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Soft actuators have enabled the growth of soft robotics, overcoming several drawbacks of rigid robotics by providing devices with many degrees of freedom and the ability to grasp, bend, move, jump, and more. The reconfiguration of the workspace is still a limitation of these actuators. Indeed, once the actuator is designed and developed, it is used for a specific task. This work presents a reconfigurable soft pneumatic actuator with a novel reconfigurable modular reinforcement. The latter is wrapped around an inner tube in silicone rubber and is made of components whose assembly can be configured based on the task. A formulation is identified by a hybrid approach based on finite element analysis and response surface methodology for predicting and designing the behavior of the actuator. The prototyping revealed the ease of fabrication and reconfigurability as the strength of this new actuator. The experimental tests demonstrated the feasibility of adopting the actuator as a finger in a gripper for handling and moving objects of different shapes, masses, and stiffness. Furthermore, the evaluated performance shows a good trade-off between mass, developed force, implementation time, easy reconfigurability, and cost-effectiveness. [ABSTRACT FROM AUTHOR]

The advent of collaborative and soft robotics has reduced the mandatory adoption of safety barriers, pushing human–robot interaction to previously unreachable levels. Due to their reciprocal advantages, integrating these technologies can maximize a device's performance. However, simplifying assumptions or elementary geometries are often required due to non-linear factors that identify analytical models for designing soft pneumatic actuators for collaborative and soft robotics. Over time, various approaches have been employed to overcome these issues, including finite element analysis, response surface methodology (RSM), and machine learning (ML) algorithms. Based on the latter, in this study, the bending behavior of an externally reinforced soft pneumatic actuator was characterized by the changing geometric and functional parameters, realizing a Bend dataset. This was used to train 14 regression algorithms, and the Bilayered neural network (BNN) was the best. Three different external reinforcements, excluded for the realization of the dataset, were tested by comparing the predicted and experimental bending angles. The BNN demonstrated significantly lower error than that obtained by RSM, validating the methodology and highlighting how ML techniques can advance the prediction and mechanical design of soft pneumatic actuators. [ABSTRACT FROM AUTHOR]

In soft robotics, the most used actuators are soft pneumatic actuators because of their simplicity, cost-effectiveness, and safety. However, pneumatic actuation is also disadvantageous because of the strong non-linearities associated with using a compressible fluid. The identification of analytical models is often complex, and finite element analyses are preferred to evaluate deformation and tension states, which are computationally onerous. Alternatively, artificial intelligence algorithms can be used to follow model-free and data-driven approaches to avoid modeling complexity. In this work, however, the response surface methodology was adopted to identify a predictive model of the bending angle for soft pneumatic joints through geometric and functional parameters. The factorial plan was scheduled based on the design of the experiment, minimizing the number of tests needed and saving materials and time. Finally, a bio-inspired application of the identified model is proposed by designing the soft joints and making an actuator that replicates the movements of the scorpion's tail in the attack position. The model was validated with two external reinforcements to achieve the same final deformation at different feeding pressures. The average absolute errors between predicted and experimental bending angles for I and II reinforcement allowed the identified model to be verified. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a novel 3-degree-of-freedom (3-DOF) parallel manipulator equipped with self-sensing Ni-Ti (Nitinol) actuators. The manipulator's architecture and mechanical design are elucidated, emphasizing the integration of Nitinol actuators. The self-sensing technique implemented in a previous work was extended to a 20 mm actuator length, and the actuator was used to design the 3-DOF manipulator. Kinematic analyses were conducted to evaluate the manipulator's performance under various operating conditions. A dynamic model was implemented for the dynamic dimensioning of the actuators, which work synergistically with a bias spring. The manipulator was realized, and a control strategy was implemented. Experimental tests, although documenting some positioning accuracy issues, show the efficacy and potential applications of the proposed manipulator in robotics and automation systems, highlighting the advantages of self-sensing Nitinol actuators in small parallel manipulator designs. [ABSTRACT FROM AUTHOR]

This paper illustrates an experimental activity for the closed-loop position control of an actuator made using shape memory alloy (SMA) wire. A solution with the self-sensing effect was implemented to miniaturize the systems, i.e., without external sensors. A proportional control algorithm was initially used, demonstrating the idea's feasibility; the wire can behave simultaneously as an actuator and sensor. An experimental investigation was subsequently conducted for the optimization of the developed actuator. As for the material, a Flexinol wire, Ni-Ti alloy, with a diameter of 0.150 mm and a length of 200 mm, was used. Preliminarily, characterization of the SMA wire at constant and variable loads was carried out; the characteristics detected were elongation vs. electric current and elongation vs. electrical resistance. The control system is PC based with a data acquisition card (DAQ). A drive board was designed and built to read the wire's electrical resistance and power it by pulse width modulation (PWM). A notable result is that the actuator works with good precision and in dynamic conditions, even when it is called to support a load up to 65% different from that for which the electrical resistance–length correlation has previously been experimentally obtained, on which the control is based. This opens up the possibility of using the actuator in a counteracting configuration with a spring, which makes hardware implementation and control management simple. [ABSTRACT FROM AUTHOR]

This study describes the activity of developing a force amplifier exoskeleton with one degree of freedom. The system was developed as a research prototype to conduct control system studies. The device consists of an arm with a pneumatic cylinder actuator controlled by a pressure regulator. As for the human–machine interface, the system has a force sensor. The idea is to verify the possibility of developing a simple system from the sensor system's point of view and the control system's architecture while simultaneously obtaining an effective, economical, and reliable device. The idea developed in this project is to use the user's available ability to control movements in unknown environments. The user constitutes the central part of the entire control system: he defines the references for the speeds and forces to be applied to the environment and observes the rates of the controlled robotic system through his own sight and proprioceptive system. On the other hand, the machine produces and controls the forces applied to the environment by the actuator. In this way, the device shows an increased admittance. A mathematical system model was created to verify the idea's feasibility. Following the results of the simulations, a prototype was built on which experimental tests were carried out. As stated above, it was possible to obtain the described behavior with the use of a force sensor, one-axis type, interposed between the machine and the user, to constitute the human–machine interface; using a pressure regulator, it was possible to avoid the sensors for the force feedback by the environment. The result is a simple architecture for the sensors and the control algorithm. Specific test protocols were proposed to test the performance of the human–machine "system", and a test bench was developed that allows the tracking of variable signals represented on a monitor, which the user must follow. The system is intuitive to use, with a rapid learning curve, and the user can handle high loads according to the different signals to be followed with good precision, even at high speeds. [ABSTRACT FROM AUTHOR]

Purpose: For off-road mobility, some manual or power assisted devices were conceived to be self-driven by paraplegics while for tetraplegics non power-assisted devices were conceived. These devices require one or more conductors who are subjected to a high physical demand thus potentially creating: precarious safety condition for the user an elevated physical demand of conductors could reduce the care and the attention to give to the user; the time of the outdoor adventure experience of the user could be limited. Methods: To address these issues, an innovative user-centered power assisted off-road wheelchair for the transportation of tetraplegics along mountain trails was developed. The device, structured like a trike, is driven by two healthy conductors; the user is placed in the middle of the frame. A movable seat provides for the transfer from the standard to the off-road wheelchair. An electrical motor, powered by a battery pack, provides for the actuation. All the design and prototype aspects, the control system and experimental tests are detailed. Results: The prototype satisfies mechanical, safety and duration requirements. No physical demand while using the device and for the transfer of the user to the device was identified. Fun and engaging tests were carried out and all the participants were involved. The device has the potential to enhance the quality of life of tetraplegics in terms of new life experiences. The device revealed the real possibility of a full recreational experience, an enhanced participation and a better social integration of tetraplegics. [ABSTRACT FROM AUTHOR]