Method and apparatus for controlling the oscillatory motion of a test device

A method for controlling the oscillatory motion of a device under test, including the steps of:

• determining a set of values of position samples of said device under test;
• calculating an average of said values for one cycle for a period of time from a time=0 to a time=t;
• determining a difference between said average and a desired value;
• and
• controlling an applied force to said device under test responsive to said difference.

An apparatus for controlling the oscillatory motion of a device under test, the device having a first end and a second end, and being mounted in a test fixture, comprising:

• a base rigidly connectable to said first end of said device under test;
• a load actuator connectable to said second end of said device under test;
• an electrohydraulic control system connected to said load actuator;
• a controller electrically connected to said electrohydraulic control system;
• a displacement sensor connected to said electrohydraulic control system, said displacement sensor being adapted for delivering a displacement feedback signal to said controller;
• and
• a load sensor connected to said first end of said device under test, said load sensor being adapted for delivering a load amplitude feedback signal to said controller.