Page 472 - Sensors and Control Systems in Manufacturing

Sensors in Flexible Manufacturing Systems
often capable of picking up an array of products at one time. They 425
may utilize various sensors to aid the robot system in locating, han-
dling, and positioning products.

8.14.4 Movement and Singularities
Most articulated robots perform by storing a series of positions in
memory, and moving to them at various times in their programming
sequence. For example, a robot that is moving items from one place to
another might have a simple “pick and place” program similar to the
following:
Define points P1–P5:

• Safely above workpiece (defined as P1)
• 10 cm Above bin A (defined as P2)
• At position to take part from bin A (defined as P3)
• 10 cm Above bin B (defined as P4)
• At position to take part from bin B (defined as P5)
• Define program:
• Move to P1
• Move to P2
• Move to P3
• Close gripper
• Move to P2
• Move to P4
• Move to P5
• Open gripper
• Move to P4
• Move to P1 and finish
For a given robot, the only parameters necessary to completely
locate the end effector (gripper, welding torch, etc.) of the robot are
the angles of each of the joints or displacements of the linear axes (or
combinations of the two for robot formats such as SCARA). However,
the points can be defined in many different ways. The most common
and convenient way of defining a point is to specify a Cartesian coor-
dinate for it (i.e., the position of the “end effector” in mm in the X, Y,
and Z directions relative to the robot’s origin). In addition, depending
on the types of joints a particular robot may have, the orientation of
the end effector in yaw, pitch, and roll and the location of the tool
point relative to the robot’s faceplate must also be specified. For a
jointed arm, these coordinates must be converted to joint angles by
the robot controller, and such conversions are known as Cartesian