Can anyone recommend a good way to measure weight of a canister being held by a gripper arm? The canister is horizontal and will be held out only about 2 inches from the front of the robot.
Maybe you want to put a movable counterweight on the other side.· You could start it at the front (the bot would be tipped toward the front) and move it until a sensor on the back indictes that it hit the ground.· You could then see the position of the counterweight and determine the weight. Hope this helps
The arm will have to grab the can as well as raise it about an inch. Since the robot will be moving id like something thats stable all the time and it seems a mechanical method like that would not be, at least not without some other 'locking' mechanism. I'm not sure all this can be achieved in the space I have available also. Also, I'm not as good with mechanical systems, electrical is my domain.
OK, I guess that solution wouldn't work in your case.· Maybe a force sensor could e mounted so that it senses pressure on the front of back wheels.· Thats all·I got.
The motor that is lifting the canister needs more· current when lifting the canister. Just measure the motor current and you will know if it is lifting the canister or not.
I think that slide wanted to know how much the canister weighed not if he had picked up the canister or not.· I am not sure sure if the motor current would be very easy to read except if you use it for just on/off.
D Faust,·it doesn't matter if you want to know the weight of the canister.··Still measure motor current, the more weight the more current the motor will use.·Slide·didn't say what the arm will look like. In some arm designs the arm is going to "see" a different weight as the arm changes position. Make a look up table for weight at different arm positions. How do you think a robot like "R.A.D." knew a weight was too·much for it to lift?
Your right, I don't think that it is... There are too many other variables that come into play when measuring current in a motor to determine the amount of force exerted against the motor. Namely, how well regulated is your supply to the motor? ...and how well isolated is that supply from the "sensing" circuitry? I think that a strain gauge is the way to go, but I don't have that much experience using them. I know that they can be made very sensitive, even for the length of a 2 inch momentum arm. Years ago in prosthetics, strain gauges were used to sense the "pendulum weight" of a prosthetic arm, to allow it to function in a "powered·free-swing mode"·while the person was walking to give it a more natural appearance.
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IC Layout Engineer
Parallax, Inc.
Beau Schwabe (Parallax)·where are you going mount the strain gauge? If you mount it in the gripper all it is going to tell you is the force the gripper is applying to the canister not the weight of the canister. Most robotic arms are locked into the position that is seeked, so·you are not likely to have a·"powered·free-swing mode".
Comments
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--DFaust
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--DFaust
The motor that is lifting the canister needs more· current when lifting the canister. Just measure the motor current and you will know if it is lifting the canister or not.
Al
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--DFaust
Carl
Al
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--DFaust
Your right, I don't think that it is... There are too many other variables that come into play when measuring current in a motor to determine the amount of force exerted against the motor. Namely, how well regulated is your supply to the motor? ...and how well isolated is that supply from the "sensing" circuitry? I think that a strain gauge is the way to go, but I don't have that much experience using them. I know that they can be made very sensitive, even for the length of a 2 inch momentum arm. Years ago in prosthetics, strain gauges were used to sense the "pendulum weight" of a prosthetic arm, to allow it to function in a "powered·free-swing mode"·while the person was walking to give it a more natural appearance.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
You mount the strain gauge on the 2 inch moment arm.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.