Have always been into models and have copious cars to use and a delta wing glider. I don't want to spend $270 on all the Ardupilot kit then $89 on the EZ then more on the RC control gear to have my first flights royal screwed due to my inexperience with flyers (I'm pretty bad :D).
I have been building guitar pedals since I was 8 and was programming when I was 7 with my father, I am 28 this Sunday so am fairly confident I can give this a good fiddle once I have a definite direction. My hope is to turn my first RC car (a Blitzer Beetle) into a Ardupilot testbed. Having read through the other posts, it seems that some counter measures on breakout boards would be wise.
My basic purchase will be the Ardupilot, GPS reciever (faster the better probably - LS20031), FTDI cable and LiPo.
I just want it to go roaming around a car park which i will plan out with GPS co-ords. It will be fully autonomous (throttle and steering) and with perfect reception wouldn't need object detection but just in case I am thinking I should add an emergency stop. I'm not looking for object detection and avoidance just an "Arrrrgh!!" stop routine.
I would want to drive round the car park 20% throttle until I've got the waypoint navigation sorted then up the throttle in 10% increases, tweaking the code as I go. Object detection may be wise to sort with another board so only a distress signal is "seen". IR and/or ultrasonics seem the obvious sensors but having never done any UAV/UGV tinkering before I'd really like some more experienced input. I will also be moving on to UAV from the UGV but that wont be for a while so my shopping list is geared to be dual purpose.
What would you recommend?
If everything is simple enough a shopping list would be nice :)
If it will be a few nights of swearing any other help would be nicer :D
Thank you
Replies
A rover version of the Ardupilot is not as simple as it seems.
Airplanes tend to fly in straight lines from one way point another, but a rover may not be able to do this depending on obstacles that are in the way of a straight line course.
Therefore, as you have observed, it might be best to build a main processor board that is responsible for obstacle avoidance on the way between waypoints. The main processor would receive steering information from the Ardupilot in the form of a "rudder" servo signal which it would decode. It would then use the steering information along with a magnetometer input to determine a straight line course to the next waypoint. However, if the rover came upon an obstacle, it would determine the best way to steer around the obstacle and then resume the straight line course to the next waypoint.
Example: Let's say that the course is a large rectangle bordered by streets. The first waypoint is on the opposite side of the course from the home starting point. The easiest path would be a straight line from the home starting point to the first way point on the other side of the course. Unfortumately there is a three foot brick wall on all sides of the rectangle. Now what do you do. Well, the main processor would detect the wall infront of it and then look right and left for a clear path which it would find. However, the Ardupilot is telling it to go straight which it cannot do. So side looking sonar would keep it a discreet distance from the wall as it moved along the wall all the time trying to make a right turn to go straight to the next waypoint on the other side of the rectangle.
I have built a main processor using a Parallax BS2p to provide foward and side looking sonar for obstacle avoidance. The Arduipilot, programmed with waypoints provides steering input to the next way point. The main processor will always try to go in a straight line to the next waypoint while avoiding all obstacles in its path. The waypoint on the opposite side of the course from the starting waypoint will require the rover to follow a "U" shaped path to the opposite side of the course as there is no way that it is ever going to break through the three foot high brick wall around the edge of the course to follow a straight line.
Hope this helps.
Regards,
TCIII