embeddedLibrary/libraries/dataAcquisition.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>

#include <dataAcquisition.h>

int outlierCount;

// Variable definition
static float **readings;
static int sensorsNumber;
static int slidingWindowSize;

/**
 * @brief Sets the number of sensors.
 *
 * This function sets the global variable `sensorsNumber` to the specified value.
 *
 * @param number The number of sensors to set.
 */
static void setSensorsNumber(int number)
{
    sensorsNumber = number;
}

/**
 * @brief Sets the size of the sliding window.
 *
 * This function sets the size of the sliding window used for data acquisition.
 *
 * @param size The desired size of the sliding window.
 */
static void setSlidingWindowSize(int size)
{
    slidingWindowSize = size;
}

/**
 * @brief Initializes the sensor readings array.
 *
 * This function allocates memory for a 2D array to store sensor readings.
 * Each sensor will have a sliding window of readings.
 *
 * @param numSensors The number of sensors.
 * @param windowSize The size of the sliding window for each sensor.
 *
 * The function performs the following steps:
 * 1. Allocates memory for the array of sensor readings.
 * 2. Allocates memory for each sensor's sliding window of readings.
 * 3. Sets the number of sensors and the sliding window size using private setter functions.
 *
 * If memory allocation fails at any point, the function prints an error message and exits the program.
 */
void initializeReadings(int numSensors, float deltaTime)
{

    int windowSize = (int)(1000 / deltaTime); // Standard case of 1 second of acquisition

    // Allocate memory for the array of sensor readings
    readings = (float **)malloc(numSensors * sizeof(float *));

    // Check if memory allocation was successful
    if (readings == NULL)
    {
        perror("Failed to allocate memory for readings");
        exit(EXIT_FAILURE);
    }

    // Allocate memory for each sensor's sliding window of readings
    for (int i = 0; i < numSensors; i++)
    {
        readings[i] = (float *)calloc(windowSize, sizeof(float));
        if (readings[i] == NULL)
        {
            perror("Failed to allocate memory for sensor readings");
            exit(EXIT_FAILURE);
        }
    }

    // Calling the private setter functions
    setSensorsNumber(numSensors);
    setSlidingWindowSize(windowSize);
}

/**
 * @brief Frees the memory allocated for sensor readings.
 *
 * This function iterates through the array of sensor readings and frees the memory
 * allocated for each individual reading. After freeing all individual readings, it
 * checks if the main readings array is not NULL and frees it as well.
 *
 * @return true if the main readings array was successfully freed, false otherwise.
 */
bool freeReadings()
{
    for (int i = 0; i < sensorsNumber; i++)
    {
        free(readings[i]);
    }

    if (readings != NULL)
    {
        free(readings);
        readings = NULL;
        return true;
    }
    else
    {
        return false;
    }
}

/**
 * @brief Get the number of sensors.
 *
 * This function returns the total number of sensors currently available.
 *
 * @return int The number of sensors.
 */
// Get the number of sensors
int getSensorsNumber()
{
    return sensorsNumber;
}

/**
 * @brief Get the sliding window size.
 *
 * This function returns the current size of the sliding window used in data acquisition.
 *
 * @return The size of the sliding window.
 */
// Get the sliding window size
int getSlidingWindowSize()
{
    return slidingWindowSize;
}

/**
 * @brief Checks if the sliding window for a given sensor is full.
 *
 * This function iterates through the readings of a specified sensor and
 * determines if all entries in the sliding window are non-zero, indicating
 * that the window is full.
 *
 * @param sensorIndex The index of the sensor to check.
 * @return true if the sliding window is full (all entries are non-zero),
 *         false otherwise.
 */
// Control on the fullness of the sliding window
bool isFull(int sensorIndex)
{
    for (int i = 0; i < slidingWindowSize; i++)
    {
        if (readings[sensorIndex][i] == 0)
        {
            return false;
        }
    }
    return true;
}

/**
 * @brief Retrieves the last reading from the specified sensor.
 *
 * This function returns the most recent reading from the sensor identified by
 * the given index. If the sensor's data buffer is full, it returns the last
 * value in the buffer. Otherwise, it returns the first value.
 *
 * @param sensorIndex The index of the sensor to retrieve the reading from.
 * @return The last reading from the specified sensor.
 */
float getLastReading(int sensorIndex)
{
    if (isFull(sensorIndex))
    {
        return readings[sensorIndex][slidingWindowSize - 1];
    }
    else
    {
        return readings[sensorIndex][0];
    }
}

static int lastSensorIndex = -1;

/**
 * @brief Adds a new sensor reading to the data acquisition system.
 *
 * This function updates the readings for the sensors in a circular buffer manner.
 * If the buffer for a sensor is full, it shifts the readings to make space for the new value.
 * If the buffer is not full, it adds the new value to the first available position.
 *
 * @param value The new sensor reading to be added.
 */
void addReading(float value)
{
    lastSensorIndex = (lastSensorIndex + 1) % sensorsNumber;
    int sensorIndex = lastSensorIndex;

    if (isFull(sensorIndex))
    {
        for (int i = 0; i < slidingWindowSize - 1; i++)
        {
            readings[sensorIndex][i] = readings[sensorIndex][i + 1];
        }
        readings[sensorIndex][slidingWindowSize - 1] = value;
    }
    else
    {
        for (int i = 0; i < slidingWindowSize; i++)
        {
            if (readings[sensorIndex][i] == 0)
            {
                readings[sensorIndex][i] = value;
                break;
            }
        }
    }
}

/**
 * @brief Calculates the average reading for a specified sensor.
 *
 * This function computes the average of the readings stored in a sliding window
 * for the sensor specified by the sensorIndex parameter. If the sliding window
 * is not full, the function prints a message and returns 0.
 *
 * @param sensorIndex The index of the sensor for which the average reading is to be calculated.
 * @return The average reading of the specified sensor if the sliding window is full; otherwise, returns 0.
 */
float getAverageOnSensor(int sensorIndex)
{
    if (isFull(sensorIndex) == false)
    {
        printf("The sliding window is not full\n");
        return 0;
    }
    else
    {
        float sum = 0;
        for (int i = 0; i < slidingWindowSize; i++)
        {
            sum += readings[sensorIndex][i];
        }
        return sum / slidingWindowSize;
    }
}

/**
 * @brief Calculates the average reading from all sensors.
 *
 * This function iterates through all available sensors, retrieves the last reading
 * from each sensor, and calculates the average of these readings.
 *
 * @return The average reading from all sensors as a float.
 */
float getAverageOnAllSensors()
{
    float sum = 0;
    for (int i = 0; i < sensorsNumber; i++)
    {
        sum += getLastReading(i);
    }
    return sum / sensorsNumber;
}

/**
 * @brief Calculates the overall average of sensor readings.
 *
 * This function iterates through all sensors and their respective sliding windows
 * to calculate the overall average of the readings. It first checks if the sliding
 * window for each sensor is full. If any sliding window is not full, it prints a
 * message indicating which sensor's sliding window is not full and returns 0.
 * Otherwise, it sums up all the readings from all sensors and calculates the average.
 *
 * @return The overall average of the sensor readings if all sliding windows are full,
 *         otherwise returns 0.
 */
float getOverallAverage()
{
    float sum = 0;
    int totalReadings = 0;
    for (int i = 0; i < sensorsNumber; i++)
    {
        if (!isFull(i))
        {
            printf("The sliding window for sensor %d is not full\n", i);
            return 0;
        }
        for (int j = 0; j < slidingWindowSize; j++)
        {
            sum += readings[i][j];
            totalReadings++;
        }
    }
    return sum / totalReadings;
}

/**
 * @brief Calculates the standard deviation of sensor readings.
 *
 * This function computes the standard deviation of the readings from a specified sensor.
 * It first checks if the sliding window for the sensor is full. If not, it prints a message
 * and returns 0. If the sliding window is full, it calculates the average of the readings,
 * then computes the sum of the squared differences between each reading and the average.
 * Finally, it returns the square root of the average of these squared differences.
 *
 * @param sensorIndex The index of the sensor for which the standard deviation is to be calculated.
 * @return The standard deviation of the sensor readings, or 0 if the sliding window is not full.
 */
float getStandardDeviationOnSensor(int sensorIndex)
{
    if (isFull(sensorIndex) == false)
    {
        printf("The sliding window is not full\n");
        return 0;
    }
    else
    {
        float sum = 0;
        float average = getAverageOnSensor(sensorIndex);
        for (int i = 0; i < slidingWindowSize; i++)
        {
            sum += pow(readings[sensorIndex][i] - average, 2);
        }
        return sqrt(sum / slidingWindowSize);
    }
}

/**
 * @brief Calculates the standard deviation of the readings from all sensors.
 *
 * This function computes the standard deviation of the sensor readings by first
 * calculating the average of all sensor readings, then summing the squared
 * differences between each reading and the average, and finally taking the
 * square root of the average of these squared differences.
 *
 * @return The standard deviation of the sensor readings.
 */
float getStandardDeviationOnAllSensors()
{
    float sum = 0;
    float average = getAverageOnAllSensors();
    for (int i = 0; i < sensorsNumber; i++)
    {
        float lastReading = getLastReading(i);
        sum += pow(lastReading - average, 2);
    }

    return sqrt(sum / sensorsNumber);
}

/**
 * @brief Detects anomalies in sensor readings based on a given average and standard deviation.
 *
 * This function calculates the upper and lower thresholds for anomaly detection using a 97% confidence interval.
 * It then iterates through the sensor readings within a sliding window and counts the number of outliers that fall
 * outside the calculated thresholds.
 *
 * @param average The average value of the sensor readings.
 * @param standardDeviation The standard deviation of the sensor readings.
 *
 * @note The function uses a confidence interval multiplier of 2.17 to determine the thresholds.
 * @note The variable `outlierCount` is used to store the number of detected outliers.
 * @note The variables `slidingWindowSize` and `sensorsNumber` are assumed to be defined globally.
 * @note The 2D array `readings` is assumed to contain the sensor data.
 */
void anomalyDetect(float average, float standardDeviation)
{
    float upperThreshold = average + 2.17 * standardDeviation; // 97% confidence interval
    float lowerThreshold = average - 2.17 * standardDeviation; // Lower bound for anomaly detection
    outlierCount = 0;
    for (int j = 0; j < slidingWindowSize; j++)
    {
        for (int i = 0; i < sensorsNumber; i++)
        {
            if (readings[i][j] > upperThreshold || readings[i][j] < lowerThreshold)
            {
                outlierCount++;
            }
        }
    }
}

/**
 * @brief Calculates the overall standard deviation of sensor readings.
 *
 * This function computes the overall standard deviation of the readings from multiple sensors.
 * It first checks if the sliding window for each sensor is full. If any sensor's sliding window
 * is not full, it prints a message and returns 0. Otherwise, it calculates the sum of the squared
 * differences between each reading and the overall average, and then computes the standard deviation.
 * The function also calls `anomalyDetect` with the calculated average and standard deviation.
 *
 * @return The overall standard deviation of the sensor readings. Returns 0 if any sensor's sliding window is not full.
 */
float getOverallStandardDeviation()
{
    float sum = 0;
    int totalReadings = 0;
    float totalAverage = getOverallAverage();
    for (int i = 0; i < sensorsNumber; i++)
    {
        if (!isFull(i))
        {
            printf("The sliding window for sensor %d is not full\n", i);
            return 0;
        }
        for (int j = 0; j < slidingWindowSize; j++)
        {
            sum += pow(readings[i][j] - getOverallAverage(), 2);
            totalReadings++;
        }
    }

    float totalStandardDeviation = sqrt(sum / totalReadings);

    anomalyDetect(totalAverage, totalStandardDeviation);

    return totalStandardDeviation;
}

/**
 * @brief Retrieves the current count of outliers.
 *
 * This function returns the number of outliers detected and stored in the
 * variable `outlierCount`.
 *
 * @return The number of outliers.
 */
int getOutlierCount()
{
    return outlierCount;
}

Metrics getMetrics(float **readings, int sensorNumber, int slidingWindow)
{
    Metrics metrics;

    float average = 0;
    float standardDeviation = 0;
    int outlierCount = 0;
    int *faultySensors = (int *)malloc(sensorNumber * sizeof(int));

    for (int i = 0; i < sensorNumber; i++)
    {
        faultySensors[i] = 0;
    }

    float sum = 0;

    for (int j = 0; j < slidingWindow; j++)
    {
        for (int i = 0; i < sensorNumber; i++)
        {
            sum += readings[i][j];
        }
    }

    average = sum / (sensorNumber * slidingWindow);

    for (int j = 0; j < slidingWindow; j++)
    {
        for (int i = 0; i < sensorNumber; i++)
        {
            standardDeviation += pow(readings[i][j] - average, 2);
        }
    }

    standardDeviation = sqrt(standardDeviation / (sensorNumber * slidingWindow));
    for (int j = 0; j < slidingWindow; j++)
    {
        for (int i = 0; i < sensorNumber; i++)
        {
            if (readings[i][j] > average + 2.17 * standardDeviation || readings[i][j] < average - 2.17 * standardDeviation)
            {
                outlierCount++;
                faultySensors[i]++;
            }
        }
    }

    int faultySensorsCount = 0;
    for(int i = 0; i < sensorNumber; i++)
    {
        if(faultySensors[i] >= 0.001 * slidingWindow)
        {
            faultySensorsCount++;
        }
    }

    int *possiblyFaultySensors = (int *)malloc(faultySensorsCount * sizeof(int));

    int j = 0;
    for (int i = 0; i < faultySensorsCount; i++)
    {
        if (faultySensors[i] >= 0.001 * slidingWindow)
        {
            possiblyFaultySensors[j] = i;
        }
    }

    metrics.mean = average;
    metrics.standardDeviation = standardDeviation;
    metrics.possibleFaultySensor = possiblyFaultySensors;
    free(faultySensors);
    return metrics;
}