Autotuning control of a precision balance for mass and density measurements

This paper deals with the design and the implementation of several autotuning controllers for the electronic reading device of a mechanical precision balance to be used in an automatic weighing system for mass and density measurements of solid specimens. The severe specifications to be accomplished by the control loop as well as the changing environment require frequent fine retuning of the controller. The control design is based on an identified linear parametric model of the plant. The identification and tuning process is fully automated but can be easily followed and/or modified by a human operator. The achieved repeatibility of the measurements are below 2 /spl mu/g.<>