Robotics, how to detect contact with objects?

  • Thread starter kolleamm
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  • #1
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Main Question or Discussion Point

I have a robotic arm that needs to be able to detect whether or not it bumped into something like a wall.

What would be the most practical way to do this without adding a large amount of sensors in different parts of the arm?
 

Answers and Replies

  • #2
rbelli1
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What types of sensors have you researched? Have you ruled out some types for any reason?

BoB
 
  • #3
Tom.G
Science Advisor
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In order of safety & reliability. Note that many Safety Codes require a physical interruption such as a switch in a supply line. Shutting off an 'Enable' input to an IC is generally NOT considered sufficient.

1) Often done with Bumper Strips. Think of a car bumper mounted so it moves toward the car body when something is hit. Then put a small switch behind the bumper to kill motor power in that direction.

2) Mount the drive motor(s) in a compliant mounting (rubber?) such that the motor body rotates a small amount at high torque. Mount a switch that gets actuated when the motor body rotates. (This is how electric garage door openers shut down when the door is blocked. [They crush fewer people that way.])

3) Sense the motor drive current and shut down on overcurrent. Not always useful, especially when high acceleration is desired.
 
  • #4
rbelli1
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How big is this arm?

1) Bumper strips can be as simple as a bent wire.

2) Torque sensors can be used for a more sophisticated solution. They can improve your control system as well.

3) For high speed and acceleration you would want to actively stop the motor if there is a safety concern.

Ultrasonic sensors can be used for object detection. For a robotic arm you will probably violate the large amount constraint.

Is the wall any wall of any type or do you have a particular wall in question? Can you make it conductive and sense collision electrically?

BoB
 
  • #5
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So basically it's a life size humanoid robot. I need the robot to be able to move it's arms in a complex environment without damaging them. The best solution I have found so far are capacitive proximity sensors although I'm not too sure that's the best choice. It seems like a good choice because they can sense a nearby object without actually touching it, just as long has it has some resonable mass which most objects do anyways.
 
  • #6
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You might dig around the net for "whisker sensors", some interesting work being done with interesting solutions for this problem. Maybe it'll give you some ideas.
 
  • #7
374
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You might dig around the net for "whisker sensors", some interesting work being done with interesting solutions for this problem. Maybe it'll give you some ideas.
Thanks for the suggestion! Well if the capacitive sensors don't work I'll probably use that idea.
 

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