BLDC Overcurrent
- From: eziggurat@xxxxxxxxx
- Date: Tue, 29 Jan 2008 00:20:14 -0800 (PST)
Hello,
I am currently working on automatic door that uses a BLDC motor. I am
using the current of the motor to determine if an obstacle is in the
way of the sliding doors. The problem is to determine when it is a
real obstacle or a cold start (stiffness of the gears and door). The
method I am using is to store a value and compare with the next 50
readings and check if it is a greater rate of change by checking if
the current value has exceed a constant threshold with comparison to
the stored value. The only problem is that the sensitivity of the
system decreases (i.e. a higher force is needed to stop the door) and
the threshold is not dynamic so if door size changes, I would not know
if the threshold is correct.
I tried using speed by setting the PWM to 0 to stop the door and
compare the speed between the cold start and an obstacle detection but
there isn't much speed differences.
The microcontroller code that I inherited, the person calculates the
acceleration and deceleration using the following equation:
m = max_speed - min_speed/size of door*10/slope; Slope varies between
10-100 and the size of door is the amount of halls sensor counts.
Any help will be useful.
Paul
.
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