Kinematic Design Research Articles

Cam 형상을 이용한 VSA (Variable Stiffness Actuator) 메커니즘 설계

As the exoskeleton robot for the assistance of walking is on the rise, HRI (Human-Robot Interaction) come to be an important issue. So in this research the angle following Variable Stiffness Actuator by using cam for overcoming the limitation of volume and weight in existing mechanisms. For this mechanism determinant of stiffness is not an absolute value but it can be change from zero to rigid by the location of the pivot in the gage between the application point of the input force and output force. So it can be miniaturized and have the volumetric advantage by kinematic design. This variable stiffness system make the HRI effective and the safety from injury resulted from the malfunction and the wrong control can be guaranteed.

Cam 형상을 이용한 VSA (Variable Stiffness Actuator) 메커니즘 설계

As the exoskeleton robot for the assistance of walking is on the rise, HRI (Human-Robot Interaction) come to be an important issue. So in this research the angle following Variable Stiffness Actuator by using cam for overcoming the limitation of volume and weight in existing mechanisms. For this mechanism determinant of stiffness is not an absolute value but it can be change from zero to rigid by the location of the pivot in the gage between the application point of the input force and output force. So it can be miniaturized and have the volumetric advantage by kinematic design. This variable stiffness system make the HRI effective and the safety from injury resulted from the malfunction and the wrong control can be guaranteed.

A Methodology for the Application of Virtual Evaluation Methods within the Design Process of Cold Forged Steel Pinions

AbstractGears are essential machine elements in the drivetrain and transmission technology. The operational behaviour of a gear pairing is influenced by the design of the gear kinematics as well as the component properties. With regard to an improvement of performance and service life, the targeted modification of tooth geometry and component properties offers a promising approach. Thus, the achievable geometric and mechanical component properties are influenced by the manufacturing process, which must be taken into account in the design process. The application of virtual evaluation methods is suitable for this purpose. For the manufacturing of steel gears, cold forging provides the potential of achieving beneficial mechanical properties in a highly productive process. Major challenges for the industrial application are the short service life of the cost- intensive tools and the low geometric accuracy in comparison to machining processes. Within this study the design of the tooth geometry as well as the associated forming tool are investigated. The aim is to derive recommendations regarding an optimization of the resulting component properties and operational behaviour.

Kinematic Design Optimization of an Eight Degree-of-Freedom Upper-Limb Exoskeleton

SummaryThis paper studies the problem of optimizing the kinematic structure of an eight degree-of-freedom upper-limb rehabilitation exoskeleton. The objective of optimization is achieving minimum volume and maximum dexterity in the workspace of daily activities specified by a set of upper-arm configurations. To formulate the problem, a new index is proposed for effective characterization of kinematic dexterity for wearable robots. Additionally, a set of constraints are defined to ensure that the optimal design can cover the desired workspace of the exoskeleton, while singular configurations and physical interferences are avoided. The formulated multi-objective optimization problem is solved using an evolutionary algorithm (Non-dominated Sorting Genetic Algorithm II) and the weighted sum approach. Among the resulted optimal points, the point with least sensitivity with respect to the variations of design variables is chosen as the final design.

Two-dimensional piston pump: Principle, design, and testing for aviation fuel pumps

Aviation fuel pumps of the future are required to be highly efficient and lightweight. As such, this work presents the designs of various mechanisms and structures of advanced two-dimensional piston pumps for aero-engines, and their universal kinematic design methods are detailed herein. The efficiency of various piston pump prototypes was experimentally tested at various speeds in an open circuit. The experimental results indicate that two-dimensional piston pumps have a volumetric efficiency >91% and a higher power–mass ratio than conventional fuel pumps under all the conditions studied. Furthermore, the structural and material problems encountered during testing can provide a blueprint for further improvement of the design and processing of two-dimensional piston fuel pumps.

Kinematic Design of a Novel Two Degree-of-Freedom Parallel Mechanism for Minimally Invasive Surgery

A novel two degree-of-freedom (2-DOF) parallel mechanism with remote center-of-motion (RCM) is proposed for minimally invasive surgical applications in this paper. A surgical manipulator with expected three-rotation and one-translation (3R1T) outputs can be obtained by serially connecting a revolute pair (R) and a prismatic pair (P) to the mechanism. First, kinematics of the new mechanism is analyzed and the corresponding velocity Jacobin matrix is established. Then, singularity identification of the mechanism is performed based on screw theory. Further, main dimensions of the mechanism are designed, and a physical prototype is developed to verify the effectiveness of executing RCM. The proposed mechanism has relatively simple kinematics, and can obtain a noninterference and nonsingularity cone workspace with the top angle of 60 deg based on a compact structure.

Transmission index of a class of parallel manipulators with 3-RS(SR) primary structures based on pressure angle and equivalent mechanism with 2-SS chains replacing RS chain

In this paper, we present a new transmission index (TI) for kinematic performance evaluation of a class of parallel manipulators with a 3-RS (or 3-SR) structure; termed the primary structure obtained by locking all actuated joints in the manipulators. TI is based on the pressure angle that is defined in a kinematically equivalent structure, a 6-SS structure by replacing an RS chain of the primary structure with a pair of SS chains, which can reflect the practical force transmission and constraint characteristics of R joint composed of two bearings in the original manipulator. The effectiveness of TI is verified by considering 3-PRS and 3-RPS parallel manipulators. The singularity analysis, relationships between the maximum joint forces and index values, distribution of TI inside the workspace, and an application of TI to a kinematic design are demonstrated. The proposed approach can indicate both output and constraint singularity conditions with a single index, can be achieved by simple calculation process without complicated normalization, and can include the width of the revolute joint in the kinematic performance evaluation of this class of parallel manipulators.

Kinematics of Metallurgical Cutters with Parallel Blades

Abstract—In the operation of cutters with parallel blades, three periods may be identified: pressing of blades into the metal; cutting; and cleavage (separation). The greatest force is required around the onset of cutting. Since one of the blades is immobile, the other must pass through the whole thickness of the metal in the course of cutting. For example, if the metal thickness is 20 mm, the upper blade must travel a distance of 20 mm to complete the cutting process. In the case of two mobile blades moving in opposite directions, the cutting forces will be less. If the metal thickness is 20 mm, each blade must travel a distance of 10 mm in the complete cutting process. To simplify the design in the case of two mobile blades, they must both be powered by a single drive. The question that arises here is whether opposing motion of the blades is possible with guaranteed strength of the components transmitting the force to the blades. A kinematic cutter design with blades that move in parallel within the vertical plane is proposed. A benefit of this design is that, in opposing cutter motion, less cutting force is required. In addition, the force from each blade is distributed to two rods, with decrease in the load on each one. Since the blades move in opposite directions, the main cutting force is distributed over the components of the mechanism and transmitted to the motor. That decreases the load on the frame and the foundation in cutting. In opposing motion of the blades, cleavage of the metal occurs more rapidly. That permits concentration of the maximum force at the cut, with minimum load on the motor. The section removed from the metal does not travel under the roller at the end of cutting, and therefore no lower mobile table is required. The degree of mobility of the proposed mechanism is determined from the Chebyshev formula; its value is one. A special method is used for kinematic analysis of the blades; this method is based on the point of intersection of the connecting rods.

Realization Energy Optimization of Complete Path Planning in Differential Drive Based Self-Reconfigurable Floor Cleaning Robot

The efficiency of energy usage applied to robots that implement autonomous duties such as floor cleaning depends crucially on the adopted path planning strategies. Energy-aware for complete coverage path planning (CCPP) in the reconfigurable robots raises interesting research, since the ability to change the robot’s shape needs the dynamic estimate energy model. In this paper, a CCPP for a predefined workspace by a new floor cleaning platform (hTetro) which can self-reconfigure among seven tetromino shape by the cooperation of hinge-based four blocks with independent differential drive modules is proposed. To this end, the energy consumption is represented by travel distances which consider operations of differential drive modules of the hTetro kinematic designs to fulfill the transformation, orientation correction and translation actions during robot navigation processes from source waypoint to destination waypoint. The optimal trajectory connecting all pairs of waypoints on the workspace is modeled and solved by evolutionary algorithms of TSP such as Genetic Algorithm (GA) and Ant Optimization Colony (AC) which are among the well-known optimization approaches of TSP. The evaluations across several conventional complete coverage algorithms to prove that TSP-based proposed method is a practical energy-aware navigation sequencing strategy that can be implemented to our hTetro robot in different real-time workspaces. Moreover, The CCPP framework with its modulation in this paper allows the convenient implementation on other polynomial-based reconfigurable robots.

Design and analysis of robot for the maintenance of divertor in DEMO fusion reactor

The present paper introduces a remote robot solution for maintenance of divertor in DEMO fusion reactor. The task of the robot is to lift and extraction the divertor cassette within the vacuum vessel (VV) of DEMO. The kinematic design of the robot has been optimized for the DEMO access, inverse kinematics of the robot solution are introduced. A preliminary concept of the robot solution is built and the uninstallation of divertor cassette is illustrated. Main components are presented in detail and FE analysis of the main component of the solution is carried out.

Correction to: Kinematic design optimization for anthropomorphic robot hand based on interactivity of fingers

Correction to: Kinematic design optimization for anthropomorphic robot hand based on interactivity of fingers

Influence of tibiofemoral congruency design on the wear of patient-specific unicompartmental knee arthroplasty using finite element analysis.

ObjectivesUnicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty for patients who require treatment of single-compartment osteoarthritis, especially for young patients. To satisfy this requirement, new patient-specific prosthetic designs have been introduced. The patient-specific UKA is designed on the basis of data from preoperative medical images. In general, knee implant design with increased conformity has been developed to provide lower contact stress and reduced wear on the tibial insert compared with flat knee designs. The different tibiofemoral conformity may provide designers the opportunity to address both wear and kinematic design goals simultaneously. The aim of this study was to evaluate wear prediction with respect to tibiofemoral conformity design in patient-specific UKA under gait loading conditions by using a previously validated computational wear method.MethodsThree designs with different conformities were developed with the same femoral component: a flat design normally used in fixed-bearing UKA, a tibia plateau anatomy mimetic (AM) design, and an increased conforming design. We investigated the kinematics, contact stress, contact area, wear rate, and volumetric wear of the three different tibial insert designs.ResultsConforming increased design showed a lower contact stress and increased contact area. In addition, increased conformity resulted in a reduction of the wear rate and volumetric wear. However, the increased conformity design showed limited kinematics.ConclusionOur results indicated that increased conformity provided improvements in wear but resulted in limited kinematics. Therefore, increased conformity should be avoided in fixed-bearing patient-specific UKA design. We recommend a flat or plateau AM tibial insert design in patient-specific UKA.Cite this article: Y-G. Koh, K-M. Park, H-Y. Lee, K-T. Kang. Influence of tibiofemoral congruency design on the wear of patient-specific unicompartmental knee arthroplasty using finite element analysis. Bone Joint Res 2019;8:156–164. DOI: 10.1302/2046-3758.83.BJR-2018-0193.R1.

Kinematic design optimization for anthropomorphic robot hand based on interactivity of fingers

The human hand provides excellent grasp capabilities by using the interaction of the thumb and other fingers, and thus, how to dextrously interact with each other can represent the performance of the robot hand. This paper presents the kinematic design optimization for an anthropomorphic robot hand based on the interactivity of fingers. We propose a new performance index, called ‘interactivity of fingers (IF),’ which is useful for quantifying the multifingered precision grasping capability of the robot hand. Using the IF, the kinematic model of an anthropomorphic robot hand is optimized. The optimization is performed by using the genetic algorithm, and position and orientation of the thumb’s saddle joint are systematically determined. In order to verify the usefulness of the proposed performance index, IF of existing hands and that of the optimized model are compared. As a result, the IF of the optimized robot hand is almost five times larger than those of the other hands and the effectiveness of the proposed method is discussed.

Robust kinematics design of MacPherson suspension based on a double-loop multi-objective particle swarm optimization algorithm

In the traditional design of a vehicle suspension system, mechanical parameters, such as spring stiffness and tire radial stiffness, are determined before optimizing the coordinates of suspension hard-points based on handling and stability. However, the mechanical parameters of vehicle suspension systems vary with repeated changes in ambient temperature and loading conditions. Consequently, the original hard-point coordinates cannot guarantee satisfactory handling and stability after long-term vehicle use. To address this issue, an A0 class vehicle with a MacPherson suspension was modeled in ADAMS/Car and was validated against the results of field tests. The relationships between the maximum absolute values of front wheel alignment parameters during parallel wheel travel analysis and the coordinates of suspension hard-points, spring stiffness, and tire radial stiffness were determined using support vector regression. Next, a multi-objective optimization function was formulated based on the interval analysis method. Finally, a novel double-loop multi-objective particle swarm optimization algorithm was designed for global optimization of hard-point coordinates. The ADAMS simulation results indicated that, compared with the vehicle with the original hard-point coordinates, the double-loop multi-objective particle swarm optimization algorithm, the traditional multi-objective particle swarm optimization algorithm, and the genetic algorithm can effectively reduce the variation ranges of front wheel alignment parameters, regardless of the values of the mechanical parameters. It also showed that the double-loop multi-objective particle swarm optimization algorithm performs better than the traditional multi-objective particle swarm optimization and the genetic algorithm with both the original and changed mechanical parameters. Except for an increase in the variation range of the caster angle by 9.24–10.69%, the variation ranges of the toe angle, camber angle, and kingpin inclination angle under various mechanical parameters using the double-loop multi-objective particle swarm optimization algorithm were observed to be reduced by 50.45–79.39%, 1.84–4.24%, and 2.11–2.96%, respectively. Last but not least, the proposed double-loop multi-objective particle swarm optimization algorithm provided better handling, stability, and ride comfort values than the traditional multi-objective particle swarm optimization algorithm and the genetic algorithm.

Innovative Human-Like Dual Robotic Hand Mechatronic Design and its Chess-Playing Experiment

This paper describes how a standard HI-tech WINner Corporation articulated six degrees of freedom (DOFs) industrial robot arm and a National Taiwan University five-finger robotic hand was equipped with additional hardware and software to enable the resulting machine to play chess with a human chess player. For automatic interaction with the human player, moves were recorded by a webcam and automatically analyzed. No manual (keyboard) input was necessary. The chess-playing robotic system has been provided. An innovative humanoid robotic hand with 12 DOFs and 19 joints were designed, and distributed tactile sensor arrays with 376 detecting points on its surface were developed. The hand can communicate with the external through controller area networks bus. For performance evaluation of the designed robotic hand, we analyzed the workspace, intersection volume, and manipulability. First, several anatomical analyses were conducted prior to a decision on the kinematic design. Optimization procedures were then developed in this study to improve the parameters of the design and structure of the mechanism. The concepts of a series elastic actuator and an under-actuated mechanism were also employed to give the robotic hand a compliant property and high dexterity; hence, a humanoid robotic hand was devised. Since the robotic hand is as small and dexterous as a human hand, it can be conveniently used for a wide range of applications. Finally, the system has been proved to be executable in a complex environment.

Leader–Follower Formation Control of USVs With Prescribed Performance and Collision Avoidance

This paper addresses a decentralized leader–follower formation control problem for a group of fully actuated unmanned surface vehicles with prescribed performance and collision avoidance. The vehicles are subject to time-varying external disturbances, and the vehicle dynamics include both parametric uncertainties and uncertain nonlinear functions. The control objective is to make each vehicle follow its reference trajectory and avoid collision between each vehicle and its leader. We consider prescribed performance constraints, including transient and steady-state performance constraints, on formation tracking errors. In the kinematic design, we introduce the dynamic surface control technique to avoid the use of vehicle's acceleration. To compensate for the uncertainties and disturbances, we apply an adaptive control technique to estimate the uncertain parameters including the upper bounds of the disturbances and present neural network approximators to estimate uncertain nonlinear dynamics. Consequently, we design a decentralized adaptive formation controller that ensures uniformly ultimate boundedness of the closed-loop system with prescribed performance and avoids collision between each vehicle and its leader. Simulation results illustrate the effectiveness of the decentralized formation controller.

Fast modelling and simulation of the dynamic behaviour of a wet multidisc clutch during the engagement phase

In recent years multidisc wet friction clutches are of great importance to manufacturers of automatic transmissions (ATs) for the automotive industry, particularly since the introduction of double-clutched ATs. Their main advantage compared to their dry-friction counterparts is that they ensure smooth engagement, high reliability and long service life. Their progressive engagement due to the developed Couette flow between the discs enables them to be used both as clutches and as brakes in order to control power flow in simultaneously engaged geared shafts in the AT. Due to the coupled nature between the mechanical and the fluid dynamics regimes governing their operation, these systems are highly complex to be treated analytically and instead numerical approaches have proven to provide better results. However, the numerical treatment of such problems provides only case-specific results, which cannot be generalised and are not able to provide a general insight in the complex dynamics of the device. Furthermore the computational cost and the associated modelling and simulation effort during the design phase is high, making the incorporation of such methods in iterative design processes and algorithms counterproductive. In this paper the modelling of the dynamic behaviour of a wet multidisc clutch during the engagement phase is performed, via the combination of analytical and numerical methods and conclusions are drawn about the effect of the main geometric, kinematic and dynamic design parameters on the clutch’s response. The dynamic modelling is performed by applying the principle of linear and angular momentum on each disc. The effect of the fluid film is taken into account through the solution of the governing Navier-Stokes equations via CFD analysis or by the use of semi-analytical solutions with high accuracy, where applicable. Therefore both the developed pressure field and the torque of the fluid film are calculated efficiently and used in the simulation of the system. The flow is assumed to be laminar and the discs rigid and flat.

High-Gain Observer-Based Line-of-Sight Guidance for Adaptive Neural Path Following Control of Underactuated Marine Surface Vessels

This paper presents an adaptive neural network dynamic surface control law with time-varying sideslip compensation, which includes a geometric kinematic control design and a dynamic control design, for path following of underactuated marine surface vessels (MSVs) in the presence of unmeasured states, model uncertainties, unknown ocean environmental disturbances, and input saturation. First, a high gain observer based line-of-sight guidance law, capable of estimating and compensating the time-varying sideslip angle induced by the unknown time-varying ocean disturbances, is proposed to generate the desired heading for the dynamic control system of the MSV. Next, considering the input saturation, adaptive neural network dynamic surface velocity control laws, in which the model uncertainties and unknown ocean environmental disturbances of the system are compensated by adaptive radial basis function neural network and the problem of input saturation is solved by introducing auxiliary dynamic systems, are designed to realize the dynamic control target of the path following. The proposed control strategy of path following compensates the ocean environmental disturbances from the perspective of both the geometric kinematics and the dynamics, and all error signals of a closed-loop control system are proven to be uniformly ultimately bounded. The simulations validate the effectiveness of the proposed control strategy for path following of MSVs.

Повышение точности взвешивания сыпучих материалов на поточном расходомере-дозаторе с двумя тензометрическими датчиками

A weighing algorithm for an on-stream dispenser flow meter based on two strain gauges is developed and investigated. The main objectives are to achieve more accurate dosing of bulk materials and to prevent the influence of uneven material distribution along the weighing axis. Better dosing accuracy is achieved by installing strain gages on the material feeding side and using an intelligent conveyor belt speed control system, which is the main element in the developed weighing algorithm. The conveyor belt speed is adjusted by means of a fuzzy controller, because the controlled plant is a complex system, and the controllers synthesized according to the classical automatic control theory fail to meet the response speed requirements. The results from testing the selected kinematic design clearly show adequate performance of the fuzzy controller. Namely, when the feed of bulk material decreases, so does the conveyor belt speed, and vice versa. As a result, it becomes possible to decrease the relative measurement error to less than 0.5%. The developed device can be used in the food and agricultural-industrial complexes, in the civil construction, and chemical industries, and in other branches of the national economy, namely, in the processes involving metering and measuring the flow of bulk material in continuous technological processes. When used in combination with a feeder, on-stream flow meters can be used for high-precision weighted metering of various bulk materials. The product is supplied by a sluice or screw feeder, which can additionally be equipped with a smaller diameter screw for operation in rough/precise modes.

The possibility of cutting shapes on CNC machine tools

The development of computer technology has enabled it to be introduced to machine tools. The widespread use of CNC machine tools has resulted in a rapid development of the processing industry. So far, obtaining the profile of the curve has required the use of a complicated machine tool kinematic design, or it has been impossible to implement it otherwise than by copying. The numerical control of machine tools is based on the mathematical description of motion. This provides the capability to form curves of the same shape but with different dimensions using parametric programs. The article describes the practical use of parameters in machining on an FYS milling machine with Mitsubishi control.