Voice Coil Motor Research Articles

Servo Controller Design for Triple-Stage Actuator in HDD to Compensate for High-Frequency Fan Vibration

Hard disk drives (HDDs) used for data servers are exposed to various vibrations. These vibrations are mainly caused by the cooling fan that controls the temperature inside the server. The vibration affects the positioning accuracy of magnetic heads that read/write digital data. This is an obstacle to obtaining high data transfer rates. To compensate for vibration, the control system for the magnetic heads must have higher frequency control bandwidth as the spectra of these vibrations have peaks up to 10 kHz. In current HDDs, the control system is a triple-stage system consisting of a voice coil motor (VCM), a milliactuator, and a microactuator. In this article, we propose a design strategy for a triple-stage control system to compensate for vibration. The design strategy addresses unstable controllers in the control system. The gain of the feedback controllers of the VCM and milliactuators is increased to expand the control bandwidth. Although these feedback loops become an unstable system due to the increase in the controller gain, the controller for the microactuator is designed to stabilize the overall feedback loop. As a result, the control system achieves high control bandwidth. The performance of the proposed control system is calculated based on the compensation of the vibration caused by the data server. The proposed design can improve positioning accuracy by approximately 48%–58% compared with the conventional controller design.

A machine for calibrating six-axis force/torque sensors using a torque sensing structure and a stiffness compensation model

In this study, a machine was developed to calibrate six-axis force/torque (F/T) sensors. The reference forces and torques were provided by six electromagnets and two voice coil motors and detected by load cells. The alignments of the electromagnets and moment arms were detected using the strain gauges of a crossbeam in the jig. The stiffness of the jig, position vectors of the application position, and additional forces and torques caused by the deformation of the jig were discussed and estimated to enhance the accuracy of the calibration machine. The output forces and torques were compared with those detected by a commercialized six-axis F/T sensor. The force and torque generation ranges were FX, FY, and FZ = ± 200 N and TX, TY, and TZ = ± 15 N m. The mean difference between the values obtained with the commercialized F/T sensor and the proposed calibration machine was 0.232%, and the mean standard deviation along the six axes was 0.067%. These results indicate that the machine could generate independent calibration forces and torques automatically along six axes for calibrating F/T sensors.

Design of 4-DOF Voice Coil Motor with Function of Reducing Laser Geometrical Fluctuations

In order to improve the quality of the laser and shorten the optical path of the fast steering mirror (FSM) laser compensation system, this paper proposes a four-degrees-of-freedom (4-DOF) voice coil motor (VCM) with the function of reducing laser geometrical fluctuations. The feature of this paper is the combination of a DC brushed spindle motor and the proposed 4-DOF VCM. A diffuser is installed on the shaft of the DC brushed motor for suppressing the laser speckle. The proposed 4-DOF VCM is combined with a laboratory-designed mirror set, controlling the laser direction to compensate for laser fluctuations. The proposed actuator was designed and verified by using the commercial CAD software SolidWorks and finite element analysis (FEA) software ANSYS. A mathematical model was built to simulate the dynamic response of the proposed 4-DOF VCM in MATLAB Simulink.

Research on Control of Stewart Platform Integrating Small Attitude Maneuver and Vibration Isolation for High-Precision Payloads on Spacecraft

The Stewart platform, a classical mechanism proposed as the parallel operation apparatus of robots, is widely used for vibration isolation in various fields. In this paper, a design integrating both small attitude control and vibration isolation for high-precision payloads on board satellites is proposed. Our design is based on a Stewart platform equipped with voice-coil motors (VCM) to provide control force over the mechanism. The coupling terms in the dynamic equations of the legs are removed as the total disturbance by the linear active disturbance rejection control (LADRC). Attitude maneuver and vibration isolation performance is verified by numerical simulations.

The Emirates Mars Mission (EMM) Emirates Mars InfraRed Spectrometer (EMIRS) Instrument

The Emirates Mars Mission Emirates Mars Infrared Spectrometer (EMIRS) will provide remote measurements of the martian surface and lower atmosphere in order to better characterize the geographic and diurnal variability of key constituents (water ice, water vapor, and dust) along with temperature profiles on sub-seasonal timescales. EMIRS is a FTIR spectrometer covering the range from 6.0-100+ μm (1666-100 cm−1) with a spectral sampling as high as 5 cm−1 and a 5.4-mrad IFOV and a 32.5×32.5 mrad FOV. The EMIRS optical path includes a flat 45° pointing mirror to enable one degree of freedom and has a +/- 60° clear aperture around the nadir position which is fed to a 17.78-cm diameter Cassegrain telescope. The collected light is then fed to a flat-plate based Michelson moving mirror mounted on a dual linear voice-coil motor assembly. An array of deuterated L-alanine doped triglycine sulfate (DLaTGS) pyroelectric detectors are used to sample the interferogram every 2 or 4 seconds (depending on the spectral sampling selected). A single 0.846 μm laser diode is used in a metrology interferometer to provide interferometer positional control, sampled at 40 kHz (controlled at 5 kHz) and infrared signal sampled at 625 Hz. The EMIRS beamsplitter is a 60-mm diameter, 1-mm thick 1-arcsecond wedged chemical vapor deposited diamond with an antireflection microstructure to minimize first surface reflection. EMIRS relies on an instrumented internal v-groove blackbody target for a full-aperture radiometric calibration. The radiometric precision of a single spectrum (in 5 cm−1 mode) is <3.0×10−8 W cm−2 sr−1/cm−1 between 300 and 1350 cm−1 over instrument operational temperatures (<∼0.5 K NEDelta T @ 250 K). The absolute integrated radiance error is < 2% for scene temperatures ranging from 200-340 K. The overall EMIRS envelope size is 52.9×37.5×34.6 cm and the mass is 14.72 kg including the interface adapter plate. The average operational power consumption is 22.2 W, and the standby power consumption is 18.6 W with a 5.7 W thermostatically limited, always-on operational heater. EMIRS was developed by Arizona State University and Northern Arizona University in collaboration with the Mohammed bin Rashid Space Centre with Arizona Space Technologies developing the electronics. EMIRS was integrated, tested and radiometrically calibrated at Arizona State University, Tempe, AZ.

Design optimization of tubular linear voice coil motors using swarm intelligence algorithms

This article presents design optimization based on swarm intelligence algorithms of a tubular linear voice coil motor (TLVCM). A magnetic equivalent circuit model is used, allowing a faster and more accurate evaluation of the initial design of the TLVCM. The design requirements are determined, and an initial design is formed based on the design requirements. The TLVCM design is considered a constrained optimization problem with complex linear and nonlinear constraints. The optimization process based on swarm intelligence algorithms is performed to find the optimal solution and improve the performance of the TLVCM. Finally, finite element analysis is used again to verify the optimized results, and different design outputs are compared. According to numerical experimental results, the average thrust is increased by 8.3% and the thrust ripple is reduced by 35.6%. Thus, a highly effective motor design meeting efficiency and performance requirements is achieved.

Parametric Simulations on Leakage and Performance of a Miniature Free-Piston Generator (MFPG)

The miniaturization of electrical equipment and popularization of portable devices is an appealing motivation for the development of small-scale heat engines. However, the in-cylinder charge leaks severely as the engine dimension shrinks. The free-piston engine on a small scale provides better sealing than other miniature heat engines. Therefore, a miniature free-piston generator (MFPG) with a single-piston internal combustion engine (ICE) and a voice coil motor (VCM) was proposed in this work. A dynamic model with special attention on the heat transfer and leakage was established accordingly, upon which parametric studies of leakage and its effects on the performance of the MFPG system were performed. Four key parameters, including scavenging pressure, ignition position, combustion duration and piston mass, were considered in the model. The results showed that the mass leakage during the compression decreases with the rise of the motoring current. The indicated thermal efficiency can be improved by boosting scavenging pressure and increase motoring current. The critical ignition position is 2 mm before the top dead center. When ignition occurs later than that, the MFPG system is incapable of outputting power. The chemical to electric energy conversion efficiency is about 5.13%, with an output power of 10~13 W and power density around 4.7~5.7 W/cc.

A virtual parallel two-point roundness error measurement system

As a typical artifact in machining, the roundness of shaft artifacts is an important tolerance standard. How to measure with high precision in ultra-precision machining is a difficult point. At present, the three-probe method is the most widely used method to measure spindle rotation error and artifact roundness error, which has the advantage of on-machine measurement, but the three-probe method has the critical problem of harmonic suppression. To completely separate the spindle error when measuring the roundness of the artifact, a new virtual parallel two-point measurement system is proposed in this paper. The probe is fixed on the flexible hinge stage, which is driven by a voice coil motor so that the measurement function of two probes can be realized only by using a single probe. Detailed numerical analysis and simulation analysis have been carried out to verify that the method can completely separate the spindle error in theory. Finally, the accuracy of the measurement system is tested through experiments. The new method results are compared with the single-point scanning method without error separation and the high-precision roundness instrument Talyrond 585LT. The comparison results show that the new method can separate the rotation error of the spindle and can improve the roundness measurement accuracy.

A low frequency horizontal active vibration isolation bench for testing the performance of high-precision space inertial sensors

High-precision space inertial sensors are one of the most important payloads in satellite Earth’s gravity measurement and space-based gravitational wave detection due to their extremely high sensitivity. However, seismic noise affects its terrestrial-based performance validation, so that it is very significant to develop low frequency horizontal vibration isolation system to suppress the impact of seismic noise. In this article, a horizontal active vibration isolation bench for terrestrial-based investigation of space accelerometer is developed, on which the motion in three dimensions is monitored by two tri-axis seismometers and actively controlled by three voice coil motors. The principle and potential performance of this bench are theoretically analyzed and estimated in details. The experimental result shows that the bench can achieve high vibration isolation performance in horizontal translation direction. The residual horizontal vibration noise of this bench due to seismic can be suppressed by about 40 dB at 0.35 Hz. Finally, the potential of this design as a vibration pre-isolation stage to investigate the performance of the inertial sensors dedicated to satellite gravity measurement and space gravitational wave detection is discussed.

원거리 가스 모니터링용 분광 센서를 위한 이동반사경의 개발

Spectroscopic sensors have been used in the field of optics and chemical analysis, and the need for remote gas monitoring in a portable form has increased. Hence, it is essential to design, manufacture, and develop a moving mirror, which that can generate the optical path difference for spectroscopic sensor. It is important to verify whether it can satisfy design requirements for the actual spectroscopic interferometer application by evaluating its performance. In this paper, a moving mirror assembly with high-speed transfer capability for a portable spectroscopic sensor is fabricated and tested. For application to a portable spectrometer, design requirements, such as moving distance, speed, and stiffness, are set and the mechanical structure, including the voice coil motor and elastic guide, satisfying these requirements is proposed. Through finite element analysis, performance of the proposed moving mirror assembly is predicted. By testing the performance after fabrication, it is verified that the proposed mirror is capable of linear movement with travel distance of several millimeters and moving speed of tens of Hz. Optical testing result shows that the proposed moving mirror can generate linear motion with a tilting error below 10 arcsecond and can be applied to the actual spectroscopic interferometer in future.

A step-up approach for selecting substitute suppliers under nonlinear profile data

ABSTRACT Selecting qualified suppliers from a group of candidates is important to procurement. Having several qualified suppliers to choose from can increase production flexibility and bargaining power. This research aims at selecting the substitute suppliers that can produce the parts with the same quality as the current supplier. Most of the existing supplier selection methods focused on univariate or linear profile data, which are insufficient to solve the supplier selection problem under nonlinear profile data. This research develops a step-up approach to select qualified suppliers for substitution under nonlinear profile data where there exists a nonlinear functional relationship between the quality characteristic and the explanatory variable. The proposed approach uses polynomial regression followed by the sequential test procedure to compare profile differences. The simulation results show that the proposed approach can reject the suppliers with different profile functions from the current supplier with satisfying power levels. To illustrate the effectiveness and practicality, the proposed approach is applied to select qualified voice coil motor (VCM) suppliers for a digital camera module manufacturer. Procuring the VCM from the selected suppliers can fulfill a higher demand, while maintaining the operational function and quality of the digital camera module.

Design and Simulation of Novel 3-DOF Spherical Voice Coil Motor

Multi-DOF motion is realized in the eyes and joints of robots mostly through the combination of multiple one-degree-of-freedom (1-DOF) motors. However, this results in reduced efficiency, a large volume, reduced response speed, and inaccurate positioning. To solve these problems, this study proposes a novel 3-DOF spherical voice coil motor (VCM). In this VCM, 16 coils and a radially oriented ring magnet are used to generate a Lorentz force to achieve motion. In particular, coils for Z-axis rotation are sandwiched between the coils for X- and Y-axis rotation. Furthermore, the proposed VCM can achieve 360° rotation about the Z-axis. The commercial software ANSYS was used to design and verify the performance of the proposed VCM. Simulation results indicate that this VCM affords improved power efficiency because only a suitable combination of coils, rather than all coils, needs to be powered on. The results demonstrate the feasibility of the proposed 3-DOF spherical VCM.

Head-Positioning Control in Triple-Stage-Actuator Enterprise Hard Disk Drives Using Mixed H2/H∞ Synthesis Methodologies

Abstract The recent rapid growth in the cloud storage industry has strongly increased the demand for high-capacity enterprise hard disk drives (HDDs). Increasing the areal density brings new challenges to the high-accuracy head-positioning control in the next generation HDD development. Triple-stage-actuator (TSA) system is one of the emerging technologies (Atsumi, 2016, “Emerging Technology for Head-Positioning System in HDDS,” IEEJ J. Ind. Appl. 5(2), pp. 117–122.) that can achieve higher bandwidth than that of a dual-stage-actuator (DSA) system and improve the track-following performance. In this paper, we focus on the TSA system with one voice coil motor (VCM) and two piezoelectric (PZT) actuators. Two types of mixed H2/H∞ synthesis methodologies based on model-based optimization and data-driven optimization are proposed to design the track-following controller for the TSA system. The simulation results show the feasibility and effectiveness of the TSA systems with a tertiary PZT actuator. We also analyze the effects of stroke limitations and resonance frequencies of the second-/third-stage PZT actuators on the head-positioning accuracy. The results might provide a guideline for the TSA mechanical design.

Development of dual-mode precision current source for macro-microcomposite actuator based on field programmable gate array.

To meet the requirements of variable input current forms, microstep adjustment, low error coefficient, high output linearity, and the low ripple of macro-microcomposite actuators developed by combining voice coil motors and a giant magnetostrictive actuator, in this study, a design scheme of dual-mode precise programmable current sources based on a field programmable gate array (FPGA) was proposed. First, according to the working principle and control characteristics of macro-microcomposite drivers, an overall circuit system model of a driving power supply was established. Second, based on the circuit operational amplifier principle, an output current equation of the power supply was obtained, and a current switching circuit and a dual-mode current sampling circuit were designed. Finally, an FPGA was used as the current control core, and an incremental PI algorithm was introduced to compensate for the current feedback. The experimental results showed that the precision current source can output two current modes (positive current 0-5A and positive and negative current -5 to 5A) under the FPGA control. The average current error coefficient of the output in the two current output modes was ε ≦ 0.006, the maximum nonlinearity was ηmax ≦ 0.005, and the error between the current adjusting step value and the preset value was less than 1%.

Investigation on the Modeling and Dynamic Characteristics of a Novel Hydraulic Proportional Valve Driven by a Voice Coil Motor

As the key control component of the water hydraulic systems, the water hydraulic proportional valve has a significant influence on the control performance of the systems. Due to the poor viscosity and lubricity of water, the valve spool resistance is large and non-linear. In this study, a novel fast-response water hydraulic proportional valve is presented. The actuator of the valve adopts a voice coil motor (VCM), which has the advantages of fast response, high control precision and small volume. In order to realize the fast control of the valve, a lever amplifier is designed to obtain enough actuation force. A detailed and precise non-linear mathematical model of the valve considering both the valve’s structural parameters and VCM electromagnetic characteristics is developed. A comprehensive performance simulation analysis has been carried out, mainly divided into an electromagnetic simulation, an analysis of the characteristics of the lever magnifier, and a dynamic performance simulation of the valve. The simulation results show that the adjusting time is about 28ms, and the maximum overshoot is about 5 %. The step response rise time is about 15 ms. The test rig of the valve and VCM have been built. The test results of the prototype show that the optimal stroke range of VCM is 4 mm to 15 mm. The maximum overshoot of the valve is around 10 %; the adjusting time is about 30 ms in the opening process and 35 ms in the closing process. The test results prove that the valve has good static and dynamic control performance.

Design and Analysis of a High Thrust Linear Voice Coil Motor Using for the Stiffness Test of Linear Motor Servo System

Linear voice coil motors (VCMs) are widely used in some high precision or high dynamic applications, such as lithography, digital cameras, and microscopes. In this article, a high thrust linear VCM is analyzed and designed, which is used for the position loop stiffness test of linear motor servo system. To guarantee the structural strength of coil frame and provide space for the cooling channels, the two layers’ coil arrangement is adopted. Based on 2-D finite element method (FEM), the thrust and thrust ripple performance of the motor are analyzed. Moreover, a reasonable cooling structure integrated with the coil frame is designed to further improve the thrust density. Finally, a linear VCM prototype with a thrust rating of 1000 N is manufactured and tested. The static thrust test results show that the thrust varies linearly with the coil current. The motor can provide a nearly constant thrust and thrust ripple within ±2 mm displacement is less than 1%, which agrees well with finite element simulation. In addition, the temperature test is also achieved. Compared with natural cooling condition, the thermal equilibrium can be achieved among the coil, coil frame and cooling water with the water-cooling condition, when the current density is 15.3 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Furthermore, a good overall cooling effect and low surface temperature rise can be realized when two heat shield cover plates are fixed onto both sides of the primary.

Dual feedback based bipolar current source with high stability for driving voice coil motors in wide temperature ranges

Bipolar current sources with a stability better than 0.1% in the temperature range of -30 to +70 °C are demanded for driving voice coil motors applied in a new ultra-quiet satellite platform, but almost none of the existing designs satisfy the harsh requirements. This paper presents a possible solution, which is essentially a floating-load, bipolar current source circuit with a dual feedback path. The key circuit is a composite amplifier (co-amp) composed of a high precision amplifier for error correction and a high power amplifier for load driving. The first feedback path comprises a specially designed four-wire current-sense resistor for current-to-voltage conversion and a discrete instrumentation amplifier for amplifying the converted voltage and closing the loop. The second feedback path is a proposed compensation network for loop stability. Error budgets for evaluating current stability and choosing key components of the circuit are comprehensively studied based on a derived rigorous current equation. Loop-stability problems attributable to the inductive load and the high open-loop gain of the co-amp are analyzed, and the proposed dual feedback compensation method is verified by theory, simulation, and measurement. All these contributions are demonstrated by three implemented prototypes with an output of up to ±2A. The measured results agree well with theoretical predictions. The best and the worst stability performances of the three prototypes at +2 and -2A are, respectively, 394 and 986 ppm in the temperature range of -30 to +70 °C, which are close to the theoretical value of 776 ppm.

A novel master-slave intraocular surgical robot with force feedback.

Intraocular surgery is one of the most challenging microsurgeries. Unintended movements of human hand and lack of force feedback can seriously affect surgical safety. We developed a novel master-slave robotic system with force feedback to assist intraocular surgeries. Isomorphism design was adopted to achieve intuitive control of the system. Contact force between instrument tip and tissues was measured with a force sensor developed by our group. Real-time force feedback was provided with one linear voice coil motor and two magnetic particle brakes in the master manipulator. Experiments were carried out to verify the proposed system. In the phantom experiment mimicking realistic surgical operations, the contact force significantly reduced by more than 30% with the force feedback when peeling the egg inner shell membranes. Experimental results demonstrate the effectiveness of force feedback and indicate the promise of the presented master-slave robotic system for intraocular surgery assistance.

A wearable light-touch contact device for human balance support

There is an urgent need for the development of ways to address the major issue of falls among today’s globally aging population. The authors here outline a new approach referred to as virtual light-touch contact to mitigate postural sway during ambulatory and stationary periods, and propose a wearable light-touch (WLT) system featuring a virtual partition around the user that allows determination of virtual forces resulting from related contact. The data produced are used to create vibrotactile fingertip feedback, which supports comprehensive perception of the partition. Non-impaired subjects were recruited to support evaluation of the prototype system (incorporating tactile stimulation and motion-capture technology), with outcomes showing successful mitigation of postural sway in a heel-to-toe tandem stance. Research performed with 150 able-bodied volunteers to validate the performance of the new set-up (incorporating an acceleration sensor and a voice coil motor to render the light-touch effect) suggested that the proposed WLT approach supports human balance on a level comparable to that of the light-touch effect.

Magnetic Field Model of Macro-motion of Coaxial Integrated Macro-micro Composite Actuator

Aiming at the problem of short stroke of giant magnetostrictive actuator (GMA), a design scheme of coaxial integrated macro-micro composite actuator is proposed by combining the long-stroke characteristics of voice coil motor with the high-precision characteristics of giant magnetostrictive actuator. Based on its structure composition and working principle, the magnetic field model of macro-motion of macro-micro composite actuator is established based on the analysis method of circuit, and the change characteristics of the driving magnetic field are obtained. The finite element method is used to verify the magnetic circuit characteristics. The results show that the magnetic circuit variation characteristics of the proposed coaxial integrated macro-micro composite actuator are consistent with the theoretical calculation results, and are consistent with the expected working process of this actuator, which indicates that the established magnetic field model is correct, and that the proposed coaxial integrated design scheme of the macro-micro composite actuator is feasible.