In this project, controlling the retraction and extension of the Airplane’s landing gear can be implemented using Finite State Machine (FSM). FSM is the most efficient algorithm which is mathematical model of computation.
Aim:
To write a program to control the retraction and extension of Airplane landing gear using Finite State Machines.
Program:
STATE DIAGRAM:
First, we are creating seven functions we want to carry out the process or controlling sets of gear under different conditions. Based on the above chart. And then we are entering this function into the array of 6 element to access the function based on the requirement. In the name of static table.
And we mentioned that as static type because we can use this anywhere in the program volatile means it values are changeable:
This step is very important we are creating the structure where we are giving the different condition where how to control the landing gears.
We are giving the name to structure as state_table.
we are creating the object named as state machine which is an array in which it contains six different types of conditional output:
In the while loop we have argument of current state.
Now argument as 0 which means current state is gear down:
#include <stdio.h>
void Initiate_State_Machine();
void GearDown();
void CheckingBeforeTakeOFF();
void RaisingGear();
void GearUp();
void CheckBeforeLanding();
void LoweringGear();
static void(*statetable[])(void)={GearDown, CheckingBeforeTakeOFF, RaisingGear, GearUp, CheckBeforeLanding, LoweringGear};
typedef enum State
{
GEAR_DOWN,
CHECKING_BEFORE_TAKEOFF,
RAISING_GEAR,
GEAR_UP,
CHECK_BEFORE_LANDING,
LOWERING_GEAR,
}State_Type;
typedef enum Switch
{
on,
off//plane is on ground
}Switch_status;
typedef enum pilot_lever
{
Raising,
falling
}pilot_lever;
typedef enum hydraulic_mechanism
{
working,
not_working
}hydraulic_mechanism;
static volatile Switch_status squat_switch;
static volatile Switch_status limit_switch;
static volatile pilot_lever pl;
static volatile hydraulic_mechanism hm;
State_Type current_state;
typedef struct
{
char* current_state_indication;
char* light;
char* direction_valve_status;
char* landing_gear_hydraulic_control;
char* Gas_Pressurized_Spring_system_status[2];
}State_Table;
static State_Table State_Machine[6]={{"GearDown","Green","Down","Enabled",{NULL,NULL}},
{"CheckingBeforeTakeOFF","Green","Down","Enabled",{NULL,NULL}},
{"RaisingGear","Red","Up","Enabled",{NULL,NULL}},
{"GearUp","Off","NULL","Disabled",{NULL,NULL}},
{"CheckBeforeLanding","Red","Down","Enabled",{NULL,NULL}},
{"LoweringGear","Green","Down","Enabled",{"Disabled","Enabled"}}
};
int main()
{
Initiate_State_Machine();
while(1)
{
statetable[current_state]();
}
}
void GearDown(void)
{
current_state=GEAR_DOWN;
printf("Enter the status of pilot's lever and squat switch");
fflush(stdout);
scanf("%d %d",&pl,&squat_switch);
if(pl==Raising && squat_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("current state:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is :%s\n", State_Machine[current_state].light);
}
else
{
GearDown();
}
}
//CheckingBeforeTakeOFF
void CheckingBeforeTakeOFF(void)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Enter the status of pilot's lever and squat switch and hydraulic mechanism:");
fflush(stdout);
scanf("%d %d",&pl,&squat_switch,&hm);
if(pl==falling&&squat_switch==off)
{
GearDown();
}
else if(pl==Raising && squat_switch==on && hm==working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
}
else if(pl==Raising && squat_switch==on && hm==not_working)
{
current_state=RAISING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
}
}
//RaisingGear
void RaisingGear(void)
{
current_state=RAISING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d %d",&pl,&limit_switch);
if(pl==falling && limit_switch==on)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_UP;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else
{
RaisingGear();
}
}
//GearUp
void GearUp(void)
{
current_state=GEAR_UP;
printf("Enter the status of pilot's lever:");
fflush(stdout);
scanf("%d",&pl);
if(pl==falling)
{
current_state=CHECK_BEFORE_LANDING;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
else
{
GearUp();
}
}
//CheckBeforeLanding
void CheckBeforeLanding(void)
{
current_state=CHECK_BEFORE_LANDING;
printf("Enter the status of pilot's lever and hydraulic mechanism status:");
fflush(stdout);
scanf("%d %d",&pl,&hm);
if(pl==falling && hm==working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
}
else if(pl==falling && hm==not_working)
{
current_state=LOWERING_GEAR;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Status of Direction valve:%s\n",State_Machine[current_state].direction_valve_status);
printf("Status of gas pressurised Spring System:%s\n",State_Machine[current_state].Gas_Pressurized_Spring_system_status);
}
else if(pl==(Raising))
{
CheckBeforeLanding();
}
}
//LoweringGear.
void LoweringGear(void)
{
current_state=LOWERING_GEAR;
printf("Enter the status of pilot's lever and limit switch:");
fflush(stdout);
scanf("%d %d",&pl,&limit_switch);
if(pl==falling && limit_switch==on)
{
current_state=CHECKING_BEFORE_TAKEOFF;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
}
else if(pl==Raising && limit_switch==off)
{
current_state=GEAR_DOWN;
printf("Current State:%s\n",State_Machine[current_state].current_state_indication);
printf("Light is:%s\n",State_Machine[current_state].light);
printf("Landing Gear Hydraulic Control:%s\n",State_Machine[current_state].landing_gear_hydraulic_control);
}
if(limit_switch==off)
{
LoweringGear();
}
}
//Initiate_State_Machine
void Initiate_State_Machine()
{
current_state==GEAR_DOWN;
printf("The Finite State Machine is Intialized and current the program is in""GearDown State & Light is:%s\n",State_Machine[current_state].light);
}
Output:
e Finite State Machine is Intialized and current the program is inGearDown State & Light is:Green
Enter the status of pilot's lever and squat switch0 0
current state:CheckingBeforeTakeOFF
Light is :Green
Enter the status of pilot's lever and squat switch and hydraulic mechanism:0 0
Current State:RaisingGear
Light is:Red
Status of Direction valve:Up
Enter the status of pilot's lever and limit switch:0 1
Current State:GearUp
Light is:Off
Landing Gear Hydraulic Control:Disabled
Enter the status of pilot's lever:1
Current State:CheckBeforeLanding
Light is:Red
Landing Gear Hydraulic Control:Enabled
Enter the status of pilot's lever and hydraulic mechanism status:1 0
Current State:LoweringGear
Light is:Green
Status of Direction valve:Down
Enter the status of pilot's lever and limit switch:0 1
Current State:GearDown
Light is:Green
Landing Gear Hydraulic Control:Enabled
Enter the status of pilot's lever and limit switch:1 1
Enter the status of pilot's lever and limit switch:1 0
Current State:CheckingBeforeTakeOFF
Light is:Green
