ผลของขนาดและความถี่ของสัญญาณอินพุตความถี่สูงที่มีต่อความเสียดทานในระบบทางกล / ภิญโญ ศรีคำแหง = Effects of amplitude and frequency of dither input on friction in mechanical systems / Phinyo Srikamhang
The study investigates the effect of amplitude and frequency of dither for friction compensation in mechanical plant. The thesis focuses on the control of system positioning of which the friction is highly nonlinear and discontinuous around a reference point; in particular, the effects of dither on the friction-induced steady state error. In addition, the model based friction compensation is incorporated into the dither based technique such that the friction effects are minimized. The experiments on three different mechanical systems, i.e. ECP 220 plant, Comdyna 767 and CRS robotics system, are used to study the step response and the resulting steady state error. Additionally, the ECP 220 plant is also simulated. The results show that the dither signal significantly reduces the steady state error while the model based friction compensation reduces the response time constant. Both techniques can be integrated to simultaneously decrease both error and time constant. The study on CRS robotics system demonstrates that the dither amplitude should exceed the maximum static friction while the dither frequency should fall within the bandwidth of the system. Otherwise, the dither may not effectively compensate the friction, yielding no reduction of the steady state error.
