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Article
Publication date: 16 October 2017

Jianhua Su, Rui Li, Hong Qiao, Jing Xu, Qinglin Ai and Jiankang Zhu

The purpose of this paper is to develop a dual peg-in-hole insertion strategy. Dual peg-in-hole insertion is the most common task in manufacturing. Most of the previous…

Abstract

Purpose

The purpose of this paper is to develop a dual peg-in-hole insertion strategy. Dual peg-in-hole insertion is the most common task in manufacturing. Most of the previous work develop the insertion strategy in a two- or three-dimensional space, in which they suppose the initial yaw angle is zero and only concern the roll and pitch angles. However, in some case, the yaw angle could not be ignored due to the pose uncertainty of the peg on the gripper. Therefore, there is a need to design the insertion strategy in a higher-dimensional configuration space.

Design/methodology/approach

In this paper, the authors handle the insertion problem by converting it into several sub-problems based on the attractive region formed by the constraints. The existence of the attractive region in the high-dimensional configuration space is first discussed. Then, the construction of the high-dimensional attractive region with its sub-attractive region in the low-dimensional space is proposed. Therefore, the robotic insertion strategy can be designed in the subspace to eliminate some uncertainties between the dual pegs and dual holes.

Findings

Dual peg-in-hole insertion is realized without using of force sensors. The proposed strategy is also used to demonstrate the precision dual peg-in-hole insertion, where the clearance between the dual-peg and dual-hole is about 0.02 mm.

Practical implications

The sensor-less insertion strategy will not increase the cost of the assembly system and also can be used in the dual peg-in-hole insertion.

Originality/value

The theoretical and experimental analyses for dual peg-in-hole insertion are proposed without using of force sensor.

Details

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

Keywords

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Article
Publication date: 7 August 2017

Nagarajan Pitchandi, Saravana Perumaal Subramanian and Muhilan Irulappan

This paper aims to estimate the required insertion force and to analyze the influence of damping in a compliantly supported chamfered peg-in-hole assembly under dynamic conditions.

Abstract

Purpose

This paper aims to estimate the required insertion force and to analyze the influence of damping in a compliantly supported chamfered peg-in-hole assembly under dynamic conditions.

Design/methodology/approach

A mathematical model of the insertion process, including damping coefficient and stiffness of the compliance, insertion speed, mass, inertia and friction coefficient, has been developed. Computer aided design (CAD) model of the peg-in-hole assembly environment with passive compliance is created. The dynamic insertion force of the modeled environment is analyzed using multibody dynamics numerical solver.

Findings

The damping property of the viscoelastic materials used in the passive compliances suppresses the vibration caused due to the impulses in the transition of the peg in hole. It also increases the insertion force required for the peg insertion at the initial stage.

Research limitations/implications

As the search strategies are not considered in this work, it is assumed that the initial contact is ensured between the chamfer and the peg of the assembly. A constant insertion speed is maintained throughout the insertion. Otherwise, it could have been varied at different stages of the insertion for reducing the assembly time.

Practical implications

The developed assembly model can be used for predicting the insertion forces of a chamfered peg-in-hole assembly and for designing/selecting the compliance device for the required assembly environment.

Originality/value

The proposed insertion model has considered the damping and elastic property of the compliance material as a parallel arrangement of spring and dashpot. This approach aids in modeling an insertion process closer to real-time assembly process.

Details

Assembly Automation, vol. 37 no. 3
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 6 August 2020

Hongtai Cheng, Tianzhuo Liu, Wei Zhang and Lina Hao

Installing a tight tolerant stepped shaft is not a trivial task for an industrial robot. If all peg-hole constraints are complete, the cascaded peg-in-hole task can be…

Abstract

Purpose

Installing a tight tolerant stepped shaft is not a trivial task for an industrial robot. If all peg-hole constraints are complete, the cascaded peg-in-hole task can be simplified into several independent stages and accomplished one by one. However, if some of the constraints are incomplete, the cross stage interference will bring additional difficulties. This paper aims to discuss the cascaded peg-in-hole problem with incomplete constraints.

Design/methodology/approach

In this paper, the problem is formulated according to geometric parameters of the stepped shaft and completeness of the corresponding hole. The possible jamming type is modeled and analyzed. A contact modeling and control strategy is proposed to compensate the peg postures under incomplete constraints.

Findings

The above methods are implemented on an experiment platform and the results verify the effectiveness of the proposed robotic assembly strategy.

Originality/value

Based on force/torque sensor, a hybrid control strategy for incomplete constraints cascaded peg-in-hole assembly problem is proposed.

Details

Assembly Automation, vol. 40 no. 5
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 2 August 2011

Sigitas Kilikevicius and Bronius Baksys

The paper aims to investigate theoretically and experimentally the process of compliantly supported peg insertion into a bush for high‐speed assembly, when vibrations are…

Abstract

Purpose

The paper aims to investigate theoretically and experimentally the process of compliantly supported peg insertion into a bush for high‐speed assembly, when vibrations are provided to the bush in the axial direction, and to analyse the influence of the parameters of the dynamic system and excitation on the assembly process.

Design/methodology/approach

The mathematical model of parts vibratory insertion process is formed and the simulation is performed using a numerical computing software environment. The model includes inertia, compliance, dry friction, insertion speed and vibratory excitation. The three‐dimensional simulation of peg‐in‐hole insertion is accomplished using motion analysis software to test the influence of vibratory excitation on assembly failures, such as jamming and wedging. The experimental setup for the robotic vibratory assembly and the investigation methodology were presented. The experimental analysis of the vibratory insertion process of cylindrical parts with clearance is performed when the compliantly supported peg is inserted by the robot into the bush, which is excited in the axial direction.

Findings

The vibratory excitation allows preventing the balance between the insertion force and frictional forces and so to avoid jamming and wedging. It is advantageous to select such the frequency of vibrations under which the resonance state of the compliantly supported peg does not occur. The parameters of vibratory excitation and initial assembly state are defined which have the principal influence on the insertion duration and the success of the process. The experimental results show the applicability of the mathematical approach.

Research limitations/implications

The assumption is made that the chamferless rigid peg moves in a plane in respect of the rigid bush with a chamfer. Also, it is considered that there is no impact during the peg and bush contact. The dynamic and static friction coefficient between the parts is equivalent and the insertion speed is constant.

Practical implications

The results can be useful aiming to design the reliable high‐performance vibratory assembly equipment for peg‐hole type parts, which does not require sensors, feedback systems and control algorithms.

Originality/value

The proposed method of applying the vibratory excitation during the peg‐in‐hole insertion process allows to avoid jamming and wedging, and to minimize the duration of the process.

Details

Assembly Automation, vol. 31 no. 3
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 1 June 2001

H.Y.K. Lau and I.S.K. Lee

A neural network controller is proposed for the motion control of robot manipulators with force/torque feedback signals. This controller is trained with reinforcement…

Abstract

A neural network controller is proposed for the motion control of robot manipulators with force/torque feedback signals. This controller is trained with reinforcement learning algorithms and a model is extracted from the synaptic weights within the neural network. This model is continuously refined by the feedback signals to ensure its validity even in a stochastic and non‐stationary environment. With this model and the real‐time force/torque feedback data, the robot can acquire a fine skill for a particular assembly task for which it is trained.

Details

Assembly Automation, vol. 21 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 21 August 2017

Kamal Sharma, Varsha Shirwalkar and Prabir K. Pal

This paper aims to provide a solution to the first phase of a force-controlled circular Peg-In-Hole assembly using an industrial robot. The paper suggests motion planning…

Abstract

Purpose

This paper aims to provide a solution to the first phase of a force-controlled circular Peg-In-Hole assembly using an industrial robot. The paper suggests motion planning of the robot’s end-effector so as to perform Peg-In-Hole search with minimum a priori information of the working environment.

Design/methodology/approach

The paper models Peg-In-Hole search problem as a problem of finding the minima in depth profile for a particular assembly. Thereafter, various optimization techniques are used to guide the robot to locate minima and complete the hole search. This approach is inspired by a human’s approach of searching a hole by moving peg in various directions so as to search a point of maximum insertion which is same as the minima in depth profile.

Findings

The usage of optimization techniques for hole search allows the robot to work with minimum a priori information of the working environment. Also, the iterative nature of the techniques adapts to any disturbance during assembly.

Practical implications

The techniques discussed here are quite useful if a force-controlled assembly needs to be performed in a highly unknown environment and also when the assembly setup can get disturbed in between.

Originality/value

The concept is original and provides a non-conventional use of optimization techniques, not for optimization of some process directly but for an industrial robot’s motion planning.

Details

Industrial Robot: An International Journal, vol. 44 no. 5
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 3 April 2017

Kuangen Zhang, MinHui Shi, Jing Xu, Feng Liu and Ken Chen

This paper aims to realize the automatic assembly process for multiple rigid peg-in-hole components.

Abstract

Purpose

This paper aims to realize the automatic assembly process for multiple rigid peg-in-hole components.

Design/methodology/approach

This paper develops fuzzy force control strategies for the rigid dual peg-in-hole assembly. Firstly the fuzzy force control strategies are presented. Secondly the contact states and contact forces are analyzed to prove the availability of the force control strategies.

Findings

The rigid dual peg-in-hole assembly experimental results show the effectiveness of the control strategies.

Originality/value

This paper proposes fuzzy force control strategies for a rigid dual peg-in-hole assembly task.

Details

Assembly Automation, vol. 37 no. 2
Type: Research Article
ISSN: 0144-5154

Keywords

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Article
Publication date: 17 February 2012

Jianhua Su, Hong Qiao, Zhicai Ou and Yuren Zhang

The purpose of this paper is to give a novel sensor‐less manipulation strategy for the high‐precision assembly of an eccentric peg into a hole.

Abstract

Purpose

The purpose of this paper is to give a novel sensor‐less manipulation strategy for the high‐precision assembly of an eccentric peg into a hole.

Design/methodology/approach

Based on the authors' previous work on the attractive region, this paper proposes the sensorless eccentric peg‐hole insertion strategy. The analysis is based on the visible strategic behaviors by decomposing the high‐dimensional configuration space of the eccentric peg‐hole into two low dimensional configuration subspaces. Then, the robotic manipulations can be designed in the configuration subspaces. Finally, a typical industry application, fitting an eccentric crankshaft into a bearing hole of the automotive air‐conditioners, is used to validate the presented strategy.

Findings

The attractive region constructed in the configuration space has been applied to guide the robotic manipulations, such as, the locating and the insertion.

Practical implications

The designed robotic assembly system without using force sensor or flexible wrist has an advantage in terms of expense and durability for the automotive air‐conditioners manufacturing industry.

Originality/value

Most previous work on sensorless manipulation strategy has concentrated on inserting a symmetric peg into a hole. However, for the assembly of an eccentric peg into a hole, the robotic manipulations should be explored in a high‐dimensional configuration space as the six‐DOFs of the eccentric peg. In this paper, the decomposition method of the high‐dimensional configuration space would make the system analysis visible; then, the assembly strategy can be easily designed in the two subspaces.

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Article
Publication date: 27 July 2021

Xinwang Li, Juliang Xiao, Wei Zhao, Haitao Liu and Guodong Wang

As complex analysis of contact models is required in the traditional assembly strategy, it is still a challenge for a robot to complete the multiple peg-in-hole assembly…

Abstract

Purpose

As complex analysis of contact models is required in the traditional assembly strategy, it is still a challenge for a robot to complete the multiple peg-in-hole assembly tasks autonomously. This paper aims to enable the robot to complete the assembly tasks autonomously and more efficiently, with the strategies learned by reinforcement learning (RL), a learning-accelerated deep deterministic policy gradient (LADDPG) algorithm is proposed.

Design/methodology/approach

The multiple peg-in-hole assembly strategy is designed in two modules: an advanced planning module and a bottom control module. The advanced module is completed by the LADDPG agent, which is used to derive advanced commands based on geometric and environmental constraints, that is, the desired contact force. The bottom-level control module will drive the robot to complete the compliant assembly task through the adaptive impedance algorithm according to the command set issued by the advanced module. In addition, a set of safety assurance mechanisms is developed to safely train a collaborative robot to complete autonomous learning.

Findings

The method can complete the assembly tasks well through RL, and it can realize satisfactory compliance of the robot to the environment. Compared with the original DDPG algorithm, the average values of the instantaneous maximum contact force and contact torque during the assembly process are reduced by approximately 38% and 74%, respectively.

Practical implications

The entire algorithm can also be applied to other robots and the assembly strategy can be applied in the field of the automatic assembly.

Originality/value

A compliant assembly strategy based on the LADDPG algorithm is proposed to complete the automated multiple peg-in-hole assembly tasks.

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: 5 October 2018

Zhimin Hou, Markus Philipp, Kuangen Zhang, Yong Guan, Ken Chen and Jing Xu

This paper aims to present an optimization algorithm combined with the impedance control strategy to optimize the robotic dual peg-in-hole assembly task, and to reduce the…

Abstract

Purpose

This paper aims to present an optimization algorithm combined with the impedance control strategy to optimize the robotic dual peg-in-hole assembly task, and to reduce the assembly time and smooth the contact forces during assembly process with a small number of experiments.

Design/methodology/approach

Support vector regression is used to predict the fitness of genes in evolutionary algorithm, which can reduce the number of real-world experiments. The control parameters of the impedance control strategy are defined as genes, and the assembly time is defined as the fitness of genes to evaluate the performance of the selected parameters.

Findings

The learning-based evolutionary algorithm is proposed to optimize the dual peg-in-hole assembly process only requiring little prior knowledge instead of modeling for the complex contact states. A virtual simulation and real-world experiments are implemented to demonstrate the effectiveness of the proposed algorithm.

Practical implications

The proposed algorithm is quite useful for the real-world industrial applications, especially the scenarios only allowing a small number of trials.

Originality/value

The paper provides a new solution for applying optimization techniques in real-world tasks. The learning component can solve the data efficiency of the model-free optimization algorithms.

Details

Assembly Automation, vol. 38 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

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