Control-based compensation of friction and backlash within rack-and-pinion drives

The mechanical stiffness of rack-and-pinion drives is independent from the current positioning, which yields the advantage that even long travel distances can be realized without sacrificing dynamics. A substancial disadvantage of this kind of drive, however, is the influence of nonlinear friction effects and the occurance of backlash. Proven methods minimizing the effects of these disturbances are mechanically or electrically pre-loaded powertrains, which, by requiring mutiple drive components and causing higher wear, are cost-intesive. Within this work, the possibility of a control-based strategy to compensate friction effects, which mutually interact with backlash, is investigated. The aim is the usage of MEMS-accelerometers in order to provide a cost-effective alternative to exisiting compensation measures. Central requirements are the enhancement of positioning accuracy as well as industrial applicability. The results of this work provide a strategy, which, by measuring the current acceleration of the drive and utilizing a simplified rack-and-pinion model, counteracts the negative influence of friction and backlash effectively. As part of a theoretical analysis, stability and robustness of the presented strategy are proven. Furthermore, the results found are validated experimentally by the realization of the compensation scheme on a rack-and-pinion test rig.