An improved posture evaluation method of cylindrical intersecting holes on large aerospace component based on monocular vision

Cylindrical intersecting holes(CIHs) are common connection and location reference features in assembly of large aerospace structures such as missile and rocket cabins. The posture accuracy of assembly holes significantly impacts the relative position accuracy of joined parts and fatigue strength of finished product. At present, monocular vision measurement is widely used in automatic drilling of assembly holes for its integration simplicity and lower cost, but in most research, only the front face edge of the hole is used in the measurement model, and the hole end surface is usually assumed to be plane, which inevitably leads to precision loss. In this research, a novel posture measurement method for CIHs is proposed. Firstly, by introducing an ambiguity removal strategy, a coarse posture estimation method based on plane hypothesis of the two end surfaces of CIHs is suggested. Secondly, considering that there is no simply explicit expression for CIHs edge, thus it is difficult to adopt the conventional model projection based pose optimization method. In view of this, the three-dimensional points corresponding to the edge pixels of CIHs image are derived, and the pose optimization model is established by minimizing the deviations between the distance from the points to the CIHs axis and the hole radius. Moreover, to better control the direction parameters of CIHs during the global optimization process, the approximately perpendicular and intersection constraints between CIHs axis and cylindrical component axis are involved in solution. The effectiveness of the posture measurement method is verified by comparative experiments with current methods and CMM, which demonstrates improvements on both measurement accuracy and robustness.

Development of a System for Measurement on Asymmetric Sitting Posture

Sitting posture measurement system using the unstable board with accelerometer was developed. And, postural balance was assessed to determine the effect of asymmetry on sitting posture between patients with pelvic asymmetry and healthy subjects. 10 subjects (pelvic asymmetry patients:5, healthy controls:5) were participated in this study. We performed experiment under static and dynamic sitting condition. Angular variation in the anterior-posterior and left-right direction was measured in both two conditions. Also, intra class correlation coefficient was used to evaluate the reliability of the system. The value of angle of pelvic asymmetry patients was more tilted significantly to the left side than right side during static and dynamic sitting. The reliability of the system was excellent. This paper suggested that a system for measurement on asymmetric sitting posture can be utilized to provide useful information about patients with pelvic asymmetry in rehabilitation medicine. Furthermore, results from this study can be used to develop the new clinical quantitative measurement system.

The Association of Muscle Dysmorphia, Social Physique Anxiety, and Body Checking Behavior in Male College Students With Weight Exercise

Objectives: To investigate the association between muscle dysmorphia (MD), social physique anxiety, and body-checking behavior in male college students with weight exercise, and to reveal the association between them.Methods: A total of 492 male college students with weight exercise from 18 Fitness Clubs or bodybuilding centers in Chengdu, China, participated in this study.Results: First, the social physique anxiety scores, body checking frequency, and weight exercise behavior (i.e., frequency, time, and intensity) in male college students with MD were significantly higher than those without MD; it indicated that the higher the exercise frequency they had, the longer the exercise time they cost, and the higher exercise intensity carried out, and the higher the social physique anxiety scores tended to be, the higher the frequency of body checking on “global muscles,” “chest and shoulder muscles,” “comparison with others” and “posture measurement” they did. Second, the mediating effect of the social physique anxiety on MD and body checking was established in the “MD → global muscle checking,” “MD → chest and shoulder muscle checking,” “MD → comparison with others,” and “muscle dysmorphia → posture measurement.”Conclusion: Male college students with MD not only have a higher social physique anxiety, but also a higher frequency of body-checking behavior than the ordinary individuals. Social physique anxiety is one of the important mediating factors to those with MD which affects the body-checking behavior.