A suit-type wearable robot (STWR) is a new type of soft wearable robot (SWR) that can be worn easily anywhere and anytime to assist the muscular strength of wearers because it can be worn like normal clothes and is comfortable to wear even with no power supply. This paper proposes an STWR, in which a shape-memory-alloy-based fabric muscle (SFM) is used as the actuator. The STWR, which weighs less than 1 kg, has a simple structure, with the following components: SFMs, wire encoders for measuring the contraction length of the SFMs, and BOA that fix the actuators on the forearms. In this study, a position controller for the SFM using the wire encoder was developed, and a prototype STWR was fabricated using this position controller. Moreover, by putting the STWR on a mannequin, step-response experiments were performed in which the arms of the mannequin lifted barbells weighing 2 kg and 4 kg to a certain target position. A fast response of moving to the target position in less than 1 s was observed in all steps except for the initial heating step for the 2 kg barbell. The response speed of the SFM was noticeably slower for the 4 kg barbell compared to that for the 2 kg barbell; it moved to the target position in approximately 3 s in all the steps except for the initial heating step. The SFM-applied STWR could overcome the limitations of conventional robots in terms of weight and inconvenience, thereby demonstrating the application potential of STWRs.

Two-stage oil-free centrifugal air compressors can bring significant advantages and open new market opportunities for compressor manufacturers. One of the core technologies behind this compressor type is the high-speed electrical machine supported by active magnetic bearings. In this paper, the requirements set by the compressor on the electrical machine design are presented. The design solutions aimed to satisfy these requirements are discussed. Two case studies illustrate possible design approaches for the target application with examples of a 120-kW, 60 000-r/min induction machine with a solid rotor and a 225-kW, 50 000-r/min permanent-magnet synchronous machine (PMSM) with a full cylindrical magnet. The system design and simulation results are confirmed by measurements of a PMSM prototype.

In this paper, we propose a shape memory alloy (SMA)-based wearable robot that assists the wrist motion for patients who have difficulties in manipulating the lower arm. Since SMA shows high contraction strain when it is designed as a form of coil spring shape, the proposed muscle-like actuator was designed after optimizing the spring parameters. The fabricated actuator shows a maximum force of 10 N and a maximum contraction ratio of 40%. The SMA-based wearable robot, named soft wrist assist (SWA), assists 2 degrees of freedom (DOF) wrist motions. In addition, the robot is totally flexible and weighs 151g for the wearable parts. A maximum torque of 1.32 Nm was measured for wrist flexion, and a torque of larger than 0.5 Nm was measured for the other motions. The robot showed the average range of motion (ROM) with 33.8, 30.4, 15.4, and 21.4 degrees for flexion, extension, ulnar, and radial deviation, respectively. Thanks to the soft feature of the SWA, time cost for wearing the device is shorter than 2 min as was also the case for patients when putting it on by themselves. From the experimental results, the SWA is expected to support wrist motion for diverse activities of daily living (ADL) routinely for patients.

This article proposes a shape memory alloy (SMA)-based artificial muscle that has an active cooling system. An SMA coil spring is embedded into a stretchable coolant vessel, which allows active cooling of SMA through coolant circulation. The coolant effect has been investigated by measuring actuation speed. Integrating a thermomechanical model and heat transfer model between coolant and SMA, actuation times have been estimated. Based on these results, actuation performances that use four different coolants have been found out, and the mineral oil cooling case shows both contraction and extension times of less than 1 s to contract to over 35% of its initial length with 1 kg load. A soft wearable robot for assisting wrist motion has been designed by integrating multiple SMA muscles with a glove, wristband, and elbow anchor. Thanks to the advantages of the SMA coil spring actuator, the proposed robot is compliant and weight-balanced structure. The robot shows ranges of motion of 38°, 50°, 34°, and 35°, for flexion, extension, radial deviation, and ulnar deviation, respectively. In addition, the robot shows improved cyclic performance compared to a natural air-cooling system. Finally, its torque assistance and theamount of time needed to wear it have been analyzed with user tests.

Fabric muscle is important for wearable robots that are soft, compliant, and silent with high contractility and high force. This study presents a novel shape memory alloy (SMA) spring-based fabric muscle (SFM). The SFM is manufactured by bundling SMA springs with proven performance as artificial muscle. The SFM generates high contractility and high force, and is soft, flexible, and light because it is covered with fabric used to make actual clothes. The SFM is contracted by heat and shows a contraction strain of 50% at a heating temperature of 70°C while generating 100 N force or higher. Furthermore, it generates a maximum contraction strain of 67% under no load. To drive it with the optimum voltage and current, the SFM is designed by optimizing the serial and parallel connection methods for the embedded SMA springs. We propose herein design and manufacturing methods for the SFM and verify the usability of the SFM as a soft actuator through a performance evaluation. The SFM as a soft actuator with a simple structure-like fabric is easily applicable to soft wearable robots that can support muscle power by simply being attached to usual suits. The SFM has a soft touch, and is lightweight; hence, it has the potential for wide applications to new-concept soft wearable robots that can be comfortably worn anytime and anywhere like usual clothes.