WOLFRAM SYSTEM MODELER
    Add4Output the sum of the four inputs  | 
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SystemModel["Aircraft.Utilities.Add4"]

This blocks computes output y as sum of the three input signals u1, u2, u3 and u4:
y = k1*u1 + k2*u2 + k3*u3 + K4*u4;
Example:
parameter: k1= +2, k2= -3, k3=1, k4 = -2;
results in the following equations:
y = 2 * u1 - 3 * u2 + u3 -2u4;
| k1 | 
         Value: +1 Type: Real Description: Gain of 1st input  | 
    
|---|---|
| k2 | 
         Value: +1 Type: Real Description: Gain of 2nd input  | 
    
| k3 | 
         Value: +1 Type: Real Description: Gain of 3rd input  | 
    
| k4 | 
         Value: +1 Type: Real Description: Gain of 4th input  | 
    
| y | 
         Type: RealOutput Description: Connector of Real output signals  | 
    
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| u1 | 
         Type: RealInput Description: Connector 1 of Real input signals  | 
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|---|---|---|
| u2 | 
         Type: RealInput Description: Connector 2 of Real input signals  | 
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| u3 | 
         Type: RealInput Description: Connector 3 of Real input signals  | 
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| u4 | 
         Type: RealInput Description: Connector 3 of Real input signals  | 
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| y | 
         Type: RealOutput Description: Connector of Real output signals  | 
    
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         Aircraft.ControlSystems.MultiRotorControllers Control the attitude and height of the quadrotor through PID controllers  | 
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         Aircraft.ControlSystems.MultiRotorControllers Control the position and attitude of the quadrotor through PID controllers  | 
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         Aircraft.Utilities Mixer to convert force and moments to the propeller forces  |