System and method for multi-axis simulation
A multi-axis fatigue testing device includes a multiple input, multiple output mechanical linkage driven by a plurality of actuators and a controller operating each of the plurality of actuators in real time and in synchronization to produce user-defined multiple fatigue cycle profiles. A startup method enables a sample mounted at an arbitrary multi-axis state to receive a desired simulation profile while maintaining the sample below any of the extremum values of the desired simulation profile.
1. A startup method for a multi-axis simulation system including a test fixture having a multiple-input-multiple-output linkage, the multiple-input-multiple-output linkage driven by a first actuator and a second actuator, the multiple-input-multiple-output linkage acting on a sample holder to control the position of the sample holder along a first simulation axis and a second simulation axis, the method comprising:
receiving a first simulation axis profile characterized by a first profile amplitude and a second simulation axis profile characterized by a second profile amplitude;
calculating an initial position for the first actuator based on the first simulation axis profile, the second simulation axis profile, and characteristics of the multiple-input-multiple-output linkage;
moving the first actuator to the initial position, the initial position of the first actuator causing the multiple-input-multiple-output linkage to position the sample along the first simulation axis within a subset of a peak-to-peak range of the first simulation axis profile and along the second simulation axis within a subset of a peak-to-peak range of the second simulation axis profile;
operating the first actuator to cause the multiple-input-multiple-output linkage to track the first and second simulation axis profiles and constrain first simulation axis values applied to the sample holder to within the peak-to-peak range of the first simulation axis profile while increasing the first actuator's amplitude from an initial value of zero to the first profile amplitude at a predetermined rate which is less than 10% per cycle.
2. The method of claim 1 wherein the predetermined rate is less than 9% per cycle.
3. The method of claim 1 wherein the predetermined rate is 1% per cycle.
4. The method of claim 1 wherein the first simulation axis is an axial strain.
5. The method of claim 4 wherein the second simulation axis is a bend angle.
6. The method of claim 1 wherein the subset of the range of the first simulation profile comprises a point in a region containing a middle half of a peak-to-peak range of the first simulation profile and the subset of the range of the second simulation profile comprises a point in a region containing a middle half of a peak-to-peak range of the second simulation profile.
7. The method of claim 1 wherein the subset of the range of the first simulation profile comprises a mean value of the first simulation axis profile and the subset of the range of the second simulation profile comprises a mean value of the second simulation axis profile.
8. The method of claim 1 wherein subset of the range of the first simulation profile comprises one-half of a value of the first simulation profile.
9. The method of claim 1 wherein the step of moving includes:
operating the first actuator to disengage a bend tool contacting the sample;
operating the second actuator to an initial position calculated for the second actuator; and
operating the first actuator to the initial position calculated for the first actuator.
10. A non-transitory computer medium containing computer instructions stored therein for causing a computer processor to perform the method of claim 1 .
11. A multi-axis simulation system comprising:
a test fixture having a multiple-input-multiple-output linkage, the multiple-input-multiple-output linkage driven by a first actuator and a second actuator, the multiple-input-multiple-output linkage acting on a sample holder to control the position of the sample holder along a first simulation axis and a second simulation axis;
a controller configured to
receive a user-specified first simulation axis profile characterized by a first profile amplitude and a second simulation axis profile characterized by a second profile amplitude,
calculate an initial position for the first actuator based on the first simulation axis profile, the second simulation axis profile, and characteristics of the multiple-input-multiple-output linkage;
move the first actuator to the initial position, the initial position of the first actuator causing the multiple-input-multiple-output linkage to position the sample along the first simulation axis within a subset of a peak-to-peak range of the first simulation axis profile and along the second simulation axis within a subset of a peak-to-peak range of the second simulation axis profile;
operate the first actuator to cause the multiple-input-multiple-output linkage to track the first and second simulation axis profiles and constrain first simulation axis values applied to the sample holder to within the peak-to-peak range of the first simulation axis profile while increasing the first actuator's amplitude from an initial value of zero to the first profile amplitude at a predetermined rate which is less than 10% per cycle.
12. The system of claim 11 wherein the first simulation axis is an axial strain and the second simulation axis is a bend angle.
13. A non-transitory computer medium containing computer instructions stored therein for causing a computer processor to execute a startup procedure on a multi-axis simulation system including a test fixture having a multiple-input-multiple-output linkage, the multiple-input-multiple-output linkage driven by a first actuator and a second actuator, the multiple-input-multiple-output linkage acting on a sample holder to control the position of the sample holder along a first simulation axis and a second simulation axis by:
receiving a first simulation axis profile characterized by a first profile amplitude and a second simulation axis profile characterized by a second profile amplitude;
calculating an initial position for the first actuator based on the first simulation axis profile, the second simulation axis profile, and characteristics of the multiple-input-multiple-output linkage;
moving the first actuator to the initial position, the initial position of the first actuator causing the multiple-input-multiple-output linkage to position the sample along the first simulation axis within a subset of a peak-to-peak range of the first simulation axis profile and along the second simulation axis within a subset of a peak-to-peak range of the second simulation axis profile;
operating the first actuator to cause the multiple-input-multiple-output linkage to track the first and second simulation axis profiles and constrain first simulation axis values applied to the sample holder to within the peak-to-peak range of the first simulation axis profile while increasing an amplitude having an initial value of zero to a value characterizing an amplitude of the first simulation profile at a predetermined rate which is less than 10% per cycle.
14. The non-transitory computer medium of claim 13 further containing computer instructions stored therein for causing the computer processor to:
operate the first actuator to disengage a bend tool contacting the sample;
operate the second actuator to an initial position calculated for the second actuator; and
operate the first actuator to the initial position calculated for the first actuator.