Angular displacement sensor plays an indispensable role in high-precision angular measurement and position feedback. With the development of sensing technology, some traditional incremental measurement methods have been unable to meet the requirements such as anti-interference ability, lossless of power-off data information and other factors that are susceptible to environment and mechanical system changes. Therefore, this paper has proposed a method based on combined measurement for absolute measurement of time-grating angular displacement sensor, which is mainly assembling two time-grating sensors that use different pole pair in a co-prime relationship on the axis. By this method, it can build high-precision and high-resolution sensor that meets vernier-subdivision principle in the form of a combination of "fine sensor and fine sensor". The sensor model and simulation experiment results are introduced by Inventor 2016 and ANSYS Maxwell 16.0, respectively. Then, the absolute position measurement method is validated by analyzing the initial phase of the induced electromotive force of the simulation experiment results with the mathematical method. Experiment results show the absolute measurement method is feasible.
The precision measurement of two-dimensional displacements is needed in many domains, such as precision fabrication and detection. This paper presents a novel inductive position sensor with the capability of measuring displacements in x- and y- directions simultaneously. The sensor consists of two parts: a ferromagnetic plate with primary windings which are composed of four layers of planar coils, a ferromagnetic plate with secondary windings which are composed of four layers of planar coils. Primary windings are supplied with two orthogonal 20KHz alternating current to generate traveling wave magnetic field along x- and y- directions separately. Secondary windings output two signals whose phases are proportional to linear displacements of X and Y directions respectively. The structure and working principles of the sensor are proposed. Meanwhile, a sensor model is simulated to verify the feasibility of the working principle and a sensor prototype is fabricated for physical experiment. According to the analysis of experiment results, the measurement range is 140mm×140mm, and the maximum linearity in one pitch is 1%. The performance of sensor may be improved by optimizing the layout of primary and secondary windings and signal processing circuit.
The magnetoresistance(MR) sensor has been successfully demonstrated in rotational speed and position detection, however, the uneven magnetic field or the installation eccentricity are all decrease the signal quality and influence the reliability of measurement. Therefore, this paper presents the theory of time grating in displacement calculation and proposes a reverse compensation method using multi-groups sensor to improve measurement performance. A pair of linear tunnel magnetorsistance (TMR) sensors are spatially displaced by 90° electrical and excited by sin or cos signals. Another pair of sensors is reversed and diametrically apart to the former. A compensated traveling wave is got whose phase is proportional to the displacement of rotation. The angle displacement is measured by counting the time pulses that serve as measurement standards. The effectiveness of the proposed scheme is verified through a prototype permanent magnet motor system. That shows the amplitude of the measurement error from 0.17° to 0.04°, which reduces 75% by the special arrangement of the multi-groups TMR sensor. Even though the magnetic sensor presented here uses TMR sensors, the proposed technique is suited without any modification for Hall and other MR sensors as well.