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Abstract Industrial robots are widely used in various industrial fields, such as handling and welding, due to their good repeat positioning accuracy. The motion error determines the absolute accuracy. For robot design, dimensional parameter errors and drive parameter errors, a mathematical model of a kinematic exponential product with error screws was proposed. The influence of different rod lengths and transmission errors on the accuracy of the end motion was analysed. A composite analysis method based on screw theory and vector method is proposed for the spatial deflection error of robot rotating joints with clearance. By using screw theory, a mathematical error model of the axial movement and spatial deflection of the joint gap was established. A mathematical model of joint space radial movement was established by using the three-dimensional vector method. Through numerical simulation, the position distribution law of the random error of the robot terminal in the workspace and the distribution of the plane projection density were obtained. By solving the attitude matrix, the distribution of each Euler angle error was obtained. A simulation test was carried out to verify the model's correctness. The calculation showed that the method is simple and correct, and the obtained error distribution characteristics are of great significance to improving robotic kinematic calibration accuracy and optimising the spatial position error distribution.

The clearance of a kinematic pair will lead to the contact collision between the joints of the mechanism, which will have a great influence on the dynamic characteristics of a mechanical system with clearance. In order to study the influence of a rotating motion pair with clearance on the dynamic characteristics of a tool changing robot, a contact wear dynamics model of a modular tool changing robot was established based on the three-state model of “free-contact-collision”. Different from analysis of a light linkage structure, this paper takes a solid structure with large mass as the analysis object. Based on the impact contact force model and the improved Coulomb friction model, the effects of clearance size, rotational speed and friction coefficient on the dynamic characteristics of the tool changing robot were analyzed. The Archard wear model was used to predict the wear between the motion pairs with clearance. The analysis results show that, with the increase of clearance size and actuating speed, the fluctuation range of velocity and acceleration increases, and the fluctuation frequency decreases. Under the action of friction, the contact force between components will be reduced due to energy loss so that the kinematic reliability of the mechanism is improved. The wear of the moving pair with clearance is non-uniform. Through the research of this paper, the motion characteristics of the tool-changing robot at low speed and heavy load are clarified. The results show that the established method can realize the dynamic characteristics analysis of low-speed heavy-duty mechanisms with joint gaps, which can be used to guide the design of tool-changing robots, and also has important reference significance for the design of mechanisms containing joint gaps in general.

The harsh environmental loads may lead to strength failure in the turbine in an aero-engine. To accurately assess the strength reliability of the turbine under multiple loads, the stress distributions of 41 danger sites of a turbine under thermal, centrifugal, and pneumatic loads were determined by the flow-thermal-solid coupling analysis using ANSYS. Second, based on the flow-thermal-solid coupling analysis and response surface method, the probabilistic analysis model of stress at the danger site was established. And the probabilistic distribution of stress was determined by sampling and hypothesis testing. Finally, the reliability model of the turbine with multi-site damage and failure dependency was established, by which a reliability of 0.99802 was calculated. And the actual reliability of the turbine was 0.99626 determined by the Monte Carlo simulations, which verified the model in precision. The results indicated that the reliability model has a high efficiency and higher precision than the traditional reliability model with failure independence. [ABSTRACT FROM AUTHOR]

Escalators are now more and more widely used around the world. As escalator accidents occur from time to time, it is very important to analyze the structure and reliability of escalators. This paper studies the structure and reliability analysis methods of typical escalators. By applying parametric analysis methods, the efficiency and accuracy of escalator structure analysis are greatly improved. Because the failure of each structural member of the escalator truss system is dependent, this paper applies the dependent failure reliability modeling method and analyzes the reliability of the escalator truss system. The results show that the reliability analysis method of the truss system after considering the dependent failure is more reasonable. The above research work has certain reference significance for the design and analysis of escalators. [ABSTRACT FROM AUTHOR]

A component with multiple weak sites is widely used in practical engineering and the existence of multiple weak sites can significantly decrease the component reliability. On the other hand, only a few components bear static loading and most components bear dynamic loading. In this paper, a reliability model of isomorphic component with multiple weak sites is built based on an order statistics model and the influences of strength decentrality and loading decentrality on isomorphic component with multiple weak sites are discussed. Furthermore the influence of loading times is studied in detail. The results show that unlike a component with only one weak site, not only does the failure of a component with multiple weak sites have a relationship with the safety margin, but there also exist relationships with the number of weak sites, the loading roughness, and loading times. he work in this paper is of some guiding significance in reliability design and assessment of a component with multiple weak sites under complex loading. [ABSTRACT FROM AUTHOR]