ABSTRACT
In the roughly 40 years between man landing on the moon and today, the DC servo has been implemented in countless applications in industry. The invention of solid-state amplifiers, as well as the microprocessor, has given rise to the idea of preprogrammed machines running on direct current. The more recent resurgence of smaller DC servos running on less than 100 watts can be attributed to a few factors: (1) the revolution of personal computers and the need for their “peripheral” electromechanical devices; (2) market demand for miniaturization and portability of increasingly complex machines; and (3) recent worldwide concern for electrical safety, where governmental approvals are much easier to obtain when a device runs on less than 48 volts DC. A typical example is the print head positioning relative to the paper on an ink-jet printer. Servo is derived from the Latin noun servus, which means “slave.” For now, we define the servo as a machine that can perform a predefined action of larger power output than that exerted by the operator.
