Page 22 - The Mechatronics Handbook

The enabling technologies for each mechatronic product class illustrate the progression of electrome-
chanical products in stride with developments in control theory, computation technologies, and micro-
processors. 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.

1.4 The Development of the Automobile
as a Mechatronic System

The evolution of modern mechatronics can be illustrated with the example of the automobile. Until the
1960s, the radio was the only significant electronics in an automobile. All other functions were entirely
mechanical or electrical, such as the starter motor and the battery charging systems. There were no
“intelligent safety systems,” except augmenting the bumper and structural members to protect occupants
in case of accidents. Seat belts, introduced in the early 1960s, were aimed at improving occupant safety
and were completely mechanically actuated. All engine systems were controlled by the driver and/or other
mechanical control systems. For instance, before the introduction of sensors and microcontrollers, a
mechanical distributor was used to select the specific spark plug to fire when the fuel–air mixture was
compressed. The timing of the ignition was the control variable. The mechanically controlled combustion
process was not optimal in terms of fuel efficiency. Modeling of the combustion process showed that,
for increased fuel efficiency, there existed an optimal time when the fuel should be ignited. The timing
depends on load, speed, and other measurable quantities. The electronic ignition system was one of the
first mechatronic systems to be introduced in the automobile in the late 1970s. The electronic ignition
system consists of a crankshaft position sensor, camshaft position sensor, airflow rate, throttle position,
rate of throttle position change sensors, and a dedicated microcontroller determining the timing of the
spark plug firings. Early implementations involved only a Hall effect sensor to sense the position of the
rotor in the distributor accurately. Subsequent implementations eliminated the distributor completely
and directly controlled the firings utilizing a microprocessor.
The Antilock Brake System (ABS) was also introduced in the late 1970s in automobiles [20]. The ABS
works by sensing lockup of any of the wheels and then modulating the hydraulic pressure as needed to
minimize or eliminate sliding. The Traction Control System (TCS) was introduced in automobiles in the
mid-1990s. The TCS works by sensing slippage during acceleration and then modulating the power to
the slipping wheel. This process ensures that the vehicle is accelerating at the maximum possible rate
under given road and vehicle conditions. The Vehicle Dynamics Control (VDC) system was introduced
in automobiles in the late 1990s. The VDC works similar to the TCS with the addition of a yaw rate
sensor and a lateral accelerometer. The driver intention is determined by the steering wheel position and
then compared with the actual direction of motion. The TCS system is then activated to control the

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