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Basic Electronics » BLDC

December 21, 2013
by esoderberg
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Made up a little Brushless DC controller. It is based on the Allegro 4915 and uses Hall Sensor feedback. Given the layout and components the controller is probably good to 30V and around 30 amps. I've had it up to about 5 amps continuous and it is barely warm. I've got it hooked to a NEMA 23 BLDC motor with a 1000 PPR encoder and am running a PI velocity closed loop control scheme. With this setup the motor runs from about 3 rad/sec to about 250 rad/sec and holds target w to about 1 rad/sec. In this case the custom build actually came in quite a bit cheaper than I could find commercially and exceeds what I needed so I'm pretty happy with the results.

Eric

BLDC_controller

December 21, 2013
by JKITSON
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Eric..

Looks very good. Nice work..

Jim

December 22, 2013
by Rick_S
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Is this another piece of your autonomous vehicle??

December 22, 2013
by esoderberg
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Rick,

Yes. I've been using a linear actuator to control my steering, now instead I'll have a BLDC motor going through a planetary gearbox (200:1) and then direct to the steering shaft. It's far more compact than with the actuator. Also, I've put a bit more effort on the steering portion of the control loop this time with the goal of getting a faster steering response with no overshoot. Hopefully it will help with the handling qualities, which were good above about 8mph before, but not so good at lower speeds than that.

Eric

December 22, 2013
by Rick_S
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This project must eat up a lot of your spare time. You've been working on, and improving on it for quite some time now. What is your end goal with the project?

Rick

December 22, 2013
by esoderberg
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Rick,

In the end I'd like to have a safe, fully enclosed, and highway capable vehicle. The basic idea is to combine the fun, cheap to operate aspects of a motorcycle with the ease of operation and more practical aspects of a car. I've seen many other similar attempts to do the same, but none exactly like what I have in mind. I'm probably 85% there on the electronics/SW side. Trying to make it as fail safe as possible has eaten up a lot of time; been trying to build in dual redundancy in most sensor, controller, and electronics elements, but the steer motor itself is a single point failure mode, so it needs to be as reliable as possible.

December 23, 2013
by Rick_S
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So are you trying to compete with Google's autonomous car project? :D

Sound like a large undertaking but one you seem to have quite a firm grasp on. What are the laws regarding vehicles like that on the public roads?

December 23, 2013
by esoderberg
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Rick,

Autonomous is actually a bit beyond what I'm doing - my bike balances itself but still needs to be steered by the operator. As for the laws, I don't actually know! My test bike is registered just like any other and for the moment I'm just ignoring the fact that some "modifications" have been made. I suppose once I really have the electronics and SW complete and start in on a new from the ground up bike I'll have to figure out how to make it legal.

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