waashk/dblp huggingface dataset:
achieving efficient and stable comanipulation through adaptation to changes in human arm impedance. we focus on comanipulation, i.e. manipulation of an object simultaneously held by a robot and a human operator. in this domain, a major difficulty is raised by significant variations of human dynamics, which depend not only on the arm posture, but also on the muscular activity (muscular co-contraction) and more generally on the type of task being performed: fine positioning, gross and rapid movements, repeated movements, etc. an ideal comanipulation system should be able of adapting its behavior to the operator's functional intention, resulting in an intuitive assisting device. toward this goal, we present in this paper first results of our research aimed at developing an instrumented handle mounted on a robot end-effector and held by an operator, that can be used for estimating the grasping force and for adapting the robot controller accordingly. we show first experimental evidences that changes in the grasping force drastically affect the robot controller performances. we thus propose a handle design and a gain scheduling strategy that result in a robot behavior adequate for any kind of grasps. this solution is successfully experimented with a 1 degree of freedom robot under largely variable comanipulation conditions, exhibiting a stable and efficiently adaptive behavior.
the "dlr crash report": towards a standard crash-testing protocol for robot safety - part ii: discussions. after giving a rich data basis of our impact tests with standardized crash-test dummies in part i of this work we address in part ii various aspects related to these tests in a case based discussion. the presented facts, the knowledge gained from our previous work, and the data from part i lead us to recommendations for standardized crash-testing procedures in robotics. the proposed impact procedures will help to compare blunt robot-human impacts on a common basis. we will discuss additional requirements which will enhance the completeness of testing procedures.
3d voxel based online human pose estimation via robust and efficient hashing. in this paper, we present a novel framework to recover human body pose on multi camera systems. our framework leverages 3d voxel data, which are reconstructed from multi-camera systems. the use of voxel data leads to viewpoint-free estimation, which benefits in that reconstruction of a training model is needless in different multicamera arrangements. other notable aspects of our approach are real-time ensuring speed (up to 30 fps), flexibility towards various complex motions and environments. we treat the pose estimation problem as estimating human pose label from the voxel features and tackle this by example based approach. to ensure the real-time speed and to improve precision of pose estimation, a newly fast and robust near-neighbor search metric is installed prior to the evaluation process, what we call csi-psh. we demonstrate the effectiveness of our approach with experiments on both synthetic and real image sequences.
on the switching control of multiple mobile robots formation. this paper considers the formation control of multiple skid-steered mobile robots with nonholonomic constraint in each robot dynamics. we propose a switching control method based on local sensor-based information for the group of robots. if the distance between leader and follower robots is larger than the switching thershold, a nonlinear control law is employed to make the followers move effectively toward the leader robot; otherwise, finite-time control based on feedback linearization is used to quickly stabilize the relative distance and orientation of the follower robots. both stability analysis and simulations are provided and moreover, the formation control of pioneer 3-at mobile robots by the proposed method is shown.
image-based path following control of mobile robots with central catadioptric cameras. the research of image-based control for nonholonomic mobile robots is a recent topic of mobile robots. there are few researches about image-based control of mobile robots with central catadioptric cameras. a central catadioptric camera is very effective to keep target objects in the camera field of view because of its wide area view. in this paper, a new image-based path following control method for a nonholonomic mobile robot with a central catadioptric camera is proposed in the image parameter space. it is confirmed by several simulation, indoor and outdoor experiments that the designed system has high performance and robustness in real world.
vision-aided inertial navigation on an uncertain map using a particle filter. this paper presents a vision-based navigation solution for unmanned aircraft operations on airfield surfaces in gps-denied environments. the unmanned aircraft system ground operations management system (ugoms) described here combines measurements from a computer vision system and inertial sensors with an airport layout database to provide real-time position determination on the airfield surface. ugoms provides both absolute position of the aircraft as well as relative position to airport surface elements such as runway hold lines and taxiway edges. the key technical components of ugoms are computer vision algorithms that classify image regions, markov localization using particle filters, and a navigation architecture which incorporates the localization information. an overview of the overall ugoms architecture is presented as well as preliminary test results using an uncertain airfield map to highlight the performance capabilities of the system.
estimation of the camera pose from image point correspondences through the essential matrix and convex optimization. estimating the camera pose in stereo vision systems is an important issue in computer vision and robotics. one popular way to handle this problem consists of determining the essential matrix which minimizes the algebraic error obtained from image point correspondences. unfortunately, this search amounts to solving a nonconvex optimization, and the existing methods either rely on some approximations in order to get rid of the non-convexity or provide a solution that may be affected by the presence of local minima. this paper proposes a new approach to address this search without presenting such problems. in particular, we show that the sought essential matrix can be obtained by solving a convex optimization built through a suitable reformulation of the considered minimization via appropriate techniques for representing polynomials. numerical results show the proposed approach compares favorably with some standard methods in both cases of synthetic data and real data.
reliable control during current loop failure using etf for position servo system including disturbance observer. a reliable control method is proposed for multiple loop control systems. if a feedback loop fails (e.g., as a result of a sensor breakdown), the control system develops an unstable fluctuation. to cope with this problem, the proposed method uses an equivalent transfer function (etf) for active redundancy compensation after loop failure. the etf is used to maintain the transfer function of the entire system the same before and after loop failure. in this study, the characteristics of a reliable control system that uses an etf were examined experimentally. a position servo system including a disturbance observer is used in the experiment. in case of feedback loop failure, the control system could not be stabilized using the disturbance observer alone; however, the etf stabilized the control system after feedback loop failure.
control of mobile manipulator using the dynamical systems approach. the combination of a mobile platform and a manipulator, known as a mobile manipulator, provides a highly flexible system, which can be used in a wide range of applications, especially within the field of service robotics. one of the challenges with mobile manipulators is the construction of control systems, enabling the robot to operate safely in potentially dynamic environments. in this paper we will present work in which a mobile manipulator is controlled using the dynamical systems approach. the method presented is a two level approach in which competitive dynamics are used both for the overall coordination of the mobile platform and the manipulator as well as the lower level fusion of obstacle avoidance and target acquisition behaviors.
coordination of multiple non-holonomic agents with input constraints. in this paper we present a multi-agent coordination algorithm suitable for systems with aircraft-like kinematic constraints. a model of a system of input-constrained nonholonomic agents is constructed, suitable for use with formal verification tools. the agents considered are uniform and have bounded velocities and limited turning capabilities. we demonstrate how a model checker can be used to generate a counterexample trace for such a system, usable as a trajectory that satisfies our safety and liveness requirements.
prediction and imitation of other's motions by reusing own forward-inverse model in robots. this paper proposes a model that enables a robot to predict and imitate the motions of another by reusing its body forward-inverse model. our model includes three approaches: (i) projection of a self-forward model for predicting phenomena in the external environment (other individuals), (ii) "triadic relation" that is mediation by a physical object between self and others, (iii) introduction of infant imitation by a parent. the recurrent neural network with parametric bias (rnnpb) model is used as the robot's self forward-inverse model. a group of hierarchical neural networks are attached to the rnnpb model as "conversion modules". experiments demonstrated that a robot with our model could imitate a human's motions by translating the viewpoint. it could also discriminate known/unknown motions appropriately, and associate whole motion dynamics from only one motion snap image.
learning to detect loop closure from range data. despite significant developments in the simultaneous localisation and mapping (slam) problem, loop closure detection is still challenging in large scale unstructured environments. current solutions rely on heuristics that lack generalisation properties, in particular when range sensors are the only source of information about the robot's surrounding environment. this paper presents a machine learning approach for the loop closure detection problem using range sensors. a binary classifier based on boosting is used to detect loop closures. the algorithm performs robustly, even under potential occlusions and significant changes in rotation and translation. we developed a number of features, extracted from range data, that are invariant to rotation. additionally, we present a general framework for scan-matching slam in outdoor environments. experimental results in large scale urban environments show the robustness of the approach, with a detection rate of 85% and a false alarm rate of only 1%. the proposed algorithm can be computed in real-time and achieves competitive performance with no manual specification of thresholds given the features.
cardiolock2: parallel singularities for the design of an active heart stabilizer. in this paper, the design of a new active cardiac stabilizer, cardiolock2, is presented. following the proof of concept cardiolock [7], this device allows an active stabilization of the surface of a beating heart in two directions, which is considered sufficient for a complete stabilization. piezoelectric actuation is combined with a compliant architecture to obtain high dynamics and accuracy. a remote center of motion is obtained with a serial architecture, and parallel mechanisms in configurations close to singularity are used to increase the workspace. a kinematic analysis is first presented, before detailing the main properties of the device and the current development of the prototype.
stable dynamic walking of a quadruped via phase modulations against small disturbances. it is generally accepted that locomotion in animals is based on a trade-off between energy consumption and stability. however, this trade-off is the result of the interaction between complex mechanical and control systems. to gain insight into that issue, a step-by-step approach is needed. in this study, as a first step to investigate three dimensional quadrupedal walking, we aim at establishing a control system as "minimal" as possible, able to realize stable dynamic walk. using a simple mechanical structure, we realized dynamic walk with a distributed control system, made of four independent leg controllers whose swing and stance phases durations are modulated based on leg loading information. phase modulations contribute to stabilize the posture in the frontal plane via automatic duty ratios adjustments that tend to compensate perturbations of the body rolling motion. by applying lateral perturbations, we found that the control system withstands well perturbations increasing the rolling motion amplitude, but is sensible to perturbations that suddenly decrease it, as the foreleg on the more loaded side is prevented to swing. hence, we implemented an ascending coordination mechanism where the transition to swing in a hind leg promotes the same event in the foreleg. the duration of the subsequent foreleg swing phase is reduced to prevent excessive increase of the rolling motion amplitude. the resultant control system, although extremely simple, was able to realize dynamic walk resistant to small disturbances (lateral perturbations and terrain irregularities).
battery state estimation using unscented kalman filter. online evaluation of battery state of function (sof) is crucial for battery management systems of autonomous mobile robots. battery state of charge (soc) represents its remaining energy available, whereas internal resistance and capacity reflect its state of health (soh). in this paper, an improved equivalent circuit model is proposed to estimate soc, internal resistance and capacity using an unscented kalman filter (ukf). the proposed method not only estimates soc, but also evaluates soh and sof. experimental results have shown the effectiveness of the proposed method using resistive loads and a robot prototype for inspecting power transmission line.
effects of compliant ankles on bipedal locomotion. the influence of ankle compliance on bipedal robot locomotion is investigated in this paper. the focus is on reduction of energy consumption. the concept of hybrid zero dynamics is adapted to design walking gaits with three phases: underactuated heel roll, full actuation and underactuated toe roll. ankle springs work in parallel with the ankle actuators. stiffness and offset of the linear torsional springs at the ankle and gait parameters are optimized simultaneously. it is shown that simultaneous optimization of spring properties and gait is superior to optimizing the spring after the gait. optimal spring stiffness and offset lead to a major reduction in energy consumption. furthermore, a more human-like gait is observed for simultaneous optimization of gait and spring parameters compared to gait optimization with zero stiffness.
visual servoing and characterization of resonant magnetic actuators for decoupled locomotion of multiple untethered mobile microrobots. wireless resonant magnetic micro-actuators have been previously described as highly effective propulsion mechanisms for untethered mobile microrobots. the discussion thus far has been primarily relegated to a characterization of stationary devices and the de facto observation of their mobility. before applications of microrobots can be more fully explored, devices are required that can operate reliably and repeatably in a host of operating environments. in this paper, we analyze the in situ performance of resonant magnetic actuators for microrobotic locomotion to better understand their durability, substrate requirements, and driving characteristics.
natural self motion of a robotic limb with single degree-of-redundancy. the self motion of a kinematically redundant robotic limb with single degree of redundancy is analyzed, focusing thereby on the nonlinear self-motion component. the role of this component has been completely ignored in past studies on self motion. it is shown that jacobian pseudoinverse-based resolution -- the usual resolution method for nonlinear self-motion -- yields poor dynamic performance. a special type of self motion is identified based on the natural metric on the self-motion manifold and the energy conservation principle. this type of self motion is shown to have superior dynamics in terms of torque requirement and to avoid abrupt fluctuations in acceleration in the vicinity of singular points.
modular weight-balanced mechanical tracker for portable haptics. this paper describes the design, the development and the tests of an innovative 6 degrees of freedom (dofs) mechanical tracker. the new device has a modular structure that exploits three mechanical units each composed of two rotational joints and allows to scale the usable workspace by substituting the connecting links. the sensing principle for the joint angles measurement is based on an innovative hall-effect angle sensor with high resolution, developed and conceived for low cost applications. the system that has been realized and tested is conceived for the tracking of portable haptic devices. furthermore, the system includes a weight balancing system that allows to exploit the mechanical structure of the tracker for balancing a given weight located at the end-effector of the device.
orbital stabilization of a pre-planned periodic motion to swing up the furuta pendulum: theory and experiments. the problem of swinging up inverted pendulums has often been solved by stabilization of a particular class of homoclinic structures present in the dynamics of the standard pendulum. in this article new arguments are suggested to show how different homoclinic curves can be preplanned for dynamics of the passive-link of the robot. this is done by reparameterizing the motion according to geometrical relations among the generalized coordinates. it is also shown that under certain conditions there exist periodic solutions surrounding such homoclinic orbits. these trajectories admit designing feedback controllers to ensure exponential orbital stabilization. the method is illustrated by simulations and supported by experimental studies.
an efficient parallel approach to random sample matching (pransam). this paper introduces a parallelized variant of the random sample matching (ransam) approach, which is a very time and memory efficient enhancement of the common random sample consensus (ransac). ransam exploits the theory of the birthday attack whose mathematical background is known from cryptography. the ransam technique can be applied to various fields of application such as mobile robotics, computer vision, and medical robotics. since standard computers feature multi-core processors nowadays, a considerable speedup can be obtained by distributing selected subtasks of ransam among the available cores. first of all this paper addresses the parallelization of the ransam approach. several important characteristics are derived from a probabilistic point of view. moreover, we apply a fuzzy criterion to compute the matching quality, which is an important step towards real-time capability. the algorithm has been implemented for windows and for the qnx rtos. in an experimental section the performance of both implementations is compared and our theoretical results are validated.
generic decoupled image-based visual servoing for cameras obeying the unified projection model. in this paper a generic decoupled imaged-based control scheme for calibrated cameras obeying the unified projection model is proposed. the proposed decoupled scheme is based on the surface of object projections onto the unit sphere. such features are invariant to rotational motions. this allows the control of translational motion independently from the rotational motion. finally, the proposed results are validated with experiments using a classical perspective camera as well as a fisheye camera mounted on a 6 dofs robot platform.
singularity avoidance for over-actuated, pseudo-omnidirectional, wheeled mobile robots. for mobile platforms with steerable standard wheels it is necessary to precisely coordinate rotation and steering angle of their wheels. an established approach to ensure this is to represent the current state of motion in form of the instantaneous centre of motion (icm) and to derive a trajectory within this space. however, while control in the icm space does guarantee adherence to the system's nonholonomic constraints, it does not avoid the system's singular configurations. within this work we address the problem of singularity avoidance within the icm space. singularities related to the mathematical representation of the icm are reduced by a reformulation of this representation. furthermore, a controller based on artificial potential fields avoiding singular configurations of the robot by representing them as obstacles in the derived icm space is designed. the resulting controller is particularized and analyzed w.r.t. the care-o-bot 3 demonstrator.
oriented bounding surfaces with at most six common normals. we present a new type of oriented bounding surfaces, which is particularly well suited for shortest distance computations. the bounding surfaces are obtained by considering surfaces whose support functions are restrictions of quadratic polynomials to the unit sphere. we show that the common normals of two surfaces of this type - and hence their shortest distance - can be computed by solving a polynomial of degree six. this compares favorably with other existing bounding surfaces, such as quadric surfaces, where the computation of the common normals is known to lead to a polynomial of degree 24.
task-space trajectories via cubic spline optimization. we consider the task of planning smooth trajectories for robot motion. in this paper we make two contributions. first we present a method for cubic spline optimization; this technique lets us simultaneously plan optimal task-space trajectories and fit cubic splines to the trajectories, while obeying many of the same constraints imposed by a typical motion planning algorithm. the method uses convex optimization techniques, and is therefore very fast and suitable for real-time re-planning and control. second, we apply this approach to the tasks of planning foot and body trajectory for a quadruped robot, the "littledog," and show that the proposed approach improves over previous work on this robot.
navigation through urban environments by visual perception and interaction. in the autonomous city explorer (ace) project a mobile robot is developed, which is capable of finding its way to a given destination in an unknown urban environment. an exemplary mission is to find the way from our institute to the marienplatz, a public place in the center of munich, without any prior knowledge or gps information. inspired by the behavior of humans in unknown environments, ace must find its way by asking pedestrians. the route is about 1.5 kilometers far and includes heavily traveled roads and crowded public places. in order to navigate safely in an unknown urban environment, some challenges arise for the vision system. robust human detection, tracking and the estimation of human body poses is essential for natural interaction with pedestrians. furthermore, the robot needs to be able to detect sidewalk and crossroads. a visual odometry system is used to support the conventional navigation. outdoor experiments were conducted twice successfully. after about 5 hours and interacting with 25 and 38 persons respectively, ace arrived the marienplatz. this paper describes both, an architecture of the vision system used for ace and the algorithms used to deal with the described challenges.