Woven Fabric Muscle for Soft Wearable Robotic Application Using Two-Dimensional Zigzag Shape Memory Alloy Actuator.

In this study, we propose a fabric muscle based on the Zigzag Shape Memory Alloy (ZSMA) actuator. Soft wearable robots have been gaining attention due to their flexibility and the ability to provide significant power support to the user without hindering their movement and mobility. There has been an increasing focus on the research and development of fabric muscles, which are crucial components of these robots. This article introduces a high-performance fabric muscle utilizing zigzag-shaped shape memory alloy (SMA), ZSMA, a new form of SMA actuator. Through modeling and experimentation of the ZSMA actuator, we identified an optimized actuator design and detailed the fabric muscle fabrication process. The proposed fabric actuator, weighing only 7.5 g, demonstrated the impressive capability to lift a weight of 2 kg with a contraction displacement of 40%. This significant achievement paves the way for future research possibilities in soft wearable robotics.

Design and Control of Lightweight Bionic Arm Driven by Soft Twisted and Coiled Artificial Muscles.

Twisted and coiled actuators (TCAs), which are light but capable of producing significant power, were developed in recent times. After their introduction, there have been numerous improvements in performance, including development of techniques such as actuation strain and heating methods. However, the development of robots using TCA is still in its early stages. In this study, a bionic arm driven by TCAs was developed for light and flexible operation. The aim of this study was to gain a foothold in the future of robot development using TCA, which is considered as the appropriate artificial muscle. The main developments were with regard to the design (from actuator design to system design), system configuration for control, and control method. First, a process technology for repeatedly manufacturing TCA, which can be used practically and delivers sufficient performance, was developed. Based on the developed actuator, a joint was designed to move the elbow and hand. The final bionic arm was developed by integrating the TCA, pulley joint, and control system. It moved the elbow up to 100° and allowed the hand to move in three degrees of freedom. Using the control method for each joint, we were able to show the movement by using the hand and elbow.

Shape Estimation of Soft Manipulator Using Stretchable Sensor.

The soft robot manipulator is attracting attention in the surgical fields with its intrinsic softness, lightness in its weight, and safety toward the human organ. However, it cannot be used widely because of its difficulty of control. To control a soft robot manipulator accurately, shape sensing is essential. This paper presents a method of estimating the shape of a soft robot manipulator by using a skin-type stretchable sensor composed of a multiwalled carbon nanotube (MWCNT) and silicone (p7670). The sensor can be easily fabricated and applied by simply attaching it to the surface of the soft manipulator. In its fabrication, MWCNT is sprayed on a teflon sheet, and liquid-state silicone is poured on it. After curing, we turn it over and cover it with another silicone layer. The sensor is fabricated with a sandwich structure to decrease the hysteresis of the sensor. After calibration and determining the relationship between the resistance of the sensor and the strain, three sensors are attached at 120° intervals. Using the obtained data, the curvature of the manipulator is calculated, and the entire shape is reconstructed. To validate its accuracy, the estimated shape is compared with the camera data. We experiment with three, six, and nine sensors attached, and the result of the error of shape estimation is compared. As a result, the minimum tip position error is approximately 8.9 mm, which corresponded to 4.45% of the total length of the manipulator when using nine sensors.