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.

H∞ CONTROL FOR BATTERY/SUPERCAPACITOR HYBRID ENERGY STORAGE SYSTEM USED IN ELECTRIC VEHICLES

Zhifeng Bai,Zengfeng Yan,Xiaolan Wu,Jun Xu,Binggang Cao 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.6

This paper proposes a control strategy of a hybrid energy storage system (HESS) based on simplified 2th-order model. The HESS uses a bidirectional DC/DC converter to connect the supercapacitors (SC) with the battery. Two control objectives, the output current of the SC during the traction procedure and the charging current of the SC while regenerative braking, are regulated by using the DC/DC converter. Two H∞ controllers are designed to control the output and charging current of the SC to their reference values, which are generated by the energy management strategy (EMS). Experimental results show that the proposed control method achieves a satisfactory performance, including a low steady-state tracking error and high response speed when the load power varies in a wide range.

A Learning Control Strategy for Robot-assisted Bathing via Impedance Sliding Mode Technique With Non-repetitive Tasks

Yuexuan Xu,Xin Guo,Bokai Xuan,Hao Sun,Gaowei Zhang,Jian Li,Xingyu Huo,Zhifeng Gu 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.3

This paper investigates an impedance-based iterative learning sliding mode control scheme for robotassisted bathing, taking into consideration scenarios with unknown model parameters. Initially, the utilization ofimpedance control is not confined to merely adjusting the desired trajectory but is also instrumental in ensuringactive compliance control during the robot-assisted bathing procedure. Furthermore, an iterative learning control(ILC) is devised to estimate the iteration-invariant dynamic parameters, which are intricate and challenging to precisely ascertain in practical applications. To mitigate the effect of divergent initial conditions in ILC, a trajectoryreconstruction method is introduced, thus ensuring the convergence of tracking errors even when starting from random initial states. Moreover, an adaptive sliding mode control mechanism is proposed to counteract non-parametricexternal disturbances and the torque generated through human-machine interaction during the bathing process. Theconvergence of the double closed-loop system in both the time and iterative domains is demonstrated through theapplication of the composite energy function method. Eventually, the efficacy and superiority of the control strategyoutlined in this paper are jointly verified through co-simulation employing MATLAB and ADAMS.

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.

Simulation of particulate matter movement characteristics in multiphase flow field system

Zhangliang Xu,Zhifeng Li,Maochuan Sun 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.8

An innovative separation system based on dielectric electrophoresis (DEP-on-achip system) is proposed to separate different particulate matters. A discrete phase model (DPM) and coupling model was utilized to simulate the movement characteristics in liquid-solid two phase flows and gas-liquid-solid three phase flows, respectively. In liquid-solid fluid systems, the effect of the liquid viscosity and density on the movement displacement of particles was studied. In gas-liquid-solid fluid systems, the effect of physical parameters, such as inlet velocity, liquid viscosity, liquid density and surface tension force, on the trajectory of PM2.5 (particulate matter 2.5) and PM10 was discussed. Conclusively, the theoretical separation time of the DEP-on-a-chip system is successfully achieved at the second level. The optimized physical parameters with the inlet velocity around 1.0 m/s, the liquid viscosity of 1×10 -5 Pa·s, the liquid density of 1500 kg/m 3 and the surface tension of 0.065 N/m for the separation system are established.

Energy-Efficient Algorithm for Assigning Verification Tasks in Cloud Storage

( Guangwei Xu ),( Zhifeng Sun ),( Cairong Yan ),( Xiujin Shi ),( Yue Li ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

Mobile Cloud Computing has become a promising computing platform. It moves users` data to the centralized large data centers for users` mobile devices to conveniently access. Since the data storage service may not be fully trusted, many public verification algorithms are proposed to check the data integrity. However, these algorithms hardly consider the huge computational burden for the verifiers with resource-constrained mobile devices to execute the verification tasks. We propose an energy-efficient algorithm for assigning verification tasks (EEAVT) to optimize the energy consumption and assign the verification tasks by elastic and customizable ways. The algorithm prioritizes verification tasks according to the expected finish time of the verification, and assigns the number of checked blocks referring to devices` residual energy and available operation time. Theoretical analysis and experiment evaluation show that our algorithm not only shortens the verification finish time, but also decreases energy consumption, thus improving the efficiency and reliability of the verification.

Synthesis of CNx nanocrystals and nanotubes on Co/Ni-covered substrate by nitrogen-atom-beam-assisted pulsed laser ablation

Ning Xu,Aimin Wu,Fuming Li,Hao Lin,Jiada Wu,Peinan Wang,Yuancheng Du,Zhifeng Ying 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.32

CNx nanocrystals and nanotubes were synthesized on Co/Ni-covered Si(100) wafers using a nitrogen-atom-beam-assisted pulsed laser ablation deposition method. Transimission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy showed that nanometer-sized CNx nanocrystals and nanotubes were contained in the as-deposited lms. The co-catalyzation by the cobalt and nickel in the synthesis process is considered to play an important role in the formation of CNx nanocrystals and nanotubes. The reasons for the formation of CNx nanocrystals and nanotubes have been analyzed.

Novel multiple-acidic ionic liquids: Green and efficient catalysts for the synthesis of bis-indolylmethanes under solvent-free conditions

Anguo Ying,Zhifeng Li,Yuxiang Ni,Songlin Xu,Hailiang Hou,Huanan Hu 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.24 No.-

Four novel multiple-acidic ionic liquids based on triethanolamine (TEA) were prepared and used as efficient catalysts to synthesize bis-indolylmethanes at room temperature without any organic solvent. [TEOA][HSO4] showed the best catalytic performance. The optimal amount of catalyst was 10 mol%. Various aldehydes/ketones reacted with indole/substituted indole smoothly and afforded to corresponding products in 70–99% yields within minutes. Additionally, the ionic liquid could be reused up to five times with only a slight decrease in catalytic activity. Finally, a possible reaction mechanism was given. Techniques of acidity test and NMR were introduced to verify the proposed mechanism.

Effects of Diamines on the Optical Properties of Poly(ether imide)s Derived from 2,2-Bis[4-(3,4-dicarboxyphenoxy)phenyl]propane Dianhydride (BPADA)

Linshuang Li,Yong Xu,Jianfei Che,Xiaohong Liu,Wei Zhao,Zhifeng Ye 한국고분자학회 2019 Macromolecular Research Vol.27 No.9

The objective of this study was to investigate the effects of diamines with ether group or/and trifluoromethyl (-CF3) group on the optical properties of polyimides. A series of poly(ether imide)s (PEIs) (III) were prepared from 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA) with various aromatic diamines (Ia-h) including non-fluorinated diamines (Ia-d) and the corresponding trifluoromethyl-substituted diamines (Ie-h). The fluorinated PEIs IIIe-h based on fluorinated diamines were nearly colorless with cutoff absorption wavelength (λ0) below 370 nm and with solubility higher than that of the corresponding CF3-free analogues (IIIa-d). Meanwhile, they had lower dielectric constants in the range of 2.91-3.21 at 1 MHz coupled with water absorptions below 0.70% and contact angles against water beyond 108o. The III series had tensile strength of 84.3-94.4 MPa, modulus of elasticity of 3.6-8.9 GPa and elongation at break of 9.4-25.3%, together with temperatures of 5% weight loss (T5%) beyond 510 °C. Compared to the IV series based on 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the corresponding III series exhibited better thermal and mechanical properties coupled with good optical properties, especially the fluorinated PEIs IIIe-h.

Contact Stiffness Determination of High-Speed Double- Locking Toolholder-Spindle Joint based on a Macro- Micro Scale Hybrid Method

Yongsheng Zhao,Jingjing Xu,Ligang Cai,Weimin Shi,Zhifeng Liu,Qiang Cheng 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.6

The stiffness of toolholder-spindle joint at high speeds plays an important role in the cutting efficiency and the machining accuracy. A double-locking toolholder (BTF type) is designed to improve the stiffness of joint. This paper presents a macro-micro scale hybrid method to determine the stiffness of double-locking toolholder-spindle joint at high speeds. In this method the finite element method and the three-dimensional fractal method are combined. It is assumed flat in macro-scale for the contact surfaces of joint. The finite element method is introduced to obtain the pressure distribution with the influence of centrifugal force at high speeds. In micro-scale, the contact surfaces are fractal featured and the three-dimensional fractal method is used to compute the stiffness based on the pressure. Experiments with BTF40-type toolholder are conducted to verify the efficiency of the proposed model in zero-speed case. The relationship between the stiffness and the technological parameters of the system can be derived based on the presented model. The upper limit of speed, the optimized range of each technological parameter are determined for obtaining the higher stiffness of joint. The results can provide theoretical basis for improving the cutting efficiency and the machining accuracy of high-speed machine tool.