Abstract: The efficiency of creating and designing noise reduction measures greatly depends on physical, chemical, mechanical and other properties of the selected materials. Some of them and sometimes all of those have a big impact on the general sound insulation of designed measures that also include absorption values predetermining their efficiency.As has been known for a long time, the formed heavy partitions and elements acquire increased sound insulation according to the law of mass, i.e. the heavier is the weight per m2 of the surface (kg/km2), the higher is the sound of insulation.To increase the efficiency of noise reduction in barriers, it is necessary to search for some other properties of the material like design, quality, etc.The article describes how calculations and empirical manipulations facilitate finding an optimal complex construction effectively reducing noise.
Abstract: The article presents a new approach to the sensor-based navigation of wheeled mobile robot Pioneer 2-DX in the unknown 2-D environment with static obstacles. The navigation task has been developed using a discrete hierarchical control system with a path planning layer and a tracking control layer designed using approximate dynamic programming algorithms. The navigator realises a behavioural control approach to the path planning process using the adaptive coordination of two simple behaviours: “goal-seeking” and “obstacle avoiding”. The main part of the navigator is the Action-Dependant Heuristic Dynamic Programming structure realised in a form of the actor and critic neural networks. To avoid the time consuming trial and error learning, additional proportional controllers generating signals that prompt the direction of the sub-optimal control law seeking process at the beginning of the NNs adaptation process are arranged in the navigator. The tracking control layer is composed of a PD controller, the Dual Heuristic Dynamic Programming algorithm and a supervisory term. It generates control signal for DC motors of the robot. The performance of the proposed discrete control system was verified by a series of experiments conducted using wheeled mobile robot Pioneer 2-DX equipped with one laser and eight ultrasonic range finders that provide object detection.
Abstract: Electric catapults can be used for automatic information storage in radioactive environment. Dynamics of a transport system with the potential of route flexibility was investigated. This system is made up of stand-alone modules, therefore further expansion is possible. Modules consist of mechanical part (rails for the cart), electrical part (inductor of a linear induction motor (LIM) and electromagnetic brake) and electronic part (thyristor commutator). Cargo cart is mounted on the LIM’s secondary unit that can be catapulted from any station (module) to another. First LIM’s inductor starts the secondary, ejects it out of primary’s range. Inertia of the cart allows it to reach the next station which in turn can either accelerate it or stop it. Position detectors (Hall effect sensors) are used for estimating cart movement. Electromagnetic brakes are used as dynamic braking is not effective in this case. A computer model was designed and various operating modes are simulated (upon non-zero initial conditions).
Abstract: The paper presents an estimation analysis methopd for the natural mode and frequency of the torsional vibrations of a marine power transmission system. A typical merchantman marine propulsion system is made up of a slow speed main engine connected to a directly driven propeller by a relatively short shaft line. Although all classification societies require calculating the operating parameters of the propulsion system, however, they have no simplified formulas. The torsional vibrations of the marine power transmission system are usually the most dangerous for the shaft line and crankshaft. Numerical algorithms based mostly on the Finite Element Method (FEM) are unobtainable and not useful for a ship crew. The chief of marine engineers should have checked a possibility of the analysis and measurements of torsional vibrations. The authors have investigated an estimation method of the torsional vibrations of the system. The article deals with a simulation method for more difficult parameters of the propulsion system like propeller water added mass moment of inertia. The paper also briefly describes the advantages and disadvantages of the undercritical and overcritical propulsion system and discusses calculation results included in the final part of the work. The introduced calculation method has been verified comparing detailed FEM estimations and the measurements of real ships.
Abstract: The work considers using a multilayer elastomeric package for the vibroisolation of engineering constructions under the action of periodic vibration. The multilayer elastomeric package is located between the protected object and a vibrating base; it consists of alternating thin metallic and elastomeric layers jointed by vulcanization or gluing. The paper discusses flat rubber-metal elements of circular shapes with reinforcing steel layers and describes kinematic excitation directed flatwise. The analytical expression of the characteristics of the compression stiffness of the plane multilayered elastomeric structure is derived on the basis of the variational principle, and metallic plates-layers are assumed to be perfectly rigid. An analytical solution was confirmed by experimental data. The fitted equation for “force-displacement” was derived and used in the equation of motion on of the protected object.
Abstract: One of the indirect tensile identification methods is the measurement of the structure of the response to the vibration excitation. Then this response is simulated using digital methods. If the similarity to the response structure is achieved, the elasticity parameters can be determined. Using the methodology discussed in this work, the problem of the determination of the elasticity parameters of prints as a consisting of the paper and several layers of inks is solved. The determined parameters of prints will be used for the modeling of the printing process in web printing presses.
Abstract: Rotary systems are frequently used in different kinds of machines and devices, and therefore the problem of vibrations observed in rotary systems play a crucial role. The article analyses a ball-shaped auto-equalizer with a vertical axis the body of which is placed relatively eccentric to the rotation axis. The auto-equalizer with a torus-shaped body contains one ball-shaped adjustment mass moving freely within the body of the auto-equalizer both in circularly and crosswise directions. This reduces resistance force in the ball motion mode to the minimum, and, at the same time, decreases the possibility of starting the auto-equalizer.Making the analysis of experimental research on the ball-shaped auto-equalizer has led to the conclusion that, along with the working mode when the ball stops relatively at the rotating body from the opposite to imbalance side, there is another mode when the ball is moving relatively continuously to the body of the auto-equalizer. It has been stated that the ball in the working mode is affected by forces trying to move it to the body of the auto-equalizer opposite to the imbalance. The closer is the ball to the optimum place the smaller is tangential force influencing the ball. A mathematical model for the auto-equalizer consisting of two differential equations has been developed.
Abstract: The paper presents a method that enables a race of a real mobile robot following the path defined by Catia software. On the basis of the performed simulation, the parameters necessary for task realization have been obtained and combined into a matrix, then importing and implementing them into the mobile robot. Exemplary experimental research on P, PI and PID regulators with a turbine switched off and on P regulator with a turbine switched on has been carried out.
Abstract: The results presented in this paper describe a practicable solution to multi-rotor platforms constructed and put together with standardized components to allow flexibility and customizability. The extensive utilization of universal parts supports an easy introduction of changes in case of necessary design alterations and speeds up the whole process when constructional changes are required. The research has been applied to a variety of special use multi-copters and has proven to be very useful. Further development will follow to secure subcomponents with necessary Ingress Protection ratings and even further optimize universal components. The constructional layout of multi-copters is relatively simple and usually consists of the main middle frame that houses control electronics, batteries and payload fastenings. Protruding boom arms have motors mounted in the tips and power cables running inside. The frame, payload and boom arms are generally fastened with hexagonal socket head cap screws, which means that assembling and disassembling takes a notable amount of valuable time when setting the UAV up on the field. For this reason, modularity and rapid assembling are needed.Fig. 1. Multi-rotors performing ice-bank and high-rise inspection
Abstract: The paper presents the structure of a precise parallel tri-axle manipulator with the functionality of progressing-tilting table. The end effector of the device is a platform, for which three coordinates of position are defined. The manipulator has three degrees of freedom: movement perpendicular to the base and rotation in two mutually perpendicular axes contained in the surface parallel to the base.The concept of the positioning mechanism is based on parallel tripod kinematics where the end effector – the platform – is seated on three active limbs – actuators. The use of parallel kinematics allowed modular construction of the positioning mechanism. The developed modular functional mechanism with minimal number of elements in kinematic chain ensures high positioning resolution. The concept of application of eccentric mechanism for platform positioning is an original idea in this solution. The compact construction allows applying the manipulator in medical devices that require meeting of the hygienic conditions in the medical test and research laboratories. The possibility of the utilisation of the precise manipulator covers wide areas of science and technology where precise positioning of the object is required, e.g. sample positioning for microscopes, scanning systems.