Development of a Miniature Pipe Crawler for Application in Fossil Energy Power Plants

The power generation of fossil fuel power plants relies on burning coal to generate steam. The heat exchange between the water and burned coal occurs in the combustion chamber, which operates at a high pressure and temperature. Monitoring the integrity of the tubes inside the combustion chamber is a key factor to avoid failures. However, this is not an easy task as some areas are hard to reach and the pipeline commonly has a complex geometry. Moreover, the inspection is typically manual, external and the environment is hazardous for humans. This thesis presents the development and testing of an electrically powered pipe crawler that can navigate inside 5 cm diameter tubes and provide an assessment of their health. The crawler utilizes peristaltic motion within the tubes via interconnected modules for gripping and extending. The modular nature of the system allows it to traverse through straight sections and multiple 90◦ and 180◦ bends. Additional modules in the system include an ultrasonic sensor for tube thickness measurements, as well as environmental sensors, LiDAR, and a camera. These modules utilize a gear system that allows for 360◦ rotation and provide a means of inspecting the entire internal circumference of the tubes

Design and Experimental Characterization of a Niti-Based, High-Frequency, Centripetal Peristaltic Actuator

Development and experimental testing of a peristaltic device actuated by a single shape-memory NiTi wire are described. The actuator is designed to radially shrink a compliant silicone pipe, and must work on a sustained basis at an actuation frequency that is higher than those typical of NiTi actuators. Four rigid, aluminum-made circular sectors are sitting along the pipe circumference and provide the required NiTi wire housing. The aluminum assembly acts as geometrical amplifier of the wire contraction and as heat sink required to dissipate the thermal energy of the wire during the cooling phase. We present and discuss the full experimental investigation of the actuator performance, measured in terms of its ability to reduce the pipe diameter, at a sustained frequency of 1.5 Hz. Moreover, we investigate how the diameter contraction is affected by various design parameters as well as actuation frequencies up to 4 Hz. We manage to make the NiTi wire work at 3% in strain, cyclically providing the designed pipe wall displacement. The actuator performance is found to decay approximately linearly with actuation frequencies up to 4 Hz. Also, the interface between the wire and the aluminum parts is found to be essential in defining the functional performance of the actuator

An earthworm-like modular soft robot for locomotion in multi-terrain environments

Robotic locomotion in subterranean environments is still unsolved, and it requires innovative designs and strategies to overcome the challenges of burrowing and moving in unstructured conditions with high pressure and friction at depths of a few centimeters. Inspired by antagonistic muscle contractions and constant volume coelomic chambers observed in earthworms, we designed and developed a modular soft robot based on a peristaltic soft actuator (PSA). The PSA demonstrates two active configurations from a neutral state by switching the input source between positive and negative pressure. PSA generates a longitudinal force for axial penetration and a radial force for anchorage, through bidirectional deformation of the central bellows-like structure, which demonstrates its versatility and ease of control. The performance of PSA depends on the amount and type of fluid confined in an elastomer chamber, generating different forces and displacements. The assembled robot with five PSA modules enabled to perform peristaltic locomotion in different media. The role of friction was also investigated during experimental locomotion tests by attaching passive scales like earthworm setae to the ventral side of the robot. This study proposes a new method for developing a peristaltic earthworm-like soft robot and provides a better understanding of locomotion in different environments

Developing Design and Analysis Framework for Hybrid Mechanical-Digital Control of Soft Robots: from Mechanics-Based Motion Sequencing to Physical Reservoir Computing

The recent advances in the field of soft robotics have made autonomous soft robots working in unstructured dynamic environments a close reality. These soft robots can potentially collaborate with humans without causing any harm, they can handle fragile objects safely, perform delicate surgeries inside body, etc. In our research we focus on origami based compliant mechanisms, that can be used as soft robotic skeleton. Origami mechanisms are inherently compliant, lightweight, compact, and possess unique mechanical properties such as– multi-stability, nonlinear dynamics, etc. Researchers have shown that multi-stable mechanisms have applications in motion-sequencing applications. Additionally, the nonlinear dynamic properties of origami and other soft, compliant mechanisms are shown to be useful for ‘morphological computation’ in which the body of the robot itself takes part in performing complex computations required for its control. In our research we demonstrate the motion-sequencing capability of multi-stable mechanisms through the example of bistable Kresling origami robot that is capable of peristaltic locomotion. Through careful theoretical analysis and thorough experiments, we show that we can harness multistability embedded in the origami robotic skeleton for generating actuation cycle of a peristaltic-like locomotion gait. The salient feature of this compliant robot is that we need only a single linear actuator to control the total length of the robot, and the snap-through actions generated during this motion autonomously change the individual segment lengths that lead to earthworm-like peristaltic locomotion gait. In effect, the motion-sequencing is hard-coded or embedded in the origami robot skeleton. This approach is expected to reduce the control requirement drastically as the robotic skeleton itself takes part in performing low-level control tasks. The soft robots that work in dynamic environments should be able to sense their surrounding and adapt their behavior autonomously to perform given tasks successfully. Thus, hard-coding a certain behavior as in motion-sequencing is not a viable option anymore. This led us to explore Physical Reservoir Computing (PRC), a computational framework that uses a physical body with nonlinear properties as a ‘dynamic reservoir’ for performing complex computations. The compliant robot ‘trained’ using this framework should be able to sense its surroundings and respond to them autonomously via an extensive network of sensor-actuator network embedded in robotic skeleton. We show for the first time through extensive numerical analysis that origami mechanisms can work as physical reservoirs. We also successfully demonstrate the emulation task using a Miura-ori based reservoir. The results of this work will pave the way for intelligently designed origami-based robots with embodied intelligence. These next generation of soft robots will be able to coordinate and modulate their activities autonomously such as switching locomotion gait and resisting external disturbances while navigating through unstructured environments

SMA-Based Muscle-Like Actuation in Biologically Inspired Robots: A State of the Art Review

New actuation technology in functional or "smart" materials has opened new horizons in robotics actuation systems. Materials such as piezo-electric fiber composites, electro-active polymers and shape memory alloys (SMA) are being investigated as promising alternatives to standard servomotor technology [52]. This paper focuses on the use of SMAs for building muscle-like actuators. SMAs are extremely cheap, easily available commercially and have the advantage of working at low voltages. The use of SMA provides a very interesting alternative to the mechanisms used by conventional actuators. SMAs allow to drastically reduce the size, weight and complexity of robotic systems. In fact, their large force-weight ratio, large life cycles, negligible volume, sensing capability and noise-free operation make possible the use of this technology for building a new class of actuation devices. Nonetheless, high power consumption and low bandwidth limit this technology for certain kind of applications. This presents a challenge that must be addressed from both materials and control perspectives in order to overcome these drawbacks. Here, the latter is tackled. It has been demonstrated that suitable control strategies and proper mechanical arrangements can dramatically improve on SMA performance, mostly in terms of actuation speed and limit cycles

Modular robots for sorting

Current industrial sorting systems allow for low error, high throughput sorts with tightly constrained properties. These sorters, however, are often hardware limited to certain items and criteria. There is a need for more adaptive sorting systems for processes that involve a high throughput of heterogeneous items such as import testing by port authorities, warehouse sorting for online retailers, and sorting recycling. The variety of goods that need to be sorted in these applications mean that existing sorting systems are unsuitable, and the objects often need to be sorted by hand. In this work I detail my design and control of a modular, robotic sorting system using linear actuating robots to create both low-frequency vibrations and peristaltic waves for sorting. The adaptability of the system allows for multimodal sorting and can improve heterogeneous sorting systems. I have designed a novel modular robot called the Linbot. These Linbots are based on an actuator design utilising a voice coil for linear motion. I designed this actuator to be part of a modular robot by adding on-board computation, sensing and communication. I demonstrate the individual characteristics of these robots through a series of experiments in order to give a comprehensive overview of their abilities. By combining multiple Linbots in a collective I demonstrate their ability to move and sort objects using cooperative peristaltic motion. In order to allow for rapid optimisation of control schemes for Linbot collectives I required a peristaltic table simulator. I designed and implemented a peristaltic table simulator, called PeriSim, due to a lack of existing solutions. Controllers optimised in simulation often suffer from a reduction in performance when moved to a real-world system due to the inaccuracies in the simulation, this effect is called the reality gap. I used a method for reducing the reality gap called the radical envelope of noise hypothesis, whereby I only modelled the key aspects of peristalsis in PeriSim and then varied the underlying physics of the simulation between runs. I used PeriSim to optimise controllers in simulation that worked on a real-world system. I demonstrate the how the Linbots and PeriSim can be used to build and control an adaptive sorter. I built an adaptive sorter made of a 5x5 grid of Linbots with a soft sheet covering them. I demonstrate that the sorter can grade produce and move objects of varying shapes and sizes. My work can guide the future design of industrial adaptive sorting systems