Locomotion Mechanism Research Articles

Vector-Controlled Wheel-Like Magnetic Swarms With Multimodal Locomotion and Reconfigurable Capabilities.

Inspired by the biological collective behaviors of nature, artificial microrobotic swarms have exhibited environmental adaptability and tasking capabilities for biomedicine and micromanipulation. Complex environments are extremely relevant to the applications of microswarms, which are expected to travel in blood vessels, reproductive and digestive tracts, and microfluidic chips. Here we present a strategy that reconfigures paramagnetic nanoparticles into a vector-controlled microswarm with 3D collective motions by programming sawtooth magnetic fields. Horizontal swarms can be manipulated to stand vertically and swim like a wheel by adjusting the direction of magnetic-field plane. Compared with horizontal swarms, vertical wheel-like swarms were evaluated to be of approximately 15-fold speed increase and enhanced maneuverability, which was exhibited by striding across complex 3D confinements. Based on analysis of collective behavior of magnetic particles in flow field using molecular dynamics methods, a rotary stepping mechanism was proposed to address the formation and locomotion mechanisms of wheel-like swarm. we present a strategy that actuates swarms to stand and hover in situ under a programming swing magnetic fields, which provides suitable solutions to travel across confined space with unexpected changes, such as stepped pipes. By biomimetic design from fin motion of fish, wheel-like swarms were endowed with multi-modal locomotion and load-carrying capabilities. This design of intelligent microswarms that adapt to complicated biological environments can promote the applications ranging from the construction of smart and multifunctional materials to biomedical engineering.

Hermetically-Sealed Flexible Mobile Robot “MOLOOP” for Narrow Terrain Exploration

Conventional mobile robots typically use a wheel or crawler mechanism for locomotion. However, these robots often get stuck in narrow spaces. To mitigate this issue, we propose an innovative flexible mobile robot named “MOLOOP” in this study. The proposed robot has double-looped and hermetically-sealed structure and all ground-contact-area moves to the same direction. Three synchronized flexible crawlers generate the driving force within the robot body. The crawler, named “HS crawler,” comprises of loop-connected flexible bags. The entire body of the robot is flexible; therefore, the robot can pass through narrow terrains with adaptive shape changes. However, in terms of power and size, performance improvement is necessary for the practical use of the robot. This paper describes the improvement of HS crawler performance, which directly affects the driving force, traveling speed, and size of the robot. For the purpose of high input pressure, this study reinforced the flexible bags of the crawler using fibrous materials. This reinforcement realizes the power-up and downsizing of the flexible bags. The new crawler achieves a performance of 3.43 Nm torque and 39.0 mm/s traveling speed, compared to a torque of 0.23 Nm and traveling speed of 3.0 mm/s of the previous crawler. Additionally, the width of the new MOLOOP changed to 270 mm from 420 mm because of the downsized crawler. Furthermore, a dedicated mechanical valve was developed. This valve achieves a flow rate of 2.39 L/min as compared to 0.92 L/min of a commercially available solenoid valve. Moreover, the traveling speed of MOLOOP increased from 3.0 mm/s to 9.0 mm/s. The prototype robot successfully passed through a narrow terrain with a minimum width of 200 mm (robot width: 270 mm).

Contribution of Afferent Feedback to Adaptive Hindlimb Walking in Cats: A Neuromusculoskeletal Modeling Study

Mammalian locomotion is generated by central pattern generators (CPGs) in the spinal cord, which produce alternating flexor and extensor activities controlling the locomotor movements of each limb. Afferent feedback signals from the limbs are integrated by the CPGs to provide adaptive control of locomotion. Responses of CPG-generated neural activity to afferent feedback stimulation have been previously studied during fictive locomotion in immobilized cats. Yet, locomotion in awake, behaving animals involves dynamic interactions between central neuronal circuits, afferent feedback, musculoskeletal system, and environment. To study these complex interactions, we developed a model simulating interactions between a half-center CPG and the musculoskeletal system of a cat hindlimb. Then, we analyzed the role of afferent feedback in the locomotor adaptation from a dynamic viewpoint using the methods of dynamical systems theory and nullcline analysis. Our model reproduced limb movements during regular cat walking as well as adaptive changes of these movements when the foot steps into a hole. The model generates important insights into the mechanism for adaptive locomotion resulting from dynamic interactions between the CPG-based neural circuits, the musculoskeletal system, and the environment.

Underactuated Soft Hip Exosuit Based on Adaptive Oscillators to Assist Human Locomotion

Reproducing the mechanisms of human locomotion is a hard challenge. Assistive wearable devices in this context need to be lightweight, portable, and to adapt to the wearer’s walking pattern. Aiming to combine the aforementioned features, we developed a soft wearable exosuit to assist hip flexion during walking. The main feature of the device is underactuation, i.e., a single actuator is used to assist bilateral hip flexion. A control strategy based on Adaptive Oscillators and gait phase estimation is implemented to deliver flexible assistance and to adapt to changes in walking pattern. The system was tested on six healthy subjects. Preliminary results show good performance of the control algorithm to track human gait and to deliver symmetrical assistance to both legs. First kinematic and muscular assessments revealed promising results at walking speeds near to the natural human walking, where the device did not alter hip kinematics and decreased the effort required by muscles contributing to hip flexion. Once validated on a larger sample of subjects, the device can have the potentialities to be used in clinical and wellness applications.

ARCSnake: Reconfigurable Snakelike Robot With Archimedean Screw Propulsion for Multidomain Mobility

Exploring and navigating in extreme environments, such as caves, oceans, and planetary bodies, are often too hazardous for humans, and as such, robots are possible surrogates. These robots are met with significant locomotion challenges that require traversing a wide range of surface roughnesses and topologies. Previous locomotion strategies, involving wheels or ambulatory motion, such as snake platforms, have success on specific surfaces but fail in others which could be detrimental in exploration and navigation missions. In this paper, we present a novel approach that combines snake-like robots with an Archimedean screw locomotion mechanism to provide multiple, effective mobility strategies in a large range of environments, including those that are difficult to traverse for wheeled and ambulatory robots. This work develops a robotic system called ARCSnake to demonstrate this locomotion principle and tested it in a variety of different terrains and environments in order to prove its controllable, multi-domain, navigation capabilities. These tests show a wide breadth of scenarios that ARCSnake can handle, hence demonstrating its ability to traverse through extreme terrains.

Terrestrial force production by the limbs of a semi-aquatic salamander provides insight into the evolution of terrestrial locomotor mechanics.

Amphibious fishes and salamanders are valuable functional analogs for vertebrates that spanned the water-land transition. However, investigations of walking mechanics have focused on terrestrial salamanders and, thus, may better reflect the capabilities of stem tetrapods that were already terrestrial. The earliest tetrapods were likely aquatic, so salamanders that are not primarily terrestrial may yield more appropriate data for modeling the incipient stages of terrestrial locomotion. In the present study, locomotor biomechanics were quantified from semi-aquatic Pleurodeles waltl, a salamander that spends most of its adult life in water, and then compared with those of a primarily terrestrial salamander (Ambystoma tigrinum) and a semi-aquatic fish (Periophthalmus barbarus) to evaluate whether terrestrial locomotion was more comparable between species with ecological versus phylogenetic similarities. Ground reaction forces (GRFs) from individual limbs or fins indicated that the pectoral appendages of each taxon had distinct patterns of force production, but GRFs from the hindlimbs were comparable between the salamander species. The rate at which force is produced can affect musculoskeletal function, so we also calculated 'yank' (first time derivative of force) to quantify the dynamics of GRF production. Yank was sometimes slower in P. waltl but there were some similarities between the three species. Finally, the semi-aquatic taxa (P. waltl and P. barbarus) had a more medial inclination of the GRF compared to terrestrial salamanders, potentially elevating bone stresses among more aquatic taxa and limiting their excursions onto land.

Modelling, simulation and experimental validation of wheel and arm locomotion based wall-climbing robot

AbstractThis article presents modelling, simulation, and development of a wall-climbing robot based on coupled wheel and arm-type locomotion mechanism. The developed robot consists of two mobile modules connected with a robot arm mechanism. The actuation of the robot arm is inspired by inchworm locomotion, particularly during wall-to-wall transition, obstacle avoidance, and uneven surface locomotion. Easiness in the interchanging of wheel to arm and vice versa makes the robot more effective compared to previously developed wall-climbing robots. The kinematic and dynamic model for the proposed coupled wheel and arm locomotion concept has been established. A combination of particle swarm optimization (PSO) and proportional, integral, derivatives (PID) feedback control algorithm has been developed using MATLAB to simulate the different cases of robot motions. The developed prototype of the wall-climbing robot is used to verify the coupled wheel and arm locomotion concept in various wall climbing scenarios. The simulation and experimental findings show good comparisons and validate the model-based design of the wall-climbing robot.

Electrically Controlled Aquatic Soft Actuators with Desynchronized Actuation and Light-Mediated Reciprocal Locomotion

Soft-bodied aquatic invertebrates can overcome hydrodynamic resistance and display diverse locomotion modes in response to environmental cues. Exploring the dynamics of locomotion from bioinspired aquatic actuators will broaden the perspective of underwater manipulation of artificial systems in fluidic environments. Here, we report a multilayer soft actuator design based on a light-driven hydrogel and a laser-induced graphene (LIG) actuator, minimizing the effect of the time delay by a monolithic hydrogel-based system while maintaining shape-morphing functionality. Moreover, different time scales in the response of actuator materials enable a real-time desynchronization of energy inputs, holding great potential for applications requiring desynchronized stimulation. This hybrid design principle is ultimately demonstrated with a high-performance aquatic soft actuator possessing an underwater walking speed of 0.81 body length per minute at a relatively low power consumption of 3 W. When integrated with an optical sensor, the soft actuator can sense the variation in light intensity and achieve mediated reciprocal motion. Our proposed locomotion mechanism could inspire other multilayer soft actuators to achieve underwater functionalities at the same spatiotemporal scale. The underwater actuation platform could be used to study locomotion kinematics and control mechanisms that mimic the motion of soft-bodied aquatic organisms.

Magnetic Nanomotors in Emulsions for Locomotion of Microdroplets.

The locomotion of droplets in emulsions is of practical significance for fields related to medicine and chemical engineering, which can be done with a magnetic field to move droplets containing magnetic materials. Here, we demonstrate a new method of droplet locomotion in the oil-in-water emulsion with the help of a nonuniform magnetic field in the case where magnetic nanoparticles (MNPs) are dispersed in the continuous phase of the emulsion. The paper analyses the motion of the droplets in a liquid film and in a capillary for various diameters of droplets, their number density, and viscosity of the continuous phase of the emulsion. It is established that the mechanism of droplet locomotion in the emulsion largely depends on the wettability of MNPs. Hydrophobic nanoparticles are adsorbed on the droplet surfaces, forming the agglomerates of MNPs with the droplets. Such agglomerates move at much higher velocities than passive droplets. Hydrophilic nanoparticles are not adsorbed at the surfaces of the droplets but form mobile magnetic clusters dispersed in the continuous phase of the emulsion. Mobile magnetic clusters set the surrounding liquid and droplets in motion. The results obtained in this paper can be used in drug delivery.

Characterization and Categorization of Various Human Lower Limb Movements Based on Kinematic Synergies.

A proper movement categorization reduces the complexity of understanding or reproducing human movements in fields such as physiology, rehabilitation, and robotics, through partitioning a wide variety of human movements into representative sub-motion groups. However, how to establish a categorization (especially a quantitative categorization) for various human lower limb movements is rarely investigated in literature and remains challenging due to the diversity and complexity of the lower limb movements (diverse gait modes and interaction styles with the environment). Here we present a quantitative categorization for the various lower limb movements. To this end, a similarity measure between movements was first built based on limb kinematic synergies that provide a unified and physiologically meaningful framework for evaluating the similarities among different types of movements. Then, a categorization was established via hierarchical cluster analysis for thirty-four lower limb movements, including walking, running, hopping, sitting-down-standing-up, and turning in different environmental conditions. According to the movement similarities, the various movements could be divided into three distinct clusters (cluster 1: walking, running, and sitting-down-standing-up; cluster 2: hopping; cluster 3: turning). In each cluster, cluster-specific movement synergies were required. Besides the uniqueness of each cluster, similarities were also found among part of the synergies employed by these different clusters, perhaps related to common behavioral goals in these clusters. The mix of synergies shared across the clusters and synergies for specific clusters thus suggests the coexistence of the conservation and augmentation of the kinematic synergies underlying the construction of the diverse and complex motor behaviors. Overall, the categorization presented here yields a quantitative and hierarchical representation of the various lower limb movements, which can serve as a basis for the understanding of the formation mechanisms of human locomotion and motor function assessment and reproduction in related fields.

Robust locomotor performance of squirrel monkeys (Saimiri boliviensis) in response to simulated changes in support diameter and compliance.

Arboreal environments require overcoming navigational challenges not typically encountered in other terrestrial habitats. Supports are unevenly distributed and vary in diameter, orientation, and compliance. To better understand the strategies that arboreal animals use to maintain stability in this environment, laboratory researchers must endeavor to mimic those conditions. Here, we evaluate how squirrel monkeys (Saimiri boliviensis) adjust their locomotor mechanics in response to variation in support diameter and compliance. We used high-speed cameras to film two juvenile female monkeys as they walked across poles of varying diameters (5, 2.5, and 1.25 cm). Poles were mounted on either a stiff wooden base ("stable" condition) or foam blocks ("compliant" condition). Six force transducers embedded within the pole trackway recorded substrate reaction forces during locomotion. We predicted that squirrel monkeys would walk more slowly on narrow and compliant supports and adopt more "compliant" gait mechanics, increasing stride lengths, duty factors, and an average number of limbs gripping the support, while the decreasing center of mass height, stride frequencies, and peak forces. We observed few significant adjustments to squirrel monkey locomotor kinematics in response to changes in either support diameter or compliance, and the changes we did observe were often tempered by interactions with locomotor speed. These results differ from a similar study of common marmosets (i.e., Callithrix jacchus, with relatively poor grasping abilities), where variation in diameter and compliance substantially impacted gait kinematics. Squirrel monkeys' strong grasping apparatus, long and mobile tails, and other adaptations for arboreal travel likely facilitate robust locomotor performance despite substrate precarity.

Motion of a chemically reactive bimetal motor in a magnetic field.

The wide research interest in nano-, micro-, and macromotors is due to the diverse range of applied problems in engineering, biomedicine, and ecology. At the same time, the amount of known mechanisms responsible for the locomotion of motors is limited. Here, we demonstrate a novel method of motor locomotion, which can be contingently called "chemical magnetism". The phenomenon considered here is based on the fact that any current loop in the magnetic field is affected by a force. "Chemical magnet" represents a bimetal surfer swimming at the electrolyte surface. When the redox reaction proceeds, a current loop emerges. That defines the action of the additional magnetic force on the surfer in the non-uniform magnetic field. The magnetic properties of the surfer can be varied in a wide range by changing the concentration of the electrolyte solution, its temperature, and the pair of metals composing the surfer. The phenomenon of "chemical magnetism" considered here widens a list of known mechanisms of motor locomotion.

Multimodal Locomotion and Cargo Transportation of Magnetically Actuated Quadruped Soft Microrobots.

Untethered microrobots have attracted extensive attention due to their potential for biomedical applications and micromanipulation at the small scale. Soft microrobots are of great research importance because of their highly deformable ability to achieve not only multiple locomotion mechanisms but also minimal invasion to the environment. However, the existing microrobots are still limited in their ability to locomote and cross obstacles in unstructured environments compared to conventional legged robots. Nature provides much inspiration for developing miniature robots. Here, we propose a bionic quadruped soft thin-film microrobot with a nonmagnetic soft body and 4 magnetic flexible legs. The quadruped soft microrobot can achieve multiple controllable locomotion modes in the external magnetic field. The experiment demonstrated the robot's excellent obstacle-crossing ability by walking on the surface with steps and moving in the bottom of a stomach model with gullies. In particular, by controlling the conical angle of the external conical magnetic field, microbeads gripping, transportation, and release of the microrobot were demonstrated. In the future, the quadruped microrobot with excellent obstacle-crossing and gripping capabilities will be relevant for biomedical applications and micromanipulation.

Upper-body haptic system for snake robot teleoperation in pipelines

Snake robots have shown a great potential for operations in confined workplaces that are less accessible or dangerous to human workers, such as the in-pipe inspection. However, the snake robot teleoperation remains a nontrivial task due to the unique locomotion mechanism (e.g., helical motion) and the constraints of the workplaces including the low visibility and indistinguishable features. Most snake robot feedback systems are based on the live camera view only. It is hard for the human operator to develop a correct spatial understanding of the remote workplace, leading to problems such as disorientation and motion sickness in snake robot teleoperation. This study designs and evaluates an innovative haptic assistant system for snake robot teleoperation in the in-pipe inspection. An upper-body haptic suit with 40 vibrators on both the front and back sides of the human operator was developed to generate haptic feedback corresponding to the bottom and up sides of the snake robot, transferring the egocentric sensation of the snake robot to the human operator. A human-subject experiment (n = 31) was performed to evaluate the efficacy of the developed system. The results indicate that the proposed haptic assistant system outperformed other feedback systems in terms of both task performance and subjective workload and motion sickness evaluations. It inspires new control and feedback designs for the future snake robot in industrial operations.

МЕТОД ОБЪЕКТНОГО МОДЕЛИРОВАНИЯ ПРИ РАЗРАБОТКЕ ПАТЕНТОСПОСОБНЫХ КОНСТРУКЦИЙ УЗЛОВ ТЯГОВОГО ПРИВОДА

Work objective is to develop a patentable design of locomotive traction drive mechanisms using the example of a suspension unit. Research methods: object modeling method, analytical methods for calculating dynamics of rolling stock. Research results and novelty: the design of the railway electric motor suspension unit, which will reduce costs in the course of maintenance and repair of a locomotive with a solid gear by increasing the reliability of the suspension unit parts, eliminating their wear, has been developed; a compensation coupling device has been devised. We will synthesize the object model of a technical system based on the identification of its typical structure by classifying technical systems. Conclusion: the application of the object modeling method together with the object model allows avoiding errors in the development of new designs of technical objects based on existing comparables and eliminates defects of the selected prototype. The use of the object modeling method makes it possible to synthesize patentable designs of the locomotive underframe mechanisms.

Magnetically Deployable Robots Using Layered Lamina Emergent Mechanism

The steady rise of deployable structures and mechanisms based on kirigami and origami principles has brought about design innovations that yield flexible and lightweight robots. These robots are designed based on desirable locomotion mechanisms and often incorporate additional materials to support their flexible structure to enable load-bearing applications and considerable efficient movement. One tetherless way to actuate these robots is via the use of magnets. This paper incorporates magnetic actuation and kirigami structures based on the lamina emergent mechanism (LEM). Three designs of magnetic-actuated LEMs (triangular prism, single LEM (SLEM), alternating mirror dual LEM (AMDLEM)) are proposed, and small permanent magnets are attached to the structures’ flaps or legs that rotate in response to an Actuating Permanent Magnet (APM) to yield stick-slip locomotion, enabling the robots to waddle and crawl on a frictional surface. For preliminary characterization, we actuate the three designs at a frequency of 0.6 Hz. We observed the triangular prism, SLEM, and AMDLEM prototypes to achieve horizontal speeds of 4.3 mm/s, 10.7 mm/s, and 12.5 mm/s on flat surfaces, respectively. We further explore how changing different parameters (actuation frequency, friction, leg length, stiffness, compressibility) affects the locomotion of the different mechanisms.

Light-powered soft steam engines for self-adaptive oscillation and biomimetic swimming.

Oscillation plays a vital role in the survival of living organisms in changing environments, and its relevant research has inspired many biomimetic approaches to soft autonomous robotics. However, it remains challenging to create mechanical oscillation that can work under constant energy input and actively adjust the oscillation mode. Here, a steam-driven photothermal oscillator operating under constant light irradiation has been developed to perform continuous or pulsed, damped harmonic mechanical oscillations. The key component of the oscillator comprises a hydrogel containing Fe3O4/Cu hybrid nanorods, which can convert light into heat and generate steam bubbles. Controllable perturbation to the thermomechanical equilibrium of the oscillator can thus be achieved, leading to either continuous or pulsed oscillation depending on the light intensity. Resembling the conventional heat steam engine, this environment-dictated multimodal oscillator uses steam as the working fluid, enabling the design of self-adaptive soft robots that can actively adjust their body functions and working modes in response to environmental changes. An untethered biomimetic neuston-like robot is further developed based on this soft steam engine, which can adapt its locomotion mechanics between uniform and recurrent swimming to light intensity changes and perform on-demand turning under continuous light irradiation. Fueled by water and remotely powered by light, this unique hydrogel oscillator enables easy control over the oscillation dynamics and modes, offering an effective approach to self-adaptive soft robots and solar steam engines.

Rotational Locomotion of an Active Gel Driven by Internal Chemical Signals.

Chemical waves arising from coupled reaction and transport can serve as biomimetic "nerve signals" to study the underlying origin and regulation of active locomotion. During wave propagation in more than one spatial dimension, the propagation direction of spiral and pulse waves in a nanogel-based PAAm self-oscillating gel, i.e., the orientation of the driving force, may deviate from the normal direction to the wave fronts. Alternating forward and backward retrograde wave locomotion along the normal and tangential kinematic vectors with a phase difference leads to a curved path, i.e., rotational locomotion. This work indicates that appendages in an organism are not required for this type of locomotion. This locomotion mechanism reveals a general principle underlying the dynamical origin of biological helical locomotion and also suggests design approaches for complex locomotion of soft robots and smart materials.

Metarpillar: Soft robotic locomotion based on buckling-driven elastomeric metamaterials

Mechanical instabilities are emerging as novel actuation mechanisms for the design of biomimetic soft robots and smart structures. The present study shows that by coupling buckling-driven elastomeric auxetic modules actuated by a negative air-pressure, a novel metamaterial-based caterpillar can be designed—the Metarpillar. Following a detailed analysis of the caterpillar’s locomotion, we were able to mimic both its crawling movement and locomotion by using the unique isometric compression of the modules and properly programing the anterograde modular peristaltic contractions. The bioinspired locomotion of the Metarpillar uses the bending triggered by the buckling-driven module contraction to control the friction through a dynamic anchoring between the soft robot and the surface, which is the main mechanism for locomotion in caterpillars and other crawling organisms. Thus, the Metarpillar not only mimics the locomotion of the caterpillar but also displays dynamic similarity and equivalent, or even faster, speeds. Our approach based on metamaterial buckling actuator units opens up a novel strategy for biomimetic soft robotic locomotion that can be extended beyond caterpillars.

Bariatric surgery on obese walking: mass(ive) changes akin to load carrying and hypogravity for normal-weight adults.

Bariatric surgery on obese walking: mass(ive) changes akin to load carrying and hypogravity for normal-weight adults.