View Full Version : RC-PWM measure routine for WRV1 Luna Rover required
04-06-2009, 03:47 AM
It is quite a while, when I posted the last time in this forum. After changing my job, I did some development on WRV1 (wiki.xprize.frednet.org/index.php/Portal:WRV1 (http://wiki.xprize.frednet.org/index.php/Portal:WRV1)) one oft the rovers of TeamFrednet (www.teamfrednet.org (http://www.teamfrednet.org)).
Now the hardware has reached the point, where I will control the rover via a simple RC control unit. Since I have planned to use Propeller chips to control the vehicle, I would like to start with a simple task: I need to measure the RC pulses for two channels and my question is: Has anybody written such a routine? For the first step I need a simple routine giving three levels -1 , 0 , +1 representating 1.2ms, 1.5ms, 1.8ms. This way I can control forward, stop, reverse and moving the steering unit left, stop, right.
If anybody has such a module I would be lucky to have knowledge of.
AND If anybody would like to participate on this project; just feel free to write an email to joerg(dot)schnyder(at)TeamFREDNET(dot)org (or post in the TeamFREDNET forum forum.xprize.frednet.com/viewtopic.php?t=345 (http://forum.xprize.frednet.com/viewtopic.php?t=345))
04-06-2009, 04:45 AM
You may want to check out the object posted here:
I have used this with good results on one of my projects. I think it will provide the basis of what you need. This object returns the pulse widths in microseconds.
04-06-2009, 04:50 AM
there are two objects suitable for thhis in the obex (http://obex.parallax.com/objects/)
Servo Pulse Input (http://obex.parallax.com/objects/331/)
Simple Radio Control Capture & Repeat to Servo (http://obex.parallax.com/objects/401/)
04-06-2009, 03:26 PM
I will report as soon as possible about the success!
There are some videos of the project (see above) and when the remote control is working, I will do some more. I have also an request of a German TV station for doing so.
04-06-2009, 03:48 PM
The spring-suspension is very interesting.
I took a look at the videos. There are so many
I don't like to go through all of them.
Which one is the one that shows how the rover is driving around climbing over things and shows how the spring-suspension works ?
04-06-2009, 10:28 PM
A video showing the wheels in action does not exist at the moment, but as soon as the rover has gotten his final motors and the control unit. I will shoot one.
04-08-2009, 06:29 PM
Here the block diagram of the WRV1 rover: (just if somebody is interested)
04-08-2009, 10:05 PM
This is quite a project ! Looking at the Concept diagram, I was wondering if the power feeds were controlled by the main control systems or are they directly plugged into the F/R buses? Plus, are the two transceivers for redundancy?
How does one determine position on the moon? Does inertial nav work at such low speeds? Do you count steps?
04-08-2009, 11:00 PM
The power system is a bus system where you can connect sources in parallel (hot plug possible!). My system does not need any main controller, it is based on the fact, that sources with a defined output impedance. I have developed a 30V DCBUS and it works at my home. A 400V power version is designed and for WRV1 I will use a 10V version. An AC/DC version is running and I am doing the design for a photo voltaic source right now. If you interested I can send you more information about the DCBUS systems.
The two tranceivers are for redundancy as you noted. The whole concept is based on the idea to have the two modules independent so the mission could be finished with half of the rover working.
The navigation is not well defined at the moment. I think the most important thing is to create a reliable vehicle with a very low weight and the lowest power consumption possible. So the speed will be low (about 2m (6ft) per minute). The mockup runs actually five times too fast!
04-16-2009, 09:37 PM
OK, some work is done!
The software is running now. The servo pulses are detected by a modified ServoInput routine (my old R/C unit does not pause between the servo pulses), the main program acts two relays for the motors and my universal stepper routine drives the stepper motor in the desired direction. The hardware is based on MoCo-B my motion controller board and a stepper motor driver PCB as well as a experimental PCB for the relays and some driver stuff.
Loo at the hardware here:
04-23-2009, 03:15 AM
WRV1 was running the first time controlled by a Propeller Chip today.
see: www.youtube.com/watch?v=wmA8ghL6BAs&feature=channel_page (http://www.youtube.com/watch?v=wmA8ghL6BAs&feature=channel_page)
04-23-2009, 09:02 AM
Looks good Jörg!
What is that sound when the steering goes to full excursion (left, maybe right as well)?
04-23-2009, 12:54 PM
Since I decided to use stepper motors, the steering unit sounds a little bit strange and if it reaches the final position you hear the typical sound of missteps. That is normal and does not any harm. The unit sounds also strange because the two motors are not aligned perfectly and I use fullstep single phase mode for driving the motors. My Propeller stepper module can do three modes fullstep single phase, fullstep dual phase and halfstep modes. It can run continuously controlled by a start/stop bit or controlled by a position count so you can only change the target position number and the Spin module does the rest! For multi axis applications you even can do a synchronous start of all axis, so you can prepare the move first and then let act the motors together. When I have tested all of the functions, I will put the module in the library!
One more point to mention; the steering unit moves too fast, so maybe it misses sometimes some steps, but I wanted to see how it behaves!