Review and summary

REVIEW AND SUMMARY 

• At the beginning of this chapter, the technology of fluidics and how fluidics is used to control fluid power systems have been discussed.

• Fluidics is the technology that utilizes fluid flow phenomena in components and circuits to perform a wide variety of control functions.

• The fluidic devices control fluid power force components and fluid power master control components by the same media with which the force components are operated—either gases or liquids.

• 'Coanda effect': When a stream of fluid meets other stream, the effect is to change its direction of flow and effect is the fluid sticks to the well.

• Basic fluidic devices are :

1. Basic bistable flip-flop,

2. Flip-flop with start-up preference,

3. SRT flip-flop,

4. OR/NOR gate,

5. AND/NAND gate, and

6. Exclusive OR gate.

• The bistable flip-flop device is normally used as a memory device. A flip-flop with start-up preference is used in applications where a specific output is required when the power supply is first turned ON and all controls are OFF. SRT flip-flop is an acronym for SET-RESET-TRIGGER flip-flop. The monostable devices—OR/NOR and AND/NAND gates-are required to perform monostable function which is analogous to spring return function.

• Types of fluid sensors are :

1. Back-pressure sensor,

2. Cone-jet proximity sensor,

3. Interruptible-jet sensor, and

4. Contact sensing.

• The construction, operation and symbol of the various fluidic devices and fluid sensors were presented in this chapter. 

• Moving-part logic (MPL) devices are miniature valve-type devices that perform switching operations in fluid logic systems by the action of internal moving parts.

• A programmable logic controller (PLC) can be defined as an digital electronie device that uses a programmable memory to store instructions and to implement functions such as logic, sequencing, timing, counting, and arithmetic in order to control machines and processes.

• Major units of a PLC are :

1. Gentral processing unit (CPU),

2. Programmer/monitor (PM), and

3. Input/output module (I/O).

• At the end of the chapter, a brief note on PLC applications in fluid power control has been presented.

• The basic form of programming commonly used with PLCs is ladder programming.

KEY TERMS ONE SHOULD REMEMBER

Fluidics

Coanda effect

Wall-attachment effect

Fluidic devices

Bistable flip-flop 

Start-up preference flip-flop

SRT flip-flop 

OR/NOR gate 

AND/NAND gate

Exclusive OR gate

Truth table

Monostable devices

Boolean algebra 

Fluid sensors

Back-pressure sensor 

Cone-jet proximity sensor 

Interruptible-jet sensor 

Contact sensing 

Pneumatic logic circuits 

Fluidic sequencing control

Moving-part logic (MPL) devices 

Programmable logic controller (PLC) 

Electromechanical relays 

Central processing unit (CPU) 

Programmer/Monitor (PM) 

Input/Output module (I/O) 

Ladder programming PLC 

ladder symbols 

PLC ladder 

logic diagrams