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Research Papers

Digitalization of Human Operations in the Age of Cyber Manufacturing: Sensorimotor Analysis of Manual Grinding Performance

[+] Author and Article Information
Gregory L. Bales

Mem. ASME
Mechanical and Aerospace Engineering,
University of California,
Davis, CA 95616
e-mail: glbales@ucdavis.edu

Jayanti Das

Mechanical and Aerospace Engineering,
University of California,
Davis, CA 95616
e-mail: jydas@ucdavis.edu

Jason Tsugawa

Mechanical and Aerospace Engineering,
University of California,
Davis, CA 95616
e-mail: jztsugawa@ucdavis.edu

Barbara Linke

Mem. ASME
Mechanical and Aerospace Engineering,
University of California,
Davis, CA 95616
e-mail: bslinke@ucdavis.edu

Zhaodan Kong

Mem. ASME
Mechanical and Aerospace Engineering,
University of California,
Davis, CA 95616
e-mail: zdkong@ucdavis.edu

Manuscript received February 3, 2017; final manuscript received August 13, 2017; published online September 1, 2017. Assoc. Editor: Ivan Selesnick.

J. Manuf. Sci. Eng 139(10), 101011 (Sep 01, 2017) (8 pages) Paper No: MANU-17-1071; doi: 10.1115/1.4037615 History: Received February 03, 2017; Revised August 13, 2017

This paper presents new techniques to analyze and understand the sensorimotor characteristics of manual operations such as grinding, and links their influence on process performance. A grinding task, though simple, requires the practitioner to combine elements from the large repertoire of his or her skillset. Based on the joint gaze, force, and velocity data collected from a series of manual grinding experiments, we have compared operators with different levels of experience and quantitatively described characteristics of human manual skill and their effects on manufacturing process parameters such as cutting energy, surface finish, and material removal rate (MRR). For instance, we find that an experienced subject performs the task in a precise manner by moving the tool in complex paths, with lower applied forces and velocities, and short fixations compared to a novice. A detailed understanding of gaze-motor behavior broadens our knowledge of how a manual task is executed. Our results help to provide this extra insight, and impact future efforts in workforce training as well as the digitalization of manual expertise, thereby facilitating the transformation of raw data into product-specific knowledge.

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Figures

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Fig. 1

Setup of our grinding experiment. Data were collected from three separate modules: (1) gaze tracking consisting of SensoMotoric instruments eye-tracking glasses and a computer running iView recording software; (2) force measurement consisting of a triaxial load cell and a computer running labview; (3) motion capture system by Optitrack, which can determine the position and orientation of selected objects. The data collected from these three modules were synchronized and analyzed using the methods described in Sec. 3.

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Fig. 2

Detail of the grinding sample and force data collection module. Forces in three directions were measured: tangential (x-axis), normal (z-axis), and axial (y-axis). The reflective spheres are used by the motion tracking system.

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Fig. 3

An example scanpath. The centers of fixations are denoted by points. The durations of fixations are represented by the diameters of the circles. The fixation centers are connected by straight lines according to their temporal order. Each straight line corresponds to a saccade.

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Fig. 4

Normalized histogram of the tangential and axial tool velocities for all subjects

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Fig. 5

Comparison of skewed fixation distributions between subjects. A vertical line within the rectangular box indicates the median of the distribution. Outliers beyond the 90th percentile labeled with a cross.

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Fig. 6

Comparison of modal responses in the gaze-motor behavior of all subjects

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Fig. 7

Sample of fixation points for a single subject. Positions are reported in pixels on the original 1280 by 960 pixel field of view. Notice the asymmetric dispersion of shifts.

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Fig. 8

Distributions of the fixational variations for all the trials. The whiskers extend to the 90th percentile of the distribution. Outliers are represented as red crosses.

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Fig. 9

(a) Plot of normal and tangential forces for all subjects. (b) Tangential and normal force distributions between subjects. The height of the bars represents the mean force for each trial with the standard deviations indicated.

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Fig. 10

Tangential force variation versus mass removal during grinding

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Fig. 11

Normal force variation versus mass removal during grinding

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Fig. 12

Average surface roughness variation versus mass removal during grinding

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Fig. 13

Average surface roughness variation versus tangential force

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