Autonomous cruise control

[ans1991]

hello, am doing a graduation project based on measuring the distance of a prototype from objects and controlling its speed ( DC motor).
i have an idea of how to measure the distance using ultrasonic sensor and 16 pic, but am having a problem in how to control the dc motor speed. Any ideas?!
Thanks in advance

 

[crutschow]

Typically you would use a PID or Fuzzy Logic control loop to provide stable control of the motor. You could use PWM to control the motor speed from that.

 

[ans1991]

yeah I thought about the PID control and i found that there is a simple way to do a hardware prototype about it ( by connecting a two PWM pins to an H-bridge )
But I was thinking is there a simple circuit other than H-bridge for example i read about using an NPN with a diode but i don't know what kind of diodes should I use.

 

[crutschow]

If you don't need to reverse the motor then you don't need a bridge and a transistor will work. The diode just needs to have voltage rating greater than the supply voltage and a current rating equal to the maximum motor current.

But PWM just allows for varying the speed of the motor, it is not a replacement for the PID control. You still need that for a stable control loop.

 

[dr pepper]

This is a 555 circuit but the fet and diode etc can be used with a pic

https://www.google.co.uk/imgres?img...c2OFaWo4ATW5oHQBA&sqi=2&ved=0CDgQ9QEwAw&dur=0

R2 would need to be a 220 ohm to keep within the pics spec, effeciency would be a little less but still fine for smaller motors.

 

[ans1991]

thank you all