Engineers at the Jet Propulsion Labs in the US have overcome a watchdog timer issue in NASA’s Ingenuity rotorcraft to enable the first extraterrestrial powered flight.
The Ingenuity rotorcraft successfully flew on Mars for 90s to a height of 3m.
Ingenuity uses Qualcomm’s Snapdragon 801 processor with a Linux operating system as the system controller. This is connected to two flight-control microcontroller units (Mto perform the necessary flight-control functions. It also carries an IMU and a Garmin LIDAR Lite v3 laser altimeter for navigation. Data is relayed to the Perseverance through a low power Zigbee wireless link using a 900MHz SiFlex 02 chipset providing 250 kbit/s bandwidth.
Ingenuity uses a ProASIC3 FPGA for the sensor fusion via an ARM Cortex-M1 soft processor, but it is the dual redundant flight controllers that are the key. These are based on the Texas Instruments TMS570LC43x, based around the ARM R5F real time floating point microcontroller core running at 300MHz. THis woul dbe where the watchdog timer issue was. Interestingly the flight code is public and has been uploaded to GitHub (see link below).
A series of five test flights of the 1.8kg craft with contrarotating 1.2m rotors is planned from the 40Wh six-cell Sony lithium ion battery pack as the craft cannot recharge itself.
The watchdog was preventing the rotors spinning up. The option adopted was to add additional instructions to sidestep the watchdog and modify the process by which the two flight controllers boot up, allowing the hardware and software to safely transition to the flight state. These were included in a revised version of the flight control software that was uploaded to Perseverance. This was then loaded into Ingenuity and validated.
Other critical functions such as power, communications, and thermal control are stable, said the team.
“The Mars Helicopter project has gone from ‘blue sky’ feasibility study to workable engineering concept to achieving the first flight on another world in a little over six years,” said Michael Watkins, director of JPL. “That this project has achieved such a historic first is testimony to the innovation and doggedness of our team here at JPL, as well as at NASA’s Langley and Ames Research Centers, and our industry partners. It’s a shining example of the kind of technology push that thrives at JPL and fits well with NASA’s exploration goals.”
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