Design and Analysis of a Novel Composited Electromagnetic Linear Actuator

Electromagnetic linear actuators, as key executive components, have a vital impact on the performance of fully flexible variable valve trains. Considering that the conventional moving coil electromagnetic linear actuator (MCELA) has the disadvantages of low force density and a lack of end-passive self-holding ability, a novel composited electromagnetic linear actuator (CELA) is proposed by combining the performance advantages of MCELA and moving iron electromagnetic linear actuator (MIELA) in this work. Firstly, the structure and magnetic circuit design scheme of the proposed actuator are introduced and the finite element simulation model is established. The magnetic field distribution and force characteristics of the actuators are assessed by finite element simulation. Secondly, the construction of the prototype of the actuator is outlined, based on which the feasibility of the design scheme and the steady-state performance of the actuator are verified. Finally, the coordinated control strategy is proposed to realize the multi motion coordination control of the actuator. The research results show that the maximum starting force of the CELA with the end-passive self-holding ability is 574.92 N while the holding force can approach 229.25 N. Moreover, the CELA is proven to have excellent dynamic characteristics and control precision under different motion modes and to have an improved adaptability to the complex working conditions of internal combustion engines.

A hybrid linear actuator based on screw clamp operation principle: Design and experimental verification

This paper presents a hybrid linear actuator using screw clamp operation principle. The actuator mainly consists of a hollow electromagnetic torque motor located between two clamping nuts, two hollow cylindrical shaped piezoelectric stacks symmetrically configured at two ends of the actuator and a feed-screw (also considered as the mover of the actuator) assembled throughout all the parts. The torque motor is symmetrically connected to two clamping nuts via two torsion coupling springs located at either end of the motor spindle. Two piezoelectric stacks can work independently to propel the opposing loads, which effectively take advantage of the anti-compression and non-tensile characteristics of piezoelectric element. The special feature of the actuator is the screw clamp mechanism, the operation of which involves intermittent rotation of two nuts (driven by the torque motor) on a feed-screw to achieve the bi-direction piezoelectric motion accumulation. Furthermore, the application of feed-screw could decrease the actuator’s sensitivity to wear, in order to realize a rigid self-locking and thus ensure the actuator’s holding capacity. A prototype was fabricated and the experimental results show that the no-load speed, maximum thrust, and peak power of the actuator were 20 mm/s, 280 N, and 1.54 W, respectively.

Incremental Linear Switched Reluctance Actuator

Linear switched reluctance actuators are a focus of study for many applications because of their simple and robust electromagnetic structure, despite their lower thrust force density when compared with linear permanent magnet synchronous motors. This chapter deals with incremental linear actuator have switched reluctance structure. First, the different topologies of linear incremental actuators are mentioned. Furthermore, a special interest is focused on the switched reluctance linear actuator then the operating principal is explained. In addition, an analytical model of the proposed actuator is developed without taking account of the saturation in magnetic circuit. Finally, the control techniques that can be applied to the studied actuator are presented.

Effectiveness of Combined Stretching and Strengthening Exercise Using Rehabilitation Exercise System with a Linear Actuator and MR Damper on Static and Dynamic Sitting Postural Balance: A Feasibility Study

Postural imbalance induced by prolonged sitting can be improved by exercise therapy. The aim of study was to evaluate the influence of combined stretching and strengthening exercise using rehabilitation exercise system with a linear actuator and MR damper on static and dynamic sitting postural balance. Twelve subjects who sit almost 10 h a day participated in this study. The rehabilitation exercise system with a linear actuator and MR damper was manufactured to provide stretching and strengthening exercise. All subjects were asked to perform an exercise program that was designed to enhance postural balance by stretching the tight muscle and strengthening the weakened muscle. Body pressure distributions were analyzed for mean force and mean pressure using a seat sensor system. Trunk muscle activities were measured by attaching surface electrodes to the thoracic erector spinae, lumbar erector spinae, and lumbar multifidus muscle. All data were divided into two regions (dominant and non-dominant side) under four conditions: no pelvic tilt, lateral pelvic tilt, anterior pelvic tilt, and posterior pelvic tilt. Body pressure distributions and trunk muscle activities were compared between before and after performing exercise under static and dynamic sitting conditions. Both in static and dynamic sitting conditions, there were significant differences in body pressure distributions and trunk muscle activities between the DS and NDS before performing the exercise (p < 0.01). After performing exercise, the body pressure distributions increased on the dominant side while those decreased on the non-dominant side significantly (p < 0.01). In addition, the activities of all trunk muscles on the non-predominant side increased significantly (p < 0.01 and p < 0.05). These results showed that postural balance was improved by decreasing the differences in body pressure distribution and trunk muscle activity between the dominant and non-dominant side after performing exercise. From the results of this study, we concluded that the rehabilitation exercise system with a linear actuator and MR damper is suitable for providing combined stretching and strengthening exercise, and it could be helpful to maintain correct posture by enhancing postural balance during sitting.

Design of a variable stiffness index finger exoskeleton

This paper presents the design and experimentation of a variable stiffness index finger exoskeleton consisting of four-bar mechanisms actuated by a linear actuator. The lengths of the four-bar mechanism were optimized so that it can follow a recorded index fingertip trajectory. The mechanism has a fixed compliance at the coupler of the four-bar link and a variable compliance at the linear actuator that moves the four-bar. The skeletal shape of the coupler of the finger link has been optimized using FEM. The exoskeleton can apply a constant fingertip force irrespective of the position of the fingers.