Future Control System

Posted by John Cunningham, Engineer on team #00 from FIRST.

Posted on 4/1/99 11:19 AM MST

Hello All,

Because of the power of this forum, I would like to pose this question here.

In the future, FIRST will upgrade it’s control system. Some things will stay the same and others will change. What I would like to know is what you think is good about the robot controllers, what needs work, or what you think should be done away with completely.

Some things to keep in mind are to keep answers practical, and remember that FIRST is on a limited budget because it is a non-profit organization.

I thank you in advance for your thoughts, and am looking forward to reading your ideas.

Sincerely,
John Cunnigham

Posted by Chris, Coach on team #308, Walled Lake Monster, from Walled Lake Schools and TRW Automotive Electronics.

Posted on 4/1/99 1:15 PM MST

In Reply to: Future Control System posted by John Cunningham on 4/1/99 11:19 AM MST:

I’ve posted something about this a long time ago. I’ll try and remember everything I said and state it again here.

First and foremost, a more powerful microcontroller is needed. Maybe not as a standard feature, but maybe as an option. The terribly slow loop time (not to mention variable loop time) really limits a team from doing any good automatic control through the feedback sensors. Sure, some control can be done, but not much that would be considered good in the real world. Adding four filters is just about enough to slow the thing to an unusable loop time.

I would like to see some teams given the option of using something that you can program in Assembly or C. Perhaps not all teams will have the people with the software know how to do this, which is why it should be an option. Also, to me, that would help level the playing field some. I work at an Automotive Electronics place, and we have very few mechanincal engineers. We end up having somewhat of a disadvantage in the mechanical department compared to a lot of teams. However, we have great strenghts in control theory and software, but we can’t use this to our advantage because of the microcontroller. If we had this option, we could have an advantage in the control of the robot that would help neutralize the advantage that Beatty has in building machines.

I’m not asking for pentiums to be put on the control board, but maybe a Motorola HC11, HC16, or something in that class.

To go along with that, if a team wants to use control, you have to use PWM outputs, so more PWM outputs would be nice.

One last thing: more (and more useful) sensors would be nice. The yaw sensors this year were a great adition, but the maximum yaw rate that they would sense was terrible for many of the applications. We wanted to use the yaw sensors to aid the drive train, but our robot turns at about 5 times the yaw rate that the sensor could measure, rendering the sensor virtually useless. We tried doing some things in software to make up for it, but the resolution of the sensor data became so bad that it was, once again, useless. Not to mention that the slow microcontroller really limited our control algorithm. Perhaps an accelerometer might be useful. But definitely yaw sensors with larger sensing ranges. Acutally, about three yaw sensors each having different ranges would be nice. That way we could make the resolution / range tradeoff ourselves.

: Hello All,

: Because of the power of this forum, I would like to pose this question here.

: In the future, FIRST will upgrade it’s control system. Some things will stay the same and others will change. What I would like to know is what you think is good about the robot controllers, what needs work, or what you think should be done away with completely.

: Some things to keep in mind are to keep answers practical, and remember that FIRST is on a limited budget because it is a non-profit organization.

: I thank you in advance for your thoughts, and am looking forward to reading your ideas.

: Sincerely,
: John Cunnigham

Posted by Jeff Burch, Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Delco Electronics Systems.

Posted on 4/1/99 1:59 PM MST

In Reply to: Future Control System posted by John Cunningham on 4/1/99 11:19 AM MST:

John Cunnigham,

Thanks for asking! This question actually came up on this forum back in mid-February. Click on Archives at the top of the page, select ‘Old Forums’ then click on ‘General’ on the left and go to about the 8th thread down.

For me the three most important things are more variable space, more PWM outputs and sensor inputs, and two-way communication.

The variable space is essential! We’re forced to do all kinds of squirly things to squeak out every last bit, like changing the rx_sw varibale from a word to a nibble and shifting in only 4 bits in ReadSwitches (if we’re only using a few limit switches), or reusing variables between the relay outputs and the PWM outputs.

You can never have too many speed controllers or too many potentiometers. We’ve used all four pots these last two years and could have easily found good uses for a couple more. Likewise, there’s almost no reason to run a motor from the relay outputs (except the pump and valves). There are just too many neat things you can do with them like limiting acceleration, allowing multiple speeds, etc.

The two-way communication doesn’t necessarily mean a programmable transmitter (although that would be nice too). We could get a lot of use out of a row of say 6 LEDs on the transmitter that can be activated from the receiver. This would be useful for telling the operator when a limit switch has been hit (when you’re not using it as a hard stop) or when the optical sensor is blocked (e.g. lined up with the pole) or what gear you’re in, etc…

I like that PBasic is pretty easy for the students to learn and understand, but a more powerful language with better tools (especially debugging) would really help. All this may seem like more than we should need for a simple robot, but the robots aren’t so simple anymore. And if you compare this to the almost limitless things you can do mechanically, I don’t think it’s too much to ask.

I’m sure you’ll get a lot more responses with good ideas; thank you again for asking for our input.

Jeff Burch
Team #45