Method for controlling a mechanical joining or forming process

A method for controlling a mechanical joining or forming process comprising a friction drilling process in which a friction drilling screw is driven to penetrate through thin-walled materials, the method including:

• (a) applying a first fluid pressure to a pneumatic actuator to generate a process parameter over an actual course for the process parameter, the actual course for the process parameter corresponding over time with a nominal course for the process parameter wherein the nominal course for the process parameter includes a nominal process parameter change from a first nominal process parameter value to a second nominal process parameter value the nominal process parameter change corresponding to a point in the friction drilling process at which the friction drilling screw penetrates through the thin-walled materials;
• (b) while applying the first fluid pressure to generate the process parameter, applying a number of reverse pulses acting on the process parameter in opposition to the first fluid pressure at least over a portion of the actual course for the process parameter corresponding in time to a portion of the nominal course for the process parameter which encompasses the nominal process parameter change and also continues after the nominal process parameter change;
• and
• (c) wherein the number and length of the reverse pulses and the length of the intervals between the reverse pulses are determined as a function of at least one immediately detectable variable associated with the process parameter.