colision detect scara staubli robot

    hi everyone,


    I need some kind of function or setting that refer collision detection in scara robot. I have doubts if in fact there is something in this type of robot due to the absence of brakes on the axes, just like 6-axis robots.

    and if so, are there any instructions or manuals to be followed?

    Hi Ycrideas,

    Look for "getJointForce" (or AddOn Motion + getJntForce)) but the precision is not very good.

    Quote
    The joint force is not a direct estimation of external efforts. It also includes gravity, friction, viscosity, inertia, noise and accuracy of current sensors, relation between motor current and torque. It can be used to estimate external efforts only by recording forces in reference conditions, and comparing them with forces measured in similar conditions with additional external efforts.

    For CS8, you have an example on Stäubli website "detectCollis" (or something like that) but I never use it !

    For CS9, I think there is a WhitePaper and an application ...

    Have a good day...

    Edited once, last by Galet (May 5, 2023 at 5:19 PM).

    As Galet said, there is an instruction getJointForce() to monitor the robot torque, or force if the joint is linear, but that won't prevent collisions.

    Code
    void getJointForce(num& nForce)

Function
This instruction returns the current joint torque (N.m for revolute axis) or force (N for linear axis) computed from the motors currents.

The joint force is not a direct estimation of external efforts. It also includes gravity, friction, viscosity, inertia, noise and accuracy of current sensors, relation between motor current and torque. It can be used to estimate external efforts only by recording forces in reference conditions, and comparing them with forces measured in similar conditions with additional external efforts.

It returns only an order of magnitude for forces. There is no commitment on accuracy that must be evaluated with each application.

A runtime error is generated if the parameter is not an array of num with sufficient size.

    You may monitor the torque of the regular operation, and when running have a task to compare the current value with the monitored one. If the torque is exceeded, then the robot is probably colliding with something.

    Again, this doesn't prevent the collision, only stops the robot when the torque gets to a certain value. So the robot is already colliding by the time the torque gets exceeded. But is good to prevent hard collisions.

    About the brakes, no robot stops with the brakes, the brakes are only used to maintain the robot's position.

    Even when an emergency stop is triggered, most of the robot uses the motor to hold and stop the robot and after a complete stop, the brakes are engaged.

    Don't know any brand that uses the brakes to stop, unless everything else fails. Keep in mind, braking while moving damage the motor and if you do it multiple times, you will need to replace it.

    Any issues let me know,

    Hi to all,

    The difficulty is not to read the speed or the joint force but to compare to the truth value... and to have anought time to react.

    For that, you need just a low speed.

    If you want to avoid a collision with the protected area, I think you make a mistake, the solution is to reduce the collision risk.

    Everyone want built an highspeed cobot but safety and speed are not compatible... It's the reason why a cobot is lowspeed and an industrial robot have an arround protect.

    Have a nice WE !

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