Method of making a connection, particulary a screw connection

Method of making a connection by means of a controllable screw driver device for turning a screw to make the connection, said method comprising the steps of:

• a) measuring a torque applied to the screw by the screw driver device and a rotation angle of the screw in at least one individual connection step during the making of the connection to obtain measured values of the torque and the rotation angle;
• b) calculating a change in the torque over a rotation angle interval from said measured values and deriving a stiffness parameter from the change in the torque divided by the rotation angle interval;
• c) calculating a change in the rotation angle over a predetermined time interval from said measured values of said rotation angle and deriving a rotation speed as the rotation angle change divided by the predetermined time interval;
• d) analyzing the stiffness parameter and the rotation speed by fuzzy logic means to obtain controlling output variables;
• and
• e) operating said fuzzy-logic means in one of three operating modes to obtain said controlling output variables from said stiffness parameter and said rotation speed and to produce at least one adjusting parameter for the controllable screw driver device from said controlling output variables, said three operating modes including a low stiffness mode, a normal stiffness mode and a high stiffness mode, so as to control the controllable screw driver device to accurately make the connection.

Method of making a connection by means of a controllable screw driver device for turning a screw to make the connection, said method comprising the steps of:

• a) measuring a torque applied to the screw by the screw driver device and a rotation angle of the screw in at least one individual connection step during the making of the connection to obtain measured values of the torque and the rotation angle;
• b) calculating a change in the torque over a rotation angle interval from said measured values and deriving a stiffness parameter from the change in the torque divided by the rotation angle interval;
• c) calculating a change in the rotation angle over a predetermined time interval from said measured values of said rotation angle and deriving a rotation speed as the rotation angle change divided by the predetermined time interval;
• d) analyzing the stiffness parameter and the rotation speed by fuzzy logic means to obtain controlling output variables;
• and
• e) operating said fuzzy-logic means in one of three operating modes to obtain said controlling output variables from said stiffness parameter and said rotation speed and to produce at least one adjusting parameter for the controllable screw driver device from said controlling output variables, said three operating modes including a low rotation speed mode, a normal rotation speed mode and a high rotation speed mode, so as to control the controllable screw driver device to accurately make the connection.