Cruise Control Speed Setpoint

Using a statechart, define the behavior for a device that specifies the desired speed setpoint for an automotive cruise controller. There is a second device that performs the actual speed control. There are also several buttons on the steering column that the driver uses to control the cruise control. The following is the interface to the cruise speed setpoint controller.

	Signal	Use	Direction
User interface to the cruise control system	ON/OFF	Turn cruise control on and off	Button input to setpoint controller. When button is closed, the cruise control is on. When button is open, the cruise control is off.
	SET	Set cruise speed setpoint to the current speed	Button input to setpoint controller. When button is pressed, set the cruise speed setpoint to the current speed.
	CANCEL	Stop controlling speed	Button input to setpoint controller. When button is pressed, stop controlling the speed, i.e. ACTIVE is off.
	RESUME	Resume controlling speed at the last cruise speed setpoint	Button input to setpoint controller. When button is pressed, start controlling the speed, i.e. ACTIVE is on.
	ACCELERATE	Increase the setpoint speed by 1 mile/hour.	Button input to setpoint controller. While the button is pressed, increase the speed setpoint by 1 mile/hour. While button remains depressed, increase the speed setpoint by 1 mile/hour every 2 seconds.
	DECELERATE	Decrease the setpoint speed by 1 mile/hour.	Button input to setpoint controller. While the button is pressed, decrease the speed setpoint by 1 mile/hour. While button remains depressed, decrease the speed setpoint by 1 mile/hour every 2 seconds.
Interface between the setpoint controller and the speed controller	ACTIVE	Turn speed controller on and off	Output signal to speed controller. While ACTIVE is on the speed controller will maintain the car's speed at the SETPOINT value.
	SETPOINT	The desired speed	Output signal to speed controller. If ACTIVE is on, this signal indicates the setpoint speed that the speed controller attempts to maintain.
	CURRENT	The current speed	Input signal to the setpoint controller. This signal indicates the car's current speed to the setpoint controller.

Notes:

It is physically not possible to press multiple buttons at the same time.
The actual control of the automobile speed is beyond the scope of this controller. You are specifying the behavior for a device that turns the speed controller on and off, and indicates the desired cruise speed.
Assume that an input scanner exists to read the button inputs, and can generate events for button depression, button release, or events repeated at regular intervals to indicate unchanged button state, i.e. the button continues to be pressed/closed or open/released.

For this exercise, you will start working with the Rhapsody tool. You can find it in Start menu -> All Programs -> IBM Rational -> IBM Rational Rhapsody for C++.

Create a new project and make sure to put it in a workspace on your Z: drive instead of the default on the C: drive.
Select the Model1 Object Model Diagram. This should display a set of tools on the right side of the workarea.
Select Class and click to place a new class in the model. Give it a class name of SpeedSetpoint.
Right click on the SpeedSetpoint class and add a new statechart.
You can now define the behavior of this class using the statechart tools.

When you are done with your statechart, copy the diagram and paste it into a Word file, and place that file into the dropbox for the Cruise Control exercise.

$Id: CruiseControl.html 170 2012-12-05 06:26:27Z jrv $