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I have a system design with a 149oz-in stepper motor for opening/closing a drawer style door. My cross sectional dimensions of the door opening are 20" width by 15" height. The motor actuates linearly inward and outward via remote user control. I'm trying to install various safety protocols, one of which is for physical interference during the state of which my system is closing or retracting the motor driven door. I need to efficiently handle the detection of such off-nominal events, where a human hand/finger or other interfering object is inside the opening during this state of operation. I want to immediately stop the motor (or shut off the entire system) upon sensing any physical interferences during the closing state in order to prevent crushing the impeding object with the retracting door.

For a reference point, the most relatable application to mine that I can think of is a kitchen dish washer door opening/closing via a remote controlled motor. I've looked into light curtain sensors, but I am unsure if these are suitable for my smaller sized cross section. To me, it seems that this would also be quite hard, if not nearly impossible, to incorporate something like this into such a limited space opening as well.

Thougths?

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  • $\begingroup$ Nearest obvious application is the car electric window motors that stop and reverse if they detect an obstruction. I will let you do the research. But as that detection is likely electrical load sensing this may be better on Electrical Engineering... $\endgroup$ – Solar Mike Jan 19 at 19:13
  • $\begingroup$ Some type of torque or power measurement should work. It might be easier with a DC motor than with a stepper motor though. $\endgroup$ – Justin Jan 19 at 19:17
  • $\begingroup$ The motor force is proportional to current and thus acceleration or deacceleration from interference. Not enough details have been considered or specified on drawer friction , acceleration control and fault detection force vs position. Please define ! Motor current may vary and have cogging unless it is a 3 phase stepper. I doubt you have the right motor. You can use less torque but still position sensitive with fractional steps but still lacks sensitivity unless calibrated for each microstep position, velocity and acceleration. which I doubt you can do. $\endgroup$ – Tony Stewart Sunnyskyguy EE75 Jan 19 at 19:29
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    $\begingroup$ My Mercedes stepper driver for the rear door just cogs (slips) if I try to stop it from moving.so the torque is just enough to move it . $\endgroup$ – Tony Stewart Sunnyskyguy EE75 Jan 19 at 19:34
  • $\begingroup$ @SolarMike nice recommendation, to which Tony iterated as well. Would a two phase stepper with 1/8 stepping be an OK unit to start with in investigating and testing this "force sensing" approach based off force vs position? $\endgroup$ – Pholotic Jan 19 at 20:49

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