Search

For traditional direct drive volume control electro-hydraulic servo system, the servo motors rotary inertia is limited strictly, the speed of response is slow and the actuators reciprocating motion characteristics are not consistent. In order to solve these problems, this paper designs a kind of high power direct drive differential volume control electro-hydraulic servo system. It is instructive for design of hydraulic system which demands high output power, changes direction of motion frequently, needs high response frequency and requires the speed of reciprocating motion keep consistent.

A control method for position servo control of Transverse flux machine (TFM) by controlling armature current Root-Mean-Square (RMS) and initial phase is proposed in this paper. Specifically, the voltage balance equation of TFM is provided, and the phasor diagrams are analyzed to achieve the expression of electromagnetic power of TFM. The expression indicates that the electromagnetic torque is determined by armature current RMS and the initial phase. A position servo control system of TFM is established based on the expression. The results of the position servo control curves show that the position servo control system of TFM is effective.

The error of gain of servo control system transfer function is larger by the method of frequency measurement, In this paper, By appying voltage on the both ends of the motor, measure DC response of system to tmeasure the DC gain of control object.Experimental results show that the gain accuracy by the measurement method increases 2.5 times than the traditional measurement.

Most current researches working on improving stiffness focus on the application of control theories. But controller in closed-loop hydraulic control system takes effect only after the controlled position is deviated, so the control action is lagged. Thus dynamic performance against force disturbance and dynamic load stiffness can’t be improved evidently by advanced control algorithms. In this paper, the elementary principle of maintaining piston position unchanged under sudden external force load change by charging additional oil is analyzed. On this basis, the conception of raising dynamic stiffness of electro hydraulic position servo system by flow feedforward compensation is put forward. And a scheme using double servo valves to realize flow feedforward compensation is presented, in which another fast response servo valve is added to the regular electro hydraulic servo system and specially utilized to compensate the compressed oil volume caused by load impact in time. The two valves are arranged in parallel to control the cylinder jointly. Furthermore, the model of flow compensation is derived, by which the product of the amplitude and width of the valve’s pulse command signal can be calculated. And determination rules of the amplitude and width of pulse signal are concluded by analysis and simulations. Using the proposed scheme, simulations and experiments at different positions with different force changes are conducted. The simulation and experimental results show that the system dynamic performance against load force impact is largely improved with decreased maximal dynamic position deviation and shortened settling time. That is, system dynamic load stiffness is evidently raised. This paper proposes a new method which can effectively improve the dynamic stiffness of electro-hydraulic servo systems.

A speed control servo system based on STM32 is designed in order to realize the rapid, accurate, smooth speed control of rotary table. the system uses embedded microprocessor STM32F103 as the core, using the absolute encoder as the position sensor.The system achieved control of motor speed by PWM (pulse width modulation).Speed and current double loops control is used,and the expert PID control is used as the control algorithm. Through the analysis of the experimental results can be seen that the system has good stability, and the static and dynamic indicators meet the design accuracy.This design basically has reached the requirement of the servo motor speed control system.

in this paper, a very low cost two-axis position servo system is developed. This system is controlled by DSP. We study the stability of the position servo control system. We use the PI control algorithm in our application. We achieved twice switching frequency by using PWM signals to share the switching dissipation ePWM module of the DSP. A numerical consideration is given. The simulation results demonstrate the stability of the proposed method.

With the growth of hard disk storage, it would be difficult to meet the specification of the high track density with conventional single actuator. Therefore the next generation of high speed hard disk drive uses the concept of dual-stage actuated hard disk drive where a secondary actuator is mounted onto the VCM actuator. This helps to achieve higher servo bandwidth and, therefore, more precise tracking. Improved tracking error allows higher track density and hence higher storage capacity. Piezoelectric actuator has been a popular choice as the secondary stage. However, the piezoelectric actuators exhibit an unavoidablecharacteristic of hysteresis which causes inaccuracies and oscillations in the system responses.In this paper, the hysteresis behaviour is investigated for asuspension based PZT actuator which is used as the secondary actuator of HDD available in the market. The Generalized Prandtl-Ishlinskii (GPI) hysteresis model which is a phenomenological based model is obtained usingnon-linear least square curve-fitting. In the secondexperiment, a second order linear dynamics model of the PZT actuator is obtained using frequency response identificationmethod. High frequency resonance modes of the PZT actuator are eliminated using a notch filter. By integrating the obtained GPI hysteresis model with this second-order lineardynamics, a nonlinear dynamic model and an inverse feedforward controller are developed.Preliminary simulation results demonstrate that inverse feedforward controller can be appliedfor precise tracking of triangular and multiple frequency sinusoidal trajectories.

directional antenna is widely used in the measurement and control for Short range UAV because of its high gain in the range of beam angle, the speed of UAV is very fast, so the requirements for speed and acceleration of directional antenna is very high, step motors are usually in the traditional directional antenna systems, which works in the open loop and has low positioning accuracy, slow speed response and dynamic regulation, In order to meet the requirements of the directional antenna servo system, the design of servo control system for Azimuth of directional antenna based on PMSM and CAN bus communication is introduced in this paper . The test results indicate that the dynamic response of antenna servo system is very quick and tracking accuracy is very high. which can be well applied in the target tracking system.

This work proposes a novel strategy for middle frequency resonance detection and reduction for the speed control of industrial servo systems. The report includes an analysis of the drawbacks of the traditional resonance reduction method based on an adaptive notch filter in the middle frequency range, and the main drawback is summarized as the difference between the resonance frequency and the oscillation frequency. In the proposed method, a self-tuning low-pass filter with a corner frequency determined using FFT results and several self-tuning rules is introduced in the speed feedback path. Consequently, the effective range of the adaptive filter is extended across the middle frequency range. The simulation and experimental results show that the frequency detection is accurate, and the resonances are successfully reduced during steady-state and dynamic speeds.

This paper presents a strategy and approach to reduce the position error signal induced by arm bending mode, which is called arm-bending off-track in high density magnetic disk drives. In order to increase the data storage capacity of a hard disk drive (HDD), the track pitch keeps decreasing. This narrow pitch and its position error margin make the accuracy on track more challenging to meet the track misregistration (TMR) budget. To meet the requirements of hard disk drives, the mechanical component should be improved considering it. Among the enablers to meet the drive requirement, this paper is focused on a strategy to reduce the off-track due to arm bending under dual stage actuator system. Off-track due to arm bending mode becomes newly important parameter related to TMR with high density drives. The position error caused by the vertical motion owing to arm bending resonance, which can be neglected enough in the larger track pitch of old day, becomes a bottle neck of the TMR budget. Proposed arm design is introduced to reduce the arm-bending off-track by allowing the head to move in such as way that will compensated the off-track caused by arm bending mode. And, optimal bending frequency location under dual stage actuator can maximize the attenuate the off-track due to arm bending. Dual stage actuator is introduced for increasing the servo bandwidth. The dual stage actuator can extend the servo bandwidth using the additional fine actuator, which is located on suspension loadbeam or gimbal. And, there is also a special servo algorithm and its error sensitivity curve. In this paper, the optimal solution for reducing arm-bending off-track is proposed under dual stage actuator system is studied.

This work presents a new approach to high performance velocity servo system design. The approach is based on a discrete-time sliding mode (DSM) control with disturbance compensation. For the purpose of design, the controlled plant is approximated by first-order model. The traditional, as well as the integral type of DSM control is considered. The disturbance compensator is based on the fact that the matched disturbances are directly reflected in the previous value of the switching function. In this paper, slow varying disturbances are estimated by a parallel connection of first- and second-order estimators. The integral type of DSM velocity servo system with such combined compensator can track references and significantly reject bounded disturbances, both up to cubic parabola type. The proposed control system is chattering-free. Theoretically obtained results are verified by simulations and experiments.

The position error signal (PES) in current hard disk drives is generated from the embedded servo data and used as the input for the track following controller. The servo pattern design and the decoding are both quite complicated in terms of the servo writing and servo detection, but they are important for the system dynamics study and track following controller design. In this paper, a novel scheme based on discrete fourier transformation (DFT) to decode the servo signal from a special magnetic servo pattern and generate the PES is proposed. In the scheme adjacent magnetic tracks with different frequencies are recorded to the disk and used as servo tracks to encode the position information. Simulation results show that the amplitudes at the two writing frequencies in the readback spectrum depend on the magnetic head position. The quadrature PES defined by the difference of the amplitudes is almost linear between the two adjacent tracks The simulation and off-line experimental results analysis agree with each other and prove the feasibility of this scheme. A real-time signal acquiring and processing system with a commercial field programmable gate array (FPGA) and ADC/DAC chips was built, and the proposed scheme was implemented in the FPGA to do the high-speed signal analysis. The magnetic head position information is extracted from the readback spectrum in the FPGA and transferred to a PC host for real-time graphic display using a labview interface. The system demonstrates an ability to generate the PES at 25 K samples per second with a resolution around 3 nm. The sampling rate can be enhanced further to 125 kHz if more servo sectors are written to the disk. This system provides a re-configurable research stage for studying the dynamic behavior of hard disk drives and for developing the control algorithm for track following.

This paper presents a control design methodology for high-precision positioning. In particular, the compensation for the effects of vibration modes and nonlinear friction on the positioning performance is taken into account in this methodology. In the controller design, the servo bandwidth of the feedback control loop should be expanded to compensate for nonlinear friction, while robust stability with respect to frequency variations in the vibration modes should be ensured. In this study, therefore, strain feedback for vibration modes is adopted to provide robustness with respect to frequency variations and to improve the disturbance suppression performance by expanding the bandwidth of a disturbance observer. This strain feedback is based on the use of a piezoelectric element. The efficiency of the proposed positioning control approach has been verified by conducting experiments using a prototype for industrial table drive systems. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(3): 46–55, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21306

An integral part of modern servo drive is a position measuring system. This article is focused on processing of resolvers and capacitive sensors signals, whose quadrature output signals are the modulated in double-sideband amplitude modulation. Well known, the disadvantage of the amplitude modulation is low noise immunity. One of the sources of the noise is switching of power transistors of inverter. This noise can leads to reduction of position feedback resolution and bandwidth. The article presents the high resolution and high bandwidth signal processing algorithm. The proposed algorithm suggests the choice of the sensor excitation frequency, based on the analyze of the noise spectrum of the inverter pulse-width modulation frequency, and includes fast synchronous demodulation and adaptive observer-based converter to estimate the feedback position. The proposed demodulation method allows sampling and demodulating of sensor signals with frequency limited only by conversion and processing time of analog-to-digital converter. The adaptive observer-based digital part of measuring system compensates the phase lag of demodulated signals and increases position feedback resolution for a given system dynamics. The proposed method was implemented in the planar servo drive with the capacitive position measuring system. The result demonstrates the 15 bit resolution into 640 цm signal period and 1 kHz bandwidth of position feedback with excitation frequency of 12 kHz.

Archival demands for digital tape storage systems require smaller spacing between data tracks on the magnetic tape to allow for more data storage on a single cartridge. Increasing track density while maintaining track following provides a challenge for the servo control of the tape drive. In particular, interchangeable tape cartridges and time-varying tape reel diameters during operation cause variable disturbances during servo control. In this paper we show how a tape servo control algorithm can be regulated to handle changes in disturbance dynamics during servo operation of the tape drive. The approach is based on adaptive regulation by exploiting a Youla-Kucera parameterization of the servo controller and an explicit minimization of the Position Error Signal (PES) during servo operation in real-time. Theoretical results on the stability of the feedback system and real-time application results on an Linear Tape-Open (LTO) drive are included in the paper. The result show a significant reduction of the variance of the PES over different tape cartridges and a constant PES variance during a complete reel-in operation of the tape drive.

In this paper, an adaptive piecewise linear control scheme is proposed for improving the performance and response time of servo mechanical control systems. It is a gain stabilized control technique. No large phase lead compensations or pole zero cancellations are needed for performance improvement. Large gain is used for large tracking error to get fast response. Small gain is used between large and small tracking error for good performance. Large gain is used again for small tracking error to cope with disturbance. It gives an almost command independent response. It can speed up the rise time while keeping robustness unchanged. The proposed control scheme is applied to a servo system with large time lag and a complicated electro-hydraulic velocity/position servo system. Time responses show that the proposed method gives significant improvements for response time and performance.

We present an approach to locking of optical cavities with piezoelectric actuated mirrors based on a simple and effective mechanical decoupling of the mirror and actuator from the surrounding mount. Using simple elastic materials (e.g. rubber or soft silicone gel pads) as mechanical dampers between the piezo-mirror compound and the surrounding mount, a firm and stable mounting of a relatively large mirror (8mm diameter) can be maintained that is isolated from external mechanical resonances, and is limited only by the internal piezo-mirror resonance of > 330 KHz. Our piezo lock showed positive servo gain up to 208 KHz, and a temporal response to a step interference within < 3 μs.

Small size ultra-precision Computer Numerical Control (CNC) machines require high dynamic performance. Flexible frame phenomena can limit the machine dynamic performance, particularly in small size machines. A novel accelerometer based feedback concept for improving machine dynamic performance was developed and realised, a virtual metrology frame. It expends the limited techniques for improving dynamic performance of a small size machine by measuring the flexible frame displacement, and feeding it into the controller. The concept was implemented in a simplified linear motion system, and showed a 12dB reduction in the magnitude of the first resonance in the plant frequency response function. This allowed improving the servo bandwidth by 58% based on a PID controller. A new technique for real-time dynamic displacement measurements using accelerometer was developed. It shows a low sensor noise σ

The piezoelectric actuator technology for moving the read-write head of Hard Disk Drive (HDD) is very important and widely used. Advanced high-performance technologies for the actuator and servo control are required in order to achieve not only accurate positioning control on data tracks but also high-speed access onto another data track. There is strong demand for hard disk drives with high-speed access performance, which generally requires actuators with a wider servo bandwidth. This paper focuses on the comparative piezoelectric materials based unimorph actuators with classical piezo (Poly crystalline PZT) and newer piezo (Single-crystalline PMN-PT) ceramics. The advantages of piezoelectric materials in terms of mechanical and electrical characteristics aiming at a useful compromise performance displacement and resonant frequency are studied and analyzed.

International audience; Towards an optical synthesis of low phase noise continuous millimeter and submillimeter electrical waves in a compact and an all-fiber system, we present the all-electrical locking of the optical frequency of a distributed feedback laser (DFB) diode at 1549 nm tunable over 4 nm, on a fibered Fabry-Perot cavity. We demonstrate a 6 MHz servo bandwidth and a frequency noise suppression down to 0.3 Hzhillz at 80 kHz carrier offset frequency in the error signal. Furthermore, we use a Brillouin fiber laser in order to refine the stabilized laser linewidth and we then demonstrate a frequency noise suppression down to 0.4 Hzhillz at 100 kHz offset frequency, limited by the phase noise floor of the measurement instrument.

The main theme of this paper is to propose fast on-line optimal bandwidth search and controller tuning techniques for servo motor drives. The proposed controller tuning method derives the controller gains by searching the optimal bandwidth and identifying the inertia. The optimal bandwidth can be achieved before oscillation occurs. It will be shown the gains of speed controller of servo drives are tuned automatically to reflect the variation of load inertia. Experimental results derived from DSP-controlled PMSM servo drives will be shown. The results demonstrate on-line optimal bandwidth and auto gain tuning can be achieved without motor and load information in prior. These results fully support the developed techniques and claims.

According to loading speed, high precision and strong stability, we design the force servo controller based on STM32 processor. During the motion process, the force servo controller can timely and accurately eliminate the excess torque, using CAN bus communication for data exchange with the host computer, precisely measuring the force in real time by the force sensor and calculating model force in real time by location feedback. Meanwhile, to solve the problem of load-induced movement caused by the mechanical structure of the control loading system, we designed a kind of decoupling control algorithm to eliminate induced movement. Experimental results show that the tracking accuracy of the system error is less than 15%, the step characteristics of the system response time less than 0.1s, and the feel of pilots for induce motion in the control loading system meet the design requirements.

The complex mechanical system with dedicated servo have servo bursts continuously stored in between data recording layer and the SUL of conventional PMR (perpendicular magnetic recording) media. It thus provides high sampling rate for servo control loop implementation. Its servo performance is investigated by imposing an external vibration in 0–500Hz, and its advantageous over conventional servo systems is verified. Dual-stage actuation mechanism is applied to enhance servo performance, making use of the high servo sampling rate. Extremely high servo bandwidth is then achieved with sufficient PES samples provided by the dedicated servo. In addition to 0–500Hz vibration, the high bandwidth servo loop is able to significantly attenuate the audio vibration which is dominant in 1k-5kHz. Testing and simulation results are provided in this paper to demonstrate the performance of the dedicated servo recording systems.

This paper presents a new method of digital feedback processing of sine-cosine position sensor. The processing algorithm is structured as an observer-based tracking loop with adaptive bandwidth. The adaptation provides noise attenuation as well as low lag between the actual and observed position. The method was implemented in a digital signal processor for feedback processing of planar servo drive capacitive position measuring system. The experiment results demonstrated the sub-micron positioning resolution of planar servo drive.

In order to calculate the servo position error signal (PES) in the servo system, it is necessary to make high precision sampling and FFT calculation for the burst signal. Most designer s adopt 8bits ADC converter in the read write channel servo system of hard drive controller chip 88i6310 to cost down, and both servo system and signal system share the sampling circuit. Because of the quantitative noise disturbing during the sampling process, it is not enough to use 6bits ADC converter for the serve burst signal, and significant error exist for t he burst signal with the FFT calculation. This paper analyzed the existing servo over-sampling model via quantitative error model firstly, and provided the enhanced servo system sampling model. The simulation shows that, the enhanced solution reduces the average quantitative error from 0. 38 LSB to 0.14LSB, and improves the resolution of ADC converter from 9.5 bits to 10.8 bits.

Electro-hydraulic servo shaking table usually requires good control performance for acceleration replication. The poles of the electro-hydraulic servo shaking table are placed by three-variable control method using pole placement theory. The system frequency band is thus extended and the system stability is also enhanced. The phase delay and amplitude attenuation phenomenon occurs in electro-hydraulic servo shaking table corresponding to an acceleration sinusoidal input. The method for phase delay and amplitude attenuation elimination based on LMS adaptive filtering algorithm is proposed here. The task is accomplished by adjusting the weights using LMS adaptive filtering algorithm when there exits phase delay and amplitude attenuation between the input and its corresponding acceleration response. The reference input is weighted in such a way that it makes the system output track the input efficiently. The weighted input signal is inputted to the control system such that the output phase delay and amplitud...

Because of such merits of servo turret like fast speed of tool changing, high accuracy of first location, simple mechanical structure, high reliability and so on, servo turrets are widely used in turning processing and turning and milling complex processing center.Control mode of servo motor speed is one of the critical problems in the designing of servo turret.S curve acceleration and deceleration control is to make the derivative of acceleration as constant in this procession, and maximize to reduce the impact of mechanical system by controlling acceleration derivative. Otherwise, by setting parameter or programming acceleration and its derivative, flexible acceleration and deceleration will be controlled to fit for different kinds of situation of machines.

Design and implementation of servo controller for a hydraulic servo system with a load of large inertia, low stiffness and multi-stage resonance is considered. To achieve a set of desired requirements, this paper is divided into three parts of work. First, notch filters and peak filters extracted from the general phase stabilized controller are applied in order to restrain the resonance peak of the load. Second, a disturbance observer in the feedback path is used for rejecting low-frequency disturbance and high-frequency noises. Third, as the complete inversion of the closed-loop dynamics at the whole frequency band does not necessarily give the best performance, low-pass filter, proportional derivative (PD) compensation, and lead correction are adopted in the feedforward path. The work proposed here overcomes the challenge of improving amplitude margin and phase margin while eliminating resonance simultaneously. The effectiveness of the combined control is investigated through simulation and experiment results, which show that the control strategies raised here successfully complete resonance rejection and also give ideal performances that meet the indices.

Dual-servo systems (DSSs) are highly desirable in micro-/nanomanipulation when high positioning accuracy, long stroke motion, and high servo bandwidth are required simultaneously. This paper presents the design and development of a new flexure-based dual-stage nanopositioning system. A coarse voice coil motor (VCM) and a fine piezoelectric stack actuator (PSA) are adopted to provide long stroke and quick response, respectively. A new decoupling design is carried out to minimize the interference behavior between the coarse and fine stages by taking into account actuation schemes as well as guiding mechanism implementations. Both analytical results and finite-element model (FEM) results show that the system is capable of over 10 mm traveling, while possessing a compact structure. To verify the decoupling property, a single-input-single-output (SISO) control scheme is realized on a prototype to demonstrate the performance of the DSS without considering the interference behavior. Experimental results not only confirm the superiority of the dual-servo stage over the standalone coarse stage but reveal the effectiveness of the proposed idea of decoupling design.

In a tape drive, the head assembly hosting servo readers and data writers/readers must initially be moved to a target position, so that information can be written to or read from the desired tracks. In tape systems with flangeless rollers, as recently introduced in IBM’s tape drives for improved performance and extended drive and tape lifetime, the initial positioning of the servo readers over the servo bands, from which the position-error signal for steady-state track-following operation is obtained, has to be fast. This requirement is dictated by the nonnegligible lateral tape motion experienced in tape paths with flangeless rollers. In this paper, a method is proposed to utilize both the servo readers and the data readers in a drive to detect the presence of a valid servo signal. If the servo readers are not positioned over a servo band, the distance between servo readers and servo band can thereby be continuously estimated by identifying the data reader detecting the presence of a servo signal. This information is then provided to a control element that controls the joint operation of a coarse stepper motor and a voice-coil motor based fine actuator with large stroke in a feedback or feed-forward configuration to achieve fast servo reader positioning. In the feedback-based approach, all data channels are continuously monitored to detect the presence of a valid servo signal and a pseudo position-error signal is generated and fed back to the control unit to drive the actuator towards the target position. In the feed-forward approach, a trajectory for the actuator is determined as soon as the servo band is in the capture range of the fine actuator and a control signal is generated so that the servo reader rapidly lands over the servo band with optimum control effort.

Motion synchronization of servo systems carries great importance in various precision manufacturing operations. For double-sided (duplex) milling of thin plates, in particular, the cutting tools must engage with both sides of workpiece in a precisely synchronized manner to avoid forced vibrations. A continuous sliding mode controller (SMC) is developed to deal with the problem of position synchronization for dual spindle servo systems. Synchronization error is defined as the differential position error between the two servo systems that follow same reference motion command. Hence, the developed continuous SMC penalizes 3 error states; namely the individual servo positioning errors, and the synchronization error between them. As a result, individual trajectory tracking as well as motion coupling objective is introduced. The final control law is implemented in the form of a PID controller in real time, and double-sided milling experiments are performed to verify its effectiveness.

An acceleration Feedback(AFB) is introduced to the servo system to improve the dynamic performance of a moving base optoelectronic stability platform.As it is difficult to establish a model for the moving base optoelectronic platform according to a moving object,the proposed acceleration feedback is realized by measuring angle acceleration signals directly.Simulation and analysis indicate that the dynamic stiffness of servo system can be enhanced and the starting and braking performance is improved with the AFB.Experiments show that the capability of resisting friction moment is increased significantly.The capability of resisting periodic disturbance is increased by 9.3db and the overshoot of speed step response is decreased by 4.9%,while the transition process has been greatly improved.The servo system has simpler structure,higher robustness,and shows better universality.

A dual-detector compound-axis APT scheme of airborne laser communication is proposed,according to the environment of communication link.The compound axis consists of Coarse Tracking Assembly(CTA) and Fine Tracking Assembly(FTA).A detailed analysis and optimization design of whole optical path structure is carried out.Then a technique about switching between coarse beacon and fine beacon is put forward.This way improves energy density of fine beacon and therefore can make CCD high frame work.Finally,it improves servo bandwidth of FTA.CTA performances a wide range of pointing and tracking,with tracking accuracy of up to 120 μrad.However,servo bandwidth of FTA is greater than 300 Hz,with dynamic range of 5 mrad and tracking accuracy of 3 μrad.The plane-to-ground laser communication demonstration experiment is successfully completed,with the distance of 17.5 km,the communication rate of 1.5 Gbps,and BER of less than 1E-7.

In order to lighten the disadvantageous effect of the friction on the machine angular position servo system, the controller is designed using the variable structure control with integral slide mode. The mathematical model of the machine servo system is built with Stribeck friction model. The integral slide mode function includes tracking error and the integral of the tracking error. The one order differential equation of the slide mode is a second-order linear model. In order to alleviate the chattering, the saturation function replaces the sign function. The simulation result show the tracking precision is high and the controller output has not obvious chattering. The controller meets the tracking precision of the machine angular position servo system.

The direct-drive ring permanent magnet torque motor is easily affected by parameters changes and the load torque disturbances, which reduces the servo performance of the system. In order to enhance the robustness of the servo system, the super twisting algorithm based on the second order sliding mode control (SMC) is proposed as the speed controller of the direct-drive servo system. The super twisting algorithm need not know the information of the sliding mode time derivative, which through the continuous control measure the sliding mode and its derivative approach zero in finite time. This method not only guarantees the robustness of the servo system and eliminates chatting, but also enhances the static precision of the servo system. The simulation results show that the servo system of the direct-drive NC rotary table has a very strong robustness by adopting the control method against parameters changes and the external disturbances.

RC servos are electro-mechanical devices that respond to a control signal, which instructs them to move their output shaft to a certain position. A servo is normally plugged into a radio receiver with a three pin connector. The three wires are a power (usually 4.8V to 6.0V), a ground, and a signal wire. The signal wire carries a PWM (Pulse-Width Modulation) signal consisting of a 1-2msec pulse repeated 50 times a second. A 1.5msec pulse will tell the servo to move to its output shaft to the center position, 0 degrees. For a servo with a 180 degree of motion, a 1msec pulse will move the servo to -90 degrees, and a 2msec pulse will move the servo to +90 degrees. In order to development a humanoid robot, mechanical design, fixtures design, analysis of kinematics, implementation moving program, selection of RC servo motor and controller are required. This study was performed to experimentally compare the rotation range of RC servo motors according to change of a periods.

In order to suppress the friction and leakage interference of continuous rotary electro-hydraulic servo motor, make the motor tracking the periodic signals with high accuracy, and improve the high frequency response performance of continuous rotary electro-hydraulic servo motor, this paper established the mathematic model of the electro-hydraulic position servo system of the continuous rotary motor, and adopted the controlling method based on the zero phase error tracking controller to suppress the interference. Through the simulation, the result confirms that the zero phase error tracking control method decreases the tracking error of the system, increases the robust performance of the system and improves the frequency response performance of continuous rotary electro-hydraulic servo motor. This method is simple and feasible.

To eliminate the errors of cylinders’ dynamic output positions of master side for the influence of random disturbance of slave side, master-slave position controller based on disturbance state observer optimal control and robust dynamic compensate PD feedback control algorithm is designed for electro-hydraulic servo tele-robot. A linear quadratic with disturbance observer and a dynamic robust compensator position controller is developed. Experimental results demonstrated the proposed algorithm is availability and showed that the designed controllers both improved position tracking precision for master-slave side and possessed good adaptive ability and robustness in existence of uncertain disturbance, enhanced the operational performance.

Backlash in servo mechanisms causes a severe deterioration in system performance. To reduce the influence of backlash on the system, a backstepping integral adaptive control is proposed. A dynamic model of a servo mechanism with backlash, considering equivalent stiffness and damping, is established. The control design is achieved by introducing parameter adaptation with a backstepping technique that ensures the convergence of parameter estimation and global stability of the adaptive system. Simulation and experimental results show that the system’s tracking accuracy and servo bandwidth are significantly improved and increased. More importantly, the impact and oscillation are evidently reduced while reversing, compared with conventional proportional-integral-derivative control.

There are some problem for Strip transmission process, such as low deviation information accuracy , poor reliability, poor control results,the electro-hydraulic servo central position control system of Strip based on the principle of differential capacitance was designed. The differential connection is used for eliminating signal drift and the nonlinear characteristics，high frequency power supply is used for reducing output impedance and improving the system bandwidth, double shielded is used for eliminating the impact of parasitic capacitance, the electro-hydraulic servo central position control system based on fuzzy PID is designed. Research shows that the measuring circuit and control system are with high precision, good reliability, maintenance-free advantages.

To meet requirement of swiftness and minimization for the tracking system as well as realize horizontal high accuracy tracking measurement, the automatic servo tracking measurement system has been designed. The two closed loop control, bisection method and compound control have been applied into the system. Experimental results show that the maximum tracking error can be limited to less than 0.5°and the regulator time can be 0.04s. The control project resonance frequency should be more than 200Hz and the sample frequency should be more than 400Hz to meet the control accuracy requirement. And these specific mechanical properties indexes are useful to mechanical working to make sure the design can be realization. So the research in this paper has important value to the engineering practice.

The positioning accuracy achievable by track-follow servo for flexible tape media is investigated using advanced concepts for several elements of the system. First, the servo pattern geometry in the timing-based servo system is designed in conjunction with a digital synchronous servo channel to minimize the measurement error in the position-error signal. Second, a flangeless tape path is introduced to mitigate high-frequency components of the lateral tape motion. Finally, a track-follow controller is designed based on the H ∞ approach, taking into account the disturbance and noise characteristics of tape path and servo-channel and the measured plant transfer function. Combining these elements with a new high SNR magnetic tape based on perpendicularly-oriented BaFe particles, we demonstrate a closed-loop track-follow performance with a standard deviation of the position-error signal of less than 15 nm.

A novel slider-based micro-actuator for magnetic disk drive was designed and fabricated to improve the magnetic head positioning accuracy. The micro-actuator consists of a head slider, an actuator base, flexible hinge elements, and a pair of unimorph actuators which has piezo-electric transducers and actuator arms as components. The slider body is able to rotate around the center of mass, and the movable end of the actuator arms are contacted but not fixed to the slider body, so the arms won't constrain the slider rotation and results to a large stroke. The actuator arms are actuated by piezo-electic transducers to apply a rotation torque to the slider. The stroke of 0.16µm peak-to-peak was obtained under a drive voltage of +/-20V and the frequency response of the slider tip excited by the piezo-electric actuators was fairly well, with slider sway mode frequency of 21.8kHz. The evaluation results showed the micro-actuator is able to improve the servo bandwidth, implemented in the disk drive in the future.

This paper presents a controller design approach to provide the precise force control considering compensation for interference and disturbance in load devices. In the control system, a pneumatic actuator and a voice coil motor are combined as a dual-stage actuator to expand the servo bandwidth of the load control. The interference between the actuators, however, deteriorates the servo performance, especially at around the cross-over frequency. In addition, the disturbance generated by an abrasive motor deteriorates the tracking performance for the target value. In this research, therefore, a PQ method is adopted to achieve the high precision load control by expanding the servo bandwidth. Here, the compensators are designed to compensate for the interference, while a resonant filter is designed to suppress the disturbance with the specific frequency, paying attention to a vector locus of the open-loop characteristic. The proposed approach has been verified by experiments using an actual load device.

In order to realize high speed control of some ac servo system, aimed at all kinds of uncertain factors such as greatly changing moment and torque, and strong impact torque. Therefore, for gaining good speed tracking characteristics, adaptive disturbance observer is adopted to observe load torque disturbance and speed variation. Stability of closed loop system is guaranteed by design of control tractics to satisfy track control requests of rocket launcher servo system. Simulation results indicate that this method can ideally observe disturbance and reduce output of controller, thus control performance of the system is improved and is greatly meaningful.

In order to suppress the periodic interference of continuous rotary electro-hydraulic servo motor, make the motor tracking periodic signals more accurate, and improve the influence of friction interference on the performance of continuous rotary electro-hydraulic servo motor, mathematic model of continuous rotary motor electro-hydraulic position servo system was established, and the compound control method based on the discrete sliding mode controller was adopted to suppress the friction interference. Through the simulation, the result confirms that the discrete sliding mode controller decreases the tracking error of the system, increases the system robust performance and improves performance of continuous rotary electro-hydraulic servo motor. This method is simple and feasible.

To overcome the limit on the natural resonant frequency and bandwidth of the traditional single-axis servo system, the paper designed a double-axis compound servo system, and established the transfer function of the fast reflector, camera, D/A data acquisition card and velocity servo unit, and further obtained the transfer function and theory model of this servo system. By combining simulation, it analyzed the influence of the dynamic hysteresis error, flat vibration error, centroid detection error, mechanical torque distortion error on the accuracy of the system. It proposes the view that the modern synthesize algorithm can optimize and compensate the parameter of the fast reflector system, by this method designed robust controller can restrain the remaining low frequency distortion and high frequency noise of the system, and further improve the bandwidth and accuracy of the system. The experiment shows that the compound-axis servo system bandwidth is of 2-16Hz and system accuracy of 0.8-4μrad.The experimental results and theory analysis are compatible basically. The design provides a foundation for the study on the servo system in the fields of the space optical communication system, deep space detection, remote sensing and etc

This paper proposes a space voltage vector modulation (SVM) method for a speed servo system to obtain a quick current response. The proposed SVM method shortens the control lag time of the conventional SVM inverter. In addition, this proposed method is easily implemented in hardware using an FPGA (Field Programmable Gate Array) because the proposed SVM equations are transformed into expressions that hardly need multiplication. By using the proposed SVM method, the servo system realizes quick and stable current control with wide bandwidth. Moreover, by using PI controllers considering the voltage saturation and the torque limiter to the speed servo system, the servo system carries out stable speed control on voltage saturation. Both the proposed SVM method and the PI controllers considering voltage saturation are applied to the speed servo system of a vector controlled induction motor. The effectiveness of both the proposed SVM method and the PI controllers considering voltage saturation is verified by the experimental results. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(1): 60–68, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20989

In this paper, we investigate the effect of read head profile on the playback signal from data and servo sector in a staggered bit-patterned-media recording system. The scaling of the read head is targeted to achieve better data signal quality while such scaling is shown to have negative effect on the servo signal. A secondary servo burst that uses data samples to generate supplementary PES is then proposed and its feasibility is demonstrated.