To calculate the static load of the motor, it is essential to know certain variables such as: • The total mass and the center of mass of the robot arm (this information can be easily obtained through a CAD software)• The gear ratio of the gearbox coupled to the motor• The orientation of the arm relative to the axis of rotation From here, you can use the fundamentals of statics (PFS) to obtain the torque at the output of the gearbox. Then calculate the torque at the axis of the motor from the reduction ratio. You can even calculate the stresses on the parts using assumptions about the geometry of the parts (for example, assuming that the robot arm has a cross section of a square and hollow section) and using simple formulas of mechanics of materials (Mechanics of Materials). However, if you want to calculate the forces when the robot arm is in motion, it becomes much more complicated. Because it is necessary to know in addition to elements such as the moment of inertia of the mass of the robot arm, and the speed of the arm which depends on the trajectory of the arm. These calculations are generally very specific to a problem / project and require a very detailed CAD model to be calculated accurately.

First of all, I apologize for this late response.

Parameters such as accuracy and speed greatly influence the choice of engine and gearbox. The reason is that dynamic loads are much more dynamic, as the name suggests. This means that the choice of engine and gearbox must meet much more working conditions, rather than a simple static load.

As for specific requirements, it depends on your objectives. If you want your robot to be extremely fast, you will need a much more powerful engine. If you want precision, I think it won’t affect your torque need much, but it will require the choice of exquisite motor drivers and again an engine that is designed for precision (like a stepper motor).

Also, I don’t know French. I use DeepL for translation. So if there’s something lost or doesn’t make sense, sorry in advance.

I wish you a good day.