As mentioned in the replies, there are a number of factors that can cause a belt to mistrack -- both external forces (idler misalignment, material buid-up on idlers and pulleys, frozen or sluggish bearings, uneven loading, load impact direction, side obstructions causing drag on the belt edges, over or under tensioning, et al) and internal forces (unevenly tensioned carcass, wavy carcass, crooked splice, belt bowing, et cetera).
There is a wealth of information available to you on belt mistraining causes and remedial actions (Mr. Mulani's book, CEMA, NIBA, most belt manufacturers, et cetera). Unfortunately there is little written on mathematical models concerning the various causes. Thus, if your thesis requires this, you will be conducting basic research and, thereby, doing the industry a favour. I would recommend that you contact belt manufacturers, conveyor manufacturers, idler manufacturers, and universities (such as the University of Hanover) to determine if they can offer assistance -- either in providing past study information or in conducting tests.
Basically, a belt reacts to the "braking" forces placed on it by the system and load, assuming good belt construction and splicing. The degree of belt reaction will depend on belt speed, load, tension, and braking (id est friction) force being applied. You should be focusing on models for each of the various mistracking causes, instead of attempting to develop an all-inclusive or unified model. For example, develop a model that shows the effect of a misaligned idler on a belt of a given weight (construction), travelling at a given speed, under a set load condition, and with a specific take-up tension. Show the effect of various misalignment angles for those conditions -- then change each of the
set conditions and repeat in turn. You can then follow this by repeating the exercise with a frozen idler and then with a sluggish idler. Further testing would be with material build-up of various amounts on one side of your test idler, through the same test range. Then do the same exercise with pulleys.
Further testing on uneven loading and impact direction would also be of use. As would side drag mistraining actions of skirting, side guide rollers, and structure contact. Finally, a study on the environmental effects of temperature, wind, moisture, dust storms, and icing would be of use.
Note that this list does not include internal causes.
Given the size of this field, you may want to limit your thesis to developing a mathematical model for just a few of the common belt mistraining causes -- my personal favorite is with the deleterious effect of over tensioning the belt, since this tends to increase the mistraining effects of all the other causes and a majority of users tend to run their belts too tight.
Good luck with your thesis, I hope to see the results in an article in Bulk Material Handling.
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