Hi all,
I started building a rover based on a 1/5th scale truck. Since most rovers discussed here are 1/8 or 1/10 trucks/crawlers I am wondering if you can provide any thoughts, ideas or recommendations about bigger rovers?
The rover is a 4WD truck with the motor placed in the middle. I’ll place the Pixhawk in the front and already moved the ESC (originally sitting in front of the motor) behind the motor to reduce interference. I am planning to use the power module for powering the Pixhawk.
I have two specific questions:
- Where to place the power module? I.e., should I use a longer DF13 cable from the back of the rover to connect to the Pixhawk in the front or should I use a longer power cable and pace the power module closer to the Pixhawk? The wheelbase is 57cm.
- Can the high torque 6V steering servo be powered from the Pixhawk or should I use the output of the ESC as a direct input to the servo (does this work at all?) and then only connect the signal and the ground to the Pixhawk (for both the ESC and the servo)?
Thanks a lot in advance!
Thorsten
Replies
Hi all,
this is a screenshot of the first successful auto missions:
There seems to be a GPS glitch at the end of a mission and I am also still fighting some shutdowns which occur mostly at very low speeds. I will post some logs the next days.
Kind regards,
Thorsten
@Thorsten,
Nice work!
Yes, provide either tlogs and/or data flash logs for us to help you analyze your issues.
Regards,
TCIII ArduRover2 Developers
@Thomas,
thanks! Yes I will! I had a look at different logs but I could not find anything obvious. So I will prepare a video along with a log file.
The main problem I have is that the behavior of the rover is not consistent: Sometimes it is running fine as it should and sometimes it stutters and doesn't want to start at all when Auto Mode is engaged. When playing around with CAM_TRIGG_DIST and the Start/Stop Switch it sometimes it proceeds normally, sometimes stutters or proceeds with a wheely.
Stuttering also occurs in manual mode. What parameters might influence this behavior (I am using EKF)?
The 4S battery should be fine but maybe I should use 6!?
Thanks in advance and kind regards,
Thorsten
@Thorsten,
The Auto Mode vehicle speed is controlled by the Cruise_Speed parameter and the Cruise_Throttle parameter.
The Cruise_Speed is the velocity you want the rover to move at on a mission.
The Cruise_Throttle is the percentage of forward throttle necessary for the rover to attain the Cruise_Speed velocity.
On my Slash Rover it takes around 30 - 35% Cruise_Throttle to reach about 6m/s. Velocities from 6 - 9m/s can take between 40 - 50% Cruise_Throttle.
Heavier chassis like yours might reqire 40 - 50% Cruise_Throttle just to get moving.
From your description of its behavior, the rover's ESC might be having an issue with determining the APM throttle neutral point (1500us) at power up.
I assume that you have calibrated the rover ESC to the R/C transmitter throttle through the APM when in the Manual Mode?
Regards,
TCIII ArduRover2 Developer
@Thomas,
Yes, indeed I am having some "problems" with the ESC calibration. I tried to calibrate it several times but the behavior is different to what is described in the (copter) wiki. What is missing is the "two additional beeps to indicate that the maximum throttle has been captured." I just tried it again for several times.
However, after pulling the transmitter’s throttle stick down to its minimum position the ESCs emits some melody (the wiki says long tone) - I assume that this is indicating that the minimum throttle has been captured!?
You are right: I played with Cruise_Throttle and ended up at 50%. For now I let it drive at low Cruise_Speeds of 2-3m/s.
I'll make some tests tomorrow...
Thanks and kind regards,
Thorsten
@Thorsten,
I always use the ESC manufacturer's calibration scheme and not the one in the (copter) wiki or elsewhere.
Since I use Traxxas products, they use the ESC leds to indicate when the high and low throttle positions have been recorded by the ESC.
Regards,
TCIII ArduRover2 Developer
Hi all,
I finally installed my new telemetry and two sonars following Thomas' guide. The CLI Sonartest looked perfect. However, I am not sure if my LV‑MaxSonar‑EZ1 will work for this purpose. Anyway, I am ready for tuning...
Regards,
Thorsten
Hi all,
attached some more pictures. Telemetry, however, is still missing...
Regards,
Thorsten
@Thorsten,
You have a nice looking configuration so far.
However, rovers can rollover when they hit curbs or other obstacles at higher speeds.
You might want to consider putting your navigation platform lower on the chassis or provide some kind of roll cage above the platform.
Regards,
TCIII Ardurover2 Developer
@Thomas,
good point! I will put some roll cage on it at some point (when I decided what I really want to do with it :-) ). So far even with speeds higher than I am planning for Auto missions it was rock-solid. It is pretty heavy...
Kind regards,
Thorsten
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