Search Results (10)

Enhancing the transparency of high-transmission-ratio linear actuators is crucial for improving the safety and capability of high-force robotic systems having physical contact with humans in unstructured environments. However, realizing such enhancement is challenging. A proposed solution for active body weight support systems involves employing a macro–mini linear actuator incorporating an electrorheological-fluid brake to connect a high-force unit with an agile, highly back-drivable unit. This paper introduces the use of an electromagnetic (EM) brake with reduced rotor inertia to address this challenge. The increased torque capacity of the EM brake enables integration with a low-gear-ratio linear transmission. The agile translation of the endpoint is propelled by a low-inertia motor (referred to as the “mini”) via a pulley-belt mechanism to achieve high transparency. The rotor of the EM brake is linked to the pulley. Damping modulation under high driving force is achieved through the adjustment of the brake torque relative to the rotational speed of the pulley. When the brake is engaged, it prevents any relative motion between the endpoint and the moving carrier. The endpoint is fully controlled by the ball screw of the high-force unit, referred to as the “macro”. A scaled prototype was constructed to experimentally characterize the damping force generated by the mini motor and the EM brake. The macro–mini linear actuator, equipped with an intrinsic failsafe feature, can be utilized for active body weight support systems that demand high antigravity force. Full article

The article incorporates an analysis of the switching-on process of alternating current (AC), low-voltage (LV), and electromagnetic (EM) relays energized by harmonically polluted voltage sources. In the undertaken research, the dynamic parameters of relays actuated by electromagnetic drive were examined for shape and supply voltage waveform distortion levels as described by different THD factor values. During the research, diverse supplying voltages were delivered to drive electromagnet coils at a variety of phases so as to reflect the stochastic nature of the energizing procedure. The performed analysis allowed for determining the most influential and decisive factors dictating the basic parameter values of the switching-on process. As an outcome, time-related parameters of relay moving armature movement were obtained, and the frequency of disorder occurrences during the switching-on was examined. For experimentation needs, an experiment stand was developed, and dedicated software for measurement results analysis was elaborated. Based on the study results, EM relay switching-on operation reliability was evaluated in view of electric energy quality. Full article

This work introduces a novel sensing concept based on reaction forces for determining the position of the levitating magnet (mover) for magnetic levitation platforms (MLPs). Besides being effective in conventional magnetic bearings, the applied approach enables operation in systems where the mover is completely isolated from the actuating electromagnets (EMs) of the stator (e.g., located inside a sealed process chamber) while levitating at an extreme levitation height. To achieve active position control of the levitating mover by properly controlling the stator’s EM currents, it is necessary to employ a dynamic model of the complete MLP, including the reaction force sensor, and implement an observer that extracts the position from the force-dependent signals, given that the position is not directly tied to the measured forces. Furthermore, two possible controller implementations are discussed in detail: a basic PID controller and a more sophisticated state-space controller that can be chosen depending on the characteristics of the MLP and the accuracy of the employed sensing method. To show the effectiveness of the proposed position-sensing and control concept, a hardware demonstrator employing a 207 mm outer-diameter (characteristic dimension, CD) stator with permanent magnets, a set of electromagnets, and a commercial multi-axis force sensor is built, where a 0.36 kg mover is stably levitated at an extreme air gap of 104 mm. Full article

Saving energy from domestic appliances is a focus in the effort to combat energy challenges. Linear compressors are a more efficient alternative to the traditional compressors used in refrigerators, which account for 20–40% of all residential electricity use. This article investigates the new topology of the moving magnet (MM), dual-stator single-mover linear oscillating actuator (DSSM-LOA) for linear compressor application. Both the stators were C-shaped, with coils looped across their end sides. Two permanent magnets (PMs) that were axially magnetized were housed on the mover. The PM structural shape significantly affected its fabrication cost and magnitude of magnetic flux density ($B$). The DSSM-LOA makes use of axially magnetized rectangular-shaped PMs because they are inexpensive and generate high electromagnetic (EM) force density. End ferromagnetic core materials were used to improve the magnetic flux, linking from the stator to the mover. All the design parameters were optimized through parametric analysis using the finite parametric sweep method. Parameters present within the three primary parameters (length, height, and depth) that were assumed constants were optimized, and the optimal dimensions were selected based on the EM force. The investigated DSSM-LOA was contrasted with traditional LOA designs, and they showed significant improvement in EM force per ampere, generally named motor constant (MC), MC per PM mass, MC density, cogging force, and stroke. Additionally, the proposed DSSM-LOA had a simple structure and low cost, and it operated in a feasible range of strokes for linear compressor application. Full article

Nowadays, vehicle industries are trying to introduce actively controllable variable valve trains to achieve maximumly efficient internal combustion engines. The electromagnetic valve train (EMV) is one of the promising valve actuators. A traditional electromagnet valve needs to be continuously supplied with current and consumes more energy during valve opening and closing, and the permanent magnet-assisted valves have a demagnetization issue. Thus, this study presents a hybrid permanent magnet electromagnetic valve (PMEMV), which needs a power supply only for a short interval of time during valve opening or closing; eventually, this PMEMV consumes much less energy than conventional EMVs. This paper proposed an improved control approach for this hybrid PMEMV to achieve variable valve actuation. Magnetic stimulation was performed on the proposed valve train to analyze the direction of the magnetic circuit during the valve actuation. An improved magnetic circuit control method was introduced to achieve the release and attraction of the armature. This innovative magnetic circuit control can make the armature effectively attract at each apex, so that the PMEMV can be effectively and completely actuated. The prototype of the valve train and the experimental platform were developed to test and validate the real-time performance of the composite EM valve. Peripheral sensor components were used to measure the valve displacement. The experimental results proved that the concept of the innovative magnetic-circuit drive and control can enable the successful operation of the hybrid compound EM valve. Full article

Implantable medical devices have been facing the severe challenge of wireless communication for a long time. Acoustically actuated magnetoelectric (ME) transducer antennas have attracted lots of attention due to their miniaturization, high radiation efficiency and easy integration. Here, we fully demonstrate the possibility of using only one bulk acoustic wave (BAW) actuated ME transducer antenna (BAW ME antenna) for communication by describing the correspondence between the BAW ME antenna and components of the traditional transmitter in detail. Specifically, we first demonstrate that the signal could be modulated by applying a direct current (DC) magnetic bias and exciting different resonance modes of the BAW ME antenna with frequencies ranging from medium frequency (MF) (1.5 MHz) to medium frequency (UHF) (2 GHz). Then, two methods of adjusting the radiation power of the BAW ME antenna are proposed to realize signal amplification, including increasing the input voltage and using higher order resonance. Finally, a method based on electromagnetic (EM) perturbation is presented to simulate the transmission process of the BAW ME antenna via the finite element analysis (FEA) model. The simulation results match the radiation pattern of magnetic dipoles perfectly, which verifies both the model and our purpose. Full article

The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a novel method for achieving position synchronization within CCMM architecture by using closed-loop feedback of variable stator resistances in parallel induction machines. The feasibility of the method is demonstrated in several case studies using electromagnetic transient simulation on a set of parallel induction machines experiencing different load torque conditions, with the central converter implementing both voltage-based and current-based primary control strategies. The key result of the paper is that the CCMM architecture with proposed feedback control strategy is shown in these case studies to dynamically drive the position synchronization error to zero. The initial findings indicate that the CCMM architecture with induction motors may be a viable option for implementing EM-TRAS in future aircraft. Full article

Semi-active knee orthosis (SAKO) is a kind of wearable lower-limb exoskeleton that uses actuators to support the regular biomechanical functions. It is much better than conventional knee orthosis (CKO) devices because of its high torque to volume ratio (TVR) and low mass. Magnetorheological (MR) brake is one of the smart actuators that can be used as an active resistance device in SAKO. It has advantages of fast response, low power consumption, and low vibration operation. This smart brake also has wide applications in the robotic and automotive industries. However, the electromagnetic setup in MR brakes has a hysteresis problem. This paper aims to turn this hysteresis problem into an advantage to save the power consumption of MR brake. Since the SAKO needs precise torque control, this research studied the hysteresis effect on the torque performance of MR brake. A less energy-consuming PWM actuation signal is proposed to activate the MR brake. The effects of frequency and duty cycle of PWM actuation signal on MR brake performance are also investigated. The electromagnetic (EM) and mechanical models of the MR brake were developed to simulate performance. Initial validation of these models is done by simulating the MR brake model with the DC actuation signal in finite element analysis software. For the final validation, the model simulation results are compared with experimental results. The factors affecting the steady torque and the response time of the MR brake are studied to find the optimal frequency and duty cycle for the applied PWM signal. This study revealed that the proposed new PWM actuation signal with a 5 kHz frequency and 60% duty cycle can power the MR brake to maintain steady torque. By turning hysteresis into an advantage, it saves 40% power consumption of MR brake compared to DC signal. Full article

In this study, we present a comprehensive review of polymer-based microelectromechanical systems (MEMS) electromagnetic (EM) actuators and their implementation in the biomedical engineering field. The purpose of this review is to provide a comprehensive summary on the latest development of electromagnetically driven microactuators for biomedical application that is focused on the movable structure development made of polymers. The discussion does not only focus on the polymeric material part itself, but also covers the basic mechanism of the mechanical actuation, the state of the art of the membrane development and its application. In this review, a clear description about the scheme used to drive the micro-actuators, the concept of mechanical deformation of the movable magnetic membrane and its interaction with actuator system are described in detail. Some comparisons are made to scrutinize the advantages and disadvantages of electromagnetic MEMS actuator performance. The previous studies and explanations on the technology used to fabricate the polymer-based membrane component of the electromagnetically driven microactuators system are presented. The study on the materials and the synthesis method implemented during the fabrication process for the development of the actuators are also briefly described in this review. Furthermore, potential applications of polymer-based MEMS EM actuators in the biomedical field are also described. It is concluded that much progress has been made in the material development of the actuator. The technology trend has moved from the use of bulk magnetic material to using magnetic polymer composites. The future benefits of these compact flexible material employments will offer a wide range of potential implementation of polymer composites in wearable and portable biomedical device applications. Full article

A valveless electromagnetic (EM) micropump with a matrix-patterned magnetic polymer composite actuator membrane structure was successfully designed and fabricated. The composite membrane structure is made of polydemethylsiloxane (PDMS) that is mixed with magnetic particles and patterned in matrix blocks. The matrix magnetic composite membrane was fabricated using a soft lithography process and expected to have a compact structure having sufficient magnetic force for membrane deformation and maintained membrane flexibility. The magnetic membrane was integrated with the microfluidic system and functionally tested. The experimental results show that a magnetic composite actuator membrane containing of 6% NdFeB is capable of producing a maximum membrane deflection up to 12.87 µm. The functionality test of the EM actuator for fluid pumping resulted in an extremely low sample injection flow rate of approximately 6.523 nL/min. It was also concluded that there is a correlation between the matrix structure of the actuator membrane and the fluid pumping flow rate. The injection flow rate of the EM micropump can be controlled by adjusting the input power supplied to the EM coil, and this is believed to improve the injection accuracy of the drug dosage and have potential in improving the proficiency of the existing drug delivery system. Full article