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Robots In Space

Applications outside the Earth's atmosphere are clearly a good fit for robots. It is dangerous for humans to get to space, to be in space and to return from space. Keeping robots operating reliably in space presents some unique challenges for engineers. The ultra-high vacuum in space prevents the use of most types of lubricants. The temperatures can swing wildly depending on whether the robot is in the sun light or shade. And, or course, there is almost no gravity. This is actually more of an opportunity than a challenge and leads to the possibility of some unique designs. The conceptual robot at left has 21 independent joints. On earth it would be impossible for this robot to support its own weight, but in space, the design presents some unique capabilities. The robot can reach around obstacles and through port holes. The robot also possesses a huge degree of fault tolerance. It can continue to operate with excellent dexterity even after several  joints fail.

The robot at right is called Robonaut. It is a humanoid robot designed by the Robot Systems Technology Branch at NASA's JSC  in a collaborative effort with DARPA. Robonaut's creators designed it to have dexterity, range of motion and task capabilities roughly equivalent to that of an astronaut in a space suit. Space flight hardware has been designed for servicing by astronauts for the last fifty years. It makes sense that robots would gradually pick up these tasks over time rather than suddenly replacing astronauts. The set of tools used by astronauts during space walks was the initial design consideration for the system. This drove  the development of Robonaut's dexterous five-fingered hand and human-scale arm. The robot's mix of sensors includes thermal, position, tactile, force and torque , with over 150 sensors per arm. The control system for Robonaut includes an onboard CPU with miniature data acquisition and power management in an environmentally hardened body. He's also got a nifty thermal suit to protect him from the wild temperature swings in space.

At left we see the Canadarm robot arm, a version of which has flown on every Space Shuttle flight for the last twenty years. The arm has a shoulder with 2 DOF, an elbow with 1 DOF and a 3 DOF wrist. The arm is routinely used as a mobile work platform for the astronauts, for "tossing" satellites into space and for retrieving faulty ones. Non-routine uses have included: knocking a block of ice from a clogged waste-water vent, pushing a faulty antenna into place, and activating a satellite that failed to go into proper orbit. Several of these arms have been in service for twenty years. A true robot success.

At right we see a press photograph of the Sojourner mobile robot that ultimately explored the surface of Mars. This is more of an R/C car than a robot as it was completely remote controlled from Earth, but NASA calls it a robot so I will too. In any case, the pictures it provided from the Martian surface were breath taking. Sometimes I think that really cool pictures may be NASA's greatest contributions. The deep field images produced by the Hubble telescope are in my opinion some of the greatest wonders of mankind.

The Sojourner is a 6-wheeled vehicle of a rocker bogie design which allows the traverse of obstacles a wheel diameter (13cm) in size. Each wheel is independently actuated and geared (2000:1). The front and rear wheels are independently steerable, providing the capability for the vehicle to turn in place. The vehicle has a top speed of 0.4m/min. It is powered by a 0.22sqm solar panel comprised of 13 strings of 18, 5.5mil GaAs cells each. The normal driving power requirement for the microrover is 10W.

NASA decided to develop a $288-million Flight Telerobotics Servicer (FTS) in 1987 to help astronauts assemble the Space Station, which was growing bigger and more complex with each redesign. Shown here is the winning robot design by Martin Marietta, who received a $297-million contract in May 1989 to develop a vehicle by 1993. About the best thing that can be said for the FTS project was that it generated a lot of lessons learned. The robot never flew and never will fly because it was never completed. This project demonstrated that fault-tolerance gone wild will doom a robot. The robot had so many redundant systems that there was just too much to go wrong.

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