Alignment characteristics of magnetic fields have been used to achieve precision movement and positioning of objects. A key principle of operation of an alternating-current (AC) motor is that a permanent magnet will rotate so as to maintain its alignment within an external rotating magnetic field. This effect is the basis for the early AC motors including the “Electro Magnetic Motor” for which Nikola Tesla received U.S. Pat. No. 381,968 on May 1, 1888. On Jan. 19, 1938, Marius Lavet received French Patent 823,395 for the stepper motor which he first used in quartz watches. Stepper motors divide a motor's full rotation into a discrete number of steps. By controlling the times during which electromagnets around the motor are activated and deactivated, a motor's position can be controlled precisely. Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems. They are used in industrial high speed pick and place equipment and multi-axis computer numerical control (CNC) machines. In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. They are used in packaging machinery, and positioning of valve pilot stages for fluid control systems. They are also used in many commercial products including floppy disk drives, flatbed scanners, printers, plotters and the like.
Although alignment characteristics of magnetic fields are used in certain specialized industrial environments and in a relatively limited number of commercial products, their use for precision alignment purposes is generally limited in scope. For the majority of processes where alignment of objects is important, e.g., residential construction, comparatively primitive alignment techniques and tools such as a carpenter's square and a level are more commonly employed. Moreover, long trusted tools and mechanisms for attaching objects together such as hammers and nails; screw drivers and screws; wrenches and nuts and bolts; and the like, when used with primitive alignment techniques result in far less than precise residential construction, which commonly leads to death and injury when homes collapse, roofs are blown off in storms, etc. Generally, there is considerable amount of waste of time and energy in most of the processes to which the average person has grown accustomed that are a direct result of imprecision of alignment of assembled objects. Machined parts wear out sooner, engines are less efficient resulting in higher pollution, buildings and bridges collapse due to improper construction, and so on.
It has been discovered that various field emission properties can be put in use in a wide range of applications.