Microcomputer Control of Thermal and Mechanical Systems

Microcomputers are having, and will have in the future, a significant impact on the technology of all fields of engineering. The applications of micro­ computers of various types that are now integrated into engineering include computers and programs for calculations, word processing, and graphics. The focus of this book is on still another objective-that of control. The forms of microcomputers used in control range from small boards dedicated to control a single device to microcomputers that oversee the operation of numerous smaller computers in a building complex or an industrial plant. The most­ dramatic growth in control applications recently has been in the microcom­ puters dedicated to control functions in automobiles, appliances, production machines, farm machines, and almost all devices where intelligent decisions are profitable. Both engineering schools and individual practicing engineers have re­ sponded in the past several years to the dramatic growth in microcomputer control applications in thermal and mechanical systems. Universities have established courses in computer control in such departments of engineering as mechanical, civil, agricultural, chemical and others. Instructors and students in these courses see a clear role in the field that complements that of the com­ puter specialist who usually has an electrical engineering or computer science background. The nonEE or nonCS person should first and foremost be com­ petent in the mechanical or thermal system being controlled. The objectives of extending familiarity into the computer controller are (1) to learn the char­ acteristics, limitations, and capabilit.

1 Microcomputer Control.- 1-1 The Penetration of Microprocessors into Engineering Fields.- 1-2 The Path by which Microcomputer Control Has Grown.- 1-3 Chemical and Process Industries.- 1-4 Environmental Control of Buildings.- 1-5 Automobiles.- 1-6 Home Appliances.- 1-7 Computer Control in Manufacturing.- 1-8 Electric Power Generation and Regulation.- 1-9 Agricultural Applications of Computer Control.- 1-10 What the Engineer Who Applies Computers Needs to Know.- References.- 2 DC Circuits and Power Supplies.- 2-1 Understanding Circuits.- 2-2 Kirchhoff’s Laws.- 2-3 Thévenin Equivalent.- 2-4 Norton Equivalent.- 2-5 RC Circuits.- 2-6 Resistors.- 2-7 Diodes.- 2-8 Rectifying Circuit.- 2-9 Voltage Ripple.- 2-10 Commercial Power Supplies.- 2-11 Voltage Regulators.- Problems.- 3 Operational Amplifiers.- 3-1 Application of Operational Amplifiers.- 3-2 Basic Characteristic of the Op Amp.- 3-3 Comparator.- 3-4 Inverting Amplifier.- 3-5 Choice of Resistances.- 3-6 Non-inverting Op Amp.- 3-7 Buffer or Follower Amp.- 3-8 Signal Conditioning.- 3-9 Summing and Multiplying Amplifier.- 3-10 Generalized Circuit for an Op Amp.- 3-11 Integrator.- 3-12 Pin Diagram of 741 Op Amp.- 3-13 Limitations and Ratings of the Op Amp.- General References.- Problems.- 4 Transistors.- 4-1 Impact of the Transistor.- 4-2 Symbols and Terminology.- 4-3 Current Characteristics.- 4-4 Bipolar-Junction and Field-Effect Transistors.- 4-5 Voltages at the Transistor Terminals.- 4-6 Voltage Amplifier.- 4-7 Transistor as a Switch, and Saturating the Transistor.- 4-8 Common Emitter and Common Collector Circuits.- 4-9 Zener Diode.- 4-10 Constant-Current Source.- 4-11 Designing a Constant-Current Source.- 4-12 Operating Limits of a Transistor.- 4-13 Transistor Packages.- References.- Problems.- 5 Transducers.- 5-1 Importance of Good Instrumentation.- 5-2 Thermocouples.- 5-3 Thermocouple Reference Junction.- 5-4 Metal and Thermistor Resist ance-Temperature Devices.- 5-5 Series Circuit.- 5-6 Bridge Circuits.- 5-7 Amplification of a Bridge Output.- 5-8 RTD Circuits Supplied with Constant Current.- 5-9 Temperature-Dependent Integrated Circuits.- 5-10 Application of Sensors—Liquid Temperature.- 5-11 Application of Sensors—Temperature of Air and Other Gases.- 5-12 An Overview of Temperature Sensors and Transducers.- 5-13 Flow Rate and Velocity Measurement.- 5-14 Venturi Tubes—Liquid Flow Measurement.- 5-15 Orifice—Liquid Flow Measurement.- 5-16 Flow Measurement of a Compressible Fluid in a Venturi or Orifice.- 5-17 Pitot Tubes.- 5-18 Hot-Wire Anemometer.- 5-19 Turbine Flow Meter.- 5-20 Ultrasonic Flow Meters.- 5-21 Vortex-Shedding Flow Meters.- 5-22 Evaluation of Flow-Measuring Devices.- 5-23 Pressure Transducers.- 5-24 Evaluation of Types of Pressure Transducers.- 5-25 Force.- 5-26 Torque.- 5-27 Electric Current.- 5-28 Humidity Sensors.- 5-29 Chemical Composition.- 5-30 Liquid Level.- 5-31 Position and Motion Sensors.- 5-32 Rotative Speed.- 5-33 How to Choose Transducers.- References.- General References.- Problems.- 6 Actuators.- 6-1 Actuators for Computer Control Systems.- 6-2 Two-Position DC Electric Switch.- 6-3 Silicon-Controlled Rectifier (SCR) for DC Switching.- 6-4 Triac—Alternating Current Switching.- 6-5 Optically Isolated Switch.- 6-6 Solid-State Relays.- 6-7 Electric-Motor Actuators.- 6-8 Magnetic Operator.- 6-9 Hydraulic Actuator.- 6-10 Pneumatic Valve and Damper Operators.- 6-11 Electric-to-Pneumatic Transducer.- 6-12 Stepping Motors.- 6-13 Performance of Stepping Motors.- References.- Problems.- 7 Binary Numbers and Digital Electronics.- 7-1 Transition to Digital Electronics.- 7-2 Binary Numbers.- 7-3 Conversion between Binary and Decimal Numbers.- 7-4 Addition of Binary Numbers.- 7-5 Basic Logic Operations.- 7-6 OR Gate.- 7-7 AND Gate.- 7-8 Inverter.- 7-9 NOT-OR (NOR) Gate.- 7-10 NOT-AND (NAND) Gate.- 7-11 Exclusive-OR (XOR) Gate.- 7-12 Combining and Cascading Gates.- 7-13 De Morgan’s Laws.- 7-14 Gate Chips.- 7-15 Ladder Diagrams for Conditional and Sequential Control.- 7-16 Ladder Diagram Using Gates.- 7-17 Sequential Logic Circuits.- 7-18 Binary Addition with Gates.- 7-19 Pull-Up Resistor.- 7-20 Three Classes of Outputs Found on Inverters and Buffer Gates.- 7-21 Debounced Switch.- 7-22 Clocks and Oscillators.- 7-23 Flip-Flops.- 7-24 Divide-By Counters.- 7-25 Schmitt Trigger.- 7-26 Monostable Multivibrator.- 7-27 Low-Frequency Pulses.- 7-28 Latches.- 7-29 Comparators.- 7-30 Analog Switches—Field-Effect Transistors.- 7-31 Binary-Coded Decimal (BCD).- 7-32 Seven-Segment LEDs.- 7-33 Summary.- General References.- Problems.- 8 Conversion Between Digital and Analog.- 8-1 Elements of a Microcomputer Controller.- 8-2 A Simple DAC.- 8-3 DAC Using R-2R Ladder Circuit.- 8-4 The 1408 DAC.- 8-5 Applying the 1408 DAC.- 8-6 Multiplexers.- 8-7 Fidelity of Voltage Transmission Through a MUX.- 8-8 Sample-and-Hold Circuits.- 8-9 Operating Sequence with Multichannel Control.- 8-10 Where Analog-to-Digital Conversion Is Needed.- 8-11 Internal Functions of One Class of ADCs.- 8-12 More Complete Description of the Internal Functions of an ADC.- 8-13 Staircase and Successive Approximation Search Routines and Dual-Slope Integration.- 8-14 Pin Diagram of an 8-Bit ADC.- 8-15 Characteristics of the ADC 0800.- 8-16 Analog-to-Digital Conversion Using a DAC in Combination with Software.- 8-17 Choosing the ADC.- Problems.- 9 Memories.- 9-1 Function and Types of Memories.- 9-2 ROMs.- 9-3 EPROMs.- 9-4 RAMs.- 9-5 The MCM6810 RAM.- 9-6 Four-Bit RAMs—the MCM2114.- 9-7 Dynamic RAMs.- 9-8 EEPROMs.- 9-9 Memories on the Microcomputer.- General References.- Problems.- 10 Binary Arithmetic.- 10-1 The Eight-Bit Microcomputer.- 10-2 Two’s Complement Arithmetic—Subtraction.- 10-3 Multiplication.- 10-4 Hexadecimal System.- 10-5 Labeling Conventions.- 10-6 Signed and Unsigned Numbers.- 10-7 Unsigned Numbers—The Carry Flag.- 10-8 Signed Numbers—Two’s Complement Overflow.- 10-9 Status Registers on Microprocessors.- References.- Problems.- 11 Programming a Microprocessor.- 11-1 A Generic Microprocessor.- 11-2 Data and Address Buses in a Generic Microcomputer.- 11-3 The Accumulator with its Arithmetic, Logic, and Transfer Operations.- 11-4 The Fetch-Decode-Execute Sequence.- 11-5 Preliminary Instruction Set.- 11-6 Program Counter.- 11-7 Status Register and Jumps.- 11-8 Another Accumulator—Incrementing and Decrementing.- 11-9 Additional Addressing Modes.- 11-10 The Index Register and the Use of Register Addressing.- 11-11 Subroutines and the Stack.- 11-12 The Intel 8080/8085 Microprocessor.- 11-13 Loading Into and Storing From the Accumulator.- 11-14 Forms of Addressing on the 8080/8085.- 11-15 Flag Register.- 11-16 Subroutines.- 11-17 The 8080/8085 Programming Guide.- 11-18 The Motorola 6800 Family.- 11-19 Registers in the 6800 Microprocessor.- 11-20 The Instruction Set of the 6800.- 11-21 Condition Codes.- 11-22 Forms of Addressing.- 11-23 Branches—Relative Addressing.- 11-24 Index Register—Indexed Addressing.- 11-25 Loops.- 11-26 Stack Pointer.- 11-27 Subroutines.- 11-28 The 6800 Microprocessor Programming Guide.- 11-29 Summary.- References.- Problems.- 12 Assembly Language Programming.- 12-1 Machine Language and Assembly Language.- 12-2 An Overview of the Assembly Process.- 12-3 Major Components of the Program.- 12-4 Assembly Language Statements.- 12-5 Assembler Directives.- 12-6 The Location Counter.- 12-7 Using Assembler Labels and Symbols.- 12-8 Relocating Assemblers and Loaders.- 12-9 The Operation of an Assembler.- References.- Problems.- 13 The Structure of an Elementary Microcomputer.- 13-1 Definition of an Elementary Microcomputer.- 13-2 The Bus Structure.- 13-3 Flow of Information on the Buses During Execution of a Program.- 13-4 The Intel 8080 Microprocessor.- 13-5 Structure of the SDK-85 System Design Kit.- 13-6 Memory Map of the SDK-85.- 13-7 The Motorola 6802 Microprocessor.- 13-8 Structure of the MEK6802D5 Evaluation Kit.- 13-9 Memory Map of the D5 Evaluation Kit.- 13-10 Common Features of an Elementary Microcomputer.- References.- Problems.- 14 Parallel Input/Output and Interrupts.- 14-1 Parallel Input/Output.- 14-2 A Generic Parallel I/O Chip.- 14-3 Processing Interrupts.- 14-4 The Motorola Peripheral Interface Adapter (PIA).- 14-5 Registers in the PIA.- 14-6 Preparing the PIA to Send and Receive Data.- 14-7 Interrupt from a Peripheral—An Overview.- 14-8 The Control Register and the Control Lines.- 14-9 Setting the Microprocessor to Receive an Interrupt.- 14-10 Structure of an Interruptible Program.- 14-11 User I/O Socket.- 14-12 Intel 8155/8156 RAM with I/O.- 14-13 Intel 8212 I/O Chip.- 14-14 Rudimentary Control Capability Now Available.- Problems.- 15 Serial Input/Output and Modems.- 15-1 Serial Data Transmission.- 15-2 Mark, Space, and Baud Rate.- 15-3 Synchronous and Asynchronous Communication.- 15-4 Parity.- 15-5 Shift Register.- 15-6 A Generic Universal Asynchronous Receiver/ Transmitter (UART).- 15-7 The MC6850 Asynchronous Receiver/Transmitter (ACIA).- 15-8 Registers in the ACIA.- 15-9 The Control Register.- 15-10 The Status Register.- 15-11 Transmitting and Receiving with the ACIA.- 15-12 The Intel 8251A Programmable Communication Interface.- 15-13 The Control and Status Register on the 8251A.- 15-14 Communicating Using RS-232-C and Modems.- 15-15 RS-232-C Interface.- 15-16 Level Conversion Between RS-232-C and TTL.- 15-17 Communicating Between Two Elementary Microcomputers Using RS-232-C.- 15-18 Transmission over Telephone Lines Using Modems.- 15-19 Dial-Up Modems.- 15-20 ASCII Characters.- 15-21 One-on-One Communication.- References.- Problems.- 16 Dynamic Behavior of Systems.- 16-1 Returning to the Thermal and Mechanical System.- 16-2 On/Off Controls.- 16-3 Make/Break Sensor with On/Off Actuator.- 16-4 Analog Sensor with On/Off Actuator.- 16-5 Modulating Control Strategies.- 16-6 Proportional Control.- 16-7 Proportional-Integral Control.- 16-8 Proportional-Integral-Derivative (PID) Control.- 16-9 Dynamic Analysis.- 16-10 Laplace Transforms.- 16-11 Inverting a Transform.- 16-12 Transforms of Derivatives.- 16-13 Solving Differential Equations by Means of Laplace Transforms.- 16-14 Transfer Functions.- 16-15 Feedback Loops.- 16-16 Stability Criteria for a Feedback Control Loop.- 16-17 A Proportional Controller Regulating the Pressure in an Air-Supply System.- 16-18 Response of a Proportional Air-Pressure Controller to a Disturbance in Air-Flow Rate.- 16-19 The Integral Mode of Control.- 16-20 The Proportional-Integral (PI) Mode of Control.- References.- Problems.- 17 The Computer and Its Sampling Processes.- 17-1 Unique Features of Computer Control.- 17-2 Numerical Simulation.- 17-3 Sampled Data.- 17-4 Responses to Sampled Values.- 17-5 The z-Transform.- 17-6 Response to a Series of Impulses.- 17-7 The Zero-Order Hold (ZOH).- 17-8 Inverting a z-Transform.- 17-9 Cascading z-Transforms and Transforms of a Feedback Loop.- 17-10 How a z-Transform Can Indicate Stability of a Control Loop.- 17-11 Proportional Control.- 17-12 Proportional-Integral Control.- 17-13 Forms of Actuator Signals.- 17-14 Non-linearities—Dead Time.- 17-15 Non-linearities—Hysteresis.- 17-16 Summary.- References.- Problems.- 18 Field Application of Microcomputer Controllers.- 18-1 Applying Microcomputer Controllers to Field Processes.- 18-2 Practical Control Algorithms.- 18-3 Incremental PI Control Algorithm.- 18-4 Position PI Control Algorithm.- 18-5 Criteria for Tuning.- 18-6 Manual Control Test.- 18-7 Trial-and-Error Tuning.- 18-8 Closed-Loop Tuning.- 18-9 Open-Loop Tuning.- 18-10 Hysteresis Compensation.- 18-11 Summary.- References.- Problems.