Understanding Smart Sensors - Nomads.usp

Control Techniques 151Table 7.1Types of Vehicle Control Systems (After: [2])System Knowledge/Skill Application ExampleOpen loopBasic mechanics, physics; Fuel indicatormechanical-electrical interfaceClosed loop Basic feedback theory Automatic temperature controlComplex processor Multiple function;Engine managementsequential processesInteractive system Interactive system controls; Antilock brakes and traction controlcontrol analysis CAETotal vehicle control Architecture tools; failure modemanagement; communicationtheory; structured softwareIntelligent vehicleGlobalHigher level languages;simulatorsExternal environment inputsTable 7.2Comparison of Open- and Closed-Loop SystemsParameter Open-Loop System Closed-Loop SystemLatchup Possible Not possibleMechanical fatigue Possible MinimizedLinearity Medium HighDynamic range Narrow WideFrequency response Set by damping Set by electronicsSensitivity Set by mechanical design Set by electronicsthe percentage of full scale that corresponds to the full operating range of thecontrol element [4].Integral control is a function of time, unlike proportional control, whichhas no time associated with it. Integral control responds to the continued existenceof a deviation such as an offset. The combination of proportional andintegral actions results in a change at a steady rate for each value of deviation.The integral rate is usually measured in repeats per minute.