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View for Terrain Images, Not Used for Its Own and Relied on a Set of Flight-Con- Tion Camera Tracks Visual Features on the Navigate in Complex Terrain GENERAL POSS: TO SWARM, BEYOND AG/MINING P.10 OR NOT TO SWARM P.16 TAKES OFF P.58 USE CASES inside June/July 2021 unmanned systems INSIDE ENGINEERING, POLICY AND PRACTICE InsideUnmannedSystems.com SPECIAL COLLABORATION ISSUE JPL AND AEROVIRONMENT MARSon SUCCEED AT SMART COLLABORATION PUBLISHED BY AUTONOMOUS MEDIA, LLC COLLABORATION Mars Helicopter Project INSIDE THE INGENUITY HELICOPTER: Teamwork on Mars pril 19th saw what some have punching above your weight. The Mars Helicopter christened “a second Wright “Now that Ingenuity is actually flying at Project, a.k.a. A Brothers moment”—namely, the Mars, we can begin to assess how things Ingenuity, lifts off successful first powered controlled flight stack up against expectations,” noted Håvard from the Martian by an aircraft on another world. Reaching Grip, Mars helicopter chief pilot for NASA’s surface, near the Perseverance rover. Mars on the underside of the Perseverance Jet Propulsion Laboratory (JPL). rover, the tiny, autonomous Mars Ingenuity Ingenuity represents the years-long Helicopter (5.4" x 7.7" x 6.4") spun its 4-foot collaboration between NASA/JPL, ma- rotors and hovered 10 feet off the ground jor unmanned systems manufacturer for 30 seconds. By its third flight, a few AeroVironment and a bevy of other compa- days later, Ingenuity would rise 16 feet (5 nies. The articles that follow chronicle how meters) up, and fly 164 feet (50 meters) at JPL created the craft’s unique navigation sys- a top speed of 6.6 ft/sec (2 m/sec). Back in tem and how AeroVironment’s engineering 1903, the Wright Brothers logged 120 feet team stepped up in the electrical, mechani- to complete the first controlled heavier- cal, systems and vehicle flight control areas. than-air powered flight. Now, squaring “Working with JPL, I think we’ve that circle, Ingenuity carries a piece of fab- learned a lot,” AeroVironment engineer- ric from the Wright Flyer’s wing, and its ing lead Ben Pipenberg said. “It’s a very flight site is called Wright Brothers Field. AV project, it’s this weird, first-of-its-kind Six weeks and six flights into its mission vehicle, but JPL is the best at what they do as we write, Ingenuity has demonstrated by far, in terms of space robotics, planetary the ability to fly on a planet more than 170 robotics, and there was a huge amount we million miles from earth in an atmosphere were able to learn from them that we’ll be 1% as thick as ours. The near-miniature ve- able to pull into a lot of our work in the fu- hicle has proved to be an intrepid explorer ture. It was really good teaming. even as it’s survived a computer anomaly “There’s a huge amount of pride, a lot of on its most recent mission. Talk about excitement, that it’s flying on Mars.” Photo courtesy of NASA/JPL. www.insideunmannedsystems.com June/July 2021 COLLABORATION Mars Helicopter Project Mars Helicopter Project COLLABORATION flights began and ended within an area that had been pre-inspected and deter- mined to be safe in terms of obstacles and ground slope. Ingenuity conducted five flights accord- ing to its programmed lifeline across a pe- riod of 31 Earth days, or 30 sols on Mars. “Now that Ingenuity Then came the surprise ending-to-date, but more on that later. For the helicopter’s pre-arranged auton- is actually flying omous test flights, under the NASA rubric at Mars, we can begin to assess of “technology demonstration,” it took off, how things stack up climbed, hovered, translated between a set against expectations.” of waypoints, then descended to land again (see Figure 1). Although the helicopter did Håvard Grip, Mars helicopter chief pilot, JPL operate independently during flight, the waypoints were specified from Earth prior to flight. FIGURE 1 Illustration of a Mars Helicopter flight, beginning and ending in the same AUTONOMY? pre-inspected safe area. This, however, raises an interesting and somewhat subtle point: is Ingenuity truly Pipenberg, AeroVironment’s engineer- autonomous? ing lead on the Ingenuity project. “When It depends on your definition. Engineers Perseverance landed, it used terrain-rel- at AeroVironment, which constructed ma- ative navigation, and it was making de- jor elements of the helicopter but was not cisions based on outside observable data involved in the guidance, navigation and that it was collecting without human When Ingenuity, the little Autonomously, in other words. Radio sig- control (GNC) system design, weighed in input. That would be an autonomous helicopter that could, sprang Autonomously Alone nals from NASA Command take 15 min- on the issue. system. Ingenuity is not doing that. It’s from the Martian surface JPL: on the Red Planet utes and 27 seconds to travel the 173 million “It certainly is making autonomous deci- essentially using VIO—visual-inertial into the wispy thin Martian miles (278.4 million kilometers) to Mars. sions [in managing rotor speed and pitch] odometry—just to navigate over the o make this happen, NASA invested Mode Commander, setting the overall Once on the surface, the more well-en- to get more cyclic to overcome a wind gust,” ground in a pre-determined flight path, atmosphere, it knocked down $85 million to build Ingenuity, ac- mode for the flight control system; the dowed Perseverance rover served as a com- said Jeremy Tyler, senior aeromechanical uploaded from Earth.” all kinds of firsts. The first T commodate it onboard Perseverance Guidance subsystem, providing refer- munications relay link so the helicopter and engineer. “It’s managing its altitude, it’s Tyler concurred, after a fashion. “It’s powered, controlled flight for the long interplanetary flight and para- ence trajectories for the flight path; the Mission Team on Earth could communicate. managing its position, all by itself without doing its own simple autonomy. But cer- on another planet. The first chute deployment, and operate it once it Navigation subsystem, giving estimates It passed flight instructions from NASA’s any external intervention.” tainly no sophisticated mission planning autonomous flight. The first reached distant Mars. of the vehicle state; and the Control sub- Jet Propulsion Laboratory in Pasadena, “It’s inherently unstable,” added Matt or decision-making.” use of an inertial navigation There’s plenty to marvel at in this un- system, commanding the actuators based California, to Ingenuity. From a Martian Keennon, technical lead for rotor system dertaking, which took the fertile minds of on the reference trajectories and the ve- hillock 65 meters away, the four-wheeled development. “It can’t fly for a half-second THE NAVIGATION SYSTEM system and visual odometry NASA’s Jet Propulsion Laboratory (JPL), hicle state. rover observed and recorded its four-bladed without making decisions based on the in- Engineers at JPL under the direction of across an alien world. NASA Ames Research Center, NASA The specific challenges for the naviga- offspring’s history-making flights. ertial measurement unit [IMU] and driv- Håvard Grip, Mars helicopter chief pi- Langley Research Center and companies tion system onboard the UAV include: While hovering on its four initial flights, ing the control system.” lot, developed and assembled the visual- that included AeroVironment, Inc. (see • A lack of global navigation aids, such as the helicopter’s navigation camera and “There’s no [navigation] decisions inertial navigation system emphasizing by Alan Cameron, PNT Editor accompanying feature) on a six-year jour- GPS or a strong magnetic field. laser altimeter fed information into the being made onboard,” countered Ben robustness, but with a correspondingly ney from inspiration to realization. Awe • A large communication time lag navigation computer to ensure Ingenuity will be confined within this article to the between Earth and Mars, preventing remained not only level, but within the phenomenon of Ingenuity’s navigation real-time communication during flight. borders of its 10x10 meter airfield—a (TOP RIGHT) The Ingenuity Mars Helicopter’s navigation camera system. • A harsh radiation environment patch of extraterrestrial real estate cho- “As we continue with our flights captures the helicopter’s shadow on that can adversely affect computing sen for its flatness and lack of obstruc- on Mars, we will keep digging deeper into the data…” the surface of Jezero Crater during the NAVIGATING THE SUBSYSTEMS elements. tions. Because landing hazard avoidance Håvard Grip, Mars helicopter chief pilot, JPL rotorcraft’s second experimental test The Mars copter’s flight control system Because of the time-lag challenge, was not prioritized for this technology flight on April 22. consists of four main subsystems: the Ingenuity has to perform on its own. demonstration, each of those four initial Photos and figures courtesy of NASA/JPL-Caltech. www.insideunmannedsystems.com June/July 2021 June/July 2021 www.insideunmannedsystems.com COLLABORATION Mars Helicopter Project Mars Helicopter Project COLLABORATION limited position accuracy and ability to facing view for terrain images, not used for its own and relied on a set of flight-con- tion camera tracks visual features on the navigate in complex terrain. In particu- navigation. trol algorithms that we developed here on ground, under the assumption that all fea- lar, the system assumes that features ob- Figure 2 shows Ingenuity’s avionics Earth, before Ingenuity was even launched tures are located on a ground plane with a served by the navigation camera lie on an system architecture. A radiation-tolerant to Mars.” known slope. This provides horizontal ve- approximate ground plane with known field-programmable gate array (FPGA) When the copter rests on the ground, locity as well as roll and pitch attitude, and slope. This is why the landing field was function routes sensor data and traffic preparing to take off, the inclinometer helps limit the drift in horizontal position chosen and why the first four flights did between other computing elements and estimates initial roll and pitch attitude.
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