Applied Mechanics and Materials Vol. 759

Abstract: The paper presents the finite element, which can be used to analyse the vibration of a three–layer beam with magnetorheological (MR) fluid layer. The MR fluid layer was sealed with silicone rubber. On the basis of the analysis of displacements, deformations of each layer has been established. Next, potential and kinetic energy of the three–layer beam were calculated. Because of the complexity of the beam with MR fluid, efficient solutions can be obtained only after discretization of the system. The finite element method was used in the study. For this purpose the mass and stiffness matrices were determined for the proposed linear finite element of two nodes and four degrees of freedom in each node.

Abstract: The paper presents the procedure of identification of a complex shear modulus which describes properties of MR fluid in the pre-yield regime as a function of magnetic field. Data necessary for identification were collected basing on measurements of free vibrations of a three-layered cantilever beam at a special laboratory stand. Magnetic field exerting on MR fluid placed in the beam was generated by electromagnet. In the next step, complex modes of beam vibrations for various places of applying the magnetic field and its strength were calculated.

Abstract: Cr/CrN multilayers with a bilayer period λ = 62 ÷ 1000nm, were investigated. They were deposited by PLD technique on austenitic and ferritic stainless steel substrates. Coating hardness and adhesion to substrates were measured by nanoindentation and scratch testing. Multilayer properties were compared with single Cr and CrN coatings. The 2xCr/CrN and 4xCr/CrN multilayers exhibited hardness slightly lower than the hardness of a single CrN coating, while the critical load of the 4xCr/CrN multilayer, measured in the scratch test, was two times higher than for CrN. Furthermore, the character of coating failure also indicates the higher fracture toughness of multilayers than ceramic ones. The highest scratch resistance of the hardest multilayer with a bilayer period λ = 250nm is extremely interesting. The measured values of the critical loads L_C1 and L_C2 of all coatings were higher for harder ferritic than austenitic substrates. However, analysis of scratch track geometry indicated that coating failure occurred under the same deformation of the coating-substrate system, while the higher values of critical load for coatings on ferrite derived from the higher hardness of the substrate.

Abstract: In this study the analysis of the magnetic field distribution of an electromagnet is presented. This electromagnet is used as an actuator in a semi-active vibration control of the three-layer beam with MR fluid. Two separate numerical methods are used for the purpose of calculating the magnetic field distribution. The first method is based on the Finite Element Method and implemented using ANSYS software. The second, simplified one is based on the assumption that the electromagnet can be substituted by a simple magnetic circuit divided into separate paths, with each sub-path defined by the value of reluctance of the corresponding electromagnet part. The comparison of the results from both methods with the ones obtained from an experiment is also presented and analyzed in the paper.

Abstract: The subject of this work is to develop a control system for the two degree of freedom robot manipulator. Manipulators play an increasingly important role not only in flexible automation production systems but also in medicine and rehabilitation process [3]. High-speed and high-precision trajectory tracking are indispensable capabilities for versatile applications of manipulators. Even in well-known industrial applications manipulators are characterized by structural and / or unstructured uncertainty. Through structural uncertainty we miss a situation in which we have a dynamic model of the object, but because of the uncertainty unknown parameters such as load, inaccuracies in constant torque actuators etc. to create a properly working control system is a difficult issue. In contrast, unstructured uncertainty is related to the unknown of the dynamic model, which may be due to many reasons such as the presence of high-frequency modes of the manipulator, neglected time-delays, nonlinear friction etc. In this case, when the dynamic model of the system is not known a priori (or not available), the system must first be identified, then the control law is developed based on the estimated model [5, [6[7].These problems cause that it is very difficult to find good control system but simple. In this case, the different algorithms for control system of the manipulator was proposed. The first classical PD controller was tested. Next the system design for PD controller with compensation of gravitational forces.

Abstract: The paper contains a description of a research into selecting drives for prototype of Continuous Passive Motion machine. Designing and constructing automated rehabilitation devices aims to increase effectiveness as well as shorten the time of a therapy. Information drew from literature, market researches and interviews in Krakow’s rehabilitation centers enabled the assessment of changes that are necessary to improve the ongoing process of automation. The article focuses on problem of designing and appropriate location of drives in accordance with durability calculations. Additionally, designing the universal machine that would allow conducting the ankle, knee and hip joint motion simultaneously, involved proper choice of drives and planning their placement, so they would not disturb the therapy.

Abstract: This paper discusses the subject of filtering range images constructed using vision systems. Construction of a range image using the laser triangulation method LTM is burdened by noise resulting from the specificity of the adopted method. This method uses structural illumination, usually in the form of a laser line from the object illumination. The image of the object is captured by a camera, whereupon the laser line image is transformed into height profiles, which are then used to construct a range image of the object. Yet, such images fail to describe the entire surface of the object, due to occlusion. Occlusion of image fragments occurs in two forms. The first one stems from the impossibility to fully illuminate all surfaces of the object, due to occlusion of the laser lines. The second form occurs when the surface is illuminated properly, but the image of this surface cannot be captured by the camera. In both cases, there is an occlusion which usually results from the shape of the object. This paper describes the method of backfilling the data in undefined areas of range images caused to the phenomenon of occlusion. It suggests a method of defining the direction of data backfilling, identification of undefined areas, as well as methods of calculating and backfilling height differences at undefined spots. The purpose of these transformations is to prepare the image for measurement and control tasks. Select examples are presented with the results of image transformation using the developed data backfilling method.

Abstract: The paper contains a description of a research into applying classic algorithm of PID controller as well as advanced Type-2 Fuzzy logic controller to ensure stability of the levitating object in magnetic field. The implemented algorithm can handle uncertainties without increasing drastically the computational complexity, which is crucial in case of PLCs. The issues concerning the construction of the unit, where the experiments were carried out, are presented, as well as the characteristics of the object for different controllers.

Abstract: In the article, a new solution of a semi-active suspension system is presented. It is based on a sky-hook strategy model. This solution in 2S1 tracked platform is applied to improve body vehicle stability and driving comfort. The solution is applied in two versions of the 2S1 vehicle suspension model. First one is a basic model. This suspension is based on existing construction of the 2S1 platform suspension. It is based on torsion bars. Second one is a modified model, based on spiral torsion springs. In this model a new solution of idler mechanism is applied. It provides constant tension of the tracks. Semi-active suspensions simulations results are compared with results of models with passive versions of the suspension to highlight the improvement level. Simulations are conducted in the Yuma Proving Ground conditions. Results of all models simulations are compared and analyzed to improve stability and comfort level in conditions of the modern battlefield. Stability level is analyzed for weapon aiming tasks. Comfort level is analyzed for the vehicle crew efficiency.