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Velocity Constraints Based Approach for Online Trajectory Planning of High‑Speed Parallel Robots

Chinese Journal of Mechanical Engineering 2022年第6期35卷 98-109页

作者： Di Yang Fugui Xie xinjun liu State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China Beijing Key Lab of Precision/Ultra‑Precision Manufacturing Equipments and Control Tsinghua UniversityBeijing 100084China

High-speed parallel robots have been extensively utilized in the light industry.However,the influence of the nonlinear dynamic characteristics of high-speed parallel robots on system’s dynamic response and stable operation cannot be ignored during the high-speed reciprocating motion.Thus,trajectory planning is essential for efficiency and stability from pick-and-place(PAP)actions.This paper presents a method for planning the equal-height pick-and-place trajectory considering velocity constraints to improve the PAP efficiency and stability of high-speed parallel robots.The velocity constraints in the start-and-end points can reduce vibration from picking and placing,making the trajectory more suitable to complex beltline situations.Based on velocity constraints,trajectory optimization includes trajectory smoothness and joint torque to optimize cycle time is carried out.This paper proposes an online trajectory optimization solution.By using back propagation(BP)neural networks,the solution is simplified and can be solved in real-time.Simulation and experiments were carried out on the SR4 parallel robot.The results show that the proposed method improves the efficiency,smoothness,and stability of the robot.This paper proposes an online trajectory planning method which is velocity constraints based and can improve the efficiency and stability of high-speed parallel robots.The work of this research is conducive to finely applying high-speed parallel robots.

关键词： Trajectory planning High-speed parallel robot Velocity constraints BP neural network

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Evolution and Development Trend Prospect of Metal Milling Equipment

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Chinese Journal of Mechanical Engineering 2023年第2期36卷 1-15页

作者： Jie Wen Fugui Xie xinjun liu Yi Yue Department of Mechanical Engineering(DME) Tsinghua UniversityBeijing 100084China Beijing Key Lab of Precision/Ultra‑Precision Manufacturing Equipments and Control Tsinghua UniversityBeijing 100084China Beijing Spacecrafts Beijing 100094China

The world is currently undergoing profound changes which have never happened within the past century.Global competition in the technology and industry fields is becoming increasingly fierce.The strategic competition of the major powers further focuses on the manufacturing industry.Developed countries such as the United States,Germany,and Japan have successively put forward strategic plans such as“re-industrialization”and“return of manufacturing industry”,aiming to seize the commanding heights of a new round of global high-end technology competition and expand international market share.Standing at the historic intersection of a new round of scientific and technological revolution and China's accelerated high-quality development,the“14th Five-Year Plan”clearly pointed out that intelligent manufacturing is the main development trend to promote China's manufacturing to the medium-high end of the global value chain.This reflects the importance of advanced manufacturing for national strategic layout.To better grasp the development direction of advanced manufacturing equipment,the development process and current application status of manufacturing equipment are summarized,and thereafter the characteristics of manufacturing equipment in different development stages of the manufacturing industry are analyzed.Finally,the development trend of advanced milling equipment is prospected.

关键词： Intelligent manufacturing High-quality development Milling equipment Evolution and development trend

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A Novel 6‑DOF Force‑Sensed Human‑Robot Interface for an Intuitive Teleoperation

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Chinese Journal of Mechanical Engineering 2022年第6期35卷 76-88页

作者： Zihao Li Fugui Xie Yanlei Ye Peng Li xinjun liu State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China Beijing Key Lab of Precision/Ultra‑Precision Manufacturing Equipments and Control Tsinghua UniversityBeijing 100084China

The teleoperation of a 6 degrees-of-freedom(DOF)manipulator is one of the basic methods to extend people’s capabilities in the wide variety of applications.The master interface based on the force/torque(FT)sensor could provide the full-dimension intuitive teleoperation of a 6-DOF robot since it has the ability to trigger 6-DOF command input.However,due to the force coupling,noise disturbance and unlimited input signals of the FT sensor,this force-sensed interface could not be widely used in practice.In this paper,we present an intuitive teleoperation method based on the FT sensor to overcome these challenges.In this method,the input signals from the force-sensed joystick were filtered and then processed to the force commands by force limit algorithm,with the merits of anti-interference,output limitation,and online velocity adjustment.Furthermore,based on the admittance control and position controller,the manipulator could be teleoperated by the force commands.Three experiments were conducted on our self-designed robotic system.The result of the first experiment shows that the interfered force from the force coupling could be effectively suppressed with the limitation of the input force through force limit algorithm.Then,a parameter was introduced in the other two experiments to adjust the velocity online practically with force limit algorithm.The proposed method could give a practical solution to the intuitive teleoperation based on the FT sensor.

关键词： Force-sensed interface Haptic control Force coupling Teleoperation Human-robot interaction

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A Real-time Look-ahead Trajectory Planning Methodology for Multi Small Line Segments Path

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Chinese Journal of Mechanical Engineering 2023年第3期36卷 76-88页

作者： Sai Zhang xinjun liu Bingkai Yan Jie Bi Xiangdong Han Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Robotphoenix Automation Technology Co. Ltd.Jinan 250100China

When a robot is required to machine a complex curved workpiece with high precision and speed,the tool path is typically dispersed into a series of points and transmitted to the robot.The conventional trajectory planning method requires frequent starts and stops at each dispersed point to complete the task.This method not only reduces precision but also causes damage to the motors and robot.A real-time look-ahead algorithm is proposed in this paper to improve precision and minimize damage.The proposed algorithm includes a path-smoothing algorithm,a trajectory planning method,and a bidirectional scanning module.The path-smoothing method inserts a quintic Bezier curve between small adjacent line segments to achieve G^(2)continuity at the junctions.The trajectory planning method utilizes a quartic polynomial and a double-quartic polynomial that can achieve a constant velocity at the velocity limitation.The bidirectional scanning module calculates the velocity at each trajectory planning segment point,simplifying calculation complexity and can be run in real time.The feasibility of the proposed algorithm is verified through simulations and experiments,which can be run in real time.In addition,high machining precision can be achieved by adjusting the relevant parameters.

关键词： Look-ahead Bidirectional scanning Transition scheme Bezier curve G^(2)continuity

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ROS2 Real-time Performance Optimization and Evaluation

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Chinese Journal of Mechanical Engineering 2023年第6期36卷 36-50页

作者： Yanlei Ye Zhenguo Nie xinjun liu Fugui Xie Zihao Li Peng Li State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipments and Control Tsinghua UniversityBeijing 100084China

Real-time interaction with uncertain and dynamic environments is essential for robotic systems to achieve functions such as visual perception,force interaction,spatial obstacle avoidance,and motion planning.To ensure the reliability and determinism of system execution,a flexible real-time control system architecture and interaction algorithm are required.The ROS framework was designed to improve the reusability of robotic software development by providing a distributed structure,hardware abstraction,message-passing mechanism,and application prototypes.Rich ecosystems for robotic development have been built around ROS1 and ROS2 architectures based on the Linux system.However,because of the fairness scheduling principle of the default Linux system design and the complexity of the kernel,the system does not have real-time computing.To achieve a balance between real-time and non-real-time computing,this paper uses the transmission mechanism of ROS2,combines it with the scheduling mechanism of the Linux operating system,and uses Preempt_RT to enhance the real-time computing of ROS1 and ROS2.The real-time performance evaluation of ROS1 and ROS2 is conducted from multiple perspectives,including throughput,transmission mode,QoS service quality,frequency,number of subscription nodes and EtherCAT master.This paper makes two significant contributions:firstly,it employs Preempt_RT to optimize the native ROS2 system,effectively enhancing the real-time performance of native ROS2 message transmission;secondly,it conducts a comprehensive evaluation of the real-time performance of both native and optimized ROS2 systems.This comparison elucidates the benefits of the optimized ROS2 architecture regarding real-time performance,with results vividly demonstrated through illustrative figures.

关键词： ROS Real-time system optimization Preempt_RT Real-time performance evaluation of ROS2

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Research on the Structural Rigidity Characteristics of a Reconfigurable TBM Thrust Mechanism

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Chinese Journal of Mechanical Engineering 2019年第6期32卷 35-47页

作者： Younan Xu xinjun liu Jiyu Xu School of Mechantronics and vehicle Engineering East China Jiaotong UniversityNanchang 330013China Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China Department of Mechanical Engineering and Aerospace Polytechnic of TorinTorin 10135Italy

To improve the adaptability of TBMs in diverse geological environments,this paper proposes a reconfigurable Type-V thrust mechanism(V-TM)with rearrangeable working states,in which structural stiffness can be automatically altered during operation.Therefore,millions of configurations can be obtained,and thousands of instances of working status per configuration can be set respectively.Nonetheless,the complexity of configurations and diversity of working states contributes to further complications for the structural stiffness algorithm.This results in challenges such as difficulty calculating the payload compliance index and the environment adaptability index.To solve this problem,we use the configuration matrix to describe the relationship between propelling jacks under reconfiguration and adopt pattern vectors to describe the working state of each hydraulic cylinder.Then,both the dynamic compatible equation between propeller forces of the hydraulic cylinders and driving forces,and the kinematic harmonizing equation between the hydraulic cylinder displacements and their deformations are established.Next,we derive the stiffness analytical equation using Hooke’s law and the Jacobian Matrix.The proposed approach provides an effective algorithm to support structural rigidity analysis,and lays a solid theoretical foundation for calculating the performance indexes of the V-TM.We then analyze the rigidity characteristics of typical configurations under different working states,and obtain the main factors affecting structural stiffness of the V-TM.The results show the deviation degree of structural parameters in hydraulic cylinders within the same group,and the working status of propelling jacks.Finally,our constructive conclusions contribute valuable information for matching and optimization by drawing on the factors that affect the structural rigidity of the V-TM.

关键词： Reconfigurable TBM thrust mechanism,Structural rigidity characteristics Configuration matrix Patternvector Kinematic harmonizing equation Dynamic compatible equation Structural stiffness equations

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Optimal design of a new spatial 3-DOF parallel robot with respect to a frame-free index

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Science China(Technological Sciences) 2009年第4期52卷 986-999页

作者： JinSong Wang xinjun liu Chao Wu Department of Precision Instruments Tsinghua University Beijing 100084 China

Optimal design is one of the most important issues in robots. Since the very beginning, the concepts of the Jacobian matrix, manipulability and condition number, which are used successfully in the field of serial robots, have been applied to parallel robots. Unlike serial robots, parallel robots are good for motion/force transmission. Their performance evaluation and design should be correspondingly dif- ferent. This paper is an attempt to optimally design a novel spatial three-degree-of-freedom (3-DOF) parallel robot by using the concept of motion/force transmission. Accordingly, three indices are defined. The suggested indices are independent of any coordinate frame and could be applied to the analysis and design of a parallel robot whose singularities can be identified wholly by using the relative angle between the output and adjacent links, and by using the relative angle between the input and adjacent links.

关键词： optimal design parallel robots index transmission angle motion/force transmission

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气候变化对西南大西洋渔业生态系统的影响研究进展

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上海海洋大学学报 2024年第1期33卷 211-229页

作者：余为刘赫威陈新军上海海洋大学海洋科学学院上海201306 国家远洋渔业工程技术研究中心上海201306 大洋渔业资源可持续开发教育部重点实验室上海201306 农业农村部大洋渔业开发重点实验室上海201306 农业农村部大洋渔业资源环境科学观测实验站上海201306

西南大西洋是世界重要的渔区,捕捞国家包括阿根廷等西南大西洋沿海国以及中国、日本等众多非沿海国家。阿根廷滑柔鱼(Illex argentinus)、阿根廷无须鳕(Merluccius hubbsi)、巴西小沙丁鱼(Sardinella brasiliensis)与弗氏绒须石首鱼(Mic... 详细信息

西南大西洋是世界重要的渔区,捕捞国家包括阿根廷等西南大西洋沿海国以及中国、日本等众多非沿海国家。阿根廷滑柔鱼(Illex argentinus)、阿根廷无须鳕(Merluccius hubbsi)、巴西小沙丁鱼(Sardinella brasiliensis)与弗氏绒须石首鱼(Micropogonias furnieri)是西南大西洋年产量最高的4种主要经济渔获物。探究气候变化对西南大西洋生态系统的影响有利于建立基于生态系统的渔业资源保护与利用对策。本文从渔业资源与生态系统两个角度出发,分别归纳了生态系统的生物因子(主要经济渔获物)、非生物因子(环境因素)与营养结构(食物链和食物网)对气候变化的响应情况。总结发现,气候变化会影响环境的变化,并对生态系统的渔业资源及营养结构产生影响。分析认为,在今后探究西南大西洋生态系统对气候变化响应的研究中,选取代表物种表征生态系统的变化,并结合人类活动与气候变化的影响可以丰富生态系统研究的相关结论,为西南大西洋提供基于生态系统的科学管理策略。

关键词：西南大西洋渔业生态系统气候变化经济渔获物食物网

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机器人化装备测量-加工一体化技术现状及展望

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机器人 2024年第1期46卷 118-128页

作者：王卓群谢福贵解增辉刘辛军清华大学机械工程系北京100084 清华大学精密超精密制造装备及控制北京市重点实验室北京100084

面对非结构化的加工场景以及多品种小批量复杂构件的定制化加工需求,机器人化装备需具备感知待加工件和加工场景的能力,对测量技术与加工技术的深度融合需求迫切,但目前尚无成熟的技术体系。本文围绕测量-加工一体化技术所涉及的测量数... 详细信息

面对非结构化的加工场景以及多品种小批量复杂构件的定制化加工需求,机器人化装备需具备感知待加工件和加工场景的能力,对测量技术与加工技术的深度融合需求迫切,但目前尚无成熟的技术体系。本文围绕测量-加工一体化技术所涉及的测量数据获取、加工特征提取、加工方案生成和末端闭环控制4项关键技术进行综述,总结了测量-加工一体化技术的现状与面临的技术挑战,对测量-加工一体化技术在构建跨尺度测量场、优化数据驱动方式、集成多功能测量、拓展智能化应用等方面的发展趋势进行了分析和探讨。

关键词：测量-加工一体化机器人化装备智能化加工跨尺度测量

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Optimal Design and Force Control of a Nine-Cable-Driven Parallel Mechanism for Lunar Takeoff Simulation

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 35-46页

作者： Wangmin Yi Yu Zheng Weifang Wang XiaoqiangTang xinjun liu Fanwei Meng Department of Mechanical Engineering Tsinghua University Beijing 100084China Beijing Institute of Spacecraft EnvironMent Engineering China Academy of Space Technology Beijing 100094 China Beijing Engineering Research Center of the Intelligent AsseMbly Technology and EquipMent for Aerospace Product Beijing Institute of Spacecraft EnvironMent Engineering Beijing 100094China School of Mechanical Engineering and AutoMation Beihang University Beijing 100191China Beijing Institute of Radio MeasureMent Second Research Institute of the China Aerospace Science and Industry Group Beijing 100854 China

Traditional simulation methods are unable to meet the requirements of lunar takeo simulations, such as high force output precision, low cost, and repeated use. Considering that cable-driven parallel mechanisms have the advantages of high payload to weight ratio, potentially large workspace, and high-speed motion, these mechanisms have the potential to be used for lunar takeo simulations. Thus, this paper presents a parallel mechanism driven by nine cables. The purpose of this study is to optimize the dimensions of the cable-driven parallel mechanism to meet dynamic workspace requirements under cable tension constraints. The dynamic workspace requirements are derived from the kinematical function requests of the lunar takeo simulation equipment. Experimental design and response surface methods are adopted for building the surrogate mathematical model linking the optimal variables and the optimization indices. A set of dimensional parameters are determined by analyzing the surrogate mathematical model. The volume of the dynamic workspace increased by 46% after optimization. Besides, a force control method is proposed for calculating output vector and sinusoidal forces. A force control loop is introduced into the traditional position control loop to adjust the cable force precisely, while controlling the cable length. The e ectiveness of the proposed control method is verified through experiments. A 5% vector output accuracy and 12 Hz undulation force output can be realized. This paper proposes a cable-driven parallel mechanism which can be used for lunar takeo simulation.

关键词： Force control Lunar takeoff simulation Parallel robots Surrogate mathematical model

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