Version 1.0, August 31, 2001, Copyright, Hugh Jack 1993-2001

39.1.2.3 - Payload

 

· The payload is always specified as a maximum value, this can be before failure, or more commonly, before serious performance loss.

 

· Static considerations,

  1. - gravity effects cause downward deflection of the arm and support systems
  2. - drive gears and belts often have noticeable amounts of slack (backlash) that cause positioning errors
  3. - joint play (windup) - when long rotary members are used in a drive system and twist under load
  4. - thermal effects - temperature changes lead to dimensional changes in the manipulator

 

· Dynamic considerations,

  1. - acceleration effects - inertial forces can lead to deflection in structural members. These are normally only problems when a robot is moving very fast, or when a continuous path following is essential. (But, of course, during the design of a robot these factors must be carefully examined)

 

· e.g.