We are presently working on the propulsion motor. For our prototype, we have chosen a 120W brushless motor (bldc) withs gear box. According to the torque and power calculation mentioned in the requirement, this motor is too big. However, it let us some margin if we have made calculation errors and if we under estimated the power required to move around in the field.
Despite its advantages, a bldc motor needs an electronic driver to work. Such a device is rather expensive. In addition, we wanted an open source one if possible. Some search on the net led us on the excellent work of Benjamin Vedder. He developed an open source bldc controller.
We ordered the PCB and list of components to build 10 controllers. However, due to the late availability of some of them, we also ordered 2 finished controller for our initial tests.