Precise motion

Replies

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  flash319

  I think you are on the right track for accuracy. Your key will be feedback to the system. If you use a stepper motor you will be limited to the steps that it can take. This must be considered. You will have to match your resolution of feedback to the capabillity of the motor or drive system. If you couple a high step (micro stepping motor) to a ball screw with a very high resolution optical scale you will have a very accurate device. A linear optical scale (used in CNC tables) will give .0001 of an inch if you spend enough money.
• 

  Destiny

  Hey flash319!
  
  Thanks for an answer.
  I nearly thought I will get no answers at all...
  
  Anyway, things moved slightly further and I now know that the movement will not be more than 10mm, but not less than 5mm.
  The type of precision you suggested, flash, though is far too much.
  The whole 'system' will look similar to this:
  
  -lowering down, until feedback of pressure exerted onto the flat surface haven't reached our limit (couple of psi max)
  - keep it there for a certain period of time
  - take it back up at a constant rate to the start position.
  
  I found some linear stepper motors as well as servos used in rc models but I am not sure about their power capabilities. The weight that might be required to 'move' shouldn't exceed 500g.
  
  I was also thinking about memory wires yet I can see some problems with controlling them, as well as maintaining constant speeds...
  
  Any more comments are welcome!
  Thanks!
• 

  flash319

  Sounds like you are more interested in rate then precision. A stepper motor with a microstepping drive will do what you want. You can set the step rate to whatever you want. You can also set acceleration and deceleration curves. Some drives will give you current feedback and through this you can figure out how much pressure you are applying as well. AC servo motors are better at that task but are more expensive and complicated to get working.
  
  Since you are moving such a small amount you may be able to find a linear motor that will do what you want. This all depends on how large the setup is going to be.
• 

  Destiny

  Thanks!
  
  The only problem is that I cant use AC motors... since the whole thing needs to be portable and I want to use batteries to power it. Recharchables, standard alkaline or something else.
  
  Setup shouldnt be any bigger than lets say... a 14V power drill, without the handle...
• 

  flash319

  I would say that you can probably just take a printer apart and you will have everything that you need. The drive for the print head will be running on a stepper motor and you will also have the drive screw. You may be able to use the control as well. Just write some code into a PIC to make it do what you want. A PIC can also do the stepping for you.😁
• 

  Destiny

  Yeah I know about pics. Useful little things 😉
  I'll check the printer though 😀 good idea 😀 thanks!