Chief Delphi - Kevin Watson's Kick-off Demo Code!

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Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by SlimBoJones

Kevin's done a great job again this year! The IR and encoder code he supplied last year was outstanding, and I had a chance to quickly flip through his code providing gyro, PID, and navigation scripting. See http://kevin.org/frc/ the first link.

This year is going to be a LOT of fun! Thanks Kevin!

Thanks, but a lot of credit goes to Rich Petras who wrote the PID and scripting code. Rich is on the MER navigation software team and is one of the original MER "drivers".

Quote:

Originally Posted by SlimBoJones

1) I think you'll need to source two encoders (not in the kit) to work with this code. The gear tooth sensors included in the kit may not cut it, unless you buy two more, and are clever about aligning them to simulate a quadrature output.

You don't really need more than one per wheel. You can garner your rotational information from the motors commanded direction.

Quote:

Originally Posted by SlimBoJones

2) There is no camera code in here. So for teams looking to use the some combination of camera navigation, navigation scripting, and position sensing via encoders and gyro, you'll need to fuse the two together. So don't get too excited about things being TOO easy.

This is an understatement <grin>.

Quote:

Originally Posted by SlimBoJones

3) Will the included gyro code work with the accelerometer provided in the kit? Plug and play I hope?

The idea is the same: Sample the heck out of the analog signal and downsample (average), but fundamentally they are very different sensors.

Quote:

Originally Posted by SlimBoJones

I didn't pick up on what kind of gyro Kevin Watson used for the demo robot.

We used a Silicon Sensing Systems gyro because we had two of 'em on hand for Rich and I to both be able to work with. We weren't too happy to see as much drift as we saw, so I'd suggest using the ADXRS150EB or ADXRS300EB, which I've had pretty good luck with.

-Kevin

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Kevin Watson

We weren't too happy to see as much drift as we saw...

Are you referring to the way the 'bot would twitch periodically as Dave was talking during kickoff? I wasn't sure whether that was intended or not.

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by gwross

Are you referring to the way the 'bot would twitch periodically as Dave was talking during kickoff? I wasn't sure whether that was intended or not.

Yes, exactly. So that Dave could show that the 'bot was actively servoing, Rich setup the code to servo using the encoders and gyro for a few minutes after Dave hit the start button and the 'bot did its routine. The gyros during that time were drifting and causing the 'bot to think that it had moved away from its intended heading. This happens with all gyros to one degree or another and is just something that has to be dealt with. I'm working to tune the gyro code to minimize this effect, yet stay pretty efficient.

-Kevin

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Kevin Watson

Kevin, have you thought about trying wheel odometry to derive heading? I found this site last summer, and I have been so busy and not active with any robotics that I have not had a chance to see if it actually works.
Scroll down to the navigating section
http://www.geology.smu.edu/~dpa-www/robo/nbot/

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Ryan Cumings

Yes, you can use differential wheel odometry to derive heading, but its a headache because just a little bit of wheel slip will throw your heading off (and the error integrates too).

-Kevin

Re: Kevin Watson's Kick-off Demo Code!

Just out of curiosity,

One of our big mentors is an aviation company. They have a bunch of parts from autopilot systems sitting around. Do you think it is worth trying to make this stuff work, or should we just shell out a couple of hundred for something which works.

Also, has anyone taken a look at RC helicopter gyros? I was searching and found some on a hobby shop site, the even had PWM cables attached. Thoughts?

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by CJO

Also, has anyone taken a look at RC helicopter gyros? I was searching and found some on a hobby shop site, the even had PWM cables attached. Thoughts?

The gyros used in helicopters are integrated PID controllers. It takes an input from the receiver as the set point, compares it to the internal sensor value, and outputs the PWM signal required to match the rates. There are potentiometers to adjust the gain. As such, they aren't suitable for integrating the heading because you don't have access to the raw sensor output. I don't think they are high precision parts but I don't know for sure.

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Kevin Watson

Sorry, I haven't been around much. The hillside directly behind my house collapsed last Sunday and I've been dealing with the mess.

Anyway, the two variables are GYRO_RATE_SCALE_FACTOR and GYRO_ANGLE_SCALE_FACTOR. GYRO_RATE_SCALE_FACTOR should be set to a value equal to the gyros sensitivity in units of angular rate per volt divided by the ADCs bits per volt. Set GYRO_ANGLE_SCALE_FACTOR to GYRO_RATE_SCALE_FACTOR divided by the update rate, which is 50Hz.

So, for example, to use the Analog Devices' ADXRS150 evaluation board, which has a sensitivity of 12.5mV/degree/sec, take the inverse of that sensitivity (80 degrees/sec/volt) and divide by the number of ADC bits per volt (1024/5), which equals (80 x 5)/1024 = 400/1024 = 100/256. The GYRO_ANGLE_SCALE_FACTOR is then just (100/256)/50 = 2/256 = 1/128.

In the coming days I'll be working on cleaning up not only my house, but the code too <grin>.

-Kevin

Thanks a lot Kevin!

Sorry to hear about your home :(

My team didn't receive the Kit yet but we decided now that we're going to use a testing plataform and last year's kit so that we can start our programming tests.

And since we programers were just helping out with other stuff we decided to do a very simple GUI for your code, We'll be finishing it today and I'll post here.

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Squall

Sorry to hear about your home :(

Thanks.

Quote:

Originally Posted by Squall

And since we programers were just helping out with other stuff we decided to do a very simple GUI for your code, We'll be finishing it today and I'll post here.

I assume this is for the gyro code? If so, the conversions I gave you were in units of degrees, which is too course to use. Rich Petras wanted milliradians (pi radians = 180 degrees), so that's what the new gyro code will return. I've also built in the option of returning tenths of a degree by uncommenting some #defines in gyro.h:

Code:



/*******************************************************************************

*

* TITLE  gyro.h 

*

* VERSION: 0.2 (Beta)                                                   

*

* DATE:  12-Jan-2005

*

* AUTHOR:  R. Kevin Watson

*        kevinw@jpl.nasa.gov

*

* COMMENTS:

*

********************************************************************************

*

* CHANGE LOG:

*

* DATE                 REV  DESCRIPTION

* -----------  ---  ----------------------------------------------------------

* 21-Nov-2004  0.1  RKW - Original

* 12-Jan-2005  0.2  RKW - Altered Get_Gyro_Rate() and Get_Gyro_Angle() to use

*                                   long integers for internal calculations, allowing larger

*                                   numerators and denominators in the GYRO_RATE_SCALE_FACTOR

*                                   and GYRO_ANGLE_SCALE_FACTOR #defines.

* 12-Jan-2005  0.2  RKW - GYRO_RATE_SCALE_FACTOR and GYRO_ANGLE_SCALE_FACTOR

*                                   #defines added for Analog Devices' ADXRS401, ADXRS150 and

*                                   ADXRS300 gyros.

*

*******************************************************************************/

 

#ifndef _gyro_h

#define _gyro_h

#define TRUE 1

#define FALSE 0

// MILLIRADIANS_PER_TENTH_DEGREE = 349/200

// ADC_BITS_PER_VOLT = 1024/5

// GYRO_RATE_SCALE_FACTOR = ANGULAR_RATE_PER_VOLT / ADC_BITS_PER_VOLT

// GYRO_ANGLE_SCALE_FACTOR = GYRO_RATE_SCALE_FACTOR / SAMPLE_RATE

// default parameters for Silicon Sensing Systems' CRS03

// sensitivity = 20mV/deg/sec

// #define GYRO_RATE_SCALE_FACTOR 625/256 // defaults to 625/256 for tenths of a degree/sec

// #define GYRO_ANGLE_SCALE_FACTOR 25/512 // defaults to 25/512 for tenths of a degree

// #define GYRO_RATE_SCALE_FACTOR 8725/2048 // defaults to 8725/2048 for milliradians/sec

// #define GYRO_ANGLE_SCALE_FACTOR 349/4096 // defaults to 349/4096 for milliradians

// default parameters for Analog Devices' ADXRS401

// sensitivity = 15mV/deg/sec

// #define GYRO_RATE_SCALE_FACTOR 1665/512 // defaults to 1665/512 for tenths of a degree/sec

// #define GYRO_ANGLE_SCALE_FACTOR 333/5120 // defaults to 333/5120 for tenths of a degree

// #define GYRO_RATE_SCALE_FACTOR 5811/1024 // defaults to 5811/1024 for milliradians/sec

// #define GYRO_ANGLE_SCALE_FACTOR 581/5120 // defaults to 581/5120 for milliradians

// default parameters for Analog Devices' ADXRS150

// sensitivity = 12.5mV/deg/sec

// #define GYRO_RATE_SCALE_FACTOR 125/32 // defaults to 125/32 for tenths of a degree/sec

// #define GYRO_ANGLE_SCALE_FACTOR 5/64  // defaults to 5/64 for tenths of a degree

#define GYRO_RATE_SCALE_FACTOR 1745/256  // defaults to 1745/256 for milliradians/sec

#define GYRO_ANGLE_SCALE_FACTOR 349/2560 // defaults to 349/2560 for milliradians

// default parameters for Analog Devices' ADXRS300

// sensitivity = 5.0mV/deg/sec

// #define GYRO_RATE_SCALE_FACTOR 625/64 // defaults to 625/64 for tenths of a degree/sec

// #define GYRO_ANGLE_SCALE_FACTOR 25/128 // defaults to 25/128 for tenths of a degree

// #define GYRO_RATE_SCALE_FACTOR 8725/512 // defaults to 8725/512 for milliradians/sec

// #define GYRO_ANGLE_SCALE_FACTOR 349/1024 // defaults to 349/1024 for milliradians



void Initialize_Gyro(void);  // initializes and starts the gyro software

int Get_Gyro_Rate(void);  // returns the current heading angular rate of change

int Get_Gyro_Angle(void);  // returns the current heading angle

void Calc_Gyro_Bias(void);  // calculates the current gyro bias

int Get_Gyro_Bias(void);  // returns the current calculated gyro bias

void Set_Gyro_Bias(int);  // manually sets the gyro bias

void Reset_Gyro_Angle(void); // resets the heading angle to zero

void Disable_Gyro(void);  // disables the gyro

void Initialize_Timer_2(void); // initializes and starts timer2

void Timer_2_Int_Handler(void); // interrupt service routine for timer2

#endif

-Kevin

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Kevin Watson

I assume this is for the gyro code?

It's not just for the gyro, it's kind of a general tool

What it does is just that we've selected some 'defines' that we have seen in your code that we think that should be something that not just us but all the teams are gonna have to change a lot during tests, and also at the competition, so our tool just grab those defines as put it on text boxes so that you can easy alter it without having to go trough all the code and find the right place.

Then you must use MpLab to compile the code.

We're translating this tool to English and comenting the code.

We're kind of late because we were having trouble with the Wireless serial device that you've mentioned in your site, we can make it work but only at 9600bps so we can't program our robot using Ifi Loader, can you give us some direction here ?

Thanks a lot

Re: Kevin Watson's Kick-off Demo Code!

Quote:

Originally Posted by Squall

We're kind of late because we were having trouble with the Wireless serial device that you've mentioned in your site, we can make it work but only at 9600bps so we can't program our robot using Ifi Loader, can you give us some direction here ?

The SMiRF wireless transceivers will only go as high as 38,400 baud, so they cannot be used to program the RC. They are, however, great for sending debugging telemetry back to your computer without a long serial cable.

-Kevin

Re: Kevin Watson's Kick-off Demo Code!

I've updated the PID/Scripting code to include the latest gyro code, additional documentation and data sheets for compatible encoders and gyros. It can be found here: http://kevin.org/frc.

-Kevin