Quote:
Originally Posted by Nathan
Thanks for your replies, everyone, we really appreciate your help!
Here's a little more information to clarify a few things:
- We're wanting to use normal wheels (not a holonomic drive) and steering like on a car
- We had a mechanical engineer give a presentation to our club and he also recommended Ackermann steering, so we'll be trying to implement it somehow with a servo
- We'll be using a cRIO for the control system
- We estimated that the weight should be around 30lbs, but to be safe we should probably plan for twice that, or 60lbs
- If we end up using FIRST motors, then we'll probably get one of the standard batteries that FIRST robots use (12V motorcycle battery?), as long as that doesn't put us way over our weight limit
Wow, that looks like it might be really helpful. Thank you!
Thanks for your help! Here's some more information:
- The weight we're shooting for is 30lbs (not sure how realistic this is..), so let's plan for up to 60lbs
- The maximum speed needs to be at least 4 mph, but we'd like it to go up to 6 mph
- I'm not sure on acceleration, but it's not a huge issue since speed isn't our primary concern
- We need it to be battery operated. What type of battery we use mainly depends on how much power the motors draw, so we don't know what battery we'll be using yet
- We'd like an operating time of at least 20 minutes of running non-stop, which would hopefully translate to at least 40 minutes of on and off use. Obviously a longer running time is preferred, though!
- We'll be using a cRIO as the control system and will have a couple of low power sensors and some kind of camera (possibly an Xbox Kinect)
- We need at least 2" of ground clearance, so we were planning on using 6" wheels
So far we've had these motors recommended: - Banebot (possibly with a 4:1 or a 16:1 ratio)
- BAG motors with the versaPlanetary gearbox of 10:1 (but they might be bad, according to a few)
- miniCIM in a versa-planetary
Where do you all buy your parts from? Is there any particular place you recommend? |
For the batteries, here is a good alternative to the standard ones!
http://www.andymark.com/product-p/am-0844.htm
Also, Yes, I agree with stinglikeabee that 30 pounds is unreasonable. MiniCIMs weigh 2.16 pounds, themselves, meaning that using two of these is 4.32 pounds! Then, you have the weight of your transmission and wheels. After that, you have your chassey. Then comes your Control system, which typically isn't too light! Then, you have you battery, which is more-or-less a block of lead
. You will find it hard to fit it into 30 pounds. Also, if you go for 60 pounds, fill up the rest of the weight with more batteries to give you the runtime! If you are aiming for that high of a runtime, you will probably need to use Lithium Ion, or LiS/Li-Air/LiHOH, if they release that technology anytime soon
Here's a link to PolyPlus, developing some Lithium technologies
http://www.polyplus.com/
For the Gearbox/motor:
6 Inch wheels means .5 ft. = 2turns/foot
1 Mile is equal to 5280 ft.
6 miles = 31680 ft. * 2 = 63360 rph (rotations/hour)
63360 rhp / 60 = 1056 rpm
You need to get your motors to 1056 rpm! That means that a MiniCIM will be able to give the RPM at a max of 1:6 reduction gearbox!
A versa planetary with 1:5 reduction shall do the work and actually get the car to possibly 7mph!
However, at 60 pounds, you would be stressing the motor/gearbox a lot, so you may need two MiniCIMs working simultaneously!
If you use four MiniCIMs, you should get a punchy throttle!
With a Kinect, you will probably need a coprocessor, requiring a UPS for safe shutdown, and other complexities. Unless you are really good at OpenKinect of OpenNI or another vision suite, this is very advanced! The cRIO can process the images from the AXIS Camera!
I hope that you found this useful!
Please let me know if I did any math wrong
Sorry about the double-post. I didn't know how to multi-quote!
