Torque and current control of high-speed motion control systems with sinusoidal-PMAC motors

Describes a torque- and current-control application to a commercial motion-control system with sinusoidal permanent magnet ac (PMAC) motors. The control approach is based on maximization of torque-per-amp ratio. The proposed torque controller, in the form of torque feedforward plus proportional-integral (PI)-type torque feedback, utilizes the feedback of nominal torque signal only, a signal that can be readily calculated, online. No torque sensor is required. Through proper design of the desired nominal torque with adaptive control, the proposed torque controller can overcome disturbances due to torque estimation error and model uncertainties. A discrete-time approach is developed for inner-current loop control design. The inner-loop control gains, which are hard to obtain through manual tuning in practice, are determined by a dynamic model-based calculation methodology. Experimental evaluation on a commercial motion control system demonstrates the validity of the proposed approach in high-speed motions.     

Real-time carbon content control for PECVD ZrO/sub 2/ thin-film growth

We present a methodology for real-time control of thin-film carbon content in a plasma-enhanced metal-organic chemical vapor deposition process using combination of online gas phase measurements obtained through optical emission spectroscopy and off-line (ex situ) measurements of film composition obtained via X-ray photoelectron spectroscopy (XPS). Initially, an estimation model of carbon content of ZrO/sub 2/ thin films based on real-time optical emission spectroscopy data is presented. Then, a feedback control scheme, which employs the proposed estimation model and a proportional-integral controller, is developed to achieve carbon content control. Using this approach, a real-time control system is developed and implemented on an experimental electron cyclotron resonance high-density plasma-enhanced chemical vapor deposition system to demonstrate the effectiveness of real-time feedback control of carbon content. Experimental results of depositions and XPS analysis of deposited thin films under both open-loop and closed-loop operations are shown and compared. The advantages of operating the process under real-time feedback control in terms of robust operation and lower carbon content are demonstrated.     

Vector control for induction machine on the application of optimalcontrol theory

An approach for constructing a field-oriented control system using the state-space method is proposed. The field-oriented control system can be realized by coinciding the synchronously rotating reference frame with the axes of the secondary flux linkage reference frame and by simultaneously but independently adjusting the three control inputs. A control-system synthesis method that achieves speed control, field-oriented control, and constant flux control simultaneously is presented. The control system has a full-state feedback structure and is synthesized by applying a multi-input and multi-output optimal regulator theory. The excellent robustness of the constructed system results in zero steady-state errors for changes in parameters such as rotor resistance. The validity of the control scheme is verified by simulation studies. Results are presented for a field-oriented induction motor driven by a PWM (pulse-width modulation) inverter     

Fault-tolerant control system of flexible arm for sensor fault by using reaction force observer

In recent years, control system reliability has received much attention with increase of situations where computer-controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and to maintain the stability and the control performance (fault tolerance). In this paper, we address the vibration suppression control of a one-link flexible arm robot. Vibration suppression is realized by an additional feedback of a strain gauge sensor attached to the arm besides motor position. However, a sensor fault (e.g., disconnection) may degrade the control performance and make the control system unstable at its worst. In this paper, we propose a fault-tolerant control system for strain gauge sensor fault. The proposed control system estimates a strain gauge sensor signal based on the reaction force observer and detects the fault by monitoring the estimation error. After fault detection, the proposed control system exchanges the faulty sensor signal for the estimated one and switches to a fault-mode controller so as to maintain the stability and the control performance. We apply the proposed control system to the vibration suppression control system of a one-link flexible arm robot and confirm the effectiveness of the proposed control system by some experiments.     

Generalized digital redesign method for linear feedback systembased on N-delay control

A new digital redesign method is proposed for feedback control systems, by which the states in the continuous-time system are completely reserved in the redesigned sampled-data system. The features of the proposed method are: 1) the N-delay control is employed, and the lth plant input is changed N_l times during one sampling period; 2) the states of the redesigned sampled-data system completely match those of the original continuous-time closed-loop system at every sampling period; and 3) the proposed redesign method can be applicable for a static state-feedback and/or a dynamic controller. An illustrative example of position control using a DC servo motor is presented. The advantages of the proposed redesign approach are demonstrated both in the time and frequency domains     

Perfect tracking control based on multirate feedforward controlwith generalized sampling periods

In this paper, a novel perfect tracking control method based on multirate feedforward control is proposed. The advantages of the proposed method are that: (1) the proposed multirate feedforward controller eliminates the notorious unstable zero problem in designing the discrete-time inverse system; (2) the states of the plant match the desired trajectories at every sampling point of reference input; and (3) the proposed controller is completely independent of the feedback characteristics. Thus, highly robust performance is assured by the robust feedback controller. Moreover, by generalizing the relationship between the sampling period of plant output and the control period of plant input, the proposed method can be applied to various systems with hardware restrictions of these periods, which leads to higher performance. Next, it is shown that the structure of the proposed perfect tracking controller is very simple and clear. Illustrative examples of position control using a DC servomotor are presented, and simulations and experiments demonstrate the advantages of this approach     

利用跟踪控制实现单模激光lorenz系统和新系统的混沌同步

分析了单模激光Lorenz系统和新系统的动力学特性.基于非线性反馈控制器的设计,利用跟踪控制使处于混沌和超混沌的两系统之间的拓扑不等价的异结构混沌系统成功地达到了混沌同步,依据线性稳定性理论分析,确定了控制系统的稳定性.数值模拟表明,通过适当地选择反馈增益系数,响应系统得到了有效控制.由于控制过程中无需计算Lyapunov指数,异结构混沌系统间的拓扑结构亦可以有较大差异,可降低混沌控制工作量和提高保密通信的性能.     

Observer-corrector control design for robots with destabilizing unmodeled dynamics

Industrial robotic manipulators and other mechatronic systems often possess undesirable higher order dynamics exhibited in the form of resonance conditions which affect closed-loop stability when feedback control is applied. In this study, an alternative reduced-complexity control design strategy is presented. The fundamental idea of the proposed approach is to synthesize a substitute feedback signal which reflects the dominant dynamics essential for operation of the system subject to control but does not include the undesirable higher order dynamic effects. A unique arrangement of a band-limited state observer and a low-pass filter corrector is employed for this purpose, providing a mechanism to extract the dominant dynamics from the output of the system with minimal amplitude and phase distortion. The resulting synthetic signal is used as a controller input, effectively eliminating destabilizing effects of the undesirable higher order dynamics. As a result, the controller can be designed practically without taking the higher order dynamic effects into account, which allows for use of conventional control techniques, and translates into reduced modeling requirements, simplified controller design and shorter development time when compared to a complete dynamic analysis. The effectiveness of the proposed concept is demonstrated experimentally on motion control of a four-axis direct-drive robotic manipulator for automated pick-place operations in semiconductor manufacturing applications. It is concluded that the proposed control design strategy provides improved control performance, increased stability margin, and added robustness against variations in system parameters in comparison to common methods adopted currently in the engineering practice.     

Precise position control of shape memory alloy actuator using inverse hysteresis model and model reference adaptive control system

Position control of Shape Memory Alloy (SMA) actuators has been a challenging topic during the last years due to their nonlinearities in the governing physical equations as well as their hysteresis behaviors. Using the inverse of phenomenological hysteresis model in order to compensate the input–output hysteresis behavior of these actuators shows the effectiveness of this approach. In this paper, in order to control the tip deflection of a large deformation flexible beam actuated by an SMA actuator wire, a feedforward–feedback controller is proposed. The feedforward part of the proposed control system, maps the beam deflection into SMA temperature, is based on the inverse of the generalized Prandtl–Ishlinskii model. An adaptive model reference temperature control system is cascaded to the inverse hysteresis model in order to estimate the SMA electrical current for tracking the reference signal. In addition, a closed-loop proportional–integral controller with position feedback is added to the feedforward controller to increase the accuracy as well as eliminate the steady state error in position control process. Experimental results indicate that the proposed controller has great accuracy in tracking some square wave signals. It is also experimentally shown that the suggested controller has precise tracking performance in presence of environmental disturbances.     

Direct evaluation of fault trees using object-oriented programmingtechniques

Object-oriented programming techniques are used in an algorithm for the direct evaluation of fault trees. The algorithm combines a simple bottom-up procedure for trees without repeated events with a top-down recursive procedure for trees with repeated events. The object-oriented approach results in a dynamic modularization of the tree at each step in the reduction process. The algorithm reduces the number of recursive calls required to solve trees with repeated events and calculates intermediate results as well as the solution of the top event. The intermediate results can be reused if part of the tree is modified. An example is presented in which the results of the algorithm implemented with conventional techniques are compared to those of the object-oriented approach     

Integrated MIMO fault detection and disturbance observer-based control

This paper presents a new method of disturbance observer-based control (DOBC) for multi-input-multi-output (MIMO) highly-coupled unstable systems. In contrast to the current input–output approach for stable single-input-single-output (SISO) systems, the Youla parameterization of stabilizing controllers by full order state observer (FOSO) feedback control is shown more appropriate for general MIMO systems, while retaining the intuitive aspects of DOBC design. We propose a general MIMO DOBC expanded from this single FOSO stabilizing control, where a parallel number of FOSOs for fault detection, state estimation, and disturbance observer are integrated to achieve the relevant operational requirements and performance. Within this integrated control system, we propose a MIMO disturbance observer design method by a game-theoretic detection filter (GTDF) design. The DOBC design features GTDF disturbance decoupling followed by H-infinity model matching to establish the desired bandwidth for each channel of the decoupled disturbance observer. The proposed DOBC is applied to an open-loop unstable MIMO Active Magnetic Bearing Spindle (AMBS). Experimental results are presented to demonstrate the design method and control performance.     

LTV controller design for vehicle lateral control under fault in rear sensors

This work focuses on vehicle lateral control for automated highway systems (AHSs) studied as a part of the California Partners for Advanced Transit and Highways (PATH) Program. In the PATH lateral control system, magnetometers are installed under both front and rear bumpers of the vehicle; these magnetometers measure the lateral deviation of the vehicle relative to the magnets buried along the centerline of each automated lane. Lateral controllers have been designed and tested successfully provided that there is no fault in magnetometers. It has been argued that these controllers are NOT tolerant to the fault in magnetometers. The focus of This work is the degraded-mode lateral control under fault in rear magnetometers. The aim of the controller design is to accomplish adequate performance with the remaining set of magnetometers, the front magnetometers. The effects of the fault are examined, and the significance of the linear time-varying (LTV) property of the front-magnetometer-based vehicle lateral dynamics is recognized. Popular control methods for LTV systems generally involve gain scheduling by switching between several linear time-invariant (LTI) controllers. Such methods are complicated and it is difficult to prove the stability of the switching mechanism. To derive a simple effective LTV controller, feedback linearization is applied to approximately cancel out the time-varying terms in the plant and to function as a gain scheduler. However, due to the weakly damped zeroes of the plant, feedback linearization with state feedback or matched observer state feedback results in weakly damped internal dynamics. In order to tune the internal dynamics, a mismatched observer is designed based on H-infinity optimal control techniques. Experimental results are presented to show the effectiveness of the controller design.     

Fault tolerant real time control system for steer-by-wire electro-hydraulic systems

A steer-by-wire (SBW) control system is presented with emphasis on safety issues. The applications are in articulated vehicles such as the wheel type loaders, articulated trucks, and others. The electro-hydraulic (EH) power circuit is controlled by two embedded electronic control modules (ECM), the primary ECM and backup ECM. The two ECMs monitor each others condition. If one detects fault in the other, it takes over the control functions. There are two main control algorithms that run in the ECMs in real-time: the steering valve control algorithm and the failure detection algorithm. The valve control algorithm basically generates command signal to the steering valve based on operator steering column signal as well as other machine condition sensors.The failure detection algorithm implements a fault detection logic for both input sensors and output drivers, and flags the corresponding warning for to the operator, and take a predefined action depending on the type of the failure detected. A unique fault strategy organization is implemented by inspecting the failure behavior on both the component and the system levels. The failure detection algorithm also determines the most likely “good” sensor signal from a set of redundant sensors for each critical measurement. Based on these good sensors data, the steering control algorithm sends two output signals: the control signal to the steering EH circuit valve and the control signal to the steering wheel force feedback device (i.e. a brake or a motor) to give operator feedback about the steering conditions.Finite state machine (FSM) concept is used to design the fault handling algorithms for both the component level and the system level failure. The probability of the system being at normal steering state or at any other steering failure state is determined. Failure mode probabilities of steering system components are also determined.     

Computer-assisted fault-tree construction using a knowledge-basedapproach

This paper presents a knowledge-based approach to analyzing fault trees of engineering systems. This approach can be used to build a fault tree from a graphical functional block diagram (using reduction for replicated events), to compute minimal cut sets, and to analyze the system for redesign suggestions. An implementation of this approach in a rule-based language is presented. The results are compared with manually prepared reliability reports on an electrical power system and an hydraulic system. The knowledge-based system outperforms the manual procedure in timeliness and accuracy     

Hybrid learning control schemes with input shaping of a flexible manipulator system

The paper describes a practical approach to investigate and develop a hybrid iterative learning control scheme with input shaping. An experimental flexible manipulator rig and corresponding simulation environment are used to demonstrate the effectiveness of the proposed control strategy. A collocated proportional-derivative (PD) controller utilizing hub-angle and hub-velocity feedback is developed for control of rigid-body motion of the system. This is then extended to incorporate iterative learning control with acceleration feedback and genetic algorithms (GAs) for optimization of the learning parameters and a feedforward controller based on input shaping techniques for control of vibration (flexible motion) of the system. The system performance with the controllers is presented and analysed in the time and frequency domains. The performance of the hybrid learning control scheme with input shaping is assessed in terms of input tracking and level of vibration reduction. The effectiveness of the control schemes in handling various payloads is also studied.     

Robust position control and disturbance rejection of an industrial plant emulator system using the feedforward-feedback control

An important class of electromechanical system known as the industrial plant emulator system which represents the many practical systems used in the industry. The motion control of the emulator system is challenging and important one as it mimics the system class of conveyors, machine tools, spindle drives, and automated assembly machines. In this paper, a new quantitative feedback-feedforward approach is proposed to address both tracking and the disturbance (measurable, uncertain) rejection problem. The proposed methodology is centered on the design of feedback controller with the inversion based feedforward control. The proposed method converts the problem on the uncertain system into a nominal sensitivity problem which is simple, less conservative and easier to solve for a large number of uncertain parameter system such as the emulator plant. The unknown dynamic of the disturbance (motor) is identified practically by a step response (three parameter model) for integrating system. The proposed feedforward/feedback control is experimentally demonstrated to meet the tracking and reject the disturbance with the less demand on the feedback control as compared to the existing methods under different loading condition.     

Feedback control with Posicast

An alternative way to use Posicast to damp oscillations in lightly damped control systems is proposed in this paper. Specifically, it is suggested that the Posicast technique be used within a feedback system, instead of the classical feedforward configuration. There are many types of Posicast, but discussion and analysis are focused here on the classical "half-cycle" Posicast form. Theoretical analysis and a design example are used to compare classical Posicast and the proposed feedback control method. An experimental result from a power converter application is also presented.     

Hybrid fault adaptive control of a wheeled mobile robot

A fault adaptive control methodology for mobile robots is presented. The robot is modeled as a continuous system with a supervisory controller. The physical processes of the robot are modeled using bond graphs, and this forms the basis of a combined qualitative reasoning and quantitative model-based estimation scheme for online fault detection and isolation during robot operation. A hierarchical-control accommodation framework is developed for the supervisory controller that determines a suitable control strategy to accommodate the isolated fault. It is shown that for small degradations in actuation effort, a robust controller achieves fault accommodation without significant loss of performance. However, for larger faults, the supervisor needs to switch among several controllers to maintain acceptable performance. The switching stability among a set of trajectory tracking controllers is presented. Simulation results verify the proposed fault adaptive control technique for a mobile robot.     

Multilayer control of an induction motor drive:A strategic step for automotive applications

Fault tolerance is a critical attribute in automotive electrical and propulsion systems. In this paper, a control scheme is presented that allows an induction motor drive system to operate in the event of multiple sensor failures. Automatic diagnosis of sensor fault and recovery is performed and used to reconfigure the drive system controls to achieve the best performance in lieu of component degradation. This approach couples a new digital delta-hysteresis regulation scheme with a model reference adaptive system scheme in order to provide fault tolerance for both phase-current and rotor position (speed) sensors. Simulation and experimental results are provided to show the effectiveness of the proposed scheme.     

Performance optimization of Cuk converters by sliding-mode control

A novel approach to the design of sliding-mode controllers for Cuk converters is presented, which is valid for both complete state feedback (fourth-order controller) and reduced state feedback (second-order controller). According to the proposed design criteria, both control techniques ensure excellent static and dynamic performances, also resulting in simple control implementation and minimum size of energy transfer capacitor. Experimental results are reported, and compared with those obtained with other popular control techniques