Trajectory Planning with Minimum Synthesis Error for Industrial Robots Using Screw Theory

Zhifeng Liu,Jingjing Xu,Qiang Cheng,Yongsheng Zhao,Yanhu Pei,Congbin Yang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.2

This work aims to propose a trajectory planning technique to minimize the end-effector synthesis error for industrial robots, while obtaining a stable movement. With ER3A-C60 robot as a research subject, the kinematic and dynamic models are established by using screw theory and Kane equations, and based on that, the end-effector synthesis error is modeled by considering the effects of interpolation algorithm and flexibilities of all joints. The septic polynomial is used to interpolate the via points in each joint space to obtain a stable movement. Finally, the PSO algorithm with suitable parameters is applied to find the minimum synthesis error under kinematic and dynamic constraints. The results show that the optimal synthesis error decreases by 88.94% compared with the initial one, the angular parameters are all far less than the limitations of joints and the optimal movement has a high stability, and this optimal trajectory has better overall performance than that based on the previous technique (with the minimum total motion time). The main contribution is that the proposed trajectory planning technique can significantly improve the tracking precision of the end effector while controlling the motion time within a given span under the requirements of continuous path control.

Design Method of Active Disassembly Structure Triggered by Temperature-Pressure Coupling

Zhifeng Liu,Yifei Zhan,Huanbo Cheng,Xinyu Li,Shaobo Pan 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

Active disassembly products often use active disassembly structures triggered by single temperature or pressure field as reversible joints. These structures can be triggered automatically in extreme or accidental circumstances, thus causing the low reliability of products. For improving the reliability of active disassembly products, working mechanisms of active disassembly structure triggered by temperature-pressure coupling is presented in this article. Through analyzing some typical active disassembly structures, this article presents the design criteria and methods of active disassembly structure triggered by temperature-pressure coupling. The feasibility of these design methods is proved by a case analysis. The results of research shows that the reliability of active disassembly structures triggered by temperature-pressure coupling is improved greatly, which can lay the foundation for the industrial applications of active disassembly methods.

A structure-based approach to evaluation product adaptability in adaptable design

Qiang Cheng,Guojun Zhang,Zhifeng Liu,Peihua Gu,Ligang Cai 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.5

Adaptable design, as a new design paradigm, involves creating designs and products that can be easily changed to satisfy different requirements. In this paper, two types of product adaptability are proposed as essential adaptability and behavioral adaptability, and through measuring which respectively a model for product adaptability evaluation is developed. The essential adaptability evaluation proceeds with analyzing the independencies of function requirements and function modules firstly based on axiomatic design, and measuring the adaptability of interfaces secondly with three indices. The behavioral adaptability reflected by the performance of adaptable requirements after adaptation is measured based on Kano model. At last, the effectiveness of the proposed method is demonstrated by an illustrative example of the motherboard of a personal computer. The results show that the method can evaluate and reveal the adaptability of a product in essence, and is of directive significance to improving design and innovative design.

A Path Optimization Technique with Obstacle Avoidance for an 8-DOF Robot in Bolt Looseness Detection Task

Jingjing Xu,Zhifeng Liu,Yongsheng Zhao,Yanhu Pei,Qiang Cheng 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.5

In the bolt looseness detection task of the locomotive system, the robot could be used to highly improve the working efficiency and reliability, but faces the complex static obstacles while planning the path for the robotic motion. In this paper, a path optimization technique is proposed to obtain an optimal path with obstacle avoidance for a redundant robot in the static complicated environment. There are three main contributions in this technique. The first is the solving of the inverse kinematics problem for a redundant robot based on the screw theory and the geometric description, which is general to all robots with rotational joints. The second is the modeling of the spatial constraint, where the pseudo distance is defined based on the plane description of the obstacles and calculated using the spatial analytic geometry knowledge. The third is the presentation of the whole path-planning framework based on the above two contributions, which could largely improve the generality of the presented technique. In this framework, the minimum-time path could be obtained while guaranteeing both the motion stability and obstacle avoidance. Moreover, a real setting that includes an obstacle environment and an 8-DOF robot, is taken as an example to better present the technique. Finally, the simulation experiment was performed in Isight software to verify the effectiveness of the path optimization technique.

Experimental and Numerical Simulation Study on Mechanical Properties of Shallow Slope Root-soil Composite in Qinghai Area

Yuan Sun,Hui Li,Zhifeng Cheng,Jianpeng Dong,Yawei Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Natural disasters such as landslides often occur in Qinghai under the double deterioration ofearthquake and freeze-thaw cycles, ecological slope protection is an effective way to preventand control this type of disaster. In this paper, the mechanical properties of root-soilcomposites are investigated experimentally using triaxial apparatus and dynamic single shear(DSS) apparatus, and based on the discrete element method, a contact model more suitablefor reinforced soil materials is proposed to study the dynamic properties of root-soilcomposites under cyclic shear from a fine viewpoint. Based on the results of the study, thefollowing conclusions were drawn: 1) The presence of roots under the action of freeze-thawcycles increases the strength properties of the soil. At the same number of freeze-thaw cycles,the shear strength and cyclic resistance of the root-soil composites are higher than those of theloess. And the strength of the root-soil composites decreases with the increase of the numberof freeze-thaw cycles and then flattens out; 2) The proposed contact model can bettersimulate the softening effect of reinforced loess material under cyclic shear, which is moresuitable for simulating the mechanical behavior of loess and laying the foundation for furtherstudy of reinforced loess material from a fine viewpoint.; 3) The presence of the root systemwill improve the stability of the slope soil, and the root system will have a positive effect on theshear strength of the soil when the moisture content is within a certain range. The presence ofthe root system also increases the cyclic resistance of the soil. Under the same cyclic shearstress conditions, the number of damage cycles of the root-soil composites is higher than thatof the loess, the cumulative shear strain is less than that of the loess. However, the root systemno longer exerts positive effects under saturated conditions. The research results can providesome guidance for the construction of ecological slopes in loess areas, and provide a new wayto investigate the dynamic properties of root-soil composites from a fine viewpoint.

Analysis of the Partial Axial Load of a Very Thin-Walled Spur-Gear (Flexspline) of a Harmonic Drive

Congbin Yang,Qiushi Hu,Zhifeng Liu,Yongsheng Zhao,Qiang Cheng,Caixia Zhang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.7

Harmonic drives are the core components to enable movement in industrial robots. Unfortunately, the deformation of flexspline causes obvious partial axial load on gear engagement. This synthetic error leads to a series of additional problems, such as the deterioration of transmission quality, and the reduction of both precision and fatigue life. This study focuses on a harmonic drive with a double circular-arc tooth profile. A coordinate transformation is carried out based on the kinematics of harmonic drives. On this basis, the conjugate tooth profile of a circular spline is derived. A simulation model is developed based on the motion relationship for harmonic transmission. The effect of inhomogeneity of the load distribution on the surface of the gear teeth was investigated using the partial axial-load index. The effect of different factors on the partial axial load is analyzed. To reduce the effect of partial axial load of flexspline, we select a suitable material and wall thickness. For a certain practical range, both tooth width and chamfering of the flexspline teeth help reduce the partial axial load and increase the flexspline length. These conclusions enable improvements of future designs of reliable flexspline.

CFRP Reclamation and Remanufacturing Based on a Closed-loop Recycling Process for Carbon Fibers Using Supercritical N-butanol

Weihao Liu,Haihong Huang,Huanbo Cheng,Zhifeng Liu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.3

This study presents a closed-loop recycling process for carbon fibers using supercritical n-butanol. In thereclamation process, to achieve the highest composite recovery efficiency, the degradation of the carbon fiber-reinforcedepoxy resin composites was conducted at various experimental feedstock ratios (ratio of composite waste to n-butanol), thenthe reclaimed carbon fiber (RCF) was characterized using various methods to develop an understanding of the changes in theproperties and morphologies. In the remanufacturing process, in order to evaluate the reusability of the RCFs and thefeasibility of the closed-loop recycling process for carbon fibers, the RCFs were mixed with new epoxy resin andpolypropylene to remanufacture the composites, and then the mechanical properties of remanufacture composites weretested. The results show that, under an optimized process, the maximum recovery efficiency (feedstock ratio) of thecomposite was 0.1 g/ml. The impact of reclamation process on RCF lies in the degradation of tensile properties and theremoval of sizing agent, which leads the change of the interfacial bonding strength between RCF and new resin, andeventually results in an impact on the performance of remanufacture composites. Compared with the virgin carbon fiberreinforcedcomposites, the improvement in the RCF-reinforced polypropylene properties and insubstantial variations in thetensile properties of the RCF validate the potential of the closed-loop recycling process for carbon fibers.

Combined effect of carbonation and chloride ingress in concrete

Zhu, Xingji,Zi, Goangseup,Cao, Zhifeng,Cheng, Xudong Elsevier 2016 Construction and Building Materials Vol.110 No.-

<P><B>Abstract</B></P> <P>The combined effect of carbonation and chloride ingress in concrete is studied in this paper. Based on the change of the pore structure and the chemical equilibrium, a comprehensive model is proposed for this problem. A coupled simulation of the transports of carbon dioxide, chloride ions, heat and moisture is carried out. Several sets of experimental data were compared with the prediction by the numerical model developed in this paper, for its verification. Parametric study shows that the differences between the combined mechanism and the independent mechanisms are significant in many aspects.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A comprehensive model for the combined carbonation and chloride ingress in concrete is developed. </LI> <LI> The effect of CSH is directly considered for the estimation of the degree of carbonation. </LI> <LI> The changes of the pore structure and the binding capacity are considered for the combined action. </LI> <LI> The corrosion initiation can be accelerated significantly by the combined mechanism. </LI> </UL> </P>

Analysis and Optimization of an Internal Feedback Hydrostatic Turntable Oil Pad Power Consumption Based on Finite Difference Method

Congbin Yang,Shuaihua Shao,Yanhong Cheng,Zhifeng Liu,Yongsheng Zhao 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.12

The hydrostatic turntable is a critical component of numerous CNC machine tools, as it performs a supporting function and enables precise rotary motion. To ensure that high-precision CNC machines can operate under heavy loads, it is imperative to minimize power consumption. The power consumption of a hydrostatic turntable is affected by various factors, such as oil viscosity, initial oil film thickness, and oil pad structure. This study focuses on investigating a hydrostatic turntable with internal feedback. The Reynolds equation of the sector oil pad is solved using the finite difference method to establish the pressure distribution model. Subsequently, the study examines the power consumed by the axial oil pad at different initial oil film thickness, lubricating oil viscosity, and sealing edge width. To minimize power consumption caused by the axial oil pad, this paper employs the genetic algorithm to identify optimal design parameters within specified constraints. Additionally, the load-bearing performance of the optimized axial oil pad is checked to ensure that the load-bearing capacity and stiffness meet the requirements. Finally, the use of simulation software for oil pads in finite element simulation can preliminarily demonstrate the reliability of the proposed method.

Tangential Damping Model of Bolted Joint with the Physics-Based Friction Coefficient

Yongsheng Zhao,Hongchao Wu,Congbin Yang,Zhifeng Liu,Qiang Cheng 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.5

The stiff ness and damping modeling of joint surfaces are important for analyzing the dynamic characteristics of bolted joints, which has a great influence on the working precision of the machine tool. In this paper, a damping model is presented to predict the tangential damping of the joint accurately. The fractal theory is introduced to characterize the rough contact surface by using fractal dimension D and fractal roughness parameter G. For each micro-contact, the contact region can be divided into stick section and slip one. The energy dissipation of the micro-contact, which can be described as the tangential damping of bolted joint, emerges in the slip section. The physics-based friction coefficient is introduced to define the energy dissipation function based on the relationship between the deformation of micro-contact and the normal pressure. The energy dissipation factor and the proportional damping of the micro-contact can be obtained. The total tangential damping of bolted joint can be obtained by integrating the whole contact surfaces. Experimental set-up is designed to verify the proposed model. Compared with the constant friction coefficient damping model, the results show that the proposed model can more accurately describe the tangential damping of bolted joint.