Design, Construction and Calibration of a Triaxial Dynamometer for Measuring Forces and Moments Applied on Tillage Implements in Field Conditions

Abstract

In this research, a dynamometer was designed, constructed and calibrated to measure the forces and moments applied on tillage implements. This dynamometer is able to measure the three orthogonal forces acting on the implement and the three moments acting around the orthogonal axes, up to a maximum force of 20 kN and a maximum moment of 20 kN m. The dynamometer uses two extended octagonal ring transducers mounted in a back-to-back arrangement with their axes at right angles and has a tubular torque meter for torque measurement. For mechanical design of the dynamometer frame and its units, the finite element method and CATIA software were used. The device was machined from the solid part and high tensile steel. The forces and moments acting on the dynamometer were measured by using the strain gauge bridges on two extended octagonal ring transducers and on the torque meter tube. The results of data analysis, including forces applied on the dynamometer, the designing method of rings and torque meter tubes, the mounting arrangement of load cell parts on each other, the mounting method of load cell on frame and the position of strain gauge on load cell, in other words, the position of different parts of the dynamometer relative to each other has been explained in this paper. Calibration of the measurement unit was done by a calibration system which was designed for static calibration of the triaxial dynamometer. The results of calibration of the measurement unit showed that the designed and constructed dynamometer has appropriate precision, sensitivity and good repeatability for measuring the desired forces and moments. The results showed a high degree of linearity between output voltage of bridges and applied forces and moments. The interaction effects of the applied forces and moments were very negligible.