Stack structured hybrid load cell for a high-stroke system

Abstract

The load cell is an essential sensor for the force measurement systems. The sensitivity of a typical load cell for general force measurement is constant over the full operating range. For high stroke systems such as hydraulic systems, this property is not suitable because of insufficient resolution at the small loading force. High stroke systems require higher sensitivity in the small loading force compared with in the large loading force. In other words, for the high control performance, the smaller loading force is applied, the higher sensitivity is necessary to the systems. The optimal relationship between strain and force can be expressed as a logarithmic function. Based on this relationships, we developed a hybrid load cell which has a piece-wised linear model based on a stack structure. In addition, equipment for loading test was invented to examine and compensate the load cell quantitatively. By using this equipment, compressive force, tensile force and torque can be applied from a small force to a large force in accordance with the seesaw principle. The performance of the proposed system was verified by experiments.

Keywords

• load cell
• strain
• logarithm
• piecewise model
• hybrid structure