Virtual Kinematic Research Articles

Optimal Design and Dynamic Characteristic Analysis of Double-Link Trapezoidal Suspension for 3WPYZ High Gap Self-Propelled Sprayer

A fast spraying speed, wide working area, and easy operation are the operational advantages of high-clearance boom sprayers. To address the issue of spray boom mechanical vibration affecting the spraying effect, a double-link trapezoidal boom suspension is designed for the 3WPYZ sprayer. This suspension can achieve passive vibration reduction, active balance, and ground profiling. The kinematic model of the boom suspension is established based on D’Alembert’s principle and the principle of multi-body dynamics, and the design factors affecting the stability of the boom are determined. Through orthogonal experimental design and virtual kinematics simulation, the influence of the boom length and orifice diameter of each part on the swing angle and the natural frequency of the boom suspension is investigated. Design-Expert 8.0.6 software is used to analyze and optimize the test results. The optimization results show that, when the connecting boom length LAB is 265 mm, the inner boom suspension boom length LAD is 840 mm, the outer boom suspension boom length LBC is 1250 mm, and the throttle hole diameter d is 4 mm; the maximum swing angle of the boom suspension is reduced by 53.02%. In addition, the natural frequency of the boom is reduced from 1.3143 rad/s to 1.1826 rad/s, and the dynamic characteristic optimization effect is remarkable. The modal analysis results show that the first sixth-order vibration test frequency of the boom sprayer suspension designed in this paper meets the requirements and avoids the influence of external factors. Field tests show that, when the sprayer is excited by the environment at 3.5° to 4°, the boom suspension can reduce the vibration transmitted by the body to a reasonable range. The static analysis shows that the structural design of this study reduces the stress at the connection of the end boom suspension, the maximum displacement, and the maximum stress of the inner boom suspension. The test results of the dynamic characteristics of the implement are basically consistent with the virtual model simulation test results, thus achieving the optimization objectives.

Design and optimization of a novel sagittal-plane knee exoskeleton with remote-center-of-motion mechanism

Powered exoskeleton is a wearable robot that can provide power-assisted motion for the human body. One of the challenges in the exoskeleton research is how to improve its kinematic synergy. In this paper, a novel knee exoskeleton robot is designed to improve the kinematic synergy between the exoskeleton and the human body. The novel exoskeleton adopts the sagittal-plane layout to reduce the bias moment, and uses a remote-center-of-rotation mechanism to ensure the coincidence of the rotation centers of the exoskeleton and the human body. To analyze the influence of the interaction error on the performance of the exoskeleton, this paper proposes a human-exoskeleton fusion model based on the virtual equivalent parallel mechanism method, and parameterize the interaction error through virtual kinematic chains. Finally, the assisting performance of the novel exoskeleton is analyzed and verified through simulation experiments, motion experiments, body motion experiments and human simulation experiments. The human-exoskeleton fusion model proposed in this paper has positive significance for the configuration design, biomechanical analysis and application of exoskeleton robots.

Идентификация искажения формы цилиндрических деталей технологических агрегатов

The paper deals with the issues arising during the technological unit operation, in particular, the geometric characteristics control of large parts of the units. The main types of rolling the surface wear of cylindrical elements of various technological equipment are given (according to GOST 24642-81, GOST 18322-2016). The equipment wear patterns due to the operating conditions and the unit design, as well as differences in the part shape distortion with the roundness loss are highlighted. It is revealed that the uneven wear of the rolling surface of the technological cylindrical parts causes shape distortion. Considering this, the profile of a conditional round part in cross section relative to one centre is modelled. The appearance of ovality is accepted as the main defect of cylindrical parts. A calculation scheme is presented for constructing the distortion of the cylindrical body profile located on two round supports. An algorithm for computing the radii centre displacement is presented. Theoretical calculations and the algorithm are confirmed by a virtual kinematic model that displays rolling a non-circular body on two idlers. The method described in the paper for obtaining a visual kinematic model, based on an analytical description of rolling a non-circular body, is proposed to be used as a direct problem of searching for instantaneous centres of rotation. The kinematic model obtained by solving the direct problem can be applied for training a neural network that processes the measurement results of a real rolling body

Positive Effect of Manipulated Virtual Kinematic Intervention in Individuals with Traumatic Stiff Shoulder: A Pilot Study.

Virtual reality enables the manipulation of a patient’s perception, providing additional motivation to real-time biofeedback exercises. We aimed to test the effect of manipulated virtual kinematic intervention on measures of active and passive range of motion (ROM), pain, and disability level in individuals with traumatic stiff shoulder. In a double-blinded study, patients with stiff shoulder following proximal humerus fracture and non-operative treatment were randomly divided into a non-manipulated feedback group (NM-group; n = 6) and a manipulated feedback group (M-group; n = 7). The shoulder ROM, pain, and disabilities of the arm, shoulder and hand (DASH) scores were tested at baseline and after 6 sessions, during which the subjects performed shoulder flexion and abduction in front of a graphic visualization of the shoulder angle. The biofeedback provided to the NM-group was the actual shoulder angle while the feedback provided to the M-group was manipulated so that 10° were constantly subtracted from the actual angle detected by the motion capture system. The M-group showed greater improvement in the active flexion ROM (p = 0.046) and DASH scores (p = 0.022). While both groups improved following the real-time virtual feedback intervention, the manipulated intervention provided to the M-group was more beneficial in individuals with traumatic stiff shoulder and should be further tested in other populations with orthopedic injuries.

Protean Kinematics: A Blended Model of VR Physics.

Avatar research largely focuses on the effects of the appearance and external characteristics of avatars, but may also warrant further consideration of the effects of avatar movement characteristics. With Protean kinematics, we offer an expansion the avatar-user appearances-based effects of the Proteus Effect to a systematic exploration into the role of movement in affecting social perceptions (about others) and idealized perceptions (about self). This work presents both a theoretical (typology) and methodological (physics-based measurement) approach to understanding the complex blend of physical inputs and virtual outputs that occur in the perceptual experience of VR, particularly in consideration of the collection of hippocampal (e.g., place cells, grid cells) and entorhinal neurons (e.g., speed cells) that fire topologically relative to physical movement in physical space. Offered is a novel method that distills the blend of physical and virtual kinematics to contribute to modern understandings of human-agent interaction and cognitive psychology.

Reference in-vitro dataset for inertial-sensor-to-bone alignment applied to the tibiofemoral joint

Skin-attached inertial sensors are increasingly used for kinematic analysis. However, their ability to measure outside-lab can only be exploited after correctly aligning the sensor axes with the underlying anatomical axes. Emerging model-based inertial-sensor-to-bone alignment methods relate inertial measurements with a model of the joint to overcome calibration movements and sensor placement assumptions. It is unclear how good such alignment methods can identify the anatomical axes. Any misalignment results in kinematic cross-talk errors, which makes model validation and the interpretation of the resulting kinematics measurements challenging. This study provides an anatomically correct ground-truth reference dataset from dynamic motions on a cadaver. In contrast with existing references, this enables a true model evaluation that overcomes influences from soft-tissue artifacts, orientation and manual palpation errors. This dataset comprises extensive dynamic movements that are recorded with multimodal measurements including trajectories of optical and virtual (via computed tomography) anatomical markers, reference kinematics, inertial measurements, transformation matrices and visualization tools. The dataset can be used either as a ground-truth reference or to advance research in inertial-sensor-to-bone-alignment.

Leader–follower formation source seeking control of multiple ships using sliding mode active disturbance rejection observer

In this paper, the control of multiple ships for unknown scalar field source seeking problem with unknown external disturbances is considered. The sliding mode active disturbance rejection observers are designed first to converge to fixed multiple of the unknown external disturbances in finite time, respectively, and a least square method is adopted to estimate the gradient of the unknown scalar field at the position of the leading ship. Second, the surge, sway and angle velocity of the leading ship can converge to the virtual kinematic controllers through the input control of the dynamic controllers using force and torque in finite time. Third, the virtual controllers and dynamic controllers of the following ships are developed to urge the following ships to accomplish the source seeking problem from the perspective of dynamics. Finally, theoretical proofs and simulations are provided to prove the effectiveness of the strategy proposed.

USING KINEMATIC ANALYSIS TO DEVELOP A NEW TOOTH SYSTEM FOR GEARINGS WITH VARIABLE SHAFT ANGLE

AbstractThe belt units of an omnidirectional treadmill need to be connected for a continuous rotational transmission with variating axes angle. Torus gearing is not appropriate due to kinematic reasons, therefore a crown gearing with cone-shaped teeth is proposed. Parameter analysis on a virtual kinematics model show that depending on the cone angle, overlaps occur at different axis angles. Consequently, the shape of the teeth is modified with tip and foot relief and optimized so that no overlapping of the teeth occurs while a large path of contact is provided.

Virtual strategies in the kinematic and dynamical models applied to fault-tolerant strategy of underwater vehicles by using state-dependent Riccati equations

A new kind of kinematic underwater vehicle modelling, which uses the screw theory and the Davis method, is proposed. This latter one makes possible to treat the direct and inverse kinematic in the same way, using virtual kinematic chains. By a specific way, the kinematic model allows simplifying the Jacobian matrix, since it is not restricted to the base frame. A transformation from Euler angles to Octonions avoids possible singularities. In addition, a new linear quadratic regulator control that uses the design of variables gains based on low-pass filter and norm. Global stability of the State-Dependent Riccati Equation is performed by using Lyapunov analysis with La'Salle's Principle. The allocation of faults in this strategy by using virtual fuzzy thrusters is addressed, which minimises the fault impact expressed as an abrupt discontinuity in the thruster system, as observed in the simulation results.

Automated Activity Identification for Construction Equipment Using Motion Data From Articulated Members

Real-time monitoring and assessment of construction resources have always been a challenge due to the unique, dynamic, and complex nature of each construction site and operation. The ability to automatically classify activities performed by various equipment in real time can aid in making timely tactical operational decisions that can lead to increased fleet productivity, reduced time and cost of operations, and minimized idle times. Such endeavors have traditionally been performed manually through human observation, making it extremely labor and time-intensive. Meanwhile, the development of low-cost micro-electro-mechanical systems (MEMS) with rapidly evolving computing, networking, and storage capabilities, along with the advances in computational techniques such as machine learning present new opportunities in the real-time activity identification domain. Even though previous studies have shown promising results for equipment activity identification at limited levels of detail, they have a fundamental limitation in their reliance on the equipment vibration. Equipment vibration is highly dependent on factors that are extrinsic to the performance of an activity itself such as ground conditions, age and condition of equipment, and operator skill. This aspect of current methods necessitates the collection of training data from the specific equipment of interest and requires manual labeling of training data, thereby limiting its application across different types of equipment and operating conditions. This paper investigates the use of activity-specific equipment motions instead of vibration for activity identification. This approach is the first step towards the larger goal of generating training data automatically from virtual kinematic models of equipment in the future. This paper also provides an array of sensitivity analyses in order to determine the most appropriate parameters for implementing machine learning algorithms for equipment activity identification. A case study was performed using an excavator working on an earthmoving site that demonstrated a significant improvement in equipment activity identification results by utilizing IMU data of different articulated elements over previous efforts. The results of this paper indicate that more accurate results for activity identification can be obtained by using articulated equipment motion over vibration, which paves the way for the automatic generation of labeled training data in the future.

Plastic Analysis of Masonry Arches Reinforced with FRCM under Vertical and Horizontal Forces

Aim of this paper is the evaluation of the increasing of the load-carrying capacity of masonry arches strengthened at intrados extrados with poliparafenilenbenzobisoxazole (PBO) fabric reinforced cementitious mortar composite. An analytical procedure is proposed, in the Limit Analysis context, considering two schemes of load: a vertical load applied at the crown of the arch and a horizontal distribution proportional to the weight. The presence of the composite material is introduced by considering a plastic behaviour of the hinges defining the virtual kinematic mechanism compatible with the Limit Analysis hypotheses. Two assumptions on these mechanisms are made: a correct position of the hinges inside the cross-section of the masonry arch or a simplified location at the intrados or at the extrados of the structure. Finally, a parametric survey is carried out in order to understand the influence of the involved parameters on the load-carrying capacity of the strengthened masonry arches.

Calculation of Program Control Not Generating Singularities in Gyrosystems

A new approach to calculating the program controls of the spacecraft (SC) attitude by single-gimbal control moment gyros (gyroscopes in English terminology or gyrodynes in Russian terminology) is described in details. The novelty of the proposed method of calculating program controls is the virtual kinematic configuration of the actuator gyrosystem and the use of the angular momentum of the SC as a state variable when describing its dynamics. The formulation of the problem of calculating the control laws, based on these innovations, made it possible to directly use the total angular momentum of all the rotors of the gyrosystem in their motion relative to the main body of the SC, rather than its derivative, as a working tool for controlling the SC, and to accept the laws of the precessions of the gyro units, rather than the velocities of these precessions. A new approach to solving the problem of reorientation enables us to obtain control laws without such special (singular) positions of the gyro units in which the execution of the calculated laws is interrupted. This feature solves the well-known singularity problem of an actuator gyrosystem consisting of gyrodynes, and suggests that the presence of a singularity problem in the process of executing the calculated laws should be due only to their calculation method rather than due to certain specific features of the gyrosystem itself. The new method of calculating the control presented in this paper uses the structure of the space trajectory given a priori and the law of the motion along this trajectory is calculated in the process of forming the control. All the calculations are carried out on the standard onboard digital computer.

Virtual reconstruction and kinematic simulation of a marble sawmill through the integration of historical and archeological data

One of the greatest difficulties researchers encounter when attempting to comprehensively recover the technological heritage of the past lies in the fact that many components (machines, tools, etc.) were fully or partially made with ephemeral materials (such as wood). For this reason, in this work, we use virtual reality tools based on 3D models and the kinematic simulation of mechanisms and machines in order to integrate information from archeological remains and information obtained from written records during research on the recovery of the technological heritage of the past. In order to demonstrate the adequacy and suitability of the proposed method, the buildings and machinery of the Fallen Mill at El Escorial (Spain) have been virtually reconstructed as a case study. This one consisted of two mills, one flour mill and one marble sawmill, and was built at the end of the sixteenth century but, following a long period of abandonment, only scarce physical remains exist today. The Fallen Mill was highly important to the construction of the Monastery of El Escorial as, on the one hand, it was the first flour mill at the Monastery and, on the other hand, the marble sawmill which made it possible to reduce the time expected for the construction of the high altarpiece in the Monastery’s Basilica by half. The virtual reconstruction enabled an integrated compression of the architecture and technique used for both mills, providing users and researchers with an interactive environment for analysis, the discussion of alternatives, and detailed knowledge of this valuable technological heritage. With this and following centuries of abandonment, the Fallen Mill can be recovered for European technological heritage and makes clear the archeological importance of the existing physical remains of both mills.

Computation of program controls performed nonstop by gyrodynes

A new method for calculating space vehicle (SV) attitude controls ensuring their effective implementation by a system of collinear pairs of single-gimbal forced unrestrained gyros (gyrodynes) has been proposed. The novelty of the method consists in a virtual kinematic configuration of the gyro system, i.e., the precession of gyro units in the collinear pairs of gyrodynes is coupled in a nonmechanical manner. In addition, the angular momentum of the system as a state variable for describing the dynamics of the SV permanent rotation was used for the first time at the stage of computing controls performed nonstop by gyrodynes. In the general formulation, when the desired final state of the SV is arbitrary, the SV attitude control problem can be reduced to a sequence of permanent rotations. The performance of the method is demonstrated as applied to the calculation of program gyrodyne controls with a permanent reduction in the SV angular velocity around its center of mass with a nonzero SV angular momentum after its discharge.

Topology design and kinematic optimization of cyclical 5-DoF parallel manipulator with proper constrained limb

This paper proposes topology design and kinematic optimization of cyclical 5-degree-of-freedom (DoF) parallel manipulator with proper constrained limb. Firstly, a type of cyclical 5-DoF parallel manipulators with proper constrained limb is proposed by analyzing DoF of the proper constrained limb within workspace. Exampled by a cyclical 5-DoF parallel manipulator with the topology 4-UPS&1-RPS, its motion mapping model is formulated. By taking the reciprocal product of a wrench on a twist as the generalized virtual power, the local and global kinematic performance indices are provided. Then, on the basis of the actuated and constrained singularity analysis of the 4-UPS&1-RPS parallel manipulator within the position and pose workspace, the topology design of the manipulator without singularity is carried out, and its reachable and prescribed workspaces are obtained. Finally, by maximizing the global kinematic performance index and subjecting to a set of appropriate constraint conditions, the kinematic optimal design of the 4-UPS&1-RPS parallel manipulator is carried out utilizing the genetic algorithm of MATLAB optimization toolbox.

Four-dimensional unsubtraction with massive particles

We extend the four-dimensional unsubtraction method, which is based on the loop-tree duality (LTD), to deal with processes involving heavy particles. The method allows to perform the summation over degenerate IR configurations directly at integrand level in such a way that NLO corrections can be implemented directly in four space-time dimensions. We define a general momentum mapping between the real and virtual kinematics that accounts properly for the quasi-collinear configurations, and leads to an smooth massless limit. We illustrate the method first with an scalar toy example, and then analyse the case of the decay of a scalar or vector boson into a pair of massive quarks. The results presented in this paper are suitable for the application of the method to any multipartonic process.

Whole Body Control of a Dual-Arm Mobile Robot Using a Virtual Kinematic Chain

Dual-arm manipulators have more advanced manipulation abilities compared to single-arm manipulators and manipulators mounted on a mobile base have additional mobility and a larger workspace. Combining these advantages, mobile dual-arm robots are expected to perform a variety of tasks in the future. Kinematically, the configuration of two arms that branches from the mobile base results in a serial-to-parallel kinematic structure. In order to respond to external disturbances, this serial-to-parallel kinematic structure makes inverse kinematic computations non-trivial, as the motion of the base has to take the needs of both arms into account. Instead of using the dual-arm kinematics directly, we propose to use a virtual kinematic chain (VKC) to specify the common motion of the two arms. We formulate a constraint-based programming solution which consists of two parts. In the first part, we use an extended serial kinematic chain including the mobile base and the VKC to formulate constraints that realize the desired orientation and translation expressed in the world frame. In the second part, we use the resolved VKC motion to constrain the common motion of the two arms. In order to explore the redundancy of the two arms in an optimization framework, we also provide a VKC-oriented manipulability measure as well as its closed-form gradient. We verify the proposed approach with simulations and experiments that are performed on a PR2 robot, which has two 7 degrees of freedom (DoF) arms and a 3 DoF mobile base.

X3D-based Virtual Prototype Robot Mechanism Simulation

This paper mainly studies the goal when using standard X3D robot virtual prototype technology research, design, and kinematics simulation of the body. In the study, the virtual prototype model should be able to satisfy the basic research and design of industrial robot kinematics. Validation X3D technology in the design of virtual prototype of robots can have good effective action. The design of industrial robot virtualization is positive. This work includes X3D technology based on the model, the robot kinematics mathematic model of virtual prototype, and the use of this robot kinematics model using the model analysis of the performance parameters of the robot virtual prototype. This paper solves X3D using the virtual prototype technology robot run to learn some key problems of the simulation of the virtual prototype of robot X3D expression methods (robot virtual body expression, organization, the assembly, and the constraint X3D research). Based on the virtual prototype, X3D is inverse kinematics calculation model.

Evaluation of a Mixed CAD Gear Modeling from Time and Precision Point of View

Abstract The aim of the paper is to present an evaluation of a new mixed CAD modeling method, capable to universally build surfaces and solid models of gears. The proposed CAD solution builds gear models, primary not for a visual simulation of the gearing processes, but for complex gearing- and FEA studies in virtual environment. Localization of the contact paths of gear pairs, virtual kinematic evaluations, rapid verification of newly developed gear types and FEA analysis requires satisfactorily precise surface and solid models. The known NURBS modeling methods are mainly based on the analytical equations of the flanks of the teeth surfaces. The bottom and tip surfaces of the teeth, are very important in meshing and FEA studies, and generally cannot be built from the meshing equations. As the new mixed modeling method proposes a simplified and quick CAD modeling procedure, with flexible modeling options like rapid tool profile modifications, an evaluation of the obtained models must be made, from both: generating time and precision point of view. For this purpose, a model of a spur cylindrical gear (generated by a convolute helical hob) is built using the Solid Boolean Subtraction method and is compared with the gear generating process using a new mixed CAD method.

A BP-GA Approach to Solve the Inverse Kinematics of Virtual Human's Upper Limb Kinematic Chain

The human’s Upper Limb Kinematic Chain (ULKC) is the most frequently used and most complicated kinematic chain. It is difficult to compute its Inverse Kinematic (IK) solution quickly and accurately by using neural network or Genetic Algorithm (GA) due to ULKC’s high degree of freedom. Combining BP neural network and GA, we proposed a method to solve its IK problem. Firstly, the joint-units of ULKC and its mathematical model were constructed based on D-H method. Then the BP neural network produced a local optimal solution, which could be served as an individual of GA’s initial population. We could determine the searching domain by its optimal solution. Finally, the high accuracy solution was obtained by using the adaptive GA. The experimental results showed that the proposed approach could obtain the high accuracy solution efficiently with the BP neural network high-speed and GA high-accuracy.