Enhancing MPS Signal by Bipolar Pulse Excitation and Interference of Reflection Wave

Abstract

To enhance the signal intensity of magnetostrictive position sensor (MPS), a new method of bipolar pulse excitation (BPE), and a new structure of single-end damper (SED) are proposed in this paper. Two torsion strain waves, named as W1 and W2 waves, are generated by the BPE, and the W1 wave is reflected (changed into RW1) by the SED. Based on the principle of wave superposition, the interference between RW1 and W2 is realized by adjusting the structure parameters of the sensor. Therefore, the MPS signal is strengthened 1.8 times approximately as well as the measuring range. The notable difference between the new strategy and the conventional one lies in the reflection wave. In conventional MPS, the smaller the reflection wave is, the better the signal will be. However, the reflection wave should be as strong as possible in the new strategy. After the explanation of BPE and SED, a new model is presented. The validity and feasibility of the proposed strategy are verified by experiments. Finally, the characteristics of BPE and SED, such as the measured object, the polar of excitation pulse, and the limit of signal, are discussed in detail. Research results indicate that the proposed BPE method and SED structure are innovative development to conventional MPS, and are of great practical value.Index Terms-Magnetostrictive position sensor (MPS), measuring range expansion, signal enhancement, torsion strain wave, wave interference.

Magnetic position sensors

“…The hysteresis may be as low as 0.4 µm, uncorrected linearity is 0.02% FS, and some devices have an internal linearization and temperature compensation. The maximum sensor length is limited by elastic wave attenuation to about 4 m [85,86]. Sensors based on similar principles are manufactured by Gemco-Patriot, MTS, and Balluff.…”

“…Magnetostrictive position sensors can simultaneously measure velocity by the eddy current principle. The independent velocity information can be used for consistency checking (self-diagnostics) or the improvement of the position measurement by signal fusion [86,90]. Some attempts were made to utilize domain wall movement for the position measurement, but this effect is too dependent on external magnetic field and stress.…”

Parameter Optimization of Magnetostrictive Linear Displacement Transducer

“…The Dependence of the sensing coil output voltage pulse on the exciting current pulse amplitude for used waveguide material 4J50 have been conducted [8]. Wave interference method is used to increase the sensing element output signal amplitude [9][10][11]. By using constructive interference among undamped torsional waves that propagate along the magnetostrictive waveguide, the output signal amplitude of the sensing coil is increased [9].…”

“…Wave array interference method using a structure that consists of multi-pulses and multi-cursors has been adopted in [10]. By adopting bipolar excitation and single-end damper structure, wave interference method using reflected wave is realized [11]. High precision time interval measurement using CPLD is adopted to improve the measurement resolution [12].…”