Using Multiple Kinds Of Motors
 

Since some motors have a higher torque, others have higher speed, isn't it a good idea to use both to drive the same robot? My team has never attempted this (or that I am aware of), would it be a good idea? According to the First Wiki, the Fisher Price motor has a higher speed, significantly higher. The CIM has a significantly higher torque. Now isn't it possible to make a mechanism that will switch the motors? Switching the motors to fit the needs of the situation. Car manufactures do it, for example the hybrid vehicles. They use both electrical motors and the traditional engines. They must have a mechanism to switch gears.

I have an idea for a mechanism that uses pneumatics and gears, but does not seem very reliable.

Now would it be really worth the trouble to make a mechanism to switch motors? Does the benefits outweigh the drawbacks?

Pros:
Best of both worlds


Cons:
Weight
Mechanism can be the weak point (more moving parts mean more chances of breaking down)
Seems like a redundant way to do something while gears ratios can be adjusted

Re: Using Multiple Kinds Of Motors
 

I can think of a way to do that without switching motors. Several, actually, but one should provide the idea.

http://www.andymark.biz/am-0114.html

Also see the Nothing But Dewalts whitepaper and team 33's 4-speed design.

Simpler than switching motors.

Re: Using Multiple Kinds Of Motors
 

Ultimately, all motors contribute is power. To paraphrase the great Dr. Joe, who posted something pretty cool that I couldn't find searching, speed and torque are "accidents of birth" - motors really only contribute power. You can trade speed for torque and vice versa with gear reductions. That's the whole idea behind transmissions and shifting gears. If you want more torque and more speed than you could find at a single balance point, you shift gears.

Shifting actual motors makes a lot less sense. First, when would you ever want less power in your drivetrain? Putting an FP in a CIM's place would just mean you would have to gear it slower to get the same torque. I just can't see a situation you'd ever want less torque.

In addition to that, you're limited to a fixed number of motors, and using more of the "best" motors when you could just shift gears seems a little trivial.

Re: Using Multiple Kinds Of Motors
 

Analogous to how batteries or a wall outlet supply power in an electrical circuit (power=voltage x current), motors only provide power into an mechanical system (power = torque x rotational speed). Since they use similar amounts of power you could use one to for slower speeds and one for faster speeds. All your doing is making a two speed shifter almost copying the effect of the AM Super Shifter or any other two speed transmission because all you are doing is changing the output speed but not the power. This isn't practical because you could just get a shifter and put both motors into it (compensating for different speeds of course) and get the same effect but double the power. Though you are correct that you could do it really just isn't practical.

About the Hybrids depending the type of drivetrain (parallel, series, or power-split) they may or may not necessarily switch between the motor and ICE (internal combustion engine). In a parallel hybrid the Motor and the ICE are simultaneously providing power to the drivetrain. In a series hybrid the motors provide all of the driving power and the ICE can act as a generator. The power-split hybrid is what you are talking about and yes they are more efficient than the others but only because the differences in energy consumption allows the motor to work for lower speeds (lowering power consumption) and the ICE and Motor to work at high speeds/loads (consuming more power) are so vast compared to the Fisher Price and CIM. This really results in having lower (than a conventional ICE car) torque at low speeds and higher torque at high speeds.

Re: Using Multiple Kinds Of Motors
 

I recommend looking at Paul Copioli's Motor Drive presentation as it does a good job explaining the relationship between speed, torque, and power. It also explains how to match different motors into a single gearbox which is what I think you really want to do instead of swapping motors.

Re: Using Multiple Kinds Of Motors
 

BTW you all realized "Team Role: Programmer".
I have had different types of drive trains on my mind, but I want to incorporate the most unique and strange drive systems. What about a system without wheels at all? I want to take the whole "Innovate not imitate" to the max here. I thought using multiple would be cooler than just one

Re: Using Multiple Kinds Of Motors
 

I can understand your desire to innovate so here is something to think about.

A fundamental problem with FIRST robots are that not all the motors are being used all the time. This means that there is a lot of untapped power at any given time. If one was able to put all motors into whatever function(s) were needed at the time, it would be revolutionary.

That would be about as good as a drivetrain could get motor/power wise.

The trick to designing is to identify the problem before finding a solution.

Re: Using Multiple Kinds Of Motors
 

Engineering isn't always about innovation.

I would suggest that you look at all you options, but the 6 and 8 wheel drivetrains that have been created recently are a very strong base on which to build an optimized system. I also wouldn't be so quick to allocate a bunch of motors to drive, seeing as how drive barely ever scores points on its own.

Also, FPs seem to like blowing up under heavy load, so if you are going to drive a robot with just FPs in 'high gear', I would recommend significant amounts of loaded testing.

Re: Using Multiple Kinds Of Motors
 

Before we were able to use more than two CIMs, everyone had to improvise. I believe our 2003 Championship robot had Cims in two wheels and FP in the other two wheels, geared accordingly, of course.

Re: Using Multiple Kinds Of Motors
 

First, what ChrisIsMe said.
Then, what BJC said.

The issue is defining the problem. Do you really want all possible energy being put into the drivetrain? Is it needed and, if so, to what end? Can the drivetrain do something useful(er) with all that power?

Way back before small electric motors were available, workshops all worked off one single power source - a water wheel, steam engine, gasoline engine or (large) electric motor - with a shaft that ran the length of the shop. Each machine had a long leather belt that took power from the shop shaft (with a clutch that could be disengaged when desired). In this way, all of the power was available to any machine that needed it, or a fraction was available to every machine in the shop.

What if you built a robot that shared ALL the mechanical power like that?

Re: Using Multiple Kinds Of Motors
 

Brooks "Design of Design"

"He who seeks originality will often find novelty, but not great design."

The Pet Rock was very original, but not necessarily a great thing.

As BJC said, good design begins by asking questions.
What would you want to create? The most agile? The fastest? The most powerful pusher? The best balance? Even "most original" would require knowledge of what others have done. Otherwise, you would find yourself talking about this great, original design that someone else ahs done.

Study "good" examples. What do you like about them? What do you not like about them? How could you/would you do things different?

Re: Using Multiple Kinds Of Motors
 

For the 2010 season, the 968/254 robots used a power takeoff to have one set of motors/gearboxes powering both the drivetrain, and the lifting arm. I believe 973 used a similar design as well.

Team 60/254 had a power takeoff in 2004 to power a winch which lifted the robot from the ground at the end of the match.

I'm not aware of any FRC robot that has been centrally driven through one power unit.

Re: Using Multiple Kinds Of Motors
 

You do make a great point, one great example is the Shake Weight... Its useless.

Now if I wanted to innovate what would be the best thing to innovate? Depending on the game, I would have to talk to my team about it. Most will think I am crazy, but I got to say, I can make a big impact by getting the new people on my side. I really wanna be crazy this year, have a blast while making a non relevant robot. I want people to way "WTF is that?" kind of response and then kick $@#$@#$@# at the competitions. I really want to move away from the traditional chassis too, maybe having a triangular pyramid?

Re: Using Multiple Kinds Of Motors
 

Innovation is not inherently bad, but I feel you may want to master the basics first. Once you do, you can understand why certain shapes, techniques, methods, etc.. are effective and commonly reused.

Re: Using Multiple Kinds Of Motors
 

^ this guy is a fun one to bug :p . I love starting to have our team known for playing the game in crazy ways. But regardless of how we accomplish a task, if a way exists to be better at that task we will do it (even if it stresses out the team moms and makes them want to strangle me).

Lots of crazy ideas are thrown into our design discussions, but our filter of what could possibly work is a lot less restrictive than most teams. Which yields some pretty fun and odd things making it through, but they have to have potential in reality to make it to the next step.

Regardless of how much I want to make some really crazy things, they'll only happen if they fit that task at hand.

Re: Using Multiple Kinds Of Motors
 

Dave, have you ever considered that perhaps having a rock solid drive system would be beneficial to something complex? Perfection of a system comes not when you can add nothing more but instead when you can remove nothing. As you said, you are a programmer, as a programmer you aren't terribly familiar with mechanical systems (this is an assumption). Perhaps you should start by figuring out what you can remove from last years drive train to make it better. This would allow you to learn more (which will help you in the future when you show us your awesome new drive system) and help your team because a better drive system is ALWAYS a good thing.

Re: Using Multiple Kinds Of Motors
 

I just noticed your usertitle... Don't go stirring up trouble now, simple, simple, simple. It's the way to go.

Re: Using Multiple Kinds Of Motors
 

Our drive system was very basic, I mean very basic... 6 wheels with 2 motors, what can you take away from that? I did not like how it was so basic, it was too much of a conformist approach for me. Of course, me being the new kid with no idea how the competition would be, I did not speak out as much as I should have. It was a terrible system, can't go over bumps, can't drive under tunnel (well it can but it can take a while to get it right). Now the leader graduated (he never liked my ideas LOL) I can step it up even more.


I might even hold off on forcing my ideas a bit though, me talking too much last year might have intimidated some people.


Yea I am not a very mechanical person, well its not awfully hard to learn.

Re: Using Multiple Kinds Of Motors
 

Going back to the problem before the answer thing. What do you want out of you drivetrain? It sounds like you currently just want it to be different then normal?

I would suggest looking at things that could be improved within your current drivetrain.

How to increase your robots tractive force?

How to make your robot more manuverable? (strafing or just turning)

How to make it weigh less?

How to make it more easily repairable?

How to get your CoG lower?

How to get up an incline?

How to make it able to stand its ground when hit from the side?

Ect.

So if your robot needs to be a triangle to better do some of these, then you should make it a triangle.
Because I gurantee you that if you can do some of these things, even if they arn't visible at first glance, you will have a more competitive robot and people will notice the difference.

Re: Using Multiple Kinds Of Motors
 

It was clear that a standard tank drive system could do everything in Breakaway and more this year. If you want an effective drive, take what you had last year and make it do the things it didn't. Conforming to an intelligent design is almost always a good idea.

And if you think being a Mechanical guy is easy, you are right. But being a great one takes just as much work as being a great programmer. The only way to really know what you are doing mechanically with an FRC robot is hands on experience, reading good mech threads on CD, learning a lot of physics and engineering concepts, and being able to weave it all together into a basis for common sense decisions (which, although known to be 'common', never is).

If you intend on building a winning robot, simplicity in the drive is one of the best ways of getting there. Ask 1114, they have been doing it since 2005.

Re: Using Multiple Kinds Of Motors
 

In my opinion I think a really innovative and cool drive train would be one that incorporates a fully mechanical Continuously Variable Transmission or even better the Infinitely variable transmission. I do not know if it would be useful and give any real advantage but it would still be awesome.

Re: Using Multiple Kinds Of Motors
 

"If it ain't broke, it don't have enough features."--engineer's thinking

"If it ain't broke, don't fix it."--everybody else's thinking

Sometimes, non-engineers are right about engineers putting complexity into things. Make things as simple as they need to be, but not simpler. If you need extra speeds, use a shifting gearbox, not a single-speed gearbox.

For next year, try a 6WD 4 CIM shifting transmission. Bonus for building a Killer Bee 4-speed; I haven't heard of one being used in years. (Double bonus for making it better/simpler.)

Re: Using Multiple Kinds Of Motors
 

There's a pretty big difference between "conformity" and "going with what works". Eschewing any used idea as "conformist" misses the point entirely of why some choose not to conform.

The danger of conformity is not in rehashing others, but in doing the same thing over and over again without bothering to ask "why". However, no matter how little you want to conform, if you aim not to conform without bothering to ask "why not", you're just as flawed, if not moreso, in your judgement than anyone who's ever conformed.

That aside, there's a reason that robots have things in common, and when a lot of people do something, if you're seriously considering something different you'd be foolish not to understand the pros and cons of a normal design. There are a lot of pitfalls to innovation and if the simple, boring solution works perfectly, it's bad engineering not to go with what works.

Re: Using Multiple Kinds Of Motors
 

Another person's random ramblings on "creativity for the sake of creativity":

I love coming up with creative designs. Who doesn't? Its one of the most fun parts of the design process! There's something special about that feeling of "I thought of something no one else did." And, creativity is responsible for every improvement to a technology in the history of mankind. Behind every improvement, whether a tiny optimization to a well established system, or a radical new direction, there was someone thinking "Now how could I do this differently?"

I have to disagree with some of the stronger-worded posts stating that innovation and creativity are not always the best options. If they weren't, how would we move forward?

But, you have to be sure that you're moving forward, and not backwards, which is the point many have been trying to make. Just because something is different, doesn't mean it's better. And to check if a new idea is "better" we use the engineering design process: have a clearly defined problem, and criteria which the solution must meet. In the case of an established system, like a drivetrain, the "problem" is a perceived deficiency of the "standard" system.

Most of the time, you'll go about this process very methodically: Defining a problem, coming up with criteria, developing possible solutions, testing, and improving these solutions. This process works well on small-scale improvements, but is more difficult to apply to Out-of-Left-Field ideas.

But sometimes, a creative spark can cause the thing to happen in reverse. A random, "different for the sake of difference" idea is worthless in itself. But, when compared, very objectively, to the original solution, you might find that it is in fact superior in some way. This is a great way to discover "problems," that you may not have percieved as problems in the past! Maybe no one has! And if it solves a problem that no one else gave a second glance to, more power to you in competition!

But, don't take this as an endorsement of the creative idea over the standard. By all means, think about them, give them a chance, and compare them objectively to the established designs. If they are better, then they are better. If they are not, then they are not. Simple as that.

I'll also give creativity the point that they stand out of a crowd. Which for some people, is a big part of what they go into these competitions hoping to achieve. But in terms of pure competition, the success of a creative design is measured by its contribution to a winning robot, not the level of creativity itself.

Lets look at your motor-switcher idea in these terms. Its different, yes. But what does it solve, that a shifting gearbox does not? Is it more efficient? Is it more powerful? Does it use more or less motors? Is it less prone to failure? Are its failure modes more or less catastrophic than those of a shifter? Does it require a pneumatics system? Is it harder, or easier on the motors heat-wise? Machining effort? Cost? Size? Weight?

You can ask these questions, and a hundred more. Some of the answers will favor the shifter, and some will favor your design. You have to weigh the pros and cons of each. In this case, it seems fairly clear that the shifter wins. But that isn't always going to be the case.

Never stop innovation.

Re: Using Multiple Kinds Of Motors
 

Where can I learn all the basics of all this? Transmissions and all that. preferably a book

Re: Using Multiple Kinds Of Motors
 

If it is non-relevant then how is it going to be effective in competitions?

Jane

P.S. a suggestion would be to think about the use of your words and their impact when developing your leadership skills with a team.

Re: Using Multiple Kinds Of Motors
 

Initially, you need to learn about traction (friction) and the relationship of rotational speed to ground speed. Then you need to learn the relationship of torque, rotational speed, and power. Also and understand of how force, mass, acceleration are related, and the relationship of acceleration, speed, and distance covered. This can be found in most good physics books. Especially the Freshman Engineering Physics text at your local university book store.
Next step is understanding the fundamentals of gearing. Learn how to calcualte speed ratios for simple gear trains and pulley or chain drives. Learn how these ratios multipy and divide torque and speed, but essentially keep power at a constant (with a small loss per stage). There are lots of good books on this. A decent physics book should cover this as well.
Important to note, most of the engineering population stops here in understanding powertrain design.
From this point you could dive into a Mechanical Power Transmission book, a Machine Design Book (Norton and Shigley have two different books, and both are quite good). This is college curriculum type stuff.

Honestly though, buying a used physics book and reading it would be great, but the internet is a great source for more detailed information.

http://science.howstuffworks.com/tra...pment/gear.htm
is a great article explaining the basics on gears.

If you are looking for innovative power transmission solutions, learn how the PRIUS transmission differs from other automatics. Learn the difference between a CVT and an IVT. Learn about "split power" or "power Recirculating" transmissions. Check out farm equipment. Their specialized purposes tend to be closer to FRC than normal cars and trucks.

OR

To paraphrase:
"You can see farther by standing on the shoulders of giants that came before you."
Find teams whose robot behaves the way you like. See what they are doing and talk to them about why they do it that way. FIRST (of last 10 or so years) is very good about sharing information.

As others keep saying over and over though, the most important part is figuring out what you want it to do rather than how to make it do what you want.
I have seen many teams shoot for the creativity award only to end up standing on the sidelines Saturday afternoon.

Re: Using Multiple Kinds Of Motors
 

Ike is right, even a quick glance through the CD Media section found:

http://www.chiefdelphi.com/media/papers/1682 - Drive Train Presentation by Ken Patton and Paul Copioli
http://www.chiefdelphi.com/media/papers/1443 - Drive Train Basics paper by Chris Hibner (Math heavy)
http://www.chiefdelphi.com/media/papers/1552 - SimSwerve paper by Ian Mackenzie
http://www.chiefdelphi.com/media/papers/2216 - Belt and Chain evaluation by Team 234
http://www.chiefdelphi.com/media/papers/2147 - Conference Presentation by Madison on Drive Trains and Implementations. (http://www.chiefdelphi.com/media/papers/2037 - older version with more pictures)

These are just the ones I have read and found helpful. I am not sure what your grasp of physics is but I have a pretty strong background in it (even if it is several years old and I don't use it very often) If you don't have one I highly suggest taking a class on it.

If that isn't an option http://botsnlinux.net/firstphysics/f...th_physics.pdf is a short primer on basic concepts that is probably worth a read. Unfortunately development seems to have stopped on it.

Re: Using Multiple Kinds Of Motors
 

Ok so you are saying I will eventually learn that in my AP Physics class?

Re: Using Multiple Kinds Of Motors
 

Learning is up to the student, but many AP physics classes will cover this material. Look through the book, and then discuss the curriculum with your teacher.

Re: Using Multiple Kinds Of Motors
 

I don't think some of the other responses here were referring to the fact that innovation should be halted. I think the point they were getting at is that very seldom does actively seeking out innovation lead to genuinely useful innovation.

Like you said, sometimes being creative for the sake of being creative is okay, but I think that being creative, and being innovative are entirely different things.

-Brando