Kinematic Structure Research Articles

A novel inverse dynamic model for 3-DoF delta robots

Delta Robots belong to a class of parallel robots widely used in industrial production processes, mostly for pick-and-place operations. The most relevant characteristics are the high speed and the extremely favorable ratio between the maximum payload and the weight of the robot itself. A reliable dynamic model is needed to implement torque controllers that reduce unnecessary high accelerations and so mechanical vibrations. The state-of-art inverse dynamic models exploit simplifications in order to facilitate the derivation of the equations of motion and their implementation. In this work, a novel and more rigorous inverse dynamic model is presented which does not rely on simplifications of the kinematic structure. The model has been validated comparing its estimations with real torques data collected moving a Delta Robot D3-1200 by SIPRO Srl; the computational complexity of the algorithm has also been investigated.

Thermodynamic and Kinematic Structures in the Rainband Region of Typhoon Lekima (2019) at Landfall

Super Typhoon Lekima (2019) was the third strongest tropical cyclone (TC) that has ever made landfall in Jiangsu and Zhejiang Provinces, China. During its passage, the storm resulted in catastrophic disasters to mainland China, which made it one of the costliest typhoons in Chinese history. This article presents an observational study on the thermodynamic and kinematic structures of Typhoon Lekima at landfall, mainly based on measurements from radiosonde balloons that were released at different periods from a coastal site located with a nearest distance of ~200 km to the track of Lekima. Observations from a weather radar are first discussed to demonstrate the horizontal structure of the typhoon, and the concentric eyewall structure of Lekima is highlighted. Then, Lekima’s pressure field is analyzed, and a two-dimensional model is proposed to quantify both the radial and height dependence of the pressure distribution. The subsequent analysis focuses on the warm-core like structure in the rainband region. The maximum perturbation of measured equivalent potential temperature with respect to the one of environment reached 25 K at ~5 km. Some factors contributing to the warm-core like feature are discussed. The authors of this article finally investigate the TC wind field. Low-level jets of vertical wind profile in rainband areas were observed at heights of around 1–3 km. Dramatic wind shears were observed in the range of 15–17 km where the outflow layer existed, while wind became considerably weak at the tropopause.

Mechanical design and friction modelling of a cable-driven upper-limb exoskeleton

This paper presents a lightweight and low-inertia cable-driven upper-limb exoskeleton powerful enough to meet the requirements for activities of daily living. It presents the mechanical design, kinematic structure,the underlying actuation system, sensors, other electronic components as well as the controller of the exoskeleton.The extensive effect of friction on cable-driven designs, such as the one presented in this paper, requires proper mathematical modelling for controller design. Thus, we propose a current actuator model that describes the relationship between the motor current, velocity, and external load. The model relies on an underlying Stribeck+Coulomb friction representation and an additional parameter that modifies its Coulomb friction representation with an offset to represent adhesion between a cable and sheath.The model has been validated based on experimental data collected with the exoskeleton. The results show that the proposed model better captures the non-linear behaviour of the exoskeleton’s actuation system, increasing overall descriptive performance by 15%. However, adding the adhesion offset to extend the relation of static friction, does not improve the model.

Kinematic-Model-Free Predictive Control for Robotic Manipulator Target Reaching With Obstacle Avoidance.

Model predictive control is a widely used optimal control method for robot path planning and obstacle avoidance. This control method, however, requires a system model to optimize control over a finite time horizon and possible trajectories. Certain types of robots, such as soft robots, continuum robots, and transforming robots, can be challenging to model, especially in unstructured or unknown environments. Kinematic-model-free control can overcome these challenges by learning local linear models online. This paper presents a novel perception-based robot motion controller, the kinematic-model-free predictive controller, that is capable of controlling robot manipulators without any prior knowledge of the robot’s kinematic structure and dynamic parameters and is able to perform end-effector obstacle avoidance. Simulations and physical experiments were conducted to demonstrate the ability and adaptability of the controller to perform simultaneous target reaching and obstacle avoidance.

The Detection of a Massive Chain of Dark H i Clouds in the GAMA G23 Field

Abstract We report on the detection of a large, extended H i cloud complex in the Galaxy and Mass Survey G23 field, located at a redshift of z ∼ 0.03, observed as part of the MeerKAT Habitat of Galaxies Survey campaign (a pilot survey to explore the mosaicing capabilities of the MeerKAT telescope). The cloud complex, with a total mass of 1010.0 M ⊙, lies in proximity to a large galaxy group with M dyn ∼ 1013.5 M ⊙. We identify seven H ɪ peak concentrations, interconnected as a tenuous chain structure, extending ∼400 kpc from east to west, with the largest (central) concentration containing 109.7 M ⊙ in H ɪ gas distributed across 50 kpc. The main source is not detected in ultraviolet, optical, or infrared imaging. The implied gas mass-to-light ratio (M H I/L r) is extreme (>1000) even in comparison to other dark clouds. The complex has very little kinematic structure (110 km s−1), making it difficult to identify cloud rotation. Assuming pressure support, the total mass of the central concentration is > 1010.2 M ⊙, while a lower limit to the dynamical mass in the case of full rotational support is 1010.4 M ⊙. If the central concentration is a stable structure, it has to contain some amount of unseen matter, but potentially less than is observed for a typical galaxy. It is, however, not clear whether the structure has any gravitationally stable concentrations. We report a faint UV-optical-infrared source in proximity to one of the smaller concentrations in the gas complex, leading to a possible stellar association. The system nature and origins is enigmatic, potentially being the result of an interaction with or within the galaxy group it appears to be associated with.

Molecules, shocks, and disk in the axi-symmetric wind of the MS-type AGB star RS Cancri

Context. The latest evolutionary phases of low- and intermediate-mass stars are characterized by complex physical processes like turbulence, convection, stellar pulsations, magnetic fields, condensation of solid particles, and the formation of massive outflows that inject freshly produced heavy elements and dust particles into the interstellar medium. Aims. By investigating individual objects in detail, we wish to analyze and disentangle the effects of the interrelated physical processes on the structure of the wind-forming regions around them. Methods. We use the Northern Extended Millimeter Array to obtain spatially and spectrally resolved observations of the semi-regular asymptotic giant branch (AGB) star RS Cancri and apply detailed 3D reconstruction modeling and local thermodynamic equilibrium radiative transfer calculations in order to shed light on the morpho-kinematic structure of its inner, wind-forming environment. Results. We detect 32 lines of 13 molecules and isotopologs (CO, SiO, SO, SO2, H2O, HCN, PN), including several transitions from vibrationally excited states. HCN, H13CN, and millimeter vibrationally excited H2O, SO, 34SO, SO2, and PN are detected for the first time in RS Cnc. Evidence for rotation is seen in HCN, SO, SO2, and SiO(v = 1). From CO and SiO channel maps, we find an inner, equatorial density enhancement, and a bipolar outflow structure with a mass-loss rate of 1 × 10−7 M⊙yr−1 for the equatorial region and of 2 × 10−7 M⊙yr−1 for the polar outflows. The 12CO/13CO ratio is measured to be ~20 on average, 24 ± 2 in the polar outflows and 19 ± 3 in the equatorial region. We do not find direct evidence of a companion that might explain this kind of kinematic structure, and explore the possibility that a magnetic field might be the cause of it. The innermost molecular gas is influenced by stellar pulsation and possibly by convective cells that leave their imprint on broad wings of certain molecular lines, such as SiO and SO. Conclusions. RS Cnc is one of the few nearby, low-mass-loss-rate, oxygen-rich AGB stars with a wind displaying both an equatorial disk and bipolar outflows. Its orientation with respect to the line of sight is particularly favorable for a reliable study of its morpho-kinematics. Nevertheless, the mechanism causing early spherical symmetry breaking remains uncertain, calling for additional high spatial- and spectral-resolution observations of the emission of different molecules in different transitions, along with more thorough investigation of the coupling among the different physical processes at play.

Examining the Kinematic Structures within which Lightning Flashes Are Initiated Using a Cloud-Resolving Model

Abstract Lightning is frequently initiated within the convective regions of thunderstorms, and so flash rates tend to follow trends in updraft speed and volume. It has been suggested that lightning production is linked to the turbulent flow generated by updrafts as turbulent eddies organize charged hydrometeors into complex charge structures. These complex charge structures consist of local regions of increased charge magnitudes between which flash-initiating electric fields may be generated. How turbulent kinematics influences lightning production, however, remains unclear. In this study, lightning flashes produced in a multicell and two supercell storms simulated using The Collaborative Model for Multiscale Atmospheric Simulation (COMMAS) were examined to identify the kinematic flow structures within which they occurred. By relating the structures of updrafts to thermals, initiated lightning flashes were expected to be located where the rate of strain and rotational flow are equal, or between updraft and eddy flow features. Results showed that the average lightning flash is initiated in kinematic flow structures dominated by vortical flow patterns, similar to those of thermals, and the structures’ kinematics are characterized by horizontal vorticity and vertical shearing. These kinematic features were common across all cases and demonstrated that where flash-initiating electric fields are generated is along the periphery of updrafts where turbulent eddies are produced. Careful consideration of flow structures near initiated flashes is consistent with those of thermals rising through a storm.

Substructure at High Speed. I. Inferring the Escape Velocity in the Presence of Kinematic Substructure

Abstract The local escape velocity provides valuable inputs to the mass profile of the galaxy, and requires understanding the tail of the stellar speed distribution. Following Leonard & Tremaine, various works have since modeled the tail of the stellar speed distribution as ∝ ( v esc − v ) k , where v esc is the escape velocity, and k is the slope of the distribution. In such studies, however, these two parameters were found to be largely degenerate and often a narrow prior is imposed on k in order to constrain v esc. Furthermore, the validity of the power-law form can breakdown in the presence of multiple kinematic substructures or other mis-modeled features in the data. In this paper, we introduce a strategy that for the first time takes into account the presence of kinematic substructure. We model the tail of the velocity distribution as a sum of multiple power laws as a way of introducing a more flexible fitting framework. Using mock data and data from FIRE simulations of Milky Way-like galaxies, we show the robustness of this method in the presence of kinematic structure that is similar to the recently discovered Gaia Sausage. In a companion paper, we present the new measurement of the escape velocity and subsequently the mass of the Milky Way using Gaia eDR3 data.

Choice of Kinematic Structure of Modular Robotic System Depending on the Type of Motion Surface

Purpose of research. The purpose of this study is to identify the advantages and disadvantages of various kinematic structures (formations) of self-reconfigurable modular robotic systems depending on the type of surface over which the system is mainly to be moved.Methods. Analysis of kinematic structures of modular robotic systems with respect to their displacement capabilities was carried out. Features of movement of these formations on different surfaces, as well as features of application of some formations are highlighted. A study of functionality of its own mobile autonomous reconfigurable system was carried out on the basis of described formations.Results. According to the results of the study, the main structures of modular robotic systems were identified, among which the most popular are formations that have a chain architecture: "snake," "manipulator"; "walking" structures: "quadropod," "spider," "centipede," as well as mobile structures "machine," "wheel" and "ball." Based on the conducted analysis, structures were developed for their own modular robotics system. Geometric features and kinematic limitations of its modules were considered in developing the structuresConclusion. The use of the analysis results will allow better adaptation of a modular self-reconfigurable robotic system to the surface on which this system moves. The selection of a particular formation of the modular system is also influenced by the required speed of movement over a given surface. Walking formations have the greatest adaptability to various types of surfaces, but they are also the most difficult from the point of view of control system developing.

Negative and positive feedback from a supernova remnant with SHREC: a detailed study of the shocked gas in IC443

ABSTRACT Supernova remnants (SNRs) contribute to regulate the star formation efficiency and evolution of galaxies. As they expand into the interstellar medium (ISM), they transfer vast amounts of energy and momentum that displace, compress, and heat the surrounding material. Despite the extensive work in galaxy evolution models, it remains to be observationally validated to what extent the molecular ISM is affected by the interaction with SNRs. We use the first results of the ESO–ARO Public Spectroscopic Survey SHREC to investigate the shock interaction between the SNR IC443 and the nearby molecular clump G. We use high-sensitivity SiO(2-1) and H13CO+(1-0) maps obtained by SHREC together with SiO(1-0) observations obtained with the 40-m telescope at the Yebes Observatory. We find that the bulk of the SiO emission is arising from the ongoing shock interaction between IC443 and clump G. The shocked gas shows a well-ordered kinematic structure, with velocities blue-shifted with respect to the central velocity of the SNR, similar to what observed towards other SNR–cloud interaction sites. The shock compression enhances the molecular gas density, n(H2), up to >105 cm−3, a factor of >10 higher than the ambient gas density and similar to values required to ignite star formation. Finally, we estimate that up to 50 per cent of the momentum injected by IC443 is transferred to the interacting molecular material. Therefore, the molecular ISM may represent an important momentum carrier in sites of SNR–cloud interactions.

Evaluation and Modification of Microphysics Schemes on the Cold Pool Evolution for a Simulated Bow Echo in Southeast China

AbstractA merger‐formation bow echo (MFBE) in southeast China during the pre‐summer rainy season (PSRS) was simulated using three microphysics schemes including Thompson (THOM), Morrison (MORR), and Weather Research and Forecasting Double‐Moment 6‐Class (WDM6) schemes to compare against polarimetric observations and Variational Doppler Radar Analysis System (VDRAS) analyses. The three schemes captured the basic kinematic structures for this MFBE event after assimilating radar radial velocities, but all underpredicted the cold pool strength by ∼25%. Particularly, THOM produced the best raindrop size distributions (DSDs) and precipitation pattern compared with observed retrievals; further analyses indicated the larger raindrop size bias and the weak cold pool strength in THOM were owing to the relatively low rain breakup efficiency and inefficient rain evaporation, respectively. By decreasing the cutoff diameter of rain breakup parameterization from the default 1.6–1.2 mm (i.e., increasing breakup efficiency) and increasing evaporation efficiency by threefold in THOM, the simulated DSDs and precipitation were greatly improved, and the cold pool strength was significantly increased from 77% to 99% compared to that in VDRAS analyses. This study illustrated a plausible approach of combining polarimetric radar retrievals and VDRAS analyses as bases to adjust THOM default settings in simulating a MFBE event in southeast China with physical characteristics more consistent with observations. Since microphysical processes vary from convective organizations and climate regions, it is recognized more cases studies are needed in the future to examine the validity and approach in this study to improve simulations and predictions of MFBEs in southeast China.

Globally-optimal whole body motion planning under nonholonomic constraints using dynamic programming

Robotics is a key enabler for many applications in space including planetary exploration, On-Orbit Servicing (OOS), In-Space Manufacturing (ISM), Active Space Debris Removal (ADR) and deep space exploration. They are usually characterized by limited resources, which requires the robotic system to be controlled according to criteria of optimality. How to perform operations and plan the robot motion are then key factors to ensure feasibility and efficiency. This work analyzes and extends a recently proposed Dynamic Programming Optimization (DPO) algorithm for off-line motion planning in the context of planetary colonization, ranging from exploration to terrain preparation and construction. The algorithm is designed to be run on ground with the aim of (1) limiting spacecraft cost and (2) optimally plan complex tasks with medium to long term time horizons before or during mission. The analysis is performed on a robotic system including a six degree of freedom manipulator mounted on a nonholonomic base which is exercised on tasks that leave more than one degree of redundancy. The planning tasks are resolved without decomposition, allowing the algorithm to optimize the motion of the whole kinematic structure. Redundancy is exploited to optimize the cost function of interest, while considering any constraint the robotic asset and the surrounding environment are characterized by. In our use case, the optimization is performed on a cost function associated to energy consumption. A tradeoff analysis of the solution quality versus the computational resources requirements is provided. Finally, we highlight the advantages of the proposed algorithm with respect to a standard planning approach based on decomposition of the planning problem in two sub-problems: the first involving the planning of the mobile base according to some heuristics (e.g. reachability) and the second involving the planning of the manipulator.

Embodying Meaning Visually: From Perceptual Dynamics to Motion Kinematics

Abstract This paper adopts an embodied cognitive perspective to review the significance of dynamic patterns in the visual expression of meaning. Drawing upon the work of Rudolf Arnheim we first show how perceptual dynamics of inanimate objects might be extended in order to structure abstract meaning in fixed images such as paintings. Second, we evaluate existing experimental work that shows how simple kinematic structures within a stationary frame might embody such high-level properties as perceptual causality and animacy. Third and last, we take inspiration from these experiments to shed light on the expressiveness of dynamic patterns that unfold once the frame itself becomes a mobile entity (i.e., camera movement). In the latter case we will also present a filmic case study, showing how filmmakers might resort to these dynamic patterns so as to embody a film’s story content, while simultaneously offering a further avenue for film scholars to deepen their engagement with the experimental method.

Precision optimized pose and trajectory planning for vertically articulated robot arms

Vertically articulated robot arms are widely used in various industries for the realization of conventional handling tasks due to their high flexibility, good workspace-to-footprint ratio and low price. However, due to their kinematic structure, their accuracy, precision and stiffness are highly dependent on the robots configuration. Standards such as EN-ISO-9283 define procedures for determining accuracy and precision by averaging measurements at different points in the robot’s main workspace. While these averages can be used to estimate the robots overall performance, they do not support process developers in identifying precision optimal poses. This paper presents a generic and comprehensive routine for the combined identification of precision-optimal robot poses and trajectories for pick and place processes. The routine consists of several cascading optimization loops with the objectives of minimizing the structural and dimensional sensitivity costs of the trajectories’ start and end configurations, minimizing the number of actuated joints and minimizing the required direction changes of the joints in motion. Using a sampling-based trajectory planner (OMPL in MoveIt! / ROS), a smooth and collision free trajectory for an exemplary pick and place process is generated and experimentally validated for a KUKA LWR iiwa 14. The optimized trajectory is benchmarked against a conventional, unoptimized reference trajectory for the same handling task. The experimental validation shows a significant increase in the repeatability of the positioning of 36µm (at 3σ) compared to both the nominal repeatability of 150µm and the repeatability of the reference trajectory of 94µm (at 3σ, 2.6-fold increase). Transferring the developed routine to inherently more precise robot models will lead to highly precise vertically articulated robot arms capable of solving more demanding assembly tasks.

Razvoj sistema za programiranje i simulaciju 4-osnog robota sa hibridnom kinematikom

This paper presents an approach for developing the programming and offline simulation systems for low-cost industrial robots in the MatLab/Simulink environment. The approach is presented in the example of a virtual model of a 4-axis robot with hybrid kinematics intended for manipulation tasks. The industrial robot with hybrid kinematics consists of the well-known 5R planar parallel mechanism to which two serial axes have been added. The programming system developed in a MatLab environment involves generating G-code programs based on given pick and place points. The virtual model included in the simulation system is configured in the Simulink environment based on the CAD model of the robot and its kinematic structure. The kinematic model and the inverse kinematic problem have to be included in the virtual model to realize the motion of the virtual robot. The system of programming and simulation has been verified through several examples that include object manipulation to perform various tasks.

Toward Real-World Category-Level Articulation Pose Estimation.

Human life is populated with articulated objects. Current Category-level Articulation Pose Estimation (CAPE) methods are studied under the single-instance setting with a fixed kinematic structure for each category. Considering these limitations, we aim to study the problem of estimating part-level 6D pose for multiple articulated objects with unknown kinematic structures in a single RGB-D image, and reform this problem setting for real-world environments and suggest a CAPE-Real (CAPER) task setting. This setting allows varied kinematic structures within a semantic category, and multiple instances to co-exist in an observation of real world. To support this task, we build an articulated model repository ReArt-48 and present an efficient dataset generation pipeline, which contains Fast Articulated Object Modeling (FAOM) and Semi-Authentic MixEd Reality Technique (SAMERT). Accompanying the pipeline, we build a large-scale mixed reality dataset ReArtMix and a real world dataset ReArtVal. Accompanying the CAPER problem and the dataset, we propose an effective framework that exploits RGB-D input to estimate part-level pose for multiple instances in a single forward pass. In our method, we introduce object detection from RGB-D input to handle the multi-instance problem and segment each instance into several parts. To address the unknown kinematic structure issue, we propose an Articulation Parsing Network to analyze the structure of detected instance, and also build a Pair Articulation Pose Estimation module to estimate per-part 6D pose as well as joint property from connected part pairs. Extensive experiments demonstrate that the proposed method can achieve good performance on CAPER, CAPE and instance-level Robot Arm pose estimation problems. We believe it could serve as a strong baseline for future research on the CAPER task. The datasets and codes in our work will be made publicly available.

MECHANICAL DESIGN, ACTUATION AND CONTROL OF BIOINSPIRED SOFT SURGICAL ROBOTS

The design of surgical soft robots is one of the most challenging problems in modern robotics. In addition to the still pending problems of general soft robotics i.e. selection/design of materials, actuators, and mechanical structures, there are serious limitations in terms of their operating environment and conditions: interaction with biological tissues, the effect of sterilization and cleaning liquids, the shape and dimensions of the working space, as well as often occurring accidents during the surgery which poses new robotic control problems to be studied. As it is known, each object of bioinspiration (elephant trunk, octopus leg, etc.) has its own type of motion, kinematic structure, and control, therefore the comparative analysis of soft robots according to different objects of bioinspiration will facilitate their selection and application in minimally invasive surgery (MIS), taking into account, of course, the limitations associated with the surgery. A review of modern literature on mechanical design, methods and technical means of actuation and control of the main types of bioinspired soft surgical robots is presented.The design and development problems, including material selection, mechanical design and optimization, actuation, and bioinspired control for each type of the existing soft surgical robots are discussed. The results and recommendations of this study will help to develop new samples of soft surgical robotic devices with task-specific functional characteristics necessary for MIS applications.

ПРОЯВЛЕНИЕ ВЕСТИБУЛЯРНОЙ УСТОЙЧИВОСТИ В СТРУКТУРЕ ОТДЕЛЬНЫХ ПАРАМЕТРОВ ДВИГАТЕЛЬНО-КООРДИНАЦИОННЫХ СПОСОБНОСТЕЙ ЗАНИМАЮЩИХСЯ СПОРТИВНЫМИ ВИДАМИ ЕДИНОБОРСТВ

The problem of vestibular stability displaying is considered depending on individual parameters of motor-coordination abilities of those practicing martial arts. Methods and organization of the research. 161 male athletes engaged in kickboxing, boxing, karate, hand-to-hand fighting, sports wrestling, etc. took part in the testing. The average age was 21.3 years old, the average experience – 9.5 years. This group of athletes was divided into two subgroups: the first one with a high level of vestibular stability, the other one – with a low level of vestibular stability. Studying the parameters of motor-coordination abilities was conducted according to a ten-point scale; symmetry-asymmentry of athletes’ limbs was conducted according to a six-point scale and the subjective assessment of an athlete. The integral indicator of motor-coordination abilities was determined by the sum of points of all parameters studied. Sportsmanship was assessed according to one hundred-point scale. Research results. It is revealed that the group with a higher level of vestibular stability is different from the group with a low level of vestibular stability at a reliable level towards higher values in the following parameters: speed of change of motor actions; time differentiation of individual phases of technical action; orientation in space; coordination of different body parts’ movements; stability of the kinematic movement structure; accuracy of spatial characteristics; preservation of stability; integral indicator of movement coordination. There were also significant differences in the parameters of symmetry and asymmetry of performing technical actions in a duel, mainly with both arms or both legs. In regard to the influence of the level of sportsmanship and the experience of sports on the display of vestibular static-dynamic stability, there were no significant differences between the groups. Conclusion. The features of vestibular stability manifestation in the structure of individual parameters of motor-coordination abilities of those engaged in martial arts are revealed.

Conceptual Design and Simulation of Cable-driven Parallel Robot for Inspection and Monitoring Tasks

The paper deals with the conceptual design of cable-driven parallel robot which will be used for inspection and monitoring tasks in production process. The reason and need of vision based control of the production process is described in the introduction. Furthermore, mechanisms with parallel kinematic structure are described, as well as their usage in industry and sports broadcasts. On that basis, there is proposed the conceptual design of the cable driven parallel robot (CDPR) for desired task of visual monitoring of production line. Finally, there is proposed a simulation of designed robotic system and workspace shape analysis.

Формула расхода воды через плоский щитовой затвор в открытом русле

The purpose of the research is to analyze the influence of the flow kinematic structure on the measuring accuracy of the water flow through the flat sluice gate in the open channel. For the simulation and analysis of the flow through the sluice gate, the DisCo4 software-computer complex developed by the author was used based on the numerical solution of the system of equations (RANS) and continuity by the finite volume method in the three-dimensional formulation. It was found that installation of the sluice gate on the thin transverse wall can signifi cantly reduce the effect of the channel bottom roughness on the water flow through the gate. The analytical formula for discharge through the flat sluice gate of the considered structure is proposed. Regardless of the channel roughness, the scatter of calculated discharges in the range of ratios of the height of the hole to the depth relative to the lower edge of the hole Hg /H < 0.3 is no more than 3%.