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In order to characterize the mechanical behavior of fragile resonant microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS), nondestructive measurements are required. In this paper, a cartography of local stiffness variations on a suspended micromembrane is established for the first time, by a tuning-fork-based dynamic force sensor inside a scanning electron microscope (SEM). Experiments are conducted individually on a batch of InP membranes 200  nm thin, using a 9-degree-of-freedom (dof) nanomanipulation system, complemented with virtual reality and automation tools. Results provide stiffness values in the range of a few newton per meter, with variations in a single sample depending on the membrane models. [ABSTRACT FROM PUBLISHER]

In this paper, we present KULEX-hand, a novel underactuated hand exoskeleton for grasping power assistance for patients having a partially paralyzed hand or the elderly with weakened muscle strength. This mechanism consists of an underactuated finger for grasp motion generation, a spherical four-bar linkage for power transmission, and a passive thumb link with a flexure hinge structure. Based on the natural closing motion of the human index finger, the motion generation linkage was synthesized as a planar five-bar in which two input links were coupled with a four-bar linkage. Therefore, after contact occurs on the proximal link, the synthesized linkage can mimic the grasping motion of the human middle and distal phalanges. The kinetoelastic relation of the underactuated finger was derived using the theory of screws. Based on this relation, guidelines were proposed for selecting the springs for achieving a stable pinch grasp. A prototype was designed, and the naturalness of motion was evaluated from an experiment with five subjects. [ABSTRACT FROM AUTHOR]

Soft actuators comprised of fluidic structures with fiber-reinforced elastomeric enclosures are seen throughout nature, exhibiting strength, power density, resilience, and diverse motions and forces. However, these structures are rarely used by engineers, in part due to the absence of a generalized understanding of their kinematics and forces. A small subset of soft actuators generating only extension or compression, popularly known as McKibben actuators, has been thoroughly investigated. This paper introduces the entire design space of actuators built with two families of fibers, of which McKibben actuators occupy a subset. The helix angle of the actuator's translation and rotation deformation is determined from the kinematics of the fiber deformation for all fiber angles as the actuator is pressurized. The volumetric transduction of the actuators, relating the output motion to change in contained volume, is analytically determined. The results are discretized to provide a designer with an easy to use design selection chart. The kinematics, force, and moment of the actuators are experimentally validated for all fiber angles. [ABSTRACT FROM PUBLISHER]

This paper presents an alternative decomposition of spatial stiffness matrices based on the concept of compliant axes. According to the congruence transformation of spatial stiffness, the coordinate-invariant aspects, which are referred to as the central principal components of the $6\times 6$ symmetric positive semidefinite matrices, can be derived uniquely. The proposed decomposition is free from the eigenvalue problems of the $6\times 6$ stiffness matrices so that both Plücker's ray and axis coordinates can be utilized to characterize the elastic system's force–deflection behavior. Hence, an arbitrary spatial stiffness matrix can be uniquely decomposed into two sets of orthogonal spring wrenches with finite and infinite pitches, respectively. The decomposed wrenches with finite pitches correspond to the stiffness’ wrench-compliant axes, along which linear deformations produce only wrenches parallel to them. As a result, three torsional and three screw springs are required, at the most, to realize a given spatial stiffness. Using the principal axes decomposition, some physical appreciations, such as the center of stiffness, the wrench-compliant axes, and the correspondence of compliance and stiffness, can be derived to reveal the inherent structure of spatial stiffness in an intuitive manner. In order to verify the effectiveness of the proposed method, two numerical examples are intensively studied with comparison to the eigenscrew decomposition. In addition, a potential application of the proposed stiffness decomposition method is also provided for the structural compliance modeling of flexible links in robot manipulators. [ABSTRACT FROM PUBLISHER]

A high-precision pointing mechanism for intersatellite optical communication is presented in this paper, which employs flexure hinges as the passive joints and orients its moving platform by means of six piezoelectric actuators. The proposed mechanism features submicroradian resolution and microradian repeatability within a submilliradian pointing range. A corner-filleted flexure hinge considering manufacturing tolerance with high motion accuracy and large displacement is designed based on performance analysis, and the theoretical analysis is also validated by FEA simulation and experimental testing within a 5% error margin. The parameters of the parallel mechanism are synthesized by multiobjective optimization on the basis of inverse kinematics model. Moreover, the workspace determination and the FEA analysis of the optimized mechanism are also performed. Finally, a high-precision pointing prototype is fabricated and the performance testing has been implemented, which validate the effectiveness of the proposed system. [ABSTRACT FROM PUBLISHER]

When moving an object endowed with continuous symmetry, an ambiguity arises in its underlying rigid body transformation, induced by the arbitrariness of the portion of motion that does not change the overall body shape. The functional redundancy caused by continuous symmetry is ubiquitously present in a broad range of robotic applications, including robot machining and haptic interface (revolute symmetry), remote center of motion devices for minimal invasive surgery (line symmetry), and motion modules for hyperredundant robots (plane symmetry). In this paper, we argue that such functional redundancy can be systematically resolved by resorting to symmetric subspaces (SSs) of the special Euclidean group $\mathrm{SE}(3)$ , which motivates us to systematically investigate the structural synthesis of SS motion generators. In particular, we develop a general synthesis procedure that allows us to generate a wide spectrum of novel mechanisms for use in the applications mentioned. [ABSTRACT FROM AUTHOR]

This paper addresses the realization of spatial elastic behavior with a parallel or a serial manipulator. Necessary and sufficient conditions for a manipulator (either parallel or serial) to realize a specific elastic behavior are presented and interpreted in terms of the manipulator geometry. These conditions completely decouple the requirements on component elastic properties from the requirements on mechanism kinematics. New construction-based synthesis procedures for spatial elastic behaviors are developed. With these synthesis procedures, one can select each elastic component of a parallel (or serial) mechanism based on the geometry of a restricted space of allowable candidates. With each elastic component selected, the space of allowable candidates is further restricted. For each stage of the selection process, the geometry of the remaining allowable space is described. [ABSTRACT FROM AUTHOR]

In this paper, we develop a new type of snake-like robot using screw-drive units that are connected by active joints. The screw-drive units enable the robot to generate propulsion on any side of the body in contact with environments. Another feature of this robot is the omnidirectional mobility by combinations of screws’ angular velocities. We also derive a kinematic model and apply it to trajectory tracking control. Furthermore, we design a front-unit-following controller, which is suitable for manual operations. In this control system, operators are required to command only one unit in the front; then, commands for the rest of the units are automatically calculated to track the path of the preceding units. Asymptotic convergence of the tracking error of the front-unit-following controller is analyzed based on a Lyapunov approach for the case of constant curvature. The effectiveness of the control method is demonstrated by numerical examples and experiments. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel kinematic-based framework for collision detection and estimation of contact location along multisegment continuum robots. Screw theory is used to define a screw motion deviation (SMD) as the distance between the expected and the actual instantaneous screw axis (ISA) of motion. The expected ISA is computed based on the unconstrained kinematics model of the robot, while the actual ISA is computed based on sensory information. Collisions with rigid environments at any point along the robot are detected by monitoring the SMD. Contact locations are estimated by the minimization of the SMD between the ISA that is obtained from a constrained kinematic model of the continuum robot and the one that is obtained from sensor data. The proposed contact detection and localization methods only require the relative motion of each continuum segment with respect to its own base. This strategy allows the straightforward generalization of these algorithms for an n -segment continuum robot. The framework is evaluated via simulations and experimentally on a three-segment multibackbone continuum robot. Results show that the collision-detection algorithm is capable of detecting a single collision at any segment, multiple collisions occurring at multiple segments, and total-arm constraint. It is also shown that the estimation of contact location is possible at any location along the continuum robot with an accuracy better than 20% of the segment nominal length. We believe this study will enhance manipulation safety in unstructured environments and confined spaces. [ABSTRACT FROM PUBLISHER]

It has been mathematically proven that a completely restrained n- degree-of-freedom (n-DOF) single rigid-bodied cable-driven platform requires a minimum of n + 1 cables with positive tension to fully constrain it. However, the force-closure analysis of open chains that are driven by cables is still an open question. For the case of an n -DOF cable-driven open chain, the following two important questions arise. 1) How can the force-closure analysis be carried out for a given cable routing configuration, while retaining the geometric insights of the problem? 2) Are n + 1 cables sufficient to fully constrain the entire chain? This paper addresses these issues by proposing a systematic and novel approach based on the reciprocal screw theory. The key idea is to express wrenches acting on the open chain as linear combinations of the reciprocal screws and determine the total required torques at each joint. This is followed by equating the joint torques that are provided by the cable forces with the joint torques, which are required by the external wrenches, and checking for force closure. The proposed methodology can analyze open chains with arbitrary cable routing configuration. The analysis shows that the entire n-DOF open chain requires a minimum of n + 1 cables to fully constrain it. [ABSTRACT FROM PUBLISHER]

This paper presents a general and systematic approach to formulate the dimensionally homogeneous Jacobian, which is an important issue for the dexterity evaluation and dimensional synthesis of f-degrees-of-freedom (DOF) (f ≤ 6) parallel manipulators having mixed rotational and translational movement capabilities. By the utilization of f independent coordinates to describe the specified motion types of the platform, the f × f dimensionally homogeneous Jacobian is derived directly from the generalized Jacobian, provided that the manipulator has only one type of actuator. The condition number of the new Jacobian is then employed to evaluate the dexterity of two typical 3-DOF parallel manipulators as an illustration of the effectiveness of this approach. [ABSTRACT FROM AUTHOR]

In this paper, a novel soft inflatable arm is proposed for telepresence robots. The new proposed structure of the arm is achieved by a very common and low-cost inflatable material and it is very light, weighing only about 50 g. However, it can realize agile movement by driving six tiny cables installed in the shoulder and elbow joints. The soft inflatable arm can work by pumping air at a very low pressure ($7.32 \pm 3.45$ kPa) and allows direct and soft human contact without any external force sensors. This paper proposes joint compressed models, joint kinematic models, and kinematic models for the whole inflatable robot arm. These models can be easily applied to multijoint arms. In addition, a new redundancy resolution method is also developed for the inflatable arm, which makes it easier to control resolution and is less complex than other traditional approaches. Numerous experiments have been conducted, including performances of accuracy, repeatability, motion trajectories, human-safe interaction, and remote interaction. Results are satisfactory and validate the expected performance of the proposed robotic arm. [ABSTRACT FROM PUBLISHER]

Presents corrections to references in the above name paper. [ABSTRACT FROM AUTHOR]

This paper presents the design, analysis, and characterization of a compliant thoracic mechanism that saves inertial power for flapping-wing micro air vehicles. Lightweight polyimide film hinges were previously integrated into a compliant flapping-wing mechanism to reduce friction. However, these were not stiff enough to fully recover wing's inertial energy into elastic energy. To store adequate elastic energy using film hinges, we develop a compliant thoracic mechanism with nonlinear stiffness characteristics by mimicking a Dipteran insect's flight thorax. This thoracic mechanism consists of rigid plates and polyimide film hinges connected to form a closed shell structure. It has a nonlinearly increasing stiffness so that it can slow the wings down rapidly toward the end stroke and subsequently help reverse the wings. It demonstrates almost full recovery of inertial power for 10-cm span flapping wings up to 25 Hz. As a result, it only expends 2% of the total mechanical power on inertial power at 25 Hz. In contrast, the rigid-body mechanism with no elastic storage expends 23% of the total mechanical power on inertial power when the same wings beat at the same frequency. With the capability of elastic energy storage, this compliant thoracic mechanism saves power expenditure ranging from 20 up to 30% to produce the same thrust, in comparison with the rigid-body flapping mechanism. This study shows that power saving is effective only if elastic energy storage is well tuned to recover the wing inertial power. [ABSTRACT FROM AUTHOR]

Piezoelectric stack actuators have the advantages of zero backlash and no acoustic noise, but their stroke is too small to actuate robotic links directly. Because the force available is often more than the required, the stroke of the piezoelectric stack can be amplified by a compliant mechanism at the expense of force. It is not always clear what the geometry of this compliant mechanism should be. Compliant mechanisms have parallels in biology in that they describe two-way interactions between the actuator and the environment. In this paper, we employ the concept of a two-port network model from circuit theory to describe this two-way interaction and present a method to obtain each element of the two-port model as an analytical function of physical geometric parameters for a wide class of geometries. This method makes use of Castigliano’s theorem and Euler–Bernoulli linearly elastic beam theory. To our knowledge, this is the first two-port representation of a compliant mechanism that is based on analytical expressions of geometric parameters. This analytical model agrees well with finite-element method calculations. We also examine a representative case experimentally and achieve accuracies better than 18%. [ABSTRACT FROM AUTHOR]

In this paper, a novel concept of two-degree-of-freedom (2-DOF) compliant forceps is suggested for the measure of pulling and grasp forces at the tip of surgical instrument for minimally invasive surgery robot. For the design of the compliant forceps, the required compliance characteristics are first defined using a simple spring model with one linear and one torsional springs. This model may be directly realized as the compliant forceps. However, for the compact realization of the mechanism, we synthesize the spring model with two torsional springs that has equivalent compliance characteristics to the linear-torsional spring model. Then, each of the synthesized torsional springs is realized physically by means of a flexure hinge. From this design approach, direct measurement of the pulling and grasp forces is possible at the forceps, and measuring sensitivity can be adjusted in the synthesis process. The validity of the design is evaluated by finite element analysis. Further, from the measured values of bending strains of two flexure hinges, a method to compute the decoupled pulling and grasp forces is presented via the theory of screws. Finally, force-sensing performance of the proposed compliant forceps is verified from the experiments of the prototype using some weights and load cells. [ABSTRACT FROM AUTHOR]

Drawing on screw theory and the virtual joint method, this paper presents a general and hierarchical approach for semianalytical stiffness modeling of parallel mechanisms. The stiffness model is built by two essential steps: 1) formulating the map between the stiffness matrices of platform and limbs using the duality of wrench and twist of the platform; and 2) formulating the map between stiffness matrices of a limb and a number of elastic elements in that limb using the duality of the wrench attributed to the limb and the twist of the endlink of that limb. By merging these two threads, the Cartesian stiffness matrix can be explicitly expressed in terms of the compliance matrices of joints and links. The proposed approach bridges the gap between two currently available approaches and is thereby very useful for evaluating stiffness over the entire workspace and investigating the influences of joint/link compliances on those of the platform in a quick and precise manner. A stiffness analysis for a 3-PRS parallel mechanism is presented as an example to illustrate the effectiveness of the proposed approach. [ABSTRACT FROM PUBLISHER]

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 article, we present a novel approach that combines snakelike 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, multidomain, navigation capabilities. These tests show a wide breadth of scenarios that ARCSnake can handle, hence demonstrating its ability to traverse through extreme terrains. [ABSTRACT FROM AUTHOR]

This article develops a mechanical screwing tool and its manipulation policies for two-finger parallel robotic grippers. The tool is based on a combined scissor-like element (SLE) and double-ratchet mechanism that converts the gripping motion of two-finger parallel grippers into a continuous rotation to realize tasks like fastening screws. The tool is entirely mechanical. There is no need for external cable connections. The manuscript includes two parts. For one thing, it shows the details of the tool design, optimizes the tool’s dimensions and effective stroke lengths, and studies the contacts and forces to achieve stable grasping and screwing. For another, it presents the related manipulation and control policies, including recognizing the tool, changing tool poses, and completing screw fastening tasks. The designed tool, together with the related manipulation and control policies, are analyzed and verified in several real-world applications. The results show that the tool has satisfying mechanical properties. Robots with parallel grippers can robustly and flexibly use the tool to fasten screws. The tool can also be used collaboratively with other tools to finish difficult tasks. In the future, similar tools are expected to replace special-purpose end-effectors or tool changers for more flexible robot integration. [ABSTRACT FROM AUTHOR]

Origami structures can transform their form and function by changing the direction of their folds. This reconfiguration can enable multifunctional robots, but doing so requires a fast, robust, and repeatable actuation method. In this article, we present an origami gripper that uses dynamic transformation to change its kinematic behavior in less than a second. We characterize individual vertices to show that the transformation is predictable and repeatable for different designs and orientations. We then apply it to a multivertex template that is capable of a wide range of shapes and motion patterns, indicating that transformation can be generalized to complex and functional machines. To demonstrate this, we built a transforming origami gripper on a robotic arm to pick up multiple objects. Demonstrations show that the gripper can quickly reconfigure between three different grasping modes and has sufficient stiffness to engage with and lift multiple objects with distinct geometries. [ABSTRACT FROM AUTHOR]

This article presents a unified mathematical approach for modeling, identifying, and solving the friction-inclusive dynamics of robotic mechanisms driven by sliding contact transmission systems. This approach is applied to the most common industrial screw-based drives: 1) the worm drive, 2) the simple lead screw drive, and 3) the antibacklash lead screw drive. The resulting dynamics, handily transferable to single and multiple degree of freedom (DoF) manipulators, are complemented with an algorithm for the solution of the forward dynamics problem as well as a framework for friction identification based on nonlinear optimization. The presented theory is experimentally tested on single-DoF screw-based drives for a variety of payloads and at different operation speeds. Simulation and parameter identification results using the classical Coulomb model, the Coulomb model with Stribeck friction, and the Armstrong model with Stribeck friction, rising static friction, and frictional memory are compared with experimental data, showcasing the effectiveness of the presented approach toward framing the concepts of friction and motion transmission into a robotics setting. [ABSTRACT FROM AUTHOR]

In this article, we present a new procedure for the derivation of the linearized kinematics and dynamics of a flexible industrial robotic manipulator. We introduce the Lie groups of dual rotation and dual homogeneous transformation matrices, which are the basis for the derivation of dual twists. In addition, dual screws and dual screw transformation matrices are introduced, which are used for the development of a general and systematic linearization procedure for both kinematics and dynamics. This leads to expressions that are linearized in all the states associated with the elastic motion. The dynamic modeling procedure is based on Kane's method, where the partial velocities and partial angular velocities are given as dual screws arranged as columns of dual projection matrices. The elasticity of the links is modeled by the assumed mode method. The presented procedure is implemented numerically for a 4-degrees of freedom manipulator and the simulation results are given. [ABSTRACT FROM AUTHOR]

In current robot calibration approaches, the error propagation and identification of serial and parallel robots fail to be solved intuitively and generically, resulting in an inefficient calibration implementation and a low accuracy improvement. In this article, we present a generic error modeling method of serial robots and extend to parallel robots by finite and instantaneous screw (FIS) theory. The differential map and the explicit description of FIS on the robot motions enable a concise error modeling of the serial robot. The identifiability of errors in serial robot is discussed. The maximum independent errors are proved to be 4r + 2p + 6, where r and p are the numbers of revolute and prismatic joints, respectively. Based on the error mapping of serial limbs, reciprocal twist and wrench are introduced to consider the interaction among limbs and reveal the error propagation of the parallel robot. Then, the identification algorithms with high robustness and efficiency are investigated for the serial and parallel robots. Specifically, the conventional ill-conditioning problems of parallel robots are addressed. Finally, the proposed kinematic calibration framework for both types of robots are compared with the existing methods, and verified by simulations and experiments. The results show that our calibration approach improves the robot accuracy in a robust and efficient manner. [ABSTRACT FROM AUTHOR]

Underactuated systems offer compact design with easy actuation and control but at the cost of limited stable configurations and reduced dexterity compared to the directly driven and fully actuated systems. Here, we propose a compact origami-based design in which we can modulate the material stiffness of the joints and thereby control the stable configurations and the overall stiffness in an underactuated robot. The robotic origami, robogami, design uses multiple functional layers in nominally two-dimensional robots to achieve the desired functionality. To control the stiffness of the structure, we adjust the elastic modulus of a shape memory polymer using an embedded customized stretchable heater. We study the actuation of a robogami finger with three joints and determine its stable configurations and contact forces at different stiffness settings. We monitor the configuration of the finger using feedback from customized curvature sensors embedded in each joint. A scaled down version of the design is used in a two-fingered gripper and different grasp modes are achieved by activating different sets of joints. [ABSTRACT FROM PUBLISHER]

A small but interesting result of Brockett is extended to the Euclidean group $SE(3)$ and is illustrated by several examples. The result concerns the explicit solution of an optimal control problem on Lie groups, where the control belongs to a Lie triple system in the Lie algebra. The extension allows for an objective function based on an indefinite quadratic form. Applying the result requires explicit knowledge of the Lie triple systems of the Lie algebra $se(3)$. Hence, a complete classification of the Lie triple systems of this Lie algebra is derived. Examples are considered for optimal trajectories in three cases. The first case concerns cars moving in the plane. The second looks at motions that rigidly follow the Bishop frame to a space curve. The final example does not have a particular name as it does not seem to have been studied before. The appendix gives a brief introduction to Screw theory. This is essentially the study of the Lie algebra $se(3)$. [ABSTRACT FROM PUBLISHER]

Accurately targeting multi-adjacent points (MAPs) during image-guided percutaneous procedures is challenging due to needle deflection and misalignment. The associated errors can result in inadequate treatment of cancer in the case of prostate brachytherapy, or inaccurate diagnosis during biopsy, while repeated insertions increase procedure time, radiation dose, and complications. To address these challenges, we present an image-guided robotic system capable of MAP targeting of irregularly shaped volumes after a single insertion of a percutaneous instrument. The design of the compact CT-compatible drive mechanism is based on a nested screw and screw-spline combination that actuates a straight outer cannula and a curved inner stylet that can be repeatedly straightened when retracted inside the cannula. The stylet translation and cannula rotation/translation enable a 3-D workspace to be reached with the stylet's tip. A closed-form inverse kinematics and image-to-robot registration are implemented in an image-guided system including a point-and-click user interface. The complete system is successfully evaluated with a phantom under a Siemens Definition Flash CT scanner. We demonstrate that the system is capable of MAP targeting for a 2-D shape of the letter “H” and a 3-D helical pattern with an average targeting error of 2.41 mm. These results highlight the benefit and efficacy of the proposed robotic system in seed placement during image-guided brachytherapy. [ABSTRACT FROM PUBLISHER]

Size reduction is a constant objective in new technologies for which very accurate devices are needed when manipulating submillimetric objects. A new kind of microfabricated microrobot based on the use of bistable modules is designed to perform open-loop controlled micropositioning tasks. The DiMiBot (a specific digital microrobot) opens a new paradigm in the design of microrobots by using mechanical stability instead of complex control strategies. We propose a new architecture of digital microrobot for which forward and inverse kinematics models are easy to use. These kinematic models are validated with finite-element-analysis simulations before the fabrication of a real DiMiBot prototype. Tests and characterization of the prototype are made and compared with the desired behavior. Thanks to its submicrometric resolution and to its small dimensions (\sim\!\400\-\mu \m thickness), it is able to manipulate microobjects in confined environments, where no other robot can be used. [ABSTRACT FROM AUTHOR]