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Discussion Starter · #1 · (Edited)
new Motor Controller for DC motors (recommendations)

I am a EE at Purdue University and am developing a series wound dc motor controller with two other Purdue students (ME and EET recent grad). We are starting a company and plan to develop a motor controller, dc-dc converter, and a charger.

I have already successfully made several dc motor controllers and a dc-dc converter. The first product we will release (in about 2 months) will be a motor controller. We have a working prototype and will soon be testing it on a converted Porsche 924s.

We are looking for feature recommendations, please help us out by letting us know what features you would want. With this first controller our goal is to meet the need of a low cost forklift conversion.

Current Plan:
  • 144v nominal (12v-165v tolerated)
  • 750-1000amps peak (for 1min)
  • 400-500amps continuous
  • $900
  • One year warranty
  • Current Limiting
  • Programmable by USB with GUI
  • 0-5k throttle
  • Data Logging
Exact current limits will be determined after field test.


Features we are debating adding for increased cost
  • Included 200w DC-DC
  • Integrated Precharge Circuit

The next planned motor controller will be HV.
 

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A commercial product pretty much has to have automotive-style CAN bus reporting, with OBD2 parameter and error reporting.

USB is a good choice for upgrading controller firmware, but not the best way to report run-time status.

I expect a commercial product to have

  • traction-side voltage sensing

  • traction battery power (watt-hour) and current (amp-hour) usage meters

  • dual contactor coil outputs, with individual stuck-on checks at start-up and shutdown

  • brake, clutch, neutral and reverse inputs, 42V tolerant
  • precharge and discharge control (trivial to implement -- why would this be optional?)
  • current, direct PWM and RPM control modes
  • temperature monitoring of heatsinks, cooling inlet and outlet, and motor, with power limiting (programmable limit for at least the motor sensor)
  • ability to support drive-by-wire with a CAN bus throttle, as well as dual-wiper TPS inputs e..g. the Bosch dual potentiometer style, which allows better low-throttle accuracy and enables fault checking
  • Cruise control e.g. fixed RPM mode
  • Shift rev-match with appropriate inputs (RPM, road speed and neutral switch)
I don't see a compelling reason to include a DC-DC converter. There is no safety reason to make it part of the motor controller, and it's not naturally tied to it. The "right" amount of converter power vs house battery is a per-build decision, but 200 watts isn't enough for most cars At night you might havedual 55 watt headlights, eight or more 5W or 10W running lights, two or three 21W brake lights, dual 10W or 21W reverse light. Throw in a 200W HVAC fan and 150W defogger grid and you can see that backing up on a moist night is a challenge.
 

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You may want to read this thread... http://www.diyelectriccar.com/forums/showthread.php/new-controller-prototype-29062.html also do, some searches for the Soliton and Open Re-Volt controllers. There is a lot of feedback on these threads.

You need to know what market u are targeting and what competition you will be facing. Right now, your specs are not going to draw in many potential customers.... well, perhaps I should reword that.... not the ones who want higher performance. Your price is an admirable target...if you can hold it. This will draw the lower end in most likely.
 

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Discussion Starter · #4 ·
Thanks for all the suggestions. We will be competing in the 144v market. From the response to the forklift motor thread and the number of threads I see started about forklift conversions, I think there will be enough potential customers. When my friend and I did our conversion, we were just out of highschool and had barely any money. Logisystems was our only option and offered no programming options. The greatest improvement we want to add compared to a logisystems is in depth programming options.

Similar products to the market we are looking at would be the Curtis 1231, Kelly KDH series, Warp Drive 160V 1000A controller, and Raptor 1200.

We will include the output to controller precharge, but were considering adding an internal contactor which would cost extra.

Temperature will be monitored in several key places within the controller.

Rev matching would a very cool idea, currently no one else offers this though (as far as I know). It seems like more of an independent product would be better at this since I think few customers would want to pay the premium.

Which programming options would you be most interested in modifying? Would a custom ramp curve be something you would modify?

Thanks for the suggestion on brake/clutch/neutral input. We will add documentation for making these switches turn off power to the motor.

We will look into CAN as a communication option. We will definitely include USB though, we have already been working with this for uploading firmware and changing limits on our prototype and it works very well.

Jim
Makt Systems
 

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Hi Jim

You should look at some means of failsafing the throttle signal, throttle microswitches or two throttle pots.

Also a traction control - wheel spin system - set a maximum acceleration rate or compare front and rear wheel speeds
 

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Discussion Starter · #6 ·
We will include documentation for the throttle micro switch failsafe. We will add a "disable" input to the controller. As a safety, any switch wired in series to this input will disable power output when open. For example, switches on the brake pedal, the potbox, your charging cable, etc.

Seeing as there are many different inputs we are seeing requested, we may just add external connectors for ~2 extra inputs and outputs. This way, we can add options in programming and the user can choose the extra features.

Traction control would be a cool feature. I don't think we will include it in our base controller, but I would be willing to work with you to implement it on your vehicle. There will be a maximum acceleration rate, we plan to make it user adjustable.

Since we will be fairly low volume at the beginning, we will be open to custom options in software and hardware. For example, for an extra ~$150 we can upgrade the power components to ones capable of 212V nominal. We will be able to use the same pcb and case because the component sizes are standard.

Jim
 

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Discussion Starter · #7 ·
I just wanted to let everyone know we are still working on it, but not as fast because final projects and studying for exams is taking up most of our time.

Since we will all be on different ends of the country(internships) and the test vehicle in the center for the summer, I am not sure how long it will take us to put on all our validation miles. We hope to drive the controller >1000miles before selling it.
 

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Discussion Starter · #9 ·
How would you like to control cruise control? With the existing buttons on the vehicle?

I think that the main obstacle would be that every vehicle has a slightly different configuration for how cruise control works. We could probably add an extra module with buttons for controlling cruising speed, but I am not sure how easily you would be able to integrate it to your vehicle's steering wheel.

Jim
 
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