I just completed my Pixhawk equipped 4WD Slash chassis complete with dual GPSs and a 3DR 915MHZ telemetry radio.
The GPSs are mounted at each end of the chassis. The 3DR GPS/Compass module is in the front of the chassis and 3DR uBlox LEA-6 v1.1 is in the rear. Both are protected by the chassis bumpers
The rest of the components are mounted on a navigation platform above the battery.
The rover is powered by a Traxxas 3500 brushless motor and VXL-3s ESC and is using a Spektrum Remote Receiver to communicate with a Spektrum DX8 Transmitter.
I have beefed up the body mounts with extruded aluminum "L" rails to help prevent damage during a rollover.
Unlike my 2WD Slash rover, the battery can be removed for charging without taking the navigation platform off of the chassis.
Here are some pictures of the new rover:
Front View
Side View
Top View
Rear View
Regards,
TCIII ArduRover2 Developer
Replies
@Jacob,
The Pixhawk has a 32bit processor while the APM2.6 has a 8 bit processor.
The Pixhawk can support dual GPSs, dual compasses, and can run the Extended Kalman Filter (EKF) firmware that is far superior to the Defined Cosine Matrix (DCM) heading knowledge processing.
There is a price difference with the Pixhawk being more expensive than the APM.
As far as I am concerned, the EKF firmware is the only way to go for improved heading knowledge and accurate waypoint steering in a rover.
Regards,
TCIII ArduRover2 Developer
@Abe,
I originally started with two APM equipped Traxxas Slash 2WD rovers and have been slowly upgrading them.
The rover I won the Sparkfun 2013 AVC Peloton Class with has been shipped to Boulder, CO for the AVC competition. It is a Pixhawk equipped 2WD brushless Slash rover with dual GPSs.
The Pixhawk equipped 4WD brushless Slash rover is built up from parts from my second APM equipped 2WD Slash rover. The theory is that you can get better steering/cornering with the 4WD version.
Also, I am using the 4WD Slash to validate any ArduRover2 firmware changes prior to leaving for the AVC this Thursday.
Regards,
TCIII ArduRover2 Developer
Just picked up a second hand stampede 4x4. Looking at your setup Thomas, I think I'll convert one of them to the LCG slash chassis.
@dr0n3droid,
I considered using the LCG chassis, but the stock 4WD Slash chassis is already sitting lower than the stock 2WD Slash chassis and the LCG chassis is going to sit even lower.
I feel, with the extra load of the navigation platform and GPSs, you might want to stick with the stock 4WD chassis to maintain reasonable ground clearance.
I started with a 4WD Slash roller chassis for $176 USD off of eBay. The LCG version was $256 USD and I did not feel that it was worth the extra $80 at the time.
The LCG conversion kit is around ~$40 USD.
Regards,
TCIII ArduRover2 Developer
What is LCG?
Ha! thats a no brainer, now i feel stupid. Thx 4 the answer.
Awesome work. It's pretty close to what I have in mind for mine. :) Do you have any concerns with using a metal base, and interfering with the compass? Are you using the dual GPS modules as more then just failsafe? I've read some of the documentation regarding dual GPS modules, but haven't heard where it stands now. Also, wonder about the weight you've added and how the suspension will handle it. Looking to seeing you in person next weekend! :)
Aluminum should not have an appreciable effect on the magnetometer.
Aluminum damps AC electro magnetic interference, but does not significantly interfere with the earths DC field.
Steel is another matter entirely and could completely impede the magnetometer.
Aluminum actually improves things because it seriously reduces the AC EMF effect on the magnetometer from the ESCs / Motors.
I use a thick aluminum plate on my Stampede, without the plate the effect on the magnetometer from the ESC motor leads is quite pronounced, with it, it is negligible.
It does not help with the primary battery leads however which produce a DC magnetic field which strengthens when the motor is under load, so it is best to insure that the magnetometer is not too close to primary battery / power wiring. (10+ cm is preferable.)
Since the primary battery wiring tends to be in the middle of these vehicles that means that it is definitely beneficial to use remote (on GPS module) magnetometer mounted at the front or back of the vehicle (or as Tom has done - Both).
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