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Achieving high-performance dynamic behavior in a robot requires careful design of morphology. However, searching for a global optimum morphology in an intensely nonlinear design space is difficult, especially if stochastic seeding is used. In contrast to optimization, we encode design requirements into a polynomial system with a huge number of isolated roots. Each root describes an alternate robot morphology in the design space. Following this, the computation of nearly all isolated roots constitutes design space exploration. Previously, these systems were intractable, due to the heavy burden of degenerate roots. We relieve this burden by using the finite root generation (FRG) method to enable the discovery of nearly all isolated roots for a certain six-bar design problem for the first time. The FRG synthesis method enables the design of a transmission function from motor dynamics to a loaded end effector to influence the overall dynamic behavior. In an example, we formulate synthesis equations which were previously intractable, obtain 1 528 608 isolated roots (estimated 99.0%), and find 3764 physical designs. Design options are compared according to their sensitivity to joint errors. [ABSTRACT FROM AUTHOR]

This paper presents “1STAR,” which is the first robot that is driven by a single actuator but can be directly commanded to move straight or turn clockwise or counterclockwise. The legged robot relies on a novel actuation gait, which exploits the compliance disparity between alternate stance tripods, to generate rotation by continuously accelerating and decelerating the legs. The direction of turning depends on the configuration of the legs—tripod left or right—and the timing of the acceleration and deceleration. Alternating leg acceleration in successive steps allows for continuous rotation in the desired direction. The turning radius can be varied by changing the timing of the leg acceleration and deceleration without changing the cycle frequency and linear speed. A simplified kinematic motion model of a robot is presented, and a dynamic simulation is performed to analyze the behavior and optimize robot parameters. The locomotion gait is verified experimentally using our newly designed “1STAR” robot. [ABSTRACT FROM PUBLISHER]

Biologically inspired adhesives developed for switchableand controllableadhesion often require repetitive uses in general, dirty, environments.Superhydrophobic microstructures on the lotus leaf lead to exceptionalself-cleaning of dirt particles on nonadhesive surfaces with waterdroplets. This paper describes the self-cleaning properties of a hard-polymer-basedadhesive formed with high-aspect-ratio microfibers from high-densitypolyethylene (HDPE). The microfiber adhesive shows almost completewet self-cleaning of dirt particles with water droplets, recovering98% of the adhesion of the pristine microfiber adhesives. The lowcontact angle hysteresis indicates that the surface of microfiberadhesives is superhydrophobic. Theoretical and experimental studiesreveal a design parameter, length, which can control the adhesionwithout affecting the superhydrophobicity. The results suggest someproperties of biologically inspired adhesives can be controlled independentlyby adjusting design parameters. [ABSTRACT FROM AUTHOR]

Electrical contact resistance can be reduced using an array of compliant and conductive nanowires which make a large area of intimate contact with an opposing surface. In this paper, analyses of electrical contact resistance, fabrication methods, and experimental results of contact resistance for compliant nickel nanowires are presented. To analyze, predict, and measure the contact resistance, models of surface contact between an array of conductive nanowires and a spherical tip probe are presented. Then, an estimate of real area of contact from the measured contact resistance is discussed. The fabrication methods elaborate on electroforming nickel fibers using commercially available nano-porous filters. Finally, experimental results of contact resistance between a spherical tip probe and arrays of nickel nanowires as well as the contact resistance between a fiat tip probe and arrays of nickel nanowires are presented. From these experimental results, we show resistance reduction by a factor of more than 20 at a load of 10 mN or less, compared to contact with a fiat sheet, and a reduction by a factor of 3 using a spherical probe. [ABSTRACT FROM AUTHOR]

This paper proposes techniques to fabricate synthetic gecko foot-hairs as dry adhesives for future wall-climbing and surgical robots, and models for understanding the synthetic hair design issues. Two nanomolding fabrication techniques are proposed: the first method uses nanoprobe indented flat wax surface and the second one uses a nano-pore membrane as a template. These templates are molded with silicone rubber, polyimide, etc. type of polymers under vacuum. Next, design parameters such as length, diameter, stiffness, density, and orientation of hairs are determined for non-matting and rough surface adaptability. Preliminary micro/nano-hair prototypes showed adhesion close to the predicted values for natural specimens (around 100 nN each). [ABSTRACT FROM AUTHOR]

Presents a novel approach to the Acrobot control problem. Concept of the proposed tracking controller; Exact trajectories of the nonlinear equations of motion; Proposed nonlinear control law; Comparison between the proposed controller and one based on pseudolinearization.

Provides information on a planar hopping robot which has only one actuated joint for use in the manufacturing process. Information on the control-strategies for the two-link robot; Details on the sliding and hopping gait; Description of the simulation results.

In order for a robot hand to grasp objects stably without using object models, tactile feedback from the fingers is sometimes necessary. This feedback can be used to adjust grasping forces to prevent a part from slipping from a hand. If the angle of force at the object-finger contact can be determined, slip can be prevented by the proper adjustment of finger forces. Another important tactile sensing task is finding the edges and corners of an object since they are usually feasible grasping locations. This paper describes how this information can be extracted from the finger-object contact using strain sensors beneath a compliant skin. For determining contact forces, strain measurements are easier to use than the surface deformation profile. The finger is modeled as an infinite linear elastic half-plane to predict the measured strain for several contact types and forces. The number of sensors required is less than has been proposed for other tactile recognition tasks. A rough upper bound on sensor density requirements for a specific depth is presented that is based on the frequency response of the elastic medium. The effects of different sensor stiffnesses on sensor performance are discussed. [ABSTRACT FROM AUTHOR]

Arrays of angled microfibers with a gecko-inspired structure were fabricated from a stiff thermoplastic polymer (polypropylene) with elastic properties similar to those of β-keratin of natural setae. Friction experiments demonstrated that this fibrillar polymer surface exhibits directional adhesion. Sliding of clean glass surfaces against and along the microfiber direction without applying an external normal force produced an apparent shear stress of 0.1 and 4.5 N/cm2, respectively. This directional adhesion is interpreted in the context of a nonlinear elastic bending model of an angled beam. Shearing and normal contact experiments yielded further evidence of the anisotropic adhesion of the fibrillar polymer and revealed the occurrence of a pull-off (adhesive) force at the instant of surface detachment, unlike vertically aligned microfiber arrays of the same material that exhibited a zero pull-off force. The results of this study provide impetus for the design of gecko-inspired adhesives with angled structures that demonstrate directional adhesion against different material surfaces. [ABSTRACT FROM AUTHOR]

Very slender cylindrical fibers are capable of bending over and maintaining side contact with an opposing substrate even as the fibers are pulled away, providing a mode of adhesion for fiber array adhesives. This paper analyzes side contact and its effect on normal adhesion and provides guidelines for fiber length to achieve side contact under zero load as a function of elastic modulus, area moment of inertia, initial geometry, and energy of adhesion between fiber and substrate. Numerical results for several relevant geometries are presented as well as a comparison to recently reported normal adhesion measurements of multiwalled carbon nanotube arrays. [ABSTRACT FROM AUTHOR]

We demonstrate thin-film repulsive-force electrostatic actuators that employ a new electrode pattern and are useful for low-force actuation applications. Compared to prior patterns, the new electrode geometry increases electrostatic force production by an order of magnitude (at equal voltages) and eliminates the most common shorting failure modes. These electrostatic actuators have stable open-loop operation with no pull-in instability, low mechanical hysteresis, and peak force in rest configurations. The actuators are fabricated with a planar, flex-circuit manufacturing process, allowing production at scale and over large areas. Two-layer out-of-plane linear actuators (25 × 10 mm electrode area) were characterized: with 0–1000 V inputs (40 × 10 6  V/m), blocked normal forces of 9.03 mN (36.1 Pa) were generated, and controllable linear displacements up to 511 μm were measured across an open loop bandwidth of 43 Hz. Finally, we present a 290 mg 1-DoF micro-mirror system for laser beam steering that employs a two-layer out-of-plane rotational actuator for open-loop stable operation with controlled angular displacements up to 5.1° at 1000 V/16 Hz. [ABSTRACT FROM AUTHOR]

Terrestrial animals and robots are susceptible to flipping-over during rapid locomotion in complex terrains. However, small robots are less capable of self-righting from an upside-down orientation compared to small animals like insects. Inspired by the winged discoid cockroach, we designed a new robot that opens its wings to self-right by pushing against the ground. We used this robot to systematically test how self-righting performance depends on wing opening magnitude, speed, and asymmetry, and modeled how kinematic and energetic requirements depend on wing shape and body/wing mass distribution. We discovered that the robot self-rights dynamically using kinetic energy to overcome potential energy barriers, that larger and faster symmetric wing opening increases self-righting performance, and that opening wings asymmetrically increases righting probability when wing opening is small. Our results suggested that the discoid cockroach’s winged self-righting is a dynamic maneuver. While the thin, lightweight wings of the discoid cockroach and our robot are energetically sub-optimal for self-righting compared to tall, heavy ones, their ability to open wings saves them substantial energy compared to if they had static shells. Analogous to biological exaptations, our study provided a proof-of-concept for terrestrial robots to use existing morphology in novel ways to overcome new locomotor challenges. [ABSTRACT FROM AUTHOR]

Particle capture and release using controllable adhesion is of growing interest in many fields including reusable adhesives, solar panel cleaning, micro-manipulation and robot locomotion where current methods of particle management are not sufficient. Here controllable adhesion to glass spheres with a new magnetically actuated synthetic gecko adhesive made from a magnetoelastomer composite is demonstrated. Adhesion is controlled by changing the effective elastic modulus of the surface through actuation of micro surface features with an external magnetic field. A compliant mechanics and magnetic torque analysis explains this general principle and generalizes the results for various geometries. Results show sphere pull-off forces can be increased 10-fold by changing the ridge orientation via the external magnetic field, and that the effective elastic modulus can be changed from 65 kPa to 1.5 MPa. Particle transport and release of 500- and 1000-micrometer glass spheres is also demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, an efficient charge recovery method for driving piezoelectric actuators with low frequency square waves in low-power applications such as mobile microrobots is investigated. Efficiency issues related to periodic mechanical work of the actuators and the relationship among the driving electronics efficiency, the piezoelectric coupling factor, and the actuator energy transmission coefficient are discussed. The proposed charge recovery method exploiting the energy transfer between an inductor and a general capacitive load is compared with existing techniques that lead to inherent inefficiencies. A charge recovery method is then applied to piezoelectric actuators, especially to bimorph ones. Unitary efficiency can be obtained theoretically for purely capacitive loads while intrinsic losses such as hysteresis necessarily lower the efficiency. In order to show the validity of the method, a prototype driving electronics consisting of an extended H-bridge is constructed and tested by experiments and simulations. Preliminary results show that 75% of charge (i.e., more than 56% of energy) can be recovered for bending actuators such as bimorphs without any component optimization at low fields. [ABSTRACT FROM AUTHOR]

This paper presents a novel fabrication method for producing high-aspect-ratio, angled polymer microfiber arrays by directional pulling of polyethylene from low-aspect-ratio, microporous polycarbonate templates. These arrays represent a novel substrate for electrostatic sensors and actuators because they are characterized by low stiffness (<24 kPa effective elastic modulus), low Poisson's ratio (effectively zero at low strains), and very low density (<1% of solid polyethylene). Validation of these properties is presented by developing a model based on elastica theory, and by performing experiments using a parallel-plate electrostatic actuator fabricated with a fiber array as the dielectric and return spring. [ABSTRACT FROM AUTHOR]

On page 3256, Andrew G. Gillies and co‐workers describe a gecko synthetic adhesive surface fabricated with magneto‐elastomer microridges, which can be controlled remotely with an external magnetic field. By changing the microridge configuration, adhesion can be switched on and off to selectively capture and release particles. [ABSTRACT FROM AUTHOR]

The role in adhesion of the toes and lamellae - intermediate-sized structures - found on the gecko foot remains unclear. Insight into the function of these structures can lead to a more general understanding of the hierarchical nature of the gecko adhesive system, but in particular how environmental topology may relate to gecko foot morphology. We sought to discern the mechanics of the toes and lamellae by examining gecko adhesion on controlled, macroscopically rough surfaces. We used live Tokay geckos, Gekko gecko, to observe the maximum shear force a gecko foot can attain on an engineered substrate constructed with sinusoidal patterns of varying amplitudes and wavelengths in sizes similar to the dimensions of the toes and lamellae structures (0.5 to 6 mm). We found shear adhesion was significantly decreased on surfaces that had amplitudes and wavelengths approaching the lamella length and inter-lamella spacing, losing 95% of shear adhesion over the range tested. We discovered that the toes are capable of adhering to surfaces with amplitudes much larger than their dimensions even without engaging claws, maintaining 60% of shear adhesion on surfaces with amplitudes of 3 mm. Gecko adhesion can be predicted by the ratio of the lamella dimensions to surface feature dimensions. In addition to setae, remarkable macroscopic-scale features of gecko toes and lamellae that include compliance and passive conformation are necessary to maintain contact, and consequently, generate shear adhesion on macroscopically rough surfaces. Findings on the larger scale structures in the hierarchy of gecko foot function could provide the biological inspiration to drive the design of more effective and versatile synthetic fibrillar adhesives. [ABSTRACT FROM AUTHOR]

We present a study on macroscalefriction of polyethylene nanofibrillararrays against patterned rough surfaces with various asperity heights,spacings, and area fractions. These surfaces are prepared by utilizingcolloidal lithographyand silica evaporation, which allows the independent control of geometricparameters. While the nanofiber arrays exhibit high friction on asmooth surface, much lower friction is observed when the asperityheight becomes larger than can be compensated by fiber compliance,or when the asperity spacing becomes small enough to prevent fiberpenetration for contact. The observed behavior is discussed with simplemechanical models and summarized to provide some criteria to maintainhigh friction against rough surfaces. [ABSTRACT FROM AUTHOR]

We study the locomotor mechanics of a small, lightweight robot (DynaRoACH, 10 cm, 25 g) which can move on a granular substrate of 3 mm diameter glass particles at speeds up to 5 body length/s, approaching the performance of certain desert-dwelling animals. To reveal how the robot achieves this performance, we used high-speed imaging to capture its kinematics, and developed a numerical multi-body simulation of the robot coupled to an experimentally validated simulation of the granular medium. Average speeds measured in experiment and simulation agreed well, and increased nonlinearly with stride frequency, reflecting a change in propulsion mode. At low frequencies, the robot used a quasi-static “rotary walking” mode, in which the substrate yielded as legs penetrated and then solidified once vertical force balance was achieved. At high frequencies the robot propelled itself using the speed-dependent fluid-like inertial response of the material. The simulation allows variation of parameters which are inconvenient to modify in experiment, and thus gives insight into how substrate and robot properties change performance. Our study reveals how lightweight animals can achieve high performance on granular substrates; such insights can advance the design and control of robots in deformable terrains. [ABSTRACT FROM AUTHOR]

The effect of counter-substrate surface energy on macroscalefrictionof nanofiber array is studied. Low-density polyethylene (LDPE) fibrillararray fabricated from silicon nanowire template is tested againstglass substrates modified with various self-assembled monolayers,which exhibit a wide range of surface energy. A large drop in frictionover a narrow range of surface energy is observed and explained interms of drastically reduced number of fibers in actual contact, inaddition to the reduced surface energy. The relationship between surfaceenergy and fiber engagement is discussed with Johnson–Kendall–Roberts(JKR) and elastic beam models. [ABSTRACT FROM AUTHOR]

Large-scale integration of high-performance electronic components on mechanically flexible substrates may enable new applications in electronics, sensing and energy. Over the past several years, tremendous progress in the printing and transfer of single-crystalline, inorganic micro- and nanostructures on plastic substrates has been achieved through various process schemes. For instance, contact printing of parallel arrays of semiconductor nanowires (NWs) has been explored as a versatile route to enable fabrication of high-performance, bendable transistors and sensors. However, truly macroscale integration of ordered NW circuitry has not yet been demonstrated, with the largest-scale active systems being of the order of 1 cm2 (refs 11,15). This limitation is in part due to assembly- and processing-related obstacles, although larger-scale integration has been demonstrated for randomly oriented NWs (ref. 16). Driven by this challenge, here we demonstrate macroscale (7×7 cm2) integration of parallel NW arrays as the active-matrix backplane of a flexible pressure-sensor array (18×19 pixels). The integrated sensor array effectively functions as an artificial electronic skin, capable of monitoring applied pressure profiles with high spatial resolution. The active-matrix circuitry operates at a low operating voltage of less than 5 V and exhibits superb mechanical robustness and reliability, without performance degradation on bending to small radii of curvature (2.5 mm) for over 2,000 bending cycles. This work presents the largest integration of ordered NW-array active components, and demonstrates a model platform for future integration of nanomaterials for practical applications. [ABSTRACT FROM AUTHOR]

Conventional connectors utilize mechanical, magnetic, or electrostatic interactions to enable highly specific and reversible binding of the components (i.e., mates) for a wide range of applications. As the connectors are miniaturized to small scales, a number of shortcomings, including low binding strength, high engagement/disengagement energies, difficulties with the engagement, fabrication challenges, and the lack of reliability are presented that limit their successful operation. Here, we report unisex, chemicalconnectors based on hybrid, inorganic/organic nanowire (NW) forests that utilize weak van der Waals bonding that is amplified by the high aspect ratio geometric configuration of the NWs to enable highly specific and versatile binding of the components. Uniquely, NW chemicalconnectors exhibit high macroscopic shear adhesion strength (∼163 N/cm2) with minimal binding to non-self-similar surfaces, anisotropic adhesion behavior (shear to normal strength ratio ∼25), reusability (∼27 attach/detach cycles), and efficient binding for both micro- and macroscale dimensions. [ABSTRACT FROM AUTHOR]

Fault diagnosis is critical for intelligent manufacturing by monitoring the status of a production line and preventing financial loss. Model-based fault diagnosis has the advantage of being able to explain the cause and propagation of faults over model-free diagnosis, but would need knowledge about the configuration model and context-specific information of the production line. Ontology modelling can provide context-specific information on top of a configuration model to benefit fault diagnosis. Typically ontologies are manually constructed and then used by a reasoner based on a set of predefined rules. From the perspective of fault diagnosis, this approach works as an expert system where both the ontology models and predefined rules are specific to a given system. Once the system has changed which happens from time to time as repairs and updates in a production line, or in the case of a different system, the ontology models and predefined rules would need to be manually modified or reconstructed. Here a model-based method is proposed to automate generation of configuration models with context-specific information using semantic web technology when a production line is healthy, and to use the generated configuration model and information for diagnosis when the production line has a fault. The method does not rely on predefined rules and reasoners, but rather uses dynamics models that are based on first-principle qualitative mechanics. It uses numerical optimization to minimize the discrepancy between sensor data from the production line and from simulation running the dynamics model to achieve automatic configuration modelling and fault diagnosis. With three use cases commonly found for a production line, i.e. automatic sensor placement modeling or misplacement diagnosis, motor fault diagnosis with single sensor modality, and motor fault diagnosis with sensory substitution, the feasibility of the proposed method is demonstrated. The method's faster computational speed and comparable accuracy to a quantitative model-based approach suggests it may complement and accelerate the latter with early-stage selection of candidate models for both modelling and fault diagnosis. [ABSTRACT FROM AUTHOR]