Tuesday, April 24, 2012

Walking With Mindstorms

Making a walking robot is another unique challenge that can be tackled with Mindstorms. The above picture is a set of legs I built, adapting a design I saw in this book.

I explain how the above system works in this video:

video
The other important concept to keep in mind as you design a walking robot, is COG; or center of gravity. Because only one foot of your robot will be on the ground at a given time, you'll either need to find a way to shift the COG over a single side, or you'll need to alternate the leg placements on either side, allowing for a successful walk, devoid of awkward falls and lurches.

Sunday, April 22, 2012

My Lego Mindstorms Creations

Really really really cool video I found. This guy details his mindstorm creations, and some of them are really neat designs. Check it out!


Tuesday, April 17, 2012

Apologies

I'm really sorry for not updating this thing in a while...been a really busy week for me. Stay tuned because I have a couple of really neat posts set up for later this week!

Thanks!

Sunday, April 8, 2012

Concept Vehicle: ATV

I've always had an interest in ATV's and there are numerous necessities I've found that are required to build a successful one:

- Power/Torque (any speed is just bonus)
- Flexible chassis (stiff vehicles get stuck and lose traction)
- Good suspension system (goes along with above; as suspension systems enable you to keep traction)

Trying to implement all these into a Lego robot, I came up with this:


This is a concept ATV I made out of Mindstorms, I followed the three guidelines I set for myself above, and I'll explain all of them in further detail here in this post.

1. The drive system- Power and torque are essential in an ATV, as the motor must be able to push the robot across any terrain. If you recall an earlier post, I demonstrated how you can get power through gear ratios. I utilized a worm gear meshed with a 24t gear to give me a ridiculous 1:24 gear ratio. That's 24x the power the motor is outputting.
Example of a worm gear              
I transferred the motors power into the worm gear, which turned the 24t in a gearbox that came standard with my RCX. So though I dealt with a low speed bot, the power that came with it was extremely helpful.


The gearbox 
2. A flexible chassis- I put this as a guideline for myself because I felt like without a certain degree of flexibility from your robot, Mindstorm bots can be prone to getting stuck on uneven terrain. Adding a degree of rotation on your chassis helps keep this from occurring.

To achieve this, I simply built the chassis in two separate parts; the drive system, and the suspension mount. This way I was able to lock the two together using two single beams, adding a degree of flexibility.

The rotation radius of the bot is illustrated in these two pictures of the chassis.






3. A suspension system- A good suspension system is NECESSARY for an ATV. Unfortunately these are a bit tricky to build out of Mindstorm parts. I found an interesting solution using the rubber bands found in many kits, and attached the front two wheels to independently attached mounted suspension beams, supported by said rubber bands. By inverting the system, you have a make-shift suspension.

Normal drive
There are other guidelines into making a successful ATV as well, however these should get you going for now.

Send me pictures of your own ATV's! ashwin.johri@gmail.com
Happy building guys.





Suspension flex

Monday, April 2, 2012

Building a Steering Drive

Steering is an essential component of building a Robot. What fun is a machine that can only go forwards and backwards? 

There are a lot of different ways to steer a robot, and one of the most common one is to build a rack and pinion steering drive. The steering drive is used by basically anything with a steering wheel, it's set up so that a gear on the end of the wheel (called a pinion) is meshed with a rack connected to the wheels. 

The rack is set up such that there are two degrees of motion, on either side of the set-up, and there's also a non-moving piece to give the wheels something to rotate around. Here's a good (non-lego) diagram of the system:




Now implementing the rack and pinion system into Lego form is tricky, but there are tons of unique solutions out there that I encourage you to take a look at. A quick google search of "Lego Steering Drive" will pull up some really cool results. 

In an effort to demonstrate on possible model for a Lego steering drive, I built this: 



The steering shaft is controlled by an independent motor, and by playing with the rack sizes, and wheel spacing, you can manipulate the turn radius as well. Building a solid chassis is important for steering drives, as they can quickly become heavy, and excessive moving parts can put stress on a robot. I locked mine with perpendicular blocks you can see laying across the underside, beneath the steering column. 

Here's a view on the pinion gear meshed with the rack, it's important to make sure the pinion has enough torque to turn the whole system. Locking gears, and jammed motors are a nightmare to builders.



Steering drives, while not an easy build for most people, really provide versatility to the bots you make. In the future, we'll explore some more steering systems, like the differential pivot wheel, and reversing motors. 
I'll leave you with a video displaying the turning radius and the piece movement involved with the execution of the drive: