Robot Mower

[cooperhow]

(I already have some 40V Ryobi batteries, so building this around a 40V Ryobi push mower seems possible at this point.)

How can I do it with only one battery system to build either an RC or fully autonomous battery electric mower? Push mowers use 40 - 80 volts. It seems that most wheelchair motors use 24 volts. Hub motors might match the higher voltage better. However, are they good for the low speeds of a mower?

Can the voltage difference be controlled by limiting current with a good motor controller, like a RoboClaw? From what I've found, Sabertooth controllers won't handle 36 volts.

Brushed, brushless, three-phase, hub motors? Where to start? Encoders would be required as I think for the autonomous mower.

I'm making many assumptions and I'm getting back into programming with the Arduino starter kit, which is interesting so far! Any comments are welcome, thanks!

 

[rjenkinsgb]

Sounds a bit like one of my [very] long-term projects!

This is eventually going to be a large robot; the chassis is made from 20mm C channel rails, drive wheels at the back and giant casters at the front. Only the electronics parts are in the photo below.

I ended up choosing wheel motors intended for balance boards, as they are capable of high torque at low speeds, with built in hall sensor position feedback. The drivers are like these, which area available on ebay & amazon etc. and detailed usage schematics are available for the controller IC; the boards match the diagrams. (The wheels were secondhand from ebay).

DC 12V-36V 15A 500W Brushless Motor Controller Hall BLDC Driver Board | eBay

Driver Power: <=500W. [VR] the governor end 0-5V(corresponding to 10% of motor speed -100%). [Ha] Hall signal. [Hb] Hall signal. Hall signal inputs for hall [Hc] Hall Signal. [5V] Hall power positive.

www.ebay.co.uk

They motor controller boards are rated 36V max, but just need one component changing to allow for 42V from a fully charged battery.

The buck regulator boards in the top right of the box reduce the main battery voltage, first to 15V which feeds the 12V electronics backup battery & also the upper two regs that give 5V for the computer and other electronics.
Like these, though I found mine from a UK seller:

10A DC to DC 6.5-60V to 1.25-30V Adjustable Buck Converter Step down Regulator | eBay

Load capacity: up to 10A. 1PC Adjustable Regulator Power module. Output: 1.25-30V adjustable.

www.ebay.co.uk

(When buying any buck or boost regulator modules, get ones rated at least twice the maximum possible real load, as the advertisers figures are often imaginary or the "at-the-instant-it-exploded" values...)


This machine supposed to be semi-autonomous, with the Jetson board [top left] running ROS (Robot operating system) and using an accelerometer, the lidar unit and stereo cameras for navigation.

My present challenge is getting the ROS system working with everything. I am a programmer but the way that works is very different to anything I have experience with. I got it close once then an update corrupted the SD card and I've had to start over...

A direct remote controlled robot should be far easier!

 

[cooperhow]

Thanks for sharing your project and experience with me! It's quite helpful