Advance Modeling of a Skid-Steering Mobile Robot for Remote ...
Advance Modeling of a Skid-Steering Mobile Robot for Remote ...
Advance Modeling of a Skid-Steering Mobile Robot for Remote ...
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6.2 Simulation Results 96• For λ max = 10 −3 , 10 −4 , the main peak frequency is the at same frequency <strong>for</strong> all thethree accelerometer axes, i.e. a x , a y , a z . Such a peak frequency seems to increase withthe angular velocity up to 20 Hz, <strong>for</strong> relatively low angular velocities (ω z < 20), while itremains almost constant at ¨low¨ frequency <strong>for</strong> relatively high angular velocities (ω z >20).• For λ max = 1, the amplitude <strong>of</strong> the vibrations linearly increases with the angular velocity<strong>for</strong> a y , while it remains almost constant at relatively low value <strong>for</strong> a x , a z .• For λ max = 10 −1 , 10 −2 , the amplitude <strong>of</strong> the vibrations linearly increases and then remainsalmost constant, respectively at low (ω z < 20) and high (ω z > 20) angularvelocity <strong>for</strong> a y , a x , while it remains almost constant at relatively low value <strong>for</strong> a z .• For λ max = 10 −3 , 10 −4 , the amplitude <strong>of</strong> the vibrations remains almost constant at relativelyhigh and low value respectively <strong>for</strong> a y and a x a z .• For all the tested cases, the amplitude <strong>of</strong> the vibrations is much smaller than the amplitudes<strong>of</strong> the real robot vibrations acquired from the accelerometers.Finally, we can claim that the overall model qualitatively reproduces the frequencies butnot the amplitudes <strong>of</strong> the real vibrations measured by the accelerometers. In particular, thevalue <strong>of</strong> λ max , which allows the model to be ¨closer¨ to the real system behavior, seems tobe <strong>of</strong> an order <strong>of</strong> magnitude <strong>of</strong> 10 −1 , 10 −2 . However, by comparing the graphs in AppendixB and C and taking into account the considerations made in Section 3.2, we notice that themodel does not quantitatively reproduce the amplitudes and frequencies <strong>of</strong> the real robotvibrations yet. The reasons <strong>of</strong> such a discrepancy might rely on the lack <strong>of</strong> an identification<strong>of</strong> λ max or on the irregularities <strong>of</strong> the ground surface.Thus, we conclude saying that, in order to validate the model also from a quantitative point<strong>of</strong> view, an accurate identification/estimation <strong>of</strong> the maximum wheel slip λ max is needed. Ifafter such identification the model is still inaccurate <strong>for</strong> our needs, we can either try to modelthe irregularities <strong>of</strong> the ground surface or propose another model.