The idea of this project is how to control the angle of a free pendulum using LabViw and Data Acquisition Card.
After a lot of thinking about the source of force, and after some advices form friends, we use a very tiny DC motor as a fan. This DC Motor is controlled using a PWM wave generated by DAQ.
The center of rotation of this arm is an Angle sensor, It is a variable resistor feeding back a voltage related to the angle.
The over all explanation will be in this topic
The force affects the arm cases a toque, this toque rotates the arm about the center of rotation. Our force is the air pressure from the fan, The force generated by this fan is directly proportional to the speed of it.
After the previous introduction, the speed control is a force control multiplied be a constant factor. We can not derive this factor because the difficulty of aerodynamics of this fan. This problem is solved using a feedback angle value.
PWM wave generated by the DAQ interfaced by LABView is used, this wave is connected to the gate of a MOSFET Driver with 20V DC-supply.
The main idea is to control the duration of the PWM due to theta calculated.
If theta calculated is smaller than theta desired, then the PWM duration will be increased automatically, and visa versa.
By this way, if some one affect on this arm by any small load, theta will be changed, and the PWM controller will work hardly to put the system on the theta desired
The variable resistor is enforced using 5V DC-supply which is supplied the DAQ.
The value of the output voltage is proportional to the position of arm. In minimum case, the output voltage is zero and the maximum is 5V.
So, the following illustrate this idea
0 V Υmin
5 V Υmax
labview 8 with DAQ 6024E:
In our Project , we use the labview 8 to interface with DAQ 6024E , and we use analog input which index 33 ACH1 with pin 8 ( +5 V) and 7 ( DGND ).