I am looking for some guidance and direction with my latest design ideas for a Mecanum Mobilator Platform. This design will not be fabricated anytime soon but I want my numbers nailed down for my design aspects. I am designing this platform to be able to move 2000 lbs not including the machines weight itself and with a max speed of 2mph. There aren’t really any other constraints. I have done my research on omni wheel, swerve drive, and other possible options for an omni-directional platform, but I have decided on the Mecanum wheels. My main questions have to do with motor sizing, type of motor, and control. I am wondering if anyone can steer me in the direction of some math that will ultimately help me decide what Hp motors I will need for my 4WD platform. I have looked at a few different papers that show A LOT of math that ultimately didn’t lead me to the answers I was looking for. Also I am looking at using one of 3 different types of motors, 1) AC Induction, 2) DC Brushless, and 3) Servo Motors. I know that technically all of these could work I just wasn’t sure if anyone had better luck with one type over the other. Lastly, my control. I am looking at whether or not I should go with a VFD for my motors or if I should just use a beefy ESC. I have seen ESC’s that can move motors upwards of 5 Hp so I am not worried about finding the right one. Also I know that some designs for control use a “Mecanum Mixer” to communicate with an RC Chip. Obviously this is much simpler than using an Arduino, but it also wouldn’t allow for any position feedback, from what I can tell. Any thoughts or ideas would be great help to me. Thanks for any and all advice.
You might want to contact the folks that worked on this project. https://www.youtube.com/watch?v=QXSJ7dprzf4
Seems like a similar set of design requirements albeit maybe a bit more than you have.
I think the biggest problem you’re going to run into trying to move that heavy load with mecanums is their low CoF. Before you settle on mecanum wheels I would do the physics to make sure that they can carry that load without just slipping in place.
Servos I’d say are out of the question. There’s no point in using a servo if you don’t need to be able to set the angle it should be at (which you don’t need to do for drive wheels). I’d probably go with DC brushless because you won’t need a converter to take a battery’s DC to AC.
Mecanum doesn’t automatically mean low friction. The rollers can be plenty grippy if you choose them to be. They get poor marks for pushing because the way the forces add up can cause them to slip at a lower combined forward torque than if the wheels were solid.
Just carrying a heavy load won’t make a difference if the acceleration is low enough.
Servos I’d say are out of the question. There’s no point in using a servo if you don’t need to be able to set the angle it should be at (which you don’t need to do for drive wheels).
He said servo motors. That’s not what you’re probably thinking of. Anyway, for a mecanum drivebase you do want to precisely control the angle of the wheels’ turning.
To address the original question – figure out how much acceleration you need, and that will set a lower limit on the power you require from the motors. Then start looking at candidate motors and desired top travel speed to determine the likely gear ratios between motors and wheels.
If I were designing something like this, I’d probably lean toward servomotors, because they make the low-level software a lot simpler by handling the wheel position feedback automatically. Note that most people in this forum won’t have experience with anything except DC Induction motors, so take that into account when assessing their advice.
As a programmer, I don’t see a problem with using something like an Arduino to do the control. If your favorite programming language is solder, however, that might be an issue.
Thank you, everyone, for your input. I have been leaning more and more towards using 4-1kW servo motors. Partly because of their size but also, because they automatically have an encoder which will help with the feedback adjustments to help the platform correct itself. My only problem is that I am not sure what the best way would be to run these 4 servo motors off of batteries. Most of my experience with motor controllers has been dealing with VFDs that run AC Induction motors that require an AC input power which then runs to a rectifier, then to an inverter, then to the motors. I know there are VFDs that can simply take a DC input voltage and go straight to an inverter but I’m not sure about servo motor controllers. I will continue researching this but any advice on the matter would be appreciated. Thank you for your quick replies.