Key Elements of Mechatronics
The study of mechatronic systems can be divided into the following areas of specialty:
1. Physical Systems Modeling
2. Sensors and Actuators
3. Signals and Systems
4. Computers and Logic Systems
5. Software and Data Acquisition
Attempts to construct automated mechanical systems has an interesting history. Actually, the term “automation”
was not popularized until the 1940s when it was coined by the Ford Motor Company to denote
a process in which a machine transferred a sub-assembly item from one station to another and then
positioned the item precisely for additional assembly operations. But successful development of automated
mechanical systems occurred long before then. For example, early applications of automatic control systems appeared in Greece from 300 to 1 B.C. with the development of float regulator mechanisms [7].
Two important examples include the water clock of Ktesibios that used a float regulator, and an oil lamp
devised by Philon, which also used a float regulator to maintain a constant level of fuel oil. Later, in the
first century, Heron of Alexandria published a book entitled
Pneumatica
that described different types of
water-level mechanisms using float regulators.
In Europe and Russia, between seventeenth and nineteenth centuries, many important devices were
invented that would eventually contribute to mechatronics. Cornelis Drebbel (1572–1633) of Holland devised
the temperature regulator representing one of the first feedback systems of that era. Subsequently, Dennis
Papin (1647–1712) invented a pressure safety regulator for steam boilers in 1681. Papin’s pressure regulator
is similar to a modern-day pressure-cooker valve. The first mechanical calculating machine was invented by
Pascal in 1642 [8]. The first historical feedback system claimed by Russia was developed by Polzunov in 1765
[9]. Polzunov’s water-level float regulator, illustrated in Figure 1.2, employs a float that rises and lowers in
relation to the water level, thereby controlling the valve that covers the water inlet in the boiler.
Further evolution in automation was enabled by advancements in control theory traced back to the
Watt flyball governor of 1769. The flyball governor, illustrated in Figure 1.3, was used to control the speed of a steam engine [10]. Employing a measurement of the speed of the output shaft and utilizing
the motion of the flyball to control the valve, the amount of steam entering the engine is controlled. As
the speed of the engine increases, the metal spheres on the governor apparatus rise and extend away from
the shaft axis, thereby closing the valve. This is an example of a feedback control system where the
feedback signal and the control actuation are completely coupled in the mechanical hardware.
These early successful automation developments were achieved through intuition, application of practical
skills, and persistence. The next step in the evolution of automation required a
theory
of automatic control.
The precursor to the numerically controlled (NC) machines for automated manufacturing (to be developed
in the 1950s and 60s at MIT) appeared in the early 1800s with the invention of feed-forward control of
weaving looms by Joseph Jacquard of France. In the late 1800s, the subject now known as control theory
was initiated by J. C. Maxwell through analysis of the set of differential equations describing the flyball
governor [11]. Maxwell investigated the effect various system parameters had on the system performance.
At about the same time, Vyshnegradskii formulated a mathematical theory of regulators [12]. In the 1830s,
Michael Faraday described the law of induction that would form the basis of the electric motor and the
electric dynamo. Subsequently, in the late 1880s, Nikola Tesla invented the alternating-current induction
motor. The basic idea of controlling a mechanical system automatically was firmly established by the end
of 1800s. The evolution of automation would accelerate significantly in the twentieth century.
The development of pneumatic
control elements in the 1930s matured to a point of finding applications
in the process industries. However, prior to 1940, the design of control systems remained an art generally
characterized by trial-and-error methods. During the 1940s, continued advances in mathematical and
analytical methods solidified the notion of control engineering as an independent engineering discipline.
In the United States, the development of the telephone system and electronic feedback amplifiers spurred
the use of feedback by Bode, Nyquist, and Black at Bell Telephone Laboratories [13–17]. The operation
of the feedback amplifiers was described in the frequency domain and the ensuing design and analysis
practices are now generally classified as “classical control.” During the same time period, control theory
was also developing in Russia and eastern Europe. Mathematicians and applied mechanicians in the
former Soviet Union dominated the field of controls and concentrated on time domain formulations
and differential equation models of systems. Further developments of time domain formulations using
state variable system representations occurred in the 1960s and led to design and analysis practices now
generally classified as “modern control.”
The World War II war effort led to further advances in the theory and practice of automatic control
in an effort to design and construct automatic airplane pilots, gun-positioning systems, radar antenna
control systems, and other military systems. The complexity and expected performance of these military
systems necessitated an extension of the available control techniques and fostered interest in control
systems and the development of new insights and methods. Frequency domain techniques continued to
dominate the field of controls following World War II, with the increased use of the Laplace transform,
and the use of the so-called s-plane methods, such as designing control systems using root locus.

the production process was a high priority beginning in the 1940s. During the 1950s, the invention of
the cam, linkages, and chain drives became the major enabling technologies for the invention of new
products and high-speed precision manufacturing and assembly. Examples include textile and printing
machines, paper converting machinery, and sewing machines. High-volume precision manufacturing
became a reality during this period. The automated paperboard container-manufacturing machine
employs a sheet-fed process wherein the paperboard is cut into a fan shape to form the tapered sidewall,
and wrapped around a mandrel. The seam is then heat sealed and held until cured. Another sheet-fed
source of paperboard is used to cut out the plate to form the bottom of the paperboard container,
formed into a shallow dish through scoring and creasing operations in a die, and assembled to the cup
shell. The lower edge of the cup shell is bent inwards over the edge of the bottom plate sidewall, and
heat-sealed under high pressure to prevent leaks and provide a precisely level edge for standup. The
brim is formed on the top to provide a ring-on-shell structure to provide the stiffness needed for its
functionality. All of these operations are carried out while the work piece undergoes a precision transfer
from one turret to another and is then ejected. The production rate of a typical machine averages over
200 cups per minute. The automated paperboard container manufacturing did not involve any nonmechanical
system except an electric motor for driving the line shaft. These machines are typical of
paper converting and textile machinery and represent automated systems significantly more complex
than their predecessors.
The development of the microprocessor in the late 1960s led to early forms of computer control in
process and product design. Examples include numerically controlled (NC) machines and aircraft control
systems. Yet the manufacturing processes were still entirely mechanical in nature and the automation
and control systems were implemented only as an afterthought. The launch of Sputnik and the advent
of the space age provided yet another impetus to the continued development of controlled mechanical
systems. Missiles and space probes necessitated the development of complex, highly accurate control
systems. Furthermore, the need to minimize satellite mass (that is, to minimize the amount of fuel required
for the mission) while providing accurate control encouraged advancements in the important field of
optimal control. Time domain methods developed by Liapunov, Minorsky, and others, as well as the
theories of optimal control developed by L. S. Pontryagin in the former Soviet Union and R. Bellman in
the United States, were well matched with the increasing availability of high-speed computers and new
programming languages for scientific use.
Advancements in semiconductor and integrated circuits manufacturing led to the development of a
new class of products that incorporated mechanical and electronics in the system and required the two
together for their functionality. The term mechatronics was introduced by Yasakawa Electric in 1969 to
represent such systems. Yasakawa was granted a trademark in 1972, but after widespread usage of the
term, released its trademark rights in 1982 [1–3]. Initially, mechatronics referred to systems with only
mechanical systems and electrical components—no computation was involved. Examples of such systems
include the automatic sliding door, vending machines, and garage door openers.
In the late 1970s, the Japan Society for the Promotion of Machine Industry (JSPMI) classified mechatronics
products into four categories [1]:
1.
Class I:
Primarily mechanical products with electronics incorporated to enhance functionality.
Examples include numerically controlled machine tools and variable speed drives in manufacturing
machines.
2.
Class II:
Traditional mechanical systems with significantly updated internal devices incorporating
electronics. The external user interfaces are unaltered. Examples include the modern sewing
machine and automated manufacturing systems.
3.
Class III:
Systems that retain the functionality of the traditional mechanical system, but the internal
mechanisms are replaced by electronics. An example is the digital watch.
4.
Class IV:
Products designed with mechanical and electronic technologies through synergistic
integration. Examples include photocopiers, intelligent washers and dryers, rice cookers, and
automatic ovens.
The enabling technologies for each mechatronic product class illustrate the progression of electromechanical
products in stride with developments in control theory, computation technologies, and microprocessors.
Class I products were enabled by servo technology, power electronics, and control theory.
Class II products were enabled by the availability of early computational and memory devices and custom
circuit design capabilities. Class III products relied heavily on the microprocessor and integrated circuits
to replace mechanical systems. Finally, Class IV products marked the beginning of true mechatronic
systems, through integration of mechanical systems and electronics. It was not until the 1970s with the
development of the microprocessor by the Intel Corporation that integration of computational systems
with mechanical systems became practical.
The divide between classical control and modern control was significantly reduced in the 1980s with
the advent of “robust control” theory. It is now generally accepted that control engineering must consider
both the time domain and the frequency domain approaches simultaneously in the analysis and design
of control systems. Also, during the 1980s, the utilization of digital computers as integral components
of control systems became routine. There are literally hundreds of thousands of digital process control
computers installed worldwide [18,19]. Whatever definition of mechatronics one chooses to adopt, it is
evident that modern mechatronics involves computation as the central element. In fact, the incorporation
of the microprocessor to precisely modulate mechanical power and to adapt to changes in environment
are the essence of modern mechatronics and smart products.

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