Project 2 - Implement the Code for controlling the retraction and extension of Airplane’s landing gear
AIM :
To show the implementation of retraction and extension function of Airplane’s landing gear using Finite State Machine (FSM)
GOALS:
- Controlling the direction of Valve.
- Controlling the retraction and extension of Airplane’s landing gear.
- indicating stages by different light signals.
- proper checking of gears before landing and take off.
GEARS:
Usually the airplane consists of three gears for smooth landing and take off
1.Nose gear.
2.Left gear.
3.Right gear.
SWITCHES:
Each gear consists of seperate limit switches and additionally nose gear will have a squat switch to check whether is lane is in ground or not.
HYDRALIC PUMP:
It exerting pressure to the gears to bring it down or pull it up and that pump is electrically driven.
STATE DIAGRAM: 
STATE TABLE:
PROGRAM :
INPUT:
MAIN.C
#include <stdio.h> //header
#include "sub.h"
static void (*state_table[])(void) = {Gear_Down,Checking_Before_Takeoff,Raising_Gear,Gear_Up,Checking_Before_Landing,Lowering_Gear};
int main()
{
Init_State_Machine();
while(1)
{
state_table[current_state]();
}
}
SUB.C
#include "sub.h" // header
#include <stdio.h>
void Init_State_Machine()
{
printf("\n Light_Status : %s\n",State_Machine[current_state].light_Status);
printf("\n Current State is%s\n",State_Machine[current_state].current_state);
}
void Gear_Down(void)
{
current_state = GR_DWN;
printf("\n Enter the position of Pilot's Lever and Squat Switch Status:");
fflush(stdout);
scanf("%d %d",&pilot_lever,&squat_switch);
if (pilot_lever == Rising && squat_switch == Open)
{
current_state = CHK_BFR_TKFF;
printf("\n Current State:%s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
}
else
{
printf("\n returning to gear down state");
Gear_Down();
}
}
void Checking_Before_Takeoff()
{
current_state = CHK_BFR_TKFF;
printf("\n Enter the position of Pilot's Lever,Squat Switch Status, Hydraulic Mechanism Status :");
fflush(stdout);
scanf("%d %d %d",&pilot_lever,&squat_switch,&hydraulic_mechanism);
printf("\n Wait for 2 secs\n");
if (pilot_lever == UP && squat_switch == Open )
{
fflush(stdout);
if(hydraulic_mechanism == Working)
{
current_state = RSING_GR;
printf("\n Current State: %s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
printf("Direction Value Status:%s\n\n",State_Machine[current_state].direction_value_status);
}
else if ( hydraulic_mechanism == Malfunctioning)
{
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
printf("Direction Value Status:%s\n",State_Machine[current_state].direction_value_status);
printf("Gas Pressurized Spring System Status:%s\n",State_Machine[current_state].gas_pressurized_spring_status[hydraulic_mechanism]);
}
}
else if(pilot_lever == Falling || squat_switch == Close)
{
printf("\n returning to gear down");
Gear_Down();
}
}
void Raising_Gear()
{
current_state = RSING_GR;
printf("\n Enter the Limit Switch Status, Pilot's Lever Position :");
fflush(stdout);
scanf("%d %d",&limit_switch,&pilot_lever);
printf("\nWait for 1 sec\n");
if(pilot_lever == Falling && limit_switch == Open)
{
current_state = CHK_BFR_LND;
printf ("\n Current State: %s\n",State_Machine[current_state].current_state);
printf ("Light Status:%s\n",State_Machine[current_state].light_Status);
printf ("Hydraulic Control for Landing Gear Status:%s\n",State_Machine[current_state].hydraulic_pump_control_status);
}
else if (limit_switch == Close && pilot_lever == UP)
{
current_state = GR_UP;
printf ("\n Current State: %s\n",State_Machine[current_state].current_state);
printf ("Light Status:%s\n",State_Machine[current_state].light_Status);
printf ("Hydraulic Control for Landing Gear Status:%s\n",State_Machine[current_state].hydraulic_pump_control_status);
}
else
{
printf("\n returning to raising gear ");
Raising_Gear();
}
}
void Gear_Up()
{
current_state = GR_UP;
printf("\n Enter the Pilot's Lever Position:");
fflush(stdout);
scanf("%d",&pilot_lever);
if(pilot_lever ==Falling)
{
current_state = CHK_BFR_LND;
printf("\n Current State:%s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
printf("Hydraulic Control for Landing Gear Status:%s\n",State_Machine[current_state].hydraulic_pump_control_status);
}
else
{
printf("\n returning to gear up");
Gear_Up();
}
}
void Checking_Before_Landing()
{
current_state = CHK_BFR_LND;
printf("\nCurrent State : %s\n",State_Machine[current_state].current_state);
printf("\nEnter the Pilot's Lever Position and Status of Hydraulic Mechanism:");
fflush(stdout);
scanf("%d %d",&pilot_lever,&hydraulic_mechanism);
if(pilot_lever == DOWN && hydraulic_mechanism == Working)
{
current_state = LWRNG_GR;
printf("\nCurrent State : %s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
printf("Direction Valve Status:%s\n",State_Machine[current_state].direction_value_status);
}
else if(pilot_lever == DOWN && hydraulic_mechanism == Malfunctioning)
{
current_state = LWRNG_GR;
printf("\nCurrent State : %s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
printf("Direction Valve Status:%s\n",State_Machine[current_state].direction_value_status);
printf("Gas Pressurized Spring System Status:%s\n",State_Machine[current_state].gas_pressurized_spring_status[hydraulic_mechanism]);
}
else if(pilot_lever == (UP || Rising || Falling))
{
printf("\n returning to Checking_Before_Landing ");
Checking_Before_Landing();
}
}
void Lowering_Gear()
{
current_state = LWRNG_GR;
printf("\n Enter the Limit_Switch Status,Pilot_Lever Status ::");
fflush(stdout);
scanf("%d %d",&limit_switch,&pilot_lever);
if( limit_switch == Close && pilot_lever == Rising)
{
current_state = CHK_BFR_TKFF;
printf("\n Current State: %s\n",State_Machine[current_state].current_state);
printf("Light Status:%s\n",State_Machine[current_state].light_Status);
}
else if(limit_switch == Open && pilot_lever == DOWN)
{
current_state = GR_DWN;
printf ("\n Current State: %s\n",State_Machine[current_state].current_state);
printf ("Light Status:%s\n",State_Machine[current_state].light_Status);
printf ("Hydraulic Control for Landing Gear Status:%s\n",State_Machine[current_state].hydraulic_pump_control_status);
}
else
{
printf("\n returning to lower gear");
Lowering_Gear();
}
}
SUB.H
#ifndef SUB_H_
#define SUB_H_
#include <stdio.h>
void Init_State_machine();
void Gear_Down();
void Checking_Before_Takeoff();
void Raising_Gear();
void Gear_Up();
void Checking_Before_Landing();
void Lowering_Gear();
typedef enum State
{
GR_DWN,
CHK_BFR_TKFF,
RSING_GR,
GR_UP,
CHK_BFR_LND,
LWRNG_GR
}State_Type;
typedef enum Hydraulic_Mechanism
{
Working=0,
Malfunctioning=1
}Hydraulic_Mechanism_Status;
typedef enum Switch
{
Open=0,
Close=1
}Switch_Status;
typedef enum Pilot_Lever
{
Rising=0,
Falling=1,
UP=2,
DOWN=3
}Pilot_Lever_Status;
static volatile Switch_Status squat_switch;
static volatile Switch_Status limit_switch;
static volatile Pilot_Lever_Status pilot_lever;
static volatile Hydraulic_Mechanism_Status hydraulic_mechanism;
State_Type current_state;
typedef struct
{
char* current_state;
char* light_Status;
char* direction_value_status;
char* hydraulic_pump_control_status;
char* gas_pressurized_spring_status[2];
}State_Table;
static State_Table State_Machine[6] = {
{"GearDown","Green","Down","Enabled",0,0},
{"Checking Before Take Off ","Green","Down","Enabled",0,0},
{"Raising Gear","Red","Up","Enabled",{"Disabled","Enabled"}},
{"Gear Up","Off","Null","Disabled",0,0},
{"Checking Before Landing","Red","Down","Enabled",0,0},
{"Lowering Gear","Green","Down","Enabled",{"Disabled","Enabled"}}
};
#endif /* SUB_H_ */
OUTPUT:
Light_Status : Green
Current State isGearDown
Enter the Pilot's Lever Position and Squat Switch Status:0 0
Current State:Checking Before Take Off
Light Status:Green
Enter the Pilot's Lever Position,Squat Switch Status, Hydraulic Mechanism Status :2 0 1
Wait for 2 secs
Light Status:Green
Direction Value Status:Down
Gas Pressurized Spring System Status:(null)
Enter the position of Pilot's Lever ,Squat Switch Status, Hydraulic Mechanism Status :2 0 0
Wait for 2 secs
Current State: Raising Gear
Light Status:Red
Direction Value Status:Up
Enter the Limit Switch Status, Pilot's Lever Position :1 0
Wait for 1 sec
Enter the Limit Switch Status, Pilot's Lever Position :1 2
Wait for 1 sec
Current State: Gear Up
Light Status:Off
Hydraulic Control for Landing Gear Status:Disabled
Enter the Pilot's Lever Position:1
Current State:Checking Before Landing
Light Status:Red
Hydraulic Control for Landing Gear Status:Enabled
Current State : Checking Before Landing
Enter the position of Pilot's Lever and Status of Hydraulic Mechanism:3 0
Current State : Lowering Gear
Light Status:Green
Direction Valve Status:Down
Enter the Limit_Switch Status,Pilot_Lever Status ::0 3
Current State: GearDown
Light Status:Green
IMAGE FOR REFERENCE :
RESULT :
Using fsm the c program for retraction and extension of Airplane’s landing gear using the switch and gear states of Airplane was generated successfully and acquired the expected results.