Internal Model Control Principle Research Articles

A dynamic controller synthesis methodology for negative imaginary systems using the internal model control principle

This paper proposes a new controller design methodology for stable and minimum-phase Negative Imaginary (NI) systems relying on the classical Internal Model Control (IMC) principle. The closed-loop stability of the proposed scheme depends only on the DC loop gain, which is theoretically justified by the feedback stability results of the NI theory. The main objective is to design the Youla parameter of an IMC scheme, which has been cast as a Negative Imaginary (NI) controller synthesis problem. Two different methodologies have been proposed. A frequency-domain IMC design approach is first presented, which depends on solving a constrained, linear, least-square estimation problem. Then, an LMI-based methodology is developed, which can be solved by the commercially available SDP solver packages. An in-depth simulation case study on the vibration attenuation problem of a lightweight cantilever beam (a potential application of the NI theory) was carried out to demonstrate the usefulness of the NI-based IMC design methodology. Finally, the simulation results were experimentally validated on a custom-made vibration suppressor to confirm the feasibility of the proposed scheme.

An all-pass based internal model principle controller for galvanometer mirror steering

Galvanometer is a critical component for beam steering in additive manufacturing, profilometry, and medical imaging. In these applications, the quality of the process relies on the precision motion control of the galvanometer to either track or reject narrow-band signals. From the internal model principle, this can be accomplished by incorporating the dynamic model of the reference or disturbance signal in the feedback loop. This paper proposes an innovative internal model principle controller based on numerically robust all-pass filters. The main concept revolves around converting the controller design into a phase response design problem with all-pass filters. For the proposed approach, the targeted frequencies of the internal model can be arbitrarily placed without sacrificing the performance. Further, it produces lower-order controller and is robust against quantization effect. When combining with frequency estimation algorithm and adaptive filter, it can be readily applied to unknown and time-varying disturbance rejection. The advantages of the proposed method are demonstrated by comparing with conventional approaches through analysis, simulation, and experimentation.

Near-Complete Suppression of Harmonic Currents in SPMSMs Caused by Back EMF and Dead Time

This paper introduces a novel algorithm forsuppression of phase current harmonics in three-phase sinusoidal surface mounted permanent magnet synchronous machines (SPMSMs) caused by non-ideal back-emf waveform and dead-time effects. Proposed feedback acquisition chain obtains an exact information on all the relevant harmonics within each period of the fundamental. Design of the harmonic current controller based on the internal model control principle is given. The paper outlines the relevant details of implementation and the results of verification performed by both computer simulations and experimentally, using a laboratory prototype machine. Experimental results, obtained in presence of non-sinusoidal back-emf and with erroneous dead-time compensation, prove the ability of the proposed solution to remove the stator current harmonics quickly, in just two fundamental periods, and thus eliminate torque ripple.

Robust Predictive Control for Linear Permanent Magnet Synchronous Motor Drives Based on an Augmented Internal Model Disturbance Observer

To optimize the current-control performance of the linear permanent magnet synchronous motor (LPMSM) drive system, a robust continuous time model-based predictive control for the LPMSM drive systems is proposed in this article. Since the current regulation technology is fundamental for obtaining the precise thrust of the LPMSM, a continuous time model-based predictive control is utilized in the current loop to achieve a fast dynamic response and accurate tracking accuracy. However, the predictive control is a model-based scheme, thus, the model uncertainties and parameter variations will influence the accuracy of stator current. To solve this problem, an augmented internal model disturbance observer is proposed to estimate the lumped disturbances and then compensate to the forward channel. First, the internal model equation of the current loop is constructed by the internal model control principle. Then, a new augmented matrix is constructed by introducing the error variables of the actual current and the internal model current. The observer control law is designed by the state feedback theory, and the observer parameters are optimized by pole assignment method. Finally, the experimental results demonstrate the correctness and effectiveness of the proposed method.

Load Frequency Controller Design Based on the Direct Synthesis Approach Using a 2DoF-IMC Scheme for a Multi-Area Power System

To maintain reliable and sustainable power supply, the frequency should be kept constant under varying load conditions. The two degrees of freedom internal model control (2DoF-IMC) scheme is a robust control technique and is efficient for load-disturbance rejection problems in industrial process control. The asymmetry of IMC compared to other methods regarding controller design is that it does not guarantee the stability of the system by itself but is based on the stability of the controlled system. For the control of less-stable and unstable systems, it is therefore usually supplemented with an additional controller, establishing two degrees of freedom in the overall design. In this manuscript, the load-frequency-regulation problem was investigated using a 2DoF-IMC scheme for a single-area as well as a multi-area power system. In the 2DoF-IMC scheme, two controllers are used to control the set-point response and load-disturbance response separately. The set-point controller is designed through the internal model control (IMC) principle, whereas the load-disturbance rejection controller is designed via the direct-synthesis (DS) approach. In the DS approach, the closed-loop transfer function of the system model is matched with the desired closed-loop transfer function of the system and the disturbance-rejection controller is approximated at a very low-frequency point to obtain the proportional–derivative (PD) controller parameter. The simulation results of the proposed method provide satisfactory performance for load-frequency control (LFC) in the single-area power system and extended to two-area and four-area power systems. The effect of non-linearity, such as generation rate constraint (GRC), was investigated in the single-area power system to establish the efficacy of the proposed method. A random step loading pattern was also considered to confirm the robustness of the proposed method. The overall performance of the proposed control scheme is comparatively better than the recently reported work.

Linear active disturbance rejection control of servo systems via IMC principle with active damping and sliding mode techniques

In this paper, a new linear active disturbance rejection control (LADRC) is proposed for servo systems based on active damping (AD), internal model control (IMC) and sliding mode control (SMC). The IMC rules are applied to tune the controller gains for a prescribed tracking performance. The AD method injects a virtual damping force into the motion system to actively attenuate disturbances. By deriving the sliding dynamics of IMC, a boundary layer solution of SMC is employed to enhance the robustness of control system. As the improved robust IMC scheme is applied as the controller of LADRC, the uncompensated disturbance of linear extended state observer can be better suppressed. With this method, a higher tracking control accuracy is expected to be obtained in the presence of uncertain dynamics. Theoretical stability was analyzed based on the Lyapunov method. Comparative experiments were conducted on a permanent magnet synchronous motor to validate the superiority of the proposed approach.

Vibration control of a class of mechatronic systems using Negative Imaginary theory

This paper proposes a new controller design methodology for a class of mechatronics systems that satisfy stable and minimum-phase Negative Imaginary (NI) property. The proposed methodology relies on the classical Internal Model Control (IMC) principle. The closed-loop stability of the proposed scheme depends only on the DC loop gain, which is theoretically established by the internal stability result of NI theory. In this scheme, the design problem of the IMC parameter (known as the Youla parameter) has been cast as a Negative Imaginary (NI) controller synthesis problem. We propose an LMI-based IMC design approach, which can be readily solved using the commercially available SDP solver packages. A frequency-domain design approach is also presented, which depends on the solution of a simple constrained least-square problem. An in-depth simulation case study on the vibration attenuation problem of a lightweight cantilever beam is executed to demonstrate the usefulness and potential application of the proposed NI-based IMC scheme.

A Method of Robot Grinding Force Control Based on Internal Model Control Principle

The application of robots in the grinding industry can solve the problems in traditional artificial grinding, such as high labor intensity, low work efficiency, unguaranteed processing quality and serious physical injury to workers. In order to ensure the grinding quality, it is necessary to control the grinding force. The aims of this study is use PID-IMC controller to control the grinding force. Carry on the robot dynamics analysis to establish the dynamics model. Based on the principle of internal model control (IMC), PID controller is optimized and PID-IMC controller is obtained, which is used to realize the constant force control of robot grinding. Simulation and experiments results show that, the dynamics model and control method proposed in this paper have a better effect in the control of robot grinding force.

Design of PID Controllers for Pure Integrator Systems with Time Delay

In this paper, design of Proportional Integral and Derivative (PID) controllers based on internal model control (IMC) principles, direct synthesis method (DS), stability analysis (SA) method for pure integrating process with time delay is proposed. The performances of the proposed controllers are compared with the controllers designed by recently reported methods. The robustness of the proposed controllers for the uncertainty in model parameters is evaluated considering one parameter at a time using Kharitonov's theorem. The proposed controllers are applied to various transfer function models and to non linear model of isothermal continuous copolymerization of styrene-acrylonitrile in CSTR. An experimental set up of tank with the outlet connected to a pump is considered for implementation of the PID controllers designed by the three proposed methods to show the effectiveness of the methods.

Tuning of PID Controllers for Unstable Continuous Stirred Tank Reactors

Tuning Proportional Integral and Derivative (PID) controllers for unstable Second Order Plus Time Delay systems with a Zero (SOPTDZ), based on internal model control (IMC) and stability analysis (SA) principles is proposed. The controllers designed by the proposed methods are used to control unstable jacketed Continuous Stirred Tank Reactors (CSTR), carrying out irreversible first order reaction. The performance of proposed controllers is compared with the synthesis method. Simulation results on nonlinear unstable continuous stirred tank reactors and transfer function models are presented to the show the efficiency of the proposed controllers.

Dynamic Performance Improvement for Permanent Magnet Generator System Using Current Compensating Method With Two-Degrees-of-Freedom Control

This article proposes a two-degrees-of-freedom (TDOF) control with torque current compensating method (TCCM) to enhance the dynamic performance of permanent magnet generator (PMG) system when load changes. First, the mathematic model of PMG system with active front-end rectifier is introduced. Based on the system model, the proportional-integral controller of current loop is designed, and the TDOF controller designed with internal model control principle is derived for voltage loop control. There are two sets of parameters in the TDOF controller, one is used to regulate the system tracking performance when the command dc-link voltage changes, and the other is used to regulate the system antidisturbance capability when the electrical load changes. Second, the TCCM is proposed to further improve the system dynamic performance. The variation of torque current is applied to revise the command dc-link voltage, namely, the command dc-link voltage increases under loading occasion and decreases when unload occurs. The TCCM needs no additional hardware and is simple to implement. Simulation and experimental results verify the effectiveness of the proposed method.

VCSEL激光器抗干扰温度控制

Due to its low power consumption, small size, high modulation frequency and easy integration, VCSELs are widely used in the field of magnetic detection. As a high-precision sensor, the atomic magnetometer reduces the measurement accuracy due to the unstable output of the laser during the measurement of the magnetic field. A controller that can resist change in ambient temperature was designed to deal with the instability of the output of the laser due to environmental disturbance. Firstly, the high-resolution temperature solution was realized by the ADAU1401A chip with DSP core and DPSD method. Then the temperature control mathematical model was established by means of system identification. Finally, the disturbance observer and internal model control principle were applied to design anti-disturbance and low overshoot robust controller. The experimental results show that the control accuracy of interference is ±0.003 °C at 70 °C, and the control accuracy is ±0.001 5 °C at room temperature, which lays a foundation for stable output of laser and high-precision magnetic field measurement.

A Modified Cascade Control Strategy for Tobacco Re-Drying Moisture Control Process With Large Delay-Time

A novel series structure is proposed based on cascade control for dominating a class of unstable processes with large delay-times. The modified structure consists mainly of one controller that exists in the inner loop, and the inner loop controller is devised on the basis of internal model control (IMC) principles. The outer loop setpoint tracking controller and the inner loop load disturbance rejection controller are designed according to the H2 optimal performance. At the same time, the tuning parameters are selected through the experience approach. Moreover, a suitable example and real value are recommended for the inner loop controller based on a wide-ranging simulation, and the results are implemented to certify the effectiveness of the proposed method. Simultaneously, the proposed method is applied to in a real-world tobacco production line, and the test results prove that the above method is significant in terms of rapidity, robustness and residual errors.

Two-degree-of-freedom internal model position control and fuzzy fractional force control of nonlinear parallel robot

ABSTRACTThe paper proposes a novel method for the nonlinear redundantly actuated parallel robot based on force/position hybrid control structure. In order to solve the limitation of making a compromise for internal model controller, a two-DOF fractional order internal model control algorithm combining the internal model control principle and the fractional order theory is proposed for the position branch of the parallel robot redundantly actuated. This algorithm can realise the adjustment of the dynamic performance and anti-interference of 6PUS-UPU respectively. Aiming at the big force control error fractional order internal model, fuzzy control theory and the fractional order internal model controller are integrated into a new controller-fuzzy fractional order internal model(FFOIM) force control algorithm. Then Admas/Matlab simulation results demonstrate that the proposed algorithm can further reduce the driving force error of the system, and also retain the strong anti-interference of fractional order internal model controller.

IMC-based PID control of servo motors with extended state observer

In this paper, a simple and effective internal model control (IMC) with extended state observer (ESO) is presented for the position tracking control of servo motors perturbed by uncertainties and disturbances. Firstly, a linear feedback controller is directly derived from the standard IMC principle for a prescribed tracking performance. Then, a linear ESO is introduced into the IMC-based controller for active disturbance rejection control (ADRC). However, for the ESO with a limited bandwidth, there will exist state estimation errors, which limit the tracking accuracy. To overcome this drawback, 2-degree-of-freedom IMC-based PID controller with ESO is developed for further improvement of the control accuracy. The dynamics of the tracking error is analyzed based on an order reduction technique and the ultimately bounded stability of the control system can be guaranteed. Since the IMC scheme and the ESO can be designed separately and integrated effectively to attenuate the effect of disturbances, a simple, effective and intuitive framework can be given for the analysis and synthesis of the motion control system. Finally, the effectiveness of this novel control approach is validated by comparative simulations and experiments implemented on a practical servo motor system.

Improved Cascade Control System for a Class of Unstable Processes with Time Delay

An improved cascade control scheme is proposed based on modified Smith predictor for controlling a class of unstable processes with time delay. The proposed control structure consist three controllers of which the secondary loop has one controller and the primary loop has two controllers. The secondary loop controller is designed according to Internal Model Control (IMC) principles. The primary loop set point tracking controller and disturbance rejection controller are designed using the same procedure based on modified Smith predictor control structure. An analytical method on the basis of the Internal Model Control design principle is adopted for the two controllers which reduces complexity in design. The two controllers in primary loop are designed as proportional, integral and derivative (PID) controller cascaded with a lead-lag filter. Moreover, suitable values are recommended for the three controllers based on extensive simulations. Simulations studies are carried out to demonstrate the effectiveness of the proposed method.

Smart lighting system using ANN-IMC for personalized lighting control and daylight harvesting

Lighting contributes a significant portion to the overall energy consumption in an office building. It is thus important to reduce the energy consumption of lighting systems especially for Net Zero Energy Buildings (NZEB). Maximizing daylight harvesting can significantly increase the energy savings. With increase in demand for satisfying occupant preferences in visual comfort, the need for personalized lighting in the office space is also rising. In this paper, a novel lighting control system for Net Zero Energy Buildings (NZEB) is proposed which models the lighting system using Artificial Neural Network (ANN) and utilizes this model with the Internal Model Control (IMC) principle for controller design. Modeling the lighting system using ANN reduces the challenge of modeling a large and complex system with inherent process variability without the need to analyze extensive data-sets. The proposed ANN-IMC controller uses feedback from sensors on the task table to maintain desired illuminance, is easy to tune with just one parameter and is robust to process variability. The proposed control design is applicable to square systems where the number of lights and number of sensors are equal. However, the proposed architecture can also be extended for controlling other lighting accessories such as roller blinds. The performance of the proposed lighting control system to harvest the daylight effectively is demonstrated using both simulation results and an experimental setup in test-bed environment. The versatility of the proposed system will allow an operator to deploy personalized lighting in an office space.

Control Strategy for Dispatchable Distributed Energy Resources in Islanded Microgrids

This paper proposes a multi-input muti-output control strategy for dispatchable power electronic based distributed energy resources (DERs) in islanded mode operation of microgrids. The controller is designed based on the dq model of the DER unit. Cascade, feedforward, and internal model control principle, incorporating the theory of integral control and repetitive controller, are used. The proposed controller regulates the voltage at the output of DERs under any load (balanced, unbalanced, and harmonic) variation and/or fault condition. The stability of the closed-loop system has been investigated. Enhanced phase-locked loop (EPLL) is used to determine the system variables in the dq frame under unbalanced (and balanced) operating conditions. The structure of the EPLL is further modified to regulate the microgrid frequency and a stability analysis of proposed frequency control loop is presented. The performance of the proposed controller is verified through test case studies, carried out on an autonomous microgrid with single and multiple DER units.

Design and Validation of Fractional-Order Control Scheme for DC Servomotor via Internal Model Control Approach

ABSTRACTThis paper proposes a robust fractional-order controller for DC servomotor using internal model control and CRONE (Commande Robuste d'Ordre Non Entier) principle. The controller acquires a PID (proportional-integral-derivative) form followed by a fractional-order integrator. Unlike the conventional fractional-order PID controller which demands five tuning parameters, the proposed scheme has only two tuning parameters which can be obtained on the basis of desired gain crossover frequency and phase margin. For speed control problem, the performance of the proposed controller is studied on hardware set up called precision modular servo system. The proposed controller outperforms in terms of robustness and optimality when compared with controllers designed by integer-order technique. Furthermore, the proposed scheme is applied for position control problem and validated on QUBE-Servo 2 set up.

Process control performance evaluation in the case of variable set‐point with experimental applications

AbstractThe purpose of this paper is to contribute with some refinements to recent methods of analysis of control loop performance, based on the well‐established principle of Internal Model Control (IMC). Lower limits for the absolute value of the integral of control error (IAE) and the total variation of control action (TV) are assumed as reference values for a control considered good or at least acceptable. The overall performance index assumes as a benchmark a controller tuned according to rules of S(implified)IMC technique and is appropriately defined with respect to the lower limits of the two metrics IAE and TV. This allows the assessment of control loop performance, that is, the validity of tuning for PID‐type controllers in response to different types of reference change. In fact, one can assess performance in the case of set‐point changes as steps, ramps, or generic varying trends over time. In order to demonstrate the validity of the refined technique, several examples of simulation, case studies on a pilot plant, and real industrial data are presented.