272 Industrial Robotics Fundamentals Copyright Goodheart-Willcox Co., Inc. 9.1 End Effector Movement The robot’s end effector can perform many of the same movements as the human hand. The human hand and an end effector have the ability to adjust, grasp, pick up, and rotate objects. Both prehensile and nonprehensile movements are used. Prehensile movements are actions that require the use of the thumb and fi ngers fi to grasp objects. Nonprehensile movements are actions that do not require par- ticular fi nger dexterity or use of the thumb. fi 9.1.1 Prehensile Movements Fingers that can curl and an opposable thumb provide the dexterity needed for prehensile movements. The opposable thumb is very important because it enables humans and robots to pick up and manipulate very small objects. People have the ability to use their hands for various grips, Figure 9-1. The hand makes the following fi ve basic prehensile (gripping) movements: fi • Palmar grip. Wrapping the fi ngers and thumb around an object, such as a fi highlight marker, to grasp the object. • Cylindrical grip. Forming a C shape with the fi ngers and thumb to grasp a fi cylindrical object, such as a drinking glass or water bottle. • Spherical grip. Using the fi ngers and thumb to hold round objects, such as fi holding a ball. Palmar Grip Cylindrical Grip Lateral Grip Oppositional Grip Spherical Grip Goodheart-Willcox Publisher Figure 9-1. The human hand is capable of fi ve basic prehensile grips: palmar, cylindrical, spherical, lateral, and oppositional. fi