Hybrid trike speed control

Hi!
We are developing an urban hybrid trike prototype -electric and human powered-, intended for Tierra del Fuego's hard topographic and weather conditions.
The trike has two independent electric driven front wheels, and one human-powered back wheel.


The electric driven wheels are intended to assist the rider, and turn only passively if the rider does not pedal themselves. I am part of the team in charge of developing the front wheels speed control system. I am an electronic technician, and my partner is an electronic engineer. We have no experience in control systems, but are quite good learners.
We plan to use two e-bike conversion kits, and control their individual speeds as a function of the human driven wheel speed, and the turning angle.
I would really appreciate your advice regarding hardware and software most appropriate for our project.
Thank you very much!

You need to know about the ebike controller and what form it’s input takes and how the “assist the human effort” bit is used -usually by measuring the input effort rather than speed ( torque sensor)
If you have two controllers there maybe an issue in getting stable output - they might fight one another ( eg one increases the speed , the other backs it off ) .
Odd things may happen when turning too when One wheel has to travel faster than the other
Why not have the motor in the rear wheel instead - one motor, one speed controller etc, no problems with wires on steered wheels or speed difference of wheels either .
If you are thinking of better “traction” as the reason , how will the FWD system know about a slipping rear wheel ( or I guess the fronts ) .

You can buy an off the shelf system for the rear wheel , I can’t see a reason for two motors , needing steering angle measurement , difficult speed control , and a lot of development - don’t er .. reinvent the wheel :wink:

On that note, there are so many electric vehicle systems now, that most of the tech you will need should be available from OEM vendors.

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Thank you aarg for your answer. I wonder if you could share one or two of these possible OEM vendors, as an example? We have no experience in this matter.
Thanks again!

At a minimum, people here need to know more about this.

Hi Hammy. We will take into account the torque sensor suggestion, thanks for your input.
I agree with you that controlling two motors is way harder than controlling just one, but we have no choice in that matter. Ushuaia is a tough city for bike and trike riders, with steep streets, snow and mud, so we need three-wheel traction. That is what makes our project locally relevant.
Your last question is very useful, since we had not taken it into account yet. I was thinking of using the rear wheel speed (and torque) as a reference for the front wheels speeds, now I see that we will also need to check the front wheel torques as a reference for tha rear wheel torque, to detect rear (human) wheel slipping.

Hence, since you must interface the drive system, we would need information about that. Please do provide that, because without it everything will just be yadda yadda yadda.

I would start with an assumption that developing a speed controller for a electric trike or cycle is not trivial (big time!) and expensive as well.

If you develop the vehicle you intend then you need to consider the problem of making spares available.

Controllers for electric bikes are relativly cheap, I just bought a spare for my eBike for circa £35 delivered.

Some of these eBike controllers have hackable software and if a standard model eBike controller with pedal sensor or torque sensor does not meet your needs then maybe use one where you can hack the software.

As has been already suggested, dont re-invent the wheel, especially when you may get what you want ready developed, easily replaced, and cheap elsewhere.

Sorry aarg, the only thing we know so far is what the vehicle should be able to do:

  • move adequately in the tough topographic and weather conditions we have in Ushuaia
  • assist, but not wholly replace, human power
  • maximum speed: 25 km/h
  • it is intended for urban (though tough) conditions, no off road intended
  • estimated power of each motor: between 1500 W and 2000 W.
    Our target is people who would ride a bike or an e-bike in a plain, moderate weather city, but end up using a car because bikes are not adequate enough for use in Ushuaia.
    The question about HOW we are going to achieve this is just made, but not answered yet. We are starting from scratch.

I think then, it's a long way from the purpose of this forum, which in this case, could be to assist in developing control systems for such a vehicle. General design of such a vehicle could better be discussed in some electrical vehicle venue.

Also my request for more information about the one thing you say you did investigate, has still not been answered.

Realistically, we can not help you design a speed control system for a completely unknown drive. You are a tech, and you have an engineer on your team. That sounds like enough human resources to start specifying and researching various drives that are available.

When you have found some candidate drives and evaluated them, you could post information about it here, and we could help you with some control software/hardware choices.

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I totally agree, aarg. There are more members in our team, working in the general design of the vehicle. Regarding the control systems, we will have to make some research and experiments, before we have more concrete questions to post in this forum. This brings me to re-phrase the first question I posted:
considering the general information we have shared so far, could you tell us which would be, in your opinion, a suitable Arduino board for this type of project? We will start experimenting with this board.
Thanks again, best regards!

The thing is - it depends so much on the sophistication of the tasks that you expect the Arduino to perform. If you can outline what those might be, it would be easier to answer that question.

In other words, sorry, the general information you have provided so far, is not enough to answer that question.

None of the current official Arduino boards meet industrial or automotive specifications. That might be something for you to consider carefully.

OK aarg, this information is really useful for us. I guess "automotive" is not the type of project we are in. It is more like a bike with some control challenges. We are going to use two 1500 W motors. If Arduino boards were not the best option, what would you suggest instead?

Spot on .. you need to specify each of the individual tasks in detail and what each will involve , what sensors, what algorithms etc, then decide how you want to do each of them .
You can’t decide what sort of processor setup ( and how many etc) you need until you know all that .

BTW - you can’t go to your leader when it fails and say “ someone on the Arduino forum ( aged 7) said it would work”, you need to know what you are doing , and tackle aspects in small chunks .

You do not yet have enough information or even design criteria to decide about controller boards.

Finish the specification and design part of the project, then come back to the forum with sensible, informed questions.

Be aware that in quite a few countries in the World, using that power of electic motor may make the thing you are building a 'vehicle' ; which can mean a large amount of regulations to follow and approvals to get.

In the UK, and most of Europe, you can use an electric motor up to rated 250W on an electric bike for instance, but beyond that you need to follow vehicle regulations, have insurance, have a driving licence etc ........

OK hammy, thank you for the advice. I see there is a lot of work to be done before choosing the processor.

Ok jremington, I see I have a long way to go before I can ask for advice here.
I'll be back :sunglasses: