CMG Space Robot

In a conventional robot, motions of arms and manipulators are usually effected by gear-motors at rotary joints. In a CMG space robot, the joints are passive bearings only and motions are effected by torques imposed by control moment gyros (CMGs) mounted in the body of the arm segment itself. This arrangement makes it easier for space robots to control oscillation, particularly for very large robots, where control feasibility is driven by arm joint stiffness. In space applications for large structure assembly, where very long reach is required, CMG actuation may become the preferred control solution. CMG arm actuation also has the advantages of low power consumption and low mass.

The concept of a CMG space robot arm was originated by Prof. Mason Peck of the Cornell University Sibley School of Mechanical and Aerospace Engineering. The following shows a six degree of freedom (DOF) space robotic manipulator utilizing the CMG actuation concept. This particular application for a 6 DOF CMG space robot was created by Rick Wagner at Northrop Grumman Aerospace Systems in March, 2007.

The CMG robot in stowed configuration. Each central arm CMG box is 10 x 10 x 15 inches with solar cells and second surface mirrors
for cooling the CMG electronics. Each box also contains a battery for storage of electrical power. Each of the six segments is 100
inches long. The rotary joints are passive bearings, each oriented at 90 degrees from the preceding one in the chain.

Embeded Windows movie file (.wmv) showing the rotation of a single joint in the stowed CMG robot.

Very large mirror segments could be launched stacked for assembly in space. This approach eliminates the size limitation of
existing launch vehicle shrouds and eliminates the structural requirement of withstanding launch loads. The mirrors can be
compressed with foam packing material for withstanding very high launch loads. The mirrors shown here construct a 10 meter dish.
Larger reflectors, either with larger mirror segments, or more of them, of course, can be assembled with a suitably scaled robot.

Embeded Windows movie file (.wmv) showing the translation of an object using the CMG robot.

The CMG robot uses electrostatic grippers for manipulating the mirror segments for assembly of the telescope primary reflector.

The CMG robot can also used to retrieve or dock with other spacecraft. It is seen here attached to an upper stage.

Email: Richard dot J dot Wagner at gmail dot com