In recent years,industrial robots have received extensive attention in manufacturing field due to their high flexibility and great workspace.However,the weak stiffness of industrial robots makes it extremely easy to a...In recent years,industrial robots have received extensive attention in manufacturing field due to their high flexibility and great workspace.However,the weak stiffness of industrial robots makes it extremely easy to arouse chatter,which affects machining quality inevitably and generates noise pollution in severe cases.Compared with drilling,the chatter mechanism of robotic countersinking is more complex.The external excitation changes with cutting width and depth in countersinking.This characteristic results in time-varying and nonlinearity of robotic countersinking dynamics.Thus,it is urgent to propose a new method of chatter suppression and provide an accurate stability analysis model.As a new special machining technology,rotary ultrasonic machining has been proved to improve robotic drilling and milling stability effectively.Based on this,robotic rotary ultrasonic countersinking(RRUC)is proposed to improve the robotic countersinking stability in this paper.A three-dimensional stability domain method of RRUC is established.First,the countersinking process was divided intoρparts.The dynamic model of every unit was constructed based on ultrasonic function angle(γ)and dynamic chip area.Then,the stability region of RRUC is obtained based on the semi-discrete method(SDM).Compared with the robotic conventional countersinking(RCC),RRUC improves the stability by 27%.Finally,the correctness and effectiveness of the stability region model are proved by robotic ultrasonic countersinking experiments.展开更多
Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires d...Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires drilling and countersinking.Robotic machining systems are gradually used in the machining of holes due to their high flexibility.However,weakly rigid stacked structure and low-stiffness industrial robot system bring about complex and diverse countersinking depth errors,which significantly affects the fatigue life of components.In this paper,the influence mechanism of ultrasonic energy on the accuracy of robotic countersinking of stacked structure is investigated.Firstly,a workpiece deformation model is established with the thinwalled plate deformation theory,defined as static error.Then,the vibration of the industrial robot is calculated from the acceleration with the frequency domain integration,defined as dynamic error.The suppression of ultrasonic energy on the two kinds of errors were elucidated,respectively.Base on this,a depth compensation model of robotic ultrasonic countersinking is established.Finally,the feasibility of the accuracy compensation is experimentally verified,and the countersinking depth error can be controlled within±0.09 mm.展开更多
The slug rivet is widely used in wing assembly due to its longer fatigue life and better sealing performance compared with other connection technologies.As a countersink with dual-angle is widely adopted for this type...The slug rivet is widely used in wing assembly due to its longer fatigue life and better sealing performance compared with other connection technologies.As a countersink with dual-angle is widely adopted for this type of connection,the countersink diameter and depth are key factors that affect assembly quality.Therefore,it is of great importance to efficiently inspect the countersink quality to ensure high accuracy.However,contact measurements are susceptible to the loss of accuracy due to cutting debris and lube build-up,while the hole-scanning method using laser profilometry is time consuming and complex.In this paper,a non-contact method for countersink diameter and depth measurement based on a machine vision system is proposed.The countersink diameter can be directly measured by the machine vision system,while the countersink depth is determined through the countersink diameter indirectly.First,by means of image processing technology together with an improved edge detection algorithm,the countersink diameter can be obtained.Then,a 3D microscope is employed to measure the countersink depth,which helps to model the countersink.As a result,once the countersink diameter is measured,so is the depth.The experimentation demonstrated that this method has strong feasibility and enables time saving,which is conducive to improve the riveting efficiency.展开更多
基金the Project on the Technological Leading Talent Teams Led by Frontiers Science Center for Complex Equipment System Dynamics(No.FSCCESD220401)the National Natural Science Foundation of China(No.52075265).
文摘In recent years,industrial robots have received extensive attention in manufacturing field due to their high flexibility and great workspace.However,the weak stiffness of industrial robots makes it extremely easy to arouse chatter,which affects machining quality inevitably and generates noise pollution in severe cases.Compared with drilling,the chatter mechanism of robotic countersinking is more complex.The external excitation changes with cutting width and depth in countersinking.This characteristic results in time-varying and nonlinearity of robotic countersinking dynamics.Thus,it is urgent to propose a new method of chatter suppression and provide an accurate stability analysis model.As a new special machining technology,rotary ultrasonic machining has been proved to improve robotic drilling and milling stability effectively.Based on this,robotic rotary ultrasonic countersinking(RRUC)is proposed to improve the robotic countersinking stability in this paper.A three-dimensional stability domain method of RRUC is established.First,the countersinking process was divided intoρparts.The dynamic model of every unit was constructed based on ultrasonic function angle(γ)and dynamic chip area.Then,the stability region of RRUC is obtained based on the semi-discrete method(SDM).Compared with the robotic conventional countersinking(RCC),RRUC improves the stability by 27%.Finally,the correctness and effectiveness of the stability region model are proved by robotic ultrasonic countersinking experiments.
基金co-supported by the National Key Research and Development Program of China(No.2024YFB4711201)National Natural Science Foundation of China(Nos.U22A20204,52305472)。
文摘Carbon Fiber Reinforced Polymer(CFRP)and aluminum stacked are widely used in aircraft assemble thanks to the high strength-to-weight ratio.Riveting is an important joining technique of stacked structure and requires drilling and countersinking.Robotic machining systems are gradually used in the machining of holes due to their high flexibility.However,weakly rigid stacked structure and low-stiffness industrial robot system bring about complex and diverse countersinking depth errors,which significantly affects the fatigue life of components.In this paper,the influence mechanism of ultrasonic energy on the accuracy of robotic countersinking of stacked structure is investigated.Firstly,a workpiece deformation model is established with the thinwalled plate deformation theory,defined as static error.Then,the vibration of the industrial robot is calculated from the acceleration with the frequency domain integration,defined as dynamic error.The suppression of ultrasonic energy on the two kinds of errors were elucidated,respectively.Base on this,a depth compensation model of robotic ultrasonic countersinking is established.Finally,the feasibility of the accuracy compensation is experimentally verified,and the countersinking depth error can be controlled within±0.09 mm.
文摘The slug rivet is widely used in wing assembly due to its longer fatigue life and better sealing performance compared with other connection technologies.As a countersink with dual-angle is widely adopted for this type of connection,the countersink diameter and depth are key factors that affect assembly quality.Therefore,it is of great importance to efficiently inspect the countersink quality to ensure high accuracy.However,contact measurements are susceptible to the loss of accuracy due to cutting debris and lube build-up,while the hole-scanning method using laser profilometry is time consuming and complex.In this paper,a non-contact method for countersink diameter and depth measurement based on a machine vision system is proposed.The countersink diameter can be directly measured by the machine vision system,while the countersink depth is determined through the countersink diameter indirectly.First,by means of image processing technology together with an improved edge detection algorithm,the countersink diameter can be obtained.Then,a 3D microscope is employed to measure the countersink depth,which helps to model the countersink.As a result,once the countersink diameter is measured,so is the depth.The experimentation demonstrated that this method has strong feasibility and enables time saving,which is conducive to improve the riveting efficiency.
