Modeling and Sliding Mode Control for a Small Scaled Magnetic Levitation Mechanism

• Main Authors: Wei-Lun Kao, 高偉倫
• Other Authors: Wu-Chung Su
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/72616031580062403489

碩士 === 國立中興大學 === 電機工程學系所 === 101 === In this thesis, a position tracking controllers for a magnetic levitation system is developed. The plant consists of a solenoid and a ball made of steel. The solenoid is wounded by a coil, which is energized with a PWM current drive for levitation force control. The position of the ball is sensed optically by a laser range finder. A magnetic levitation system is intrinsically unstable and nonlinear. We first derived the linearized dynamic model and then validated the model by experiments. The control design is carried out with two steps－the inner-loop current control and the outer-loop position control. In the inner-loop control, the current is passed through a low-pass filter, compared with the command current, and then accomplished the current control objective by sliding mode. For the outer-loop control, there is a laser sensing system for the detection. The command current is first determined by a PI controller. Thus the coil of the electromagnet produces a magnetic force to balance the gravity of the steel ball. These controllers are realized by a digital signal processor.