Query: voice coil motor

title: A cost effective voice coil motor based portable micro indentation device for in situ testing
abstract: To evaluate the mechanical properties of structures in service, a portable micro indentation device was developed and built. The basic design principle of the indentation device, i.e. measurement of the indentation depth and the indentation force with sufficient accuracy, was discussed. To avoid using load cell to decrease the machine compliance, a new method that using the current through voice coil motor to calculate the indentation force was proposed. After analyzing the equivalent mechanical model of the developed device, an eddy current displacement sensor was installed on the device to improve the measurement accuracy of indentation depth. Indentation tests were performed on polymethylmethacrylate (PMMA) and unplasticized polyvinyl chloride (UPVC) with the developed device and the commercial indentation device ZHU2.5 to demonstrate the validity and accuracy of the developed micro indentation device.

title: LCL Filter Design and Implementation for Improving Transient Position Tracking Control Performance of Voice Coil Motor
abstract: Voice coil motor (VCM) is widely used in high precision position servo control for its merits of high linearity and no cogging torque. There are two conventional driving modes: PWM chopper drive and analog drive. PWM chopper drive usually results in current ripples, which could affect position control precision. Acceptable current ripple limits the increase in the DC bus voltage and could not achieve faster response. On the other hand, analog drive uses power amplifiers, which does not suffer from current ripple but can result in high power loss. Such power loss could also affect precision or result in cooling difficulty, especially for thermal sensitive applications such as semi conductor lithography. In this paper, a VCM chopping drive with an LCL filter together with filter design method is proposed. Unlike conventional LCL filter design for grid inverter that only focuses on steady state current quality, the proposed LCL filter design in this paper aims at transient position control, which considers the current ripple, transient position tracking time and additional volume. With the designed filter, position tracking time can be shortened with acceptable current ripple. To compensate the delay caused by LCL filter, the DC drive voltage is increased. And under the same current ripple level, with LCL filter and higher DC voltage can get faster position response speed than without LCL filter and lower voltage. The results are validated by simulation and experimental results.

title: Design of a Voice Coil Motor Actuator With L Shape Coils for Optical Zooming Smartphone Cameras
abstract: This paper proposes a voice coil motor (VCM) with a novel electromagnetic structure for smartphone OZ actuators, and the advantages of this novel design are its long displacement, compact size, and more powerful and stable Lorentz force. These advantages are achieved by the novel electromagnetic structure that consist of L shape coils. Its performances were verified by a laboratory built prototype, and the experimental results (Lorentz force <inline formula> <tex math notation="LaTeX"$F_{VCM} /tex math>/inline formula> response time, and zoomed images) can prove the proposed VCM actuator is feasible and vigorous.

title: Bi stable actuator measurement method based on voice coil motor
abstract: Bi stable actuator (BA) has been widely used in industry as an energy converter because of low power consumption. However, the holding force, start up force and dynamic performance under load are difficult to comprehensively test by existing measurement method. A measurement method is proposed in this paper, a voice coil motor (VCM) acts as both a force sensor and a load simulator, which significantly simplifies the complexity of device. The core VCM was designed based on the analysis of the system's structure and principle. Besides, a force tracking controller was built without a feedback signal from routine force sensor. Meanwhile, the MAP of VCM's displacement current force was obtained and the target force tracking test was carried out by VCM's calibration experimental setup. Finally, the force characteristics and dynamic characteristics of a BA were tested to verify the effectiveness and reliability of the measurement method. The results show that the tracking precision of VCM under step signal and slope signal is 2 N, which achieves the requirement of load simulator combining with fast response. Moreover, the results of BA's force characteristic agree well with those through a traditional complex test system. Additionally, BA's moving time under linear load is 3 ms, which is hard to obtain by traditional measurement methods. Although in this paper the methodology was employed to a BA, its structure can be used to test a wide range of linear actuator.

title: An embedded electrical impedance analyzer based on the AD5933 for the determination of voice coil motor mechanical properties
abstract: The voice coil motor (VCM) is a simple electromechanical linear motor used in space constrained applications such as pumps, precision positioning, and mobile camera lens actuation. The motion of a VCM is determined by the applied current as well as the mechanical parameters of mass, spring constant, and damping coefficient. VCM motion and mechanical parameters can be determined by a position sensor, but such a sensor may be too bulky for a miniaturized solution. To overcome this limitation, measurements of the VCM electrical impedance versus frequency can be combined with an electromechanical model to identify mechanical parameters. Here we detail an analytical model that relates the electrical impedance to mechanical parameters and demonstrate a miniaturized electrical impedance analyzer for VCMs designed around the AD5933 integrated circuit. The electrical instrument measures impedances of a typical VCM coil of ~10 O with a signal to noise ratio of 84.7 dB. We display the effectiveness of the analytical model and impedance analyzer by identifying mechanical parameters of mass, spring constant, and damping coefficient using electrical impedance measurements alone. We experimentally modified the system mass and detected the changes using electrical impedance with a mean error of 5.6% and a Pearson's correlation coefficient of r 0.95. Repeated measurements of a single VCM configuration demonstrated that the natural frequency, knowledge of which is critical for optimal efficiency, was detected with a variation of 0.2% A departure from harmonic motion was observed at low velocities. We explain this departure by adding static friction to the model of VCM motion. The AD5933 based miniaturized VCM driver and impedance analyzer coupled with a model that relates mechanical motion to electrical impedance is a viable instrument for in situ diagnostics and tuning of VCMs.

title: Effect of Characteristic Parameters on the Magnetic Properties of Voice Coil Motor for Direct Fuel Injection in Gasoline Engine
abstract: In this paper, the effects of driving current and voice coil motor's (VCM) structure parameters (e.g. magnetizer height, width of working air gap and damping hole angle) on the static electromagnetic characteristics are numerically investigated. The results show that the driving current has remarkable effects on the electromagnetic force before magnetic saturation; the oversize current applied to the coil would weaken the electromagnetic conversation because of the energy losses. Besides, the permanent magnets' structure were researched, in order to achieve the stronger electromagnetic force, the magnetizer was embedded in the middle of two permanent magnets, and the static electromagnetic characteristics were investigated. Furthermore, damping holes have significant influence on magnetic flux, the tendency of magnetic saturation will be enhanced with the further increase of damping hole. Among other parameters studied, air gap is the most important parameter affecting electromagnetic force owing to the variation of magnetic induction intensity.

title: Design of linear voice coil motor with semi closed structure
abstract: A Halbach permanent magnet (PM) tubular linear voice coil motor (LVCM) with a semi closed structure is developed to enhance the thrust density in this study. Generally, the end of conventional LVCM is open and suffers from the considerable end reluctance. The usage of Halbach array in LVCM makes this problem more prominent although it improves the air gap flux density greatly. The flux at the end of LVCM can be guided to improve the air gap flux density. Therefore, this study aims to constrain and direct the magnetic field at the end of a Halbach PM LVCM by using a ferromagnetic auxiliary yoke to construct a semi closed structure. Magnetic equivalent circuit method is utilised to analyse the effect of the auxiliary yoke on air gap flux density. Besides, finite element analysis is used to analyse the magnetic circuit and design the parameters of LVCM. The semi closed tubular LVCM topology is manufactured and the effectiveness of this topology is validated by experimental measurements. Results show that the thrust density of LVCM is improved effectively by using an auxiliary yoke at the end.

title: Analysis and Design of Ironless Toroidal Winding of Tubular Linear Voice Coil Motor for Minimum Copper Loss
abstract: Due to the ironless structure of the toroidal winding in the tubular linear voice coil motor (TLVCM) the winding thickness is one of the critical parameters that have an impact on air gap flux density, and hence affects the copper loss at rated thrust. This paper investigates and determines the thickness of the ironless toroidal winding of the TLVCM for the purpose of a minimum copper loss. Magnetic equivalent circuit (MEC) method is used to analyze the air gap flux density with respect to winding thickness, and the corresponding copper loss at the rated thrust is assessed by considering the slot fill factor. The optimal solution is obtained according to the U shaped curve of the copper loss. Moreover, the finite element analysis is combined to validate the results of MEC method, and a good agreement is reached. Two prototypes of TLVCMs having similar slot fill factor are made, one of which is with the optimal winding thickness. The expected current at the rated thrust is obtained by a test platform of static thrust, so as to obtain the corresponding copper loss for each prototype. The experimental results show that the TLVCM with optimal winding thickness features a lower copper loss. Hence, the attempt to minimize the copper loss by designing the thickness of the ironless winding is highly effective.

title: Optimization and simulation of a voice coil motor for fuel injectors of two stroke aviation piston engine
abstract: Two stroke engines taking advantages of high power density and light weight as well as small size are widely used on aircrafts. Compared with conventional fuel injection system, gasoline direct injection technology can control the air fuel ratio according to different working conditions and thus a more efficient combustion can be achieved. Normally, a solenoid valve is employed in the gasoline fuel injectors to control the injected fuel amount and timing. In this study, the performance of a novel voice coil motor for gasoline direct injection injectors of a two stroke aviation engine is studied. The voice coil motor works as a linear actuator to pressurize the fuel, and thus the amount of injected fuel and the injection timing can be controlled by the driving current of the coil. As a result, the high pressure pump of the conventional fuel injection system can be canceled. The working principle of the voice coil motor is described at first. Then, a finite element model of the voice coil motor is setup, and the influences of structure parameters including the coil turns, the magnetizer height, and the yoke thickness are analyzed. Subsequently, the magnetic equivalent circuit methodology is used to study the response characteristics of the voice coil motor. The results show that the coil turns, the magnetizer height, and the yoke thickness are three important parameters that will influence the electromagnetic force. The total mass and resistance of the coil and the coefficients k and ke are four important parameters that will influence the dynamic response time. A theoretical optimization of these parameters can improve the system performance of the voice coil motor significantly. The results of this study can provide a reference for the design of gasoline direct injection system for aviation piston engines.

title: Decentralized vibration control of a voice coil motor based Stewart parallel mechanism: Simulation and experiments
abstract: In pursuit of a better working performance of the precise instruments equipped in spacecraft, vibration control systems are essential for preventing them from being disturbed. This paper studies the decentralized vibration control problems of a voice coil motor based Stewart parallel mechanism. The Newton Euler Method is used to formulate the dynamical equations of the Stewart platform in joint space. The decentralized control theory is employed to design the controller for the linearized system. A prototype of the voice coil motor based Stewart platform was designed and tested to validate the vibration attenuation performance of the decentralized system. The effectiveness of active vibration isolation system is revealed by both the simulation and real time experiments.