Preliminary finite element modeling of a piezoelectric actuated marine propulsion fin

New technologies surrounding composite materials and autonomous underwater vehicle (AUV) design have led to numerous studies involving the marine propulsion for these AUVs. AUVs traditionally are classified as highly efficient, payload capable, and can be utilized as reconnaissance or surveillance vehicles. Undullatory and oscillatory propulsion devices have been conceived to replace the present propulsion technologies, of propellers, with highly maneuverable, efficient, and quiet propulsion systems. Undullatory and oscillatory propulsion has been around for centuries employed by aquatic life, but only recently have the mini-technologies been available to present such propulsion devices economically and with enough materials research as to mimic biologic life on the same scale. Piezoelectric properties coupled with a thin plate allow for actuation properties, similar to bimetallic metals. Applying two piezoelectrics to the fixed end of a cantilevered beam or plate, on opposite sides, and actuating them with an opposite phase shift in electrical voltage potential results in transverse motion of the beam from the orthogonal plane to the vertical axis of the piezoelectric device. Coupling this property to a particular fiber orientation, composite thin plate, significantly increases the actuation properties. In addition, placing more than two piezoelectrics along the length of the thin composite plate gives the potential to increase actuation properties and change the motion from oscillatory to undullatory. These motions can again be increased by utilizing the natural vibration modes of the thin composite plate with piezoelectrics near resonance actuation. The current research is involved with modeling a piezoelectric actuated marine propulsion fin using the Galerkin finite element technique. An experimental proof of concept was developed to compare results. Using fluid-structure interaction (FSI) methods, it is proposed that the fluid and structure programs are resolved within one program. This is in contrast to traditional attempts at FSI problems that utilize a computational fluid dynamics (CFD) solver transferring load data between a structural dynamics/finite element (FE) program

Insects have the capacity for subjective experience

To what degree are non-human animals conscious? We propose that the most meaningful way to approach this question is from the perspective of functional neurobiology. Here we focus on subjective experience, which is a basic awareness of the world without further reflection on that awareness. This is considered the most basic form of consciousness. Tellingly, this capacity is supported by the integrated midbrain and basal ganglia structures, which are among the oldest and most highly conserved brain systems in vertebrates. A reasonable inference is that the capacity for subjective experience is both widespread and evolutionarily old within the vertebrate lineage. We argue that the insect brain supports functions analogous to those of the vertebrate midbrain and hence that insects may also have a capacity for subjective experience. We discuss the features of neural systems which can and cannot be expected to support this capacity as well as the relationship between our arguments based on neurobiological mechanism and our approach to the “hard problem” of conscious experience

The Research on Soft Pneumatic Actuators in Italy: Design Solutions and Applications

Interest in soft actuators has increased enormously in the last 10 years. Thanks to their compliance and flexibility, they are suitable to be employed to actuate devices that must safely interact with humans or delicate objects or to actuate bio-inspired robots able to move in hostile environments. This paper reviews the research on soft pneumatic actuators conducted in Italy, focusing on mechanical design, analytical modeling, and possible application. A classification based on the geometry is proposed, since a wide set of architectures and manufacturing solutions are available. This aspect is confirmed by the extent of scenarios in which researchers take advantage of such systems’ improved flexibility and functionality. Several applications regarding bio-robotics, bioengineering, wearable devices, and more are presented and discussed

Emerging Trends in Mechatronics

Mechatronics is a multidisciplinary branch of engineering combining mechanical, electrical and electronics, control and automation, and computer engineering fields. The main research task of mechatronics is design, control, and optimization of advanced devices, products, and hybrid systems utilizing the concepts found in all these fields. The purpose of this special issue is to help better understand how mechatronics will impact on the practice and research of developing advanced techniques to model, control, and optimize complex systems. The special issue presents recent advances in mechatronics and related technologies. The selected topics give an overview of the state of the art and present new research results and prospects for the future development of the interdisciplinary field of mechatronic systems

Quasi-Articulation of a Continuous Robotic Manipulator Enabled by Stiffness-Switching Origami Joints

Soft robots possess a nearly infinite number of kinematic degrees of freedom due to the compliance of their underlying materials which enables them to accomplish incredible feats of movement and adaptation. However, their severely underactuated structures limit their controllability and the degree of precision that can be achieved. As demonstrated by the octopus when fetching prey, it is possible to achieve precise movement in an otherwise “soft” arm by stiffening select sections of the arm while keeping other sections flexible, in effect generating a quasi-articulated structure and reducing the degrees of freedom from practically infinite to a finite number of angles. In this study, we use the bistable generalized Kresling origami to emulate this strategy. Both experimental and computational modeling procedures are conducted to evaluate the bending mechanics of the structure at each of its two stable states (extended and contracted). As the model accurately predicts the major trends observed in experiments, it is used to perform a parametric study on the bending stiffness ratio, defined as the ratio of bending stiffness at the extended state to the bending stiffness at the contracted state. Using the results of the parametric study, we discover that the Kresling design which maximizes the bending stiffness ratio is that possessing the greatest angle ratio λ, the lowest contracted height Lc, and the largest number of sides of the base polygon n, enabling the transformation of the structure from rigid to flexible. To complete the study, we use the optimal Kresling design in the fabrication of a tendon-driven reconfigurable manipulator composed of three Kresling modules. We find that by reconfiguring the Kresling module states (rigid or flexible), the manipulator can effectively transform into 2m different configurations where m corresponds to the number of modules. Through this reconfiguration, the manipulator can generate a quasi-articulated structure which reduces its effective degrees of freedom and enables linkage-like motion. Unlike other methods of stiffness modulation, this solution reduces system complexity by using a bistable structure as both the body of the robot and as a mechanism of stiffness-switching. The structure’s primary reliance on geometry for its properties makes it a scalable solution, which is appealing for minimally invasive surgical applications where both precision and adaptability are vital. The manipulator may also be used as an inspection or exploration robot to access areas that may be inaccessible to humans or rigid robots

Energy-based approach to develop soft robots

Soft robotic systems offer advantages against rigid robot systems in applications that involve physical robot-human interactions, unstructured or extreme environments, and manipulating delicate objects. Soft robots can offer inherently safe operation and adapt to unknown geometry of the environment or object. The current soft robot development approach is an empirical approach starting from a type of soft actuation technology, whereas the development of rigid robots can start from a top-level task in a System Engineering framework. The rigid robot developer can select from well-defined components to construct the task-orientated system. Soft robots are relatively novel systems compared with rigid robots and do not have well-defined components due to a wide range of soft actuation technologies. The initial choice of soft actuation technology places constraints on the system to perform the task. Soft robotic systems are not widely used despite the advantages compared to rigid robots. In this thesis, I study an abstraction approach to enable a System Engineering framework to develop soft robotic systems. My research focus is on an energy-based approach that encompasses the multi-domain nature of soft robotic systems. The impact on the final system from the energy transfer characteristics of the initial choice of the soft actuator has not been fully explored in the literature. I study how energy, and rate of energy transfer (power), can describe different components of each type of soft actuation and how the total energy can model the top-level system. This thesis includes (i) a literature review of soft robots; (ii) an abstraction approach based on bond-graph theory applied to soft actuation technologies; (iii) a port-Hamiltonian theory to describe the top-level soft robotic system, and (iv) an experimental application of the approach on a type of soft actuation technology. In summary, I explore how energy and rate of energy transfer can provide the abstraction approach and in time provide the well-defined components necessary for task-orientated design approaches in a System Engineering framework. In particular, I applied the approach to soft pneumatic systems for additional insights relevant to the development of future task-orientated soft robotic systems.EPSRC Doctoral Training Centre in Robotics and Autonomous Systems funding