Modularity of Spiri Mu
Benefits of Modular Design
Inside a Spiri Mu are many separable parts and systems of parts. This makes repair and replacement work easy; if a part breaks in a crash, the damage and the cost is limited to the broken part. Similarly, if a part upgrade becomes available. All told, this increases the operating life, and decreases the lifetime operating cost, of a Spiri Mu.
The power system consists of a separable battery pack and power distribution board. The power distribution board directly feeds certain sensors, the propulsion system, the flight control system, and the cognitive system.
The propulsion system consists of a 4-in-1 electronic speed controller (ESC) running BLHeli-32, and the four motors. The motors are mounted on a three part mechanical system consisting of a landing gear and two-part motor holster. In crashes, the landing gears tend to break first, and are therefore the easiest parts to replace.
Flight Control System
The flight control system consists of a flight control board (the PixRacer) running PX4 and a GNSS with compass. The GNSS collects data from the GPS, GLONASS, and Galileo satellite networks. There are three compasses, an accelerometer and gyroscope, a barometer within this equipment, supported by a range-finding sensor and the vision system. The two boards of the flight control system are mounted on the same mechanical plate, meaning they can be separated for testing and recalibration as needed.
The cognitive system consists of the Nvidia TX2 mounted on a carrier board (the ConnectTech Elroy). It is located at the center of the robot, protected by an interior frame, an outer shell, and the other systems on Spiri. In a crash, it is the last part to get damaged, and it is the most valuable. The cognitive system is responsible for decisions, communications, and processing data in real time. It passes power on to the vision system.
Heat Transfer System
The heat transfer system consists of a heat pipe made of aluminum and containing acetone, with a cotton cartridge attached and soaked in isopropanol. This provides passive heat transfer and evacuation ultimately through the evaporation of the isopropanol. The heat pipe is in direct contact with the TX2 and is close to the ESC.
The vision system consists of two global shutter cameras, two interposing boards, and the cabling that connects them together. This cabling causes simultaneous shutter movements, meaning the cameras are not only global shutter, but hardware synchronized.
The communications system consists of two Wi-Fi antennas, a mini-PCIE mounted 4G cellular modem with antennas, and a 900Hz radio receiver connected to the flight control system's telemetry communications channel. Depending on conditions and the power of connecting antennas, the Wi-Fi range is under 1km, the telemetry radio is under 10km, and the 4G modem connects everywhere in cell tower range.
The protective system consists of the outer shell parts, including a dorsal shell and two ventral shells, one containing the battery pack, and the other containing the range finding sensor and the cameras.