Razvoj modela za ocenu oscilatorne udobnosti vozila

Abstract

Oscilatorna udobnost vozila, kao kompleksan problem, poslednjih nekoliko decenija privlači pažnju velikog broja istraživača. Razvojem industrijskih mašina i motornih vozila, počela su proučavanja negativnog uticaja dejstva vibracija na telo čoveka. Dugotrajno izlaganje vibracijama u različitim pravcima delovanja, frekvenciji ili amplitudi, prvo počinje malom neudobnošću, a kasnije dovodi do smanjenja radne sposobnosti i ugrožavanja zdravlja. Biodinamička istraživanja ponašanja tela čoveka, pored subjektivnih metoda, imaju veoma važnu ulogu u analizi i predviđanju oscilatorne udobnosti vozila. Ova istraživanja su veoma korisna, jer s jedne strane omogućavaju formiranje biodinamičkih modela, dok sa druge strane omogućavaju analizu vibracija koje se prenose na telo vozača i putnika. Biodinamička funkcija frekventnog odziva sedište-glava STHT (eng. Seat-to-head transmissibility - STHT) opisuje meru prenetih vibracija kroz telo vozača i kao takva je korišćena kao objektivan pokazatelj oscilatorne udobnosti. U okviru sprovedenih istraživanja, a u cilju generisanja slučajnih širokopojasnih vibracija, korišćen je hidraulički pulzator. Ispitanici (20 muškaraca i 10 žena) su bili izloženi slučajnim širokopojasnim vibracijama celog tela u pravcu jedne ose (podužno ili vertikalano) i u pravcu više osa (istovremeno u podužnom i vertikalnom pravcu). Amplitude pobude su varirane (0,45 m/s2 ; 0,8 m/s2 i 1,1 m/s2 r.m.s. - efektivna vrednost) u frekventnom opsegu 0,1 Hz - 20 Hz. Proučavan je uticaj promena uglova nagiba naslona sedišta (90°, 100° i 110°) na STHT odziv tela čoveka. Dobijene funkcije frekventnog odziva tela pomogle su u identifikaciji relevantnih faktora koji imaju najveći uticaj na oscilatornu udobnost vozača. Na osnovu dobijenih eksperimentalnih rezultata formiran je model za ocenu oscilatorne udobnosti vozila pomoću rekurentnih neuronskih mreža. Model uzima u obzir pol, antropometrijske karakteristike ispitanika, karakteristike pobude (amplitudu, frekventni opseg i pravac dejstva), kao i uslove sedenja. Koeficijent korelacije između eksperimentalnih rezultata i rezultata modela neuronske mreže je bio preko 98% u sve tri faze (treninga, validacije i testiranja). Prednost ovakvog modela je u tome što, na bazi velikog broja podataka kojim je model obučen, on ima mogućnost da predvidi funkciju frekventnog odziva tela čoveka za bilo koju vrednost amplitude, pravca pobude i ugla nagiba naslona sedišta i da na osnovu efektivnih vrednosti ponderisanog ubrzanja (primenom standarda SRPS ISO 2631–1:2014), izvrši ocenu oscilatorne udobnosti ispitanika.

Oscillating vehicle comfort, as a complex problem, has attracted the attention of a large number of researchers in the last few decades. The development of industrial machines and motor vehicles has begun to study the negative impact of vibrations on the human body. Prolonged exposure to vibrations in different directions of action, frequency, or intensity, first begins with a small discomfort and later leads to a decrease in work ability and endangering health. Biodynamic studies of human body behavior, exposed to whole body vibration, in addition to subjective methods, have a very important role in analyzing and predicting the oscillatory comfort of vehicles. These researches are very useful, because on the one hand they enable the formation of biodynamic models, while on the other hand they enable the analysis of vibrations transmitted to the body of the driver and passengers. The biodynamic seat-to-head transfer function (STHT) describes a measure of transmitted vibrations through the driver's body and as such has been used as an objective indicator of oscillatory comfort. A hydraulic pulsator was used in order to cause random wide-band vibrations. Subjects (20 men and 10 women) were exposed to random broadband broadband vibrations to single axis (fore-and-aft or and vertical) and to multi-axis (simultaneously foreand-aft and vertical). Excitation amplitudes were varied (0,45 m/s2 , 0,8 m/s2 and 1,1 m/s2 r.m.s. – root mean square) in the frequency range 0,1 - 20 Hz. Тhe influence of changes in the angle of inclination of the seat back (90°, 100° and 110°) on the STHT response of the human body was studied. The obtained frequency response functions of the body helped to identify the relevant factors that have the greatest influence on the oscillatory comfort of the driver. Based on the obtained experimental results, a model for evaluating the oscillatory comfort of the vehicle using recurrent neural networks was created. The model takes into account the gender, anthropometric characteristics of the subjects, characteristics of excitation: amplitude, frequency range and direction of vibration, as well as sitting conditions. The correlation coefficient between experimental results and neural network model was over 98% in all three phases (training, validation, testing). The advantage of such a model is that, on the basis of a large amount of data with which the model is trained, it has the ability to predict the frequency response function of the human body for any value of the amplitude and direction of excitation, the angle of the seat back and the basis of the effective values of the weighted acceleration (using the standard SRPS ISO 2631–1:2014), evaluate the subject's oscillatory comfort.