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Robotic Gripper — Parallax Forums

Robotic Gripper

Aj53Aj53 Posts: 3
edited 2014-04-14 10:14 in Robotics
What do you command the motor of a gripper when you want to grip an object.
i mean once the object is gripped , and still the motor is running then, this will result in stall current.
Do people usually turn off the motor after gripping the object?
If yes, then isnt there a possibility of the object slipping off?

Comments

  • Martin_HMartin_H Posts: 4,051
    edited 2014-04-13 03:11
    Is this an RC servo gripper, or something else?

    I've found that RC servo grippers drop what they're holding when you turn the motor off. So I use the pulse width that is close to the diameter of the object to avoid gear strain.

    If a gripper used a worm gear then you could cut power and it would still hold, but I don't have one of those.
  • Aj53Aj53 Posts: 3
    edited 2014-04-13 08:15
    Martin_H wrote: »
    Is this an RC servo gripper, or something else?

    I've found that RC servo grippers drop what they're holding when you turn the motor off. So I use the pulse width that is close to the diameter of the object to avoid gear strain.

    If a gripper used a worm gear then you could cut power and it would still hold, but I don't have one of those.

    But will using a pulse width that is close to diameter of object will also result in stall current, right?
    And in case of worm gear , will it experience gear strain if we cut power?
  • Martin_HMartin_H Posts: 4,051
    edited 2014-04-13 09:13
    I've never measured it, but I think the current would be lower. This is because the servo motor controller has a proportional control scheme, and it increases motor power as the difference between the pulse width and position is larger. This is why CR servos run faster as the control pulse widths get further from the neutral pulse width. But a DMM should let you measure this.

    When you cut power to the motor a worm gear would hold position, so while current consumption stops, the gear experiences the strain of holding the position. I've seen worm gears and threaded rods used for their ability to hold position when power is cut. For small motors and loads this shouldn't be a problem, but for large loads it might exceed the strength of the materials and strip a gear.
  • Aj53Aj53 Posts: 3
    edited 2014-04-14 10:14
    Thanks for your help Martin!
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