Displacements in a Vibrating Body by Strain Gage Measurements

An important issue in the position control of elastic systems is the correct on-line measurement of displacements. EndPoint Control of flexible manipulators, for example, requires the measurement of the manipulator's tip displacement. While this kind of measurement is relatively easy to carry out in a laboratory setting, it can be problematic in a real world environment. A novel procedure for the real-time determination of displacements at any point of a vibrating body is proposed. The procedure calls for the use of strain gauges and the knowledge of the modal properties of the structure. Advantages of the proposed method are its simplicity and low cost. To verify the method a simple test structure (a clampedend beam) was instrumented and experimented upon under different loading conditions. The displacements derived with the proposed method show good agreement with displacement measurements performed with a Laser Doppler Vibrometer.