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In this article, we consider the time-varying trajectory tracking boundary control problem for the flexible rotation beam subject to distributed disturbance. A partial differential equation model for the flexible rotation beam system with the coupling of angle and vibration displacement is established by Hamilton principle. By introducing a servo system generated by the reference signal, a boundary controller is proposed to track the desired time-varying trajectory, which is different from the fixed angular position in most existing work. A Lyapunov-based stability analysis is presented to demonstrate that the tracking error system between the servo system and the original system is uniformly ultimately bounded. Based on the infinite dimensional operator theory, it is proved that the closed-loop system is well posed and all signals remain bounded. Numerical simulations verify the correctness of the theory and the effectiveness of the control strategy. And the experiments based on the Quanser platform demonstrate the same result as well. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive PID controller based on linear extended state observer (LESO) for the two-degree-of-freedom joint servomechanism of industrial robot with time-varying load, uncertainties of parameters and disturbance. The third-order extended state space equations of the system approximate model is established to obtain LESO which is applied to estimate the state values and the total disturbance. The model reference adaptive algorithm is used to estimate the variable moment of inertia to design the controller parameter for control law which is designed with disturbance compensation. By appropriately selecting the adaptive gain coefficient of model reference adaptive algorithm and the bandwidth of LESO, the influences of parameter uncertainty, unknown dynamics and disturbances are effectively attenuated. Simulation and experimental results show that the proposed method achieves both satisfactory disturbance rejection and tracking performances of the two-degree-of-freedom joint servomechanism. [ABSTRACT FROM AUTHOR]

Tuning rules for PID and PI-PI servo controllers are developed using a pole placement approach with a multiple pole, i.e. a triple one in the case of PID and a quadruple for PI-PI. The controllers involve complex roots in the numerators of the transfer functions. This is not possible in the classical P-PI structure which admits real roots only. The settling time of the servos determined by the multiple time constant is the only design parameter. Nomograms to read out discrete controller settings in terms of the time constant and control cycle are given. As compared to the classical structures, the upper limit on the control cycle is now twice longer in the case of PID, and four times in the case of PI-PI. This implies that the settling times can be shortened by the same ratios. Responses of a PLC-controlled servo confirm the validity of the design. [ABSTRACT FROM AUTHOR]

Summary: This study presents a novel digital control algorithm with state estimator technique for semi‐active control of structures with magneto‐rheological (MR) damper. The proposed control strategy is based on servomechanism (popularly known as command‐following or tracking system), where the measured output of a system pursues the command of reference input. This is achieved through a hybrid proportional–integral (PI) controller, different from the conventional output or state‐based feedback design, where the control force is proportional to the feedback of internal state (i.e., displacement and velocity) as well as the integral state (i.e., integral of output error signal) of the system. In this approach, optimal observer technique through Kalman filter is modified to estimate the full state and integral state vector of the system for feedback from the measured absolute acceleration output. Optimal gains of the proposed regulator (i.e., both proportional and integrator gains) and estimator are formulated by minimizing a desired performance index in discrete time. In addition, the present study proposes a direct algorithm, where the applied voltage to the MR damper varies continuously between the maximum and minimum range instead of being restricted to only maximum and minimum values. The adequacy of the proposed strategy is studied in terms of reduction in the following: (a) structural responses, (b) optimal control force, (c) sensor noise and process noise covariance of the filter output, and (d) applied voltage (as compared to clipped on–off case). Finally, it has been demonstrated that the proposed control algorithm provides superior performance and stability in comparison to the conventional proportional (state)‐based techniques. [ABSTRACT FROM AUTHOR]

One of the little described problems in hydrostatic drives is the fast changing runs in the hydraulic line of this drive affecting the nature of the formation and intensity of pressure pulsation and flow rate occurring in the drive. Pressure pulsation and flow rate are the cause of unstable operation of servos, delays in the control system and other harmful phenomena. The article presents a flow model in a hydrostatic drive line based on fluid continuity equations (mass conservation), maintaining the amount of Navier-Stokes motion in the direction of flow (x axis), energy conservation (liquid state). The movement of liquids in a hydrostatic line is described by partial differential equations of the hyperbolic type, so modeling takes into account the wave phenomena occurring in the line. The hydrostatic line was treated as a cross with two inputs and two outputs, characterized by a specific transmittance matrix. The product approximation was used to solve the wave equations. An example of the use of general equations is presented for the analysis of a miniaturized hydrostatic drive line fed from a constant pressure source and terminated by a servo mechanism. [ABSTRACT FROM AUTHOR]

This paper deals with the aspects of modeling, simulation and control of an automatic control system with hydrostatic transmission (HT). The aim of this research is to design the model of a system based on a specific conditions and requirements. Hydrostatic transmitters as a big power transmitters have a broad utilization as an executive device in systems of automatic control. The foundations for designing of those systems are dynamic analyses for HT and control of his elements. [ABSTRACT FROM AUTHOR]

A proper real-time system identification method is of great importance in order to acquire an analytical model that sufficiently represents the characteristics of the monitored system. While the use of different time-domain online identification techniques has been widely recognized as a powerful approach to system diagnostics, the frequency-domain identification techniques have primarily been considered for offline commissioning purposes. This paper addresses issues in the online frequency-domain identification of a mechanical system with varying dynamics; particular attention is paid to detect the changes in the system dynamics. A closed-loop online identification method is presented that is based on a sliding discrete Fourier transform at a selected set of frequencies. The method is experimentally validated by a closed-loop controlled servomechanism with a limited stroke and time-varying parameters. [ABSTRACT FROM PUBLISHER]

In this article is exposed the construction, design and testing of an alternative of a transhumeral electromechanical prosthesis, which aims to provide the patient with physical comfort and psychological satisfaction through a new functional prosthetic option. The main functions performed are activities symmetry as lifting objects with both hands and support activities. And whose operation is based on the replica of movement of the other contralateral upper extremity through deflection sensors and accelerometers, obtaining a parallel movement. [ABSTRACT FROM AUTHOR]

This study is about the electronic automation of the photoreflectance technique (PR), which consisted of the development of a digital electronic control for the spatial variation characterization of semiconductor materials. In this type of optical characterization, the interaction of radiation with the matter is achieved by directing two beams of light toward the sample, using arrays of mirrors and lenses, which require precise optical alignment. For this reason, a servomechanism for digital control of the positioning of the sample was added to the optical path , fixing the incident area of the light beams, allowing moving the sample in the XY coordinate system under study, obtaining 1.0 μm of resolution for both axes. The digital control of the position of these beams of light in the sample was achieved by embedding an electronic system based in AVR microcontroller, and a graphical user interface developed in LabVIEW software from the National Instruments. In the calibration of the measuring system, we used GaAs commercial single crystals, which are able to reproduce physical information reported in the literature for this material and therefore be able to contribute with this study to increasing the versatility of the PR technique. [ABSTRACT FROM AUTHOR]

This study is about the electronic automation of the photoreflectance technique (PR), which consisted of the development of a digital electronic control for the spatial variation characterization of semiconductor materials. In this type of optical characterization, the interaction of radiation with the matter is achieved by directing two beams of light toward the sample, using arrays of mirrors and lenses, which require precise optical alignment. For this reason, a servomechanism for digital control of the positioning of the sample was added to the optical path , fixing the incident area of the light beams, allowing moving the sample in the XY coordinate system under study, obtaining 1.0 μm of resolution for both axes. The digital control of the position of these beams of light in the sample was achieved by embedding an electronic system based in AVR microcontroller, and a graphical user interface developed in LabVIEW software from the National Instruments. In the calibration of the measuring system, we used GaAs commercial single crystals, which are able to reproduce physical information reported in the literature for this material and therefore be able to contribute with this study to increasing the versatility of the PR technique. [ABSTRACT FROM AUTHOR]

This paper studies the preview control problem for continuous-time control systems. A design method for an optimal preview controller is presented, when the desired tracking and disturbance are piecewise-continuously differentiable functions. Applying the same techniques as for optimal control in linear quadratic optimal control, we derive a type-one servomechanism with both desired tracking preview and disturbance preview compensation. A proof is presented that if the original system is stabilizable and detectable, the closed-loop system is asymptotically stable. We also design a full-dimensional state observer for the considered system. Finally, numerical simulations show the efficiency of the controller. [ABSTRACT FROM AUTHOR]

Abstract: This paper is concerned with modeling, analysis, and control of the cable-supporting system including actuator dynamics for the next generation large spherical radio telescope. According to its 50-m scaled model, to begin with, the dynamic formulations of the electromechanical coupling system including servomechanism dynamics and parabolic curve of the long-span cable sag effects are established; at the same time the relationship among cable force, cable end displacement and cable length variation is obtained by utilizing parabolic equation, and the dynamic modeling for control can be justified by the numerical example. In addition, taking account of the characteristics of nonlinearity, slow time-variant and multivariable coupling, a fuzzy control plus proportional-integral control method is utilized to control the wind-induced vibration of the cable-supporting system. Finally, simulation results from the 50-m scaled model control system, regarding the wind-induced vibration control of the cable-supporting structure in stationary position and the tracking control of the cable-supporting system, show the satisfactory performance of the proposed control scheme as compared with a discrete-time automatic disturbances rejection controller in the presence of internal model uncertainties in both the cable-supporting mechanism and servomechanism dynamics and external disturbances. [Copyright &y& Elsevier]

This paper focuses on the adaptive robust control (ARC) for servomechanisms whose dynamic models are subject to unknown parameters, disturbance, and parameter sudden changes. To improve the control performance of the traditional ARC, a novel identifier-based ARC (IFARC) scheme is proposed. In this scheme, an identifier is utilized to accelerate the parameter tuning process and to heighten the accuracy of parameter estimation. A switching logic component based on a given performance index is introduced to select the better parameter estimate vector from those provided by the identifier and the adaptation law. As a result, transient performance can be improved according to the certainty equivalence principle. In addition, the exact reconstruction of the unknown parameters and exponential decay of the tracking error can be achieved under certain conditions. The stability and performance of IFARC are theoretically analyzed. Finally, simulation results show that the IFARC can achieve favorable tracking performance. [ABSTRACT FROM AUTHOR]

Abstract: This paper considers the problem of asymptotic trajectory tracking and/or disturbance rejection for linear time-varying systems via input/output representation. Inspired by the structure of repetitive control, a novel feedback mechanism is proposed based on which the necessary and sufficient condition for the problem is derived. This condition is a generalization to the time-varying case of the result in time-invariant setting. Based on the complete knowledge of the plant model, a design is provided and it is applicable to repetitive control for time-varying plants. An important feature of the proposed approach is that a systematic way of constructing time-varying internal model unit is provided. [Copyright &y& Elsevier]

Abstract: This paper presents an integrated design approach for variable input-speed servo four-bar linkages. In order to satisfy the kinematic requirements, to reduce the shaking force and moment, to improve the speed trajectory tracking performance and to minimize the motor power dissipation, the dimensions of the links, the counterweights, the input-speed trajectory and the controller parameters are considered as the design variables simultaneously. The proposed integrated design approach is introduced and formulated with the optimization design problem. Examples are given to compare the results of the proposed design approach with the other two approaches and demonstrate the feasibility of the proposed integrated design approach. [Copyright &y& Elsevier]

Abstract: Friction degrades the positioning accuracy of servomechanisms. Friction compensators are required to fabricate high-performance servomechanisms. In order to compensate for the friction in the servomechanism accurately, identification of the friction is required first. This paper proposes a friction identification method of a ball-screw driven servomechanism in the frequency domain. A nonlinear friction model including static, Coulomb, and viscous friction as well as Stribeck effect is formulated by using describing functions. Friction elements are estimated through the limit cycle analysis in a velocity control loop. In order to increase the accuracy of the friction identification process, a Butterworth filter is incorporated into the velocity feedback loop. Validity of the proposed method is confirmed through the numerical simulation and experiment in a ball-screw driven servomechanism. In addition, a model-based friction compensator is applied as a feedforward controller to compensate for the nonlinear characteristics of the servomechanism and to verify the effectiveness of the proposed identification method. [Copyright &y& Elsevier]

The term "data recovery" herein refers to accessing logically and/or physically damaged storage media, for which no functioning backup exists. The state-of-the-art physical techniques for recovering data from failed hardware can all be described as "part replacement." To achieve high data density and high manufacturing yields, modern drives are "hyper-tuned" in the factory so that their data layout, zone frequencies, and various channel settings are optimized for each head, surface, and zone. This greatly complicates part replacement because a transplanted headstack, for example, no longer matches the servo, preamp, and read channel parameters that were optimized for the original headstack. Methods and challenges are discussed for replacing, or "refreshing," firmware and system area information and for replacing all of the drive's electronics. The data recovery industry's point of view, limitations of current techniques, and some probable future directions in data recovery are also presented. It is predicted that data recovery will be more important in the future as drives are exposed to more extreme mobile environments. Drive manufacturers may be able to differentiate themselves from their competition by designing for recoverability. [ABSTRACT FROM AUTHOR]

A servocompensator with performance of frequency following is applied to a tracking control system whose reference signal includes sinusoidal components. The applied servocompensator is characterized by using signals synchronized with the reference signal in calculating the control input by means of convolution integral. Since the transmission zeros of the closed-loop system are generated at the same locations as the unstable poles of the reference signal automatically, the pole-zero cancellation necessary for asymptotic regulation is achieved. To demonstrate the efficacy of the servocompensator, an experimental apparatus is developed in which the position of a pick up is controlled to hold the distance between the pick up and a rotating disk. In such systems, the misalignment of the disk causes the reference signal to include sinusoidal components. The control error was remarkably reduced at any rotational speed by the servocompensator. [Copyright &y& Elsevier]

The mechanism of topographic mapping of retinal ganglion cells to the midbrain was previously elucidated by the servomechanism model, which is based on the fact that cells expressing Eph-receptors respond specifically to surface expressing membrane-bound ephrin-ligands at a critical level. The retina has increased nasal-to-temporal gradient of Eph receptor-density, and the optic tectum/superior colliculus has increased rostral-to-caudal gradient of membrane-bound ephrin-ligand. An axon from the retina has an identification tag of a certain level of Eph-receptor density depending on its retinal position, and adheres to the site on the tectum/superior colliculus expressing ephrin-ligands at a critical ligand-density level. The servomechanism model rigidly defines positions of axon terminals on the midbrain. However, optic nerve regeneration experiments combined with halved retina or tectum show a plastic or flexible mapping (expansion, compression and transposition of tectal projections). To reconcile the discrepancy between the rigid model and the plastic behavior, competition between retinal axon terminals for a target site was introduced to the servomechanism. The servomechanism/competition model succeeded in computer simulations of the plastic mapping of retinal axons on the tectum. Recent experiments of upregulated ligand-density on the tectum during nerve regeneration and the role of axonal competition are discussed. [ABSTRACT FROM AUTHOR]

A direct procedure is proposed for identifying the joint parameters in a linear servomechanism with multiple joints. The linear dynamical equations of a mechanical system with gains from feedback sensors are derived. The Bode graphs are used to compare the experimental and analytical models to identify the stiffness and damping coefficients. Sensitivity techniques are applied to reduce the discrepancies in the frequency responses of the output in analytical and experimental models. The joint parameters are then identified. An industrial servomechanism with multiple joints, in which a payload is driven by a mechanism that consists of a motor, a ball screw, gears, linkages, and a feedback sensor, is used to demonstrate the utility of the proposed procedure. The values of five stiffness and six damping parameters for the joints of this servomechanism were identified successfully by this procedure. The identified joint parameters were also verified in a different operating condition of the servomechanism. [ABSTRACT FROM AUTHOR]

The global robust servomechanism problem (alternatively, global robust output regulation problem) for lower triangular systems has been studied for two special cases. The first case assumes that the systems only contain polynomial nonlinearities, and the second case limits the exogenous signals and the unknown parameters to be within a known bounded set. This paper presents the solvability conditions of the global robust servomechanism problem for the lower triangular systems for the most general case where neither of the above two assumptions is needed. Our approach consists of two steps. In the first step, we convert the problem into a global adaptive regulation problem for lower triangular systems subject to both dynamic and static uncertainties. In the second step, we derive the solvability conditions of the problem by appealing to the recent result on the solvability of the global adaptive regulation problem for lower triangular systems with both dynamic and static uncertainties. [Copyright &y& Elsevier]

This paper describes classical system identification and control design techniques for the dual actuated servomechanism of a hard disk drive. The dual actuated servomechanism consists of a electromechanical coarse actuator and a piezo-electric micro-actuator. The coarse actuator provides the motion required to move the read–write head from one data track to another, while the micro-actuator improves the tracking performance of the servoloop. The micro-actuator also reduces the response time for small seek-length. A simple design approach is adopted in this paper. The coarse actuator loop is first designed for basic performance and stability, using estimated state feedback. The compensator for the micro-actuator is then designed to achieve better performance of the overall system. Simulation and experimental results underscore the effectiveness of the design. [Copyright &y& Elsevier]

Topographic mapping of retinal ganglion axons to the midbrain is computed by the servomechanism model, which is based on the experimental result of cell attachment. Cells expressing a certain level of Eph proteins (receptors for ephrin ligands) optimally attach to a surface that expresses a specific level of ephrin ligand density. The retina has an increasing nasal-to-temporal gradient of Eph receptor density, and the optic tectum/superior colliculus has an increasing rostral-to-caudal gradient of membrane-bound ephrin ligand. An axon from the retina has an identification tag of a certain level of Eph receptor density depending on its retinal position and adheres to the site on the tectum/superior colliculus expressing ephrin ligands at a critical ligand density level. Quantitatively, a retinal axon has a receptor density (R) that is determined by its retinal position, and the axon terminal is induced to adhere to the tectal site of ligand density (L = S/R), where S is a constant. Consequently, the servomechanism model defines positions of axon terminals on the midbrain, Abnormal topographic maps are reported in a knock-in experiment with elevated density of Eph receptors and a knock-out experiment lacking ephrin ligands using gene-targeting technology. By adding competition between axon terminals for target sites to the servomechanism model, the abnormal maps became easy to understand. Furthermore, the servomechanism-competition model allowed conjecture of the gradient shapes of receptor and ligand densities and estimation of the capacity of the midbrain surface to accept retinal axon terminals. [ABSTRACT FROM AUTHOR]

In this paper, we present a two-degree-of-freedom controller tuning for two-mass-spring systems with friction based on the iterative feedback tuning (IFT) approach. While two-mass-spring systems are widely used as fundamental components of the mechanical servo systems, they have sometimes severe friction. In order to cope with such cases, we adopt two strategies. One is the separate tuning of feedback and feedforward controllers. In particular, the feedback controller is tuned to achieve low sensitivity rather than tracking. The other is to introduce a quasi-Newton method into a parameter renewal law. The effectiveness of the proposed method is demonstrated through numerical simulations. Furthermore, we evaluate its effectiveness by experiments. [Copyright &y& Elsevier]

A two degree-of-freedom microprocessor based controller that uses the principle of Extended Physiological Proprioception (EPP), was designed for the simultaneous multifunctional control of upper-limb prostheses. In an EPP system, the output is related to the input by a mechanically ``unbeatable'' position servomechanism. Use of embedded microprocessor systems in the control of upper-limb prostheses provides a high degree of control algorithm flexibility allowing different control algorithms to be downloaded and executed in the same controller circuit. In addition, control parameters can be easily adjusted and tailored to different user capabilities. In a trans-humeral or shoulder disarticulation prosthesis we envision this controller enabling EPP control of both elbow flexion-extension, and humeral rotation. In a wrist disarticulation or trans-radial prosthesis this controller, in conjunction with other similar controllers, could provide EPP control of individual digits in a multifunctional hand prosthesis. [ABSTRACT FROM AUTHOR]

For electro-discharge machining (EDM), only when in the optimum state can the highest material removal rate be realized. In the practical machining process, the timely elevation of the tool electrode, which ordinarily occupies quite a lot of time, is needed to eliminate chipping. In this paper, an adaptive fuzzy control system of a servomechanism for EDM combined with ultrasonic vibration is studied. This control system can adjust the discharge pulse parameters in a timely manner, and also the gap between the tool electrode and the workpiece material, therefore, the machining state can be optimal, by which the EDM combined with ultrasonic vibration is improved and the machining efficiency is increased. In addition, a stimulation program is designed by means of Microsoft Visual Basic software. [Copyright &y& Elsevier]

• Research highlights a new theorem of multistage operated cascaded intelligent fault protection scheme. • Research highlights an intelligent relaying algorithm for controlling multiple connected load. • Research highlights an idea of how the output from the stage - II will be fed to the CR type isolator just after enduring the defuzzification process. Designing an instrument protection system has been considered as one of the most challenging domains in the power system. Intelligent tripping mechanism has been introduced in few sectors for controlling the moving contacts of a single operating relay connected to an electrical system. In this work, we have developed a cascaded relaying for a priority based decision making fuzzy inference system with fault tripping mechanism for controlling multiple operating relays. To obtain this priority based design of intelligent relaying, a multistage cascaded relaying is considered for achieving the higher accuracy. In this paper, we have discussed regarding the simulation of a load priority based tripping mechanism incorporated intelligent relaying. The differential equation achieved from the stage - I relaying simulation model of measurement blocks and fault generator blocks have been discussed. We have validated the stage - I relaying of the entire concept of the design with the mathematical modeling and also the simulation results of the stage - II output. The proposed method utilizes the concept of two stage relaying by introducing a Fuzzy Inference System designed to control the isolator state for the particular multistage based cascaded intelligent fault protection scheme. [ABSTRACT FROM AUTHOR]