Let's Make Robots!

Radio Controlled Rover 5

Radio Controlled and Autonomous Navigation.

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.

Modified Rover 5

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.

Barrel Shaped Rollers

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.

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Duane, that is awesome. Killer bot to be sure!

Thanks, I've recently been working with a digital compass. I'm hoping to add the compass to the Rover 5 so it can make a large (autonomous) figure 8 in the snow. It's snow season now in Idaho. I need to hurry and get the Rover 5 working with the compass before the weather warms up.

Awesome man. I am Trying To do a similar thing with my Tank like bot and an orange RX. except with arduino.

 

Awesome man. I am Trying To do a similar thing with my Tank like bot and an orange RX. except with arduino.

 

The newer chassis's come with a different shaped wheel. This solves most of the tread problems. If you change the angle of the motors to raise the ground clearance it also reduces tension on the gearboxes and prevents them bowing. This would also help with deep snow.

The standoff idea is also good.

Thanks for the information about the updated Rover 5. Hopefully I can find a video of the new wheels in action.

I lowered the chassis thinking the added tension in the treads would assist in keeping the treads on. IIRC, the treads were more likely to stay on the wheels with the tread under tension (as long as the gearbox bow was addressed other ways) than treads under little tension.

I haven't tried these modified wheels with the robot configured for higher ground clearance. The added standoffs and bolts make changing the angles of the gearboxes more work than with an unmodified robot. I'm not sure how long it will take for my curiosity to get me to try the high clearance configuration.

Nice work Duane, photos of the wheel hubs without the flanges look stock, what method did you use to remove the flanges? I never had my Rover 5 running with the treads (second hand and previous owner had damaged three out of the four wheels) so I haven't had to contend with the treads coming off.

I think I might borrow your stand-off method for reigning in the bow-legged gearboxes.

I was pleasantly surprised at how the wheels turned out. I used a belt sander to remove the flanges. It was pretty easy. I cleaned up the edges with a Dremel drum sander but the belt sander did most of the work. I'm not sure if I would have had the guts to try removing the flanges if I hadn't had an extra set of wheels (from my Mecanum wheeled Rover 5).

I think I like the looks of the modified wheels more than the original. 

Duane, I followed the link to your parallax forum thread and in reading through post #6 swa you too have a mechanum wheel Rover 5. Video footage of it in action looks amazing and has me questioning if I have my wheels on the wrong way round. I've still to implement encoders on my robot and think this may go a long way to balancing the individual speeds of each of the wheels.

I plan to make a separate post about my Mecanum wheeled Rover 5. Right now my two Rover 5 robots share their electronics with each other. I have to undo a few wires to move the controller and batteries from one chassis to the other. I also have to reprogram the QuickStart board with the appropriate code when making the switch.

A QuickStart board is $25 and the motor control boards were under $4 each. It isn't very expensive to give each robot its own brain.

I'm in the process of cleaning up the code on both Rover 5 robots and I plan to post it within the next few days. I found the feedback from the encoders is really important for controlling the Mecanum wheeled robot.

I really like the Vex Mecanum wheels. The FingerTech Mecanum wheels are easier to mount to the Rover 5 but the Vex Mecanum wheels are so much nicer (IMO) than the FingerTech wheels (I have a set of both). I'll give more information about using the Vex Mecanum wheels when I make a LMR page for my Mecanum wheel Rover 5.