Load sensor on tool

    Hello


    I currently work on a project where a robot picks cast iron parts out of a bin. The position and orientation of the parts are more or less random. The parts are located using a vision system. Sometimes the parts are entangled. Because of this, the robot might pick 2 or more parts at a time in some cases. The customer will not accept this, so he suggests that we mount a load sensor on the tool unit. By measuring the weight of the gripped parts, we should be able to determine whether we have gripped more than one part. I don't know how heavy the parts are, but my guess is that they weigh around 0.5 kg each.


    So my question is: Do any of you have experience using a load/weight sensor mounted on the tool? Does it sound realistic to solve the problem using a weight sensor?
    The sensor needs to be relatively compact, and must be able to withstand forces that are much greater than the forces it is measuring.


    Thanks in advance!


    /RoboticsMan

    No direct experience with your particular application, but some experience with 6-axis force-torque sensors and also strain gage based load cells.


    I suppose it could be made to work. The robot would have to remain stationary during the force sensing to eliminate forces due to inertial effects. Sensors would have to be sized properly. I would also do a mass measurement test on a suitable population of the cast parts to make sure I had good data on what my target range would be. Seems you may have to be very careful in your system design to avoid over-ranging your sensors due to collisions, binding, misalignments, or general handling of parts. And incorporate a regular method of auto-calibration.


    An alternative may be to pick the part, put into a secondary location and check it with a camera again for single-part verification.
    Or check with a second camera while holding the picked part.


    Or combine the two methods for extra redundancy.

    Hello TygerDawg


    Thank you for your answer. I have thought about all of the things you mention. Unfortunately, the cycletime will be too long if we have to put down the part and make a verification using a camera. I was hoping that a company like Schunk had a finished product that could be mounted on their gripper modules, but this does not seem to be the case.


    /RoboticsMan

    RoboticsMan


    I dont know the shapes of your parts BUT
    The tool (mechanically design) should be able to pick one part only and if for some reason picks two, the sensors on the gripper should tell you that there's something wrong (close gripper sensors input not ON). If something is wrong, drop them and pick a new one


    If you have the luxury of having a 2nd camera and cycle time, you can locate a camera between your pick and drop locations and stop for a second while you are taking the picture. Your master picture will be the tool facing the camera with ONE part.

    Retired but still helping

    Hello Fabian


    Thank you for your answer!
    The parts are rings. It is possible to grip one ring through another, and it is not possible to detect this situation by looking at the position of the gripper fingers (open/closed). The parts may either be gripped from the side or from the top, and we may not have exact information about the orientation of the part in the gripper (since the part can move in the gripper when we are pulling it out of the bin). This also makes it difficult to make a check using a camera, because the ring might be sitting in a new way in the gripper every time.
    I'm still open to new ideas :icon_smile:


    /RoboticsMan

    When picking up blank sheet metal to load presses, you can get a "double blank" detecting sensor which would be capable of detecting 2 pieces of metal stuck together.


    I'm not certain how the sensor works but it is capable of detecting 1 piece of metal (a few mm thick) and then it also detects when you have more than 1 piece of metal.


    Perhaps this could work as well??


    RoboGuru

    Hi,
    I think instead of going for vision or force torque sensor which add more cost to your project, you can try for through beam sensors.
    I not sure of your part, but a rough thought is that when you pick a ring take it to checking station where you can have 3-4 through beam sensors arranged in such a way that entangled ring can be detected. In this case may be you can more through beam sensors depending on your part.


    Hope this Works. :beerchug:


    Regards
    Sachin

    Just Do It.........

Advertising from our partners