April 2008

Factory Automation

Intelligent systems in all walks of life

Mechatronic advances will benefit medicine, sensing, robotics, manufacturing, space technology, and transportation

FAST FORWARD

  • The electronic ignition system was one of the first mechatronic systems.
  • The divide between classical control and modern control narrowed with the advent of robust control theory.
  • The microprocessor is the heart of modern mechatronics and smart products.
 
By Ellen Fussell Policastro

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," augmenting the bumper and structural members to protect occupants in case of accidents.

Seat belts, introduced in the early 1960s, were for improving occupant safety and actuated completely mechanically. The driver or one of several mechanical control systems controlled all the engine systems.
For instance, before the introduction of sensors and microcontrollers, a mechanical distributor selected the specific spark plug to fire when the fuel-air mixture was compressed just so.

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, for increased fuel efficiency, there existed an optimal time when the fuel should ignite.

The timing depends on load, speed, and other measurable quantities. The electronic ignition system was one of the first mechatronic systems to go 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 and directly controlled the firings utilizing a microprocessor.

Complex and highly accurate

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 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 the 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 satellite mass while providing accurate control encouraged advancements in the important field of optimal control. Time domain methods and theories of optimal control matched well with the increasing availability of high-speed computers and new programming languages.

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.
Yasakawa Electric introduced the term mechatronics in 1969 to represent such systems. Yasakawa got the trademark in 1972, but after widespread usage of the term, released its trademark rights in 1982.

Initially, mechatronics referred to systems with only mechanical systems and electrical components-no computation was involved. Examples include the automatic sliding door, vending machines, and garage door openers.

In the late 1970s, the Japan Society for the Promotion of Machine Industry classified mechatronic products into four categories:

Class 1: Primarily mechanical products with electronics incorporated to enhance functionality. Examples include numerically controlled machine tool and variable speed drives in manufacturing machines.

Class 2: 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.

Class 3: Systems that retain the functionality of the traditional mechanical system, but the internal mechanisms are now made of electronics. An example is the digital watch.

Class 4: Products designed with mechanical and electronic technologies through synergistic integration. Examples include photocopiers, intelligent washers and dryers, rice cookers, and automatic ovens.

factory 1

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 1 products used servo technology, power electronics, and control theory. Class 2 products used the availability of early computational and memory devices and custom circuit design capabilities. Class products relied heavily on the microprocessor and integrated circuits to replace mechanical systems.

Finally, class 4 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 narrowed significantly in the 1980s with the advent of robust control theory. These days everyone agrees 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.

The incorporation of the microprocessor to precisely modulate mechanical power and to adapt to changes in environment is the essence of modern mechatronics and smart products.

Novel products, smart features

Mechatronics has become a necessity for product differentiation in automobiles.

Since the basics of internal combustion worked out almost a century ago, differences in engine design among the various automobiles are no longer useful as a product differentiator.

In the 1970s, the Japanese automakers succeeded in establishing a foothold in the U.S. market by offering unsurpassed quality and fuel-efficient small cars. The quality of the vehicle was the product differentiator through the 1980s.

In the 1990s, consumers came to expect quality and reliability in automobiles from all manufacturers. Today, mechatronic features have become the product differentiator in these traditional mechanical systems.

Added acceleration to this comes from a higher performance/price ratio in electronics, market demand for innovative products with smart features, and the drive to reduce cost of manufacturing of existing products through redesign incorporating mechatronics elements.

New applications of mechatronic systems in the automotive world include semi-autonomous to fully autonomous automobiles, safety enhancements, emission reduction, and other features including intelligent cruise control, and brake-by-wire systems eliminating the hydraulics.

Another significant growth area that would benefit from a mechatronics design approach is wireless networking of automobiles to ground stations and vehicle-to-vehicle communication.

Telematics, which combines audio, hands-free cell phone, navigation, Internet connectivity, e-mail, and voice recognition, is perhaps the largest potential automotive growth area. In fact, the use of electronics in automobiles will probably increase significantly over the next few years.

factory 2 

Human-friendly machines

In the future, growth in mechatronic systems will piggyback on the growth in the constituent areas. Advancements in traditional disciplines fuel the growth of mechatronics systems by providing enabling technologies. For example, the invention of the microprocessor had a profound effect on the redesign of mechanical systems and design of new mechatronics systems.

Expect continued advancements in cost effective microprocessors and microcontrollers, sensor and actuator development enabled by advancements in applications of MEMS, adaptive control methodologies and real-time programming methods, networking and wireless technologies, mature CAE technologies for advanced system modeling, virtual prototyping, and testing. The continued rapid development in these areas will only accelerate the pace of smart product development.

The Internet is a technology that, when utilized in combination with wireless technology, may also lead to new mechatronic products.

While developments in automotives provide vivid examples of mechatronics development, there are numerous examples of intelligent system in all lifestyles, including smart home appliances such as dishwashers, vacuum cleaners, microwaves, and wireless network enabled devices.

In the area of "human-friendly machines," we can expect advances in robot-assisted surgery and implantable sensors and actuators. Other areas that will benefit from mechatronic advances may include robotics, manufacturing, space technology, and transportation.

The future of mechatronics is wide open.

ABOUT THE AUTHORS

Robert H. Bishop is a professor of aerospace engineering and engineering mechanics at the University of Texas at Austin. His book is The Mechatronics Handbook, CRC Press, ISA Press, 2002. M. K. Ramasubramanian (rammk@eos.ncsu.edu) is associate professor of mechanical & aerospace engineering and director of the mechatronics program at North Carolina State University in Raleigh, N.C.

 

Terminology

Hall Effect refers to the potential difference on the opposite sides of an electrical conductor through which an electric current is flowing, created by a magnetic field applied perpendicular to the current.

Hall Effect devices produce a very low signal level and thus require amplification. It was only with the development of the low cost integrated circuit that the Hall Effect sensor became suitable for mass application.

They are good for current sensing, position and motion sensing, automotive ignition and fuel injection, wheel rotation sensing, electric motor control, and others.

Numerical control or numerically controlled machine tools are machines that operate automatically using commands that their processing units receive. These machines used instructions coming off punched paper tape or punch cards.

Numerically controlled machines were first developed soon after World War II and made it possible for large quantities of the desired components to be precisely and efficiently produced (machined) in a reliable repetitive manner.

Robust control theory is a method to measure the performance changes of a control system with changing system parameters.

CAE, or computer-aided engineering, is the use of information technology for supporting engineers in tasks such as analysis, simulation, design, manufacture, planning, diagnosis, and repair.

CAE tools are very widely used in the automotive industry. In fact, their use has enabled the automakers to reduce product development cost and time.

The predictive capability of CAE tools has progressed to the point where much of the design verification takes place by using computer simulations rather than physical prototype testing.

 

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