Search Results (43)

Dog clutches are superior to synchromesh units due to much less wear caused by friction but require an external torque source to synchronize the rotation speeds. The current trend in e-mobility to use the driving motor of an electric vehicle as this source just creates another problem, which is known as torque holes. In this work, we propose a novel double-sided dog clutch that synchronizes the speeds electromagnetically by itself avoiding mechanical contact between the parts. A shift sleeve, two coils placed coaxially in their stators, and two complementary rings form an electromagnetic reluctance actuator, which is integrated inside the gearbox between two gearwheels and represents the double-sided clutch. Thus, intermediate parts between the shift sleeve and the actuator are not required. Both actuator sides can produce axial force and electromagnetic torque. However, torques and forces are generated simultaneously on both sides. Therefore, a special control algorithm is developed to keep the resulting axial force approximately equal to zero while the torque is generated in the neutral gear position. After the synchronization, the axial force is applied on the corresponding side to shift the required gear engaging the shift sleeve teeth directly with the slots of the complementary ring mounted on the gearwheel. So, an axial contact of the teeth at an unaligned state, which can lead to unsuccessful shifting, is avoided. A testrig, which includes a clutch prototype and a testing two-speed gearbox, has been designed and built. The developed theoretical ideas have been verified during the experiments under different conditions. The experiments confirm that the actuator can reduce positive and negative speed differences on both sides and subsequently shift the gear without a shift sleeve collision at misaligned angular positions. Full article

Robotic auscultation has the potential to solve problems associated with gender issues by allowing examinations that eliminate the need for physical contact between doctor and patient. Aiming toward a robotic auscultation device capable of safely acquiring chest and back auscultatory sounds simultaneously, this study aimed to develop a unique actuator-less hugging mechanism with a multi-acoustic sensor array that can be transformed to wrap around the chest and back to fit the patient’s body shape. The mechanism consists of a twin-articulated arm with multi-layer gear coupling and a cam mechanism for power transmissions. The hugging motion is generated by pushing the cam mechanism by the patient. The force applied to the cam mechanism acts as the driving force for the twin-articulated arm. The trajectory of the arm changes depending on the distance that the cam mechanism is pressed, and it was designed to fit typical body types (obese, standard, and slender). Our results demonstrated that the proposed mechanism was able to be transformed for each body type, and its positional error was less than 15 mm in all body types. This means that the proposed mechanism is capable of safely acquiring chest and back auscultatory sounds whilst simultaneously fitting to various body shapes. Full article

Recent advancements in Electrowetting on Dielectric (EWOD) systems, such as simplified fabrication, low-voltage actuation, and the development of more reliable materials, are expanding the potential applications of electrowetting actuators. One application of EWOD actuators is in RF devices to enable dynamic reconfiguration and allow real-time adjustments to frequency and bandwidth. In this paper, a method is introduced to actuate a panel using EWOD forces. In the EWOD system, the velocity of the plate increases by maximizing the actuation force, minimizing the moving mass (droplets and metalized plate), and reducing resistance (contact line drag, fluid drag). However, some of these are competing factors. For instance, the actuation force can be increased by increasing the number of droplets, but this also increases the inertia and the drag force. An analytical model of EWOD actuation is presented to understand system performance tradeoffs. The model is validated with an EWOD experiment, and the data demonstrate less than a 7.8% error between the measured and predicted maximum plate velocities for different voltage inputs. In addition, this study presents a 3D numerical FEM model to analyze the velocity profile and viscous force in the thin droplets, focusing on variations along the droplet’s height, which cannot be captured experimentally. The main advantage of the proposed system over previous works is the simple 2D manufacturing process, which allows embedding metalized plates and RF circuit boards, in addition to being compact, portable, and low-cost. In addition, the proposed method does not have any mechanical components, which can increase the system’s reliability in a harsh environment. Full article

The rapid evolution of microelectronics and display technologies has driven the demand for advanced manufacturing techniques capable of precise, high-speed microchip transfer. As devices shrink in size and increase in complexity, scalable and contactless methods for microscale placement are essential. Laser-induced forward transfer (LIFT) has emerged as a transformative solution, offering the precision and adaptability required for next-generation applications such as micro-light-emitting diodes (μ-LEDs). This study optimizes the LIFT process for the precise transfer of silicon microchips designed to mimic μ-LEDs. Critical parameters, including laser energy density, laser pulse width, and dynamic release layer (DRL) thickness are systematically adjusted to ensure controlled blister formation, a key factor for successful material transfer. The DRL, a polyimide-based photoreactive layer, undergoes photothermal decomposition under 355 nm laser irradiation, creating localized pressure that propels microchips onto the receiver substrate in a contactless manner. Using advanced techniques such as three-dimensional profilometry, X-ray photoelectron spectroscopy, and ultrafast imaging, this study evaluates the rupture dynamics of the DRL and the velocity of microchips during transfer. Optimization of the DRL thickness to 1 µm and a transfer velocity of 20 m s⁻¹ achieves a transfer yield of up to 97%, showcasing LIFT’s potential in μ-LED manufacturing and semiconductor production. Full article

Electrothermal actuators are highly advantageous for microelectromechanical systems (MEMS) due to their capability to generate significant force and large displacements. Despite these benefits, their application in reconfigurable conduction line switches is limited, particularly when employing commercial processes. In DC MEMS switches, electrothermal actuators require electrical insulation between the biasing voltage and the transmission line to prevent interference and maintain the integrity of the switch. This work presents a chevron-type electrothermal actuator utilizing a stack of $\mathrm{S}\mathrm{i}{\mathrm{O}}_2/$ Al thin films on a silicon (Si) structural layer beam to create a DC MEMS switch. The design leverages a thin film Al heater to drive the actuator while the $\mathrm{S}\mathrm{i}{\mathrm{O}}_2$ layer provides electrical insulation, suppressing crosstalk with the Si layer. The electrical contact resistance of a Si-to-Si interface was evaluated by applying a controlled current and measuring the resultant voltage. A low contact resistance of 150 Ω was achieved when an initial contact gap of 2.52 μm was closed using an actuator with an actuation voltage of 1.2 V and a current of 205 mA, with a switching speed of less than 5 ms. Factors such as the contact force, the temperature, and the residual device layer etching angle significantly impact the Si-to-Si contact resistance and the switch’s longevity. The switch withstands a breakdown voltage up to 350 V at its terminal contacts. Thus, it will be robust to self-actuation caused by unwanted voltage contributions, making it suitable for high-voltage and harsh environment applications. Full article

Digital microfluidics is a novel technique for manipulating discrete droplets with the advantages of programmability, small device size, low cost, and easy integration. The development of droplet sensing methods advances the automation control of digital microfluidics. Impedance measurement emerges as a promising technique for droplet localization and characterization due to its non-invasive nature, high sensitivity, simplicity, and cost-effectiveness. However, traditional impedance measurement approaches in digital microfluidics based on the high-voltage actuating signal are limited in sensing accuracy in practical applications. In this paper, we propose a novel droplet impedance sensing system for digital microfluidics by introducing a low-voltage and addressable measurement circuit, which enables impedance measurement over a wide frequency range. The proposed measurement system has also been used for detecting the droplet composition, size, and position in a digital microfluidic chip. The improved impedance sensing method can also promote the applications of the digital microfluidic, which requires high accuracy, real-time, and contactless sensing with automatic sample pretreatment. Full article

This work investigates a new sensing technology for use in robotic human–machine interface (HMI) applications. The proposed method uses near E-field sensing to measure small changes in the limb surface topography due to muscle actuation over time. The sensors introduced in this work provide a non-contact, low-computational-cost, and low-noise method for sensing muscle activity. By evaluating the key sensor characteristics, such as accuracy, hysteresis, and resolution, the performance of this sensor is validated. Then, to understand the potential performance in intention detection, the unmodified digital output of the sensor is analysed against movements of the hand and fingers. This is done to demonstrate the worst-case scenario and to show that the sensor provides highly targeted and relevant data on muscle activation before any further processing. Finally, a convolutional neural network is used to perform joint angle prediction over nine degrees of freedom, achieving high-level regression performance with an RMSE value of less than six degrees for thumb and wrist movements and 11 degrees for finger movements. This work demonstrates the promising performance of this novel approach to sensing for use in human–machine interfaces. Full article

Compared to other actuating methods, acoustic actuators offer the distinctive capability of the contactless manipulation of small objects, such as microscale and nanoscale robots. Furthermore, they have the ability to penetrate the skin, allowing for the trapping and manipulation of micro/nanorobots that carry therapeutic agents in diverse media. In this review, we summarize the current progress in using acoustic actuators for the manipulation of micro/nanorobots used in various biomedical applications. First, we introduce the actuating method of using acoustic waves to manipulate objects, including the principle of operation and different types of acoustic actuators that are usually employed. Then, applications involving manipulating different types of devices are reviewed, including bubble-based microrobots, bubble-free robots, biohybrid microrobots, and nanorobots. Finally, we discuss the challenges and future perspectives for the development of the field. Full article

Magnetic gears (MGs) emerged as an interesting alternative to conventional mechanical gears, owing mainly to their high torque densities and contactless operation. This paper presents a novel observer-based position control system for a magnetic-geared servo drive. The presented control system is based on two well established control strategies—field-oriented control (FOC) and state feedback control. The former is used to achieve effective torque control of a permanent magnet synchronous motor (PMSM) which is considered as an actuator that drives the high-speed rotor, whereas the latter is used to control the position of the low-speed rotor. A reduced-order extended state observer is used to estimate the position and speed of the low-speed rotor, thereby reducing the number of sensors required for the implementation of the controller. The whole control system is implemented on a microcontroller and tested on an existing prototype with a gear ratio of 18:1. The experimental results show that the presented control system guarantees precise positioning within a short amount of time and excellent disturbance rejection. Full article

The growing demand for reliability has led to an increased interest in developing effective disconnection systems for enhancing the safety of and preventing failure escalation in engineering systems. Considering this prospect, the design optimization of two disconnection actuators composed of a coaxial magnetic coupling linked to an electromagnetic device is presented and discussed. The disconnection actuator delivers a contactless torque transmission through the coaxial magnetic coupling, whereas the torque transfer is interrupted by the electromagnetic device in case a failure is detected via a dedicated algorithm. The performed design procedure relies on 2D finite element analysis, and trade-off studies are carried out to achieve an optimized geometry of an electromagnetic device. Finally, two disconnection actuators, for high-speed and high-torque applications, are prototyped and tested, with the aim of evaluating their disconnection capability. For both disconnection actuators, the developed force and voltage–current characteristics are measured along with the disconnection time. Full article

We report on the photo-mobility properties of a free standing large area graphene oxide (GO) paper (GOP). The thickness of the film is ≈20 $\mathsf{\mu }$m. GOP is made by drop casting an aqueous suspension of GO on a microscope glass slide placed on a hot plate kept at the temperature of 70 °C. The film is peeled-off from the glass substrate and irradiated under different coherent and incoherent light sources. The film bends up to ≈55° when the irradiation is made using a near infra-red (NIR) incoherent incandescent lamp and returns back to the initial position when the NIR lamp is switched-off. The bending mechanism is attributed to the asymmetry of the GOP film obtained during the film formation process. We characterize the film morphology and structure using a Scanning Electron Microscopy (SEM) imaging and X-ray Diffraction (XRD) measurements, respectively. Remarkable differences between the two surfaces of the GOP are evidenced, both on a macroscopic length scale (surface roughness) and on a microscopic one (GO interlayer distance). This asymmetry results in different (negative) thermal expansion coefficients for the two film surfaces and hence in the bending of the film when the film temperature is increased by light absorption. Full article

At present, research on intelligent wheelchairs mostly focuses on motion control, while research on attitude-based adjustment is relatively insufficient. The existing methods for adjusting wheelchair posture generally lack collaborative control and good human–machine collaboration. This article proposes an intelligent wheelchair posture-adjustment method based on action intention recognition by studying the relationship between the force changes on the contact surface between the human body and the wheelchair and the action intention. This method is applied to a multi-part adjustable electric wheelchair, which is equipped with multiple force sensors to collect pressure information from various parts of the passenger’s body. The upper level of the system converts the pressure data into the form of a pressure distribution map, extracts the shape features using the VIT deep learning model, identifies and classifies them, and ultimately identifies the action intentions of the passengers. Based on different action intentions, the electric actuator is controlled to adjust the wheelchair posture. After testing, this method can effectively collect the body pressure data of passengers, with an accuracy of over 95% for the three common intentions of lying down, sitting up, and standing up. The wheelchair can adjust its posture based on the recognition results. By adjusting the wheelchair posture through this method, users do not need to wear additional equipment and are less affected by the external environment. The target function can be achieved with simple learning, which has good human–machine collaboration and can solve the problem of some people having difficulty adjusting the wheelchair posture independently during wheelchair use. Full article

We have developed a photo-mobile polymer film, that combines organic and inorganic materials, to allow for controlled motion that can be triggered by light or heat. Our film is made using recycled quartz and consists of two layers: a multi-acrylate polymer layer and a layer containing oxidized 4-amino-phenol and N-Vinyl-1-Pyrrolidinone. The use of quartz in our film also gives it a high temperature resistance of at least 350 °C. When exposed to heat, the film moves in a direction that is independent of the heat source, due to its asymmetrical design. Once the heat source is removed, the film returns to its original position. ATR-FTIR measurements confirm this asymmetrical configuration. This technology may have potential applications in energy harvesting, due to the piezoelectric properties of quartz. Full article

The agile locomotion of adhesive animals is mainly attributed to their sophisticated hierarchical feet and reversible adhesion motility. Their structure–function relationship is an urgent issue to be solved to understand biologic adhesive systems and the design of bionic applications. In this study, the reversible adhesion/release behavior and structural properties of gecko toes were investigated, and a hierarchical adhesive bionic toe (bio-toe) consisting of an upper elastic actuator as the supporting/driving layer and lower bionic lamellae (bio-lamellae) as the adhesive layer was designed, which can adhere to and release from targets reversibly when driven by bi-directional pressure. A mathematical model of the nonlinear deformation and a finite element model of the adhesive contact of the bio-toe were developed. Meanwhile, combined with experimental tests, the effects of the structure and actuation on the adhesive behavior and mechanical properties of the bio-toe were investigated. The research found that (1) the bending curvature of the bio-toe, which is approximately linear with pressure, enables the bio-toe to adapt to a wide range of objects controllably; (2) the tabular bio-lamella could achieve a contact rate of 60% with a low squeeze contact of less than 0.5 N despite a ±10° tilt in contact posture; (3) the upward bending of the bio-toe under negative pressure provided sufficient rebounding force for a 100% success rate of release; (4) the ratio of shear adhesion force to preload of the bio-toe with tabular bio-lamellae reaches approximately 12, which is higher than that of most existing adhesion units and frictional gripping units. The bio-toe shows good adaptability, load capacity, and reversibility of adhesion when applied as the basic adhesive unit in a robot gripper and wall-climbing robot. Finally, the proposed reversible adhesive bio-toe with a hierarchical structure has great potential for application in space, defense, industry, and daily life. Full article

In this work, we study the light-induced changes of the rotational speed of a thin photomobile film using a single-axis acoustic levitator operating at 40 kHz. In our experiments, a 50 μm thick photomobile polymer film (PMP) is placed in one of the nodes of a stationary acoustic field. Under the action of the field, the film remains suspended in air. By externally perturbing this stable equilibrium condition, the film begins to rotate with its natural frequency. The rotations are detected in real time by monitoring the light of a low power He–Ne laser impinging on and reflected by the film itself. During the rotational motion, an external laser source is used to illuminate the PMP film; as a consequence, the film bends and the rotational speed changes by about 20 Hz. This kind of contactless long-distance interaction is an ideal platform for the development and study of many electro-optics devices in microgravity and low-friction conditions. In particular, we believe that this technology could find applications in research fields such as 3D dynamic displays and aerospace applications. Full article