Muscle lines of action in the lower extremity: A centroid line approach vs the straight line approach : R.P. Mikosz, R. McKersie, R. Berg, P. Snitovsky, J. Lobick, S. Logue, G.B.J. Andersson and T.P. Andriacchi, Department of Orthopedic Surgery, Rush-Presbyterian-St. Luke's Medical Center, 1753 West Congress Parkway, Chicago, Illinois 60612

Abstract

The manufacture of certain garments, such as underwear, requires the attachment of tensioned elastics and tapes to workpieces. If the elastic is incorrectly tensioned, when it returns to its original length the garment will be too tight or too loose, and a sub-standard garment is produced. Two distinct processes are involved in the feed of elastic for such an operation. These are precise control of the elastic tension and of the rate of feed of the workpiece into the sewing machine. The former can be achived with a fully automated control system while the latter usually involves an operator, thus requiring a man/machine inteface.This paper describes the design and development of an adaptive microprocessor-based control system to implement the above operations. The system employs closed-loop control to maintain precise elastic tension. It also uses an adaptive control loop to compensate for practical problems such as manual workpiece feed rate, elastic feed path friction, and changes in the physical characteristics of the elastic. The system has been implemented with a 68000 single board computer for all control calculations, a stepper motor, a force transducer, and optical sensors. The performance simulation results are given and compared to those of conventional open-loop systems. Practical operational data is also presented.