Page 453 - Sensors and Control Systems in Manufacturing

Sensors in Flexible Manufacturing Systems

FIGURE 8.28 Diameter and height measurement. 407

FIGURE 8.29 The end effector sensor can be used to direct a stepper motor
to rotate the part until a match between part and standard is found.

8.10 End Effector Linear Variable-Displacement
Transformer Sensor
Sensing capability in a robot can have widely ranging degrees of sophis-
tication in addition to a variety of sensing media. For instance, sensing
capability can vary from a simple photoelectric cell to a complex, three-
dimensional sound-vision system as described in the previous section.
The linear variable-displacement transformer (LVDT) sensor is an
electromechanical device that can be attached to a robotic manipula-
tor or can be itself a drive control for a robotic gripper. The LVDT
produces an electrical output proportional to the displacement of a
separate movable core. It consists of a primary coil and two secondary
coils, intricately spaced on a cylindrical form. A free-moving rod-shaped
magnetic core inside the coil assembly provides a path for the mag-
netic flux linking the coils. A cross-section of the LVDT sensor and a
plot of its operational characteristics are shown in Figs. 8.30 and 8.31.