// fly_by_wire.c - Airbus® A320 Flight Control Laws (Demo) // This demo simulates a simplified fly-by-wire system. // Author: Hamza Bendahmane #include <stdio.h> #include <stdlib.h> #include <stdint.h> #include <stdbool.h> #include <math.h> #include <time.h> // ---------------- Sensors ---------------- typedef struct { float pitch_angle; // Aircraft pitch angle (degrees) float roll_angle; // Aircraft roll angle (degrees) float yaw_angle; // Aircraft yaw angle (degrees) float airspeed; // Aircraft airspeed (knots) float angle_of_attack; // Angle of attack (degrees) float load_factor; // G-load (g) } Sensors; // ---------------- Pilot Inputs ---------------- typedef struct { float sidestick_pitch; // Pilot input on pitch float sidestick_roll; // Pilot input on roll float rudder; // Pilot input on rudder } PilotInput; // ---------------- Control Outputs ---------------- typedef struct { float elevator; // Command to elevator (degrees) float aileron; // Command to aileron (degrees) float rudder; // Command to rudder (degrees) uint8_t protections; // Active protections (bitfield): // bit0: alpha-floor, bit1: high-speed, bit2: g-limit } ControlOutput; // ---------------- Protection Limits ---------------- #define MAX_ALPHA 15.0f // Max safe angle of attack (stall protection) #define MAX_SPEED 350.0f // Max safe airspeed (knots) #define MAX_G 2.5f // Max positive G load #define MIN_G -1.0f // Max negative G load #define MAX_ELEVATOR 30.0f // Mechanical limit for elevator #define MAX_AILERON 25.0f // Mechanical limit for aileron #define MAX_RUDDER 30.0f // Mechanical limit for rudder // ---------------- Utility Functions ---------------- // Generate a random float in the range [min, max] float randFloat(float min, float max) { return min + ((float)rand() / (float)RAND_MAX) * (max - min); } // ---------------- Sensor Reading Simulation ---------------- void readSensors(Sensors* s) { // Populate sensor values with realistic random numbers for demo s->pitch_angle = randFloat(-5.0f, 5.0f); // Pitch in degrees s->roll_angle = randFloat(-3.0f, 3.0f); // Roll in degrees s->yaw_angle = randFloat(-2.0f, 2.0f); // Yaw in degrees s->airspeed = randFloat(230.0f, 370.0f); // Airspeed (knots) s->angle_of_attack = randFloat(0.0f, 20.0f); // Angle of attack (deg) s->load_factor = randFloat(-1.5f, 3.5f); // G-load (g) } // ---------------- Pilot Input Simulation ---------------- void readPilot(PilotInput* p) { // Populate pilot inputs with small random values for demo p->sidestick_pitch = randFloat(-2.0f, 2.0f); // Pitch input p->sidestick_roll = randFloat(-1.5f, 1.5f); // Roll input p->rudder = randFloat(-0.5f, 0.5f); // Rudder input } // ---------------- Compute Control Outputs ---------------- void computeControl(const Sensors* s, const PilotInput* p, ControlOutput* out) { float pitch = p->sidestick_pitch; // Start with raw pilot input float roll = p->sidestick_roll; float rud = p->rudder; uint8_t prot = 0; // Protection bits initially zero // --- Alpha-Floor Protection (prevent stall) --- if(s->angle_of_attack > MAX_ALPHA) { pitch -= 0.5f * (s->angle_of_attack - MAX_ALPHA); // Reduce pitch if above safe alpha prot |= 0x01; // Activate alpha-floor bit } // --- High-Speed Protection --- if(s->airspeed > MAX_SPEED) { pitch += 0.3f * (s->airspeed - MAX_SPEED); // Adjust pitch to limit speed prot |= 0x02; // Activate high-speed bit } // --- G-Load Protection --- if(s->load_factor > MAX_G) { pitch -= 0.5f * (s->load_factor - MAX_G); // Reduce pitch for high G prot |= 0x04; // Activate G-limit bit } else if(s->load_factor < MIN_G) { pitch += 0.5f * (MIN_G - s->load_factor); // Increase pitch for negative G prot |= 0x04; // Activate G-limit bit } // --- Mechanical Limits --- if(pitch > MAX_ELEVATOR) pitch = MAX_ELEVATOR; if(pitch < -MAX_ELEVATOR) pitch = -MAX_ELEVATOR; if(roll > MAX_AILERON) roll = MAX_AILERON; if(roll < -MAX_AILERON) roll = -MAX_AILERON; if(rud > MAX_RUDDER) rud = MAX_RUDDER; if(rud < -MAX_RUDDER) rud = -MAX_RUDDER; // Store final control outputs out->elevator = pitch; out->aileron = roll; out->rudder = rud; out->protections = prot; } // ---------------- Send Outputs to Actuators ---------------- void sendToActuators(const ControlOutput* out) { // Print actuator commands and active protection flags printf("Elevator: %6.2f | Aileron: %6.2f | Rudder: %6.2f | Protections: 0x%02X\n", out->elevator, out->aileron, out->rudder, out->protections); } // ---------------- Main Flight Loop ---------------- void flightLoop(void) { Sensors s; PilotInput p; ControlOutput out; readSensors(&s); // 1. Sample sensors readPilot(&p); // 2. Sample pilot inputs computeControl(&s, &p, &out); // 3. Compute outputs with protections sendToActuators(&out); // 4. Output results } // ---------------- Main Program ---------------- int main() { srand((unsigned int)time(NULL)); // Seed RNG printf("Fly-by-wire demo started\n\n"); // Run 5 simulation cycles for(int i = 0; i < 5; i++){ printf("Cycle %d:\n", i + 1); flightLoop(); printf("\n"); } printf("Fly-by-wire demo finished\n"); return 0; }