Locator and Sensor Placement for Automated Coordinate Checking Fixtures

Abstract

This article proposes a systematic method for the optimal design of sensor locations for an automated Coordinate Checking Fixture (CCF). The fixture can be employed for making at-machine assessments of the dimensional accuracy of manufactured components. Coordinate measurements obtained by the sensors built into the fixture can be utilized in estimating geometric parameters of a manufactured part. Two important issues that arise in the design of a CCF are the optimal number of sensors to be used and the best locations for each sensor. The proposed method uses statistical analyses of the Fisher information matrix and the prediction matrix to obtain an optimal set of sensors from an initial candidate set. Sensors are placed at locations that maximize the determinant of the Fisher information matrix for best parameter estimation, while the sensor of the least contribution to the measurement objective is iteratively eliminated. With the benefit of physical insight, the design procedure results in a balanced decision for the optimal placement of sensors. The developed method also addresses the problem of selection of part locators for part localization in the CCF. Examples are provided for illustration of the developed procedure for automotive space frame extrusion parts.

Tolerance Optimization Considerations Applied to the Sheet Metal Compliant Assembly

“…Diagnostic approaches for single fault of fixture failures in assembly processes were proposed by Ceglarek and Shi [1]. Wang and Nagarkar [2], han and Ceglarek [3] and Khan et al [4] studied the locator and sensor placement for the automated coordinate checking fixtures and assembly systems, respectively, for rigid parts. The modeling and diagnosis of sheet metal assembly considering the compliant characteristics such as the part-to-part interferences and the part fabrication errors has been studied.…”

Distributed Sensing for Quality and Productivity Improvements

“…As stated before, Problems 2) and 3), which focus on the determination of the number and locations of sensors, are usually called the problem of "sensor placement" in engineering practice [11], [12]. It is important to note that the "location of a sensor" bears two meanings in the literature.…”

Optimal sensor distribution in multi-station assembly processes for maximal variance detection capability

“…Another often used criterion for sensor placement is the sensitivity of a sensor system (Wang and Nagarkar, 1999;Camelio et al, 2005;Liu et al, 2005) -we will present the formal definition of the sensitivity in Section 2. Intuitively, the sensitivity is related to the detection capability of a sensor system.…”

“…The aforementioned work using the sensivity criterion (Wang and Nagarkar, 1999;Camelio et al, 2005;Liu et al, 2005) was conducted primarily under a single-station setting. This is not surprising because solving the sensor distribution problem for a multi-station system is generally more difficult, a point argued previously in Ding et al (2006) and Mandroli et al (2006).…”