As some of you noticed, I’ve been asking a few questions here and there. And a few of you have asked what’s up. Well, I’ve been doing some brainstorming regarding an all-direction drive system (I think you all have a special term for it; but for the life of me it escapes me).
It seems that the simplest and easiest way is to employ the use of omniwheels setup in a perpendicular fashion. But I’m not keen on the idea of splitting up the motor power of the robot between the two directions. Nor the seemingly lack of traction when compared to some other robots (as you really only have two wheels that will be opposing the force; the other two will just roll with it)
So this is what I came up with for my ideal drive system:
All the wheels can steer 360 degrees
All the wheels can individually go forwards or backwards while having a single motor set, gearbox, and transmission power ALL the wheels.
At least a two speed transmission (though to be honest, I’d really like to have an ULTRA-low gear as well)
All the wheels can steer 360 degrees
After thinking about this one, I figured there’s no point to having the wheels steer individually; that is, to be able to have them facing different directions. While the thought of having them all opposing each other in order to combat being pushed, I figured it might be better to instead have them turn in the direction of the force and use the motors to push back.
So I came to the conclusion to develop a steering system in which turns ALL of the wheels simultaneously. I concocted one system (that has two variations) that seems to do the trick. I’ll probably post another animation of it when I get the chance to model it (probably tomorrow evening), so I’ll come back to this later.
- All the wheels can individually go forwards or backwards while having a single motor set, gearbox, and transmission power ALL the wheels.
This is one of the bigger problems I’ve been facing. When I was putting such a drive system through the ropes (in my head) it dawned on me that as the wheels turn, in order for the robot to spin, the wheels that turn backwards/forwards change. That is, say the wheels are all pointing forward and you want to turn right, well, simply you spin the left wheels forward, and the right wheels backwards. Voila. So I originally thought to have two drive systems; one for the left wheels, one for the right wheels. BUT, say the wheels are all facing left: now you want the forward wheels to spin backwards, and the rear wheels to spin forwards in order to turn the robot.
So now I’m faced with two choices: a) Build a motor-mount, gear box, and transmission for EACH of the four wheels
b) Use a single motor-mount, gear box, and transmission that would power ALL the wheels simultaneously AND develop some sort of method to reverse that power for individual wheels.
And personally, while a) MIGHT be the more feasible choice… to my knowledge, option b) hasn’t been explored much. And it might turn out to be a good choice too; this would save grief having to build four gear boxes, four motor mounts, and four transmissions. Plus I like a challenge; I want to see it done
- At least a two speed transmission (though to be honest, I’d really like to have an ULTRA-low gear as well)
I hope this is pretty self explanatory. Ultimately, in a perfect world, I would like to have a high speed, low-speed/high torque, and an ultra-low-speed/ultra-high-torque gears. I want this drive train to get down and dirty; and if need be, it will drive slow… but it will certainly move whatever is infront of it.
Now, with regards to 1), I do have a question concerning the idea in my head. I can’t elaborate on the idea now, but I will tomorrow evening when I get the time to. But just a quick question: I see chains used all the time; but always in a vertical fashion. Is it feasible to have the chains run horizontally? Or will it be very prone to slipping off the sprockets? If so, what can one do to counteract that from happening?
In regards to 2), you can read up on my “reverse gear” thread here: http://www.chiefdelphi.com/forums/showthread.php?t=28174
And finally, in regards to 3), I saw the team 222 3 shifter design that has balls pop out of the shaft to engage the proper gear. (http://www.chiefdelphi.com/forums/showthread.php?threadid=26630) That seems like a grand idea; I really like it. But I also read some cautions regarding the design. You think the design is quite alright to use so long as you take the proper precautions (i.e. material selection/lubrication)? Any other three shifters? Maybe I can use that 4 speed automatic shifter Though to be honest; I prefer to have the shifting in the power of the driver, so if I did implement that, I’d program in an override switch. You think it’d be simplist just to use a single small pneumatic to engage a 2nd gear instead? Beauty part of this is I want to have only ONE transmission in the robot; no need to build two transmissions and mount double the parts.
So yeah; I’m a newcomer to mechanical engineering, so I’m looking for your input; and so far it’s been great! And I have one problem that seems to be just out of my reach right now. And that is transferring the power of the motors (from a fixed shaft… or gear… or chain, or what-have-you) to a 360-degree spinning wheel. I’m sure it’s been done before, but I haven’t seen any threads (though admitadly, I didn’t look through ALL of them… but a half decent number none-the-less) regarding that issue.
So thanks again on any input and advice you can toss my way! You’ve been a great help so far!