• Information technology (systems theory, automation, software engineering, artificial intelligence).

TABLE 2.1 Historical Development of Mechanical, Electrical, and Electronic Systems

FIGURE 2.1 Mechatronics: synergetic integration of different disciplines.

Some survey contributions describe the development of mechatronics; see [5–8]. An insight into general aspects are given in the journals [4,9,10]; first conference proceedings in [11–15]; and the books [16–19].

Figure 2.2 shows a general scheme of a modern mechanical process like a power producing or a power generating machine. A primary energy flows into the machine and is then either directly used for the energy consumer in the case of an energy transformer, or converted into another energy form in the case of an energy converter. The form of energy can be electrical, mechanical (potential or kinetic, hydraulic, pneumatic), chemical, or thermal. Machines are mostly characterized by a continuous or periodic (repet-itive) energy flow. For other mechanical processes, such as mechanical elements or precision mechanical devices, piecewise or intermittent energy flows are typical.

Figure 2.2 Mechanical process and information processing develop towards mechatronic systems

The energy flow is generally a product of a generalized flow and a potential (effort). Information on the state of the mechanical process can be obtained by measured generalized flows (speed, volume, or mass flow) or electrical current or potentials (force, pressure, temperature, or voltage). Together with reference variables, the measured variables are the inputs for an information flow through the digital electronics resulting in manipulated variables for the actuators or in monitored variables on a display.

The addition and integration of feedback information flow to a feedforward energy flow in a basically mechanical system is one characteristic of many mechatronic systems. This development presently influ-ences the design of mechanical systems. Mechatronic systems can be subdivided into:

• mechatronic systems

• mechatronic machines

• mechatronic vehicles

• precision mechatronics

• micro mechatronics

This shows that the integration with electronics comprises many classes of technical systems. In several cases, the mechanical part of the process is coupled with an electrical, thermal, thermodynamic, chemical, or information processing part. This holds especially true for energy converters as machines where, in addition to the mechanical energy, other kinds of energy appear. Therefore, mechatronic systems in a wider sense comprise mechanical and also non-mechanical processes. However, the mechanical part normally dominates the system.

Because an auxiliary energy is required to change the fixed properties of formerly passive mechanical systems by feedforward or feedback control, these systems are sometimes also called active mechanical systems.

2.2 Functions of Mechatronic Systems

Mechatronic systems permit many improved and new functions. This will be discussed by considering some examples.

Division of Functions between Mechanics and Electronics

For designing mechatronic systems, the interplay for the realization of functions in the mechanical and electronic part is crucial. Compared to pure mechanical realizations, the use of amplifiers and actuators with electrical auxiliary energy led to considerable simplifications in devices, as can be seen from watches, electrical typewriters, and cameras.

A further considerable simplification in the mechanics resulted from introducing microcomputers in connection with decentralized electrical drives, as can be seen from elec-tronic typewriters, sewing machines, multi-axis handling systems, and automatic gears.

The design of lightweight constructions leads to elastic systems which are weakly damped through the material. An electronic damping through position, speed, or vibration sensors and electronic feedback can be realized with the additional advantage of an adjustable damping through the algorithms. Examples are elastic drive chains of vehicles with damping algorithms in the engine electronics, elastic robots, hydraulic systems, far reaching cranes, and space constructions (with, for example, flywheels).

The addition of closed loop control for position, speed, or force not only results in a precise tracking of reference variables, but also an approximate linear behavior, even though the mechanical systems show nonlinear behavior. By omitting the constraint of linearization on the mechanical side, the effort for construction and manufacturing may be reduced. Examples are simple mechanical pneumatic and electro-mechanical actuators and flow valves with electronic control.

With the aid of freely programmable reference variable generation the adaptation of nonlinear mechan-ical systems to the operator can be improved. This is already used for the driving pedal characteristics within the engine electronics for automobiles, telemanipulation of vehicles and aircraft, in development of hydraulic actuated excavators, and electric power steering.

With an increasing number of sensors, actuators, switches, and control units, the cable and electrical connections increase such that reliability, cost, weight, and the required space are major concerns. Therefore, the development of suitable bus systems, plug systems, and redundant and reconfigurable electronic systems are challenges for the designer.