Closed-loop Chain Research Articles

Analysis of ride comfort of a continuous tracked bogie system with variable configuration

In this study, the effect of change in height of a so-called variable configuration of a continuous tracked bogie system on ride comfort performance is investigated. To this end, constraint equations among different vehicle parts are derived recursively, and equations of motion are formulated according to the Newton–Euler equations using the embedding technique. Besides, to model the track as a closed-loop chain, the penalty method has been used instead of loop-closure equations. To mathematically model the contact between tracks, wheels, and the terrain, the continuous contact force model has been employed. To validate the mathematical model, the vehicle dynamic behavior is simulated by the Runge–Kutta method in MATLAB software and compared with those obtained from the identical model, built in RecurDyn software, and the results show good agreement. Moreover, the vibrational behavior of the tracked vehicle is investigated using two different vehicle configurations. This reveals that an increase in vehicle height does not change the vehicle vibrational frequencies. However, it increases the vehicle vibration amplitude and the energy absorbed by the vehicle components and decreases the ride comfort.

Accuracy analysis and synthesis of asymmetric parallel mechanism based on Sobol-QMC

Aiming at the aircraft composite skin grinding, a new three degree-of-freedom (DOF) parallel mechanism with asymmetrical structure (TAM) is proposed to replace manual grinding. The TAM is achieved by integrating one of active limbs into the passive limb while keeping the required DOF unchanged, which is divided into two closed-loop chains: telescopic rod and parallelogram. The inverse kinematics models of the two chains are established according to closed-loop vector method. Thus, the actuation and the constraint Jacobian matrix are obtained. Based on the perturbation principle, the error modeling of the TAM is built. Adopting the constraint Jacobian matrix, 15 uncompensated errors are distinguished from the error model. In order to improve the working accuracy of the TAM, accuracy analysis and synthesis are necessary for all the uncompensated errors. The mapping function reflects the influence of uncompensated errors on the pose accuracy. The global sensitivity evaluation indexes are established by mapping function. Since Sobol sequences are superior in uniformity and convergence, the Quasi-Monte Carlo method based on Sobol sequences (Sobol-QMC) is introduced for sensitivity analysis. Taking the minimum manufacturing and installation costs as the optimization target, the objective function of accuracy synthesis is constructed. Ultimately, the reasonable tolerance zone of each uncompensated error is calculated by genetic algorithm. Simulation is performed by Sobol-QMC to verify the rationality of the optimization. The results show the probability is above 97% where most pose errors are in [[Formula: see text], [Formula: see text]] within the workspace. Therefore, accuracy synthesis is correct and practical.

Fire Suppression and Thermal Behavior of Biobased Rigid Polyurethane Foam Filled with Biomass Incineration Waste Ash.

Currently, there is great demand to implement circular economy principles and motivate producers of building materials to integrate into a closed loop supply chain system and improve sustainability of their end-product. Therefore, it is of great interest to replace conventional raw materials with inorganic or organic waste-based and filler-type additives to promote sustainability and the close loop chain. This article investigates the possibility of bottom waste incineration ash (WA) particles to be used as a flame retardant replacement to increase fire safety and thermal stability under higher temperatures. From 10 wt.% to 50 wt.% WA particles do not significantly deteriorate performance characteristics, such as compressive strength, thermal conductivity, and water absorption after 28 days of immersion, and at 32 °C WA particles improve the thermal stability of resultant PU foams. Furthermore, 50 wt.% WA particles reduce average heat release by 69% and CO2 and CO yields during fire by 76% and 77%, respectively. Unfortunately, WA particles do not act as a smoke suppressant and do not reduce smoke release rate.

“Five Targets” management strategy of formulating international standards for energy enterprises

There are many problems in energy enterprises, such as insufficient understanding of internationalization, serious shortage of international talents, unthorough investigation of the rules of international standards organization, and inadequate transformation of existing achievements into standards, which seriously restrict the development of international standardization. The article relies on the research on management strategy of the State Grid Shanghai Electricity Research Institute, and proposes a “Five Targets” international standardized formulation system, which develops the closed-loop value chain of platform operation, professional focus, processed management, refined control, and industrialization development. The chain drives the implementation of the world’s leading strategy of energy enterprises, builds an international technology standard ecosystem, enhances the international influence and global competitiveness of energy enterprises, and opens up new areas and new prospects for building a world’s leading urban energy internet enterprise with Chinese characteristics.

A Parallel Manipulator with Planar Configurable Platform and Three End-Effectors

This work reports on the kinematic analysis of a planar parallel manipulator endowed with a configurable platform assembled with six terminal links serially connected by means of revolute joints. This topology allows the robot manipulator to dispose of three relative degrees of freedom owing to the mobility of an internal closed-loop chain. Therefore, the proposed robot manipulator can admit three end-effectors. The forward displacement analysis of the configurable planar parallel manipulator is easily achieved based on unknown coordinates denoting the pose of each terminal link. Thereafter, the analysis leads to twelve quadratic equations which are numerically solved by means of the Newton homotopy method. Furthermore, a closed-form solution is available for the inverse position analysis. On the contrary, the instantaneous kinematics of the robot manipulator is investigated by means of the theory of screws. Numerical examples are included with the purpose to illustrate the method of kinematic analysis.

Modeling and prototyping of a soft closed-chain modular gripper

PurposeThis paper aims to present a soft closed-chain modular gripper for robotic pick-and-place applications. The proposed biomimetic gripper design is inspired by the Fin Ray effect, derived from fish fins physiology. It is composed of three axisymmetric fingers, actuated with a single actuator. Each finger has a modular under-actuated closed-chain structure. The finger structure is compliant in contact normal direction, with stiff crossbeams reorienting to help the finger structure conform around objects.Design/methodology/approachStarting with the design and development of the proposed gripper, a consequent mathematical representation consisting of closed-chain forward and inverse kinematics is detailed. The proposed mathematical framework is validated through the finite element modeling simulations. Additionally, a set of experiments was conducted to compare the simulated and prototype finger trajectories, as well as to assess qualitative grasping ability.FindingsKey Findings are the presented mathematical model for closed-loop chain mechanisms, as well as design and optimization guidelines to develop controlled closed-chain grippers.Research limitations/implicationsThe proposed methodology and mathematical model could be taken as a fundamental modular base block to explore similar distributed degrees of freedom (DOF) closed-chain manipulators and grippers. The enhanced kinematic model contributes to optimized dynamics and control of soft closed-chain grasping mechanisms.Practical implicationsThe approach is aimed to improve the development of soft grippers that are required to grasp complex objects found in human–robot cooperation and collaborative robot (cobot) applications.Originality/valueThe proposed closed-chain mathematical framework is based on distributed DOFs instead of the conventional lumped joint approach. This is to better optimize and understand the kinematics of soft robotic mechanisms.

Design of a class of generalized parallel mechanisms with large rotational angles and integrated end-effectors

The generalized parallel mechanisms (GPMs) become a new feasible research topic to explore the advantages and overcome the shortcomings of the traditional parallel mechanisms (TPMs). This paper aims to address the challenge of the synthesis method for the GPMs with large rotational angles and integrated end-effectors (or configurable platforms). A sufficient condition for the independent rotations is presented and a design framework for constructing independent rotational degree of freedom (DOF) is developed. Using the set mapping and the Lie group theory, a method for synthesizing GPMs with hybrid structures is proposed on the basis of the obtained sufficient condition and the design framework. This method provides a way to connect the symmetric 0-DOF closed-loop kinematic chains with the parallel limbs to preserve the motions of both the parallel limbs and the elements in the closed-loop chains. A 3T3R GPM with 3-dimension large rotational angles and a class of 4-DOF and 6-DOF GPMs with 1-DOF integrated end-effectors are synthesized using the proposed method. The orientation workspace of the example GPMs are analyzed and discussed to reveal the high rotational capability. The obtained GPMs are suitable for the occasions that require high rotational performance, assembly, pick-and-place, drilling and other industrial applications.

A System Dynamics Model to Evaluate Effects of Retailer-Led Recycling Based on Dual Chains Competition: A Case of e-Waste in China

China, as the largest electronic waste producer in the world, is facing a critical challenge to manage its negative impacts on the environment. Hence, e-waste management is crucial for sustainable Chinese economic development. In this paper, a system dynamics model is adopted to identify the effects of retailer-led recycling based on closed-loop dual chains competition. The influence of contracts made by manufacturers on different retail modes is also discussed. From the aspects of total revenue (TR), market share (MS) and market competitiveness (MC), this paper analyzes the impact of e-waste recycling coefficient (ERC) on supply chain and analyzes the equilibrium solution of total supply chain return. The research results show that the contract incentive mechanism can improve the retailer’s recycling enthusiasm, and the effect on the retail mode of executive shop is more obvious. When the ERC is adjusted to 44.3%, the TR of supply chain is optimal, and the MS and MC occupy an obvious advantage.

Robust design of a closed-loop supply chain under uncertainty conditions integrating financial criteria

This paper proposes the formulation of a Mixed Integer Non-Linear Programming (MINLP) model that integrates financial risks measures in the robust design of a closed-loop supply chain, considering demand uncertainty of final products. In light of the advances in the reprocessing of goods to improve financial performance, the analysis of a closed-loop supply chain becomes crucial for the competitiveness of companies. We propose a multi-period model to solve the supply chain design problem in which several items must be produced through different levels after the production process, considering the flow of reverse of some products, which can be reprocessed or discarded. In this paper, we studied the design of a supply chain that includes several plants, distribution centers, collection centers, demand zones, and products; it consists of both products forward and reverses in the supply chain. Indeed, the perturbation parameters, robustness requirements, and the performance characteristics were identified qualitatively and quantitatively by determining their impact on the formulation and methodology. A variety of configurations are produced in the closed-loop supply chain, considering the variations of the uncertainty of the demand as a perturbation parameter. The objective is to maximize the economic value-added (EVA™); therefore, the most robust configuration is identified through robustness- EVA™ characterization and used to design the closed-loop chain. Finally, we present a numerical example using real information of the electronics industry in Bogotá to test the applied methodology and show that it is suitable for this type of problems.

Scapular kinematic reconstruction – segmental optimization, multibody optimization with open-loop or closed-loop chains: which one should be preferred?

Several numerical approaches have been developed to address the soft tissue artefact, such as the segmental optimization and multibody kinematics optimizations using either open-loop or closed-loop chains. However, it is still not clear which method is the most efficient for scapular kinematics reconstruction. In this study, six kinematic models were compared to a silver standard, i.e. a scapula palpator, during a series of 55 postures with maximal amplitudes of both the arm and scapula performed by 15 subjects. The most accurate approaches were the multibody optimization with a closed-loop chain and the segmental optimization. They provided averaged scapula misorientations of 14.9 ± 6.7° and 16 ± 7.1, respectively. Regarding the closed-loop chain integrating a point-to-ellipsoid scapulothoracic joint, the ellipsoid providing the most accurate results was a thorax-size ellipsoid fitting the area browsed by the scapula. Eventually, considering the high implementation costs of a multibody kinematics optimization, the segmental optimization could be considered as appropriate for scapular kinematics reconstruction.

A Lagrange-based generalised formulation for the equations of motion of simple walking models

Simple 2D models of walking often approximate the human body to multi-link dynamic systems, where body segments are represented by rigid links connected by frictionless hinge joints. Performing forward dynamics on the equations of motion (EOM) of these systems can be used to simulate their movement. However, deriving these equations can be time consuming. Using Lagrangian mechanics, a generalised formulation for the EOM of n-link open-loop chains is derived. This can be used for single support walking models. This has an advantage over Newton–Euler mechanics in that it is independent of coordinate system and prior knowledge of the ground reaction force (GRF) is not required. Alternative strategies, such as optimisation algorithms, can be used to estimate joint activation and simulate motion. The application of Lagrange multipliers, to enforce motion constraints, is used to adapt this general formulation for application to closed-loop chains. This can be used for double support walking models. Finally, inverse dynamics are used to calculate the GRF for these general n-link chains. The necessary constraint forces to maintain a closed-loop chain, calculated from the Lagrange multipliers, are one solution to the indeterminate problem of GRF distribution in double support models. An example of this method’s application is given, whereby an optimiser estimates the joint moments by tracking kinematic data.

System Dynamics Modelling of Remanufacturing and Recycling Mode Based on Closed-Loop Across-Chain Competition

To face the reality of resources exhaustion, the significance of recycling and remanufacturing in the closed-loop chain has become quite evident. This paper constructs a competitive recycling and remanufacturing model of the closed-loop supply chain through a case study of Midea Corp. and Gree Corp. and explores the impact of two recycling modes on total revenue of the supply chain and market share. The simulation results show that the total revenue of the supply chain will benefit from the increasing coverage points by the third party and the increasing environmental awareness of certain regions. The retailers show more enthusiasm of recycling through certain amendment of the contract between manufacturers and retailers. The time of payment could be shortened in closed loop. Moreover, the improvement of recycling mechanism of the retailers can enlarge the share of supply chain market. Guiding role of the proposed model and the simulation results played in establishing a better supply chain mode is presented.

A Systematic Approach for the Jacobian Analysis of Parallel Manipulators with Two End-Effectors

Parallel manipulators with two end-effectors (PM2Es) enable the design of gripping robots with high dynamic performance. The gripping action is enabled by internal, relative degrees of freedom (DoFs) between the two end-effectors. Many standard methods for the analysis and control of parallel manipulators rely on a Jacobian, where a complete Jacobian analysis includes constraint relations. These constraint relations have not been consistently included in previous analyses of PM2Es, while they are specifically relevant for PM2Es because constraints play an important role in the static force analysis of a PM2E. This is because wrenches applied by the actuators can be transferred to the end-effectors through internal constraints, an effect which is not captured by kinematic relations alone. This paper presents a systematic approach to perform the Jacobian analysis of PM2Es, which is based on screw theory, and that takes all constraint relations into account. The approach is applied to a PM2E with three legs and one internal closed-loop chain. An example mechanism was built to experimentally validate the resulting Jacobian analysis using a static force analysis.

Development of a calibrating algorithm for Delta Robot’s visual positioning based on artificial neural network

Delta robot with vision system can automatically control the end-actuator to accurately grasp moving objects on the conveyor belt. Establishment of the mapping relationship between the image feature space and the robot working space form a closed-loop chain for transformational link between the robot coordinate, camera coordinate and conveyor belt coordinate. The vision system calibration is a basic problem of robot vision research and implementation. The artificial neural networks (ANN) which has learning ability, adaptive ability and nonlinear function approximation ability can establish the nonlinear relationship between space points and pixel points to complete accurate calibration of the vision system. The convergence speed of calibration algorithm affects the real-time visual servo system. The calibration precision, generalization ability and calibration space of algorithm influence the robot grasping accuracy. Therefore, a new calibration technique for delta robot’s vision system was presented in this paper. The algorithm combines ANN with Faugeras vision system calibration technology. The setting of the initial value, network structure and the choice of the activation function is based on the model of Faugeras vision system calibration algorithm, which makes the actual output of the network closer to the target output. Experiments proved that this algorithm has higher calibration accuracy and generalization ability compared with the conventional calibration algorithm, as well as faster convergence speed compared with the conventional artificial neural network structure in the case of high calibration accuracy.

PROBABILISTIC BEHAVIOR OF JOINT FORCES IN MECHANISMS

This paper discusses the influence of the clearance in joints on the joint reaction forces in mechanisms. By using mathematical programing, the optimal parameters of kinematic chains can be efficiently obtained by using the deterministic approach. However, the situation becomes more sophisticated if random effects of tolerances of the arm lengths and the random pin positions have to be considered. In this work the influence of clearances on joint forces is calculated by using the Taylor approximation and the Monte Carlo method. Using the two methods was necessary, because the Taylor approximation usually yields satisfying results only for small values of clearances and for this reason it makes sense to compute the required quantities also by another independent method. The implementation of the model is illustrated with two examples. The first example considers a closed loop chain, representing a four-bar mechanism being an actual part of a hydraulic support, employed in mining industry. The hydraulic support must fulfill some requirements so it’s very important to have influence of clearances on joint forces in control. The second example considers joint reaction forces of car wiper mechanism. It will be shown, that the clearance in joints have some influence on the joint reaction forces.

電力供給型無段変速機構と測定システムの開発

As a newly type of CVT, we propose a linkage type CVT for transmission used in power generation system with high efficiency. The proposed CVT is composed of closed loop chains and non-invertible components. As for wind power generation using natural energy, when the wind is strong, the rotational speed in the input axis is increased, the rotational speed exceeds the rotational speed at the output axis through non-invertible component, then the CVT does not transmit any powers. Contrariwise, when the wind is weak, the CVT can transmit the power by non-friction transmission with high efficiently.

Extension of D-H parameter method to hybrid manipulators used in robot-assisted surgery.

The main focus of this work is to extend the applicability of D-H parameter method to develop a kinematic model of a hybrid manipulator. A hybrid manipulator is a combination of open- and closed-loop chains and contains planar and spatial links. It has been found in the literature that D-H parameter method leads to ambiguities, when dealing with closed-loop chains. In this work, it has been observed that the D-H parameter method, when applied to a hybrid manipulator, results in an orientational inconsistency, because of which the method cannot be used to develop the kinematic model. In this article, the concept of dummy frames is proposed to resolve the orientational inconsistency and to develop the kinematic model of a hybrid manipulator. Moreover, the prototype of 7-degree-of-freedom hybrid manipulator, known as a surgeon-side manipulator to assist the surgeon during a medical surgery, is also developed to validate the kinematic model derived in this work.

Parallel robots with configurable platforms: Fundamental aspects of a new class of robotic architectures

This paper introduces general and fundamental aspects of a new class of parallel robots termed “parallel robots with configurable platforms”. The concept behind parallel mechanisms with configurable platforms is that the rigid link (non-configurable) end-effector is replaced by an additional closed-loop chain (the configurable platform). Some of the links of this closed loop are attached to the limbs so both the position and the configuration of the platform can be fully controlled from the motors located on the base. They retain the advantages of classical parallel robots, i.e. that all the motors are grounded on the base, while offering mechanical grasping capabilities via multiple contact points. Despite the few studies that have been done yet on the subject, the possible range of applications for this type of architecture is promising since it would be suitable for any application requiring both controlled grasping capabilities and high dynamic performance. This paper provides some preliminary results regarding the topology, mobility, overconstraints, Jacobian matrix, singularities and type synthesis of parallel robots with configurable platforms.

Type synthesis of spatial 3-DoF parallel mechanisms with planar sub-chains using revised digital topological graphs and arrays

SUMMARYType synthesis of spatial 3-DoF (degree of freedom) parallel mechanisms (PMs) with planar sub-chains is studied using the revised digital topology graph (r-DTGs) and arrays. First, many DTGs for type synthesis of spatial 3-DoF PMs are derived from their contracted graphs (CGs). Second, a complicated derivation of the DTG and an identification of an isomorphic DTG are transformed into a simple derivation of an array and an identification of an isomorphic array using a compiled program. Third, one or more spatial closed-loop chains in the derived DTGs are changed into the planar closed-loop chains by modifying digits marked in closed-loop chains, and the DTGs are transformed into the r-DTGs for the type synthesis of the spatial 3-DoF PMs with planar sub-chains. Finally, the 52 novel spatial 3-DoF PMs with the planar sub-chains are synthesized and verified by simulation mechanisms.

Ideal Compliant Joints and Integration of Computer Aided Design and Analysis

This paper discusses fundamental issues related to the integration of computer aided design and analysis (I-CAD-A) by introducing a new class of ideal compliant joints that account for the distributed inertia and elasticity. The absolute nodal coordinate formulation (ANCF) degrees of freedom are used in order to capture modes of deformation that cannot be captured using existing formulations. The ideal compliant joints developed can be formulated, for the most part, using linear algebraic equations, allowing for the elimination of the dependent variables at a preprocessing stage, thereby significantly reducing the problem dimension and array storage needed. Furthermore, the constraint equations are automatically satisfied at the position, velocity, and acceleration levels. When using the proposed approach to model large scale chain systems, differences in computational efficiency between the augmented formulation and the recursive methods are eliminated, and the central processing unit (CPU) times resulting from the use of the two formulations become similar regardless of the complexity of the system. The elimination of the joint constraint equations and the associated dependent variables also contribute to the solution of a fundamental singularity problem encountered in the analysis of closed loop chains and mechanisms by eliminating the need to repeatedly change the chain or mechanism independent coordinates. It is shown that the concept of the knot multiplicity used in computational geometry methods, such as B-spline and NURBS (nonuniform rational B-spline), to control the degree of continuity at the breakpoints is not suited for the formulation of many ideal compliant joints. As explained in this paper, this issue is closely related to the inability of B-spline and NURBS to model structural discontinuities. Another contribution of this paper is demonstrating that large deformation ANCF finite elements can be effective, in some multibody systems (MBS) applications, in solving small deformation problems. This is demonstrated using a heavily constrained tracked vehicle with flexible-link chains. Without using the proposed approach, modeling such a complex system with flexible links can be very challenging. The analysis presented in this paper also demonstrates that adding significant model details does not necessarily imply increasing the complexity of the MBS algorithm.