Kinematic Chain Research Articles

Modelling and identification methods for simulation of cable-suspended dual-arm robotic systems

This paper proposes rigid-body modelling and identification procedures for long-reach dual-arm manipulators in a cable-suspended pendulum configuration. The proposed model relies on a virtually constrained open kinematic chain and lends itself to be simulated through the most commonly used robotic simulators without explicitly account for the cables constraints and flexibility. Moreover, a dynamic parameters identification procedure is devised to improve the simulation model fidelity and reduce the sim-to-real gap for controllers deployment. We show the capability of our model to handle different cable configurations and suspension mechanisms by customising it for two representative cable-suspended dual-arm manipulation systems: the LiCAS arms suspended by a drone and the CRANEbot system, featuring two Pilz arms suspended by a crane. The identified dynamic models are validated by comparing their evolution with data acquired from the real systems showing a high (between 91.3% to 99.4%) correlation of the response signals. In a comparison performed with baseline pendulum models, our model increases the simulation accuracy from 64.4% to 85.9%. The simulation environment and the related controllers are released as open-source code.

Structural–Parametric Synthesis of the Planar Four-Bar and Six-Bar Function Generators With Revolute Joints

Abstract This paper studies a structural–parametric synthesis of the four-bar and Stephenson II, Stephenson III A, and Stephenson III B six-bar function generators. A four-bar function generator is formed by connecting two coordinate systems with given angles of rotation using a negative closing kinematic chain (CKC) of the RR type. Six-bar function generators are formed by connecting two coordinate systems using two CKCs: a passive CKC of the RRR type and a negative CKC of the RR type. The negative CKC of the RR type imposes one geometrical constraint to the relative motion of the links, and its geometric parameters are defined by least-squares approximation. Passive CKC of the RRR type does not impose a geometrical constraint, and the geometric parameters of its links are varied to satisfy the geometrical constraint of the negative CKC. Numerical results of the four-bar and six-bar function generators parametric synthesis are presented.

Dynamic simulation of the differential gear in road vehicles

The differential gear is a mechanism that is part of the kinematic chain of the vehicle’s transmission. The differential gear has the role of dividing the self-propulsion power flow received from the main drive into two branches, each transmitted to a drive wheel, giving them the possibility to rotate with different angular velocities, depending on the driving conditions. The present work presents the possibilities of computer-aided design and 3D modeling of the main drive and differential gear, respectively the bevel pinion, the crown wheel, the planet pinions and the satellites, using Autodesk Inventor Professional. The 3D model of the main drive - differential gear assembly, considered as a mechanism, was subjected to a dynamic study, using the Dynamic Simulation module. This involves the modeling of the kinematic couplings, the definition of the drive movement parameters and the external loads, respectively the graphical visualization of the kinematic and kinetostatic results for the various components of the mechanism, in real operating conditions, during a kinematic cycle. At the same time, based on the obtained results, the analysis by the finite element method of the most critical component elements, under straight-line driving and turning conditions, is presented.

Structural Synthesis of Planar Kinematic Chains and Their Detection of Isomorphism

Structural Synthesis of Planar Kinematic Chains and Their Detection of Isomorphism

Detection of Isomorphism of Kinematic Chains Using two DOF Using CSJV Matrix

Detection of Isomorphism of Kinematic Chains Using two DOF Using CSJV Matrix

Configuration design and kinematic performance analysis of a parallel wheelset suspension for a multi-wheeled pressurized lunar rover

When a multi-wheeled pressurized lunar rover (MWPLR) travels over rough terrain, the ability of its suspension to maintain wheel–ground contact is critical for achieving heavy load distribution and increasing its payload capacity. If the MWPLR uses an independent suspension, increasing the number of wheels worsens the wheel-off-ground problem. If the MWPLR utilizes a rocker–bogie suspension with a planar open-loop kinematic chain, it will have difficulty withstanding lateral impacts. In this study, to solve the above problems, the configurations of the 4-SS parallel mechanism were enumerated based on the Grassmann line geometry and screw theory to design a two-degree-of-freedom parallel wheelset suspension. The suspension integrated two axially parallel wheels on the same moving platform. Kinematic analysis showed that no singularities occurred in the workspace. The moving platform enabled large vertical movement and rotation of ±30°. Simulations showed that the suspension dramatically improved the ride comfort and wheel–ground contact capability of the MWPLR.

A Study to Compare the Kinematic Chain Exercise Versus Theraband Exercise on Pain for Subjects with Flat Foot

Background: Pes Planus (flatfoot) only becomes a medical issue when symptoms appear. This disease occurs inboth young children and adults. When the medial longitudinal arch (MLA) has raised to the point where it cannotbe maintained, the flatfoot changes form. This condition causes over pronation of the foot in contrast to normalfeet, resulting in heel eversion and moving the weight load inward to compress the MLA.1-2Purpose: To compare the effectiveness of kinematic chain exercise and TheraBand exercise session among theyoung adults with flat foot.Materials and Methods: 30 subjects participated and were taken from Saveetha college of physiotherapy basedon specific criteria and assigned to two groups. Pre and post assessment was taken using Numerical Pain RatingScale [NPRS] and Foot Functional Index Scale [FFI]. The interventions were given for 2 Weeks and the study wasconducted from November 2022 to April 2023. .Results: The study’s results revealed that both groups exhibited significant improvements in flat foot, with ap-value < 0.001. However, Group A showed more statistical significance than Group B.Conclusion: In conclusion, the commencement of two- week intervention plan, kinematic chain exercise showeda marked outcome on pain subjects with flat foot

A Layered Approach to the History and Physical Exam of the Athlete's Hip

Hip pathology is a common source of pain and dysfunction in athletes. Taking a layered approach to the history and physical examination of the athlete's hip is imperative to deciphering the vast differential diagnoses for an athlete's hip pain. Systematic evaluation of the (1) osteochondral, (2) capsulolabral, (3) musculotendinous, (4) neurovascular, and (5) kinematic chain layers of the hip allow for the comprehensive consideration of hip pain etiologies, including femoroacetabular impingement syndrome, labral tears, osteoarthritis, Coxa Saltans, hamstring and gluteal tendinopathy, and sacroiliac joint dysfunction, among numerous other conditions. A thorough history, including the location, acuity, quality, radiation, and sport-specific limitations of the hip pain, followed by a methodologic physical examination, with ordered inspection, gait, palpation, range of motion, strength testing, and provocative maneuvers, allows clinicians to arrive at an early and accurate diagnosis of hip pain. Only after a thorough history and physical examination can more specific diagnostic and therapeutic modalities be applied.

Experimental study and geometrical method to design bio-inspired robotic kinematic chains of inching-locomotion caterpillars

Inching-locomotion caterpillars (ILAR) show impressive environmental adaptation, having high dexterity and flexibility. To design robots that mimic these abilities, a novel bioinspired robotic design (BIROD) method is presented. The method is composed by an algorithm for geometrical kinematic analysis (GEKINS) to standardize the proportional dimensions according to the insect’s anatomy and obtain the kinematic chains. The approach is experimentally applied to analyze the locomotion and kinematic chain of these specimens: Geometridae—two pair of prolegs (represents 35 000 species) and Plusiinae—three pair of prolegs (represents 400 species). The obtained data indicate that the application of the proposed method permits to locate the attachment mechanisms, joints, links, and to calculate angular displacement, angular average velocity, number of degrees of freedom, and thus the kinematic chain. Geometridae in contrast to Plusiinae, shows a longer walk-stride length, a lower number of single-rotational joints in 2D (3 DOF versus 4 DOF), and a lower number of dual-rotational joints in 3D (6 DOF versus 8 DOF). The application of BIROD and GEKINS provides the forward kinematics for 35 400 ILAR species and are expected to be useful as a preliminary phase for the design of bio-inspired arthropod robots.

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.

Multivariate analysis of the kinematics of an upper limb rehabilitation robot.

Purpose: The purpose of this work is to present a multivariate analysis of the kinematics of an upper limb rehabilitation robot. Comparing multiple concepts of kinematic chains makes it possible to identify advantages and disadvantages and, as a consequence, choosing the optimal solution to create a physical device. Such actions shall contribute towards automation of the rehabilitation process, bringing benefits to both therapists and patients in comparison with conventional rehabilitation. Methods: Multivariate analysis of kinematics was performed on the basis of three concepts of the kinematic chain of an exoskeleton, enabling the rehabilitation of both right and left upper limb within the area of the shoulder joint, elbow joint and wrist. The kinematic chain allows the performance of simple and complex movements. Results: The results of the conducted multivariate kinematic analysis define specific movements and angular ranges, which may be performed while applying one of the proposed concepts of the robot design. The results made it possible to determine the optimum solution to the kinematic diagram and construction design, which best satisfy the expectations for effective rehabilitation. Conclusions: The analysis of the kinematic diagram concept of the exoskeleton should be done in relation to its design (construction form). Considering the obtained parameters, it is necessary to find an optimum concept and wisely manoeuvre the values, in order to avoid a situation in which one significant parameter influences another, equally important one. It is noteworthy that the introduction of changes into particular segments of the kinematic chain often has a significant impact on other segments.

The use of differentials to increase the efficiency of orienting robotic devices of agricultural equipment

Robots are used in modern agricultural equipment. There are several types of robot designs: articulated robots, delta robots, sсara robots and others. Almost every robot has in its design an orienting device, designed to orient the tool, used by the robot in space. Orienting devices differ from each other by different structural diagrams of transmission mechanisms and types of links, functioning in the mechanisms. All orienting devices are united by a design feature, which consists in the fact, that in order to rotate the tool around the axis of any kinematic pair, which is the degree of mobility of the orienting device, it is necessary to rotate several electric drives. If you rotate with one electric drive, the tool will make a spherical movement. The reason for this effect is that the kinematic chains, through which rotation is transmitted from the electric drive to the tool, intersect with each other. The use of differentials in the design will allow the tool to rotate around one axis by one electric drive, which gives some advantages in motion control. The article describes the design features and the principle of operation of the orienting device with differentials.

Design of a wearable shoulder exoskeleton robot with dual-purpose gravity compensation and a compliant misalignment compensation mechanism.

This paper presents the design and validation of a wearable shoulder exoskeleton robot intended to serve as a platform for assistive controllers that can mitigate the risk of musculoskeletal disorders seen in workers. The design features a four-bar mechanism that moves the exoskeleton's center of mass from the upper shoulders to the user's torso, dual-purpose gravity compensation mechanism located inside the four-bar's linkages that supports the full gravitational loading from the exoskeleton with partial user's arm weight compensation, and a novel 6 degree-of-freedom (DoF) compliant misalignment compensation mechanism located between the end effector and the user's arm to allow shoulder translation while maintaining control of the arm's direction. Simulations show the four-bar design lowers the center of mass by cm and the kinematic chain can follow the motion of common upper arm trajectories. Experimental tests show the gravity compensation mechanism compensates gravitational loading within Nm over the range of shoulder motion and the misalignment compensation mechanism has the desired 6 DoF stiffness characteristics and range of motion to adjust for shoulder center translation. Finally, a workspace admittance controller was implemented and evaluated showing the system is capable of accurately reproducing simulated impedance behavior with transparent low-impedance human operation.

Synergistic effects of transcutaneous spinal stimulation and neuromuscular electrical stimulation on lower limb force production: Time to deliver.

Transcutaneous spinal stimulation (TSS) and neuromuscular electrical stimulation (NMES) can facilitate self-assisted standing in individuals with paralysis. However, individual variability in responses to each modality may limit their effectiveness in generating the necessary leg extension force for full body weight standing. To address this challenge, we proposed combining TSS and NMES to enhance leg extensor muscle activation, with optimizing timing adjustment to maximize the interaction between the two modalities. To assess the effects of TSS and NMES on knee extension and plantarflexion force, ten neurologically intact participants underwent three conditions: (1) TSS control, (2) NMES control, and (3) TSS + NMES. TSS was delivered between the T10 and L2 vertebrae, while NMES was delivered to the skin over the right knee extensors and plantarflexors. TSS and NMES were administered using a 15 Hz train of three 0.5 ms biphasic pulses. During the TSS + NMES condition, the timing between modalities was adjusted in increments of ¼ the interval within a 15 Hz frequency, i.e., 66, 49.5, 33, 16.5, and 1 ms. NMES combined with TSS, produced synergistic effects even on non-targeted muscle groups, thereby promoting leg extension across multiple joints in the kinematic chain. The sequence of NMES or TSS trains relative to each other did not significantly impact motor output. Notably, a delay of 16.5 to 49.5 ms between interleaved TSS and NMES pulses, each delivered at 15 Hz, results in more robust and synergistic responses in knee extensors and plantarflexors. By adjusting the timing between TSS and NMES, we can optimize the combined use of these modalities for functional restoration. Our findings highlight the potential of integrated TSS and NMES protocols to enhance motor function, suggesting promising avenues for therapeutic applications, particularly in the rehabilitation of individuals with SCI.

The Midfoot Joint Complex (Foot Arch) Contributes to the Upper Body Position in Bipedal Walking and Coordinates With the Lower Limb Joints.

This study estimated the contribution of the midfoot joint complex (MJC) kinematics to the pelvis anterior-posterior positions during the stance phase of walking and investigated whether the MJC is functionally coordinated with the lower limb joints to maintain similar pelvic positions across steps. Hip, knee, ankle, and MJC sagittal angles were measured in 11 nondisabled participants during walking. The joints' contributions to pelvic positions were computed through equations derived from a link-segment model. Functional coordination across steps was identified when the MJC contribution to pelvic position varied and the summed contributions of other joints varied in the opposite direction (strong negative covariations [r ≤ -.7] in stance phase instants). We observed that the MJC plantarflexion (arch raising) during the midstance and late stance leads the pelvis backward, avoiding excessive forward displacement. The MJC was the second joint that contributed most to the pelvis positions (around 18% of all joints' contributions), after the ankle joint. The MJC and ankle were the joints that were most frequently coordinated with the other joints (≅70% of the stance phase duration). The findings suggest that the MJC is part of the kinematic chain that determines pelvis positions during walking and is functionally coordinated with the lower limb joints.

Design, modeling, and experimental analysis of the Crawler Unit for inspection in constrained space

Inspections of industrial and civil infrastructures prevent unexpected failures that may lead to loss of life. Although inspection robotics is gaining momentum, most of field operations are still performed by human workers. For inspection robots, the main limiting factors are the low versatility and reliability in dynamic, non-structured and highly complex environments. To tackle these issues, we have designed a modular and self-reconfigurable hybrid platform, which consists of three units: the mobile Main Base and two Crawler Units with docking interfaces. The Crawler Unit operates in constrained environments and narrow spaces, while the Main Base will inspect wide areas and deploy/recover the Crawler Units near/from inspection sites, as in marsupial robots. Docking interfaces will allow the Crawler Units to reconfigure into a snake robot or mobile manipulators. In particular, the Crawler Units consist of four modules connected by three kinematic chains for nine active joints in total. Each module is equipped with half active, half passive tracks for moving. This paper discusses in detail the dynamic model of the Crawler Unit, especially focusing on the definition of effective constraint equations, which closely model the system features avoiding common simplifications. Numerical simulations and physical experiments validate the proposed dynamic model of the Crawler Unit.

A new structural code for detecting isomorphism of kinematic chains with simple, multiple and gear pairs

A new structural code for detecting isomorphism of kinematic chains with simple, multiple and gear pairs

Jacobian-Sensitivity Approach for Identifying Machine Dynamic Model Parameters of Robots with Flexible Joints

The versatility and large work envelope have made robots a fixture in the field of assembly for years. However, their lower stiffness and pose dependency require robust models to find optimal trajectories even for high accuracy applications. A significant obstacle in this domain is parametrizing such models of compliant robots during operation. Addressing this gap, and considering the trend of robots performing manufacturing tasks in parallel with assembly, we present an automated identification process to estimate the stiffness and damping parameters of robot joints within a milling process. This method relies solely on universally accessible kinematic chain data and force and acceleration measurements at the tool center point, eliminating the need for specialized equipment. The approach is based on a multi-body simulation, which includes flexible 6-DOF bushing joints. Key to our approach is using Jacobian-based sensitivities inside a Random Search (RS) algorithm to navigate the complexities of a sparse multi-dimensional parameter space. Our approach is versatile enough to accommodate various parameter types. We test our approach on a simulated 3-joint robot with 6 DOF per joint. By pairing the Jacobian-based sensitivities with adaptions made to the RS algorithm, we obtain accurate predictions for unknown input data with a mean relative displacement error of 2%.

A new structural code for detecting isomorphism of kinematic chains with simple, multiple and gear pairs

A new structural code for detecting isomorphism of kinematic chains with simple, multiple and gear pairs

Acute responses of postural alignment and intermuscular coherence to anti-gravitational muscle engagement—A randomized crossover trial

IntroductionPosture is a facet of clinical assessment in several rehabilitative disciplines. Despite extensive clinical focus, the precision with which posture can be evaluated and intervened upon is limited by the very general terms used to describe it. The purpose of this crossover trial was to quantify the effects of targeted postural intervention motivated by theoretical sagittal gravitational collapsing (SGC) tendencies on: 1) distance from SGC, 2) intermuscular coherence (iCOH), and 3) kinematic chain connectivity. MethodsTen healthy adults (24.50 ± 1.18 years, 172.72 ± 10.19 cm, 76.47 ± 14.60 kg) completed pre- and post-intervention testing on two occasions involving contrasting interventions: promote postural muscle (PPM) vs. reduce compensatory muscle (RCM) engagement. Distance from SGC, iCOH, and kinematic chain connectivity were quantified from electromyography and/or kinematic data acquired during tests administered before and after interventions. Effects of Treatment [PPM, RCM] and Time [Pre, Post] were tested with linear mixed models. ResultsA Treatment*Time interaction was observed for distance from SGC. Post-intervention distance from SGC was greater following PPM only (p < 0.01). A Treatment*Time interaction was observed for hi-frequency trunk muscle iCOH, with a post-intervention increase corresponding to the RCM intervention (p < 0.007). Additional iCOH effects did not differ by intervention. ConclusionDistance from SGC is acutely modifiable and increases following exercises to facilitate anti-SGC muscles. Convergent findings related to kinematic chain connectivity and prescriptive neural binding were not observed. These observations suggest that it may be possible to describe, evaluate, and intervene upon posture in reference to a specific, mechanistic theory regarding the function of postural alignment.