11-02-2005 17:15

sanddrag

Re: pic: Steering mechanism

The steering is very interesting, but what I'm even more curious about is how did you adapt to the strange gear on the jideco motor?

11-02-2005 19:03

Rick TYler

Re: pic: Steering mechanism

Pretty cool. Most teams use tank steering. How did you decide to use "automobile" steering instead?

11-02-2005 23:10

CRAZYMADI

Re: pic: Steering mechanism

The gear is biult to give more revolution per mintue to our four-wheel steerign drive. Keeping in mind that there will be six robots on the field at the same time, Robots must move on sharp angles and possibly on faster pase. Our steering system fulfil the requirements and is pretty light. So far with the gear boxes, four wheel steering system and arm, we are still under 115 lbs.

11-02-2005 23:17

Lil' Lavery

Re: pic: Steering mechanism

Nice. Typically you only see tank or "skid" stearing, or a form of omni-drive. Occasionally a robot who can "crab drive" or strafe too(especially in stack attack). But very rarely akerman(sp?) steering.

11-02-2005 23:19

sanddrag

Re: pic: Steering mechanism

Team's that I remember having it are Crescenta Valley 589 in 2003 and Archer (#?) in 2004.

11-02-2005 23:42

Greg Perkins

Re: pic: Steering mechanism

this kinda looks like what 121 did in 2001.

except they made their robot turn in the middle via a vandoor motor. basically 4 wd with tthe robot looking like this...>o<... with the <'s being the wheels and chassis, and the o is the pivot...

it was pretty amazing

i like this approach to driving, most drivers allready own a car (or drive one) so any time a car steering system comes up its second nature.

13-02-2005 11:40

jskene

Re: pic: Steering mechanism

Yes, this type of steering mechanism is referred to as Ackerman steering. Each wheel turns around its own turning axle, in our case both the front and rear wheels turn, so we get a very small steering radius.

Due to the sharp turning angle we have (45 degrees), the fact that we turn all 4 wheels, and the extreme grip of our tires on carpet (coefficient of friction is about 1.2!), we cannot tolerate any slip angle (difference between the angle the wheel is actually turned to and the angle it should be turned to to remain tangent to the turning circle), so we had to make the inside and outside wheels turn different amounts, so they remain tangent to the circumference of the turning circle they are supposed to follow.

It makes for some interesting mechanical design, as well as some neat programming.

Here is a photo of the steering shafts (note that we also have 4 wheel drive in addition to 4 wheel steering):

The steering arms of the left wheels are connected together, so their steering angle is identical. The same is done on the right wheels. The left and right sides are driven by independent steering motors, each with its own steering angle sensor. When the driver pushes the joystick to the left, say 20°, the left wheels become the inside wheels, and the left steering motor turns the wheels to the desired 20° steering angle, as measured by a potentiometer connected to the steering axle.

So, referring to the diagram below, we can calculate θo as follows:

We are also using an electronic differential, by setting the relative speed of the inside and outside motors to be proportional to their respective turn radii.

We also plan to add speed-sensitive steering, so at high speed the ratio between joystick angle and turn angle is reduced. Hopefully that will minimize the chance of flipping over with our 100" arm extended.

13-02-2005 12:02

Mirza95vx

Re: pic: Steering mechanism

pretty sweet. Very diffrent and original

13-02-2005 13:24

jskene

Re: pic: Steering mechanism - Jideco gear adapter

We CNC machined an adapter out of delrin. Email me if you want the G-code. We also did one for the Denso window motor, as the one FIRST provides is a bit bulky.

13-02-2005 14:19

Jeff K.

Re: pic: Steering mechanism

Whoa, that is insanely cool...But will it last all of the competitions?

13-02-2005 14:23

jrocket567

Re: pic: Steering mechanism

one word to describe it: wow ... thats incredible.. that must be one heck of a program to determine everything that fast.. hope yall will be at VCU, can't wait to see it!

13-02-2005 15:05

jskene

Re: pic: Steering mechanism

Yes, we will be at VCU, also in Atlanta.

13-02-2005 15:36

Fixen

Re: pic: Steering mechanism

This is just downright awesome. Akkerman steering is something I didn't expect in this competition.

If you guys don't win the regionals, you'd at least awe the people.

13-02-2005 19:05

psquared

Re: pic: Steering mechanism

very nice design, that whole programming team must be really amazing

14-02-2005 23:03

CRAZYMADI

Re: pic: Steering mechanism

Our team have worked pretty hard on the steering system. There is still a lot to be unviel about our robot. Out robot will be ready by Feb 19th. We will be testign it in DC scrimmage. Good luck with rest of the season.

17-02-2005 23:20

CRAZYMADI

Re: pic: Steering mechanism

yeah, the programming team is really kool........
especially when it comes to Autonomous Code.