Design of biomimetic compliant devices for locomotion in liquid environments

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 161-164).Presently, there is a need for devices capable of autonomous locomotion in liquid environments. Humanitarian, industrial and defense applications are numerous and include examples such as search and rescue missions, ocean exploration, and de-mining operations. Due to the nature of the environments involved, the required devices must overcome several challenges. The main challenges are related to hardware performance in terms of propulsion efficiency, mechanical robustness, maneuverability, adaptability, stealth and autonomy. Current traditional approaches that use propeller driven devices have limited success in addressing these challenges. As a result devices that mimic fish-like swimming techniques have emerged as a promising alternative that can provide additional maneuvering features and the promise of improved performance. However, the inherent problems of current biomimetic devices have been identified as: (i) mechanical complexity due to the use of discrete and rigid components, and (ii) lack of a systematic design approach. These problems limit the practical implementation of biomimetic techniques in real mission environments. This thesis presents an alternative approach for implementing biomimetic fish-like swimming techniques by exploiting natural dynamics of compliant bodies.(cont.) The resultant devices are simpler and more mechanically robust than traditional biomimetic devices. Models are developed to express both the swimming kinematics and the corresponding swimming performance of the proposed devices, in terms of material, actuation and geometry design parameters. Design methodologies that identify the required prototype design parameters for a given target performance are proposed. The designs for caranguiform and thunniform type swimming devices are presented and their performance is characterized experimentally. Predictions based on an elongated body theory model that uses a second order approximation for the body kinematics display good agreement with prototype performance. Finally, the performance limits and the sensitivity to changes in design parameters are shown to be related to the second order system approximation of the body kinematics.by Pablo Valdivia y Alvarado.Ph.D

Modeling and Inspection Applications of a Coastal Distributed Autonomous Sensor Network

Real time in-situ measurements are essential for monitoring and understanding physical and biochemical changes within ocean environments. Phenomena of interest usually display spatial and temporal dynamics that span different scales. As a result, a combination of different vehicles, sensors, and advanced control algorithms are required in oceanographic monitoring systems. In this study our group presents the design of a distributed heterogeneous autonomous sensor network that combines underwater, surface, and aerial robotic vehicles along with advanced sensor payloads, planning algorithms and learning principles to successfully operate across the scales and constraints found in coastal environments. Examples where the robotic sensor network is used to localize algal blooms and collect modeling data in the coastal regions of the island nation of Singapore and to construct 3D models of marine structures for inspection and harbor navigation are presented. The system was successfully tested in seawater environments around Singapore where the water current is around 1-2m/s. Topics: Inspection , Modeling , Sensor networks , ShorelinesSingapore. National Research Foundation (Singapore-MIT Alliance for Research and Technology (SMART)

Soft Robotics: A Route to Equality, Diversity, and Inclusivity in Robotics

: Robotics is entering our daily lives. The discipline is increasingly crucial in fields such as agriculture, medicine, and rescue operations, impacting our food, health, and planet. At the same time, it is becoming evident that robotic research must embrace and reflect the diversity of human society to address these broad challenges effectively. In recent years, gender inclusivity has received increasing attention, but it still remains a distant goal. In addition, awareness is rising around other dimensions of diversity, including nationality, religion, and politics. Unfortunately, despite the efforts, empirical evidence shows that the field has still a long way to go before achieving a sufficient level of equality, diversity, and inclusion across these spectra. This study focuses on the soft robotics community-a growing and relatively recent subfield-and it outlines the present state of equality and diversity panorama in this discipline. The article argues that its high interdisciplinary and accessibility make it a particularly welcoming branch of robotics. We discuss the elements that make this subdiscipline an example for the broader robotic field. At the same time, we recognize that the field should still improve in several ways and become more inclusive and diverse. We propose concrete actions that we believe will contribute to achieving this goal, and provide metrics to monitor its evolution

Design, analysis and control of an autonomous conveyance module for well exploration

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaf 78).by Pablo Valdivia y Alvarado.S.M

Viscosity Control of Pseudoplastic Polymer Mixtures for Applications in Additive-Manufacturing

Various additive manufacturing (AM) processes exploit the rheological properties of non-Newtonian (e.g. pseudoplastic) polymers for stability and feature realization. For embedded 3D-printing (e3DP) and direct ink writing (DIW), features are deposited on top or within a layer of matrix/base material and the rheological properties of the matrix are crucial for satisfactory prints. Due to their high apparent viscosities under static conditions, these base polymers do not flow easily when poured in bulk into the fabrication space. Traditionally, manual methods were employed to spread them into an even layer. In this study, an alternative approach to spread and level pseudoplastic polymers using oscillatory shear stresses generated by a vibrating actuator is presented. The proposed approach lowers the viscosity of the polymers, thereby facilitating gravity-driven flow to generate a flat polymer-air interface. A fluid rheology model detailing the parameters influencing the process is presented and experiments are performed using these parameters.Mechanical Engineerin

Sensing on robots inspired by nature

Aquatic organisms capable of undergoing extensive volume variation of their body during locomotion can benefit from increased thrust production. This is enabled by making use of not only the expulsion of mass from their body, as documented extensively in the study of pulsed-jet propulsion, but also from the recovery of kinetic energy via the variation of added mass. We use a simplified mechanical system, i.e. a shape-changing linear oscillator, to investigate the phenomenon of added-mass recovery. Our study proves that a deformable oscillator can be set in sustained resonance by exploiting the contribution from shape variation alone which, if appropriately modulated, can annihilate viscous drag. By confirming that a body immersed in a dense fluid which undergoes an abrupt change of its shape experiences a positive feedback on thrust, we prove that soft-bodied vehicles can be designed and actuated in such a way as to exploit their own body deformation to benefit of augmented propulsive forces

A soft body under-actuated approach to multi degree of freedom biomimetic robots: A stingray example

In this paper we present a new application of the methodology our group is developing to design and prototype under-actuated biomimetic robots by determining appropriate body material property distributions. When excited, flexible bodies with proper anisotropic material distributions display modes of vibration that mimic required locomotion kinematics and require minimal actuation. Our previous prototypes explored simple two dimensional applications for fish-like swimming. In this paper, the three dimensional vibrational kinematics of a stingray are explored. A simple design is explained, and corresponding prototypes are presented along with preliminary performance data. Our methodology shows great promise to develop simple, robust, and inexpensive mobile robots that can efficiently accomplish locomotion.Cameron and Hayden Lord Foundatio

Self-powered micro-sensors to improve control and maneuvering of a robotic stingray

Increased demand for high-efficiency underwater vehicles has led to significant research focusing on development of biologically inspired underwater vehicle systems. In the past, many bio-inspired robotic vehicles are developed such as fish, stingray, seal, and octopus. However, development of efficient sensing system for these robots has not gained the desired momentum. In this paper, to improve the situational awareness of a robotic stingray, we developed self-powered piezoelectric MEMS pressure sensor for use on streamline bodies of underwater vehicles. This paper outlines the biological inspiration behind the development of fish-like MEMS pressure sensor, as well as demonstrates the utility of the sensors in harsh and real-time applications on a robotic stingray.4 page(s