Hardware/Software help

[Anonymous]

I’m trying to get information about autonomous robots, I am building one for my grandson. It is being built from a Jazzy (mobility) scooter to be more exact it’s a zero turn scooter has twin motor drive it will have a Sabertooth 2 X 60 H-BRIDGE. At the current stage I need to purchase a micro controller, robot compass board, and a ultrasonic range finder board. Leaning towards Arduino micro-controller unless someone can suggest a better choice. For software I would like to use a simple .cad file. 2-D program for X , Y moves, also need to be able to do “C” rotation. But I know nothing about C++ programming which from what I have read that is what is needed to feed the Arduino to tell the 2 X 60 H-Bridge what,when,where,and how to use the Jazzy drive motors. Not having much luck in my searches. Much of the forums don’t want to waist time answering my questions. And the companies I have contacted must think I am trying to steal ideas from them. This has me at a bit of a disadvantage.
A little info about me, I am a Tool&Die maker with forty years in the trade. The last 16 years of that forty I have spent in the C.A.M. room as a Cutter Path Developer. I have had target training in “Uni-graphics Nx” also training in reverse engineering software “Tebis” and “Smirtware” I need to finish this project to hold my grandson’s interest and to show him how to program it, kind of like jump starting him into creative thinking. Thank You for your time I hope I have explained it enough for some to answer my question.

Thank You for your time
Dave P.

[Dan]

How did you choose this list of parts? I suspect if you use a 9DOF sensor then you won’t need a range finder – the 9DOF can tell which way it is tilting and then drive the wheels accordingly.

C++ is overkill for most Arduino projects. There are lots of examples online and in the Arduino program to get you started with C. I would build up like so:

– a sketch to drive a motor forward, backward, forward, backward…
– a sketch to read the 9DOF sensor tilt
– a sketch to read the 9DOF sensor tilt and drive the motors forward or back. At this point you might be able to stand on the platform and have it self balance.
– a sketch to read a potentiometer
– adding potentiometer to the previous sketch for left/right turning.

Everything after that is a hardware design problem – where to put the on/off switch, how to mount the batteries, how to build the steering column so you can turn the pot without letting go of the handles, etc.

[Anonymous]

Hello Dan

You asked “How did you choose this list of parts?” I started reading about robots when my grandson talked to me about building one. The first thing I did was locate a mobility chair. Then called dimension engineering for the 2 X 60 H-bridge. Tech support went over the twin motor spec’s and
suggested the 2 X 60 H-Bridge also told me I would need a micro controller. Visited a couple of
sites looked at you tube and came up with using Arduino, and it seemed to make sense to use a robot compass and a range finder. Never been in the loop of robot fashion. At this point I have a zero turn mobility chair with a 2 X 60 H-Bridge. So in the end I would like to have autonomous robot-mower to mow a lawn by way of a .cad file, drip feed the file, put the file on a thumb drive or SD card.
“9DOF sensor then you won’t need a range finder – the 9DOF can tell which way it is tilting and
then drive the wheels accordingly.” I have seen the tilt sensor but never made the connection that it is used on a 4 wheel robot.
“C++ is overkill for most Arduino projects.” I was searching for a way to write a lawn mowing map using software that uses G-codes and M-codes. Because my logic was to make the robot think it’s a big milling machine the size of a football field. And I could use protection sheets to contain the robot from entering areas of the lawn that have flowers, Rocks, or water. Just thought I could Use “X” axis and “Y” axis and find a way to use rotation.
You said “Everything after that is a hardware design problem – where to put the on/off switch, how to mount the batteries, how to build the steering column so you can turn the pot without letting go of the handles, etc” I don’t see the need for a steering column the robot will steer like a bobcat or a tank. But I will need a remote control over ride in-case of a run-a-way.

Dave P.

[Dan]

aha. From the original post I didn’t realize it was a four wheel, or that you were trying to mow a lawn with a robot. It sounded like a DIY segway.

This is considered a very challenging problem you’ve picked. There is usually a difference between where the robot thinks it is positioned and where it is actually positioned. Even GPS only has an accuracy of +/-20′. So as the robot drives around with a fast moving blade, it might drive over the petunias or the curb and into the street.

gcodes and mcodes can tell the robot to move, but have no way to tell the robot “oh and pay attention to your surroundings. don’t run over the garden hose.” a remote will be necessary – the only way I see this working right now is exclusively by RC driving. An RC remote can be attached to an arduino, which will read the PWM signals from the remote, translate one PWM to an angle value and another to a speed value, and command the h bridges to drive the motors.

I’d start by getting a signal from the RC controller to the arduino to Serial (google it) to my PC, and when those numbers are sane then I’d attach the motors (without wheels) and test forward, back, left, and right steering. finally I’d mount all that on a frame. You’ll probably want a separate 9v power supply for the arduino, as it’s easier than adding a voltage divider to run the arduino from the same power supply as the motors.

[Anonymous]

Forgive me for not explaining in more detail, most days if I type a text or letter I do so between jobs which means a short note might take 5 min. or 5 hours and most times I take it for granted that people know what I am thinking when I am multitasking. The flip side of my problem is I am thinking this project can be made as if I am programming a cutter path. For example: I thought the compass board would talk to the robot the same way a stepper motor talks to a controller constantly calibrating it’s location. Could I achieve the same results if I set the program up using a grid pattern? call out each square as a fixed size and give a location calibration as it passes through each square of that grid? To make it more efficient a look-a-head feature if that is even feasible. But it might require more memory than what the Arduino can handle. to give you an idea of the grid I am speaking of it would need to have 300 squares along “X” axis and 300 squares along “Y” axis. Each square measures 18 inches by 18 inches. And call it out as 18 inch grid The robot compass would be orientated to “X” and “Y” of the graph not setup to reference the Earth’s magnetic North Pole. The command would say start at (X 0.0, Y 0.0) which would be bottom left corner of grid. First move would say goto (X 72 , Y 72) and create a path moving “X & Y” simultaneously. Is this even possible? or were the 60’s too good to me.

Dave P.

[Dan]

18″x18″ won’t matter when your GPS has a resolution of +/-360″.

CNCs and 3D printers can get great accuracy because the moving piece is attached to the frame. literally the frame of reference is always fixed. A lawn mower moving over the grass is detached from the frame of reference.

Put another way: you’ll need to find a method to accurately calculate the position of your lawn mower to within 18″ (probably much less than that) relative to your house and lawn. If you can find that, the rest is (relatively) easy. One could drive the lawn mower around in “record” mode, then play back the same recording later to get a pretty good cut of your lawn every time.

[Anonymous]

Could something be mounted on a non drive wheel. Mount a trigger wheel that sends a signal on every revolution. I am sure I am reaching out in deep space thinking hardware like this is even available. Do they make a tracking device that could be put in stationary beacon that could receive a signal from a trigger wheel and use that to calibrate the path of the robot.

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