Stress-tek and Micro-Measurements Strain Gages, Giving a Sense of Touch to the Mars Rover Perseverance

Man’s desire to explore Space specifically Mars continues to push technology to new limits.  Mars’ distance to Earth and its hostile environmental conditions present monumental challenges.  This week NASA’s Mars Exploration Program launched the latest edition of the Perseverance rover.  Micro-Measurements Advanced Sensor Technology helped make it possible with sensors that have the reliability, stability and durability to meet these challenges.

Part of the Rover’s mission is to take soil and rock samples from the Martian surface.  The Rover is equipped with a robotic arm that holds the drilling and other sensing hardware.  Mission success demands absolute reliability from all systems.  Since it is impossible to retrieve the Rover for repairs, obtaining force feedback during the drilling operation is critical to ensure that the drill and drive mechanism is positioning is precise with the highest level of reliability and survivability. 

To solve this technical problem, NASA / JPL recruited support from key vendors in the sensor industry to develop purpose-built sensors including six-degree-of-freedom (6DOF) transducers for this mission critical application.  Motiv Space Systems, a sub-contractor to NASA located in Pasadena, CA, was chosen to develop this transducer.  Motiv, while well suited to the development of mission critical hardware, recognized they needed the support of a highly skilled staff of strain gage based transducer experts to perform the critical strain gage installation process.  Motiv reached out to Micro-Measurements and its sister company Stress-Tek located in Kent, WA for assistance.  Stress-tek’s role was to bond Micro-Measurements strain gages to a 6DOF transducer element, and complete initial testing.  Some of these transducers were used to development testing while others were on the final Rover for deployment to Mars.

The 6DOF sensor was incorporated into the shoulder joint of a robotic arm to provide sensing and structural support.  As the rover traverses the Martian landscape performing tests, taking samples and gathering data, the sensor provides complex force data to ensure the entire system operates within pre-determined limits as well as providing data regarding hardness of samples.

The technical requirements included support of sampling operations for the life of the mission, executing critical deployment and positioning of instruments in the Mars environment, and providing sufficient force sensing capabilities to support docking operations, preload operations and load limiting fault protections.

The Sensing elements:

Micro-Measurements® strain gages were specifically selected for use on the six-degree-of-freedom (6DOF) sensor in the robotic arm. Micro-Measurement’s available strain gage geometries and constructions far exceed the alternate options in the market. The Micro-Measurements® strain gages available off the shelf not only made this sensor technically feasible, they worked flawlessly in terms of sensor combined errors and measurement crosstalk. Additionally, the use of support applications accessories from Micro-Measurements®, which, are rated for space flight, ensured the necessary reliability of the sensor system.

The skilled technicians at Stress-tek were able to locate and install strain gages with the required precision to meet functional specifications.  These highly sensitive strain gages, manufactured to exacting tolerances and the miniature size were the only choice to meet the design criteria of this critical sensing system for measurement of force, torque and bending in multiple axis.