Means Of Propulsion Research Articles

Ground reaction forces during sprint hurdles

ABSTRACT This study aimed to demonstrate ground reaction forces (GRFs) during sprint hurdles and to clarify determinants of faster sprint hurdlers. Eleven male hurdlers performed 60-m sprint hurdle trials, clearing five hurdles, during which step-to-step spatiotemporal and GRF variables were measured. The preparatory step showed smaller braking and effective vertical impulses compared with the other steps, possibly lowering the centre of mass (CM). The greater braking and smaller propulsive impulses, which result in negative net anteroposterior impulse, were characteristics of the hurdle step. This deceleration may be due to producing a large elevation of CM for clearing the hurdle through large vertical GRF production. Compared with the other steps, the second greatest braking mean force and relatively small propulsive impulse, and large propulsive impulse through long propulsive time were shown at the landing and recovery steps, respectively. The results showed better sprint hurdle performance could be achieved by minimizing braking impulse through suppressing braking time, and increasing propulsive impulse through maximizing propulsive mean force at the hurdle step; suppressing braking and propulsive times at the landing step; minimizing propulsive time, increasing effective vertical mean force, and maximizing anteroposterior net mean force through increasing propulsive mean force at the recovery step.

‘Oumuamua as a light sail: Evidence against artificial origin

‘Oumuamua, the first detected interstellar visitor to the Solar System, exhibits non-gravitational acceleration in its trajectory. In ruling out other means of propulsion, such as the evaporation of material via a cometary tail, it has been argued that radiation pressure is responsible for this acceleration. From this (a = 5 × 10−6 m s−2), the mass of the object must be approximately 4 × 104 kg, and given its dimensions, ‘Oumuamua must have a thickness of ≲1 mm if of a similar rock and iron composition as the Earth. This raises the much publicised possibility that ‘Oumuamua is artificial in origin and intentionally sent across interstellar space by an alien civilisation. This conclusion, however, relies upon the common misapprehension that light (solar) sails can accelerate to a considerable fraction of the speed of light, permitting rapid interstellar travel. We show that such speeds are unattainable for conceptual man-made sails and that, based upon its observed parameters, ‘Oumuamua would require half a billion years just to travel to our Solar System from its closest likely system of origin. These cosmological timescales make it very unlikely that this is a probe sent by an alien civilisation.

CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method

One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.

A round of applause for butterfly wings

Gently fluttering above a field of flowers on short, broad wings, butterflies are unlike any other animal aviator. With such large wings relative to their body size, these unusual fliers flap slowly, but inefficiently. So what can explain this unique body plan? Many different aerodynamic mechanisms have been previously suggested to play an important role in butterfly flight, but little data existed to assess their importance. Christoffer Johansson and Per Henningsson of Lund University, Sweden, set out to understand how these insects generate the forces of flight and shed light on the function of their iconic wings.Johansson and Henningsson focused on the role of the wing upstroke in butterfly flight. Specifically, they looked for an important function at the end of the upstroke when the wings clap together, a phenomenon found in other flying insects that helps generate the lift that keeps them aloft. The team first filmed the butterflies at high speed, taking off in a wind tunnel, and used an aerosol mist to reveal the air movements generated by their wings. They found a clear difference between the downstroke of the wings, which created lift to support the body against gravity, and the upstroke, which created thrust to move the insects forward. These measurements also revealed that the wing clap, which generates lift in other insects, contributes primarily to thrust in butterflies; at the end of the upstroke, the surfaces of the wings meet above the insect, forcing a trapped volume of air out into a jet that propels the butterflies forward.When analysing recordings of butterfly flapping, Johansson and Henningsson also observed that the wings formed a cup shape as they came together. The researchers hypothesized that the cup shape was important for improving the function and performance of the wing clap. Specifically, cupped wings could trap more air, while also forming a better seal at the edges, which together could result in a stronger, more efficient and more directed jet of air. To test this prediction, they constructed a mechanical clapper that mimicked butterfly flapping with either flexible or rigid wings. They found that the flexible wings, which were able to form a cupped shape, produced stronger and more efficient jets than the rigid wings, which slapped together.Using relatively large wings to flap slowly is not an efficient way of generating lift and creates a great deal of aerodynamic drag. Therefore, the ability of large flexible wings to generate thrust through such an effective clap may be key to balancing the apparent inefficiencies of butterfly flight. The strong jets generated by the wing clap may also contribute to the erratic nature of butterfly flight, which is useful to escape predators. This could explain the persistence of the butterflies’ unusual body plan and flight style. Johansson and Henningsson have also identified the cupped wing clap as an alternative means of jet propulsion that may be exploited by other flying, or swimming, animals and robots. Clearly, butterflies and their exceptional wings are worthy of acclaim not just as graceful beauties but also as mechanical marvels.

Short-Term Creatine Loading Improves Total Work and Repetitions to Failure but Not Load-Velocity Characteristics in Strength-Trained Men.

This study assessed the effects of a 7-day creatine (CRE) supplementation on the load–velocity profile and repeated sub-maximal bouts in the deep squat using mean propulsive velocity (MPV) and mean propulsive power (MPP). Eleven strength-trained men (31.4 ± 5.4 years) supplemented 0.3 g·kg−1·d−1 CRE or a placebo (PLA, maltodextrin) for seven days in a randomized order, separated by a 30-day washout period. Prior to and after the supplementation, the subjects performed an incremental maximal strength (1RM) test, as well as 3 × 10 repetitions and a repetitions-to-failure test (RFT), all at 70% 1RM. Maximal strength remained statistically unaltered in CRE (p = 0.107) and PLA (p = 0.568). No statistical main effect for time (p = 0.780) or interaction (p = 0.737) was observed for the load–velocity profile. The number of repetitions during RFT remained statistically unaltered in both conditions (CRE: +16.8 ± 32.8%, p = 0.112; PLA: +8.2 ± 47.2%, p = 0.370), but the effect size was larger in creatine compared to placebo (g = 0.51 vs. g = 0.01). The total work during RFT increased following creatine supplementation (+23.1 ± 35.9%, p = 0.043, g = 0.70) but remained statistically unaltered in the placebo condition (+15.0 ± 60.8%, p = 0.801, g = 0.08; between conditions: p = 0.410, g = 0.25). We showed that CRE loading over seven days did not affect load–velocity characteristics but may have increased total work and power output during submaximal deep squat protocols, as was indicated by moderate effect sizes.

Guidelines and procedure for tailoring high-performance, steady-state traveling waves for propulsion and solid-state motion

Structure-Borne Traveling Waves (SBTWs) have significant promise as a means of underwater propulsion, solid-state motion, and drag reduction. However, there is limited understanding over how to tailor SBTWs for these applications. This study establishes guidelines and a procedure for tailoring SBTWs on thin-walled two-dimensional (2D) surfaces. These guidelines were specifically crafted to yield SBTWs favorable for propulsion and solid-state motion: propagation along a uniform direction and with consistent amplitude. SBTWs are steady-state traveling waves generated by taking advantage of a surface’s modal properties (i.e. mode shapes). This novel mechanism provides significant benefits including a minimal actuation footprint, a wide frequency bandwidth, and active variability (propagation direction, wavelength, etc). However, this mechanism also introduces a dependence on the mode shapes and actuator location. Thus, to tailor SBTWs favorable for propulsion the relationship between SBTWs, the mode shapes, and actuator locations must be understood. Eight Guidelines governing this relationship are established. These Guidelines are demonstrated using SBTWs generated on a previously validated model of a 2D plate. Among others, it is shown that the frequency bandwidth can be broken into distinct frequency regions, and each region can be classified as yielding favorable or unfavorable SBTWs. A multi-step procedure is then introduced that enables SBTWs to be tailored on any thin-walled surface. Numerically or experimentally applicable, the actuator configuration can be defined to tailor SBTWs with a specific propagation direction; all that is required is knowledge of the mode shapes. Finally, a case study is presented in which the guidelines and procedure are implemented to tailor SBTWs on a trapezoidal surface. Two different sets of SBTWs are tailored, each propagating in different directions and with various wavelengths. Thus, the established guidelines and procedure enable SBTWs to be tailored for specific applications, such as propulsion and solid-state motion.

Environmental Change and Modernization of Fishing Gear for Fishermen in Depok Beach, Bantul, Yogyakarta 1995-2010

The purpose of this study is to analyze environmental changes and modernization of fishing gear for fishermen. This article identifies and evaluates several impacts of the implementation of modernization of fishing gear, particularly by taking a case study on the fishing environment of Depok Beach, Bantul, Yogyakarta. This research is categorized as maritime history research. This study uses the historical method with a sociological approach. The results of this study state that Depok fishermen have experienced several changes in their fishing gear. Those who used to use traditional fishing gear then use modern fishing gear. Characterized by the use of the engine as a means of propulsion of the boat which in turn causes the fishing range to be wider. The influence of modernization has changed the mindset of the fishing community of Depok Beach. In addition, the threat of abrasion is very dangerous for buildings around the coast. Abrasion that occurs is caused by strong waves. Strong waves occur due to gusts of wind from the Indian Ocean. The waves continuously erode the sediment on the beach. The scour will affect the land area and will also affect the reduced activity. The effect of abrasion on buildings is very dangerous and detrimental to the people of Depok Beach.

Sailing at the brink – The no-limits of near-/now-term-technology solar sails and SEP spacecraft in (multiple) NEO rendezvous

Near-Earth object (NEO) in-situ exploration can provide invaluable information for science, possible future deflection actions and resource utilisation. This is only possible with space missions which approach the asteroid from its vicinity, i.e. rendezvous. This paper explores the use of solar sailing as means of propulsion for NEO rendezvous missions. Given the current state of sail technology, we search for multiple rendezvous missions of up to ten years and characteristic acceleration of up to 0.10 mm/s2. Using a tree-search technique and subsequent trajectory optimisation, we find numerous options of up to three NEO encounters in the launch window 2019–2027. In addition, we explore steerable and throttleable low-thrust (e.g. solar-electric) rendezvous to a particular group of NEOs, the Taurid swarm. We show that an acceleration of 0.23 mm/s2 would suffice for a rendezvous in approximately 2000 days, while shorter transfers are available as the acceleration increases. Finally, we show low-thrust options (0.3 mm/s2) to the fictitious asteroid 2019 PDC, as part of an asteroid deflection exercise.

A Scientific Study of the Unidentified Flying Objects in accordance with Anti-Gravity

<p>Electrohydrodynamics, semi-quantum kinetics, anti-gravity, electro-gravitics, gravito-electrics, all these are classified as the ‘black’ area of theoretical and experimental physics because, these theories tend to explain the amazing science behind the alien means of propulsion, thereby giving answers to many questions like, how they travel such long distances? Do they need any kind of fuel? If so, then why are they not seen to be massive like the rockets with 80-90% fuel capacities? Do they travel in perpetual motion? Is the fact really true that they can harness energy from the nature? Then, do they travel at a speed faster than that of light? These, along with many facts are still unexplainable to modern day physics, its not unexplainable but rather its covert and classified, government does not want to disclose the science behind UFOs that they have gathered through reverse engineering of ‘crashed alien crafts’ and through the covert research of many scientists who were engaged in black R&D operations. This paper will answer the researches and physics behind those unexplained phenomena’s because, once explained they tend to shake the pillars of modern physics.</p>

Generating and tailoring Structure-Borne Traveling Waves on two-dimensional surfaces

Structure-Borne Traveling Waves (SBTWs) have significant potential as a means of underwater propulsion and drag reduction, but there is limited understanding of how to tailor SBTWs, especially on the two-dimensional (2D) surfaces needed for these applications. To tailor SBTWs on 2D surfaces they must propagate in defined directions and have controlled patterns (e.g. wavelength). This study presents the initial step towards tailoring application-ready SBTWs on 2D surfaces. A finite element model is developed for a realistic system, correlated with test, and then used to perform a case study on tailoring SBTWs. The model represents a thin plate with electro-mechanically coupled piezoelectric actuators, elastic boundary conditions, and internal pre-stresses. Experimental validation demonstrates that the model accurately captures both the modal properties and SBTW generation of the realistic system. This enables the model to investigate the underlying dynamics and tailoring of SBTWs without the need for time-intensive experiments. A quality metric is also introduced which quantifies, for the first time, the quality of SBTWs on a 2D surface. The correlated model and quality metric are then used in a case study to tailor SBTWs on the 2D surface at three different frequencies. These SBTWs are tailored through definition and then manipulation of the actuation configuration (location, number, and phasing of actuators) to excite specific mode shapes and control the SBTW pattern. The resultant, tailored SBTWs propagate in defined directions and have controlled patterns, providing insight into the underlying dynamics of SBTWs. The novel quality metric, tailored SBTWs, and SBTW insights represent a substantial step towards realizing application-ready SBTWs on 2D surfaces.

Winds of Trade: Passage to Zero‐Emission Shipping

AbstractThe shipping industry needs to decarbonize over the coming decades, but there are competing visions about how that will happen. While major shipping companies are looking to potential new fuels, including ammonia, other disruptors are already shipping small quantities of boutique goods, emission free, on sailboats harnessing the power of the wind. They are a reminder that all global trade used to travel by sail. Can wind propel us back to the future? There is a role for wind power in shipping as both a primary means of propulsion and a way to provide wind assistance to reduce a vessel’s fuel use. This article examines the possibilities and challenges for wind‐based sea transport.

Perspectives, frontiers, and new horizons for plasma-based space electric propulsion

There are a number of pressing problems mankind is facing today that could, at least in part, be resolved by space systems. These include capabilities for fast and far-reaching telecommunication, surveying of resources and climate, and sustaining global information networks, to name but a few. Not surprisingly, increasing efforts are now devoted to building a strong near-Earth satellite infrastructure, with plans to extend the sphere of active life to orbital space and, later, to the Moon and Mars if not further. The realization of these aspirations demands novel and more efficient means of propulsion. At present, it is not only the heavy launch systems that are fully reliant on thermodynamic principles for propulsion. Satellites and spacecraft still widely use gas-based thrusters or chemical engines as their primary means of propulsion. Nonetheless, similar to other transportation systems where the use of electrical platforms has expanded rapidly, space propulsion technologies are also experiencing a shift toward electric thrusters that do not feature the many limitations intrinsic to the thermodynamic systems. Most importantly, electric and plasma thrusters have a theoretical capacity to deliver virtually any impulse, the latter being ultimately limited by the speed of light. Rapid progress in the field driven by consolidated efforts from industry and academia has brought all-electric space systems closer to reality, yet there are still obstacles that need addressing before we can take full advantage of this promising family of propulsion technologies. In this paper, we briefly outline the most recent successes in the development of plasma-based space propulsion systems and present our view of future trends, opportunities, and challenges in this rapidly growing field.

Preliminary Stability and Resistance Analysis of the Cheops Boat

The Cheops Boat is the most complete, largest, and one of the oldest boats ever excavated, but it has received surprisingly little study by Naval Architects. The 43-m boat was constructed around 2500 BC and placed, disassembled, in a pit next to the Great Pyramid at Giza in Egypt. Since its discovery in 1954, there has been speculation about its original design, means of propulsion, and purpose. This article presents previously unpublished results of the first tank testing of a model of the Cheops Boat and some preliminary conclusions about the design, propulsion, and function of the original. It is shown that the stability characteristics of the boat make it suited for carrying lightweight cargo and people in the protected waters of the Nile. Towing tests have shown that the boat can be safely rowed in a variety of wind and current conditions. Windward sailing calculations have shown that, if fitted with sail, then boats such as the Cheops Boat perform well downwind, but sail no closer than a beam reach. During the 1954 clearing of debris from the Giza Plateau, it was noticed that the Great Pyramid's north and west enclosure walls were 23.6m from the base of pyramid, but the south wall was 5mcloser to the base. Careful inspection revealed that the south wall had been built in an asymmetrical location to conceal two boat pits beneath it. The two pits were end to end, one covered by 41 massive limestone blocks and the other by 40. When the eastern pit was opened, the remains of the disassembled boat were revealed. Figure 1 shows photographs of some of the pieces as they were removed from the pit. Remarkably, the 4500-year-old cedar had been so well preserved that it was possible to reassemble this boat like a kit. Even the rope was preserved, and looked like what could be bought today.

Simulation regarding the forward part of underwater remotely operated vehicle designed for research in maritime and river districts

Over the last few decades, underwater mechanical system became a necessity for ocean research and exploration. The necessity of this type of equipment provides a new type of marine platforms in different areas of oceanographic research. Until this moment, the underwater vehicles have developed in different shapes, sizes and means of propulsion. Take into consideration these characteristics, we could determinate the type and mission of the vehicle. In this paper we investigate the problem regarding the pressure exerted of remotely operated vehicle. The remotely operated vehicle is designed in order to achieve different mission regarding the surveillance in lakes, harbors and maritime environment. This mission can take place through a remote control system placed onshore or on seaborne platforms. To improve the endurance of remotely operated vehicle, we performed a simulation study during which we compare the drag forces acts on the underwater vehicle according to its shape. Using SolidWorks program to create the body simulation vehicle and Ansys CFX to realise the simulation, this paper present the result simulated for the forward part of the vehicle.

PERFORMANCE VERIFICATION OF A RECENT ROTOR SAIL INSTALLATION

Auxiliary wind propulsion offers viable solution to reduce the emissions of global shipping. While it is very traditional means of propulsion, it is relatively new to modern commercial shipping. It is then highly important to provide the industry with independent and verified data of its performance. This paper reviews measurement campaigns conducted onboard cruise ferry Viking Grace, which was retrofitted with a Rotor Sail in April 2018. Four different approaches to the performance verification were applied and the results show good agreement between results from different methods. These results are also seen to be in-line with the original target of the project.

Fore-aft resistance applied at the center of mass using a novel robotic interface proportionately increases propulsive force generation in healthy nonimpaired individuals walking at a constant speed

BackgroundPast studies have utilized external interfaces like resistive bands and motor-generated pulling systems to increase limb propulsion during walking on a motorized treadmill. However, assessing changes in limb propulsion against increasing resistance demands during self-controlled walking has not been undertaken.PurposeWe assessed limb propulsion against increasing fore-aft loading demands by applying graded fore-aft (FA) resistance at the center of mass during walking in a novel, intent-driven treadmill environment that allowed participants to control their walking speeds. We hypothesized that to maintain a target speed against progressively increasing resistance, participants would proportionately increase their limb propulsion without increasing vertical force production, with accompanying increases in trailing limb angle and positive joint work.MethodsSeventeen healthy-nonimpaired participants (mean age 52 yrs., SD = 11) walked at a target, self-controlled speed of 1.0 m/s against 10, 15, 20, and 25% (% body weight) FA resistance levels. We primarily assessed linear slope values across FA resistance levels for mean propulsive force and impulse and vertical impulse of the dominant limb using one-sample t-tests. We further assessed changes in trailing and leading limb angles and joint work using one-way ANOVAs.ResultsParticipants maintained their target velocity within an a priori defined acceptable range of 1.0 m/s ± 0.2. They significantly increased propulsion proportional to FA resistance (propulsive force mean slope = 2.45, SD = 0.7, t (16) =14.44, p < 0.01; and propulsive impulse mean slope = 0.7, SD = 0.25, t (16) = 11.84, p < 0.01), but had no changes in vertical impulse (mean slope = − 0.04, SD =0.17, p > 0.05) across FA resistance levels. Mean trailing limb angle increased from 24.3° at 10% resistance to 27.4° at 25% (p < 0.05); leading limb angle decreased from − 18.4° to − 12.6° (p < 0.05). We also observed increases in total positive limb work (F (1.7, 26) = 16.88, p ≤ 0.001, η2 = 0.5), primarily attributed to the hip and ankle joints.ConclusionsFA resistance applied during self-driven walking resulted in increased propulsive-force output of healthy-nonimpaired individuals with accompanying biomechanical changes that facilitated greater limb propulsion. Future rehabilitation interventions for neurological populations may be able to utilize this principle to design task-specific interventions like progressive strength training and workload manipulation during aerobic training for improving walking function.

Influence of Heart Rate Variability Variables in Half Squat Performance in Female Athletes

The search of non-invasive and easy-to-monitor variables is essential to improve the athlete performance. The assessment of neuromuscular characteristics, such as velocity, with a lineal position transducer (LPT), allows training optimization and just like heart rate variability (HRV) guaranties an adequate athlete monitoring. The autonomic nervous system (ANS) and Sympathetic nervous system (SNS) exert an important influence on skeletal muscle functions. However, there are no studies that correlate the activity of SNS with current technologies such as LPT to calculate several neuromuscular performance variables. Otherwise, the results of HRV assessment could be related to a TLP strength test performance. PURPOSE: The aim of this study is to find correlations between HRV variables and TLC variables during a half squat movement in young female soccer players. METHODS: Thirteen professional female soccer players were tested (Age 20.7 years +/-2.62, Weight 60.9 kg +/- 4.4), we analyzed HRV during standing, we also evaluated the velocity of a half squat movement with a LPT, during a maximal strength test, statistical analyses were performed to determine associations. RESULTS: Associations were found between Stress index during standing position and Mean acceleration to Maximal velocity (m/s/s) (R2 0,3115 P 0,0381), Mean velocity (R2 0,3284 P 0,0322), Propulsive mean velocity (R2 0,3189 P 0,0354). CONCLUSIONS: Stress Index (SI) is a variable that reflects sympathetic activation and suggest autonomic reactivity to stress situations indicating an adequate response to confront the demands presented by the sport. Thus, an abnormal sympathetic predominance could result in chronic fatigue which would evince a SI higher elevation, giving the index greater value. According to our findings the SI during standing position correlated with velocity and acceleration variables during half squat, this suggests that adequate sympathetic reactivity could contribute to the improvement of neuromuscular variables. We hypothesized that SI could be a simple non-invasive way to measure sympathetic reactivity in sports, being part in assessment and monitoring of performance. We also suggest that interventions aimed to improve sympathetic reactivity could improve neuromuscular performance.

Serpens: A Highly Compliant Low-Cost ROS-Based Snake Robot with Series Elastic Actuators, Stereoscopic Vision and a Screw-Less Assembly Mechanism

Snake robot locomotion in a cluttered environment where the snake robot utilises a sensory-perceptual system to perceive the surrounding operational environment for means of propulsion is defined as perception-driven obstacle-aided locomotion (POAL). From a control point of view, achieving POAL with traditional rigidly-actuated robots is challenging because of the complex interaction between the snake robot and the immediate environment. To simplify the control complexity, compliant motion and fine torque control on each joint is essential. Accordingly, intrinsically elastic joints have become progressively prominent over the last years for a variety robotic applications. Commonly, elastic joints are considered to outperform rigid actuation in terms of peak dynamics, robustness, and energy efficiency. Even though a few examples of elastic snake robots exist, they are generally expensive to manufacture and tailored to custom-made hardware/software components that are not openly available off-the-shelf. In this work, Serpens, a newly-designed low-cost, open-source and highly-compliant multi-purpose modular snake robot with series elastic actuator (SEA) is presented. Serpens features precision torque control and stereoscopic vision. Only low-cost commercial-off-the-shelf (COTS) components are adopted. The robot modules can be 3D-printed by using Fused Deposition Modelling (FDM) manufacturing technology, thus making the rapid-prototyping process very economical and fast. A screw-less assembly mechanism allows for connecting the modules and reconfigure the robot in a very reliable and robust manner. The concept of modularity is also applied to the system architecture on both the software and hardware sides. Each module is independent, being controlled by a self-reliant controller board. The software architecture is based on the Robot Operating System (ROS). This paper describes the design of Serpens and presents preliminary simulation and experimental results, which illustrate its performance.

What’s the best way to build a molecular machine?

Chemists are tinkering with a variety of different designs and means of propulsion, though practical uses for these mini-motors have yet to be realized. Some of the smallest, most useful machines known to science are the biological molecules that keep living things living. The protein myosin drives the contraction and relaxation of muscle. Kinesin drags cellular cargo around the cell. Motor enzymes unwind, rewind, and maintain DNA, and bacteria use a molecular motor to rotate their whip-like flagella up to 100,000 times per minute, propelling them forward. These machines turn chemical energy into motion. They’re very efficient at their jobs. Seeking various ways to build molecular motors that can do meaningful work, researcher David Leigh came up with designs such as the one depicted here, a version of a molecular structure called a catenane that’s powered by chemical reactions. Illustration courtesy of Jo Richers (artist) and David Leigh (University of Manchester, Manchester, United Kingdom). Now researchers are building synthetic cousins of these molecular machines, taking inspiration not only from their design but also their function. “Nature has worked with over 3 billion years of evolution to use them for every conceivable thing,” says chemist David Leigh at the University of Manchester in the United Kingdom, who has developed a variety of nanoscale machines. “So perhaps nature should tell us how and why to use them.” The idea of using molecules to build minuscule machines that perform useful tasks dates back at least to a lecture given in 1959 by physicist Richard Feynman titled “There’s Plenty of Room at the Bottom.”* More recently, demonstrations of artificial molecular machines offer good reasons to think that such devices are feasible. Researchers have forged motors, shuttles, elevators, walkers, and pumps out of molecules, and powered them with electrical energy, chemical reactions, or light. Tiny …

SnakeSIM: a ROS-based control and simulation framework for perception-driven obstacle-aided locomotion of snake robots

Biological snakes are capable of exploiting roughness in the terrain for locomotion. This feature allows them to adapt to different types of environments. Snake robots that can mimic this behaviour could be fitted with sensors and used for transporting tools to hazardous or confined areas that other robots and humans are unable to access. Snake robot locomotion in a cluttered environment where the snake robot utilises a sensory–perceptual system to perceive the surrounding operational environment for means of propulsion can be defined as perception-driven obstacle-aided locomotion (POAL). The initial testing of new control methods for POAL in a physical environment using a real snake robot imposes challenging requirements on both the robot and the test environment in terms of robustness and predictability. This paper introduces SnakeSIM, a virtual rapid-prototyping framework that allows researchers for the design and simulation of POAL more safely, rapidly and efficiently. SnakeSIM is based on the robot operating system (ROS) and it allows for simulating the snake robot model in a virtual environment cluttered with obstacles. The simulated robot can be equipped with different sensors. Tactile perception can be achieved using contact sensors to retrieve forces, torques, contact positions and contact normals. A depth camera can be attached to the snake robot head for visual perception purposes. Furthermore, SnakeSIM allows for exploiting the large variety of robotics sensors that are supported by ROS. The framework can be transparently integrated with a real robot. To demonstrate the potential of SnakeSIM, a possible control approach for POAL is considered as a case study.