Textruta: Above This is the frequency spectrum as computed by PEMpro2. Some of the "peaks" are not fundamentals (i.e. multiples of the worm period). The red text above is related to the gears in the motor and is generally not related to any fundamentals. As it happens T4 coincides with the 33rd funtamental (F33). Below We will try to elliminate the main components (highest peaks in the frequency spectrum above) one by one and see what will be left. Left The blue curve is the original recorded data for one period, the purple curve is the periodic error (W or F1) computed by PEMpro2. PE = 20 (+/- 10) arcsec (blue curve) Note that there is a lot of noise on top of the W
Textruta: The blue curve is the PE that remains after W (or F1) has been removed. PE = 9.4 (+/- 4.7) arcsec (blue curve) The purple curve is PE related to the fourth axis (A4).
Textruta: The blue curve is the PE that remains after W and A4 has been removed. PE = 7.3 (+/- 3.65) arcsec (blue curve) The purple curve is PE related to the fifteenth fundamental (F15).
Textruta: The blue curve is the PE that remains after W, A4 and F15 has been removed. PE = 7.2 (+/- 3.6) arcsec (blue curve) Note that the improvement is minor. The purple curve is PE related to the third axis (A3).
Textruta: The blue curve is the PE that remains after W, A4, F15 and A3 has been removed. PE = 6.7 (+/- 3.4) arcsec (blue curve) Note that the improvement is minor. The purple curve is PE related to the teeth on gear 4 (T4). Note that T4 coincides with F33.
Textruta: The blue curve is the PE that remains after W, A4, F15, A3 and T4 has been removed. PE = 5.6 (+/- 2.8) arcsec (blue curve) Note that there is actually some improvement. Conclusions The fifteenth fundamental does not really contribute. Except for the worm period correction (W), A4 and T4 also gives significant improvemtns, indicating that there is something wrong with this part of the motor. Removing all the above components does not give a satisfactory PE. There is a lot of fairly high frequency noise left. It may be due to the "sintered metal" of two of the gears in the gear box as outlined in Mike Dodds pdf? Or is it something else?
Textruta: Comparision to measurement with PEC turned on To the left is a PEMpro2 measured curve (blue) when PEC was turned on in the Hand Control of the CGE mount. The purple curve corresponds to A4. PE = 8.8 (+/- 4.4) arcsec (blue curve) This is not as good as the curve above, but note that PEC can not remove A4 and T4. Removing A4 and A3 results in a PE = 6.6 (+/- 3.3) arcsec. Which is a little bit worse than above but still comparable within error margins. The high frequency noise remains???? Note that removing any fundamental (e.g. F15 or F33) from the blue curve will make the PE worse. The reason is that all fundamentals are dealt with in the PEC.