Identification, digital control and fuzzy logic techniques applied to a synchronous generator

The experimental results obtained in the design and implementation of an decoupled digital speed and voltage controller for a micro-energy system are reported in this work. The studied system is formed by a 9 Kw DC motor driving a 10 KVA synchronous machine. There are two control loops in the proposed controller: the speed control (speed governor) and the control of the stator's voltage (automatic voltage regulator). Each control loop was designed using linear control techniques and fuzzy control techniques. Tests on the system show the performance of the proposed controllers.     

Development and implementation of an FPGA based fractional order controller for a DC motor

Fractional calculus has been gaining more and more popularity in control engineering in numerous fields, including mechatronic applications. One of the most common applications in all mechatronic domains is the control of DC motors. Several control algorithms have been proposed for such motors, ranging from traditional PID algorithms, to the more sophisticated advanced methods, including fractional order controllers. Nevertheless, very little information regarding the implementation problems of such fractional algorithms exists today. The paper proposes a simple approach for designing a fractional order PI controller for controlling the speed of a DC motor. The resulting controller is implemented on an FPGA target and its performance is compared to other possible benchmarks. The experimental results show the efficiency of the designed fractional order PI controller. Beside the initial DC motor, two other different DC motors are also used in the experiments to demonstrate the robustness of the controller.     

Advanced control strategy for a digital mass flow controller

Mass flow controllers are complex mechatronic devices, the design of which involves many techniques and skills in various scientific domains. Due to the slow response time of the sensors embedded in such devices, it is critically important to control gas flow variations in processes used in semiconductor industry. This paper shows how a digital controller for MFCs can be mathematically computed once the dynamic characteristics of the open-loop system have been identified. The proposed control method goes beyond prior art control methods as it explicitly takes into account the dynamics of the sensor, computes the digital controller appropriate to the order of the open-loop model and imposes a desired closed-loop transient response. The simulations performed and experimental results obtained with this new type of digital controller were very promising.     

Antiwindup Strategy for PI-Type Speed Controller

This paper proposes a new antiwindup strategy for PI speed controller to suppress the undesired side effect known as integrator windup when large set-point changes are made. When the speed control mode is changed from P control to PI control, an appropriate initial value for the integrator is assigned. This value then restricts the overshoot. In addition, the proposed method guarantees the designed performance independent of the operating conditions, i.e., different set-point changes and load torques, and can be easily implemented with existing PI controllers. In SIMULINK/MATLAB-based comparative simulations and experiments for a permanent-magnet synchronous motor speed controller, the proposed method shows a superior control performance compared with the existing well-known antiwindup methods, such as conditional integration and tracking back calculation.      

Control of High-Speed Solid-Rotor Synchronous Reluctance Motor/Generator for Flywheel-Based Uninterruptible Power Supplies

A hybrid controller, consisting of a model-based feedforward controller and a proportional–integral feedback compensator, for a solid-rotor synchronous reluctance motor/generator in a high-speed flywheel-based uninterruptible power supply application is proposed in this paper. The feedforward controller takes most of the control output of the current regulator based on the machine model, and the PI controllers compensate the possible inaccuracies of the model to improve the performance and robustness of the complete control system. The machine current tracking error caused by parameter inaccuracy in the model-based controller is mathematically analyzed and utilized to dynamically compensate the estimated flux linkage to eliminate the steady-state error in current regulation. Stability analysis is also presented, and it can be seen that the regulation performance and robustness of the system are improved by the proposed hybrid controller. Simulation and experimental results consisting of a flywheel energy storage system validates the performance of the controller.      

Design of incremental fuzzy PI controllers for a gas-turbine plant

In this paper, incremental fuzzy proportional integral (PI) speed and temperature controllers for a heavy-duty gas-turbine plant are presented. To improve performance, an analysis of incremental fuzzy PI control is provided, and new fuzzy control rules are proposed. In applying the fuzzy PI control to a gas-turbine plant, all gains are optimized by an adaptive genetic algorithm. We show the performance improvement of the proposed controller compared with conventional PI controller via simulations.     

永磁同步电机的双闭环调速系统设计

永磁同步电机因其优越的性能近年来得到了广泛应用。针对双闭环控制器参数整定困难所导致的控制效果不佳的问题,文中提出了基于极点配置和Ramp函数的改进型双闭环PI控制器。从永磁同步电机矢量控制算法的角度出发,建立了速度、电流双闭环解耦控制的系统模型,并在此模型下论述了速度环、电流环控制器的设计方法,给出改进后双闭环控制器参数的计算结果。对所研究方法分别进行了计算机仿真和实际试验,结果表明优化后的系统减小了系统过冲,缩短了稳定时间,提高了系统动态响应,具有良好的工程意义。     

Lagrangian modeling and passivity-based control of three-phase AC/DC voltage-source converters

In this paper, we investigate the dc-bus voltage regulation problem for a three-phase boost-type pulsewidth-modulated (PWM) ac/dc converter using passivity-based control theory of Euler-Lagrange (EL) systems. The three-phase PWM ac/dc converters modeled in the a-b-c reference frame are first shown to be EL systems whose EL parameters are explicitly identified. The energy-dissipative properties of this model are fully retained under the d-q-axis transformation. Based on the transformed d-q EL model, passivity-based controllers are then synthesized using the techniques of energy shaping and damping injection. Two possible passivity-based feedback designs are discussed, leading to a feasible dynamic current-loop controller. Motivated from the usual power electronics control schemes and the study of Lee, the internal dc-bus voltage dynamics are regulated via an outer loop proportional plus integral (PI) controller cascaded to the d-axis current loop. Nonlinear PI control results of Desoer and Lin are applied to theoretically validate the proposed outer loop control scheme. The PWM ac/dc converter controlled by the proposed passivity-based current control scheme with outer loop PI compensation has the features of enhanced robustness under model uncertainties, decoupled current-loop dynamics, guaranteed zero steady-state error, and asymptotic rejection of constant load disturbance. Experimental results on a 1.5-kVA PC-based controlled prototype provide verification of these salient features. The experimental responses of a classical linear PI scheme are also included for comparative study.     

Nonlinear control of mechatronic systems with permanent-magnet DC motors

The current trends in development and deployment of advanced electromechanical systems have facilitated the unified activities in the analysis and design of state-of-the-art motion devices, electric motors, power electronics, and digital controllers. This paper attacks the motion control problem (stabilization, tracking, and disturbance attenuation) for mechatronic systems which include permanent-magnet DC motors, power circuity, and motion controllers. By using an explicit representation of nonlinear dynamics of motors and switching converters, we approach and solve analysis and control problems to ensure a spectrum of performance objectives imposed on advanced mechatronic systems. The maximum allowable magnitude of the applied armature voltage is rated, the currents are limited, and there exist the lower and upper limits of the duty ratio of converters. To approach design tradeoffs and analyze performance (accuracy, settling time, overshoot, stability margins, and other quantities), the imposed constraints, model nonlinearities, and parameter variations are thoroughly studied in this paper. Our goal is to attain the specified characteristics and avoid deficiencies associated with linear formulation. To solve these problems, an innovative controller is synthesized to ensure performance improvements, robust tracking, and disturbance rejection. One cannot neglect constraints, and a bounded control law is designed to improve performance and guarantee robust stability. The offered approach uses a complete nonlinear mechatronic system dynamics with parameter variations, and this avenue allows one to avoid the conservative results associated with linear concept when mechatronic system dynamics is mapped by a linear constant-coefficient differential equation. To illustrate the reported framework and to validate the controller, analytical and experimental results are presented and discussed. In particular, comprehensive analysis and design with experimental verification are performed for an electric drive. A nonlinear bounded controller is designed, implemented, and experimentally tested.     

Adjustable speed control of ultrasonic motors by adaptive control

The driving principle of the ultrasonic motor (USM) is different from those of the electro-magnetic type motors. Some mathematical models for the USM have been reported; however, these models are very complex to apply for speed control of the USM. Therefore, the speed controllers have been designed using PI controllers or fuzzy controllers and it is necessary to develop a simple and convenient mathematical model for the USM in order to achieve a high-performance speed control. In this paper, a mathematical model for the USM is proposed which is simple and useful for speed control. The speed controller is designed based on the model using adaptive control theory. Adaptive control is attractive for control of the USM because the speed characteristics of the USM vary with drive conditions. The application of this control scheme to speed control for the USM is attempted first. The effectiveness of proposed control is demonstrated by experimental     

Gain scheduler middleware: a methodology to enable existing controllers for networked control and teleoperation - part I: networked control

Conventionally, in order to control an application over a data network, a specific networked control or teleoperation algorithm to compensate network delay effects is usually required for controller design. Therefore, an existing controller has to be redesigned or replaced by a new controller system. This replacement process is usually costly, inconvenient, and time consuming. In this paper, a novel methodology to enable existing controllers for networked control and teleoperation by middleware is introduced. The proposed methodology uses middleware to modify the output of an existing controller based on a gain scheduling algorithm with respect to the current network traffic conditions. Since the existing controller can still be utilized, this approach could save much time and investment cost. Two examples of the middleware applied for networked control and teleoperation with IP network delays are given in these two companion papers. Part I of these two companion papers introduces the concept of the proposed middleware approach. Formulation, delay modeling, and optimal gain finding based on a cost function for a case study on DC motor speed control with a proportional-integral (PI) controller are also described. Simulation results of the PI controller shows that, with the existence of IP network delays, the middleware can effectively maintain the networked control system performance and stabilize the system. Part II of this paper will cover the use of the proposed middleware concept for a mobile robot teleoperation.     

Identification and tuning fractional order proportional integral controllers for time delayed systems with a fractional pole

First order plus time delay model is widely used to model systems with S-shaped reaction curve. Its generalized form is the model with a single fractional pole replacing the integer order pole, which is believed to better characterize the reaction curve. In this paper, using time delayed system model with a fractional pole as the starting point, fractional order controllers design for this class of fractional order systems is investigated. Integer order PID and fractional order PI and [PI] controllers are designed and compared for these class of systems. The simulation comparison between PID controller and fractional order PI and [PI] controllers show the advantages of the properly designed fractional order controllers. Experimental results on a heat flow platform are presented to validate the proposed design method in this paper.     

Integrated design of mechanical structure and control algorithm fora programmable four-bar linkage

As the demand increases for machines of high accuracy, high speed, and high stiffness, programmable closed-loop linkages emerge in the development of modern machinery. A mechatronic design methodology is proposed for the integrated design of mechanical structure and control algorithm for a programmable closed-loop mechanism system. This design methodology suggests a negative mass-redistribution scheme, which follows the principle of a shaking force/shaking moment balancing scheme, for the modification of an existing four-bar mechanism, with the aim to obtain a simple system dynamic model and, thus, to facilitate controller design. In consequence, motion tracking performance and vibration behavior of the linkage system are significantly improved by simply applying a conventional PD control algorithm. The effectiveness of the proposed methodology has been verified by simulation studies     

Robustness evaluation of fractional order control for varying time delay processes

In this paper, we investigate the robustness of a methodology to design fractional order PI controllers combined with Smith Predictors, for varying time delay processes. To overcome the drawback of possible instability associated with Smith Predictor control structures, mainly due to the changes in the time delay, the design focuses on ensuring robustness of the closed loop system against time delay uncertainties. The proposed method is based on time-domain performance specifications??more accessible to the process engineer, rather than the more abstract notions related to the frequency domain. A second advantage of the proposed method relies on additional robustness to plant uncertainties, achieved by maximizing open-loop gain margin. The convergence problems associated with optimization techniques, previously used in fractional order controller designs, are eliminated by an iterative procedure in computing the gain margin. The simulation example provided demonstrates the efficiency of the proposed method, in comparison to classical integer order PI controller.     

Design of Mechatronic Systems With Configuration-Dependent Dynamics: Simulation and Optimization

This paper considers the simulation and optimization of mechatronic systems with configuration-dependent dynamics. A modeling methodology, able to capture the varying dynamics and the embedded control system actions, using affine reduced models and cosimulation, is proposed. In this way, mechatronic systems with configuration-dependent dynamics can be evaluated during the design phase. This methodology is applied to a pick-and-place assembly robot and an experimental validation is carried out. The mechatronic design approach, which takes into consideration structural and control parameters, is considered. Using time-domain metrics, two control strategies are derived: a linear time-invariant proportional--integral--derivative (PID) controller and a linear parameter-varying PID controller. Finally, design tradeoffs are evaluated in a truly mechatronic approach.      

Adaptive learning algorithm for Cerebellar model articulation controller

Cerebellar model articulation controller (CMAC) was developed two decades ago, yet lacks an adequate learning algorithm. Examining the performance of a CMAC based controller showed that the control system become unstable after a long period of real time runs. A new adaptive learning algorithm is proposed. The resultant controller is applied for the trajectory tracking control of a piezoelectric actuated tool post. The performance of the proposed controller is compared with those of conventional controllers (PI controller and the conventional CMAC based controller). The experimental results showed that performance of the CMAC based controller using the proposed learning algorithm is stable and more effective than that of the conventional controllers.     

Offset-Free Model Predictive Control for a cone-shaped active magnetic bearing system

Active Magnetic Bearings (AMB) are mechatronic systems that support a rotating shaft using magnetic levitation. The standard AMB architecture includes two radial actuators and one for the axial direction. An alternative geometry with cone-shaped magnetic cores allows for a more compact layout without a dedicated axial actuator. However, this configuration reduces the axial force generation capability and requires a more complex control architecture due to the inherent coupling of the axial and radial control actions. When using decentralized control, effective handling of the coil current limitations together with the axial disturbance rejection is difficult to achieve. In this context, the present paper demonstrates the benefits of applying Offset-Free Model Predictive Control (OF-MPC) for a cone-shaped AMB system. A procedure for the overall design is presented and supported by the experimental work conducted in a scaled machine that reproduces an on-board turbo-compressor unit for an aircraft. The modeling of the system is described together with the design of the OF-MPC in all its parts: general control architecture, disturbance model and observer design, target calculation and control problem formulation. An OF-MPC variant with reduced control horizon is proposed and implemented in real time. Experimental results demonstrate that the prototype is compliant with application-specific stability requirements from the ISO 14839-3:2006 standard. In addition, experiments show that OF-MPC outperforms decentralized PID controllers in terms of axial disturbance rejection. OF-MPC yields a favorable constrained optimal control technique for cone-shaped AMBs because intrinsic coupling and current saturation are optimally handled by the controller.     

基于MATLAB的直流调速数字控制系统的分析和设计

直流调速系统的数字化控制已得到广泛应用。文中简单介绍了直流调速系统数字控制的特点和直流调速系统模型的建立,重点介绍了数字PI控制器和利用Z域根轨迹的设计方法,以及用MATLAB进行了设计过程的仿真和稳定性、动态特性的分析。     

Application of Memristor-Based Controller for Loop Filter Design in Charge-Pump Phase-Locked Loops

In this work, a monotonic increasing piecewise-linear (PWL) memristor-based proportional-integral (PI) controller is analyzed. A periodic rectangular pulse current source is used as the input signal, and the proportionality constant of the PWL memristor-based PI controller is varied according to the amount of charge that passes through the memristor. A circuit is proposed to achieve zero net-charge injection for the memristor so that the memristance of the PWL memristor can be varied in the subsequent period. The proposed PWL memristor-based PI controller can be used in the design of the loop filter for the charge-pump phase-locked loop for achieving a faster dynamical response from an unlocked state to a locked state compared to conventional fixed proportional constant PI controllers.