A 3D Printed Modular Soft Gripper Integrated With Metamaterials for Conformal Grasping

A single universal robotic gripper with the capacity to fulfill a wide variety of gripping and grasping tasks has always been desirable. A three-dimensional (3D) printed modular soft gripper with highly conformal soft fingers that are composed of positive pressure soft pneumatic actuators along with a mechanical metamaterial was developed. The fingers of the soft gripper along with the mechanical metamaterial, which integrates a soft auxetic structure and compliant ribs, was 3D printed in a single step, without requiring support material and postprocessing, using a low-cost and open-source fused deposition modeling (FDM) 3D printer that employs a commercially available thermoplastic poly (urethane) (TPU). The soft fingers of the gripper were optimized using finite element modeling (FEM). The FE simulations accurately predicted the behavior and performance of the fingers in terms of deformation and tip force. Also, FEM was used to predict the contact behavior of the mechanical metamaterial to prove that it highly decreases the contact pressure by increasing the contact area between the soft fingers and the grasped objects and thus proving its effectiveness in enhancing the grasping performance of the gripper. The contact pressure can be decreased by up to 8.5 times with the implementation of the mechanical metamaterial. The configuration of the highly conformal gripper can be easily modulated by changing the number of fingers attached to its base to tailor it for specific manipulation tasks. Two-dimensional (2D) and 3D grasping experiments were conducted to assess the grasping performance of the soft modular gripper and to prove that the inclusion of the metamaterial increases its conformability and reduces the out-of-plane deformations of the soft monolithic fingers upon grasping different objects and consequently, resulting in the gripper in three different configurations including two, three and four-finger configurations successfully grasping a wide variety of objects.

A Dynamic Modeling Method for the Bi-Directional Pneumatic Actuator Using Dynamic Equilibrium Equation

Dynamic modeling of soft pneumatic actuators are a challenging research field. In this paper, a dynamic modeling method used for a bi-directionaly soft pneumatic actuator with symmetrical chambers is proposed. In this dynamic model, the effect of uninflated rubber block on bending deformation is considered. The errors resulting from the proposed dynamic equilibrium equation are analyzed, and a compensation method for the dynamic equilibrium equation is proposed. The equation can be solved quickly after simplification. The results show that the proposed dynamic model can describe the motion process of the bi-directional pneumatic actuator effectively.

Development of Wrist Rehabilitation Device Using Extension Type Flexible Pneumatic Actuators with Simple 3D Coordinate Measuring System

Rehabilitation devices have been developed to assist patients recover from physical disabilities by using specific devices to do an exercise, training and therapy. The purpose of this study is to develop a home-based rehabilitation device which is safe to use and without requirement of person-in-charge. In this study, a simple home-based wrist rehabilitation device which can give passive exercise on spherical orbit while patients hold its handles is proposed and tested. The device has two moving handling stage driven by 6 extension type flexible pneumatic actuators (“EFPA” for short) on two hemispherical acrylic domes. The device can give passive exercise for the upper limb by changing the relative position of the patient’s hands. In this paper, the construction and operating principle of the tested device are described. A low-cost 3-dimentional coordinate measuring system using two wire-type linear potentiometers to control the position of the holding stages is also described. In addition, the tracking position control of the holding handles on sphere is carried out. As a result, it can be found that the handling stage of the tested device can trace the desired orbit based on the coordinates measured from 3-dimentional coordinate measuring system. It can be confirmed that the tested wrist rehabilitation device has a possibility to apply passive movements to the wrist along desired orbit while patients hold its handles.

Biomimetic Artificial Joints Based on Multi-Material Pneumatic Actuators Developed for Soft Robotic Finger Application

To precisely achieve a series of daily finger bending motions, a soft robotic finger corresponding to the anatomical range of each joint was designed in this study with multi-material pneumatic actuators. The actuator as a biomimetic artificial joint was developed on the basis of two composite materials of different shear modules, and the pneumatic bellows as expansion parts was restricted by frame that made from polydimethylsiloxane (PDMS). A simplified mathematical model was used for the bending mechanism description and provides guidance for the multi-material pneumatic actuator fabrication (e.g., stiffness and thickness) and structural design (e.g., cross length and chamber radius), as well as the control parameter optimization (e.g., the air pressure supply). An actuation pressure of over 70 kPa is required by the developed soft robotic finger to provide a full motion range (MCP = 36°, PIP = 114°, and DIP = 75°) for finger action mimicking. In conclusion, a multi-material pneumatic actuator was designed and developed for soft robotic finger application and theoretically and experimentally demonstrated its feasibility in finger action mimicking. This study explored the mechanical properties of the actuator and could provide evidence-based technical parameters for pneumatic robotic finger design and precise control of its dynamic air pressure dosages in mimicking actions. Thereby, the conclusion was supported by the results theoretically and experimentally, which also aligns with our aim to design and develop a multi-material pneumatic actuator as a biomimetic artificial joint for soft robotic finger application.

Al2O3/WS2 Surface Layers Produced on the Basis of Aluminum Alloys for Applications in Oil-Free Kinematic Systems

The article presents the results of an aluminum oxide layer doped with monolayer 2H tungsten disulphide (Al2O3/WS2) for applications in oil-free kinematic systems. The results concern the test carried out on the pneumatic actuator operational test stand, which is the actual pneumatic system with electromagnetic control. The cylinders of actuators are made of Ø 40 mm aluminum tube of EN-AW-6063 aluminum alloy which is used in the manufacture of commercial air cylinder actuators. The inner surfaces of the cylinder surfaces were covered with an Al2O3/WS2 oxide layer obtained by anodic oxidation in a three-component electrolyte and in the same electrolyte with the addition of tungsten disulfide 2H-WS2. The layers of Al2O3 and Al2O3/WS2 obtained on the inner surface of the pneumatic actuators were combined with a piston ring made of polytetrafluoroethylene with carbon (T5W) material and piston seals made of polyurethane (PU). The cooperation occurred in the conditions of technically dry friction. After the test was carried out, the scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) analysis of the surface of the cylinder bearing surfaces and piston seals of the pneumatic cylinders was performed. The analysis revealed the formation of a sliding film on the cylinder surface modified with tungsten disulfide, as well as on the surface of wiper seals. Based on the SEM/EDSM tests, it was also found that the modification of the Al2O3 layer with tungsten disulfide contributed to the formation of a sliding film with the presence of WS2 lubricant, which translated into smooth cylinder operation during 180 h of actuator operation. The cylinder with the unmodified layer showed irregular operation after approximately 70 h thereof.

Experimental Stand for Sorting Components Dismantled from Printed Circuit Boards

There is nothing new about the fact that higher concentrations (up to 50 times) of valuable materials can be found in e-waste, compared to mined ores. Moreover, the constant accumulation of excessive amounts of waste equipment has a negative impact on the environment. The components found in electronic equipment may contain hazardous materials or materials that could be recycled and reintroduced into production processes, thus reducing the carbon footprint created by waste electrical and electronics equipment (WEEE). Sustainable e-waste recycling requires high-value, integrated recovery systems. By implementing a two-stage experimental sorting stand, this paper proposes an efficient and fast sorting method that can be industrially scaled up to reduce the time, energy and costs needed to sort electronic waste (e-waste). The sorting equipment is in fact an ensemble of sensors consisting of cameras, color sensors, proximity sensors, metal detectors and a hyperspectral camera. The first stage of the system sorts the components based on the materials’ spectral signature by using hyperspectral image (HSI) processing and, with the help of a robotic arm, removes the marked components from the conveyor belt. The second stage of the sorting stand uses a contour vision camera to detect specific shapes of the components to be sorted with the help of pneumatic actuators. The experimental sorting stand is able to distinguish up to five types of components with an efficiency of 89%.

Data-driven geometric system identification for shape-underactuated dissipative systems

Systems whose movement is highly dissipative provide an opportunity to both identify models easily and quickly optimize motions. Geometric mechanics provides means for reduction of the dynamics by environmental homogeneity, while the dissipative nature minimizes the role of second order (inertial) features in the dynamics. Here we extend the tools of geometric system identification to ``Shape-Underactuated Dissipative Systems (SUDS)'' -- systems whose motions are more dissipative than inertial, but whose actuation is restricted to a subset of the body shape coordinates. Many animal motions are SUDS, including micro-swimmers such as nematodes and flagellated bacteria, and granular locomotors such as snakes and lizards. Many soft robots are also SUDS, particularly those robots using highly damped series elastic actuators. Whether involved in locomotion or manipulation, these robots are often used to interface less rigidly with the environment. We motivate the use of SUDS models, and validate their ability to predict motion of a variety of simulated viscous swimming platforms. For a large class of SUDS, we show how the shape velocity actuation inputs can be directly converted into torque inputs suggesting that systems with soft pneumatic actuators or dielectric elastomers can be modeled with the tools presented. Based on fundamental assumptions in the physics, we show how our model complexity scales linearly with the number of passive shape coordinates. This offers a large reduction on the number of trials needed to identify the system model from experimental data, and may reduce overfitting. The sample efficiency of our method suggests its use in modeling, control, and optimization in robotics, and as a tool for the study of organismal motion in friction dominated regimes.

A Procedure for the Fatigue Life Prediction of Straight Fibers Pneumatic Muscles

Different from the McKibben pneumatic muscle actuator, the straight fibers one is made of an elastomeric tube closed at the two ends by two heads that ensure a mechanical and pneumatic seal. High stiffness threads are placed longitudinally into the wall of the tube while external rings are placed at some sections of it to limit the radial expansion of the tube. The inner pressure in the tube causes shortening of the actuator. The working mode of the muscle actuator requires a series of critical repeated contractions and extensions that cause it to rupture. The fatigue life duration of a pneumatic muscle is often lower than traditional pneumatic actuators. The paper presents a procedure for the fatigue life prediction of a straight-fibers muscle based on experimental tests directly carried out with the muscles instead of with specimens of the silicone rubber material which the muscle is made of. The proposed procedure was experimentally validated. Although the procedure is based on fatigue life duration data for silicone rubber, it can be extended to all straight-fibers muscles once the fatigue life duration data of any material considered for the muscles is known.

Jumping robot: A pneumatic jumping locomotion across rough terrain

This paper presents a jumping mechanism using pneumatic actuators adopted in a traditional robotic vehicle’s frame. This is a skeleton for future development on this technology. This is a simple mechanism to overcome obstacles on its way in a robotic vehicle. As we know a traditional wheeled robotic vehicle can not over come an obstacle on ease as it doesn’t have an effective mechanism or it might take an other alternative long route to reach the target. This mechanism has an effective design to overcome obstacles comparing to the traditional robot vehicles. So this model has a higher mobility, flexibility and rapidity. This design has a new type of locomotion to it that is jumping along with wheeled movement which is not present in a traditional robot. This mechanism works from the real time information from the sensors. There are 4 double acting cylinders placed at equidistant from each other and mass distribution of the whole model has been equally divided and each cylinder has the same load. These 4 cylinders are pneumatically actuated as compressed air as source. When these cylinders are actuated there is rapid pressurizing which causes the jump. These cylinders are actuated when the relay receives signal from the sensor module that there is an obstacle ahead. As we know there are many kind of locomotion of robots are been developed these days like wheeled, tracked, crawling, walking and so on but all these robots have difficulty in overcoming obstacle on their way, if it is modified to overcome obstacle too their would be a complex design which in this model is not the case as it has a very simple design. This mechanism is designed to take over rough terrains and uneven and unknown terrains. As a overall outcome we were able to make the robot overcome the obstacles on its way in its unique way.