Hi, I made along with a friend a small production run of one of the first electronic braking systems available, most of the current systems are a close copy of this. In the pre-production/prototype testing we came across some issues and one which I believe is causing your problem - the permanent magnetisation of the floating steel disc. If you simply pass a DC current through an electromagnet in one direction (and this is the clue) you will magnetise the steel disc and it will then lock onto the electromagnets case (normally iron for best results), once this happens the brake system is not going to work. We designed the software to continually change the current direction over 100 times a second to help prevent this happening - the result is minimal magnetic charging and smoother braking.

I am not sure how others have tackled this problem but simply shooting a voltage through an electromagnet is not going to work.

marcs