waashk/dblp huggingface dataset:
control of nonholonomic mobile robots based on the transverse function approach. the problem of stabilizing reference trajectories-- also referred to as the trajectory tracking problem--for nonholonomic mobile robots is revisited. theoretical difficulties and impossibilities that set inevitable limits to what is achievable with feedback control are surveyed, and properties of kinematic control models are recalled, with a focus on controllable driftless systems that are invariant on a lie group. this geometric framework takes advantage of ubiquitous symmetry properties involved in the motion of mechanical bodies.the transverse function approach, a control design method developed by the authors for the past few years, is reviewed. a salient feature of this approach, which singles it out of the abundant literature devoted to the subject, is the obtention of feedback laws that unconditionally achieve the practical stabilization of arbitrary reference trajectories, including fixed points and nonadmissible trajectories. this property is complemented with novel results showing how the more common property of asymptotic stabilization of a large class of admissible trajectories can also be granted with this type of control. application to unicycle-type and car-like vehicles is presented and illustrated via simulations. complementary issues (transient maneuvers monitoring, extensions of the approach to systems that are not invariant on a lie group, etc.) are also addressed with the concern of practicality.
source seeking for two nonholonomic models of fish locomotion. in this paper, we present a method of locomotion control for underwater vehicles that are propelled by a periodic deformation of the vehicle body, which is similar to the way a fish moves. we have developed control laws employing "extremum seeking" for two different "fish" models. the first model consists of three rigid body links and relies on a 2-degree-of-freedom (dof)movement that propels the fish without relying on vortices. the second fish model uses a joukowski airfoil that has only 1 dof in its movement and, thus, relies on vortex shedding for propulsion. we achieve model-free and position-free "source seeking," and, if position is available, navigation along a predetermined path.
performance evaluation for multi-arm manipulation of hollow suspended organs. this paper presents a unified mathematical framework for modeling and evaluating the performance of multiple robotic arms that operate on hollow suspended organs. this framework is applied 10 a novel two-armed hybrid robotic system being developed for ophthalmic vitreous surgeries. four cases are designated to capture the general movements required for any surgical procedure associated with hollow suspended organs. dexterity measures, based on multiple characteristic lengths, are presented for procedures corresponding to these mauipulation cases. simulation results of the dual-arm robotic system for ophthalmic surgery are presented for all four manipulation cases. a comparison of this robotic system with current surgical tools shows a significant improvement in intraocular dexterity.
impedance compensation of subar for back-drivable force-mode actuation. the sogang university biomedical assistive robot (subar), which is an advanced version of the exoskeleton for patients and the old by songang (expos) is a wearable robot developed to assist physically impaired people. it provides a person with assistive forces controlled by human intentions. if a standard geared dc motor is applied, however, the control efforts will be used mainly to overcome the resistive forces caused by the friction, the damping, and the inertia in actuators. in this paper, such undesired properties are rejected by applying a flexible transmission. with the proposed method, it is intended that an actuator exhibits zero impedance without friction while generating the desired torques precisely. since the actuation system of subar has a large model variation due to human-robot interaction, a control algorithm for the flexible transmission is designed based on a robust control method. in this paper, the mechanical design of subar, including the flexible transmission and its associated control algorithm, are presented. they are also verified by experiments.
compliant terrain adaptation for biped humanoids without measuring ground surface and contact forces. this paper reports the applicability of our passivity-based contact force control framework for biped humanoids. we experimentally demonstrate its adaptation to unknown rough terrain. adaptation to uneven ground is achieved by optimally distributed antigravitational forces applied to preset contact points in a feedforward manner, even without explicitly measuring the external forces or the terrain shape. adaptation to unknown inclination is also possible by combining an active balancing controller based on the center-of-mass (com) measurements with respect to the inertial frame. furthermore, we show that a simple impedance controller for supporting the feet or hands allows the robot to adapt to low-friction ground without prior knowledge of the ground friction. this presentation includes supplementary experimental videos that show a full-sized biped humanoid robot balancing on uneven ground or time-varying inclination.
design strategy of serial manipulators with certified constraint satisfaction. this paper presents the design strategy of serial manipulators with constraint satisfaction. the algorithm provides certified solutions to the range of values of the manipulator design parameters that satisfy the given constraints for all points inside a desired workspace. alternatively, it can also be used to obtain the achievable workspace of a particular manipulator topology within which a set of given constraints are satisfied. this strategy can therefore be applied to the general case of a serial manipulator design problem. robots of adjustable parameters, or even reconfigurable robot strategy to obtain a suitable topology. the intervalbased algorithm was implemented on an example serial anthropomorphic manipulator with joint displacement constraints and obtains the possible variations to the manipulator topology that allow the required workspace to be achievable under the given joint displacement constraints. results are presented and discussed.
a hybrid mav for ingress and egress of urban environments. small bird-sized aerial robots are expendable and can fly over obstacles and through small openings to assist in the acquisition and distribution of intelligence during reconnaissance, surveillance, and search-and-rescue missions in urban environments. however, limited flying space and densely populated obstacle fields require a vehicle that is capable of hovering but is also maneuverable. a secondary flight mode was incorporated into a fixed-wing aircraft to preserve its maneuverability while adding the capability of hovering. an inertial measurement sensor and onboard flight control system were interfaced and used to transition the hybrid prototype from cruise to hover flight and sustain a hover autonomously. furthermore, the hovering flight mode can be used to maneuver the aircraft through small openings such as doorways. an ultrasonic and infrared sensor suite was designed to follow exterior building walls until an ingress route was detected. reactive control was then used to traverse the doorway and gather reconnaissance. this paper describes the holistic approach of platform development, sensor suite design, and control of the hybrid prototype.
modeling and system identification of a life-size brake-actuated manipulator. safety is a critical factor when designing a robotic rehabilitation environment. whole-limb or life-size haptic interaction would allow virtual robotic rehabilitation of daily living activities such as sweeping or shelving. however, it has been too dangerous to implement such an environment with conventional active robots that use motor, hydraulic, or pneumatic actuation. to address this issue, a life-size 6-degree-of-freedom (dof) brakeactuated manipulator (bam) was designed and constructed. this paper details the bam's system models including mechanisms, kinematics, and dynamics, as well as detailed input and friction models. in addition, a new system-identification technique that utilizes human input to excite the robot's dynamics with unscented kalman filtering was employed to identify system parameters. noise sources are discussed, and the model is validated through force estimation with inverse dynamics. model parameters and performance are compared with other commercially available haptic devices. the bam shows a significantly larger workspace, maximum force, and stiffness over other devices exhibiting its promise toward rehabilitative applications.
a modularized personal robot drp i: design and implementation. in this paper, we investigate comprehensive issues of modularized robot systems and present architecture for effective development of personal robots. the proposed architecture includes the interface and interaction methodology of the hardware modules and the software among the modules. based on the architecture, we present a fully modularized personal robot dynamically reconfigurable personal robot i. its hardware modules are easily added to or removed from the original system, and also the distributed software functions of the modules are rearrangeable accordingly. we focus on how to effectively build up the robot, and discuss the dynamically reconfigurable features of it for evaluating the proposed idea and approach.
a geometric algorithm to compute time-optimal trajectories for a bidirectional steered robot. this paper addresses the problem of determining time-optimal trajectories, between two specified configurations, for a nonholonomic bidirectional steered robot. it presents an original geometric reasoning that is grounded on pontryagin's maximum principle, which provides analytical solutions of this problem in a visually clear way and allows for an effective algorithm to compute the exact optimal trajectories between two arbitrarily specified configurations. the proposed geometric reasoning is based on the analysis of the switching functions of the optimal controller and the definition of a switching vector from which it is able to determine a unit vector rotating along a unit circle of an appropriate coordinate system. it is shown that simple geometric rules are sufficient to determine all possible rotations of this unit vector, from which the time-optimal trajectories can be uniquely determined. the proposed algorithm, which is based on this geometric reasoning, is guaranteed to be complete and has a low computational cost. moreover, the proposed geometric representation provides an interesting insight into the structure of this class of nonholonomic systems, thereby offering a model for further studies.
a multisensor decision fusion system for terrain safety assessment. this paper describes an onboard automated hybrid reasoning system for terrain safety assessment using multiple heterogeneous sensors onboard a spacecraft. an innovative feature of this system is integration of multiple sensing modalities and different reasoning engines into a unified approach. three different frameworks for representation of data uncertainty are considered: fuzzy set theory, bayesian probability theory, and dempster-shafer belief theory. the hybrid reasoning system is composed of three subsystems, namely, multisensor fusion, multidecision fusion, and tier-based fusion selection, where each tier represents a range of spacecraft altitudes. simulation results are presented to illustrate the multisensor decision fusion methodology described in this paper. the developed capabilities will enable future spacecraft to land safely in more challenging planetary regions with scientifically qileresting terrain features.
a reconfigurable robot with lockable cylindrical joints. this paper presents a new conceptual design for reconfigurable robots. unlike conventional reconfigurable robots, our design does not achieve reconfigurability by utilizing modular joints. rather, the robot is equipped with passive joints, i.e., joints without actuator or sensor, which permit changing the denavit-hartenberg (dh) parameters such as the link length and twist angle. the passive joints will become controllable when the robot forms a closed kinematic chain. also, each passive joint is equipped with a built-in brake mechanism that is normally locked, but the lock can be released whenever the parameters are to be changed. such a versatile and agile robot is particularly suitable for space application for its simple, compact, and light design. the kinematics and recalibration of this kind of reconfigurable robot are thoroughly analyzed. a stable reconfiguration-control algorithm is devised to take the robot from one configuration to another by directly regulating the passive joints to the associated, desired dh parameters. conditions for the observability and the controllability of the passive joints are also derived in detail.
image guidance of flexible tip-steerable needles. image guidance promises to improve targeting accuracy and broaden the scope of medical procedures performed with needles. this paper takes a step toward automating the guidance of a flexible tip-steerable needle as it is inserted into the human tissue. we build upon a previously proposed nonholonomic model of needles that derive steering from asymmetric bevel forces at the tip. the bevel-tip needle is inserted and rotated at its base in order to steer it in 6 dof. as a first step for control, we show that the needle tip can be automatically guided to a planar slice of the tissue as it is inserted. our approach keeps the physician in the loop to control insertion speed. the distance of the needle tip position from the plane of interest is used to drive an observer-based feedback controller that we prove is locally asymptotically stable. numerical simulations demonstrate a large domain of attraction and robustness of the controller in the face of parametric uncertainty and measurement noise. physical experiments with tip-steerable nitinol needles inserted into a transparent plastisol tissue phantom under stereo image guidance validate the effectiveness of our approach.
a new mechanism for mesoscale legged locomotion in compliant tubular environments. we present design and experimental performance results for a novel mechanism for robotic legged locomotion at the mesoscale (from hundreds of microns to tens of centimeters). the new mechanism is compact and strikes a balance between conflicting design objectives, exhibiting high foot forces and low power consumption. it enables a small robot to traverse a compliant, slippery, tubular environment, even while climbing against gravity. this mechanism is useful for many mesoscale locomotion tasks, including endoscopic capsule robot locomotion in the gastrointestinal tract. it has enabled fabrication of the first legged endoscopic capsule robot whose mechanical components match the dimensions of commercial pill cameras (11 mm diameter by 25 mm long). a novel slot-follower mechanism driven via lead screw enables the mechanical components of the capsule robot to be as small while simultaneously generating 0.63 n average propulsive force at each leg tip. in this paper, we describe kinematic and static analyses of the lead screw and slot-follower mechanisms, optimization of design parameters, and experimental design and tuning of a gait suitable for locomotion. a series of ex vivo experiments demonstrate capsule performance and ability to traverse the intestine in a manner suitable for inspection of the colon in a time period equivalent to standard colonoscopy.
robot-aided neurorehabilitation: a novel robot for ankle rehabilitation. in this paper, we present the design and characterization of a novel ankle robot developed at the massachusetts institute of technology (mit). this robotic module is being tested with stroke patients at baltimore veterans administration medical center. the purpose of the on-going study is to train stroke survivors to overcome common foot drop and balance problems in order to improve their ambulatory performance. its design follows the same guidelines of our upper extremity designs, i.e., it is a low friction, backdriveable device with intrinsically low mechanical impedance. here, we report on the design and mechanical characteristics of the robot. we also present data to demonstrate the potential of this device as an efficient clinical measurement tool to estimate intrinsic ankle properties. given the importance of the ankle during locomotion, an accurate estimate of ankle stiffness would be a valuable asset for locomotor rehabilitation. our initial ankle stiffness estimates compare favorably with previously published work, indicating that our method may serve as an accurate clinical measurement tool.
cooperative robot control and concurrent synchronization of lagrangian systems. concurrent synchronization is a regime where diverse groups of fully synchronized dynamic systems stably coexist. we study global exponential synchronization and concurrent synchronization in the context of lagrangian systems control. in a network constructed by adding diffusive couplings to robot manipulators or mobile robots, a decentralized tracking control law globally exponentially synchronizes an arbitrary number of robots, and represents a generalization of the average consensus problem. exact nonlinear stability guarantees and synchronization conditions are derived by contraction analysis. the proposed decentralized strategy is further extended to adaptive synchronization and partialstate coupling.
biologically inspired mobile robot vision localization. we present a robot localization system using biologically inspired vision. our system models two extensively studied human visual capabilities: 1) extracting the "gist" of a scene to produce a coarse localization hypothesis and 2) refining it by locating salient landmark points in the scene. gist is computed here as a holistic statistical signature of the image, thereby yielding abstract scene classification and layout. saliency is computed as a measure of interest at every image location, which efficiently directs the time-consuming landmark-identification process toward the most likely candidate locations in the image. the gist features and salient regions are then further processed using amonte carlo localization algorithm to allow the robot to generate its position. we test the system in three different outdoor environments--building complex (38.4m × 54.86 m area, 13 966 testing images), vegetation-filled park (82.3m × 109.73m area, 26 397 testing images), and openfield park (137.16m × 178.31m area, 34 711 testing images)--each with its own challenges. the system is able to localize, on average, within 0.98, 2.63, and 3.46 m, respectively, even with multiple kidnapped-robot instances.
robust impedance control of a flexible structure mounted manipulator performing contact tasks. this paper presents a robustness analysis and design approach for impedance control of a flexible structure mounted manipulator (fsmm) performing contact tasks. in the analysis, the dynamics of the flexible structure are treated as uncertain. the environment is also treated as uncertain, but with force-displacement characteristics satisfying a sectorbound condition. first, a one dimensional model for an end-effector under impedance control is considered. the effect of base flexibility on stability under contact conditions is then assessed via the popov criterion. based on these results, an approach to robust impedance control is proposed. it is shown that by augmenting low-order filters within a standard impedance control law, robust global stability in the presence of base flexibility can be achieved. the controller is shown to perform successfully in experiments on a two-link lab-scale fsmm.
dynamic performance of a scara robot manipulator with uncertainty using polynomial chaos theory. this short paper outlines how polynomial chaos theory (pct) can be utilized for manipulator dynamic analysis and controller design in a 4-dof selective compliance assembly robot-arm-type manipulator with variation in both the link masses and payload. it includes a simple linear control algorithm into the formulation to show the capability of the pct framework.
swedish wheeled omnidirectional mobile robots: kinematics analysis and control. swedish wheeled robots have received growing attention over the last few years. their kinematic models have interesting properties in terms of mobility and possible singularities. this paper addresses the issue of kinematic modeling, singularity analysis, and motion control for a generic vehicle equipped with n swedish wheels.
a unified approach to integrate unilateral constraints in the stack of tasks. the control approaches based on the task function formalism, and particularly those structured as a prioritized hierarchy of tasks, enable complex behaviors with elegant properties of robustness and portability to be built. however, it is difficult to consider a straight forward integration of tasks described by unilateral constraints in such frameworks. indeed, unilateral constraints exhibit irregularities that prevent the insertion of unilateral tasks at any priority level, other than the lowest, of a hierarchy. in this paper, we present an original method to generalize the hierarchy-based control schemes to account for unilateral constraints at any priority level.we develop our method first for task sequencing using only the kinematics description; then, we expand it to the task description, using the operational space formulation. the method applies in robotics and computer graphics animation. its practical implementation is exemplified by realizing a real-manipulator visual servoing task and a humanoid avatar reaching task; both experiments are achieved under the unilateral constraints of joint limits.
design and implementation of nims3d, a 3-d cabled robot for actuated sensing applications. we present nims3d, a novel 3-d cabled robot for actuated sensing applications. we provide a brief overview of the main hardware components. next, we describe installation procedures, including novel calibration methods, that enable rapid in-field deployability for nonexpert end users, and provide simulations and experimental results to highlight their effectiveness. kinematic and dynamic analysis of the system are provided, followed by a description of control methods.we provide experimental results that illustrate tracking of linear and nonlinear paths by nims3d. thereafter, we briefly present an example of an actuated sensing task performed by the system. finally, we describe methods of improving energy efficiency by leveraging nonlinear trajectories and energy-optimal tension distributions. experimental and simulated results show that energy efficiency can be improved significantly by using optimized parabolic trajectories. furthermore, we provide simulation results that demonstrate improved efficiency enabled by optimal, least norm tension distributions.