These vibrations may reflect the dynamic phenomena in

  • No School
  • AA 1
  • 13

This preview shows page 3 - 6 out of 13 pages.

These vibrations may reflect the dynamic phenomena in the cutting process that is very detrimental to the machined surface, the tool life and even the spindle. [6], [7] [8] . Impact tests take place in three configurations defined in the experimental protocol, representing some of the common positions in cutting composite parts. Following this analysis as follows: P 1 configuration, the robot arm is in a position closest to the robot base, followed by position P 2 and P 3 which crossed the robot moves on a well defined trajectory to the point P 1 , presented in figure 3. Figure 3: The experimental position for impact test. The results of the frequency spectra measurements for each configuration (Figure 3) P 1 , P 2 , and P 3 are presented on figure 4. It can be observed the two main frequency ranges that we will call: LFR- Low Frequency Range, with a frequency range between: 0-250 Hz and HFR- High Frequency Range, with a frequency range between: 1200-3600 Hz. The importance of this study is to identify the robot stiffness, considering that it presents low frequency [9] it has to determine these frequencies in different configurations
Image of page 3
4 ICASAAM 2011 7-10 September 2011 Bucharest Romania in order to optimize de cutting robot parameters in order to reduce the effect of the low frequencies respectively the low stiffness of the robot. Figure 4: Frequency spectrum for P 1 , P 2 and P 3 position Given the objective characterization of rigidity for various working positions of the robot, we are interested in low frequency range, where the basic rigidity of the robot is emphasized [9]. In order to identify this basic rigidity, a low frequency analysis is made of the frequencies measured during the impact tests in the range 0- 250 Hz. The acquisition data is made by continuous acquisition with a sample rate of 6250 samples / sec,) a buffer size of 32 768 samples, and block size of 2000 samples. Figure 5: Waterfall frequency diagram for X direction in P 1 position
Image of page 4
5 7-10 September 2011 Bucharest Romania ICASAAM 2011 Figure 6: Waterfall frequency diagram for X direction in P 2 position Based on signal processing, Waterfall diagram are used to identify the self-excited frequencies generated by hammer impact excitation. Waterfall diagram is necessary in this analysis because the impact hammer tests are made on-time and we can highlight self-excited frequencies and also their dissociation in relation to external frequencies. Thus the quality of the analysis can easily identify the electrical grid frequency of 50 Hz and the 100 Hz. For the X measurement direction from the impact excitation, the spectrum is observed similar for every tested position. But a slight shift of the fundamental lower frequency (7-10 Hz) to the increase frequency is observed. The P 1 position presents the value of 17 Hz (figure 5), while frequency increases to P 2 with 20 Hz (figure 6) and 22 Hz for P 3 (figure 7 ).
Image of page 5
Image of page 6

You've reached the end of your free preview.

Want to read all 13 pages?

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors