A Low-Cost Fiber Optic Avionics Network for Control of an Energy Kite

The M600 energy kite has 8 turbines and a 25 m wingspan (21 November 2016)

Kurt Hallamasek Avionics Systems Engineer

Makani at X 2175 Monarch St. Alameda, CA 94501 U.S.A hallamasek@x.team x.company/makani

A Low-Cost Fiber Optic Avionics Network for Control of an Energy Kite

1_{Makani / X} 2_{Access / Alphabet}

We describe low-cost and fault tolerant data commu-nication on an energy kite with on-board flight control and power generation. The requirements on availabil-ity and safety of a modern wind turbine demand that the kite avionics system has a failure rate and fault tolerance on par with equivalent systems on commercial aircraft. Yet, substantially lower cost targets for wind turbines do not allow the straight-forward adoption of solutions that have successfully addressed similar operational require-ments in commercial and military aircraft. This paper describes the design and implementation of a low-cost avionics bus, used on a prototype energy kite, that retains safety critical traits of modern avionics buses.

The control system for flight and power generation is based on a modular and scalable architecture: motor controllers, control surface actuators and centralized computer modules each incorporate a microcontroller, purpose-designed for safety-critical applications. The microcontrollers, in addition to performing local control functions and issuing motor commands, collect sensor data over diverse short distance busses local to each node and collate this data into messages adhering to the avionics I/O protocol. These messages are routed between the over 20 nodes that are distributed on the energy kite, which has a wingspan of 25 meters, using dual-redundant Ethernet networks. Plastic Optical Fiber

is used as physical medium for low-cost robust intercon-nections and immunity to electromagnetic interference (EMI). Zero-failover time, deterministic message rout-ing with bounds on latency, and a rich set of diagnostic features are achieved, without requiring new low-level hardware protocols, by leveraging features available in modern network switches.

FC B CS B FC A FC C RecorderKite CS A Motor Motor Motor Motor Motor Motor Backup Battery MV Fault Mgmnt Motor Motor MV to LV Servo A1 Servo A2 Servo A4 Servo A5 Servo A7 Servo A8 Tether Comm Load Cell Load Cell Radio Load Cell Load Cell Servo E1 Servo E2 Servo R1 Servo R2 Lights Lights GPS Lights GPS

The M600 kite network consists of two independent Ethernet net-works, routed by two core switches (CS A, CS B). The networks link triple-redundant flight computers (FC A, FC B, FC C), motor con-trollers, control surface servo concon-trollers, telemetry links, power converters, sensors and anti-collision lights on the kite.