Which motor / tires / motor controller would you suggest for a mower-bot?
Please pick from the RobotShop inventory.
I don’t want to have to do any considerable effort gearing down the motors so something with a low RPM would be good. Also assume about 10-12A max per motor. It should be able to carry the two motors, a netbook-like PC, a car battery, the DC whipper-snipper assembly (pretty light) and other related electronics (buried fence detector, GPS, etc.)
I assume the motor controllers will slow them down beyond that?
The motor controllers should do variable speed and reverse. I’m less concerned about regenerative capabilities, but if it has it … hey!
Of course the controller should be easy to interface to some sort of PIC.
Finally, suggestions for mounting the tires to the motor shafts … this seems to be where I always get in trouble with my bots … the mechanical linkages.
Any help would be greatly appreciated.
Here’s what I got from the calculator:
INPUT
Total mass of robot: 40lbs (could be lighter)
Number of drive motors: 2
Radius of drive wheel: 10" (depends on motor really, but I’d like them large)
Velocity of robot: 1 m/s
Maximum incline: 20
Supply voltage: 12v
Desired acceleration: don’t really care.
Desired operating time: 2-4hrs
Total efficiency: 65%
OUTPUT (per drive motor)
Angular Velocity 3.9 rad/s
Torque* 130 kgf/cm
Total Power .066 hp
Maximum current 4.2 A
Battery Pack 16.5 AH
I guess from that it looks like 2
Banebots 12V 263RPM 2527oz-in Planetary Gearmotor w/RS-540 Motor
and perhaps the
Dimension Engineering Sabertooth Dual 25A 6V-24V Regenerative Motor Driver
(unless there is something smaller)
and then I just need wheels and hub mounts?
Or do you think I’m over-engineering this puppy?
Whoa, this is really adding up. Why couldn’t I use the dual motor controller I listed above? I’ll find some other wheels to use.
I have an idea for eliminating the buried wire fence. Are there shaft encoders available for these motors?
Ideally, using all the known values of your mower project, use the Motor Sizing Tool to determine the motor you require. From this we can suggest a controller, hubs to mount wheels to the motor shafts and the wheels themselves. Banebots has wheel/hub/motor solutions that are as easy as 1-2-3. You may opt for a different type of wheel, or even custom cut metal spikes to bolt onto regular wheels for better traction, like on the LawnBott.
Hi ZebZiggle,
RB-Ban-31 (Banebots 12V 263RPM 2527oz-in Planetary Gearmotor w/RS-540 Motor) is certainly a powerful motor. Note however that the specifications are the maximum the motor can provide (2527oz-in is the stall torque). This means that when it encounters a 20 degree incline for extended periods, the motor may burn. Although not yet on our website, banebots has finally released their new line of planetary gearboxes for beta testing which can handle RS-540 to RS-555 motors. If you are interested, we can place a special order. You can power both using the RB-Dim-06 (Dimension Engineering SyRen 25A 6V-24V Regenerative Motor Driver). To move an object on level ground does not require much force until you factor in friction - which in this case might be wet grass. You also can see that as soon as you factor in an incline, the forces increase drastically. For a prototype. it is best to include a safety factor (of sorts) and increase the motor size/power.
With regard to wheels and hubs, since you have a large wheel, you can connect the RB-Ban-31 using a stardard sized hub such as the AndyMark 375 Key Hub. Unfortunately we do not carry any 10" wheels, though the Andymark 6" Plaction wheel might work well. We can also be your source for all the raw materials you need to build your robot.
Hope this helps,
Hi ZebZiggle,
You certainly could use the Dimension Engineering Sabertooth you indicated before. It is always good to know you have options (different regenerative capabilities for not a significant price difference). Some Banebots motors have optional encoders, it depends on which motor most closely meets your needs.
