UNIVERSITI KUALA LUMPUR

MALAYSIA-FRANCE INSTITUTE

CONTROL SYSTEM 2

(LAB REPORT 1)

(Feedback Control of Magnetic Levitation System)

PREPARED BY:

MOHD SYAFIQ HILMI BIN HASAN PEKRI 50213107236

MOHD ZAIRIL AZWAN B IDRIS 50213208169

MCA082D2

PREPARED FOR:

MR. YUSOF MOHD EKHSAN

DUE DATE:

04/10/2010

Objective

To know wheater magnetic levitation system are stabilization of the open loop system and close loop system

To know how the implementation based on the feedback control of magnetic levitation system

To observe the stability of the magnetic levitation system using both of feedback system and the reaction to vibration.

Tools

1. Magnetic Levitation Module2. Dual-channel power supply (+12Vdc and -12Vdc)3. Neodymium magnet (2 pieces)4. Object (1 piece of small rectangular box, 2 pieces of metal screws)5. Multimeter6. Oscilloscope

Experiment 1: Open loop system

Procedures:

1. First we set the Jumper on the control board to Open Loop.2. Second turn on power supply to +12Vdc for channel-1, and –12Vdc for channel-2.

Connect the power supply to the hardware module.3. Next take one piece of the small Neodymium magnet then attach it to the load provided4. Then please hold the load by your hand and slowly move it up towards the electromagnet,

keeping it directly below the center of the coil. Hold it about 1/2” from the coil.5. Try to levitate the load by adjusting the potentiometer on the Controller Board. If you feel

a strong pull/push when turning in one direction, adjust the potentiometer to the reverse direction until the forces (magnetic against gravity) are balanced.

Experiment 2: Close loop system

Procedures:

1. First we set the Jumper on the control board to Closed- Loop.

2. Then slowly move the load up towards the electromagnet, keeping it directly in line below the center of the coil.

3. Next within about 1/2" you should begin to feel a slight push or pull. Three things need to be in the correct magnetic polarity relative to each other in order to achieve levitation: the coil, the Hall Effect Sensor, and the suspended magnet. If your magnet pulls toward the coil, try reversing the magnet. The correct combination is when the load will be pushed away when it gets closer to the coil, and attracted when it gets further from the coil.

4. Once the polarities are right you will feel the magnet “grab” as it enters the optimumspot under the coil. At this point, let the load go very gently.If it pulls up and sticks to the coil, you will need to add more weight. If it falls away,your load is too heavy. If it bobbles up and down, add some ferrous metal to thesuspended magnet - like some small washers. This will damp the magnetic reactanceof the circuit. The range of viable weights is limited by any given combination ofelectromagnet and permanent magnet, so be prepared to do some of testing andchanging of weights.

5. Then increase the weight of the load slightly by adding metal screw/s at the bottom ofthe rectangular box

6. Lastly attach two pieces of the Neodymium magnets together and stick them to the load

Results and discussions

Experiment 1-1: Open Loop System

Yes. It is possible to levitate the magnet by using open loop control by adjusting the potentiometer to the reverse direction until the forces (magnetic against gravity) are balanced.

Levitate one magnet attached with a small rectangular box by using open loop control.

Experiment 1-2: Close Loop System

Table 1: MLS observations

Load Stability(Stable/ marginally stable/unstable)

Reaction to Vibration(Bobble/ stabilize/ etc.)

1 magnet + 1 rectangular box stable Bobble

1 magnet + 1 rectangular box + 1 screw

stable Bobble

1 magnet + 1 rectangular box + 2 screws

stable Unstable

2 magnets + 1 rectangular box

stable Bobble

2 magnets + 1 rectangular box + 1 screw

StableBobble

2 magnets + 1 rectangular box + 2 screws stable Bobble

Question Answers:

1. Draw the control system block diagram of the MLS. Indicate the reference input, controlled

output, controller Gc(s), plant G(s), feedback sensor H(s) an etc.

Block diagram of the Magnetic Levitation System

2. Measure the waveform of the PWM controller output at pin 7 of IC MIC501 at no load and with load condition. Identify the waveform’s frequency and duty-cycle for both conditions.

With load : There is a step response with square waveform with 4V amplitude at 2.5 ms.Without load : There is a straight line at 0V

3. Explain why the waveform measured above differs.

When the magnet is attached, the current charged is changing. There are currents charged when the magnet is attached to the solenoid. The electromagnet can be proportionately controlled from full reverse to full forward current. If the input signal is at 50%, then the net effect is equal attraction and repulsion of the suspended permanent magnet. If the permanent magnet moves further away from the Hall sensor, the duty cycle changes to a higher ratio that attracts the magnet. If the permanent magnet moves closer to the Hall sensor, the duty cycle changes to a lower ratio that pushes the magnet away. So, with more load, more current needed for solenoid to increase the magnetic force.

4. What happens when we introduce a disturbance on the levitated object? What does this say about the stability of this system?

The levitated object will bobble or in the word it was unbalance or unstable (moving up and down or left or right). At sufficient high rate of movement, a suspended magnet will levitate on the metal, or vice versa with suspended metal. Halbach arrays are also well-suited to magnetic levitation and stabilisation of gyroscopes and electric motor and generator spindles.

5. Explain how to increase the MLS levitation capacity such that it can levitate more weight?

By passing a certain amount of electric current through the electromagnetic winding, it will generate an electromagnetic force. By regulating the electric current in the circuit, the electromagnetic force can be adjusted to be adjusted to be equal to the weight of the load, thus the load will levitate in equilibrium state. So, in order to increase the MLS levitation capacity, we must increase the voltage through the system. With high voltage, more current will flow through the solenoid and then increase the electromagnetic force.

Conclusion:

From this experiment, we can concluded that by passing a certain amount of electric current through the electromagnetic winding, it will generate an electromagnetic force. By regulating the electric current in the circuit, the electromagnetic force can be adjusted to be equal to the weight of the load, thus the load will levitate in equilibrium state. Pulse Modulation Modulated (PWM) controllers are used to make use of the position sensor signal, we need to drive an electromagnet with a PWM signal. A repeating pulse changes it’s width to apply more or less power to the device over time.