Showing papers on "Kinematics published in 2017"
TL;DR: Five techniques for motion reconstruction were selected and compared to reconstruct a human arm motion and results show that all but one of the selected models perform similarly (about 35 mm average position estimation error).
Abstract: Motion tracking based on commercial inertial measurements units (IMUs) has been widely studied in the latter years as it is a cost-effective enabling technology for those applications in which motion tracking based on optical technologies is unsuitable. This measurement method has a high impact in human performance assessment and human-robot interaction. IMU motion tracking systems are indeed self-contained and wearable, allowing for long-lasting tracking of the user motion in situated environments. After a survey on IMU-based human tracking, five techniques for motion reconstruction were selected and compared to reconstruct a human arm motion. IMU based estimation was matched against motion tracking based on the Vicon marker-based motion tracking system considered as ground truth. Results show that all but one of the selected models perform similarly (about 35 mm average position estimation error).
273 citations
TL;DR: A neural networks (NNs) enhanced telerobot control system is designed and tested on a Baxter robot and guaranteed performance is achieved at both kinematic and dynamic levels.
Abstract: In this paper, a neural networks (NNs) enhanced telerobot control system is designed and tested on a Baxter robot. Guaranteed performance of the telerobot control system is achieved at both kinematic and dynamic levels. At kinematic level, automatic collision avoidance is achieved by the control design at the kinematic level exploiting the joint space redundancy, thus the human operator would be able to only concentrate on motion of robot’s end-effector without concern on possible collision. A posture restoration scheme is also integrated based on a simulated parallel system to enable the manipulator restore back to the natural posture in the absence of obstacles. At dynamic level, adaptive control using radial basis function NNs is developed to compensate for the effect caused by the internal and external uncertainties, e.g., unknown payload. Both the steady state and the transient performance are guaranteed to satisfy a prescribed performance requirement. Comparative experiments have been performed to test the effectiveness and to demonstrate the guaranteed performance of the proposed methods.
269 citations
Book•
01 Jan 2017
TL;DR: In this article, the authors present a simulation of the physics of rigid bodies in three dimensions and three dimensions in the plane motion of Rigid Bodies: forces and acceleration, energy and momentum, and moments of inertia.
Abstract: 1 Introduction 2 Statics of Particles 3 Rigid Bodies: Equivalent Systems of Forces 4 Equilibrium of Rigid Bodies 5 Distributed Forces: Centroids and Centers of Gravity 6 Analysis of Structures 7 Forces in Beams and Cables 8 Friction 9 Distributed Forces: Moments of Inertia 10 Method of Virtual Work 11 Kinematics of Particles 12 Kinetics of Particles: Newton's Second Law 13 Kinetics of Particles: Energy and Momentum Methods 14 Systems of Particles 15 Kinematics of Rigid Bodies 16 Plane Motion of Rigid Bodies: Forces and Accelerations 17 Plane Motion of Rigid Bodies: Energy and Momentum Methods 18 Kinetics of Rigid Bodies in Three Dimensions 19 Mechanical Vibrations Appendix Fundamentals of Engineering Examination
259 citations
TL;DR: A neurodynamics-based output feedback scheme is proposed for distributed containment maneuvering of marine vessels guided by multiple parameterized paths without using velocity measurements to recover unmeasured velocity information as well as to identify unknown vessel dynamics.
Abstract: In this paper, a neurodynamics-based output feedback scheme is proposed for distributed containment maneuvering of marine vessels guided by multiple parameterized paths without using velocity measurements. Each vessel is subject to internal model uncertainties and external disturbances induced by wind, waves, and ocean currents. In order to recover unmeasured velocity information as well as to identify unknown vessel dynamics, an echo state network (ESN) based observer using recorded input–output data is proposed for each vessel. Based on the observed velocity information of neighboring vessels, distributed containment maneuvering laws are developed at the kinematic level. Next, in order to shape the transient motion profile for vessel kinetics to follow, finite-time nonlinear tracking differentiators are employed to generate smooth reference signals as well as to extract the time derivatives of kinematic control laws. Finally, ESN-based dynamic control laws are constructed at the kinetic level. The stability of the closed-loop system is analyzed via input-to-state stability and cascade theory. Simulation results are provided to illustrate the efficacy of the proposed neurodynamics-based output feedback approach.
257 citations
11 Jun 2017
TL;DR: This paper studies the kinematic bicycle model, which is often used for trajectory planning, and compares its results to a 9 degrees of freedom model, and proposes a simple and efficient consistency criterion to validate the use of this model for planning purposes.
Abstract: Most autonomous driving architectures separate planning and control phases in different layers, even though both problems are intrinsically related Due to limitations on the available computational power, their levels of abstraction and modeling differ; in particular, vehicle dynamics are often highly simplified at the planning phase, which may lead to inconsistency between the two layers In this paper, we study the kinematic bicycle model, which is often used for trajectory planning, and compare its results to a 9 degrees of freedom model Modeling errors and limitations of the kinematic bicycle model are highlighted Lastly, this paper proposes a simple and efficient consistency criterion in order to validate the use of this model for planning purposes
245 citations
TL;DR: The results show that the exoskeleton exhibits good kinematic compatibility to the human body with a wide range of motion and performs task-space force and impedance control behaviors reliably.
Abstract: We present an upper-body exoskeleton for rehabilitation, called Harmony, that provides natural coordinated motions on the shoulder with a wide range of motion, and force and impedance controllability. The exoskeleton consists of an anatomical shoulder mechanism with five active degrees of freedom, and one degree of freedom elbow and wrist mechanisms powered by series elastic actuators. The dynamic model of the exoskeleton is formulated using a recursive Newton-Euler algorithm with spatial dynamics representation. A baseline control algorithm is developed to achieve dynamic transparency and scapulohumeral rhythm assistance, and the coupled stability of the robot-human system at the baseline control is investigated. Experiments were conducted to evaluate the kinematic and dynamic characteristics of the exoskeleton. The results show that the exoskeleton exhibits good kinematic compatibility to the human body with a wide range of motion and performs task-space force and impedance control behaviors reliably.
167 citations
TL;DR: In this paper, an adaptive visual servo controller based on piecewise-constant curvature kinematic, without knowing the true values of the manipulator's length and the target positions, is proposed.
Abstract: It is unavoidable for a soft manipulator to interact with environments during some tasks. These interactions may affect the soft manipulator and make the kinematic model different from the one in free space, e.g., the soft manipulator's effective length and the target positions might change. In order to apply the soft manipulator to constrained environments, an adaptive visual servo controller based on piecewise-constant curvature kinematic, without knowing the true values of the manipulator's length and the target positions, is proposed in this paper. Experimental results in the free space, constrained environment, and the gravity-influenced environment, demonstrate the convergence of the image errors under the proposed controller.
161 citations
TL;DR: A variety of methods have been presented over the past 25 years for the estimate of 2D and 3D joint kinematics by using inertial and magnetic sensors using wearable inertial measurement units, and the aim of the present review is to describe these approaches from a purely methodological point of view.
150 citations
TL;DR: In this article, the adaptive control problem for robot manipulators with both the uncertain kinematics and dynamics is investigated, and two adaptive control schemes are proposed to realize the objective of task-space trajectory tracking irrespective of the uncertain KG and dynamics.
Abstract: In this note, we investigate the adaptive control problem for robot manipulators with both the uncertain kinematics and dynamics. We propose two adaptive control schemes to realize the objective of task-space trajectory tracking irrespective of the uncertain kinematics and dynamics. The proposed controllers have the desirable separation property, and we also show that the first adaptive controller with appropriate modifications can yield the improved performance, without the expense of the conservative gain choice. The performance of the proposed controllers is shown by numerical simulations.
150 citations
TL;DR: The proposed control strategy can simultaneously deal with input saturation, full-state constraint, kinematic coupling, parametric uncertainty, and matched and mismatched disturbances.
Abstract: This paper presents a six-degree-of-freedom relative motion control method for autonomous spacecraft rendezvous and proximity operations subject to input saturation, full-state constraint, kinematic coupling, parametric uncertainty, and matched and mismatched disturbances. Relative rotational and relative translational controllers are developed separately based on a unified adaptive backstepping technique. Both element-wise and norm-wise adaptive estimation techniques are used for handling parametric uncertainties, kinematic couplings, and matched and mismatched disturbances, where the bounds of disturbances are unknown. Two auxiliary design systems are employed to deal with input saturation in the relative rotational and relative translational control designs, and the stability of the saturated control solution is verified. Full-state constraint of the relative pose motion is handled by using barrier Lyapunov functions while achieving a satisfactory control performance. All signals in the closed-loop system are guaranteed to be uniformly ultimately bounded, and the relative motion states are all restricted within the known constraints. Compared with the previous control designs of spacecraft rendezvous and proximity operations, the proposed control strategy in this paper can simultaneously deal with input saturation, full-state constraint, kinematic coupling, parametric uncertainty, and matched and mismatched disturbances. Experimental simulation results validate the performance and robustness improvement of the proposed control strategy.
144 citations
TL;DR: This study provides novel and robust evidence that technique explains a substantial proportion of the variance in RE and performance and recommends that runners and coaches are attentive to specific aspects of stride parameters and lower limb angles in part to optimize pelvis movement, and ultimately enhance performance.
Abstract: © 2017 American College of Sports MedicineDespite an intuitive relationship between technique and both running economy (RE) and performance, and the diverse techniques employed by runners to achieve forward locomotion, the objective importance of overall technique and the key components therein remain to be elucidated. PURPOSE: To determine the relationship between individual and combined kinematic measures of technique with both RE and performance. METHODS: Ninety-seven endurance runners (47 female) of diverse competitive standards performed a discontinuous protocol of incremental treadmill running (4 min stages, 1 km.h increments). Measurements included three-dimensional full body kinematics, respiratory gases to determine energy cost, and velocity of lactate turnpoint (vLTP). Five categories of kinematic measures (vertical oscillation, braking, posture, stride parameters and lower limb angles) and locomotory energy cost (LEc) were averaged across 10-12 km.h (the highest common velocity
TL;DR: In this article, a robot posture optimization methodology based on robotic performance indexes is presented, where a deformation evaluation index is proposed to directly illustrate the deformation of the six-revolute (6R) industrial robot (IR) end-effector (EE) when a force is applied on it.
Abstract: For industrial robots, the relatively low posture-dependent stiffness deteriorates the absolute accuracy in the robotic machining process. Thus, it is reasonable to consider performing machining in the regions of the robot workspace where the kinematic, static and even dynamic performances are highest, thereby reducing machining errors and exhausting the advantages of the robot. Simultaneously, an optimum initial placement of the workpiece with respect to the robot can be obtained by optimizing the above performances of the robot. In this paper, a robot posture optimization methodology based on robotic performance indexes is presented. First, a deformation evaluation index is proposed to directly illustrate the deformation of the six-revolute (6R) industrial robot (IR) end-effector (EE) when a force is applied on it. Then, the kinematic performance map drawn according to the kinematic performance index is utilized to refine the regions of the robot workspace. Furthermore, main body stiffness index is proposed here to simplify the performance index of the robot stiffness, and its map is used to determine the position of the EE. Finally, the deformation map obtained according to the proposed deformation evaluation index is used to determine the orientation of the EE. Following these steps, the posture of the 6R robot with the best performance can be obtained, and the initial workpiece placement can be consequently determined. Experiments on a Comau Smart5 NJ 220-2.7 robot are conducted. The results demonstrate the feasibility and effectiveness of the present posture optimization methodology.
TL;DR: Results showed that the Kinect v2 sensor has the potential to be an effective clinical assessment tool for sagittal plane knee and hip joint kinematics, as well as some spatiotemporal temporal variables including pelvis displacement and step characteristics during the gait cycle.
TL;DR: This study reports acceptable accuracy of a commercially available IMU system; however, results should be interpreted as protocol specific because of the significant inversely proportional error across all joints.
Abstract: The purpose of this study was to validate a commercially available inertial measurement unit (IMU) system against a standard lab-based motion capture system for the measurement of shoulder elevation, elbow flexion, trunk flexion/extension, and neck flexion/extension kinematics. The validation analyses were applied to 6 surgical faculty members performing a standard, simulated surgical training task that mimics minimally invasive surgery. Three-dimensional joint kinematics were simultaneously recorded by an optical motion capture system and an IMU system with 6 sensors placed on the head, chest, and bilateral upper and lower arms. The sensor-to-segment axes alignment was accomplished manually. The IMU neck and trunk IMU flexion/extension angles were accurate to within 2.9 ± 0.9 degrees and 1.6 ± 1.1°, respectively. The IMU shoulder elevation measure was accurate to within 6.8 ± 2.7° and the elbow flexion measure was accurate to within 8.2 ± 2.8°. In the Bland-Altman analyses, there were no significant syst...
19 Oct 2017
TL;DR: This work makes the first attempt to generate articulated human motion sequence from a single image by utilizing paired inputs including human skeleton information as motion embedding and a single human image as appearance reference to generate novel motion frames based on the conditional GAN infrastructure.
Abstract: This work makes the first attempt to generate articulated human motion sequence from a single image. On one hand, we utilize paired inputs including human skeleton information as motion embedding and a single human image as appearance reference, to generate novel motion frames based on the conditional GAN infrastructure. On the other hand, a triplet loss is employed to pursue appearance smoothness between consecutive frames. As the proposed framework is capable of jointly exploiting the image appearance space and articulated/kinematic motion space, it generates realistic articulated motion sequence, in contrast to most previous video generation methods which yield blurred motion effects. We test our model on two human action datasets including KTH and Human3.6M, and the proposed framework generates very promising results on both datasets.
TL;DR: Results indicate that in healthy subjects sagittal plane joint kinematics measured with the RehaGait® are comparable to those using a Vicon® system/model and that the measuredKinematics have a good repeatability, especially for walking.
TL;DR: In this paper, a combination of pseudo-dynamic approach and discretisation technique is used to estimate slope stability under the ultimate limit state with the aim of generating a potential failure mechanism with discretised points by forward difference point-to-point method.
Abstract: Slopes are more vulnerable to instability when subjected to earthquake ground shaking. In order to account for the dynamic forces induced by ground shaking, a novel procedure is introduced in this paper to estimate slope stability under the ultimate limit state with a combination of pseudo-dynamic approach and discretisation technique. A pseudo-dynamic approach is adopted which allows the introduction of an arbitrary time history of seismic accelerations. In order to consider non-uniformity of soil properties of the slope, the discretisation technique is proposed with the aim of generating a potential failure mechanism with discretised points by forward difference ‘point-to-point’ method. Infinitesimal trapezoidal elements composed of successive discretised points and sloping surface are selected for kinematic analysis. In this way, the problem is decomposed into separate components, which aids computational effort. The upper-bound solutions of limiting surcharge loading and yield seismic acceleration are...
TL;DR: In this paper, a general and comprehensive methodology to eliminate the constraints violation at the position and velocity levels is offered, which is embedded in the standard method to solve the equations of motion based on the technique of Lagrange multipliers.
Abstract: It is known that the dynamic equations of motion for constrained mechanical multibody systems are frequently formulated using the Newton–Euler’s approach, which is augmented with the acceleration constraint equations. This formulation results in the establishment of a mixed set of partial differential and algebraic equations, which are solved in order to predict the dynamic behavior of general multibody systems. The classical solution of the equations of motion is highly prone to constraints violation because the position and velocity constraint equations are not fulfilled. In this work, a general and comprehensive methodology to eliminate the constraints violation at the position and velocity levels is offered. The basic idea of the described approach is to add corrective terms to the position and velocity vectors with the intent to satisfy the corresponding kinematic constraint equations. These corrective terms are evaluated as a function of the Moore–Penrose generalized inverse of the Jacobian matrix and of the kinematic constraint equations. The described methodology is embedded in the standard method to solve the equations of motion based on the technique of Lagrange multipliers. Finally, the effectiveness of the described methodology is demonstrated through the dynamic modeling and simulation of different planar and spatial multibody systems. The outcomes in terms of constraints violation at the position and velocity levels, conservation of the total energy and computational efficiency are analyzed and compared with those obtained with the standard Lagrange multipliers method, the Baumgarte stabilization method, the augmented Lagrangian formulation, the index-1 augmented Lagrangian, and the coordinate partitioning method.
TL;DR: A model-free approach for closed loop kinematic control of continuum manipulators in the task space, requiring minimal sensor elements and involving few open parameters for tuning, which is very well suited for nonlinear stochastic continuum robots.
Abstract: This article introduces a machine-learning-based approach for closed loop kinematic control of continuum manipulators in the task space For this purpose, we propose a unique formulation for learning the inverse kinematics of a continuum manipulator while integrating end-effector feedback We demonstrate that this model-free approach for kinematic control is very well suited for nonlinear stochastic continuum robots The article addresses problems that are vital for practical realization of machine-learning techniques The primary objective is to solve the redundancy problem while making the algorithm scalable, fast, and tolerant to stochasticity, requiring minimal sensor elements and involving few open parameters for tuning In addition, we demonstrate that the proposed controller can exhibit adaptive behavior in the presence of external forces and in an unstructured environment with the help of the morphological properties of the manipulator Experimental validation of the proposed controller i
TL;DR: In this paper, a real-time interpolation algorithm is proposed to generate continuous rapid feed motion along short segmented linear tool-paths by smoothing local and adjacent corners that are within close vicinity.
Abstract: Majority of tool-paths for high-speed machining is composed of series of short linear segments, so-called G01 moves. This discrete tool-path format limits the achievable speed and accuracy of CNC machines. To generate continuous feed motion along sharp cornered tool-paths, most NC systems smooth corners locally using a pre-specified curve or a spline and slow down to be able to change the feed direction within machine kinematic limits. Path speed is dramatically reduced for accuracy if sharp corners are within close vicinity. This paper proposes a new real-time interpolation algorithm for NC systems to generate continuous rapid feed motion along short segmented linear tool-paths by smoothing local and adjacent corners that are within close vicinity. Instead of locally modifying the corner geometry with a spline, the proposed algorithm directly blends axis velocities between consecutive linear segments based on the jerk limited acceleration profile (JLAP) and generates cornering trajectories within user-specified contour errors and kinematic limits of the drives. A novel Look-Ahead Windowing (LAW) technique is developed to plan tangential feed profile with uninterrupted acceleration to continuously smooth the path. The feed profile is optimized to generate rapid motion along overlapping adjacent corners. Simulation and experimental results demonstrate effectiveness of the proposed method to interpolate accurate Cartesian high-speed motion along short-segmented tool-paths for machining free-form surfaces found in dies, molds and aerospace parts.
TL;DR: Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises.
Abstract: This paper investigates the problem of spatial curvilinear path following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties. Firstly, in order to design the appropriate controller, path following error dynamics model is constructed in a moving Serret–Frenet frame, and the five degrees of freedom (DOFs) dynamic model with multiple uncertainties is established. Secondly, the proposed control law is separated into kinematic controller and dynamic controller via back-stepping technique. In the case of kinematic controller, to overcome the drawback of dependence on the accurate vehicle model that are present in a number of path following control strategies described in the literature, the unknown side-slip angular velocity and attack angular velocity are treated as uncertainties. Whereas in the case of dynamic controller, the model parameters perturbations, unknown external environmental disturbances and the nonlinear hydrodynamic damping terms are treated as lumped uncertainties. Both kinematic and dynamic uncertainties are estimated and compensated by designed reduced-order linear extended state observes (LESOs). Thirdly, feedback linearization (FL) based control law is implemented for the control model using the estimates generated by reduced-order LESOs. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiators (NTDs) are applied to construct derivatives of the virtual control commands. Finally, the closed loop stability for the overall system is established. Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises.
TL;DR: This paper proposes to find the kinematic base frame by solving a hand-eye calibration problem using 3D position measurements only, which avoids the inconvenience and inaccuracy of measuring orientations and thus significantly facilitates practical operations.
Abstract: When a robot is required to perform specific tasks defined in the world frame, there is a need for finding the coordinate transformation between the kinematic base frame of the robot and the world frame. The kinematic base frame used by the robot controller to define and evaluate the kinematics may deviate from the mechanical base frame constructed based on structural features. Besides, by using kinematic modeling rules such as the product of exponentials (POE) formula, the base frame can be arbitrarily located, and does not have to be related to any feature of the mechanical structure. As a result, the kinematic base frame cannot be measured directly. This paper proposes to find the kinematic base frame by solving a hand-eye calibration problem using 3D position measurements only, which avoids the inconvenience and inaccuracy of measuring orientations and thus significantly facilitates practical operations. A closed-form solution and an iterative solution are explicitly formulated and proved effective by simulations. Comprehensive analyses of the impact of key parameters to the accuracy of the solution are also carried out, providing four guidelines to better conduct practical operations. Finally, experiments on a 7-DOF industrial robot are performed with an optical tracking system to demonstrate the superiority of the proposed method using position data only over the method using full pose data.
TL;DR: In this article, a 3-DOF planar parallel manipulator with two kinematic chains connecting the moving platform to the base can reduce interference while still maintaining 3 DOF.
Abstract: The paper deals with the workspace and dynamic performance evaluation of the PRR-PRR parallel manipulator in spray-painting equipment. Functional workspace of planar fully parallel robots is often limited because of interference among their mechanical components. The proposed 3-DOF planar parallel manipulator with two kinematic chains connecting the moving platform to the base can reduce interference while still maintaining 3 DOFs. Based on the kinematics, four working modes are analyzed and singularity is studied. The workspace is investigated and the inverse dynamics is formulated using the virtual work principle. The dynamic performance evaluation indices are designed on the basis of maximum and minimum magnitude of acceleration vector of the moving platform produced by a unit actuated force. The index not only can evaluate the accelerating performance of a manipulator, but also can reflect the isotropy of accelerating performance. Workspace and dynamic performances of the four working modes are compared and the optimal working mode for the painting of a large object with conical surface is determined. HighlightsFour working modes are analyzed and the optimal mode for painting a long rocket fairing with conical surface is determined.Dynamic performance indices are designed on the basis of acceleration vector of the moving platform produced by a unit actuated force.The index not only can evaluate the accelerating performance, but also can reflect the isotropy of accelerating performance.
TL;DR: In this paper, an anthropomorphic robotic hand named KITECH-Hand adopts a new "roll-pitch"-type MCP structure to replace conventional "yaw pitch" structures, which provides benefits such as enhanced kinematic performance and ease of the mechanical design.
Abstract: This paper presents an anthropomorphic robotic hand named “KITECH-Hand,” along with its kinematic analysis and detailed mechanical features. From a kinematic perspective, the authors particularly focus on the structure of the metacarpophalangeal (MCP) joints of the fingers. The KITECH-Hand adopts a new “roll–pitch”-type MCP structure to replace conventional “yaw–pitch” structures. The proposed structure provides benefits such as enhanced kinematic performance and ease of the mechanical design. Through the kinematic analysis, it is shown that the KITECH-Hand shows remarkably high dexterity, well surpassing that of existing robotic hands with conventional MCP joints. The unique MCP structure also helps modularize the robot at the joint level, which simplifies its mechanical structure and enables the production cost to be reduced. The performance of the KITECH-Hand, including its dexterity feature, was experimentally verified through a series of experiments, which included object in-hand manipulation and a Cutkosky taxonomy test.
TL;DR: In this article, the authors used the Stackel potential to constrain the kinematics of the thin and thick disks using the Besancon population synthesis model together with RAVE DR4 and Gaia first data release (TGAS).
Abstract: Aims. We attempt to constrain the kinematics of the thin and thick disks using the Besancon population synthesis model together with RAVE DR4 and Gaia first data release (TGAS).Methods. The RAVE fields were simulated by applying a detailed target selection function and the kinematics was computed using velocity ellipsoids depending on age in order to study the secular evolution. We accounted for the asymmetric drift computed from fitting a Stackel potential to orbits. Model parameters such as velocity dispersions, mean motions, and velocity gradients were adjusted using an ABC-MCMC method. We made use of the metallicity to enhance the separation between thin and thick disks.Results. We show that this model is able to reproduce the kinematics of the local disks in great detail. The disk follows the expected secular evolution, in very good agreement with previous studies of the thin disk. The new asymmetric drift formula, fitted to our previously described Stackel potential, fairly well reproduces the velocity distribution in a wide solar neighborhood. The U and W components of the solar motion determined with this method agree well with previous studies. However, we find a smaller V component than previously thought, essentially because we include the variation of the asymmetric drift with distance to the plane. The thick disk is represented by a long period of formation (at least 2 Gyr), during which, as we show, the mean velocity increases with time while the scale height and scale length decrease, very consistently with a collapse phase with conservation of angular momentum. Conclusions. This new Galactic dynamical model is able to reproduce the observed velocities in a wide solar neighborhood at the quality level of the TGAS-RAVE sample, allowing us to constrain the thin and thick disk dynamical evolution, as well as determining the solar motion.
TL;DR: In this paper, a 2-DOF manipulator is attached to the bottom of a quadrotor to enable the end-effector to track a desired 6DOF trajectory with minimum possible actuators.
Abstract: The research on aerial manipulation has increased rapidly in recent years. In the previous work, a manipulator or a gripper is attached to the bottom of a quadrotor to facilitate the interaction with the environment. However, the previously introduced systems suffer from either limited end-effector degrees of freedom (DOF) or small payload capacity. In this paper, a quadrotor with a 2-DOF manipulator that has a unique topology to enable the end-effector to track a desired 6-DOF trajectory with minimum possible actuators is investigated. The proposed system is designed and modeled. However, such a system produces complexity in its inverse kinematics and control. A novel solution to the inverse kinematics problem is presented, which requires a solution of complicated algebraic/differential equations. Its accuracy is verified via numerical results. In order to solve the control problem, the system nonholonomic constraints are utilized with a model-free and low computation cost robust control technique. Moreover, the system stability proof under the proposed controller is carried out. A prototype of the proposed system is built and its design is verified via a flight test. In addition, the system feasibility and efficiency are enlightened.
06 Jul 2017
TL;DR: In this paper, a vertex-based representation of the support area constraint is introduced, which can treat arbitrarily oriented point-, line-, and area-contacts uniformly, allowing to generate diverse motions such as quadrupedal walking, trotting, bounding, pacing, combinations, and transitions between these.
Abstract: This letter combines the fast zero-moment-point approaches that work well in practice with the broader range of capabilities of a trajectory optimization formulation, by optimizing over body motion, footholds, and center of pressure simultaneously. We introduce a vertex-based representation of the support-area constraint, which can treat arbitrarily oriented point-, line-, and area-contacts uniformly. This generalization allows us to create motions, such as quadrupedal walking, trotting, bounding, pacing, combinations, and transitions between these, limping, bipedal walking, and push recovery all with the same approach. This formulation constitutes a minimal representation of the physical laws (unilateral contact forces) and kinematic restrictions (range of motion) in legged locomotion, which allows us to generate diverse motions in less than a second. We demonstrate the feasibility of the generated motions on a real quadruped robot.
TL;DR: An overview of the different upper limb models available in the literature and a discussion about their applicability to Multibody kinematics optimisation (MKO) is proposed.
TL;DR: The leg mechanism of the novel jumping robot, Salto, is designed to achieve multiple functions during the sub-200ms time span that the leg interacts with the ground, including minimizing impulse loading, balancing angular momentum, and manipulating power output of the robot’s series-elastic actuator with a single degree-of-freedom linkage that has a coupled, unintuitive design.
Abstract: The leg mechanism of the novel jumping robot, Salto, is designed to achieve multiple functions during the sub-200ms time span that the leg interacts with the ground, including minimizing impulse loading, balancing angular momentum, and manipulating power output of the robot’s series-elastic actuator. This is all accomplished passively with a single degree-of-freedom linkage that has a coupled, unintuitive design which was synthesized using the technique described in this paper. Power delivered through the mechanism is increased beyond the motor’s limit by using variable mechanical advantage to modulate energy storage and release in a series-elastic actuator. This power modulating behavior may enable high amplitude, high frequency jumps. We aim to achieve all required behaviors with a linkage composed only of revolute joints, simplifying the robot’s hardware but necessitating a complex design procedure since there are no pre-existing solutions. The synthesis procedure has two phases: (1) design exploration to initially compile linkage candidates, and (2) kinematic tuning to incorporate power modulating characteristics and ensure an impulse-limited, rotation-free jump motion. The final design is an eight-bar linkage with a stroke greater than half the robot’s total height that produces a simulated maximum jump power 3.6 times greater than its motor’s limit. A 0.27m tall prototype is shown to exhibit minimal pitch rotations during meter high test jumps. [DOI: 10.1115/1.4035117]