Abstract: Dynamic control on hydraulic machine system and kinematic control on industrial robotic manipulators are two studied topics in this research. The main objective of this study is to analyze dynamic, forward kinematic and inverse kinematic on a couple of mechanical systems and hydraulic mechanical systems in order to control these machines. The characteristics of hydraulic and manipulator robot parameters are firstly calculated by using dynamic theories. In the former topic, we perform an example on CNC machine tools which is designing a hydraulic controller to move a cutting tool along a circular path. Dynamics analysis, forward kinematics and inverse kinematics of industrial robotic are archived in the latter topic. Two experiments were also performed on RRR and RRRRRR manipulators by analyzing the inverse kinematic equations to make these robots follow the desired trajectories. This study takes innovations and achieves control improvement in different systems with optimization controller or trajectory planning.
Abstract: An elastic-plastic contact stress analysis is presented to study cyclic plastic deformation of rolling elements under repeatedly contact loadings. The rolling contact is simulated by a Hertzian line contact loading translating over the surface of an elastic-plastic half-space, and the Chaboche nonlinear hardening rule is used to model the cyclic plastic behavior of contact components. A finite element procedure based on the return mapping algorithm is implemented to analyze the evolution plastic strains and residual stresses versus contact cycles. For the contact loading below the shakedown limit, p0/k=4, the plastic deformation occur only at first few contact cycles and become pure elastic in the subsequent cycles due to the existing residual stresses and material hardening. For the contact loading exceeding the shakedown limit, p0/k=7, the plastic strains increase progressively with each pass of contact cycles and result in plastic ratchetting. The normal residual stresses, however, quickly reach a steady state after few contact cycles.
Abstract: Guided-waves-based diagnostic imaging techniques have been attracting much attention due to their merits including easily interpretable image, high identification accuracy and suitable for online surveillance. In this study, to envisage the difficulty in detecting orientation-specific damage (crack, notch etc.), a novel guided-waves-based diagnostic imaging technique capable of inspecting complicated engineering structures was developed, in terms of the relationship between damage parameters (location, orientation and severity) and extracted guided waves signal features (time-of-flight, signal correlation and signal energy). Experimental studies were performed to verify the developed diagnostic imaging approach, where a through-thickness crack was successfully identified in a metallic plate and a part of real rail structure respectively.
Abstract: High speed transmission table is wildly used in industry and the demand is increased recently. High speed ball-screw device is a major component in the system. High speed transmission brings high friction and causes serious thermal displacement, especially in vertical transmission situation. Because the external load is become axial load applied on nut directly. Friction and wear became heavier on contact areas between ball and raceways, preload in ball-screw will thus be decreased speedily with operating time. The decrease of preload is also affect thermal rising rate and thermal displacement.The work of this paper is to establish a thermal elastic-viscous hydrodynamic lubrication (EHL) analysing model for friction calculation. Contact and friction forces of each contact area varying with operating conditions of ball-screw can be obtained as boundary conditions of FEM model, and theoretical results were well confirmed with surface temperature and displacement of screw. The aim of the study is useful in understanding thermal effect for a preloaded double nut ball-screw in vertical transmission.
Abstract: Robot simulation has developed quickly in recent decades. Along with the development of computer science, a lot of simulation soft-wares have been created to perform many purposes such as studying kinematic, dynamic, and off-line program to avoid obstacle on manipulator robots. The main objective of this study is therefore to analyze kinematic, dynamic characteristics of an R-R robotic manipulator in order to control this robot. Newton-Euler method was used to calculate the torque acting on each joint of the robot. Then, a numerical model of the robot was established by a multi-body dynamics software to compare with the results obtained by Newton-Euler theory. After that, a feed-forward control system was created by RecurDyn/CoLink to control the end-effector of the robot following a desired trajectory. The results showed that this research can be used for efficient simulation of structural kinematics, dynamics as well as control of the real manipulator robot with the robot structure in a virtual environment.
Abstract: Due to the reasons of manufacture cost and mechanical efficiency, the gear transmissions for electric vehicles are helical gear reducers. For electric vehicles, the reduction ratios are required to be 11~30 and their gear reducers are helical gear reducer with two gear pairs. This paper focused on the design and prototype manufacture of helical gear reducers with two gear pairs. First, according to the kinematic requirements of electric vehicles, their reduction ratios were derived. Then, based on the involute theorem, the gear data of helical spur gear pairs we obtained. Finally, according to the gear data, its corresponding engineering drawings were accomplished and its corresponding prototype was manufactured. The results of this paper can be used as reference for engineers to design the gear reducers for electric vehicles.
Abstract: This paper reports comparative studies on effects of interlayer on mechanical properties of diamond-like carbon (DLC) coatings. Two interlayers, TiC/Ti and CrC/Cr, were deposited and studied. The DLC coatings were prepared by using an unbalanced magnetron sputtering system. The chemical composition, micro-structure, constituted phases, and fundamental mechanical and tribological properties were evaluated. The results showed that the two amorphous (a-) DLC coatings were obtained. The a-DLC coating with the TiC/Ti interlayer showed higher adhesion, hardness and wear resistance than the one with the CrC/Cr interlayer.
Abstract: This study discusses the mechanical and tribological properties of a series of carbon nitride coatings deposited by unbalanced DC magnetron sputtering using nitrogen-argon mixture gas and graphite targets. The carbon nitride coatings were with varying carbon/nitrogen ratio by varying the gas flow rate ratio of nitrogen gas/argon while kept the overall gas flow rate at constant. The carbon nitride coatings with C/N ratios from 2.01 to 3.27 were obtained. The coatings were characterized and studied by nanohardness, scratching, and wear testers. It was found that the carbon nitride coatings with C/N ratio=2.36 showed the best performance of all the evaluated properties.
Abstract: The surface micro-temperature of sliding, rough bodies is an important factor affecting contact properties, such as chemical reactions of automatic injectors for medicine and chemical processes and surface failure of micro-and macro-devices. In this work, the Finite Element Method is used to analyze the micro-temperature of the peaks and valleys of multiplying asperity sliding contact surfaces. The affecting parameters include pressure, roughness, sliding speed, Peclet number, and thermal conductivity of rough surfaces. Analysis results showed that the effects of the studied parameters are different to those of peak and valley temperatures. While pressure increased, the increasing rate of the temperature rise parameter of valleys was larger than those of peaks. The temperature rise of peaks increased as roughness increased. On the contrary, the temperature rise of valleys decreased as roughness increased. Sliding speed and thermal conductivity played the most important roles in affecting the maximum micro-temperature rise. The temperature rise difference between peaks and valleys was almost proportional to thermal conductivity, and was inversely proportional to sliding speed for all cases. This transient thermal analysis enables precision control of interface micro-temperature for micro-moving devices.