A soft sensor-based three-dimensional (3-D) finger motion measurement system

In this study, a soft sensor-based three-dimensional (3-D) finger motion measurement system is proposed. The sensors, made of the soft material Ecoflex, comprise embedded microchannels filled with a conductive liquid metal (EGaln). The superior elasticity, light weight, and sensitivity of soft sensors allows them to be embedded in environments in which conventional sensors cannot. Complicated finger joints, such as the carpometacarpal (CMC) joint of the thumb are modeled to specify the location of the sensors. Algorithms to decouple the signals from soft sensors are proposed to extract the pure flexion, extension, abduction, and adduction joint angles. The performance of the proposed system and algorithms are verified by comparison with a camera-based motion capture system.ope

Review of machine learning methods in soft robotics

Soft robots have been extensively researched due to their flexible, deformable, and adaptive characteristics. However, compared to rigid robots, soft robots have issues in modeling, calibration, and control in that the innate characteristics of the soft materials can cause complex behaviors due to non-linearity and hysteresis. To overcome these limitations, recent studies have applied various approaches based on machine learning. This paper presents existing machine learning techniques in the soft robotic fields and categorizes the implementation of machine learning approaches in different soft robotic applications, which include soft sensors, soft actuators, and applications such as soft wearable robots. An analysis of the trends of different machine learning approaches with respect to different types of soft robot applications is presented; in addition to the current limitations in the research field, followed by a summary of the existing machine learning methods for soft robots

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Department of Mechanical Engineeringope

A Hybrid Gripper With Soft Material and Rigid Structures

Various robotic grippers have been developed over the past several decades for robotic manipulators. Especially, the soft grippers based on the soft pneumatic actuator (SPA) have been studied actively, since it offers more pliable bending motion, inherent compliance, and a simple morphological structure. However, few studies have focused on simultaneously improving the fingertip force and actuation speed within the specified design parameters. In this study, we developed a hybrid gripper that incorporates both soft and rigid components to improve the fingertip force and actuation speed simultaneously based on three design principles: first, the degree of bending is proportional to the ratio of the rigid structure; second, a concave chamber design is preferred for large longitudinal strain; and third, a round shape between soft and rigid materials increases the fingertip force. The suggested principles were verified using the finite element methods. The improved performance of the hybrid gripper was verified experimentally and compared with the performance of a conventional SPAs. The ability of the hybrid gripper to grasp different objects was evaluated and was applied in a teleoperated system

Development of a Sensorized Hybrid Gripper to Evaluate Grasping Quality

Various soft grippers based on the soft pneumatic actuators (SPAs) have been studied actively since it offers pliable bending motion, inherent compliance, and a simple morphological structure. For improved functionality or feedback control, embedding sensors to SPAs has also been studied vigorously. However, evaluating grasping quality of the gripper with the embedded sensor has rarely been studied even if the stable grasping is significant in robotic manipulation. Thus, in this study, we developed a sensorized hybrid gripper which embeds a commercial bending sensor and a customized tactile sensor, and the grasping quality based on the largest-minimum wrench (LMW), which evaluate the contact wrenches, was calculated. The grasping quality metrics with two different grips were compared experimentally

A Hybrid Jamming Structure Combining Granules and a Chain Structure for Robotic Applications

To allow versatile manipulation of soft robots made of compliant materials with limited force transmission, variable stiffness has been actively developed, which has become one of the most important factors in soft robotics. Variable stiffness is usually achieved by a jamming mechanism using layers, granules, or chain structures, through vacuum pressure or cable-driven mechanism due to its simple and rapid actuation. However, such jamming mechanisms are not suitable for actual robotic applications that require large supporting forces or drastic changes in stiffness. In this article, a hybrid jamming structure that combines granules and a rigid chain structure is proposed to simultaneously increase the average stiffness change in all directions and the maximum force in a certain direction. The improved performance of the proposed structure was compared to that of conventional granular and chain jamming structures. Based on the analytical model of the proposed structure, the principles for designing the hybrid jamming structure were derived and experimentally verified. Finally, based on the hybrid jamming structures, a multilink hybrid jamming structure was developed as a wearable system to assist the upper limbs and a robotic arm structure

Investigation on repeatable and consistent direct writing of eutectic gallium-indium (EGaIn) and its application to a soft sensor

In this study, direct ink writing (DIW) of eutectic gallium-indium (EGaIn) is introduced and the important process variables (PVs) are introduced and discussed. To fabricate the soft sensor in a stable manner, it was very important to ensure the flatness of the substrate. In addition, wettability of EGaIn on the substrate significantly affects the printing performance. Therefore, it is necessary to investigate the proper combination of PVs by understanding the mechanism of EGaIn DIW