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Rover Vehicle with Autopilot


WT sideThis view shows the main power switch just above the middle wheel. To the right is the battery pack consisting of six LiPo cells stacked to provide 7.4 volts and about 8.5 amps. The white box above the power switch mounted with aluminum angle bracket houses a Ardupilot made by 3D Robotics. Notice the square GPS antenna on the top of the box. Also, the black telemetry antenna of the left under the camera mount. The Ardupilot provide waypoint following, heading, Lat-Long, and three modes. It sits enlign with the signals from the Spektrum RC controller seen in the background. There are 8 channels, but only two are needed to drive the vehicle (elevator for forward/back speed and aileron for left/right direction). It's difficult to see, but between the Ardupilot box and the battery pack is the A8000 receiver for the RC controller.

WT Rear ViewThis picture shows the back of the vehicle and the video transmitter hardware. There is a clover leaf antenna, 12V LiPo battery, and power switch. The transmitter is under the metal body plate. You can see a black cable going up toward the camera mount. That carries 12V to and video, and audio signals from the camera.

I used the throttle channel to move the camera up and down and the rudder channel to move the camera left and right. When the camera is down, it can see what the claw in the front is grabbing. The claw is opened and closed using the Aux3 channel. So there's one more channel left. I intend to use it to lift the claw and maybe pull it back onto the vehicle with a cam action.

WT cameraThe camera is a Sony 650 lines of NTSC video and audio. The mount has two small servo motors to provide the two degrees of freedom. This performance is best seen in the associated YouTube video of driving the vehicle remotely using the camera view to steer.

The telemetry is on 933MHz and the video is on 5.4GHz. The RC controller is on 2.4GHz so the transmitters don't show any sign of interference.

Each wheel has its own motor. The motor is 75:1 gear ratio, 6Volt DC motor. The motors and main computer are on one PCB board mounted under the deck plate under the Ardupilot box. This board has a Arduino ATMEGA168 processor and two heavy duty H-switches for the motor direction. Three motors on a side are connected in parallel, so the direction is controlled like a tank with each side's speed adjusted to turn, go forware, or backward. It can spin on a dime if full aileron is commanded. The suspension is loosely coupled from side-to-side connecting two motor together. If the vehicle leaves the ground, a small cable is tided between motor pairs to limit the wheels folding under the vehicle. This sloppy suspension allows the vehicle a fluid sort of drive that easily goes over objects. It will try to climb a wall, especially if one side hits a wall. The wheels on that side go right up the wall so maximum tracksion is realized. The knobby tires actually grip too tightly if on a shag carpet and stall the motors. If a stall occurs, the battery current and voltage have threshold limits. If it lasts three polling intervals of the software, the software is shutdown. At that point, you have to rescue the vehicle and recycle the power switch.

If you outside and power up, the GPS takes about two minutes to lock on. You should wait for the. The Mission Planning software running on a laptop will link with the telemetry channel and you can see GPS lock-on. The position is displayed on a Google Map. I open the video channel at that point and overlay it on the Google Map. Using the RC Controller from just about anywhere you can see where you are going through the camera eye. It drives like a dream with the higher gear ration motors. There is a version of Wild Thumper with 34:1 gear and that screams. I didn't want to flip this vehicle with all the antennas to munch. This was a challenging project and is really never complete because this vehicle can support just about anything you want to do remotely on the ground. I have to set waypoints next and let it drive its self around an open field. You can drive it manually to a point, change the mode and set that location as a waypoint, and then do the same around the course. Then you can start over in an automatic navigation mode. All great fun.


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