This invention concerns a communication system between at least one device control unit connected to a device to be controlled and at least one human-machine interface through a series communication bus. At least one chirality center is provided with a distance of up to 5 atomic bonds from the functional group. A back drive torque of the first power transmission unit is larger than a back drive torque of the second power transmission unit. A third routine is arranged to compute a set of navigation parameters for the route.