Brushless Motor H-bridge without R/C inputs for 50V/400W motors?

Ken Gracey

Hello,

I am really looking forward to a new project with the Propeller, having worked exclusively on the business side of Parallax for the last six months. We've had a number of staff absent for sabbaticals, personal leave and maternity. So I'm seeking a bit of technical therapy.

The project is a 5-6' long cataraft-looking surface robot designed to study the use of GPS for navigation on a nearby lake. I want to effectively use GPS without too many additional sensor issues to manage at the same time, so the lake is probably the easiest way to do this if I don't want a flying UAV. Managing GPS in the Parallax parking lot is a bit tricky - a robot needs to be large enough to move around a big space, but nice vehicles and UPS trucks pose unique problems. So I'm headed to the water this time.

I have two of Crustcrawler's underwater thrusters:

http://www.crustcrawler.com/products/urov2/index.php

The R/C brushless speed controls for these motors are very expensive ($200). I would rather buy a kit or off-the-shelf product that doesn't support the R/C input signals (1-2 ms pulse every 20-40 ms) but lets me provide the PWM input directly from the Propeller.

Can anybody recommend a reference design, kit, or motor control circuit I might use to design my own? I may use this project as an opportunity to make a PCB.

Any direction would be appreciated, even if you just help me hone the Google search words.

Thanks,

Ken Gracey

hover1

Ken,

I can't give any specific links at the moment, but a good Google search to start:

BLDC Sensorless Contollers

Jim

W9GFO

Brushless motor control is beyond my comprehension for the time being. So I am of no help there.

The 120 amp ESC that they specify seems way overkill for a 400 watt motor. I would think that a 40 or 50 amp controller would do just fine. They are about $50 to $60 if you don't need reverse. If you did need reverse you could make it reversible by adding an H bridge to swap two of the motor wires.

Rich H

Timmoore

There are some discussions on rcgroups.com about i2c controlled escs. Some of the discussions include circuits. Another place to look is microchip.com they have some app notes on brushless controllers e.g. http://ww1.microchip.com/downloads/en/AppNotes/01175A.pdf

gmarchese

Ken -

Jesuit Robotics (parallax sponsors us) used these: http://www.himodel.com/electric/Seaking-60A_Waterproof_Brushless_ESC_for_Boats_W_water-cooling_system.html on our underwater robot last year. The only difficult part with these is that a full reverse signal is required to send them in reverse. for example: to go half speed reverse, you have to send a full seed reverse signal for about a second, then send it the value you want.

gmarchese

Also, If you need any help with electronics / mechanics of your project, feel free to email / pm me. I am the head of electronics and programming at Jesuit Robotics, and we have other students that are knowledgable in H₂O robotics

RobotWorkshop

Hello Ken,

Have you looked at any of the controllers made by RoboteQ? It looks like they may have something that would work for your project:

http://www.roboteq.com/

Robert

rhugg

Hi Ken, we are building something similar for a research project in the Arctic. Our approach is to use two Minkota endura 30 motors (about $100 each). AFter some looking into building our own, we decided on the >30amp motor controllers from the Open Source project at Robotpower. The system uses two motors to steer rather than a rudder, and at the expense of power, great manoverability. A propellor-based acquisition system (probably several props) handle the GPS, sub bottom profiler, CTD, bathimetry and GPS. The requirement is for this system to be lowered by helicopter, left for a couple of days, then meet it at a pre-agreed upon location, after it has visited preprogrammed way points.

I'm in the Bay area and need to come to Sac sometime soon. I would be happy to drop by if you would like to chat.
-Rob