Coil Actuator Research Articles

Design and Positioning Control of a Flexure-Based Nano-positioning Stage Driven by Halbach Array Voice Coil Actuator

Design and Positioning Control of a Flexure-Based Nano-positioning Stage Driven by Halbach Array Voice Coil Actuator

A NIR-Light-Driven Twisted and Coiled Polymer Actuator with a PEDOT-Tos/Nylon-6 Composite for Durable and Remotely Controllable Artificial Muscle.

In this paper, we proposed a novel light-driven polymer actuator that could produce remotely controllable tensile stroke in response to near infrared (NIR) light. The light-driven polymer actuator was composed of a twisted and coiled nylon-6 fiber (TCN) and a thin poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonate (PEDOT-Tos) layer. By adopting dip-coating methodology with thermal polymerization process, we constructed a thin and uniform PEDOT-Tos layer on the surface of the three-dimensional TCN structure. Thanks to the PEDOT-Tos layer with excellent NIR light absorption characteristic, the NIR light illumination via a small LEDs array allowed the multiple PEDOT-Tos coated TCN actuators to be photo-thermally heated to a fairly consistent temperature and to simultaneously produce a contractile strain that could be modulated as high as 8.7% with light power. The actuation performance was reversible without any significant hysteresis and highly durable during 3000 cyclic operations via repetitive control of the LEDs. Together with its simple structure and facile fabrication, the light-driven actuator can lead to technical advances in artificial muscles due to its attractive benefits from remote controllability without complex coupled instruments and electromagnetic interference.

A Modified Triaxial Apparatus for Soils under High-Frequency, Low-Amplitude Vibrations

Abstract A modified triaxial apparatus was developed to explore the behavior of cohesionless soil subjected to high-frequency, low-amplitude vibrations, such as those induced by high-speed trains. It was based on a conventional Bishop-type triaxial apparatus to utilize its existing static loading module. The major modification was an added dynamic loading module with a low-inertia linear voice coil actuator mounted coaxially with the vertical loading rod. Through a signal generator and an amplifier connected to the voice coil actuator, a vibration input with wide range of frequencies and amplitudes could be superimposed to a monotonic loading process. A series of tests under different conditions were performed to demonstrate the effectiveness and performance of the modified triaxial apparatus, with the focus being placed on the reduction of shear resistance and accumulative deformation of sand induced by high-frequency, low-amplitude vibrations.

Analysis and Design of a Thomson Coil Actuator System for an HVDC Circuit Breaker

In this study, we analyze and design a Thomson coil actuator system (TCAS) that ensures stable operation of a high voltage direct current circuit breaker. High voltage direct current circuit breakers require a high-speed actuator and proper brake system that can absorb the kinetic energy of fast-moving mass to prevent damage and malfunction of the device. However, existing brake systems degrade the responsiveness of TCAS. Therefore, the proposed TCAS is designed to improve the low responsiveness of the actuator, which is caused by braking forces, by applying a series spring brake system and latch type holding system. An equivalent circuit model of TCAS that reflects its electromagnetic and kinetic properties is derived and applied to the design of the TCAS. The validity of the proposed TCAS design and analysis model is verified through prototype experiments. The experimental results show that the proposed TCAS completes a 30 mm stroke opening operation in 5.4 ms at a drive voltage of 300 V, and the analysis results reveal that the error rate for the experimental results is 4.65 %.

Dual-stage nanopositioner augmented with feedforward control

A piezoelectric walking stage is retrofitted with a secondary stage for precisely tracking ramp position references. Fine motion control of the secondary stage shuttle is achieved using a voice coil actuator to correct for small, periodic deviations in position produced by the walking motion of the piezoelectric drive modules. The shuttle position tracking error is more than an order of magnitude smaller than the walking stage error for velocities less than 1.0 mm/s, however, the shuttle error remains dominated by harmonics of the walking stage stepping frequency. A feedforward controller using a modulated-demodulated implementation is designed to augment the high-bandwidth (300 Hz) shuttle controller to reject three dominant disturbance modes. When the system is tracking a 1.0 mm/s position ramp reference, the modulated-demodulated controller reduces the RMS shuttle position error from 44 to 21 nm. The reported system is under development to meet the scanning requirements of spaceborne Fourier Transform spectrometers.

Design and performance research of high efficiency variable reluctance voice coil actuator

Design and performance research of high efficiency variable reluctance voice coil actuator

Alternative Representation Method of Low Frequency Vibration for Voice Coil Actuators

Alternative Representation Method of Low Frequency Vibration for Voice Coil Actuators

LINEAR SOLENOID ELECTROMAGNETIC ACTUATOR WITH DIFFERENTIAL SERIES WINDINGS

A linear solenoid electromagnetic actuator is a device for creating a linear reciprocating motion with a force effect. It contains a moving part consisting of a permanent magnet in the housing, threaded spacers, threaded rods, nuts for adjusting the stroke of the actuator and the hanging eyes of the actuator. The device further comprises a non-moving part formed by the coil body, the left actuator coil winding, the right actuator coil winding and the actuator cover, the sense of winding the left actuator coil winding opposite.

Design and Dynamic Modeling of a 3-RPS Compliant Parallel Robot Driven by Voice Coil Actuators.

In order to increase the driving force of the voice coil actuator while reducing its size and mass, the structural parameters of the coil and magnet in the actuator are optimized by combing Biot–Savart law with Lagrangian interpolation. A 30 mm × 30 mm × 42 mm robot based on a 3-RPS parallel mechanism driven by voice coil actuators is designed. The Lagrangian dynamic equation of the robot is established, and the mapping relationship between the driving force and the end pose is explored. The results of dynamic analysis are simulated and verified by the ADAMS software. The mapping relationship between the input current and the end pose is concluded by taking the driving force as the intermediate variable. The robot can bear a load of 10 g. The maximum axial displacement of the robot can reach 9 mm, and the maximum pitch angle and return angle can reach 40 and 35 degrees, respectively. The robot can accomplish forward movement through vibration, and the maximum average velocity can reach 4.1 mm/s.

Active tremor control in human-like hand tremor using fuzzy logic

<span>Tremor<span>is the vibration in sinusoidal orientation that is experienced regularly by a person with Parkinson’s disease (PD), which disturbs their daily activities. One solution that may be used to counter this tremor effect is by developing an active tremor control system in LabVIEW for linear voice coil actuator (LVCA), where the system uses proportional (P) controller and various types of fuzzy logic controller (FLC) as a hybrid controller to reduce tremor vibration. From this research, it can be concluded that the best controller for tremor reduction is the P+FLC 1<sup>st</sup> set of rules, compared to P+FLC 2<sup>nd</sup> set of rules, and P controller only, with the highest percentage of 88.39% of tremor reduction with the actual tremor vibration of PD patients as the reference result. The P+FLC 2<sup>nd</sup> set of rules has the highest percentage of tremor reduction with a value of 86.81%, whereas P controller only has the highest tremor reduction percentage of 67.10%. This percentage of tremor reduction is based on the power spectral density (PSD) values, in which it represents the intensity of the tremor vibration. This experimental study can be used as an initial step for researchers and engineers to design and develop an anti-tremor device in the future.</span></span>

Fixed Points on Active and Passive Dynamics of Active Hydraulic Mounts with Oscillating Coil Actuator

Active hydraulic mounts with an inertia track, decoupler membrane, and oscillating coil actuator (AHM-IT-DM-OCAs) have been studied extensively due their compact structure and large damping in the low-frequency band. This paper focuses on a comprehensive analysis of the active and passive dynamics and their fixed points in mid-low-frequency bands, which will be helpful for parameter identification. A unified lumped parameter mechanical model with two degrees-of-freedom is established. The inertia and damping forces of the decoupler/actuator mover may be neglected, and a nonlinear mathematical model can be obtained for mid-low-frequency bands. Theoretical analysis of active and passive dynamics for fluid-filled state reveals the amplitude dependence and a fixed point in passive dynamic stiffness in-phase or active real-frequency characteristics. The amplitude dependence of local loss at the fluid channel entrance and outlet induces the amplitude-dependent dynamics. The amplitude-dependent dynamics constitute a precondition for fixed points. A single fixed point in passive dynamics is experimentally validated, and a pair of fixed points in active dynamics for an AHM-IT-DM-OCA is newly revealed in an experiment, which presents a new issue for further analysis.

Summarisation, Simulation and Comparison of Nine Control Algorithms for an Active Control Mount with an Oscillating Coil Actuator

With the further development of the automotive industry, the traditional vibration isolation method is difficult to meet the requirements for wide frequency bands under multiple operating conditions, the active control mount (ACM) is gradually paid attentions, and the control algorithm plays a decisive role. In this paper, the ACM with oscillating coil actuator (OCA) is taken as the object, and the comparative study of the control algorithms is performed to select the optimal one for ACM. Through the modelling of ACM, the design of controller and the system simulations, the force transmission rate is used to compare the vibration isolation performance of the nine control algorithms, which are least mean square (LMS) adaptive feedforward control, recursive least square (RLS) adaptive feedforward control, filtered reference signal LMS (FxLMS) adaptive control, linear quadratic regulator (LQR) optimal control, H2 control, H∞ control, proportional integral derivative (PID) feedback control, fuzzy control and fuzzy PID control. In summary, the FxLMS adaptive control algorithm has the better performance and the advantage of easier hardware implementation, and it can apply in ACMs.

Voice Coil Actuator를 이용한 고속조준기의 구조설계 및 신뢰성 검증 연구

Because laser weapons are relatively easy to use and can exert powerful energy with high efficiency versus cost, the laser weapons are being developed competitively in the defense industry. A fast steering mirror is the key component for precision tracking and automatic beam alignment, which are the main performances of laser weapons. The purpose of this study is to verify the structural design and driving reliability for implementing the target performance of a fast steering mirror using voice coil actuators. For the performance evaluation of a fast steering mirror, the driving range for the available thrust considering of the electromagnetic force and also the dynamic characteristics within the driving bandwidth were investigated through electromagnetic and structural analysis. In addition, the structural robustness was verified by securing a sufficient safety factor based on the analysis of the fatigue life for the area where the stress was concentrated.

Shaping acoustic radiation induced by vibrotactile rendering on a touch surface

Many electronic devices with touch-sensitive surfaces aim to provide vibrotactile feedback, along with visual or auditory feedback, to facilitate the interaction between the user and the interface. In parallel to these efforts, recent studies developed various vibration rendering techniques, enabling more complex vibration patterns to be generated on the touch surface. However, few have addressed sound radiation induced by vibrotactile rendering on a touch surface, which could significantly impact the haptic interaction's overall perception. This study presents a method to shape the acoustic radiation due to rendering high-fidelity vibrotactile feedback on a touch surface. The proposed method utilizes measured frequency response functions and a vibroacoustic representation of the touch surface to define the relationship between actuator driving signals, vibration responses on the touch surface, and radiated sound power. Proper actuator driving signals are derived from the optimization problem formulated using the relationship. The proposed method was demonstrated through vibration rendering experiments on a touch surface comprising an acrylic plate and voice coil actuators. The results showed that the proposed method could shape the acoustic radiation while rendering target vibration patterns at desired positions on the touch surface. This study's proposed method could allow haptic engineers to design vibrotactile feedback and sound radiation simultaneously for a more compelling haptic experience.

A Low Cost Inkjet-Printed Mass Sensor Using a Frequency Readout Strategy.

The development of low-cost mass sensors is of unique interest for the scientific community due to the wide range of fields requiring these kind of devices. In this paper, a full inkjet-printed mass sensor is proposed. The device is based on a PolyEthylene Terephthalate (PET) cantilever beam (operating in its first natural frequency) where a strain-sensor and a planar coil have been realized by a low-cost InkJet Printing technology to implement the sensing and actuation strategies, respectively. The frequency readout strategy of the sensor presents several advantages, such as the intrinsic robustness against instabilities of the strain sensor, the residual stress of the cantilever beam, the target mass material, and the distance between the permanent magnet and the actuation coil (which changes as a function of the target mass values). However, the frictionless actuation mode represents another shortcoming of the sensor. The paper describes the sensor design, realization, and characterization while investigating its expected behavior by exploiting dedicate models. The working span of the device is 0–0.36 g while its resolution is in the order of 0.001 g, thus addressing a wide range of potential applications requiring very accurate mass measurements within a narrow operating range.

Measurement and modelling of a linear electromagnetic actuator driven camless valve train for spark ignition IC engines under full load condition

Camless engine valve train for gasoline engines particularly port injection engines offer major improvements over traditional system with fixed valve timing and lift, in terms of efficiency, maximum torque and power, and emissions. Electromagnetic driven valve actuators are very promising in this context, but there are significant control problems. The use of displacement sensor could add extra cost to the camless engine. In this work, a moving coil actuator driven valve train was designed and prototyped and a 1D single-cylinder internal combustion engine model was built to investigate the benefit of without throttle by adopting such camless valve train using Ricardo WAVE under full load operating conditions. A novel low-cost sensor named linear actuator position sensor (LAPS) based on flux linkage change on search coil was constructed in LabVIEW by using current, voltage and proximity sensors to detect the valve lift. The measurement of valve lift and current was reported to prove the feasibility of the camless valve train. The valve lift was used for the single-cylinder engine model and the simulation shows that the peak overall engine efficiency using camless valve train reaches 38.2% and the peak torque increases by 5 Nm compared conventional throttled engine under full load operating conditions. The LAPS model was validated by the experimental valve lift and the high accuracy indicates that the LAPS can be adopted for future development of camless valve train for spark ignition IC engines.

Development of a Tactile Actuator with Non-Contact and Trans-Object Characteristics Using a Time-Varying Magnetic Field

A non-contact tactile stimulation system using a time-varying magnetic field was developed. The system comprises a control unit, power unit, output unit, and actuator. The control unit adjusts stimulation parameters, particularly the signal intensity and frequency. The power unit produces high voltages for generating the magnetic field, whereas the output unit transmits the energy generated according to the signal from the control unit to the actuator. A spiral coil actuator generates the magnetic field. To validate the effectiveness of the system, preliminary experiments on 10 male adults without neurological disorders (23.2 ± 3.05 years) were conducted. Magnetic field stimuli were presented to the right palm of the subjects at three different frequencies (10, 30, and 50 Hz), and corresponding electroencephalogram (EEG) signals were measured simultaneously. Event-related potential (ERP) analysis showed that N100 and P300 components were identified in somatosensory areas. Subjective evaluations revealed that feelings such as “tingling,” “trembling,” “tapping,” and “percussing” were induced. Moreover, as the stimulus frequency changes, differences may occur in induced feeling. The system uses a time-varying magnetic field, which not only induces tactile stimulation without contact but also has trans-object characteristics that can present tactile sensations, even when there is an obstacle between an actuator and skin.

Self-Reinforced Nylon 6 Composite for Smart Vibration Damping.

Passive vibration control using polymer composites has been extensively investigated by the engineering community. In this paper, a new kind of vibration dampening polymer composite was developed where oriented nylon 6 fibres were used as the reinforcement, and 3D printed unoriented nylon 6 was used as the matrix material. The shape of the reinforcing fibres was modified to a coiled structure which transformed the fibres into a smart thermoresponsive actuator. This novel self-reinforced composite was of high mechanical robustness and its efficacy was demonstrated as an active dampening system for oscillatory vibration of a heated vibrating system. The blocking force generated within the reinforcing coiled actuator was responsible for dissipating vibration energy and increase the magnitude of the damping factor compared to samples made of non-reinforced nylon 6. Further study shows that the appropriate annealing of coiled actuators provides an enhanced dampening capability to the composite structure. The extent of crystallinity of the reinforcing actuators is found to directly influence the vibration dampening capacity.

Active vibration isolation of ultra-stable optical reference cavity of space optical clock

Space optical clocks with frequency instability better than 1×10−15 are increasingly demanded for PNT (positioning, navigation, and timing) and space physical science. Inevitably, the micro-vibration level in the order of micro-g (μg) is required for ultra-stable optical reference cavity of space optical clocks. The realization of such a strict micro-vibration requirement over broadband frequencies is still technically challenging under complex space disturbances in the order of milli-g (mg). This paper thus proposes a multi-degree of freedom (DOF) active vibration isolation approach for the ultra-stable optical reference cavity to satisfy the stringent micro-vibration requirement. Non-contact voice coil actuators are designed as the driving unit of active vibration isolation. The robust vibration isolation controller is presented considering the control uncertainty caused by the voice coil clearance and the low frequency drift of accelerometers. The loop shaping technology is used to avoid the current drift and achieve high accuracy vibration isolation over the designed bandwidth. The active vibration isolation experimental platform is further developed, and the experimental results validate the effectiveness of the designed multi-DOF active vibration isolation scheme.

Interlaboratory validation of a hanging pendulum thrust balance for electric propulsion testing.

A hanging pendulum thrust balance has been developed by Imperial College London in collaboration with the European Space Agency (ESA) to characterize a wide range of static fire electric propulsion and chemical micro-propulsion devices with thrust in the range of 1 mN to 1 N. The thrusters under investigation are mounted on a pendulum platform, which is suspended from the support structure using stainless steel flexures. The displacement of the platform is measured using an optical laser triangulation sensor. Thermal stability is ensured by a closed loop self-compensating heating system. The traceability and stability of the calibration are ensured using two separate calibration subsystems: a voice coil actuator and a servomotor pulley system. Two nearly identical thrust balances have been constructed, with one being tested in the Imperial Plasma Propulsion Laboratory and the other in the ESA Propulsion Laboratory. Both balances show a high degree of linearity in the range of 0.5 mN-100 mN. Both instruments have demonstrated a stable calibration over several days, with an estimated standard deviation on thrust measurements better than 0.27 mN for low thrust measurements. The same electric propulsion test article was used during both tests: a Quad Confinement Thruster (QCT) variant called QCT Phoenix. This thruster differed from previous QCT designs by having a newly optimized magnetic topology. The device produced thrust up to 2.21 ± 0.22 mN with a maximum specific impulse of 274 ± 41 s for an anode power range of 50 W-115 W.