In July, NASA launched the most sophisticated rover the agency has ever built: Perseverance. Scheduled to land on Mars in February 2021, Perseverance will be able to perform unique research into the history of microbial life on Mars in large part due to its robotic arms. To achieve this robotic capability, NASA needed to call upon innovation-driven contractors to make such an engineering feat a reality.
One of the company’s that NASA enlisted to help develop Perseverance was ATI Industrial Automation. NASA looked to have ATI adapt the company’s own Force/Torque Sensor to enable the robotic arm of Perseverance to operate in the environment of space. ATI Force/Torque sensors were initially developed to enable robots and automation systems to sense the forces applied while interacting with their environment in operating rooms or factory floors.
However, the environment of space presented unique engineering challenges for ATI’s Force/Torque Sensor. The extreme environment and the need for redundancy to ensure that any single failure wouldn’t compromise the sensor function were the key challenges the ATI engineers faced, according to Ian Stern, Force/Torque Sensor Product Manager at ATI.
“ATI’s biggest technical challenge was developing the process and equipment needed to perform the testing at the environmental limits,” said Stern. “The challenges start when you consider the loads that the sensor sees during the launch of the Atlas 5 rocket from earth. The large G forces cause the tooling on the end of the sensor to generate some of the highest loads that the sensor sees over its life.”
Once on Mars the sensor must be able to accurately and reliably measure force/torques in temperatures ranging from -110° to +70° Celsius (C). This presents several challenges because of how acutely temperature influences the accuracy of force measurement devices. To meet these demands, ATI developed the capability to calibrate the sensors at -110°C. “This required a lot of specialized equipment for achieving these temperatures while making it safe for our engineers to perform the calibration process,” added Stern.
In addition to the harsh environment, redundancy strategies are critical for a sensor technology on a space mission. While downtime on the factory floor can be costly, a component failure on Mars can render the entire mission worthless since there are no opportunities for repairs.
This need for a completely reliable product meant that ATI engineers had to develop their sensor so that it was capable of detecting failures in its
measurements as well as accurately measuring forces and torques should there be multiple failures on the measurement signals. ATI developed a patented process for achieving this mechanical and electrical redundancy.
All of this effort to engineer a sensor for NASA’s Mars mission may enable a whole new generation of space exploration, but it’s also paying immediate dividends for ATI’s more terrestrial efforts in robotic sensors.
“The development of a sensor for the temperatures on Mars has helped us to develop and refine our process of temperature compensation,” said Stern. “This has benefits on the factory floor in compensating for thermal effects from tooling or the environment.”
Stern points out as an example of these new temperature compensation strategies a solution that was developed to address the heat produced by the motor mounted to a tool changer. This heat flux can cause undesirable output on the Force/Torque data, according to Stern.
“As a result of the Mars Rover project we now have several different processes to apply on our standard industrial sensors to mitigate the effects of temperature change,” said Stern.
The redundancy requirements translated into a prototype of a Standalone Safety Rated Force/Torque sensor capable of meeting Performance Level d (PL-d) safety requirements.
This type of sensor can actively check its health and provide extremely high-resolution data allowing a large, 500 kilogram payload robot handling automotive body parts to safely detect if a human finger was pinched.
ATI is also leveraging the work it did for Perseverance to inform some of its ongoing space projects. One particular project is for a NASA Tech demo that is targeting a moon rover for 2023, a future mars rovers and potential mission to Europa that would use sensors for drilling into ice.
Stern added: “The fundamental capability that we developed for the Perseverance Rover is scalable to different environments and different payloads for nearly any space application.”
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Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.