Feedback Control: An Invisible Thread in the History of Technology

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Table of Contents

Introduction
The Escapement
The Governor
The Aileron
The Gyro
The Amplifier
Conclusion

Introduction

The concept of feedback control facilitated great waves of technological and scientific advancements in the last century.

It led to innovations, which had significant impacts on technology during the Scientific Revolution, the Age of Electronics, the Age of Aviation, Industrial Revolution, and the Space Age. In this regard, this paper will discuss the technological innovations that were based on feedback control systems.

The Escapement

The invention of the mechanical clock towards the end of the 13^th century led to a remarkable accuracy and reliability in the measurement of time. Every mechanical clock had a regulator, which controlled its operations.

One of the earliest regulators to be used in mechanical clocks was referred to as the verge-and-foliot escapement. The escapement, which had been invented by 1283, had two components, namely the verge and the foliot. The former consisted of an escape wheel, which was rotated by weights.

It also had a pair of pallets that were fitted on a revolving shaft. The two components of the verge made periodic contacts as they rotated. The periodic contacts between the escape wheel and the pallet provided a feedback mechanism, which regulated the clocks speed.

The escapement was an important improvement since it measured time in terms of the period of contact between the two components of the verge.

This technique was better than measuring time through an incessant flow of water or wax. Reading the clock involved counting the contacts between the escape wheel and the pallets, which was a digital process.

Christian Huygens improved the verge-and-foliot escapement in 1657. This involved substituting the oscillations of a pendulum for the dynamics of the verge-and-foliot system, which led to the development of the earliest pendulum clock.

The use of a pendulum reduced reliance on contact to measure time. However, its application was negatively affected by the circular errors that occurred due to the long distance covered by the pendulum as it oscillated.

Consequently, Robert Hooke and William Clement developed the anchor escapement, which eliminated the circular error by reducing the amplitude of the pendulum.

John Harrison improved the anchor escapement by making wooden clocks, which had high accuracy and did not require regular lubrication.

In the pendulum clock, feedback control was used to transfer energy to the pendulum in the appropriate phase in order to maintain the speed of oscillation and the accuracy of the clock.

The escapement significantly increased the accuracy of mechanical clocks and made it possible to measure time independently of nature. This led to the use of time as a concept in financial investments and the service of labor.

Additionally, the mechanical clock outperformed methods such as graduated candles in terms of the accuracy of measuring time.

The Governor

Prior to the adoption of fossil fuels in production, machines were powered by wind and waterpower. Wind power was found to be unreliable due to the constant variation of its speed and direction.

Edmund Lee addressed the problem of fluctuating wind speed by allowing the sails of windmills to revolve around their long axis. Additionally, he introduced fantails to enable the mills cap to turn in the direction of the wind without human intervention.

During high-speed wind, the distance between millstones widened. Thus, it was essential to boost the force between the millstones in order to improve their efficiency. The use of governors to regulate the operation of millstones addressed this problem.

In this case, the two types of governors that were used included the lag and the centrifugal governors. By 1783, James Watt had invented a steam-powered engine that could produce a circular motion.

John Rennie improved Watts invention by using a centrifugal governor to control the engines velocity. In this case, the feedback system enabled the engine to control itself. Thus, it became possible to use large amounts of energy to power engines during Industrial Revolution.

The Aileron

Earlier enthusiasts of manned flight realized that apart from ensuring stability, a flying machine had to maneuver and to counter any disturbances.

Consequently, the Wright brothers developed several innovations including the biplane wing structure, wing warping, lightweight engines, and propellers to illustrate machine-powered manned flight.

Wing warping was the main improvement, which led to manned flight by facilitating controlled turning of the aircraft.

In 1908, Glenn Curtiss improved on the Wrights innovation by using a pair of ailerons rather than wing warping for lateral control. Ailerons functioned as detached variable aerodynamic surfaces. The use of ailerons was better than wing warping in two ways.

First, it made it possible to roll the airplane, as well as, to ensure the lateral control of the aircraft without interfering with its lift.

Second, it facilitated autonomous management of each of the airplanes axes. The realization of the three-axis rotary control of the airplane was facilitated by the use of the rudder, the elevator, and the ailerons. This achievement effectively ushered in the Age of Aviation.

The Gyro

The gyro was developed by Elmer Ambrose Sperry and used by Lawrence Sperry and Emile Cachin to improve the stability of moving aircrafts.

The gyro was a revolving wheel fitted on a pivoted support. The rotating axis of the wheel remained on its course as the pivoted supports revolved around it. The gyro and the ailerons created a feedback mechanism, which stabilized the movement of the airplane.

Apart from stabilizing the motion of aircrafts, gyros were used for sensing and actuation in order to stabilize automobiles and ships. Additionally, the use of gyros in aviation applications facilitated inertial navigation.

In particular, it led to the development of gyrocompasses that had a mechanism for determining the direction of motion. Moreover, it led to the development of rate gyros and accelerometers, which gave indications for determining location.

These advancements facilitated the control of missiles, submarines, and space ships. Furthermore, the use of gyro based feedback loops led to autopilot technology, thereby ushering in the Space Age.

The Amplifier

One of the most important innovations in the Age of Electronics was the invention of the amplifier. An amplifier is a gadget that magnifies the amplitudes of signals without distorting their properties. Despite not being a feedback device, an amplifier plays a key role in a feedback control system.

The Positive Feedback Amplifier

In 1880, Thomas Alva Edison discovered the possibility of transmitting current through a vacuum. This discovery, which was referred to as the Edison effect, facilitated the development of the radio.

In his study of the Edison effect, Fleming realized in 1904 that AC radio waves could be corrected using a vacuum tube with a wire and a plate. Lee de Forest improved Flemings innovation by adding a third wire in the tube.

This enabled him to control and amplify the signal applied to the wire, thereby developing the first electronic amplifier. The positive feedback system led to the development of the triode-based amplifier circuit. Edwin Armstrong accomplished this innovation in 1912.

The triode-based circuit outperformed all other types of amplifiers that had been developed. Armstrongs innovation replaced the use of huge generators to transmit voice and music.

The Negative Feedback Amplifier

By 1911, it was possible to make phone calls over long distances. However, it was not feasible due to sound distortion. The problem of sound distortion was addressed through a negative feedback mechanism.

The use of a negative feedback amplifier facilitated telecommunication over long distances by improving the quality of sound.

Additionally, the concept of negative feedback enabled William Hewlett and David Packard to develop audio oscillating devices for testing sound equipment.

The work of Hewlett and Packard led to the emergence of the Silicon Valley, which is known for modern electronic technological advancements.

Conclusion

The use of feedback innovation facilitated the various waves of scientific and industrial developments. The mechanical clock significantly improved the measurement of time, thereby ushering in the Scientific Revolution.

The centrifugal governor facilitated the control of steam engines during the industrial revolution. The aileron made controlled flight possible, whereas the gyro improved guidance and control of spacecrafts.

The positive feedback and the negative feedback systems were important during the electronic revolution since they facilitated the development of amplifiers with low distortion. It is likely that feedback control will be an important aspect of future technological advancements.

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