capability of oscillation decrease for ASS is quite efficient

Speed cascade adaptive control for hybrid electric vehicle using electronic throttle control during car-following process

Achieving robust longitudinal speed control for hybrid electric vehicles (HEVs) through precise position tracking of electric throttle control system (ETCS) can improve engine fuel economy and vehicle longitudinal speed performance. Whereas, nonlinearities resulting from friction, gearbox, and return springs of ETCS, uncertain system parameters related to production deviations and device aging, disturbance from the air flow fluctuation on the throttle plate, and unknown road grade and uncertain preceding vehicle acceleration make control design challenging. Aiming at this issue, a speed cascade control scheme considering car-following scenario is investigated for a parallel ETCS controlled HEV in this paper, of which contains a primary speed adaptive controller and a secondary electronic throttle adaptive nonlinear active disturbance rejection controller with the adaptive gains extended state observer. The distinction from the existing relevant literatures is that the inherent characteristics of nonlinearity and uncertainty in the ETCS and longitudinal velocity kinematics, and the car following scenarios are explicitly taken into account in the design of the cascade control for ETCS controlled HEVs. Both simulation and rapid-control-prototype (RCP) experimental results demonstrate the effectiveness and practicality of the proposed scheme and the advantages over other existing research strategies.

Optimal Fractional Order IMC-Based Series Cascade Control Strategy with Dead-Time Compensator for Unstable Processes

In industrial unstable processes, disturbance rejection is more challenging task than setpoint tracking. So, cascade control structure is widely used in many chemical processes to reject disturbances. In this work, an advanced dead-time compensator-based series cascade control structure (SCCS) is suggested for unstable processes. The suggested SCCS has three controllers (named as primary, secondary and stabilizing controllers). Both primary and secondary controllers are designed using fractional order-based internal model control (IMC) approach. The stabilizing proportional–derivative controller is designed using maximum sensitivity considerations and Routh–Hurwitz stability criteria. Optimal values of the closed-loop time constants and fractional orders of IMC filters are obtained using constrained artificial bee colony (ABC) algorithm. This ABC algorithm uses a multi-objective function involving minimization of integral of absolute error, integral of time weighted absolute error and integral of squared error. Simulation studies are conducted using some benchmark plant models used in literature for illustrating the advantages of the proposed strategy compared to the state of the art. Moreover, robust stability of the proposed design is analysed and quantitative performance measures are also computed.

Invasive Weed Optimized Area Centralized 2 Degree of Freedom Combined PID Controller Scheme for Automatic Generation Control

Frequency disturbances caused by load perturbations of multi area interconnected power system are reduced by using proper control schemes provided via secondary control loop along with primary control of generation plants. These secondary controllers provide simultaneous control signal to individual machines of a particular area when the control scheme is area centralized. This area centralized mechanism provides quick control action with less computational burden since control problem dimensions gets reduced even the area consists multiple plants/machines. Such centralized new cascade control scheme is proposed in this paper to supervise the secondary control mechanism and it is implemented with parallel connection of 2-Degree of Freedom Proportional-Integral-Derivative (2-DOF PID) controller combined with regular PID controller. The performance of this new controller is studied on multi area multi machine interconnected power system with participation factor concept and later its relative performance in terms of dynamic and steady state specifications are compared with conventional PID and 2-DOF PID controllers. These control parameters are tuned by Invasive Weed Optimization (IWO) algorithm to achieve better system outputs. Case studies presented in this paper show the advantages of proposed control scheme.

Cascade Control Strategy on Servo Pneumatic System with Fuzzy Self-Adaptive System

Servo pneumatic position control has gained considerable attention due to its superiority in improving the precision of automation and mechatronic systems. This paper presents the proposed cascaded fuzzy self-adaptive with proportional, integral, and derivative (CFSAPID) control strategy in providing an accurate rod-piston displacement as desired input with stable pressure in chambers. Unlike the conventional cascade strategy, the control law of proposed CFSAPID was designed based on the Mamdani-type fuzzy approach as a dynamic tuner to each stage in the proportional, integral, and derivative (PID) controller that deals with the nonlinearity of servo pneumatics adequately. The bounder sector zone of Mamdani-type fuzzy was determined based on position and velocity states on servo pneumatic rod–piston, and the parameter was constructed to obtain the optimum gain parameters of PID in each stage. The proposed CFSAPID was verified using a pneumatic proportional valve with a double-acting cylinder dynamic model plant. Simulation and analyses were emphasized on steady-state error, difference in pressures of pneumatic cylinder’s chambers, hysteresis effect, tuning parameters convergence, performance criteria, and performance indices. The results show that the proposed CFSAPID controller was able to withstand the load disturbances, at variable input trajectory with a stable pressure in chambers at almost minimum hysteresis effect compared to the FSAPID and single PID controllers.

Parametric eigenvalue assignment by constant output feedback – a cascaded approach

Abstract In this paper a numerical efficient approach to the problem of eigenvalue assignment by constant output feedback is presented. It improves the well known Kimura’s condition by 2, i. e., it is shown that if m + p ≥ n − 1 m+p\ge n-1 generically a solution to this design problem exists where n , m n,m and p denote the dimensions of the system states, inputs and outputs, respectively. The algorithm is based on a cascaded control scheme with up to three design steps. The first two steps merely require standard methods from linear algebra while the last step only in case of m + p = n − 1 m+p=n-1 demands for the numerical solution of a system of three polynomial equations each of order two. The design procedure explicitly embodies all degrees of freedom beyond eigenvalue assignment. Thus, they can be used to account for other design it is shown goals, e. g., to minimize the spectral condition number of the closed-loop system or a norm of the feedback gain as it is shown by numerical examples from literature.

A new control strategy for a higher order proton exchange membrane fuel cell system

In this paper, a new cascade control strategy is proposed for a higher order Proton Exchange Membrane (PEM) Fuel Cell system for improving the performance on the basis of stack voltage. In the proposed strategy, stack voltage is considered as the primary objective and maintaining oxygen excess ratio value as a secondary aim, by manipulating the air compressor voltage. A higher-order PEMFC model is reduced to lower order integer and fractional models using varied model reduction techniques, which are then used to realize the primary as well as secondary controllers. Both integer and fractional order PID controllers are designed for the reduced order models and then implemented for the higher order system. The control performance is evaluated for disturbance rejection, system model mismatch and better controlled output for continuous random disturbance on the basis of Integral Absolute Error and controller effort. The outcome of the proposed control strategy is advantageous in terms of disturbance rejection, robustness, parameter uncertainty and reduction of plant-model mismatch.