Elevator Control Systems for Commercial Buildings

PROGRAM PLC_CONTROL_LOGIC_EXAMPLE
VAR
    // Inputs
    start_button : BOOL;
    stop_button : BOOL;
    system_ready : BOOL;
    error_detected : BOOL;

    // Outputs
    motor_run : BOOL;
    alarm_signal : BOOL;

    // Internal State
    system_state : INT := 0; // 0=Idle, 1=Running, 2=Error
    runtime_counter : INT := 0;


    // Building Automation
    Occupancy_Count : INT;
    Occupancy_Detected : BOOL;
    Office_Hours : BOOL;
    Weekend_Mode : BOOL;

    // Energy Management
    Demand_Response_Active : BOOL;
    Peak_Shaving_Mode : BOOL;
    Load_Shedding_Level : INT;
    Utility_Rate_Period : STRING[20];  // 'PEAK', 'OFF_PEAK', 'SHOULDER'

    // Scheduling
    Schedule_Override : BOOL;
    Scheduled_Start : TIME;
    Scheduled_Stop : TIME;
    Holiday_Mode : BOOL;

    // Comfort Optimization
    CO2_Level : REAL;  // ppm
    Lighting_Level : REAL;  // Lux
    Adaptive_Control_Active : BOOL;
END_VAR

// ==========================================
// BASE APPLICATION LOGIC
// ==========================================

CASE system_state OF
    0: // Idle state
        motor_run := FALSE;
        alarm_signal := FALSE;

        IF start_button AND system_ready AND NOT error_detected THEN
            system_state := 1;
        END_IF;

    1: // Running state
        motor_run := TRUE;
        alarm_signal := FALSE;
        runtime_counter := runtime_counter + 1;

        IF stop_button OR error_detected THEN
            system_state := 2;
        END_IF;

    2: // Error state
        motor_run := FALSE;
        alarm_signal := TRUE;

        IF stop_button AND NOT error_detected THEN
            system_state := 0;
            runtime_counter := 0;
        END_IF;
END_CASE;

// ==========================================
// COMMERCIAL BUILDINGS SPECIFIC LOGIC
// ==========================================

    // Occupancy-Based Control
    IF NOT Occupancy_Detected AND NOT Office_Hours THEN
        // Setback mode - reduce HVAC, lighting
        Temperature_Setpoint := Setback_Temperature;
        Lighting_Level := 10.0;  // Security lighting only
    ELSE
        Temperature_Setpoint := Comfort_Temperature;
        Lighting_Level := 100.0;
    END_IF;

    // Demand Response Integration
    IF Demand_Response_Active THEN
        CASE Load_Shedding_Level OF
            1: // Moderate reduction
                Temperature_Setpoint := Temperature_Setpoint + 2.0;
            2: // Significant reduction
                Temperature_Setpoint := Temperature_Setpoint + 4.0;
                Non_Essential_Loads := FALSE;
        END_CASE;
    END_IF;

    // Time-of-Use Rate Optimization
    IF Utility_Rate_Period = 'PEAK' THEN
        // Minimize usage during peak rate hours
        Pre_Cool_Complete := TRUE;
        Peak_Shaving_Mode := TRUE;
    END_IF;

    // CO2-Based Ventilation
    IF CO2_Level > 1000.0 THEN  // ppm
        Outside_Air_Damper := MIN(Outside_Air_Damper + 10.0, 100.0);
    END_IF;

// ==========================================
// COMMERCIAL BUILDINGS SAFETY INTERLOCKS
// ==========================================

    Production_Allowed := NOT Emergency_Stop
                          AND Building_Systems_Normal;