Abstract
Compared with rotary motors, linear motors possess many advantages in linear motion driving applications, such as direct driving, low frictional loss, high position control accuracy, high speed, high acceleration and deceleration capability, maintenance free and large structural flexibility, …, etc. In this thesis, the position control of a linear brushless DC motor (LBDCM) drive system is studied. First, an one-dimensional table driven by LBDCM is established, wherein the Hall-effect sensors and linear encoder are employed to obtain the position information of moving member. For obtaining good position driving performance, a current-controlled voltage source inverter (VSI) with lowly-distorted sinusoidal output current is developed, the commutation instant tuning of inverter to yield better force generating capability of a LBDCM is also studied. It is known that the dynamic model is indispensable for performing the controller analysis and design. In this thesis, the dynamic modeling of LBDCM is described. According to the estimated motor drive dynamic model at nominal case, a two-degree-of-freedom controller (2DOFC) is first designed to meet the prescribed position tracking and load regulation responses. As the system parameter and operating condition changes occur, the given control requirements will not be satisfied further. A robust controller (RC) and an output feedback linear model following controller (MFC) are further developed to reduce the degradation of performance. The control performance comparison between these two types of position controllers is made. After confirming the validity of the designed controllers by some simulations, the realization of controllers is made and the driving performances of the whole linear motor drive are demonstrated by some measured results. Finally, a ramp position command with suitable changing rate is generated to avoid the occurrence of speed limitation, and thus the overshoot of position response due to large step command change can be eliminated.