I have a trailer and I want to calculate the driving force on it in different driving situations. By the word driving force (Fd), I mean Fd >= 0 if trailer acceleration >=0 and Fd
Maryam,
Your Q is not clear, but the foloowing might be a starter.
Firstly, just consider the horizontal forces in the direction of travel only. Then you would have the traction force forward, and aerodynamic drag, road friction drag and possibly the braking force.
The aerodynamic force is normally based on the cross section area (A) of the trailer body, and the equation is 0.5 X air density X square of velocity X A X Drag Coefficient. All the data are physical, except the drag coefficient, which is basically an aerodynamic data based on the shape and proportion of the dimensions of the object. For a trailer, it should be around 0.8 to 1.2. You may have better reference for this data. But for comparison, a flat plate with wind blowing perpendicular to the surface has a drag coefficient of 1.6 to 1.65.
As for the road force, it should be friction coefficient (mu) X vertical Reaction force. This acts at the wheels of the trailer. The reaction force is physical, and the coefficient could be found from data. I suggest values from 0.3 to 0.5.
And I think as a starting point, assume there is zero braking force.
I hope this will be useful to you.
Wan Zaidi
Rolling drag is a function of speed. Aerodynamic drag is a function of speed squared.
Then it's only a case of Newton's laws of movement.
thanks all for your answers. Here again I make my question clear maybe you have a better answer.
I have a generator that I want to use it in order to convert the brake and retarder power to Electricity. I want to define the current of this generator?
I thought I must know the driving force and use it to control the generator current. If you have a better suggestion I will be happy to hear.
Maryam,
As for the road force, it should be friction coefficient (mu) X vertical Reaction force. This acts at the wheels of the trailer. The reaction force is physical, and the coefficient could be found from data. I suggest values from 0.008 to 0.015 .
And assume there is zero braking force.
as you gain the accelerations in different directions, you can formulate all frictional and drag forces according to the Newton second law in all directions. So, by placing your trailer weight and multiplying it by acceleration with negative friction forces according to superstition forces rule, all original forces will be obtained, clearly.
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