tailieunhanh - Vibration Control Part 5

Tham khảo tài liệu 'vibration control part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Vibration Isolation System Using Negative Stiffness 89 Electromagnet Hybrid magnet Base Air bearing Table Permanent magnet Fig. . Schematic drawing of experimental apparatus Middle mass Sensor Coil spring Fig. . Photo of experimental apparatus Apparatus. Figures and are a schematic diagram and a photograph of a single-axis apparatus that was built for experimental study. The height diameter and mass of the apparatus are 200 mm 226 mm and 18 kg respectively. The isolation table and the middle mass weigh kg and 5 kg respectively and are guided to move translationally in the vertical direction by linear air bearings. A ring-shape electromagnet with a 448-turn coil is fixed to the middle mass its inner and outer diameters are 68 and 138 mm respectively. Ten 10 X 10 X 5-mm permanent magnets made of NdFeB provide bias flux. These magnets rather than the electromagnet are built in the reaction part of the isolation table. The nominal gap between the electromagnet and the permanent magnets is about 3mm. The middle mass is suspended by four mechanical springs. An electromagnet for adjusting the positive stiffness 90 Vibration Control k1 and the damping C1 is installed on the base and its reaction part is built in the middle mass. The electromagnet is referred to as an auxiliary electromagnet and is used to equalize the positive stiffness and the amplitude of the negative stiffness in the following experiment. The relative displacement of the middle mass to the base and that of the isolation table to the middle mass are detected by eddy-current gap sensors. In the experiments we use a zero-power controller in the form of i - Pd Pv x2 - x1 Pi Iidt. dt This is a combination of PD proportional-derivative control and a local integral feedback of current Mizuno Takemori 2002 . Equation states that I s - s P PvS X2 s - X1 s -C2 s s X2 s - X1 s s - Pi The designed control algorithm is implemented with a digital controller. The control period is 100ps.