Method for determining a torque and an industrial robot

A method for determining with a controller of a robotic manipulator a torque having an effect on a link of a robotic arm, whereby the robotic arm has several sequentially arranged links, of which a first link is supported relative to a second link of the links on an axis of rotation, and by use of a stationary motor relative to the second link and a gearbox then connected to the motor, is rotatable around the axis of rotation, the method comprising:

• determining the angle of rotation turned toward the driving side of the motor and the angle of rotation turned to the reducing side of the gearbox, and
• determining the torque having an effect on the first link on the basis of the determined driving side and reducing side angles of rotation of the gearbox and based on a mathematical model of the gearbox, wherein the mathematical model takes into account at least one of:
• the elastic properties of the gearbox,
• a hysteresis that depends on the direction of rotation of the gearbox,
• a rotational direction of the gearbox,
• a transmission error of a gearbox unit,
• a speed of rotation of the motor,
• a deformation of the gearbox dependent on the load, or
• an increasing and decreasing deformation of the gearbox.