PBP projects for R/C models

[Kenjones1935]

The WEB says that a standard hockey rink is 200' by 85' with curved corners on a 10' radius. Here in Fitchburg we have both indoor ice hockey rinks and outdoor street hockey rinks where the players use roller blade skates. The rinks are bounded by an approximately 4' high solid wooden wall.

The advantage here is speed is possible; 25mph +- for electric cars well over that for nitro powered gas engined cars.

I just found a WEB site extolling the 2D IR proximity sensor. Two potential problems - outdoors in bright sunlight and multiple cars. What do you think?

I did not read the specs for IR sensing. They are talking inches to a few feet. I need at least ten feet, probably more.

http://www.societyofrobots.com/senso...pirrange.shtml

Ken

[Kenjones1935]

I think my little car needs to know where it is relative to the wall it is trying to follow and what maneuver it is presently trying. Right now the code has three states:
1. Trying to go straight along the wall.
2. Trying to turn left sharply because something is in front, but not close enough for state #3.
3. Trying to brake and backup and turn to the left enough so it can return to #1 above.
There is a forth unofficial state in which it is completely lost. It usually gets there from state #2 by turning too successfully. It thinks it is in state #1 but is too far from the wall. If the room is too big it just keeps turning right making a big circle.

It has problems in each case.
In #1 it swerves rather than going straight. If it knew better its rate and angle of approach it could better decide how hard to make its corrective turn.
In #2 if it turns too hard and too successfully it becomes lost. If it does not turn hard enough it finds itself in state #3.
#3 works pretty well except when the front of the car is touching the wall. Something strange sometimes happens then. It just stops. I am not sure why.

My model level car has a POT with which I tell the PIC how fast to go. The top POT position is no where near top speed for this particular model. Associated with each of the seven POT positions are three distances: The ideal distance from the wall. The distance at which the car must enter state #2. The distance at which the car must go to state #3.

I have SONARs, PICBASIC PRO, and 16F887 to work with. Can my cars race inside a hockey rink?

Ken

[ScaleRobotics]

I just found a WEB site extolling the 2D IR proximity sensor. Two potential problems - outdoors in bright sunlight and multiple cars. What do you think?

I did not read the specs for IR sensing. They are talking inches to a few feet. I need at least ten feet, probably more.

http://www.societyofrobots.com/senso...pirrange.shtml

Ken

Yeah, that was discussed back on post # 617 of this thread. http://www.picbasic.co.uk/forum/show...6363#post96363

I thought the object was to be within two feet of the wall, but maybe that changed? I was thinking if you are more than two feet from the wall, turn right. So I am not sure that you really need more than 30 inches of sensing for the side view. Front view, yes, you need more like 15 - 20 feet. Using one sonar and one IR, at least you would be able to take both measurements at the same time, giving you twice the data in the same amount of time.

I would think multiple cars with IR sensors would be a lot happier than multiple cars with sonar. The IR is a spot, where as the sonar is pretty much all over the map with echos etc. As for sunlight, this website says "This ranging method is almost immune to interference from ambient light, and offers amazing indifference to the color of the object being detected. In other words, the sensor is capable of detecting a black wall in full sunlight with almost zero noise." But then they go to say "(UPDATE: despite popular belief, it is quite possible for both direct and indirect sunlight to significantly affect results. I learned this the hard way!) " Sounds like some testing is required!


I had another thought about the importance of a wheel speed sensor. If you are measuring vehicle speed with a wheel sensor, you can differentiate the speed that your sonar is picking up to see if the wall is moving toward you at a faster or slower rate than your vehicle is moving. This will tell you if the wall is turning toward you (curved surface), or if you are turning toward a straight wall. This would be helpful for a lot of things. I would say required for better control

I have SONARs, PICBASIC PRO, and 16F887 to work with. Can my cars race inside a hockey rink?

As long as they get enough traction, and don't get checked by any of the hockey players.

[Kenjones1935]

Yes, two feet from the wall is fine when the car is moving at walking speed. At 20mph or more as would be appropriate in a hockey rink I think the car needs more maneuvering room.

The model level cars have rubber tires that can be studded. Since 'indoor' hockey rinks have good enough ventilation to run the Zamboni ice scrapping machine it might be possible to race gas (nitro) driven models in them.

The issue seems to be speed of sensing and accuracy of sensing and using PBP to do the math. I have no idea how to attach a speed measuring device to the wheels of a model car.

Ken