An extension of the concept of the group

Abstract

A group is traditionally regarded as part of a mechanism which has zero mobility when its external pairs are connected to the other parts of the mechanisms. This has meant that actuators have not been able to exist in a group. Such a group has been called an Assur group. In this note the concept of a group is extended to groups with many degrees of mobility. Such groups must have as many actuator pairs as degrees of mobility.