Operation Of Linear Motor Research Articles

Performance of a linear refrigeration compressor with small clearance volume

Linear compressors are attractive for domestic refrigerator owing to high efficiency, free piston and possible oil-free operation. Minimizing the clearance volume is an approach to increase the volumetric efficiency thus cooling capacity. This is particularly beneficial for refrigerants that require high displacement due to high friction. However, operation of linear motor with offset may deteriorate the motor efficiency due to earlier saturation. This paper experimentally compares the refrigeration performance of a linear compressor using R1234yf among using various clearance volumes and using an offset of 0 mm. Measurements with different clearances and an offset of 0 mm were carried out for compressor strokes of 11–13 mm and pressure ratios of 2.5–4.0 using R1234yf. The cooling capacity for a pressure ratio of 2.5 and a stroke of 13 mm increases by 12% as the clearance decreases from 1.07 mm to 0.4 mm. Although the motor efficiency is sacrificed, the overall coefficient of performance (CoP) increases particularly for high pressure ratio.

Enhanced Complex Space Vector Modeling and Control System Design of Multiphase Magnetically Levitated Rotary–Linear Machines

Rotary–linear electric machines can perform coupled rotary and linear motion. In addition, they can have magnetic bearings (MBs) integrated and magnetically coupled with the rotary, linear, or rotary–linear machine operation. Since rotary–linear machines with MBs have not been thoroughly analyzed in the literature, the models that provide understanding of their operation and give basis for the control system implementation are not entirely covered. Hence, in this article, an enhanced complex space vector-based model of the rotary–linear machine with MBs is derived and expressions for the torque, thrust force, and MB force are given. The rotary–linear machine complex space vector of the voltage, current, or flux linkage is defined using the proposed transformation with two complex frames: one related to the rotation and MBs and another to the linear motion. This results in complex space vectors with two complex units; however, the techniques used for a conventional complex space vector calculation can also be applied to the proposed complex space vector description. This is also experimentally validated on a hardware prototype of a magnetically levitated linear tubular actuator (MALTA), whose position control system is designed and implemented based on the enhanced space vector modeling approach, with the dynamic operation of the MALTA, including linear motor operation with an axial stroke of 10mm and a mechanical frequency of 17Hz.

A smart experimental technique for the optimization of dielectric elastomer actuator (DEA) systems

In order to aid in moving dielectric elastomer actuator (DEA) technology from the laboratory into a commercial product DEA prototypes should be tested against a variety of loading conditions and eventually in the end user conditions. An experimental test setup to seamlessly perform mechanical characterization and loading of the DEA would be a great asset toward this end. Therefore, this work presents the design, control and systematic validation of a benchtop testing station for miniature silicon based circular DEAs. A versatile benchtop tester is able to characterize and apply programmable loading forces to the DEA while measuring actuator performance. The tester successfully applied mechanical loads to the DEA (including positive, constant and negative stiffness loads) simulating biasing systems via an electromagnetic linear motor operating in closed loop with a force/mechanical impedance control scheme. The tester expedites mechanical testing of the DEA by eliminating the need to build intricate pre-load mechanisms or use multiple testing jigs for characterizing the DEA response. The results show that proper mechanical loading of the DEA increases the overall electromechanical sensitivity of the system and thereby the actuator output. This approach to characterize and apply variable loading forces to DEAs in a single test system will enable faster realization of higher performance actuators.

A square-plate piezoelectric linear motor operating in two orthogonal and isomorphic face-diagonal-bending modes

We report a piezoelectric linear motor made of a single Pb(Zr,Ti)O3 square-plate, which operates in two orthogonal and isomorphic face-diagonal-bending modes to produce precision linear motion. A 15 × 15 × 2 mm prototype was fabricated, and the motor generated a driving force of up to 1.8 N and a speed of 170 mm/s under an applied voltage of 100 Vpp at the resonance frequency of 136.5 kHz. The motor shows such advantages as large driving force under relatively low driving voltage, simple structure, and stable motion because of its isomorphic face-diagonal-bending mode.

A square-plate ultrasonic linear motor operating in two orthogonal first bending modes

A novel square-plate piezoelectric ultrasonic linear motor operated in two orthogonal first bending vibration modes (B₁) is proposed. The piezoelectric vibrator of the linear motor is simply made of a single PZT ceramic plate (sizes: 15 x 15 x 2 mm) and poled in its thickness direction. The top surface electrode of the square ceramic plate was divided into four active areas along its two diagonal lines for exciting two orthogonal B₁ modes. The achieved driving force and speed from the linear motor are 1.8 N and 230 mm/s, respectively, under one pair orthogonal voltage drive of 150 V(p-p) at the resonance frequency of 92 kHz. The proposed linear motor has advantages over conventional ultrasonic linear motors, such as relatively larger driving force, very simple working mode and structure, and low fabrication cost.

Transformer Characteristics of Linear Motor-Transformer Apparatus

The characteristics of linear transformer are studied analytically. The transformer is composed in one of modes of linear motor-transformer apparatus proposed for future wireless light rail vehicle (LRV). The secondary (onboard) power factor can be adjusted at any value by an onboard converter. The equivalent circuit is used to study the transferred power control. The parameters are determined by three-dimensional finite element method (FEM) analysis for one pole-pair model. Under the rated primary (input) and secondary voltage and current, which are specified for linear motor operation, the characteristics of the secondary power factor are cleared. It is also shown that the input capacitor can improve the primary power factor and decrease the input power capacity, but does not change the efficiency. This linear transformer has the efficiency of 91% and the input power factor of 0.87 when the apparatus without input capacitor is controlled at the secondary power factor of 0.4.

Design of Multisectional Driver and Field-Oriented Modeling of the Axial-Flux Linear Brushless Motor for Railway Transportations

A multisectional power driver design for the two-phase linear brushless motor is proposed in this paper. The field-oriented modeling of the axial-flux linear brushless motor (AFLBM) is also developed by using stationary and cosecant similarity transformation and singular value decomposition. Stationary and cosecant coordinate models were derived based on the proposed approach. Decoupled relation and constant torque property were obtained from the proposed models. Switching logic table for the linear motor operation is provided to drive the AFLBM properly. The switching-mode analysis for the power driver is also analyzed in detail. In order to increase the efficiency and the effectiveness of the electric motor applications, a multisectional driver circuit, which features the power driver with the so-called N + 2 structure, is investigated and compared. Experimental results show that the proposed circuit design can achieve better performance with the higher efficiency. It is believed that the proposed driver circuit technique and system modeling can be very helpful to the control of railway transportations.

Mechanosensory modulation of perioral neuronal groups during active force dynamics.

The spatiotemporal organization of the mechanically evoked perioral sensorimotor response was sampled from five normal females using a custom-designed linear motor operating under force feedback. Electromyographic activity was sampled from the superior and inferior segments of the orbicularis oris muscle during the production of a visually guided ramp-and-hold lip-rounding task. Brief mechanical inputs of approximately 0.45 N delivered to the left upper lip during the ramp-and-hold task produced a composite myogenic response characterized by phases of excitation and suppression. Modulation of the primary excitatory component (R1) of the mechanically evoked perioral response was found to be highly dependent upon the rate of force recruitment (1 N/s vs. 4 N/s) and the phase of force recruitment (20% vs. 50% vs. 80% of 1 N end-point force). Modulation of later occurring inhibitory (S1) and excitatory (R2) potentials were also found to be dependent upon differences in the rate and phase of force recruitment. The organization of the perioral sensorimotor response is considered in relation to speech motor control and the dynamic organization of neuronal groups subserving perioral sensorimotor activity.

Modulation of the mechanically evoked perioral reflex during active force dynamics in young adults

Mechanically evoked reflex activity in the superior and inferior segments of the orbicularis oris muscle was sampled from three normal females using a specially designed linear motor operating under force feedback. Mechanical inputs delivered to the left upper lip during a ramp-and-hold task produced a composite reflex response characterized by phases of excitation and suppression at the homonymous muscle recording site. The modulation of the evoked composite perioral reflex was found to be dependent upon the rate and phase of force recruitment. The organization of the composite perioral reflex response is discussed in relation to speech motor control and load compensatory mechanisms.