Here in Germany we are supposed to stay at home (this will probably turn into a curfew soon), so I decided to build a new rover. It is just the chassis with RC control for now:
The body is a Hammond aluminium case, the rover is upside down in the pictures. It is driven by two Planet Hobby 510kV brushless outrunners powered by two 4000mAh 2S lipos in parallel. The wheels are 1/8th scale RC wheels, fixed to 8mm solid steel axles with 17mm hex adapters. The drivetrain has a ratio of 1:7.5. First stage are pinion gears, the second stage is a GT2 belt drive. The ESCs are sensored/sensorless 60A car ESCs for now, VESCs are in transit.
The rover is almost finished now, or better, as finished as all my projects ever are.
FC is a Navio2 on a RPi3B+. I failed at installing Rpanion server on the same RPi, so I added a RPi2 for that. I also changed the ESCs to 30A blheli ESCs in bidirectional mode, the whine from the 8kHz/1kHz car ESCs was unbearable.
Driving indoors on a smooth surface works very well, but turning outdoors on asphalt makes the belts skip. The wheels are soft and have way to much grip. I bought new tires, but for now I put some strapping tape around the wheels. Yesterday I took it for a testdrive (ca. 3km asphalt and offroad) and the belts only skipped when I let the stick snap and the brakes kicked in. AUW is around 5kg, that is a lot of weight for the poor 6mm GT2 belts.
The lipos only went from 7.85V to 7.7V on that trip (multimeter).
The only parts missing are a camera and some encoders perhaps.
I uploaded a new video to my Google drive. The drive belts now have proper tension, no skipping anymore. The rover now has new wheels, gearboxes are mounted at an angle for negative camber, VESCs running on 4S with AMS AS5047D encoders, a Pixhawk 1 instead of the Navio2, Raspberry Pi 3B+ with Rpanion server, Alfa wifi and a Rpi camera with nightvision. The VESCs with encoders are really great. The rover does 30kph and more, but starts with without stuttering from a standstill, even on an incline.
Hi @count74! Awesome build. I’ve been working on pretty much the same project this summer, was wondering if I could get some advice on how you configured bidirectional BLHeli32 ESCs? I’ve set the ESCS to “Bidirectional 3D” in BLHeli32 but can’t get them to initialize after pressing the hardware safety switch. I’ve already successfully driven with normal directionality on brushless motors, using the same ESC, with no issues so I think my configuration is ‘correct’ up until that point.
I think my problem is that the ESCs are set to initialize at a PWM value of ~1500 while the servo outputs from my Pixhawk4 FC are giving it ~1000. I tried setting the SERVOx_TRIM params for servos 1 and 3 (my vehicle is also skid steering) to 1500 but after reconnecting/resetting the autopilot, these values reset to their SERVOx_MIN and do not save. Can’t seem to find a clear answer on fixing this, have already tried reflashing firmware. Any ideas are welcomed!
Since Germany is in partial lockdown, I had to build something. But instead of building something new, I changed the drive system of my last rover. I replaced the timing belt gearboxes with four 120kv sensored brushless motors, which work as hub motors in the 1/8 RC wheels. The rover now has around 3.3kW of motor power and weighs 7.4kg. The motors are controlled by four FSESC (VESC) 4.12.
It drives really well now. Here is a short video: https://drive.google.com/file/d/12G0O1roMaresIAAmisBwyvbbVF0HMv1P/view?usp=drivesdk
My daughters robot is not ardupilot powered, so I guess it does not belong here. It has an EZ-B V4 from Synthiam (EZ-Robot) as its brains.
The rover is very robust now. The motors have 10mm shafts and the closed aluminium box does not bend, even if I put a good part of my weight on it.
