NSF-Funded Student Design Projects:

Infra-Red Sensing System for Inventory and Process Control

Designer: Guiping Liu
Client Coordinator: Ronald Zapinski, Keith Bovenschen School
Supervisors: Dr. Robert Erlandson, Mr. David Sant
Department of Electrical and Computer Engineering
Wayne State University
Detroit, MI 48202

Introduction

Individuals with cognitive disabilities are precluded from a variety of sorting and packaging jobs because they are not able to remain focused on the task, make frequent errors, and require prompting from a job coach or co-worker to stay focused or correct an error. The Enabling Technologies Laboratory (ETL) has developed a collection of devices, based on universal design principles, to address the needs of individuals with cognitive disabilities and yet satisfy small business needs for cost containment, high quality, and sustained production rates (Erlandson, 2001; Erlandson & Sant, 1998; ETL, 2000). The Infra-Red Sensing System for Inventory and Process Control system is another system that can address the vocational needs of individuals with disabilities.

Summary of Impact

Time has permitted only a pilot test of the Infra-Red Sensing System for Inventory and Process Control. The preliminary testing showed that the system performed according to specifications. The system did provide error-proofing capabilities in that it can identify if the worker reaches into the wrong bin and provide an auditory warning to the worker that he/she is making an error. The system will prompt the worker to stay focused if the sensing system does not sense the worker reaching into a bin within a specified period of time. These strategies work in terms of improving the job performance of and creating jobs for individuals with disabilities (Erlandson, In Press-a; Erlandson, In Press-b).

Technical Description

The ValueScan system is shown in Figure 1. The sensing elements consist of two long narrow units, one contains the emitters and one contains the detectors. The scanning protocol used by the sensing elements allows detection of not only a break of the infra-red light beam between emitters and detectors, but also data as to where along the length of the sensing element the break occurs. The sensing elements connect to the ValuScan controller unit, which in turn connects to a Windows based PC via an RS 232 serial interface.

The sensing elements are mounted on a Creform® frame. Creform® is a pipe and joint technology with over 400 interconnecting parts. Creform® is widely used in a variety of industries for material handling and positioning systems. The frame is designed to hold 1 to 4 plastic bins at an ergonomically appropriate angle for a worker.

Visual Basic was used to create a user infer-face program. This program allows a supervisor to set up the job specifications, the number of bins, the number of parts per bin, sequence critical, and a prompt time. If no sensor occurs during the specified “prompt time”, the system assumes that the worker’s attention has wandered, and a voice prompt reminds the worker to focus and continue the task. The supervisor can record the prompting message.

When the task starts the PC monitor shows the number of bins and indicates, by changing color, when the worker reaches into a bin. The system also decrements the part count in the selected bin. If the task is sequence dependent, i.e., packaging or assembly that must be done in the specific left-to-right order, the system prompts the worker with an error message if he/she enters a bin out of sequence. When the worker has selected an item from each of the bins present, another prompt indicates that one packing cycle is complete.

The system also records the starting time of the job, the times associated with each bin entry, and the job end time. This allows a detailed task/worker analysis.

Figure 1. The ValuScan sensing elements are mounted so that 1 to 4 bins can be placed between the elements. A Creform® frame holds the bins at an ergonomically appropriate angle.

References

Erlandson, R., F. (2001, June 24-27, 2001). A Student Design Program that Integrates Research, Education, and Community Service. Paper presented at the 2001 American Society for Engineering Education Annual Conference & Exposition, Albuquerque, NM.

Erlandson, R. F.. Accessible Design and Employment of People with Disabilities. In J. F. D. Moxlley (Ed.), The Sourcebook of Rehabilitation and Mental Health Practice (Vol. Chapter 19, ). New York: Plenum.

Erlandson, R. F., & Sant, D. (1998). Poka-Yoke Process Controller Designed for Individuals with Cognitive Impairments. Assistive Technology, 10, p102-112.

ETL. (2000). Enabling Technologies Laboratory: Home Page (Vol. 2000): http://www.ece.eng.wayne.edu/etl/.