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Chapter 7. Experimental Measurements This chapter attempts a comparison between the analytical predictions of the performance of XY Flexure
 

Summary: 181
Chapter 7. Experimental Measurements
This chapter attempts a comparison between the analytical predictions of the performance of XY Flexure
Mechanism Design 6 made in Chapter 5, and the experimental measurements obtained from the test set-
up described in Chapter 6. This section presents the experimental measurements based on the prototype
fabricated by wire EDM.
In all the laser interferometry based experiments, the uncertainty in measurement is due to cosine errors
resulting from laser optics misalignment, and change in ambient temperature, pressure and humidity. To
minimize these error sources, the optics were very carefully aligned, the dead paths were kept small, and a
compensation for the wavelength of light based on temperature, pressure and humidity measurements,
was included. The overall uncertainty in measurement as a consequence of all these effects is of the order
of 25nm. Other important sources of errors arise from actual physical effects such as thermal expansion
and misalignment of the target block. The former was taken care of by conducting the experiments in a
temperature controlled environment, whereas the latter was resolved by measuring the target block
misalignment explicitly on a CMM. The single most detrimental effect on the measurements arose from
the ball bearing used in the pulley for suspending free weights. Hysteresis and creep at the interface of the
fishing line and the pulley, and the balls and the race, resulted in large unexplained variations in the
measurements of the order of 200nm. As pointed out earlier, this problem may be resolved by
implementing a virtual pulley instead of a real pulley.
When weights are used for actuation, there is an uncertainty in the actual value of the weight, which is of

  

Source: Awtar, Shorya - Department of Mechanical Engineering, University of Michigan

 

Collections: Engineering