1. MagneticSystem Using Discretize Low Pass Filter
Student : Chin yi.Kuo

2. O u t l i n e MagneticSystem Hardware Introduction Flow diagram
Discretize Low Pass Filter
Low Pass Filter for cutoff frequency
Compare with/without LPF results
Polynomial Curve Fitting
Magnetic Levitation 1-6mm Figures

3. H a r d w a r e Power Amplifier Electromagnetic coil ADC DAC Position
Sensor
Power Supply

4. Voltage conversion equation with position
F l o w d i a g r a m
ADC
Using Discretize LPF
Voltage conversion equation with position
DAC
Power
Amplifier
Using Discretize LPF
Electro
Magnetic
coil
PID Controller

5. L o w P a s s F i l t e r ISSUE： MagneticSystem unstable
A to D , Noise disturbance
PID-controller , D control → oscillation
Solution：
Add Low pass filter to program
Represent the low-pass filter as：
# Familiar transfer function of LPF.
# K =ω (rad/s) = 2 π f

6. Discretize L o w P a s s F i l t e r
Bilinear Transform：
Using in digital signal processing and discrete-time control theory
to transform continuous-time system representations to discrete-
time vice versa.
Discrete-time approximation

7. Using equation in program
T(s)→T(z)：
(前一次輸入+目前輸入-前一次輸出)
Using equation in program

8. Low Pass Filter for cutoff frequency
No Low Pass Filter
of reading Voltage
Filter frequency
：1000Hz

9. Filter frequency
：500Hz
Filter frequency
：100Hz

10. Filter frequency
：70Hz
Filter frequency
：10Hz

11. Input Without Low Pass Filter

12. Output Without Low Pass Filter

13. Without Low Pass Filter

14. Using LPF to program After ADC & Before DAC

15. Polynomial curve fitting
Position correspond to voltage DATA

16. First degree
5th degree

17. Curve fitting coefficients(A、B 、C 、D 、E 、F)

18. 1-6mm Magnetic Levitation
Airgap_1mm
Airgap_2mm
Airgap_3mm
Airgap_5mm
Airgap_6mm
Airgap_4mm

19. Thank You