track steering with scooter motors

[D Alan Stewart]

Hi, all. I have a small one rider vehicle idea I want to build. This is my first time doing an electric vehicle project. It’s literally going to be a motorized lawn chair. Well, a motorized platform with a lawn chair sitting on it. I want to attempt to do track steering, where the wheels on each side work as one. I would appreciate any expertise offered.

I’ve already ordered four Xiaomi M365 hub motor wheels. Those are DC brushless 36V 250W. As I understand it these motors have the ability to do regen, which is used in the actual scooter for braking in addition to a rear wheel brake. I’m hoping I can get away with regen only for braking. I’m not looking to make this thing fast.

I see there are cheap generic motor controllers, but I’m leery about shopping at the bottom of the barrel. Will I need to have a separate controller for each motor, or can I use a single controller for each pair of motors? I imagine either way I may need a controller to interface the joystick or similar combined throttle, steering, and braking device to the two or more motor controllers.

Any recommendations on controllers I should shop for? I’m a retired software developer so not afraid to learn how to program something, but lazy if there’s something off the shelf that is adequately configurable. I’m not constrained financially but also have the Scottish desire to not spend more than I need to.

TIA for any help.
Alan

 

[Apartunis]

Will I need to have a separate controller for each motor, or can I use a single controller for each pair of motors?

Yes you will need a separate controller for each motor. There are a few controllers for dual motor systems that package two controllers in a single housing, but they are still separate controllers internally.

I have gotten excellently functional controllers for about 20 dollars each online. Maybe more now in tariff times. There is no need to spend very much money on controllers unless you require programmability or a feature set that does not exist in a cheap controller.

36V/48V 350W DC Electric Bicycle E-bike Scooter Brushless Motor Speed Controller | eBay

(Rated Power: 350W. Cruise speed line. if wheel reverse, Separate the self-learning line. Docking the self-learning line again，if wheel forward ,Separate the self-learning line.). docking the two self-learning lines, the wheel will forward or reverse.

www.ebay.com

.

I think the torque required for effective track steering or skid steering will be at odds with your desire to go fast and the power limitations of those scooter motors. At least you get to multiply everything by 4.

 

[D Alan Stewart]

I think the torque required for effective track steering or skid steering will be at odds with your desire to go fast and the power limitations of those scooter motors. At least you get to multiply everything by 4.

Thanks! Actually I said I don’t plan for this thing to be fast. The intent is relaxed motoring. I think to skid steer all that has to happen is the power needs to be reduced on one side.

Alan

 

[Apartunis]

Thanks! Actually I said I don’t plan for this thing to be fast. The intent is relaxed motoring.

I reviewed the tapes and found that you want to *make* the thing fast, not make it go fast. That's very good.

I think the sweet speed for M365 motors is 18mph at 36V nominal. That is pretty fast for what you are trying to do. I would use lower voltage if you can get the necessary torque that way.

 

[PaPaSteve]

How about this idea :
Search for "brushless controllers for wheelchairs"
They often come with the joystick.

 

[D Alan Stewart]

How about this idea :
Search for "brushless controllers for wheelchairs"
They often come with the joystick.

Thanks for the tip! But I have four 250w motors to control…

 

[Apartunis]

Thanks for the tip! But I have four 250w motors to control…

One throttle can control more than one motor as long as they are all expected to do the same thing. I imagined the simplest solution for you would be one two way throttle on each side controlling both motors on its side. A single joystick containing logic to do the same thing would also work.

Reversible controllers are common, but for seamless operation the throttle would have to switch the reverse wire when reversed.

 

[D Alan Stewart]

One throttle can control more than one motor as long as they are all expected to do the same thing. I imagined the simplest solution for you would be one two way throttle on each side controlling both motors on its side. A single joystick containing logic to do the same thing would also work.

Reversible controllers are common, but for seamless operation the throttle would have to switch the reverse wire when reversed.

I see that these generic brushless scooter motor controllers have specific wires for each feature, which implies there are universal or de facto standards for the protocol each of these wires expects?

I guess the throttle wire signal is just voltage so the throttle wires from two controllers can be spliced together and connected to a single source? If that’s true is that likely true for all the controller wires?

Before @PaPaSteve’s comment I was actually thinking of buying a Raspberry Pi Pico 2 as a central controller to manage the joystick and four motor controllers.

 

[Papa]

Not to spoil the party, but,.. I'm dubious you'll be happy with skid steering and a CoM height well above safe limits (especially if you expect speeds even close to 18 MPH). Not to mention outrageous tire wear. I'd suggest you start with just two rear motors, and casters on the front... ala wheelchair, but a lot lower seat height.

 

[PaPaSteve]

A Raspberry Pi Pico 2 as a central controller to manage the joystick and four motor controllers sounds very sensible.
There is likely better guidance from robotics forums such as Hackaday

However . . . 4 motors will probably suck up more battery verse 2 motors and 2 castors due to the traction fight 4 wheels will have.

 

[D Alan Stewart]

Not to spoil the party, but,.. I'm dubious you'll be happy with skid steering and a CoM height well above safe limits (especially if you expect speeds even close to 18 MPH). Not to mention outrageous tire wear. I'd suggest you start with just two rear motors, and casters on the front... ala wheelchair, but a lot lower seat height.

As I said earlier I don’t plan to make a fast vehicle, rather a relaxed, stately vehicle, more like a parade float. But it does need to be able to easily handle a steep hill with a large rider plus a cold drink cooler, and maybe a couple bags of groceries. Steering wheels add mechanical complexity I don’t want and adds nothing to the desired visual of a motorized lawn chair. Being able to do an in-place ‘tank turn’ is a visual plus. To do that with steering all four wheels would need to be steerable. I don’t think tire wear will matter for the small number of miles I expect to travel.

 

[Papa]

Steering wheels add mechanical complexity...

Not universally true - my delta trike not only employs the simplest directional control available (both to DIY replication and usage), but it can, and often does,... perform U-turns within it's length (the inside rear wheel during low speed U's either stops rotating, or rotates backwards).

....and adds nothing to the desired visual of a motorized lawn chair. Being able to do an in-place ‘tank turn’ is a visual plus.

... whatever 'floats yur boat'.

No further interruptions from me.

 

[D Alan Stewart]

Not universally true - my delta trike not only employs the simplest directional control available (both to DIY replication and usage), but it can, and often does,... perform U-turns within it's length (the inside rear wheel during low speed U's either stops rotating, or rotates backwards).

... whatever 'floats yur boat'.

No further interruptions from me.

Thanks, but this project is about making a visual statement. There will be no mechanical steering wheel or handlebars for the user to steer the wheels with. There will be a (hopefully) discrete joystick that controls steering, power, and forward/reverse.

 

[PaPaSteve]

Not so crazy an idea !
Built in 2017 when I worked in San Francisco.
A couple of creatures built from Craig's list sourced, joystick controlled, skid steer, mobility scooters.
Note - they also have 4 castor wheels.
Turned so sharply that the shapes (tails, heads) would bump into things.
They went up and down hills safely.
Both needed replacement batteries (24v lead acid) which cost more than the used scooters.
The shapes are made from layered pink insulation foam board.

 

[D Alan Stewart]

Not so crazy an idea !
Built in 2017 when I worked in San Francisco.
A couple of creatures built from Craig's list sourced, joystick controlled, skid steer, mobility scooters.
Note - they also have 4 castor wheels.
Turned so sharply that the shapes (tails, heads) would bump into things.
They went up and down hills safely.
Both needed replacement batteries (24v lead acid) which cost more than the used scooters.
The shapes are made from layered pink insulation foam board.
View attachment 389884View attachment 389883

Cool!