Calculating motor torque for a robotic arm

If we want to find the static load on the motor axis, the values we need to know about the arm are:

- Total weight and center of gravity with respect to the rotation axis. (This information can be obtained from CAD programs)
- The gear ratio of the gearbox attached to the motor.
- The angle of the robot arm with respect to the rotation axis.

Based on these values, the loads on the output of the gearbox by the robot arm can be calculated with simple static formulations. After that, the torque required for the motor to hold the arm at a certain angle can be calculated using the gear ratio. However, if we want to calculate the torque values that the motors will need when the robot arm is in motion, we need to know the mass inertia moment and the speeds that the arm will have on the path it will take.