Hi All,

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

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Replies to This Discussion

Hi Thomas,

Looks really good! I like the nice and clean build! Will you mount sonars in the future? Btw, do you know some less expensive alternatives to the MB1240 sonars?

Best regards,

Thorsten

PS: what is the wheelbase of the Slash?

@Thorsten,

I wish the MB1240s were cheaper or that there were other alterative sonars with the same range and quality, but I have yet to see a cheaper price than the ones at Jameco Electronics and the alternatives just do not have the quality build and the range.

However, that being said, unless you plan to go at low speeds, like around less than 3m/s, the sonars are not going to help you avoid obstacles at speeds greater than 4m/s as the reaction/processing time is to long to avoid an obstacle when going at the higher speeds.

You might want to consider a LIDAR-Lite which has a range of at least 13m. I have one on order and will be testing it this summer. However it has a narrow beam and must be swept in azimuth in front of the vehicle's path to reasonably see obstacles to the right and left of the vehicle center line.

Running a mission on a course like the AVC, I would rather rely on highly accurate GPS heading knowledge, accurate steering, and as accurate as possible obstacle (barrels, hoops, ramps) lat and long positions.

The new uBlox M8 and the Navspark GPSs have been found to be able to acquire 15 - 20 satellites and the Extended Kalman Filter in the rover Pixhawk firmware can produce exceptionally accurate turns and waypoint to waypoint headings.

I believe that this is the future of highly accurate waypoint missions.

Here are the details on the chassis: Specs

Regards,

TCIII ArduRover2 Developer 

Love the dual GPS. Can't wait to see how LIDAR-Lite works on that. 

Looking forward to seeing it run next week!

@Chris,

Unfortunately this 4WD version of the Slash will have to wait until the 2015 AVC.

I will be running my 2WD Slash which has the same navigation system and dual GPSs.

The thinking concerning the 4WD version is that it can get through the turns at somewhat higher speed than the 2WD version.

Regards,

TCIII ArduRover2 Developer

Hi All,

I will be glad to duplicate my Pixhawk equipped 4WD Slash chassis for any interested party.

The total cost will be the actual cost of all parts, shipping, and a reasonable labor change that can be negotiated.

I am also open to converting new Traxxas 4WD chassis for autonomous use.

Regards,

TCIII ArduRover2 Developer

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! :)

@JesseJay,

Thanks for the kudos, much appreciated.

Based on my experience with my Pixhawk equipped 2WD Slash, the metal in the chassis has not been an issue and I use aluminum plate and stainless steel and brass hardware for component mounting. Also, we can do an initial compass offset and then turn the compass learning function on to further refine the offsets.

Right now the dual GPS setup is more for redundancy as at least one GPS will maintain a lock when the other GPS has momentarily lost a lock. The navigation firmware is programmed to use the GPS with the most satellites at any given moment. In the future we are considering some form of averaging.

I am able to get 6 - 8 runs around my simulated AVC course (~1/8 mile) on a 5000mahr battery at speeds up to 9m/s so the additional weight has not been a concern at this time.

Regards,

TCIII ArduRover2 Developer

Wow! The slash has so much room under the hood. My stampede 4x4 chassis is tiny in comparison.
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.

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).

@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

That does look great! What's the intent,of making this bad boy?

That is such a clean build...most impressive.

Beautiful work.

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