Search

The effect of adding texture to increase the deformation of a bilayer actuator by a factor of over 100 was demonstrated. A bilayer actuator is driven by the difference in thermal deformation. Therefore, two films or plates with a large difference in thermal expansion coefficient are required. The newly developed textured film actuator (TFA) obtained large deformation even in a case involving a combination of two films with a small difference in thermal expansion coefficient. The TFA was fabricated by transferring the texture when laminating two PI films with different coefficients of thermal expansion. A TFA with thin‐film electrodes was heated by applying electric power. Thereby, it unfolded from a curled state. The maximum generated force and curvature of the TFA were 7.4 mN and 0.19 mm−1, respectively, at 0.38 W. The manufacturing process for the TFA is simple and convenient, as it does not require adhesives or special materials. In thermal drive bilayer actuator fabrication, the range of material selection is expanded substantially. In addition, large deformations are generated with less energy. Therefore, the energy consumption is likely to be reduced. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Rehabilitation devices for passive exercise have been actively researched and developed in accordance with Japan's aging society. A previous study proposed and tested an extension-type flexible pneumatic actuator (EFPA) with reinforced stiffness that could achieve passive exercise in patients. In addition, a rehabilitation device for shoulder joints with an embedded controller and small valves was proposed and tested. Joints such as the shoulder and scapula were subjected to passive exercise utilizing the tested device. However, it is difficult for patients with contractions to perform the same exercise because the reinforced EFPA can buckle. Here, to realize an EFPA with a higher stiffness, a flexible actuator in the shape of a hexagonal pyramid is proposed and tested. The hexagonal pyramid shape of a flexible actuator has a high stiffness in the direction of motion and flexibility in other directions; hereafter, this characteristic is called anisotropic stiffness. The characteristics of the hexagonal pyramid shape of the EFPA are described and compared with those of a previously reinforced EFPA. An analytical model was proposed to predict and design the shape of the hexagonal pyramid EFPA. The validity of the model is also described. [ABSTRACT FROM AUTHOR]

This study proposes an adaptive sliding‐mode control strategy based on trajectory re‐planning for a permanent magnet spherical actuator (PMSA) to address the large overshoot caused by substantial initial error while maintaining tracking precision. The proposed re‐planning technique reconstructs a local trajectory without the preceding knowledge of the desired position in the future, which makes this technique more suitable for reconstructing trajectory given online. First, a re‐planning cool‐down term is added to maximize the capability of controller to improve the precision and speed of tracking. Moreover, a smooth switching technique is also applied to further improve the precision of trajectory tracking and stop redundant re‐planning when the system enters satisfactory state. Finally, the proposed trajectory re‐planning strategy is combined with a robust adaptive sliding‐mode controller (RASC), which effectively reduces friction, delay, and external uncertainty disturbances. The effectiveness of the proposed control design is verified by both simulation and experiment on PMSA, which can provide reference for the further engineering application of multi‐degree‐of‐freedom system. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

A shearing‐motion‐type microelectromechanical system (MEMS) tactile display mechanism was fabricated to provide a shear vibration stimulus to the fingertip. It consisted of shrinking shape memory alloy (SMA) thick‐film actuators and a supporting coil spring array. The SMA actuator array was designed and fabricated using a flash‐evaporated SMA film (10 μm thick) on a mirror‐polished Cu substrate. The coil spring was successfully arrayed on a glass substrate with an SU‐8 circular array pattern. The glass substrate with the coils was bonded to the SMA substrate to complete the shearing‐motion mechanism. During the bonding process, the SMA actuators were initially elongated by the coil springs. The generated amplitude and force of the fabricated mechanism were characterized when the SMA actuator was heated by applying a pulsed current to be shrank by the shape recovery effect. The fabricated shearing‐motion mechanism successfully generated large amplitude of 41 μm (around 80 μm in reciprocal motion) and force of 22 mN at a driving frequency of 1 Hz. At 20 Hz, an amplitude of 23 μm and force of 10 mN were obtained even though they were reduced owing to the low thermal response. At both driving frequencies, the obtained amplitudes and forces seems to be sufficient for tactile stimulation to finger skin. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Because of the elderly society in Japan, a passive exercise device that can be used in homes or hospitals without assistance is desirable. In the device, a soft actuator that can move with both longer strokes and a larger force is useful. In the previous study, a pneumatic linear stepping actuator (PLSA) that can push and pull a flexible rod while changing the gripping position of a tube was developed. In this study, a variable step type PLSA is proposed and tested. Moreover, the development of a passive exercise device for the hip joint using three PLSAs and one connecter connected with three flexible rods and a knee supporter is described. The tracking position control of the knee supporter based on an analytical model is also described. The control system using developed actuators is also introduced. [ABSTRACT FROM AUTHOR]

Asymmetric vibration‐based haptic devices are being developed to apply to various applications such as navigation systems. A mobile‐type three‐dimensional haptic device requires a compact structure. Then, we focused on a three‐degree‐of‐freedom oscillatory actuator (3‐DOFOA). However, conventional 3‐DOFOAs are large in size and weight because they need a large and complicated support mechanism on the outside of the magnetic circuit. Furthermore, they do not satisfy both the requirement of similar force characteristics in each axis and no interference. To address these issues, we propose a novel 3‐DOFOA integrated with a support mechanism that has equal static characteristics in each axis without interference. The proposed structure and operating principle are described in detail in this paper, as well as the force, frequency characteristics, and acceleration responses. As these results, it can be concluded that the proposed actuator is suitable for use as a haptic device. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Multi‐degree‐of‐freedom (multi‐DOF) spherical actuators have been developed for the fields of robotics and industrial machineries. We have proposed an outer rotor type three‐DOF spherical actuator that can realize a high torque density. Each coil input current is calculated using a torque generating equation based on the torque constant matrix. The permanent magnet type actuators have a problem with generating unexpected cogging torque due to various manufacturing errors. Manufacturing errors mainly mean differences between the ideal dimensions at the motor design stage and the actual dimensions in mass production. In this case, the actuator would exceed the limitations of classical proportional‐integral‐differential (PID) controllers. Therefore, we propose a current compensator using reinforcement learning by introducing a deep neural network that is expected to improve the robustness of spherical actuators. This current compensator was applied to uncertainty problems such as manufacturing fluctuations of cogging torque. We examined the reward, which is the main parameter of deep reinforcement learning, and reduced the control error compared to classical PID controller and simple neural network (NN) controller. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In recent years, many large structures have been constructed all over the world due to economic development. Especially in Japan, more than 50 years have passed since the intensive construction of large structures during the period of high growth known as the Japanese economic miracle. As these structures age, they need to be inspected, and numerous robots have been proposed for structural inspection. However, the technology for inspection of large structures by robots remains immature. This paper proposes a vibration actuator system that can move a robot over an iron structure having a complicated surface, such as a stepped surface. A prototype vibration actuator system was built, in which four vibration actuators and wheels containing magnets were combined with flexible silicone rubber “backbone.” Actual climbing tests showed that this actuator system can move smoothly over vertical steps. Further, this system can be equipped with an automatic tapping device, which might allow it to inspect the main towers of a large bridge. [ABSTRACT FROM AUTHOR]

This article develops a novel path‐following control strategy for underactuated unmanned surface vehicle (USV) subject to unmodeled dynamics and unknown multiple disturbance. A practical robust path‐following controller is proposed using trajectory linearization control (TLC) technology, neural network, and auxiliary design system. First, the greatest advantage of this article is that the TLC technology is first introduced into the field of USV motion control, which provides a new direction for TLC technology research. Second, the underactuated model based on a transformation of the USV kinematics to Serret‐Frenet frame is simplified by introducing a nonlinear coordinate transformation. Meanwhile, to improve the robustness and reduce the computational complexity, radial basis function neural network is replaced by neural network with minimum learning parameter method to compensate for unmodeled dynamics and unknown multiple disturbance. In addition, an auxiliary dynamic system is used to reduce the risk of actuator saturation. The stability of the whole system was proved based on the Lyapunov criteria. Finally, the comparison results demonstrate the superior performance of the proposed approach. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper is concerned with the design of a robust, state-feedback, delay-dependent H∞ controller for an active vibration control of seismic-excited structural systems having actuator delay, norm bounded uncertainties, and L2 disturbances. The norm bounded uncertainties are assumed to exist in variations of structural stiffness and damping coefficients. Based on the selection of Lyapunov-Krasovskii functional, first a bounded real lemma (BRL) is obtained in terms of linear matrix inequalities (LMI5) such that the nominal, time-delay system is guaranteed to be globally asymptotically stable with minimum allowable disturbance attenuation level. Extending BRL, sufficient delay-dependent crite,ia are developed for a stabilizing H∞ controller synthesis involving a matrix inequality for which a nonlinear optimization algorithm with LMIs is proposed to get feasible solution to the problem. Moreover, for the case of existence of norm-bounded uncertainties, both the BRL and H∞ stabilization criteria are easily extended by employing a wellknown bounding technique. Then, a cone complementary algorithm is also utilized to solve the nonconvex optimization problem. By use of the proposed method, a suboptimal controller with maximum allowable delay bound, uncertainty bound and minimum allowable disturbance attenuation level can be easily obtained by solving the proposed convex optimization technique. A four-degree-of-freedom uncertain structural system subject to seismic excitations is used to illustrate the effectiveness of the approach through simulations. Simulation results, obtained by using real time-history data of Kobe and Kocaeli earthquakes show that the proposed controller is very effective in reducing vibration amplitudes of storeys and guarantees stability at maximum actuator delay and parametric uncertainty bound. [ABSTRACT FROM AUTHOR]

In recent years, mixed or/and augmented reality, which aims to integrate virtual space with real space, has received a significant amount of attention in research and development. In particular, the concept of a tangible interface is an interesting research area in this growing field of study. This article develops and evaluates a tangible terrain representation system (TTRS), a tangible interface that recognizes the terrain in three dimensions and provides a more efficient approach to highway route planning and design. The developed system represents a terrain surface by controlling the shape of a stretchable screen using 64 actuators (8 × 8) and by projecting an aerial photograph on a screen. In applying TTRS to highway route planning, the user establishes control points using a magnetic positioning device and projects the image of a highway alignment on the TTRS. The developed system was evaluated by comparing its usability to an alternative system (virtual reality-based visual three-dimensional representation) using a group of evaluators at Miyagi University, Japan. The article concludes that TTRS is an effective tool for terrain representation and highway route planning and design. [ABSTRACT FROM AUTHOR]

Abstract: The harsh environment in the ITER device presents many diagnostic challenges. A proposed design engineered at the Japan Atomic Energy Agency (JAEA) is of an optical alignment system installed on mirrors behind double vacuum windows. Due to the harsh environment, a piezo-motor is used as an actuator and a sliding bearing is used as a pivot. The required torque of the actuator is estimated. Trial results indicate that the actuator as described fulfills requirements. A prototype of a key optical component, the micro-retro-reflector array, is produced through the electro-forming method. Measured reflectivity yields a sufficient signal for in situ calibration. A Cassegrain telescope prototype is designed and produced using simple spherical mirrors and achromatic lenses made of silica and CaF2. The measured focal length concurs with design objectives. Irradiation tests are necessary to verify the capabilities of these optical devices. [Copyright &y& Elsevier]

A low-pressure rotary-type air motor is suitable to use for a wall-climbing robot, as it has good performances and lightweight and so on. The prototype of the low-pressure air motor has been developed in Miyazaki University, Japan. It is mainly composed of a pair of impellers and the corresponding casings, a switching valve and a shaft. The two impeller-casing pairs are designed to drive the motor shaft to turn in opposite directions. The input airflow is derived with the switching valve to drive one of the two impellers, and thus by alternating the valve position the rotational direction of the air motor shaft can be reversed. This paper presents the mechanism, the static and dynamic characteristics of the air motor, as well as the velocity and position controls in actuating systems. [Copyright &y& Elsevier]

Reports that Tokyo University of Agriculture and Technology in Japan sees wide potential for displays and actuators from its process of getting planar light and ultrasonic emissions out of nanocrystaline silicon. Treatment of polysilicon with anodic oxidation to make crystals; Concept of the anodization process.

Evaluates an acoustical patent for control apparatus for vibration type actuator, manufactured by Canon Kabushiki Kaisha and filed in Japan on December 28, 2000. Description of several control circuits for piezoelectric traveling-wave-type actuators.