Search results

The purpose of this paper is to propose a new trajectory planning algorithm for industrial robots, which can let the robots move through a desired spatial trajectory, avoid colliding with other objects and achieve accurate movements. Trajectory planning algorithms are the soul of motion control of industrial robots. A predefined space trajectory can let the robot move through the desired spatial coordinates, avoid colliding with other objects and achieve accurate movements.

The mathematical expressions of the proposed algorithm are deduced. The speed control, position control and orientation control strategies are realized and verified with simulations, and then implemented on a six degrees of freedom (6-DOF) industrial robot platform.

A fixed-distance trajectory planning algorithm based on Cartesian coordinates was presented. The linear trajectory, circular trajectory, helical trajectory and parabolic trajectory in Cartesian coordinates were implemented on the 6-DOF industrial robot.

A simple and efficient algorithm is proposed. Enrich the kind of trajectory which the industrial robot can realize. In addition, the industrial robot can move more concisely, smoothly and precisely.

The purpose of this paper is to present a novel laser pointer for manual coating robot teaching. The laser pointer has simple structure and no physical contact with substrate in teaching work. The sensitivity of visual detection in the design accuracy is guaranteed.

The strategy adopts two laser sources to form a triangle to achieve a fixed distance detection pointer for manual robot teaching. After optimizing the source, spot size and the incident angle of the lasers, the sensitivity of fixed-distance judgment is analyzed and compared with traditional pointers. In addition, the laser pointer adds the functions to simulate coating atomizer, including posture and overlap pitch. Finally, the laser pointer verified by coating application and measurement system analysis evaluation.

The laser pointer has been successfully applied to coating robot teaching by the authors’ team. From the simulation and experimental results, it can be concluded that the proposed approach is effective at improving manual teaching of coating robot, especially for the complex geometry.

The main function of the laser pointer often used for manual teaching in other purposes; for example, sealer etc. The paper innovatively considered and tested the laser pointer on robotic coating process.

Compared with the traditional hard straight stick pointer, the paper proposes a very simple construction for teaching pointer with laser feature. At the same time, the requirement of coating process simulation is considered.

Micro-focus X-ray computed tomography (CT) can be used to quantitatively evaluate the packing density, pore connectivity and provide the basis for specimen derived simulations of gas permeability of sand mould. This non-destructive experiment or following simulations can be done on any section of any size sand mould just before casting to validate the required properties. This paper aims to describe the challenges of this method and use it to simulate the gas permeability of 3D printed sand moulds for a range of controlling parameters. The permeability simulations are compared against experimental results using traditional measurement techniques. It suggests that a minimum volume of only 700 × 700 × 700 µm³ is required to obtain, a reliable and most representative than the value obtained by the traditional measurement technique, the simulated permeability of a specimen.

X-ray tomography images were used to reconstruct 3D models to simulate them for gas permeability of the 3D printed sand mould specimens, and the results were compared with the experimental result of the same.

The influence of printing parameters, especially the re-coater speed, on the pore connectivity of the 3D printed sand mould and related permeability has been identified. Characterisation of these sand moulds using X-ray CT and its suitability, compared to the traditional means, are also studied. While density and 3PB strength are a measure of the quality of the moulds, the pore connectivity from the tomographic images precisely relates to the permeability. The main conclusions of the present study are provided below. A minimum required sample size of 700 × 700 × 700 µm³ is required to provide representative permeability results. This was obtained from sand specimens with an average sand grain size of 140 µm, using the tomographic volume images to define a 3D mesh to run permeability calculations. Z-direction permeability is always lower than that in the X-/Y-directions due to the lower values of X-(120/140 µm) and Y-(101.6 µm) resolutions of the furan droplets. The anisotropic permeability of the 3D printed sand mould is mainly due to, the only adjustable, X-directional resolution of the furan droplets; the Y-directional resolution is a fixed distance, 102.6 µm, between the printhead nozzles and the Z-directional one is usually, 280 µm, twice the size of an average sand grain.A non-destructive and most representative permeability value can be obtained, using the computer simulation, on the reconstructed 3D X-ray tomography images obtained on a specific location of a 3D printed sand mould. This saves time and effort on printing a separate specimen for the traditional test which may not be the most representative to the printed mould.

The experimental result is compared with the computer simulated results.

The purpose of this paper is to prepare a new combined method of rapid prototyping, fused deposition modeling (FDM) and electrospinning for the fabrication of coronary artery bypass graft (CABG).

A dynamically optimum design of blood vessel graft was constructed using FDM and electrospinning. Fabrication of 3‐D CABG model was constructed using pro‐engineer based on the optimum hemodynamic analysis and was converted to an stereolithography file format which was imported to the Magic software where it was edited to a high‐resolution contour. The model was then created from acrylonitrile butadiene styrene which was used as a collector for electrospinning fabrication. For the electrospinning thermoplastic polyurethane was dissolved with hexafluoroisopropanol. The voltage applied for electrospinning was 15 kV where the solid FDM model was used to collect nanofibers at fixed distance.

The properties of the fabricated vessel agreed well with those of human artery. The proposed method can be effectively used for the fabrication of an optimized graft design. This proposed method has been proved as a promising fabrication processes in fabricating a specially designed graft with the correct physical and mechanical properties.

The proposed method is novel and combines the advantages of both FDM and electrospinning techniques.

The purpose of this paper is to present a methodology and experimental results on using global optimization algorithms to determine the optimal orbit, based on the mission requirements, for a set of spacecraft flying in formation with an asteroid.

A behavioral‐based hybrid global optimization approach is used to first characterize the solution space and find families of orbits that are a fixed distance away from the asteroid. The same optimization approach is then used to find the set of Pareto optimal solutions that minimize both the distance from the asteroid and the variation of the Sun‐spacecraft‐asteroid angle. Two sample missions to asteroids, representing constrained single and multi‐objective problems, were selected to test the applicability of using an in‐house hybrid stochastic‐deterministic global optimization algorithm (Evolutionary Programming and Interval Computation (EPIC)) to find optimal orbits for a spacecraft flying in formation with an orbit. The Near Earth Asteroid 99942 Apophis (2004 MN₄) is used as the case study due to a fly‐by of Earth in 2029 leading to two potential impacts in 2036 or 2037. Two black‐box optimization problems that model the orbital dynamics of the spacecraft were developed.

It was found for the two missions under test, that the optimized orbits fall into various distinct families, which can be used to design multi‐spacecraft missions with similar orbital characteristics.

The global optimization software, EPIC, was very effective at finding sets of orbits which met the required mission objectives and constraints for a formation of spacecraft in proximity of an asteroid. The hybridization of the stochastic search with the deterministic domain decomposition can greatly improve the intrinsic stochastic nature of the multi‐agent search process without the excessive computational cost of a full grid search. The stability of the discovered families of formation orbit is subject to the gravity perturbation of the asteroid and to the solar pressure. Their control, therefore, requires further investigation.

This paper contributes to both the field of space mission design for close‐proximity orbits and to the field of global optimization. In particular, suggests a common formulation for single and multi‐objective problems and a robust and effective hybrid search method based on behaviorism. This approach provides an effective way to identify families of optimal formation orbits.

The purpose of this paper is two‐fold. First, to deal with the problem of audio speaker localization and second, to deal with the problem of mobile camera control. The task of speaker localization consists of determining the position of the active speaker and the task of camera control consists of orienting a mobile camera towards that active speaker. These steps represent the main task of speaker tracking, which is the global purpose of the research work.

In this approach, two‐channel‐based estimation of the speaker position is achieved by comparing the signals received by two cardioids microphones, which are placed the one against the other and separated by a fixed distance. The localization technique presented in this paper is inspired from the human ears, which act as two different sound observation points, enabling humans to estimate the direction of the speaking person with a good precision. Concerning the camera control part, the authors have conceived an automatic system for generating the command signals and controlling the rotation of the mobile camera by a stepper motor.

The off‐line experiments of speaker tracking by camera have been done in a small meeting room without echo cancelation. Results show the good performances of the proposed localization methods and a correct tracking by camera.

This new technique can be used for the automatic supervision of smart rooms.

The work described in this paper is original, since it uses only two microphones for the speaker localization.

Emergencies commonly reveal the disorder from which routine order is painfully extracted. They dramatise social fissures, inconsistencies and ignorance that ordinarily remain hidden or can be ignored without damage or controversy. They transform the taken‐for‐granted into the up‐for‐discussion, compel the formation of decisions and accompanying justifications, and demand action of a special and urgent kind. Using Unger (1988) terminology, we can say that emergencies might reduce fixed distance between context and routines, thus they can be perceived as “context‐revising” situations, providing possibilities for lifting “a powerful constraint over all social practices, forcing them into a specific mould of predictable routines” (Unger 1988, p. 125). AIDS (an acronym formally designating the most developed stage of HIV infection but misleadingly used in our lexicon of public concern to stand for the disease as a whole), is such an emergency, not only due to the extent of the spread of the disease, but because this epidemic presents so many difficult ethical, legal and technical issues, and because of growing and changing knowledge about the disease, it requires continuous rethinking of strategies and adopting them to new discoveries.

The aim of this paper is to develop a technique to measure the oil film thickness between piston ring and liner throughout the stroke, without impairing the surface properties of the piston ring and liner. Mechanical properties of the piston ring, like ring stiffness, are also not altered. Effect of variation in bore on the movement of piston ring can be studied with the proposed technique.

The gap Hmin between the cylinder liner and the piston ring is formed due to the hydrodynamic pressure generated by the presence of oil film between piston ring and liner. This gap can be inferred by measuring the movement of the inner surface of piston ring with reference to a sensor mounted on the piston at a fixed distance from the piston ring. The piston ring is connected to the sensor through reasonably rigid member. The underlying assumption here is that there is no elastic deformation of the piston ring due to the hydrodynamic pressure. The fundamental sensor to measure oil film thickness used in this setup is a set of strain gauges.

It is possible to measure oil film thickness by the proposed arrangement for the entire stroke without changing the surface properties. Mechanical properties of the piston ring, like ring tension, are not affected. The results possibly provide the correct picture of the piston ring movement throughout the stroke. The measurement at near zero speed can give information on the movement of the piston ring due to hydrodynamic action and to the variation in the bore. The measurement is not affected by engine vibrations. The proposed technique can be helpful in validating the theoretical models proposed in the literature.

The measurement is possible only in unfired condition. However, this attempt can be considered as the basis to measure OFT in fired condition with necessary improvements. It is not feasible to measure quantity of lubricant/extent of lubricant on leading or trailing edge of piston. Effect of temperature on the oil film thickness cannot be studied as the engine is not fired. It is assumed that the piston ring does not pass through elasto‐hydrodynamic lubrication regime. Debris/worn out particles in the oil may affect the indicated oil film thickness at local points.