- •What is Mechatronics?
- •1.4 The Development of the Automobile as a Mechatronic System
- •Vehicles. (Adapted from Modern Control Systems, 9th ed., r. C. Dorf and r. H. Bishop, Prentice-Hall, 2001. Used with permission.)
- •1.5 What is Mechatronics? And What’s Next?
- •Information technology (systems theory, automation, software engineering, artificial intelligence).
- •Figure 2.2 Mechanical process and information processing develop towards mechatronic systems
- •2.2 Functions of Mechatronic Systems
- •Improvement of Operating Properties
- •Table 2.2 Properties of Conventional and Mechatronic Design Systems
- •2.3 Ways of Integration
- •Figure 2.4 Ways of integration within mechatronic systems.
- •2.4 Information Processing Systems (Basic Architecture and hw/sw Trade-offs)
- •Figure 2.5 Advanced intelligent automatic system with multi-control levels, knowledge base, inference mechanisms, and interfaces.
- •2.5 Concurrent Design Procedure for Mechatronic Systems
- •• An Automotive Example
- •• Software Design
- •3.2 Input Signals of a Mechatronic System
- •3.3 Output Signals of a Mechatronic System
- •3.4 Signal Conditioning
- •3.5 Microprocessor Control
- •3.6 Microprocessor Numerical Control
- •3.7 Microprocessor Input–Output Control
- •Input and Output Transmission
- •3.8 Software Control
- •4.4 Microprocessors and Microcontrollers
- •4.5 Programmable Logic Controllers
- •5.2 Microactuators
- •5.3 Microsensors
- •5.4 Nanomachines
- •6.2 Nano-, Micro-, and Mini-Scale Electromechanical Systems and Mechatronic Curriculum
- •6.3 Mechatronics and Modern Engineering
- •Integrated multidisciplinary features approach quickly, as documented in Fig. 6.2. The mechatronic paradigm, which integrates electrical, mechanical, and computer engineering, takes place.
- •6.4 Design of Mechatronic Systems
- •6.5 Mechatronic System Components
- •6.7 Mechatronic Curriculum
- •Integrating electromagnetics, electromechanics, power electronics, iCs, and control;
- •6.8 Introductory Mechatronic Course
- •6.9 Books in Mechatronics
- •6.10 Mechatronic Curriculum Developments
- •Introduction to Mechatronics,
- •7.3 Rigid Body Models
3.6 Microprocessor Numerical Control
Fixed-Point Mathematics
The microprocessors in an embedded controller are generally quite small in comparison to a personal computer or computer workstation. Adding processing power in the form of a floating-point processor and additional RAM or ROM is not always an option. This means that sometimes the complex mathematical
functions needed in a control system are not available. However, sometimes the values being sensed and computed, though real numbers, are of a reasonable range. Because of this situation there exists a special type of arithmetic whereby microcontrollers use integers in place of floating-point numbers to compute non-whole number (pseudo real) values.
There are several forms of fixed-point mathematics currently in use. The simplest form is based upon powers of 2, just like normal integers in binary. However, a virtual binary point is inserted into the integer to allow an approximation of real values to be stored as integers. A standard 8-bit unsigned integer is shown below along with its equivalent decimal value.
0001 0100 = (1 * 24) + (1 * 22) = (1 * 16) + (1 * 4) = 20
Suppose a virtual binary point is inserted between the two nibbles in the byte. There are now four bits left of the binary point with the standard positive powers of 2, and 4 bits right of the binary point with negative powers of 2. The same number now represents a real number in decimal.
0001 0100 = (1 * 20) + (1 * 2 -2) = (1 * 1) + (1 * 0.25) = 1.25
Obviously this method has shortcomings. The resolution of any fixed point number is limited to the power of 2 attached to the least significant bit on the right of the number, in this case 2 -4 or 1/16 or 0.0625. Rounding is sometimes necessary. There is also a tradeoff in complexity, as the position of this virtual binary point must constantly be maintained when performing calculations. The savings in memory usage and processing time, however, often overcome these tradeoffs; so fixed-point mathematics can be very useful.
Calibrations
The area of calibrating a system can sometimes take on an importance not foreseen when designing a mechatronic system. The use of calibrations, numerical and logical values kept in EEPROM or ROM, allow flexibility in system tuning and implementation. For example, if different microprocessor crystal speeds may be used in a mechatronic system, but real-time values are needed, a stored calibration constant of clock cycles per microsecond will allow this calculation to be affected. Thus, calibrations are often used as a gain, the value multiplied by some input in order to produce a scaled output.
Also, as mentioned above, calibrations are often used in the testing of a mechatronic system in order to change the “feel” of the product. A transmission control unit can use a set of calibrations on engine RPM, engine load, and vehicle speed to determine when to shift gears. This is often done with hysteresis, as the shift points moving from second gear to third gear as from third gear to second gear may differ.