Radio Controlled Rover 5
I've been working with a couple Rover 5 chassis lately and I thought I'd share my experience with my treaded Rover 5.
I think the biggest problem people have with threaded robots is keeping the treads from coming off.
I've tried several methods of keeping the treads of my Rover 5 in place. One thing I found to be very helpful was to use standoffs to pull the "bowed" gearboxes back into alignment.
Another trick I've learned to keeping the treads from coming off is to remove the rims from the rollers. It seems counter intuitive that removing the rims would help keep the treads on but I learned this while trying the opposite, extending the rims. I make a set of donut shaped rim extenders out of expanded PVC. These disks increased the diameter of the rims by 10mm. I was very disappointed at how poorly these rim extenders worked. When I posted a video of this failed attempt on the Parallax Robotics forum, erco pointed out that many belt drive systems use barrel shaped rollers in order to keep the belts from coming off.
Since I had a second set of Rover 5 rollers, I decided to try the barrel shaped idea. I was amazed at how well they work. I can still lose a tread once and a while but these tread problems are much less frequent than they used to be. If I notice a tread starting to come off, I can usually coax it back in place by driving the Rover 5 straight.
This robot uses a Parallax QuickStart board ($25) as its main control board. The Propeller chip reads the four quadrature encoder lines and adjusts the PWM output of each motor based on the target speed and the actual speed computed from the encoder feedback.
The motor controllers are a pair of inexpensive L298N PCBs I purchased off ebay (for about $3 each).
I think the Rover 5 is a good robot to demonstrate the advantages the Propeller microcontroller bring to robotics. Being able to devote an entire processor (cog) to monitoring the quadrature encoders greatly simplifies the code needed to control the Rover 5.
The landing gear switch on the RC transmitter allows the robot to be either controlled remotely or to operate "autonomously". Presently the only autonomous activity the robot does is drive in a figure 8. (Having a robot drive in an autonomous figure 8 is easier said than done.) Check out the video of the figure 8 (I've gotten the robot to behave better since recording the figure 8).
There's also a video (sorry about the bad audio) showing the robot driving in the snow. Kind of fun but I think it's clear from the video if there had been more snow, the Rover 5 would probably have had trouble getting around.
I plan to add some sensors to this robot to allow it to autonomously navigate. I thought it would be a good idea to share these mods since it seems like a lot of people have trouble with the treads of the Rover 5.