Robot Arm Singularities

A robot arm singularity refers to a specific configuration of a robotic arm where it loses one or more degrees of freedom, resulting in a loss of control or unpredictable behavior. It's a situation that can occur when the joints of a robot arm align in a certain way.

The two common types of singularities in robot arms are:

Joint Limit Singularity

This type of singularity occurs when one or more joints of the robot arm reach their mechanical limits. For example, if a joint can rotate between -180 degrees and +180 degrees, a joint limit singularity can happen when the joint reaches either extreme. In such a case, the robot arm loses a DOF and cannot move freely.

Wrist Singularity

This singularity arises when the axes of the robot arm's wrist joints align in a way that restricts the motion of the end effector (the tool or gripper attached to the arm). In a three-joint wrist, the axes of the joints are typically orthogonal to each other, allowing for unrestricted movement. However, when these axes align, the robot arm loses one or more DOF, and certain directions of movement become impossible or limited.

When a robot arm enters a singularity, it can lead to issues such as uncontrollable or jerky movements, inability to reach certain points in space, or unpredictable behavior. Singularity avoidance algorithms are often employed in robotics to prevent or minimize the occurrence of singularities. These algorithms help the robot arm to navigate around singular configurations, maintaining smooth and reliable movement.