The apparatus is used as a gravity compensator for a human arm.

Some potential uses include industrial robots used in unmanned automated manufacturing lines, rehabilitation medical robots for patients or the elderly, and home robots to provide life convenience.

On some manufacturing lines, workers perform repetitious tasks and may suffer from muscle fatigue at a designated body part. These workers use only a special muscle, and may easily suffer from arthritis.

For what the arm intends to do, it does a good job. We will look at some of the ways this arm compensates for gravity, and apply it to neurosurgery. Some examples are:

• the threaded rod that moves the arms up and down, because when power is cut to the robot the arm will not drop;
• the yaw axis also gravitationally compensates the human arm, because it slides parallel to the ground; and
• the pitch axis has enough friction to prevent the arm from pitching when power is cut.

For what the arm intends to do, it does a good job. However, we are looking at the limitations of this type of gravity compensation for neurosurgery such as:

• the device itself requires different amounts of torque for different maneuvers, which is not ideal in an operating room;
• the system relies on static friction, which is not feasible for long arms (such as those used for surgery); and
• the architecture of the arm is not scalable to more moving segments.