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Article
Publication date: 18 January 2021

Hongxing Wang, LianZheng Ge, Ruifeng Li, Yunfeng Gao and Chuqing Cao

An optimal solution method based on 2-norm is proposed in this study to solve the inverse kinematics multiple-solution problem caused by a high redundancy. The current…

Abstract

Purpose

An optimal solution method based on 2-norm is proposed in this study to solve the inverse kinematics multiple-solution problem caused by a high redundancy. The current research also presents a motion optimization based on the 2-Norm of high-redundant mobile humanoid robots, in which a kinematic model is designed through the entire modeling.

Design/methodology/approach

The current study designs a highly redundant humanoid mobile robot with a differential mobile platform. The high-redundancy mobile humanoid robot consists of three modular parts (differential driving platform with two degrees of freedom (DOF), namely, left and right arms with seven DOF, respectively) and has total of 14 DOFs. Given the high redundancy of humanoid mobile robot, a kinematic model is designed through the entire modeling and an optimal solution extraction method based on 2-norm is proposed to solve the inverse kinematics multiple solutions problem. That is, the 2-norm of the angle difference before and after rotation is used as the shortest stroke index to select the optimal solution. The optimal solution of the inverse kinematics equation in the step is obtained by solving the minimum value of the objective function of a step. Through the step-by-step cycle in the entire tracking process, the kinematic optimization of the highly redundant humanoid robot in the entire tracking process is realized.

Findings

Compared with the before and after motion optimizations based on the 2-norm algorithm of the robot, its motion after optimization shows minimal fluctuation, improved smoothness, limited energy consumption and short path during the entire mobile tracking and operating process.

Research limitations/implications

In this paper, the whole kinematics model of the highly redundant humanoid mobile robot is established and its motion is optimized based on 2-norm, which provides a theoretical basis for the follow-up research of the service robot.

Practical implications

In this paper, the whole kinematics model of the highly redundant humanoid mobile robot is established and its motion is optimized based on 2-norm, which provides a theoretical basis for the follow-up research of the service robot.

Social implications

In this paper, the whole kinematics model of the highly redundant humanoid mobile robot is established and its motion is optimized based on 2-norm, which provides a theoretical basis for the follow-up research of the service robot.

Originality/value

Motion optimization based on the 2-norm of a highly redundant humanoid mobile robot with the entire modeling is performed on the basis of the entire modeling. This motion optimization can make the highly redundant humanoid mobile robot’s motion path considerably short, minimize energy loss and shorten time. These researches provide a theoretical basis for the follow-up research of the service robot, including tracking and operating target, etc. Finally, the motion optimization algorithm is verified by the tracking and operating behaviors of the robot and an example.

Details

Assembly Automation, vol. 41 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 9 April 2021

Jinlei Zhuang, Ruifeng Li, Chuqing Cao, Yunfeng Gao, Ke Wang and Feiyang Wang

This paper aims to propose a measurement principle and a calibration method of measurement system integrated with serial robot and 3D camera to identify its parameters…

Abstract

Purpose

This paper aims to propose a measurement principle and a calibration method of measurement system integrated with serial robot and 3D camera to identify its parameters conveniently and achieve high measurement accuracy.

Design/methodology/approach

A stiffness and kinematic measurement principle of the integrated system is proposed, which considers the influence of robot weight and load weight on measurement accuracy. Then an error model is derived based on the principle that the coordinate of sphere center is invariant, which can simultaneously identify the parameters of joint stiffness, kinematic and hand-eye relationship. Further, considering the errors of the parameters to be calibrated and the measurement error of 3D camera, a method to generate calibration observation data is proposed to validate both calibration accuracy and parameter identification accuracy of calibration method.

Findings

Comparative simulations and experiments of conventional kinematic calibration method and the stiffness and kinematic calibration method proposed in this paper are conducted. The results of the simulations show that the proposed method is more accurate, and the identified values of angle parameters in modified Denavit and Hartenberg model are closer to their real values. Compared with the conventional calibration method in experiments, the proposed method decreases the maximum and mean errors by 19.9% and 13.4%, respectively.

Originality/value

A new measurement principle and a novel calibration method are proposed. The proposed method can simultaneously identify joint stiffness, kinematic and hand-eye parameters and obtain not only higher measurement accuracy but also higher parameter identification accuracy, which is suitable for on-site calibration.

Details

Industrial Robot: the international journal of robotics research and application, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 15 May 2020

Feifei Bian, Danmei Ren, Ruifeng Li, Peidong Liang, Ke Wang and Lijun Zhao

The purpose of this paper is to enable robots to intelligently adapt their damping characteristics and motions in a reactive fashion toward human inputs and task…

Abstract

Purpose

The purpose of this paper is to enable robots to intelligently adapt their damping characteristics and motions in a reactive fashion toward human inputs and task requirements during physical human–robot interaction.

Design/methodology/approach

This paper exploits a combination of the dynamical system and the admittance model to create robot behaviors. The reference trajectories are generated by dynamical systems while the admittance control enables robots to compliantly follow the reference trajectories. To determine how control is divided between the two models, a collaborative arbitration algorithm is presented to change their contributions to the robot motion based on the contact forces. In addition, the authors investigate to model the robot’s impedance characteristics as a function of the task requirements and build a novel artificial damping field (ADF) to represent the virtual damping at arbitrary robot states.

Findings

The authors evaluate their methods through experiments on an UR10 robot. The result shows promising performances for the robot to achieve complex tasks in collaboration with human partners.

Originality/value

The proposed method extends the dynamical system approach with an admittance control law to allow a robot motion being adjusted in real time. Besides, the authors propose a novel ADF method to model the robot’s impedance characteristics as a function of the task requirements.

Details

Industrial Robot: the international journal of robotics research and application, vol. 47 no. 4
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 30 October 2018

Feifei Bian, Danmei Ren, Ruifeng Li and Peidong Liang

The purpose of this paper is to eliminate instability which may occur when a human stiffens his arms in physical human–robot interaction by estimating the human hand…

Abstract

Purpose

The purpose of this paper is to eliminate instability which may occur when a human stiffens his arms in physical human–robot interaction by estimating the human hand stiffness and presenting a modified vibration index.

Design/methodology/approach

Human hand stiffness is first estimated in real time as a prior indicator of instability by capturing the arm configuration and modeling the level of muscle co-contraction in the human’s arms. A time-domain vibration index based on the interaction force is then modified to reduce the delay in instability detection. The instability is confirmed when the vibration index exceeds a given threshold. The virtual damping coefficient in admittance controller is adjusted accordingly to ensure stability in physical human–robot interaction.

Findings

By estimating the human hand stiffness and modifying the vibration index, the instability which may occur in stiff environment in physical human–robot interaction is detected and eliminated, and the time delay is reduced. The experimental results demonstrate significant improvement in stabilizing the system when the human operator stiffens his arms.

Originality/value

The originality is in estimating the human hand stiffness online as a prior indicator of instability by capturing the arm configuration and modeling the level of muscle co-contraction in the human’s arms. A modification of the vibration index is also an originality to reduce the time delay of instability detection.

Details

Industrial Robot: the international journal of robotics research and application, vol. 46 no. 4
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 4 April 2016

Fei Yan, Ke Wang, Jizhong Xiao and Ruifeng Li

The most prominent example of scan matching algorithm is the Iterative Closest Point (ICP) algorithm. But the ICP algorithm and its variants excessively depend on the…

Abstract

Purpose

The most prominent example of scan matching algorithm is the Iterative Closest Point (ICP) algorithm. But the ICP algorithm and its variants excessively depend on the initial pose estimate between two scans. The purpose of this paper is to propose a scan matching algorithm, which is adaptable to big initial pose errors.

Design/methodology/approach

The environments are represented by flat units and upright units. The upright units are clustered to represent objects that the robot cannot cross over. The object cluster is further discretized to generate layered model consisting of cross-section ellipses. The layered model provides simplified features that facilitate an object recognition algorithm to discriminate among common objects in outdoor environments. A layered model graph is constructed with the recognized objects as nodes. Based on the similarity of sub-graphs in each scans, the layered model graph-based matching algorithm generates initial pose estimates and uses ICP to refine the scan matching results.

Findings

Experimental results indicate that the proposed algorithm can deal with bad initial pose estimates and increase the processing speed. Its computation time is short enough for real-time implementation in robotic applications in outdoor environments.

Originality/value

This paper proposes a bio-inspired scan matching algorithm for mobile robots based on layered model graph in outdoor environments.

Details

Assembly Automation, vol. 36 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 16 October 2017

LianZheng Ge, Jian Chen, Ruifeng Li and Peidong Liang

The global performance of industrial robots partly depends on the properties of drive system consisting of motor inertia, gearbox inertia, etc. This paper aims to deal…

Abstract

Purpose

The global performance of industrial robots partly depends on the properties of drive system consisting of motor inertia, gearbox inertia, etc. This paper aims to deal with the problem of optimization of global dynamic performance for robotic drive system selected from available components.

Design/methodology/approach

Considering the performance specifications of drive system, an optimization model whose objective function is composed of working efficiency and natural frequency of robots is proposed. Meanwhile, constraints including the rated and peak torque of motor, lifetime of gearbox and light-weight were taken into account. Furthermore, the mapping relationship between discrete optimal design variables and component properties of drive system were presented. The optimization problem with mixed integer variables was solved by a mixed integer-laplace crossover power mutation algorithm.

Findings

The optimization results show that our optimization model and methods are applicable, and the performances are also greatly promoted without sacrificing any constraints of drive system. Besides, the model fits the overall performance well with respect to light-weight ratio, safety, cost reduction and others.

Practical implications

The proposed drive system optimization method has been used for a 4-DOF palletizing robot, which has been largely manufactured in a factory.

Originality/value

This paper focuses on how the simulation-based optimization can be used for the purpose of generating trade-offs between cost, performance and lifetime when designing robotic drive system. An applicable optimization model and method are proposed to handle the dynamic performance optimization problem of a drive system for industrial robot.

Details

Industrial Robot: An International Journal, vol. 44 no. 6
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 8 May 2019

Feifei Bian, Danmei Ren, Ruifeng Li, Peidong Liang, Ke Wang and Lijun Zhao

The purpose of this paper is to present a method which enables a robot to learn both motion skills and stiffness profiles from humans through kinesthetic human-robot cooperation.

Abstract

Purpose

The purpose of this paper is to present a method which enables a robot to learn both motion skills and stiffness profiles from humans through kinesthetic human-robot cooperation.

Design Methodology Approach

Admittance control is applied to allow robot-compliant behaviors when following the reference trajectories. By extending the dynamical movement primitives (DMP) model, a new concept of DMP and stiffness primitives is introduced to encode a kinesthetic demonstration as a combination of trajectories and stiffness profiles, which are subsequently transferred to the robot. Electromyographic signals are extracted from a human’s upper limbs to obtain target stiffness profiles. By monitoring vibrations of the end-effector velocities, a stability observer is developed. The virtual damping coefficient of admittance controller is adjusted accordingly to eliminate the vibrations.

Findings

The performance of the proposed methods is evaluated experimentally. The result shows that the robot can perform tasks in a variable stiffness mode as like the human dose in the teaching phase.

Originality Value

DMP has been widely used as a teaching by demonstration method to represent movements of humans and robots. The proposed method extends the DMP framework to allow a robot to learn not only motion skills but also stiffness profiles. Additionally, the authors proposed a stability observer to eliminate vibrations when the robot is disturbed by environment.

Details

Assembly Automation, vol. 40 no. 1
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 13 May 2020

Tingting Miao and Hao Ju

Over the past several decades, there has been an increasing trend towards inter-city cooperation, which is an efficient policy option to deal with the challenges from…

Abstract

Purpose

Over the past several decades, there has been an increasing trend towards inter-city cooperation, which is an efficient policy option to deal with the challenges from globalization, regionalization and the externalities resulting from urban entrepreneurialism. Specific to China, the city governments, which mainly refer to prefecture-level and county-level governments, have also made many attempts to cooperate with respect to their local economic development and public affairs. Nevertheless, the results of these initiations to cooperate vary to a great extent. Based on a review of regional pollution governance in the Xiaoqing River area, tourism cooperation initiatives at Weishan Lake and transport integration between Jinan and Laiwu. The findings demonstrate that China's idiosyncratic institutional background has a significant impact on the shaping of inter-city cooperation. For the most part, leading small groups (LSGs) and their leadership property tend to determine the effectiveness of inter-city cooperation.

Design/methodology/approach

To examine the effect of the LSGs, we categorize them into three types, groups with strong leadership, weak leadership and self-forming leadership. Through reviewing regional pollution governance in the Xiaoqing River area, tourism cooperation initiatives at Weishan Lake and transport integration between Jinan and Laiwu, we try to probe the role of leading groups in the settlement of cross-administrative border issues.

Findings

Based on these three cases, the conclusion can be drawn that the leadership type of the LSG can exert an important influence on the efficiency of inter-city cooperation. If there is a leader with a higher administrative rank or authority, the cooperation can be quite efficient. Otherwise, the cooperative ending might be very negative. In terms of the operation principle, we can infer that even though the cities are always self-development oriented, the leader with higher authority or a strong coordinating capacity can convince and persuade the city leaders to overcome their self-centered behavior template and boost the cooperation to March on smoothly. Also, it means that the LSG is constrained by its personalistic characteristic. Key command derives from the person who chairs the LSG other than specific rules and norms. If the lead of the LSG leaves his position, the cooperation might just become paralyzed. From this point of view, the lack of legal basis remains to be the LSGs' significant deficiency and the future reform should attach more importance to the legalization of the LSGs so the operation of LSGs can be more standard and stable.

Originality/value

Many scholars have proposed their own theoretical models to explain the reason some cities successfully and effectively form cooperative relations, while the other cities do not. However, their models do not consider the idiosyncratic context of China or, how and to which extent LSGs can promote cooperation. Therefore, this paper seeks to probe which path in the context of China cities usually follows in the formation of joint efforts, and what role LSGs play in enabling cities to cooperate.

Details

International Journal of Public Leadership, vol. 16 no. 2
Type: Research Article
ISSN: 2056-4929

Keywords

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Article
Publication date: 4 September 2017

Wei Xie, Tariq Ali, Qi Cui and Jikun Huang

The purpose of this paper is to examine the potential economic impacts of China’s insect-resistant GM maize and provide new evidence for decision making concerning its…

Abstract

Purpose

The purpose of this paper is to examine the potential economic impacts of China’s insect-resistant GM maize and provide new evidence for decision making concerning its commercialization.

Design/methodology/approach

This study uses data drawn from the production trials of insect-resistant GM maize and expert interviews to determine the impacts of commercializing GM maize at farm level under three scenarios with varying severity of insect pest attacks in maize production. Economic impacts are simulated using a modified Global Trade Analysis Project model.

Findings

In farm terms, insect-resistant GM maize increases crop yield and reduces both pesticide and labor inputs. In national terms, China can increase its GDP by USD8.6 billion and maize self-sufficiency by about 2 percent given normal insect pest attacks if China commercializes GM maize. Additional beneficiaries include consumers and the livestock industry. Non-maize crops can also benefit from land saving through GM maize commercialization. Chemical is a sector with the decrease in its output because demand for pesticides will fall.

Originality/value

Although China has announced a roadmap for commercializing GM crops for use as feed and in processing after nearly two decades of producing GM cotton, no clear timetable for producing GM maize as feed has been established due to several concerns, including the potential for economic gains from GM maize. This study is the first to assess the economic impacts of commercializing China’s GM maize. The findings should have significant policy implications for the development and commercialization of GM crops in general and GM maize in particular.

Details

China Agricultural Economic Review, vol. 9 no. 3
Type: Research Article
ISSN: 1756-137X

Keywords

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