Kinematic Optimization Research Articles

Kinematic Optimization for the Design of a Collaborative Robot End-Effector for Tele-Echography

Tele-examination based on robotic technologies is a promising solution to solve the current worsening shortage of physicians. Echocardiography is among the examinations that would benefit more from robotic solutions. However, most of the state-of-the-art solutions are based on the development of specific robotic arms, instead of exploiting COTS (commercial-off-the-shelf) arms to reduce costs and make such systems affordable. In this paper, we address this problem by studying the design of an end-effector for tele-echography to be mounted on two popular and low-cost collaborative robots, i.e., the Universal Robot UR5, and the Franka Emika Panda. In the case of the UR5 robot, we investigate the possibility of adding a seventh rotational degree of freedom. The design is obtained by kinematic optimization, in which a manipulability measure is an objective function. The optimization domain includes the position of the patient with regards to the robot base and the pose of the end-effector frame. Constraints include the full coverage of the examination area, the possibility to orient the probe correctly, have the base of the robot far enough from the patient’s head, and a suitable distance from singularities. The results show that adding a degree of freedom improves manipulability by 65% and that adding a custom-designed actuated joint is better than adopting a native seven-degrees-freedom robot.

Regressional analysis of the patella parameters of male cadaveric knees found among South East Nigerians: A useful guide to patella replacement during total knee replacement

Background: Total knee replacement (TKR) is a viable option for the management of osteoarthritis, and it has proven to be both effective and successful. Optimization of the patellofemoral joint kinematics is important for surgeons who choose to resurface the patella during TKR. The whole idea is to get the final patellar bone-prosthesis composite thickness to match the original patellar thickness before the surgery. Aim: To correlate patella height (PH) and patella width (PW) with patella thickness (PT) as well as build a regression model through which the dimensions can predict the thickness among the native knees of the South East Nigerians. Materials and Methods: This is a correlational, nonexperimental, and observational study conducted on 60 knees from 30 male cadavers taken from the anatomy laboratory of the University of Nigeria, Enugu Campus. The PH, PW, and PT were measured by using specific endpoints and the observed data were subjected to statistical correlation analysis. Results: PH and PT were strongly positively correlated, r(59) = 0.797, P < 0.001. Results of the multiple linear regression indicated that there was a collective significant effect between the PH, PW, and PT (F(2, 57) = 51.486, P < 0.001, R2 = 0.644). The individual predictors were examined further and indicated that PH (t = 4.931, P < 0.001) was a significant predictor whereas PW (t = 1.153, P = 0.254) was not a significant predictor in the model. The patella’s predicted thickness is equal to 1.734+0.328 (PH in cm) +0. PT increased 0.328 cm for each centimeter of height. The PH was the only significant predictor of PT. Conclusion: This study was able to establish a correlation between the PH, PW, and PT, and it was able to demonstrate PH and PW as predictors of PT among the population of South East Nigeria.

Preliminary Assessment of a Postural Synergy-Based Exoskeleton for Post-Stroke Upper Limb Rehabilitation.

Upper limb exoskeletons have drawn significant attention in neurorehabilitation because of the anthropomorphic mechanical structure analogous to human anatomy. Whereas, the training movements are typically unorganized because most exoskeletons ignore the natural movement characteristic of human upper limbs, particularly inter-joint postural synergy. This paper introduces a newly developed exoskeleton (Armule) for upper limb rehabilitation with a postural synergy design concept, which can reproduce activities of daily living (ADL) motion with the characteristics of human natural movements. The semitransparent active control strategy with the interactive force guidance and visual feedback ensured the active participation of users. Eight participants with hemiplegia due to a first-ever, unilateral stroke were recruited and included. They participated in exoskeleton therapy sessions for 4 weeks, with passive/active training under trajectories and postures with the characteristics of human natural movements. The primary outcome was the Fugl-Meyer Assessment for Upper Extremities (FMA-UE). The secondary outcomes were the Action Research Arm Test(ARAT), modified Barthel Index (mBI), and metric measured with the exoskeleton After the 4-weeks intervention, all subjects showed significant improvements in the following clinical measures: the FMA-UE (difference, 11.50 points, p = 0.002), the ARAT (difference, 7.75 points ), and the mBI (difference, 17.50 points, p = 0.003 ) score. Besides, all subjects showed significant improvements in kinematic and interaction force metrics measured with the exoskeleton. These preliminary results demonstrate that the Armule exoskeleton could improve individuals' motor control and ADL function after stroke, which might be associated with kinematic and interaction force optimization and postural synergy modification during functional tasks.

Six-Legged Walking Robot (Hexabot), Kinematics, Dynamics and Motion Optimization

The movement of a walking six – legged robot hexabot (a "spider" robot) with the possibility of implementing various movements is considered. The equations of kinematics and dynamics of a separate robot leg with three degrees of freedom are written out, and the question of optimizing the robot movement is considered based on the study of dynamic equations. At the first stage for solving this problem, one leg is considered separately, as a kinematic system with open kinematics and with three degrees of freedom. The kinematics equations were presented in matrix form using the principle of rotation of the coordinate system. The dynamics equations are based on Lagrange equations of the second kind. The mass of the legs, reduced to the center of gravity, moments of inertia, moments developed by engines were taken into account, and ets. The conclusions were made about the optimal movement of the leg based on the obtained equation of kinetic energy of the robot’s leg based on the obtained equation of the kinetic energy of the robot leg. This paper doesn’t consider the movement of the entire platform (the spider’s “body”), nor does it consider the influence of the friction force that occurs in kinematic pairs and when the robot’s legs touch the surface during movement.

Accuracy improvement of 6-UPS Stewart forward kinematics solution based on self-aggregating MFO algorithm

In this paper, a Stewart’s positive solution optimization model is proposed, for obtaining the complex solution to a Stewart’s forward kinematics problem, considering the existence of multiple solutions. The model converts the positive kinematics problem into an optimization problem, in which the value of the objective function is used to represent the precision of Stewart’s positive solution. A self-aggregating moth–flame optimization algorithm (SMFO) is used to improve the accuracy of Stewart’s forward kinematics solution. Two features were added to the conventional MFO algorithm to obtain a more stable balance between global and local explorations. First, Gaussian distribution was used for the flame population to select suitable individuals for Levy Flight operation, increase the diversity of the population, and enhance the algorithm’s ability to jump out of a local optimum. Second, in the middle and late iterations, the positions of the flames were periodically adjusted using the light intensity-attraction characteristic (LIAC) to strengthen the connection between individual flames and enhance the local exploration ability of the algorithm. The proposed SMFO algorithm is compared with three classic meta-heuristic algorithms for eight benchmark functions. Experimental results indicate that the SMFO algorithm is significantly better than the other three algorithms in terms of solution quality and convergence rate. To verify the effectiveness of the SMFO algorithm in solving the Stewart positive kinematics optimization model, values of eight sets of conventional position and posture parameters as well as limiting position and posture parameters were randomly obtained, and values of 16 sets of position and posture parameters were obtained using four algorithms. The results indicate that the SMFO algorithm can improve the accuracy of the forward kinematics solution to 4.05E-09 mm.

Production Process Automation for Construction of Monolithic Buildings and Structures

Article presents a scientific approach to creating a complex production process automation system for construction of monolithic buildings and structures (MBS). Specific features of systems with complex structure which present themselves in the way they function and by the interaction of local control systems within integrated system for production process automation were discovered. Justification is given to the structure of creation of local systems for automation of MBS construction processes and their functioning within interconnected complex control system. Model for optimal transportation of concrete mixture to the pouring site with sliding thermo-active formwork with hydraulic actuators is presented in the article. The model is integrated by parameters of physical and mechanical processes. Concept of production process automation for construction of MBS was outlined. The concept is implemented in accordance with specific operational and technological and IT support of integrated system for automated control. The greatest potential for increasing the rate of housing construction is possessed by the technology of monolithic housing construction. However, traditional methods of erecting monolithic structures are associated with increased labor intensity, a significant share of manual operations, and the lack of objective instrumental control of the quality of concrete work, which significantly affects the increase in the time and cost of construction. A radical solution to the problem of increasing the efficiency of monolithic housing construction technology is possible only through the integrated use of automation, robotization and microprocessor technology. A method and means have been developed for automating the processes of feeding, distributing, laying and compacting concrete mixture, which make it possible to fundamentally change not only the nature of the work of construction workers, but also its organization, productivity, quality and intellectual saturation. The technical requirements for the automated structures of switchgears are formulated, based on taking into account the specific technological conditions for the production of concrete works. A criterion is proposed and a methodology for choosing the optimal kinematic structure of an automated switchgear for the production of concrete works is developed. The problem of determining the geometric characteristics (the length of the links, the angles of rotation of the joints), the distribution booms for the given constructive and technological conditions of concreting has been solved.

Dynamic Modeling and Error Analysis of a Cable-Linkage Serial-Parallel Palletizing Robot

The efficiency and accuracy for parallel robot play a significant role in the industrial production process. In order to further improve the motion performance of parallel robot, this paper focuses on the study of mechanism design, dynamic modeling and error analysis of a cable-linkage serial-parallel palletizing robot (CSPR). Firstly, the CSPR is designed as a series-parallel hybrid mechanism driven by flexible cables, which can effectively reduce the inertia and improve the dynamic response. As is known that kinematic design optimization of compliant mechanisms requires accurate yet efficient mathematical models, the kinematics and dynamic models are established by the homogeneous coordinate transformation method and Lagrange equation. Based on the dynamic mathematical model of the robot, a variety of sensors are chosen to construct the hardware control system and the sliding mode variable structure control strategy is also designed based on motion errors. Then, the motion performance and load carrying capacity of the CSPR were analyzed and compared in different operating conditions respectively, and the results verify the validity and efficiency of the mechanism.

A Planar Parallel Device for Neurorehabilitation

The patient population needing physical rehabilitation in the upper extremity is constantly increasing. Robotic devices have the potential to address this problem, however most of the rehabilitation robots are technically advanced and mainly designed for clinical use. This paper presents the development of an affordable device for upper-limb neurorehabilitation designed for home use. The device is based on a 2-DOF five-bar parallel kinematic mechanism. The prototype has been designed so that it can be bound on one side of a table with a clamp. A kinematic optimization was performed on the length of the links of the manipulator in order to provide the optimum kinematic behaviour within the desired workspace. The mechanical structure was developed, and a 3D-printed prototype was assembled. The prototype embeds two single-point load cells to measure the force exchanged with the patient. Rehabilitation-specific control algorithms are described and tested. Finally, an experimental procedure is performed in order to validate the accuracy of the position measurements. The assessment confirms an acceptable level of performance with respect to the requirements of the application under analysis.

Optimal kinematic synthesis of 6 bar rack and pinion Ackerman steering linkage

In this article, synthesis and simultaneous optimization of a steering mechanism is proposed for enhancing the cornering performance of a Formula Students competition car. A planar six-bar steering mechanism is synthesized assuming it as two separate slider-crank arrangements with a rigid link between the sliders. Numerical optimization is performed using multi-objective genetic algorithm (MOGA), which includes minimization of differences between both slider displacements and summation of deviations from true Ackerman geometry for a set of steering inputs. The selection of various parameters for running MOGA is well established based on iterative way. The seven variables (such as wheelbase and track width lengths, tie rod, tie-arm etc.) are optimized and used to construct the Ackerman steering geometry. Finally, the outer to inner tyre rotations of obtained geometry is calculated and compared with the predefined targeted values of actual Ackerman criteria.

Does double calibration coupled with a closed loop multibody kinematic optimization improve scapular kinematic estimates?

Assessment of scapular kinematics has been a challenging topic for several decades. While invasive procedures, such as biplanar fluoroscopy or intra cortical pins, have showed high accuracy to meas...

Inverse kinematic optimization for 7-DoF serial manipulators with joint limits

Inverse kinematic optimization for 7-DoF serial manipulators with joint limits

Recent advancements in flapping mechanism and wing design of micro aerial vehicles

Recent studies on understanding of natural flyers have encouraged researchers in development of micro aerial vehicles mimicking birds and insects such as hummingbirds, dragonflies, bats and many more. The vehicles find their applications in reconnaissance and situational awareness in combat field, search and rescue operations, biological and nuclear compromised sites and broadcasting and sports. The focus of this review is to assess recent progress in sub systems of these vehicles including drive mechanisms, actuation mechanisms and wing designs that define the aerodynamics, propulsion, stability, and control of the vehicles. Limited research has been carried out on drive mechanisms capable of producing figure-of-eight wingtip motion contrary to conventional four and five-bar linkage mechanisms along with modified planar and spherical attachments. Motor and piezoelectric actuation mechanisms are being used extensively in these vehicles due to lightweight and power efficiency as compared to non-conventional power sources. Wing shape and rigidity plays a key role in determining the required lift and thrust along with frequency limitations and material constraints. A relatively new field of structural and kinematic optimization for the development of a lightweight flapping vehicle with high endurance capability is also a part of this review. This review has pointed out the research gaps including 3-DoF piezoelectric kinematics, under-actuated mechanisms, structural contact analysis, limited static and dynamic structural analysis, limited fatigue analysis and development of optimization techniques.

Kinematic Chain Optimization Design Based on Deformation Sensitivity Analysis of a Five-Axis Machine Tool

This paper focuses on optimization of kinematic chain to reduce force-induced error in the scheme design phase of a five-axis machine tool. After conducting process planning on the machining target, local deformation of motion units in cutting positions is considered using a geometric way. A mathematical model is then established describing the influence of local deformation error on the general machining error through homogeneous transformation matrices. Conceptual model of the machine tool is constructed to obtain deformation distribution using static FEA. Error sensitivity coefficients are then calculated and compared among all alternative kinematic chains to select the optimized scheme. The proposed method is verified through a designing example of a five-axis vertical machining center. The optimized kinematic chain could lower the magnitude of deformation sensitivities by 9.69% and increase error equalization variance by 71.25% compared to the conventional method.

Globally Optimal Inverse Kinematics Method for a Redundant Robot Manipulator with Linear and Nonlinear Constraints

This paper presents a novel inverse kinematics global method for a redundant robot manipulator performing a tracking maneuver. The proposed method, based on the choice of appropriate initial joint trajectories that satisfy the kinematic constraints to be used as inputs for a multi-start optimization algorithm, allows for the optimization of different integral cost functions, such as kinetic energy and joint torques norm, and can provide solutions with a variety of constraints, both linear and nonlinear. Furthermore, it is suitable for multi-objective optimization, and it is able to find multiple optima with minimal input from the user, and to solve cyclic trajectories. Problems with a high number of parameters have been addressed providing a sequential version of the method based on successive stages of interpolation. The results of simulations with a three-Degrees-of-Freedom (DOF) redundant manipulator have been compared with a solution available in the literature based on the calculus of variations, thus leading to the validation of the method. Moreover, the effectiveness of the presented method has been shown when used to solve problems with constraints on joint displacement, velocity, torque, and power.

A unified kinematics modeling, optimization and control of universal robots: from serial and parallel manipulators to walking, rolling and hybrid robots

The paper develops a unified kinematics modeling, optimization and control that is applicable to a wide range of autonomous and non-autonomous robots. These include hybrid robots that combine two or more modes of operations, such as combination of walking and rolling, or rolling and manipulation, as well as parallel robots in various configurations. The equations of motion are derived in compact forms that embed an optimization criterion. These equations are used to obtain various useful forms of the robot kinematics such as recursive, body and limb-end kinematic forms. Using the modeling, actuation and control equations are derived that ensure traversing a desired path while maintaining balanced operations and tip-over avoidance. Various simulation results are provided for a hybrid rolling-walking robot, which demonstrate the capabilities and effectiveness of the developed methodologies.

Semi-Isotropically Optimized Stewart Platform Manipulator Design with Actuator Stroke Constraint

The isotropic property has been a general use in the context of kinematic design optimization of robotic manipulators. In this paper, the semi-isotropic home or neutral configuration of a semi-regular Stewart platform manipulator has been designed by introducing the stroke constraint of all the legs through the assessment of new actuator variable termed as ‘fractional excess margin’ of actuation. The constrained optimization problem structured with the quadratic functions relating all the rotational and translational motion of the tool center point and the actuator stroke. The numerical solution obtained from the system of nonlinear equations has been interpreted graphically through the analysis of the ‘fractional excess margin’ for prescribed single degree of motions of Stewart platform manipulator. Finally, a trade-off has been made between the goals of optimum semi-isotropic design configuration and that of the configuration with the actuators in the legs of the least stroke requirement.

Clinically derived biomechanical criteria for the Trendelenburg test

BackgroundThe Trendelenburg test has been used to assess hip abductor muscle function. A standardized evaluation of the test requires an assessment of both pelvis and trunk coronal plane alignment as the patient stands on one leg for 30 s. Coronal plane biomechanics using motion analysis allows for development of objective criteria to grade the test response. The aim of this study was to develop biomechanical criteria of the pelvis and trunk coronal plane kinematics. MethodsThe video of 39 subjects with acetabular hip dysplasia performing the test while instrumented with a full-body modified Plug-In-Gait marker set for three-dimensional kinematic analysis, were evaluated by two orthopedic surgeons and one senior level biomechanist. Reviewers as a group assessed whether the subject had a positive test and noted the reason using guidelines outlined in the literature. Coronal plane trunk and pelvic angles of all subjects were analyzed and Receiver Operating Characteristic curves were used to determine optimal kinematic cutoff values for each positive Trendelenburg test reason. FindingsThere were 26/39 patients who reviewers identified as having a positive test. Area under the curve of the receiver operating characteristic curve for trunk and pelvis mean/minimum were greater than 0.75. The curve was used to identify the optimal cut-offs of trunk lean and pelvic obliquity mean/minimum. InterpretationThe biomechanical criteria developed includes clinically derived coronal plane kinematic cut-offs of the pelvic and trunk angles. The criteria can be used within a motion capture setting for the standardization of the grading of the test response.

Mixing Yarns and Triangles in Cloth Simulation

AbstractThis paper presents a method to combine triangle and yarn models in cloth simulation, and hence leverage their best features. The majority of a garment uses a triangle‐based model, which reduces the overall computational and memory cost. Key areas of the garment use a yarn‐based model, which elicits rich effects such as structural nonlinearity and plasticity. To combine both models in a seamless and robust manner, we solve two major technical challenges. We propose an enriched kinematic representation that augments triangle‐based deformations with yarn‐level details. Naïve enrichment suffers from kinematic redundancy, but we devise an optimal kinematic filter that allows a smooth transition between triangle and yarn models. We also introduce a preconditioner that resolves the poor conditioning produced by the extremely different inertia of triangle and yarn nodes. This preconditioner deals effectively with rank deficiency introduced by the kinematic filter. We demonstrate that mixed yarns and triangles succeed to efficiently capture rich effects in garment fit and drape.

ДОСЛІДЖЕННЯ ПРОЦЕСУ ПЕРЕМІЩЕННЯ СИПКОГО МАТЕРІАЛУ В НЕАКТИВНІЙ ЗОНІ МІЖ ГВИНТОВИМИ СЕКЦІЯМИ

The article presents the results of theoretical and experimental studies of the process of moving bulk material in the inactive zone between hinged screw sections of a flexible screw conveyor. The influence of the gap between the edges of adjacent screw sections and the magnitude of their circular displacement on the process of continuous transportation of bulk material is presented. The results of theoretical and experimental studies are compared. This will allow choosing the optimal design, kinematic and technological parameters of the developed sectional screw working body when transporting bulk agricultural materials along curved paths, both in horizontal and inclined directions, as well as along curved paths.

Kinematic and dynamic design and optimization of a parallel rehabilitation robot

In this paper, a method for concurrent optimum design of a complex parallel manipulator is introduced. The manipulator is a three-degree-of-freedom mechanism used as a walking rehabilitation device. The proposal deals with several optimization issues; firstly, the methodology is applied to a system recently designed and, in the best of our knowledge, the control policy, and dynamic model have not been published before, secondly, we propose an objective function which considers dexterity and singular manipulators, as well as energy and position error, and thirdly, we propose an optimization algorithm which successfully approximates the optimum solution, delivering low-cost feasible designs with fewer function evaluations than a comparing Genetic Algorithm. A set of numerical simulations validate the methodology and evidence its robustness since it delivers quite similar designs in several independent executions.