Booch Block diagram for cruise control | Website for Students | VTU NOTES | QUESTION PAPERS | NEWS...

Booch Block diagram for cruise control

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Cruise control• System on/off- to maintain car speed• Engine on/off- to control car engine (cruise control system is only active if

the engine is on. • Pulse from wheel- to send pulse for revolution of the wheel• Accelerator- to indicate how far the acceleration has been pressed• Brake-reverts to manual control when applied.• Increase/Decrease speed- • Resume speed- To resume last maintained speed• Clock- Timing pulse every millisecond• Throttle- Digital value for the engine throttle setting



Cruise control- problem statementProblem definition

• Whenever the system is active, determine the desired speed, and control the engine throttle setting to maintain that speed.

• i.e– The target speed must be engine throttle setting. – To control the current speed of the vehicle.



Booch’s OOD for cruise control

Driver

Engine

Brake

Clock

Current speed

Desired speed

wheel

Accelerator

Throttle



Object view of cruise control

• Booch organizes an oo decomposition of the system.• The elements of the decomposition correspond to important

quantities and physical entities in the system.• Blobs represent objects, and the lines represent

dependencies among objects.



Process control view of cruise control

• Computational elements – Process definition-• Process receives throttle setting and turns the car’s wheels.

– Control algorithm• Models the current speed from wheel pulses, compares it to

the desired speed and changes the throttle setting. • Clock input is needed to determine current speed from the

intervals between wheel pulses.



• Data elements– Controlled variable –

• Current speed of the vehicle

– Manipulated variable• Throttle setting

– Set point• Desired speed is set and modified by the accelerator input and the

increase/decrease speed input.

– Sensor for controlled variable• Current state is the current speed, which is modeled on data from

a sensor that delivers wheel pulses using clock.



Control Architecture for cruise control



Working..

• The controller receives two I/P from set point computation– The active/inactive toggle- whether the controller is in charge of the

throttle.– The desired speed-needs to be valid when the vehicle is under

automatic control

• The controller is continuously evaluating function that matches the dataflow character of t he inputs and outputs.



• Additional inputs to cruise control problem– State: System on/off engine on/off, accelerator , brake.– Events: Wheel pulses, increase/decrease speed, resume clock.







Analysis and Discussion

• Correspondence between architecture and problem

• Methodological implications • First, it should help the designer decide when the architecture is

appropriate• 2nd should help the designer identify elements of the design and

their interactions.• 3rd help to identify critical design decisions.



• Methodology should provide modifications.• Add a digital speedometer.• Use separate micro computers for current/desired speed and

throttle.



• Performance: system response to control– On/off control– Proportional control– Proportional plus reset control

• Correctness • When software controls a physical system ,

correctness and safety are critically important.



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