Serial Chain Research Articles

Optimal Curve Fitting for Serial Chain in Six-Crease Origami Unit

Abstract Origami-inspired structures have been widely used in aerospace and robotics for three-dimensional (3D) symmetrical configurations using crease-symmetrical origami basic patterns. These patterns offer advantages in repeatable and systematic modeling and mass production. However, few studies have focused on 3D non-symmetrical structures using symmetrical origami basic patterns due to their structure complexity, limiting their application. Therefore, we aim to analyze the folding behavior in 3D non-symmetrical structures using a 6-crease symmetry origami base pattern. To achieve this goal, we first focus on behavior in a two-dimensional (2D) plane. This paper presents a scheme for the behavior of origami units with an optimal curve-fitting algorithm. The curve can be any 2D space curve. The fitting curve, constructed by numerical analysis and an optimal approaching scheme, can satisfy error requirements and retain foldable origami unit features. The paper verifies the feasibility of the curve-fitting scheme by presenting two curve examples, including a quadratic curve and a sin wave function. The results show that the fitting error is reduced by 99% when no boundary conditions are applied. This research provides valuable insights into understanding origami unit kinematic optimization through forward and inverse kinematics. It offers potential applications in the engineering design of foldable structures and precision origami-inspired mechanism, thereby opening avenues for further exploration of complex origami structures and their applications in emerging technologies.

Type synthesis of 3-DOF spherical hybrid mechanisms with fixed centers of rotation

To improve the load-bearing capacity and the rotation range about the normal of the moving platform in a spherical parallel mechanism (SPM), a type synthesis method for spherical hybrid mechanisms (SHMs) with fixed centers of rotation is proposed by coupling a serial transmission chain with the central passive limb chain of the SPM near its center area. Based on the analysis of the spherical mechanism configuration’s research status with a fixed rotation center, a method for systematically synthesizing SHMs is given, and four types of limb chains are developed. The possible limb constraint systems provided by each type of limb chain are analyzed via screw theory, and the type synthesis of each type of limb chain is carried out. Screening rules are proposed to obtain the preferred limb chains from the limb chain configuration results. By selecting and permuting preferred limb chains based on the mechanism’s center position of rotation and the constraint type, a series of SHMs that rotate unrestricted about the normal of the moving platform are produced. Selecting the RBR-2RRR SHM as an example, its workspace, singularity, dexterity, and stiffness are analyzed to verify the effectiveness of the research. This work enriches the configuration types of SHMs and provides theoretical support for the design and applications of SHMs in engineering.

Supply chain cash-flow bullwhip effect: An analytical model for working capital variance propagation

This research article probes the cash-flow bullwhip effect (CFB), a phenomenon precipitating an increase in the fluctuations of working capital within supply chains. A novel analytical model is proposed to delve into the CFB within a multi-echelon, serial supply chain, taking factors into account, such as demand autocorrelation, procurement lead time, and payment lead times. Our study implies that extended procurement lead times contribute to a heightened CFB, and a substantial discrepancy between a firm’s payment lead time and that of its customers results in a more pronounced CFB. Importantly, adopting shorter payment lead times for customers and extending them for suppliers can inflate the cash-flow bullwhip for all three constituent entities: the echelon, its customers, and suppliers. Our quantitative analysis reveals that strategies, such as payment batching and divulging end-customer demand information can mitigate the cash-flow bullwhip by as much as 49.5 and 53.7%, respectively. Empirical inspection of the CFB experienced by a sample of 786 companies from 2010 to 2019 demonstrates that ∼65% of these companies intensify their working capital variance. This underscores the need for cautious management of working capital variance and the adoption of suitable inventory and payment strategies to forestall financial turmoil within the supply chain.

Investigating the Determinants of Construction Stakeholders’ Intention to Use Construction and Demolition Waste Recycling Products Based on the S-O-R Model in China

In China, the annual generation of construction and demolition waste (CDW) has been steadily increasing, accompanied by a generally low recycling rate. To promote sustainable development, there is an urgent need to enhance the recycling of CDW. This paper aims to investigate the determinants of construction stakeholders’ intention to use CDW recycling products in China. The stimulus–organism–response (S-O-R) model, integrating the technological–organizational–environmental (TOE) framework, personal perceptions, personal traits, and the intention to use, was chosen as our theoretical model. Through an analysis of 272 valid questionnaires, the partial least squares structural equation modeling (PLS-SEM) was utilized to evaluate the model and test the proposed hypotheses. The results indicated that personal traits are the most influential factor shaping construction stakeholders’ intention to use, followed by personal perceptions, while external stimuli exert no direct significant impact on the intention to use. Nevertheless, personal traits and personal perceptions play a significant mediating role in the relationship between external stimuli and the intention to use, forming a noteworthy serial chain mediation. The research findings imply that in China, bolstering personal traits plays a critical role in guiding and promoting the intention to use CDW recycling products.

KULEX-Wrist: Design and Analysis of Linkage-Driven Exoskeleton for Wrist Assistance

Abstract This paper presents a wrist exoskeleton called the KIST Upper-Limb EXoskeleton (KULEX)-wrist for activities of daily living assistance of the elderly and the disabled. A novel linkage-based structure of the rotational mechanism with three degrees-of-freedom is proposed. The proposed wrist mechanism is composed of two prismatic-universal-spherical serial chains and one revolute-revolute-revolute spherical chain. Besides, a combination of a planar slider-crank and spherical four-bar linkages was employed as a drive mechanism for power transmission. Kinematic analysis was conducted to understand its working principle. Then, the dimensions of all the linkages were synthesized to meet the structural design suitable for the wearable exoskeleton and the transmission quality. In addition, motion twists and wrenches were geometrically derived. Finally, a prototype of the KULEX-wrist was designed, and then its performance of mechanical stiffness, motion capability, and power assistance was verified.

Motion planning and control of planar serial chain articulating locomotion system

This paper addresses two important problems in motion planning and control of serial chain planar articulating locomotion systems moving on a flat surface. Locomotion systems generally use closed curve cyclic gaits to perform maneuvers in the environment. The geometric mechanics tools are used to identify the cyclic gaits. Firstly, a motion control approach is presented using a single cyclic gait parametrized with variable gait parameters. The parameterized gait is used to drive the system along a continuous trajectory with varying curvature. On the other hand, the proposed approach presents how the gait parameters can be controlled to smoothly track a continuous trajectory. Secondly, this paper presents a joint coordination approach to generalize the height function based approach to design cyclic gaits for the system having joint space with more than two degrees of freedom. Using joint coordination approach, cyclic gaits can be designed for different motion behaviors such as longitudinal motion, sideways motion and rotation in place. The joint coordination approach also helps generalizing the proposed motion control approach to planar serial chain articulating robots with any even number of joints.

Kinematic Analysis of 3-PRPPS Spatial Parallel Manipulator with Circularly Guided Base for Singularity-Free Robotic Motions

Robot manipulators are classified as serial manipulators and parallel manipulators. Parallel manipulators are classified into planar and spatial parallel manipulators (SPMs). The parallel manipulators have moved and fixed platforms connected with serial chains. The parallel manipulators have many linkages, which create a singularity problem. The singular positions of SPMs have also gained substantial attention in various industrial applications due to their intrinsic advantages in precision, flexibility, and load-bearing capabilities. The 3-PRPPS SPM has three prismatic joints, one spherical joint, and one revolute joint. This work changed the fixed base with a circular guided base to avoid singularity issues. The manipulator was modeled with direct kinematic relations. The Jacobian matrix for position and orientation was derived. The workspace was taken as the common area of the three circles, whose radius was the maximum arm length. The position and orientation of the end effector were traced. In the form of the end effector traces, no singularities in the mechanism were observed. The path of the robot manipulator was observed in all the possible positions and orientations. The multi-body simulation was also conducted on the 3-PRPPS manipulator, the main findings of which are presented in this article.

Identification of Deformable Linear Object Dynamics from Input-output Measurements in 3D Space

Controlling deformable linear objects requires reliable models that capture their complex and high-dimensional dynamics. This paper aims to obtain accurate state-space models of such objects from input-output measurements only, tailored for the use in a model predictive control setting. The proposed identification approach is initialized by a physics-inspired baseline model which approximates a deformable linear object by a serial chain of rigid bodies connected via elastic joints. The nonlinear residual dynamics of the baseline model are then modeled by an artificial neural network, where a key element is the so-called guided residual search that first infers the latent residual and state trajectories in the time domain, in this way facilitating supervised learning of the neural network. The efficacy of the modeling approach is demonstrated on experimental data of the 3D end-point motion of a flexible aluminum rod, excited by a 7-axis Franka Panda robot arm. Compared to a physics-inspired baseline model, the proposed method achieves a 14% prediction performance increase, and compared to a fully neural network-based approach with a similar number of parameters, it achieves a 58% improvement, while also reporting a training time that is more than 5 times faster.

A new virtual functional element method for deviation prediction of assembled structures with parallel connection chain

The assembly precision prediction of industrial products with numerous tolerance information and complex assembly relations is a challenge for existing deviation analysis methods since their dimensional chains usually form parallel connections. The parallel connection chain is often transformed into a serial connection chain by discarding some tolerance information and physical constraints in practical application, which leads to amplifying the range of predicted results and reducing the predicted accuracy. In this paper, a virtual functional element method is proposed to simplify the parallel connection chain by integrating the tolerance information into the torsor parameters of specified virtual functional elements. A general Jacobian-Torsor model is developed to solve the simplified parallel connection chain, in which the Boolean intersection operation on torsor parameters is used to obtain comprehensive deviation results for multiple branches in a parallel connection chain. Meanwhile, the locking effect and leverage activation effect are proposed to characterize the effect of the invariant degree in parallel connection chain. Finally, an assembly case of a power plant is applied to validate the proposed method, and the results show that it has a high potential to improve the prediction accuracy of assembly deviation compared to three conventional methods.

Hypercomplex Quaternions and Higher-Order Analysis of Spatial Kinematic Chains

Abstract This paper introduces a novel computational method for analyzing the higher-order acceleration field of spatial kinematics chains. The method is based on vector and quaternionic calculus, as well as dual and multidual algebra. A closed-form coordinate-free solution generated by the morphism between the Lie group of rigid body displacements and the unit multidual quaternions is presented. Presented solution is used for higher-order kinematics investigation of lower-pair serial chains. Additionally, a general method for studying the vector field of arbitrary higher-order accelerations is discribed. The method utilizes the “automatic differentiation” feature of multidual and hyper-multidual functions to obtain the higher-order derivative of a rigid body pose without need in further differentiation of the body pose regarding time. Also is proved that all information regarding the properties of the distribution of higher-order accelerations is contained in the specified unit hyper-multidual quaternion.

Noncollocated Proprioceptive Sensing for Lightweight Flexible Robotic Manipulators

This article presents the design of a noncollocated feedback system for flexible serial manipulators. The device is a passive serial chain of encoders and lightweight links, mounted in parallel with the manipulator. This measuring arm effectively decouples the manipulator's proprioception from its actuators by providing information on the actual end effector pose, accounting for both joint and link flexibility. The kinematic redundancy of the measuring chain allows for safe operation in the context of human–robot interaction. A simple yet effective error model is introduced to assess the suitability of the proposed sensor system in the context of robotic control. The practicality of the device is first demonstrated by building a physical joint-encoder assembly and a simplified planar measuring arm prototype. With this additional feedback, a task-space position controller is devised and tested in simulation. Finally, the simulation results are validated with an experimental 3-DoF lightweight manipulator prototype equipped with a five-joint measuring arm.

The effect of model complexity on the human center of mass estimation using the statically equivalent serial chain technique

Estimating the human center of mass (CoM) has long been recognized as a highly complex process. A relatively recent and noteworthy technique for CoM estimation that has gained popularity is the statically equivalent serial chain (SESC). This technique employs a remodeling of the human skeleton as a serial chain where the end effector represents the CoM location. In this study, we aimed to evaluate the impact of model complexity on the estimation capability of the SESC technique. To achieve this, we designed and rigorously assessed four distinct models with varying complexities against the static center of pressure (CoP) as reference, by quantifying both the root-mean-square (RMS) and correlation metrics. In addition, the Bland–Altman analysis was utilized to quantify the agreement between the estimations and reference values. The findings revealed that increasing the model complexity significantly improved CoM estimation quality up to a specific threshold. The maximum observed RMS difference among the models reached 9.85 mm. However, the application and task context should be considered, as less complex models still provided satisfactory estimation performance. In conclusion, the evaluation of model complexity demonstrated its impact on CoM estimation using the SESC technique, providing insights into the trade-off between accuracy and complexity in practical applications.

An Integrated Kinematic Mapping and Fourier Method to Design Spherical Coupled Serial Chain Mechanisms for Single-Joint Rehabilitation

Abstract Robotic devices are capable of reducing the physical burden on rehabilitation therapists and providing training programs of good repeatability, high efficiency, and high precision. When designing the kinematic structure for rehabilitation robots, there has been a growing interest toward one-degree-of-freedom (DOF) end-effector mechanisms due to their simpler structure and less complicated control algorithms. Compared with current one-DOF mechanism designs that are mainly customized for multi-joint robotic training, spherical coupled serial chain (SCSC) mechanisms are proposed in this paper to specifically deliver the single-joint robotic training, which is of equal importance to the effective physical recovery. Using kinematic mapping theory, the end-effector motion of SCSC mechanisms can be naturally transformed to two trigonometric curves composed of finite Fourier series in two separate planes of the image space. This novel formulation helps to establish an analytical and direct relationship between the design parameters of the SCSC mechanism and the harmonic parameters of the image-space representation of the task rehabilitation motion. The result is a simple and effective method for kinematic synthesis of SCSC mechanisms for generation of single-joint motion with an arbitrary number of spherical poses. An example of designing SCSC mechanisms for shoulder-joint rehabilitation is presented at the end of this paper to illustrate the feasibility of the proposed method.

Dynamic range enhancement for the sensing signals of peak-saturated fiber Bragg grating spectra.

Fiber Bragg grating (FBG) sensors applying time-delay interrogators with wavelength swept lasers (WSLs) are popular for their great potentials in high sensing resolution and power budget. In these systems, well-calibrated WSLs with reduced wavelength nonlinearity and jitter are critical for the sensing performance. However, high-performance WSLs are expensive and could significantly increase the cost of the systems. The overall cost may be reduced by maximally sharing each WSL with multiple sensing FBGs through mechanisms like power splitting, which distribute the WSL signal into multiple independently operated serial FBG chains. Under such scenarios, the sensing processing unit (SPU) of each serial FBG chain must be synchronized with the WSL for correctly estimating the FBGs' respective spectra from the signal return time delays. We previously propose a self-synchronized scheme relying on the dual-polarity spectrum signal, which reduces the synchronization labor. The dual-polarity signal has a wider dynamic range, which may limit the system response speed or accuracy, considering the amplifiers' responses or the analog-to-digital converters' (ADCs') quantization noise. In this Letter, we apply peak-saturated FBG spectra for the sensors to increase the receivers' equivalent dynamic range. The flattop waveforms of the saturated peaks result in uncertainty for the peak positions. An artificial neutral network (ANN)-based method is further studied to enhance the peak detection accuracy. We show an ∼88% receiver dynamic range improvement with an inaccuracy reduction of about a half compared to the filter-and-maximum-readout (FMR) method.

Kinematics and optimization of a novel 4-DOF two-limb gripper mechanism

AbstractThis study presents a novel 4-DOF two-limb gripper mechanism with a simple design that offers high adaptability for different objects. The mechanism integrates a three-finger end effector and employs a 2-DOF driving system in both serial kinematic chains mounted on the base, addressing performance problems caused by moving actuators. First, the architecture of the gripper mechanism is described, and its mobility is verified. Next, the inverse and forward kinematic problems are solved, and the Jacobian matrix is derived to analyze the singularity conditions. The inverse and forward singularity surfaces are plotted. The workspace is investigated using a search method, and two indices, manipulability and dexterity, are studied. The proposed manipulator’s parameters are optimized for improved dexterity. The novel gripper mechanism has high potential for grasping different types of parts within a large workspace, making it a valuable addition to the field of robotics.

Origami-Inspired Wearable Robot for Trunk Support

We present a wearable “exo-shell” device inspired by the human spine for improving the gait of elderly people during obstacle avoidance tasks. This device—designed and fabricated with origami-inspired techniques—features a serial chain of lockable joints that can be stiffened using a braking system inspired by laminar jamming concepts. Current related work has identified that the trunk plays a crucial role in obstacle avoidance tasks. In this article, we thus propose an affordable wearable system that can be quickly fabricated and whose design can be adjusted to fit the individual wearer. The design leverages switchable, passive systems, in combination with lightweight materials that remain as “transparent” to the user as possible when inactive. This article focuses on translating human requirements into a tangible design that addresses the current state of our biomechanics knowledge. We describe the kinematics and forces of our proposed device, describe the performance of our system in a locked and unlocked state, discuss the integration of various sensors into our device, and characterize the performance of the device when locked and unlocked.

Kinematic geometry of spatial RSSR mechanisms

Two different novel methods to derive the input–output (IO) equation of arbitrary RSSR linkages are described. Both methods share some common elements, i.e., they use the standard Denavit–Hartenberg notation to first describe the linkage as an open kinematic chain, and Study’s kinematic mapping to describe the displacement of the coordinate frame attached to the end-effector of the chain with respect to the relatively non-moving base frame. The kinematic closure equation is obtained in the seven-dimensional projective kinematic mapping image space by equating the eight Study soma coordinates to the identity array. Then two methods are successfully applied to eliminate the intermediate joint angle parameters leading to the degree four biquadratic implicit algebraic IO equation: (a) the linear implicitisation algorithm, which can be applied after rearranging the closure equation such that the linkage can be viewed as two serial RS chains, and (b) numerical elimination theory using pseudowitness sets. Both approaches lead to the same IO equation. The utility of this algebraic form of the IO equation is illustrated with three detailed application examples.

System tests of the ATLAS ITk planar and 3D pixel modules

In order to validate the design of the new all-silicon Inner Tracker (ITk) for ATLAS for the HL-LHC, a series of system tests has been performed, to assess the performance of prototype planar and 3D pixel modules arranged into serial power chains mounted onto realistic mechanical structures. In this paper, the prototype loaded local supports and test infrastructure is described and the key results presented.

Type synthesis of serial kinematic chains with screw type terminal constraints based on an adding joint method

Serial kinematic chains(SKCs) with screw type terminal constraints are ubiquitous. However, the type synthesis of such mechanisms has not been systematically studied. Unlike the SKCs which only have pure constraint forces and torques, these kinds of SKCs contain independent screw type terminal constraints with non-zero pitch. This paper develops a systematic work for the type synthesis of general SKCs with terminal screw type constraints. In this paper, combined with the screw theory and the atlas method, the principle and steps for synthesizing SKCs based on an adding joint method are proposed. To derive feasible SKCs with terminal screw type constraints, the concept of constraint-kinematic identification graph(CKIG) is proposed and used to identify the screw type constraints in SKCs. Based on the proposed approach, varied 4R, 3R1P and 2R2P SKCs with 1F1H and 1C1H type terminal constraints and numerous 5R, 4R1P and 3R2P SKCs with 1H type terminal constraint are obtained. In addition, some examples for constructing novel parallel mechanisms(PMs) using the derived SKC with screw type terminal constraints are given. This paper provides an effective method for the type synthesis of SKCs with screw type terminal constraints.

ОБОСНОВАНИЕ ТЕХНИЧЕСКИХ ТРЕБОВАНИЙ К РОБОТОТЕХНИЧЕСКОМУ КОМПЛЕКСУ МНОГОРЕЖИМНОГО ПОЖАРОТУШЕНИЯ

The purpose of the study is to substantiate the technical requirements for a robotic complexdesigned to eliminate man-made emergencies associated with the need to eliminate fires. Theseemergencies can occur, first of all, in radiation and chemical accidents, as well as in accidents atfire and explosion hazardous facilities. The elimination of such emergencies, as a rule, is associatedwith an increased risk for firefighters and rescuers and requires the use of heavy equipment.The article proposes a campaign that involves considering two possible options for using the complex:when extinguishing a fire over an area in the modes of a single cycle with a transportablesupply of water and when extinguishing fires in a long-term fire extinguishing mode. At the sametime, it is proposed to consider the areal fire extinguishing rate and water consumption as the main indicators for assessing the effectiveness of the complex. Under the areal rate of fire extinguishing,it is proposed to understand as the ratio of the fire extinguishing area to the time. Waterconsumption during fire extinguishing is a single value for all links in a serial chain, in the form ofwhich a scheme for supplying water to a fire source can be represented. For the first option, theamount of water flow is sequentially calculated, which depends on the pressure that is created infront of the water shaft. This indicator primarily depends on such factors as the water pressuregenerated by the pump, the pressure loss in the hose line, the excess or decrease of the water barrelin relation to the pump. According to the results of calculations for each link, the obtainedindicators are summarized. For the second option, the capabilities of the robotic complex for longtermfire extinguishing involve the use of an existing reservoir of natural or artificial origin as asource of fire extinguishing agent. At the same time, the number of factors affecting the areal rateof fire extinguishing and water consumption increases significantly. To simplify the calculations, anomogram has been developed that allows you to calculate not only the above indicators, but alsodetermine the predicted values of the time required to extinguish the fire. The data obtained as aresult of the above calculations make it possible to finally realize the main task of the studies underconsideration, that is assessment of the capabilities of a promising complex of a robotic complexfor extinguishing fires at radiation-, chemical- and explosive objects. This problem is proposedto be solved by forming the technical forms of the RTK, which can be created to solve firesat the above objects, and then by a comparative assessment of their qualities.