Small Linear Actuator Research Articles

Design and Optimization of a Custom-Made Six-Bar Exoskeleton for Pulp Pinch Grasp Rehabilitation in Stroke Patients.

Stroke often causes neuromotor disabilities, impacting index finger function in daily activities. Due to the role of repetitive, even passive, finger movements in neuromuscular re-education and spasticity control, this study aims to design a rehabilitation exoskeleton based on the pulp pinch movement. The exoskeleton uses an underactuated RML topology with a single degree of mobility, customized from 3D scans of the patient's hand. It consists of eight links, incorporating two consecutive four-bar mechanisms and the third inversion of a crank-slider. A two-stage genetic optimization was applied, first to the location of the intermediate joint between the two four-bar mechanisms and later to the remaining dimensions. A targeted genetic optimization process monitored two quality metrics: average mechanical advantage from extension to flexion, and its variability. By analyzing the relationship between these metrics and key parameters at different synthesis stages, the population evaluated is reduced by up to 96.2%, compared to previous studies for the same problem. This custom-fit exoskeleton uses a small linear actuator to deliver a stable 12.45 N force to the fingertip with near-constant mechanical advantage during flexion. It enables repetitive pulp pinch movements in a flaccid finger, improving rehabilitation consistency and facilitating home-based therapy.

G100025 リニア駆動の小型振動アクチュエータに関する基礎検討

In this study, we consider the utilization of vibration as a mean of information transmission in place of utilization of the sound. In order to achieve reliable vibration transmission and for realizing a variety of vibration patterns, we investigate the basic design of small linear actuator driven by magnetic force. Using only a coil and permanent magnet, we study whether it is possible to generate the vibration with various frequencies. The magnetic force acting between the magnet and the coil is measured in the experiment, and using measured force, numerical simulation is conducted to evaluate the amount of vibration induced by the actuator. Vibration waveform is mesured by non-contact laser displacement meter. We also pay attention to compact and simple structure of the actuator. The frequency of the continuous vibration could be confirmed until 180 Hz. Frequencies above 200 Hz vibration was not continuous. The amount of vibration is 1.1 〜 1.8 times larger than conventional vibration equipment.

Design and optimization of a linear actuator for subminiature optical storage devices

Recent advancements in mobile devices have fueled a requirement for information storage systems with characteristics such as subminiature size, low cost, and minimum power consumption. Small optical disk drives could provide a good solution, because their storage media is cheaper than those of hard disk drives or flash memories. In this paper, a small linear actuator that can be used to provide seeking and fine tracking for small optical disk drives was designed using structural and electromagnetic analyses. The designed actuator was optimized by applying design of experiments (DOE) and response surface method (RSM) techniques to verify the effectiveness of the initial design and further improve its performance characteristics, such as output power and compactness. The dynamic performance of the designed linear actuator was evaluated by experiments.

小形リニア電磁アクチュエータの特性評価

Linear actuators have been used in a wide range of fields in the recent years. A linear actuator has a simple structure and is easy to miniaturize. The small size and high thrust of linear actuators are essential for office and factory automation.This paper discusses a comparison of the characteristic evaluations of linear actuators. The type of small linear actuator to be investigated is defined as one having an input power of 100 W or less. The expressions of the motor constant of moving-magnet- type and moving-coil-type linear actuators were examined theoretically and compared.

摩擦駆動式マイクロ圧電リニアアクチュエータの研究 グリップ式圧電リニアアクチュエータの推力特性

This paper reports study on a very small linear actuator which can have big force, long stroke and precise positioning capability. Although the actuator is driven by multilayer piezoelectric devices in cyclic way, small displacement is continuously transmitted to a slider through friction drive method. The spring plates which are fixed on both sides of the slider press the actuator grip points and the pressing force generates friction drive force. The maximum pressing force under which the actuator can work normally is calculated by FEM analysis. As a result, the actuator with an appropriate structure is designed, fabricated and experimentally evaluated. The factors which give effects to thrust force characteristics are studied.

MAGNETIC FIELD AND FORCE CHARACTERISTICS OF A SOLENOID ACTUATOR FOR DISPLAY BOARD APPLICATION

The work described concerns a technical assessment of a small linear actuator that was developed for use in large, electronically controlled, electromechanical display boards. Each pixel of the board is driven by an individual actuator and displays alternative colours to the viewer, according to the position occupied by its armature. In operation, the whole screen can be refreshed a few times per second, and an actuator life of about 100M operations is required. No coil excitation must be needed when the armature is stationary, to minimise heating. Detent positions are therefore essential and these are achieved with the aid of a permanent magnet.

Linear electrostatic actuators: Gap maintenance via fluid bearings

This paper addresses a novel actuator for manufacturing applications, the “electrostatic artificial muscle.” Artificial muscle is composed of a dense array of small linear actuators. Its promise lies in the prospect of high performance (e.g. higher force-to-weight ratio and peak acceleration than a comparable magnetic motor), clean, quiet operation, and design versatility (especially the elimination of transmissions in many applications). The characteristics of artificial muscle are particularly appealing for applications in robotics and high-speed automation. A model of a linear electrostatic induction motor is presented to illustrate the potential for high performance as well as the difficulty of “gap maintenance.” Gap maintenance refers to the demanding task of preserving a uniform, narrow gap between “slider” and stator in the presence of destabilizing electrostatic forces. A novel approach to gap maintenance, the use of dielectric fluid bearings, is presented. Analysis of a simple, 2-D motor model shows that gap maintenance and motor efficiency may be characterized by two nondimensional parameters: a levitation number, and a gap aspect ratio. It is shown that achieving both low-speed levitation and high efficiency requires long, narrow gaps (high aspect ratio). The results of this analysis are extended to a more complex model featuring an unconstrained, rigid slider. An experimental study of fluid bearings is also presented.