Optimization and Systems Theory Seminar

Friday November 16 at 14.00 Lindstedtsvägen 25, room 3424
Per-Olof Gutman  Technion, Israel.

Describing Function Models for Friction and Backlash and their Duality

A quasi-analytical Describing Function (DF) for the Karnopp stick-slip friction model is presented, and compared with the numerically computed DF (Baril, 1996), and with experimental measurements. Its phase lag is shown to be dictated by the static-to-dynamic friction ratio, and is generally limited to 32.5 deg. A DF for the exact physical Nordin-Gutman backlash model is presented, and compared with the numerically computed DF in Nordin (2000). The proper backlash contact condition in analytically defined in the phase-plane. It is shown that the friction and backlash models and their DFs are duals of each other, and hence the common engineering practice to fight backlash with friction has got an analytical foundation. The minimum friction level to eliminate backlash induced limit cycles is computed, as well as the minimum dither frequency to eliminate friction induced limit cycles. The DF models can facilitate robust control design, and be used in real-time adaptive control algorithms.


Calendar of seminars Last update: November 10, 2012.