The electrical contact impedance at stiff interfaces is essential to the development of touch sensors for in-situ force and pressure measurements. This work examines systematically the relationship between the electrical contact impedance and the applied normal contact load between two spheres of silicon carbide. Through the combination of numerical simulations and experimental measurements, we meaningfully locate the linearity between the electrical contact impedance and the contact load, for various measurement conditions. Results indicate that the electrical contact impedance, for slight normal compression, is strongly affected by voltage amplitude, measurement time, and the generally existing surface roughness at the submicron scale, presenting significant nonlinearity and nonrepeatability. However, these dependencies vanish as the normal compression increases. This study advances our understanding of electro-mechanical mechanisms at conductive interfaces, providing insights into the development of touch sensors for in-situ force and pressure measurements.

The output performance of stick-slip piezoelectric actuators is comprehensively determined by the electro-mechanical responses of the driving unit, control strategy, and the contact status between the driving unit and the slider. Most previously developed inertial piezoelectric actuators face the problems of frequency dependence, motion speed, excessive volume, step resolution as well as loading capacity. To exhaustively improve actuation performance while maintaining low power consumption, we propose a compact bi-directional piezoelectric-based rotary actuator incorporating the rhombic amplification mechanism, adjustable preload, and simulation method based on by LuGre friction model for comparison. A prototype is fabricated and examined, which accomplishes the maximum load torques of 27.78 and 30.87 Nmm in clockwise and anticlockwise directions, respectively, at the highest rotational velocity of 0.4720 rad/s, which is almost equal in two directions. Compared with previously reported inertial actuators, the performance of the proposed actuator is significantly enhanced, promising in applications requiring nanometer resolution, long stroke, large holding and driving forces.

Atomic magnetometers are among the most sensitive technologies for detecting and characterizing magnetic fields, making them ideal for many applications. A compact atomic magnetometer utilizes a built-in laser diode to generate light at the specified frequency. The stability of the diode significantly affects the sensor’s performance. This paper proposes a novel method of stabilizing the laser diode output by a regulated double feedbacks control setting. The control coefficients are regulated dynamically according to the operating state of the atomic magnetometer. The method does not need any additional component and performs better than the conventional approach in a long-time operation. A compact atomic magnetometer with sensitivity 14 fT/Hz1/2 @10 Hz is developed and tested, which demonstrates the feasibility of the proposed method.

The detection of small defects that are buried in ferromagnetic steel is still a challenging problem for electromagnetic non-destructive testing. This paper presents a probe with high-resolution high-sensitivity tunneling magnetoresistance (TMR) sensors for buried defects inspection. The operation principle of the probe is based on eddy current testing (ECT) and magnetic flux leakage effects, which does not need a strong magnetic field to saturately magnetize the sample. The excitation frequency is optimized, in which way the eddy current field can penetrate through the sample. Experimental results show that the probe can detect a defect with dimensions of 5 mm (length)* 1 mm (width)* 1 mm (depth) buried in a 3 mm thick carbon steel plate. The proposed probe can be widely used for ferromagnetic materials inspection.

This paper proposes a new multi-degree-of-freedom (DOF) vibration system using electropermanent magnet (EPM) to achieve wide band frequency response of the system. A five-DOF system with four EPMs can operate with 16 different frequency response curves. Numerical calculation reveals that the proposed system significantly broadens its operational range by using the MAX function.

The lift-off effect is a main challenge for the eddy current testing (ECT)-based rail detections. The non-coaxial transmitter-receiver (TR) probes are considered as promising structures, however, the research focused on the transmitter-receiver coil distance optimization is limited. In this study, this coil distance is optimized for the Tx-Rx probe with varying lift-offs in rail inspections. Analytical simulations under different conditions show that the optimized coil distance can reduce the lift-off effect. The proposed method provides an optimization method for coil parameter design.

This paper compares 6-phase switched reluctance motors (SRMs) with 24 stator slots. A 24-slot-20-pole (24/20) SRM has a small torque ripple compared with a conventional 24/16 3-phase SRM. However, the iron loss of a 24/20 SRM is larger than that of a 24/16 SRM because the number of rotor poles is large. In order to decrease the iron loss of a 6-phase SRM, 24/14 and 24/10 SRMs are firstly proposed in this paper. Next, the torque and iron loss characteristics of these 6-phase SRMs are compared. Finally, the effectiveness of the proposed 24/14 and 24/10 SRMs are discussed.

Electrical and mechanical energy type converts around the nature. Among electromechanical coupling effects and materials, electrets are widely applied on microphones, earphones, and air filters. Stretchable electrets have been developed with elastomeric bases and nano-particle electrets to behave its mechanical stretchability and electrical activity simultaneously, and its electromechanical properties has been expanded on multiple applications such as mechanical sensing, energy harvesting and actuation. The electromechanical coupling properties of this energy-active material are analyzed in this work by four types of mechanical procedures: compression, vertical motion, stretch extension, and vertical pricking between electrode setup. It is found that the vertical pricking onto electret films induces ultra-high effective piezoelectric coefficients according to its mechanical-induced deformations. The electromechanical applications of mechanical sensing, energy harvesting and actuation with this mechanical procedure are demonstrated with this pricking type, showing its advantages of electromechanical coupling capabilities.

This paper proposes a new method of pulsed eddy current thickness measurement based on a new characteristic quantity to address the problem that the pulsed eddy current detection signal can be affected by lift-off, resulting in inaccurate thickness measurements. Firstly, the principle of pulsed eddy current detection is introduced, the simulation model of Tx-Rx (Transmitter-Receiver) sensor is established, the differential signal characteristics of ferromagnetic materials are studied, and the relationship between the time and amplitude of the gradient minima time and the lift-off is discussed. Secondly, an experimental system is built and it is found that the gradient minima time is less affected by the lift-off and increases with the thickness of the differential specimen. Finally, a method of thickness measurement of ferromagnetic materials based on gradient minima is proposed.

In this study, we evaluated the magnetic properties of ring-shaped laminated cores manufactured by laser machining, which are used in prototype motor development. As a result, it was found that the magnetic properties of the specimens manufactured by laser machining were degraded due to the distortion of the B-H loop caused by the thermal stress generated during the machining process. It was also found that hysteresis loss increased by about 113% when the excitation frequency was 50 Hz and the magnetic flux density was 1.0 T.

An active seat suspension was proposed to improve ride comfort of the ultra-compact vehicle. Discomfort vibration for vehicle occupants was reduced by active control of the seat suspension. In this study, a control system that directly feedback the absolute acceleration measured on the seat was proposed. To investigate the performance of vibration control, vibration response of this control system was measured using the experimental apparatus assumed the active seat suspension. In acceleration feedback control, improving the ride comfort by selecting proper feedback gain because characteristics of frequency was changed by gain.

Obtaining real-time force and displacement states of piezoelectric actuators is a necessary condition for accurate control. Self-sensing methods that utilize the piezoelectric actuator itself as the sensor have attracted much attention due to low cost and portability. However, researches on the self-sensing of piezoelectric actuators mostly focuses on phenomenological models, and reports on fundamental physics are infrequent. In this work, theoretical calculations and experimental measurements were combined to expose the physical mechanism of self-sensing. Taking the widely used barium titanate (BaTiO3) piezoelectric materials as an example, the influence of intrinsic and extrinsic contributions on the capacitance under mechanical-electrical coupling were systematically studied. The data obtained from material and electrical characterizations were used to quantify the contributions of various parts in piezoelectric materials to capacitance, and the obtained theoretical formula is in good agreement with experimental measurements. This study will further promote the applications of self-sensing in piezoelectric actuators.

There are many situations in the operation of mechanical products that require linear motion. In most cases, the conversion from rotational to linear motion is performed through various mechanisms. However, there is concern that such a method may be subject to the mechanical effects of each mechanism. Although there are some cases in which the motion pattern can be varied by installing a variable mechanism, such mechanisms are rarely used in general products because they complicate the system. Therefore, our laboratory has been continuously studying linear actuators that enable high-speed and high-precision linear motion. In this report, a linear actuator with a dual Halbach array of permanent magnets in the stator was designed to further improve the thrust of the linear actuator. The effect of the geometry of the permanent magnets on the thrust characteristics was investigated using electromagnetic field analysis based on the finite element method.

Hybrid vehicles have multiple power sources and are energy efficient; this improves both their fuel efficiency and dynamic performance. Therefore, hybrid vehicles have recently been used as competition vehicles, which require high powertrain performance. The system of hybrid vehicle consists of two power resources: an internal combustion engine and motor, each of which requires precise control. Controlling the output of an internal combustion engine is difficult. In this study, the dynamic response of an actuator to an electronic throttle system is investigated. The experimental results indicate that the optimized parameters improve the dynamic response.

Linear motion in a machine is converted from rotational motion by the mechanism. The performance of linear motion by a mechanism depends on the geometry of the mechanism. In addition, energy loss occurs by using mechanisms. However, by replacing these mechanisms with linear actuators that use Lorentz force and have a simple structure, direct drive can be realized and highly efficient linear motion can be achieved. In this study, a prototype actuator in which the magnetic flux is concentrated in the coil by the arrangement of magnets was fabricated, and the thrust characteristics in the reciprocating motion of the mover were evaluated.

In conventional elevators, vibration and cable twisting are major problems when the cable is long. Therefore, we are considering an elevator that omits the counterweight and uses a single cable with fixed ends to move the actuator. However, there are problems such as reduced efficiency due to cable contact and damage. Therefore, we propose a vertical transfer system that uses a cylindrical linear induction motor (LIM) as an actuator to move the actuator in a non-contact manner over a long uniform conductor cable. By placing the cylindrical LIM on top of a reaction plate, which is a cylindrical shell-shaped conductor, the advantage is that the magnetic force acts uniformly on the reaction plate and vibration in the gap direction is suppressed. So, we built an analytical model in which the cylindrical LIM is driven vertically and analyzed the electromagnetic field using the finite element method.

This paper deals with the design optimization of a mechanical fast switch for DC circuit breaker (DCCB) using the response surface method (RSM). The dynamic characteristics such as transient current, electromagnetic force, velocity, and movement of repulsive plate are calculated using a coupled electric circuit, magnetic, and mechanical analysis based on the finite element method (FEM). In order to verify the validity of coupled analysis model, the calculated dynamic characteristics are compared with the experimental values. Subsequently, in order to improve the action completion time of the mechanical fast switch, an optimal thomson coil model(TCA) is designed using the RSM.