Mechanics
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ISSN 1734-8927
e-ISSN: 2300-7060
Issue Date
2008
Volume
Vol. 27
Number
No. 3
Description
Journal Volume
Mechanics
Vol. 27 (2008)
Projects
Pages
Articles
Experimental construction of walking robot
(Wydawnictwa AGH, 2008) Babiarz, Artur; Jaskot, Krzysztof
The paper presents an experimental construction of six legs walking robot. In the paper, we consider problem of control six legs robot with eighteen servomotors. Each of the legs is equipped in three servomotors what mean 3DOF (degree of freedom) per leg. Using multiprocessor architecture, one microcontroller for servo control and one for analyse data from sensors are described. Mobile robot is a machine that can operate in a human-made environment. By control, in this case we will understand to be able to avoid collisions with obstacles during walk in unknown environment. Legs movement algorithm is described. Presented algorithm generates movement of legs with surface detection. All of presented algorithms were written in C language. Results of real application are also shown. Preliminary results of work on fully autonomous walking robot that can operate in human environment are presented.
Influence of nonlinear foundation on Timoshenko beam vibration
(Wydawnictwa AGH, 2008) Bar, Adam; Bar, Olaf
The goal of this paper is presentation of the physical properties of the thick beam on nonlinear foundation with infrequent analyzed free boundary condition. Galerkin's method with two-elements basis is applied. This paper justifies this choice too. Nonlinear effects such as internal resonance and discontinuous of amplitude frequency characteristic is observed. The proper choice of parameters ensures the ratio first to second natural frequencies equal to 3. This is one of the conditions satisfying existing of the internal resonance. In the amplitude-frequency characteristic near first resonance there appear breaks and their numbers grows with the increase of nonlinearity of the foundation.
Fuzzy logic controller for one-way SMA actuator
(Wydawnictwa AGH, 2008) Dominik, Ireneusz; Kwaśniewski, Janusz
Fuzzy logic controllers are well known and often used for their ability to control nonlinear objects in an easy and efficient way. In the article fuzzy logic controller was chosen to control displacement of one-way actuator where the movement in one-way was realized by SMA wire while an external load was responsible for the way back. The SMA wire is characterized by one of the highest in technology weight ratios, which describes the ratio of maximum external load to its own weight. It allows for building miniature devices which are extremely efficient. Mostly SMA wires are applied as on-off actuators. Having built a test stand with SMA wire the research on selection of an appropriate method control was launched to control displacement. Eventually a fuzzy controller was implemented into PLC controller made by Omron. On that way in future it will be easier to emigrate from the PLC platform to a dedicated embedded microprocessor. The fuzzy controller was built as a task controller, where the specialized controllers for particular stages of the systems' operation were distinguished. They allowed for accurate and fast SMA wire control. The design controller allows for position control with +/- 0.1 % accuracy with time response below 0.4 s.
Simulation of fatigue process
(Wydawnictwa AGH, 2008) Kuffova, Mariana
In the paper are shown the results of fatigue crack propagation in the microstructure of material and the dependence da/dN - DKapl by finite - element software ADINA. These results are confronted with the results of fatigue tests. The aim was to elaborate on the crack initiation and growth in the microstructure containing a stress concentrator and redistribution of stress during propagation.
Active noise control with moving error microphone
(Wydawnictwa AGH, 2008) Michalczyk, Małgorzata
Electro-acoustic plants controlled by active noise control (ANC) systems in enclosures are usually time-varying. Their changes can be caused by movements of an error microphone, around which zones of quiet are created. Then, the time variations of the electro-acoustic plant can be fast and adaptive ANC algorithms for tracking variations of error microphone position should be used. The preliminary research results showed that the created zone of quiet can move tracking the movement of the error microphone, when filtered-x least mean squares (FX-LMS) algorithm is applied. The paper presents further results of real-world experiments conducted on a special laboratory stand, which enabled to move the error microphone round the circle trajectory with constant rota- tional speed. Two modifications of FX-LMS algorithm were applied in order to accelerate control algorithm convergence and improve tracking properties of the ANC system: normalized FX-LMS and modified FX-LMS algorithm. It was shown, that the zone of quiet can track movement of the error microphone, however, there was no significant difference in control algorithms performance. In all cases the zone of quiet tracked the movement of the error microphone, even for the error microphone velocity as high as 3.7 m/s, and high attenuation was obtained - from 16 dB for the fast microphone movement up to 28 dB for the slowest microphone movement.