in the EC and DC subsystems. The soft tasks in the engine control part are related to

the adjustment of the throttle valve for improving the fuel consumption efficiency.

For the display control part, the utility of soft tasks is a measure of the time$-$accuracy

of the displayed data, that is$,$ how soon the information on the dashboard is updated.

The parameters of the task set are presented in Table PS$1.$

Table PS$1$

a$.$ Assign priority for each task based on Rate Monotonic Analysis $($RMA$).$

$[2$ marks$]$

b$.$ Based on the system design sketch a timeline $($from time $0$ to $120ms)$ show the

execution of the above tasks based on time slicing solution using the RMA

scheduling queue with $15$ milliseconds time slice based on RMA priority sequence as

identified in Question a$.$ Based on your timeline sketch, identified the task$/$s which

missed their deadline assuming deadline is equal to period.

c$.$ If the design in Question b$.$ to be executed with $10$ milliseconds time slice, does it

solve the problem of the missed task? Sketch the new timeline and discuss.

d$.$ Perform a scheduling analysis of the system based on processor utilization analysis

and the RMA priority identified in Question a$.$ From the analysis, discuss the

schedulability of the tasks. e$.$ From the analysis result in Question d$.$ discuss the possibility to add another task with

period $55$ milliseconds and execution $3$ milliseconds. If not possible, suggest a new

value of period of any task to the five tasks designed, discuss your suggestion.

marks$]$

f$.$ The scheduling designed in Question b$.$ to e$.$ assume there is no shared resources. Let

consider some of the tasks in Table PS$1$ sharing a block of memory, where Collision

Avoidance and Display Control make use of a block of shared memory. This block of

memory is protected by a semaphore. Collision Avoidance requires the block of memory

during the last $5ms$ of its execution and Display Control requires the block of memory

during the last $10ms$ of its execution. Sketch a timeline $($from time $0$ to $120ms)$ to

show the execution of the four tasks with fixed$-$priority scheduler RMA.

Sketch timeline diagrams to show the execution of the four tasks given the

initial arrival time of each task is at time $0.$ In each timeline shows the three

situations: executing, preempted and blocked, when appropriate using the

following legend.

Preempted

Blocked

marks$]$

g$.$ In your answer f$.,$ discuss at which time the priority inversion problem occur. Show

how this priority inversion problem can be solved using priority inheritance.SCSJ$4423$

$7$

PART B: PROBLEM SOLVING

$[40$ Marks$]$

Part B consists of one essay questions. Answer all the questions.

Given the following requirements for a Cruise Control with Collision Avoidance $($CCCA$)$ system design that contains the following independent software tasks and answer the following questions.

CCCA is a common and well known automotive driver assistance system. It can automatically assist the driver in maintaining the speed and keeping safe distances to other vehicles in the same lane. It consists of four main atomic control laws, as shown in Figure PS$1$:

i$)$ The "steering" law allows the driver of a vehicle to steer in the desired directions.

ii$)$ The "throttle" law allows the vehicle to accelerate or maintain a given acceleration through engine control.

iii$)$ The "brake" law allows the vehicle to decelerate.

iv$)$ The "collision avoidance" law allows the vehicle to do lane change maneuver with a severe braking to avoid collision.

The CCCA is composed of four main subsystems, namely Braking Control $($BC$),$ Engine Control $($EC$),$ Collision Avoidance $($CA$),$ and Display Control $($DC$).$ Each subsystem has one deadline that equals its period. The BC and CA subsystems are specified as hard tasks. For collision avoidance part, to completely avoid rear$-$end collision, severe braking and lane change maneuver is used. Soft tasks are identified