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
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Cruise control- problem statement
Problem 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.
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Booch’s OOD for cruise control
wheel
Clock
Driver
Current
speed
Brake
Desired
speed
Throttle
Engine
Accelerator
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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.
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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.
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• 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.
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Control Architecture for cruise control
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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.
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• Additional inputs to cruise control problem
– State: System on/off engine on/off, accelerator , brake.
– Events: Wheel pulses, increase/decrease speed, resume clock.
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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.
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• Methodology should provide modifications.
• Add a digital speedometer.
• Use separate micro computers for current/desired speed and
throttle.
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• 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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Three vignettes in mixed style
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An interpreter using different idioms for
the components
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A blackboard globally recast as an
interpreter
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