A Solution to Ambiguities in Position Estimation for Solenoid Actuators by Exploiting Eddy Current Variations

Abstract

Position estimation techniques for solenoid actuators are successfully used in a wide field of applications requiring monitoring functionality without the need for additional sensors. Most techniques, which also include standstill condition, are based on the identification of the differential inductance, a parameter that exhibits high sensitivity towards position variations. The differential inductance of some actuators shows a non-monotonic dependency over the position. This leads to ambiguities in position estimation. Nevertheless, a unique position estimation in standstill condition without prior knowledge of the actuator state is highly desired. In this work, the eddy current losses inside the actuator are identified in terms of a parallel resistor and are exploited in order to solve the ambiguities in position estimation. Compared to other state-of-the-art techniques, the differential inductance and the parallel resistance are estimated online by approaches requiring low implementation and computation effort. Furthermore, a data fusion algorithm for position estimation based on a neural network is proposed. Experimental results involving a use case scenario of an end-position detection for a switching solenoid actuator prove the uniqueness, the precision and the high signal-to-noise ratio of the obtained position estimate. The proposed approach therefore allows the unique estimation of the actuator position including standstill condition suitable for low-cost applications demanding low implementation effort.

Quantitative Analysis of Insulator Degradation in a Single Layer Solenoid by Renormalization of the Transmission Parameter

“…Figure 1a shows a lumped circuit parameter model for a solenoid where L s indicates the equivalent series inductance of the solenoid, R s indicates the conductor's resistance, and C p and R i are parallel capacitance and parallel resistance, respectively. This model has been used to estimate reactance [10,13,14], and induced torque with a plunger from measured voltage and current [15] in a low-frequency range. However, it is not suitable for estimating the distributed degradation of the insulator inside a solenoid due to the limit of lumped element modeling itself.…”

“…Since the Z 0 in Equation ( 14) is the reference impedance in the VNA (50 Ω), the input impedance Z in can be calculated, of course, and reversely the Z 0 can be calculated for a given input impedance value. If we need to convert Z in into the solenoid impedance, that is, if we need the input impedance Z in to be matched to the solenoid impedance, the new Z 0 can be calculated using Equation (14). Since the measured S-parameter is based on the reference impedance of 50 Ω, it can be converted into new S-parameter based on the new Z 0 , which is calculated using Equation (14).…”

“…If we need to convert Z in into the solenoid impedance, that is, if we need the input impedance Z in to be matched to the solenoid impedance, the new Z 0 can be calculated using Equation (14). Since the measured S-parameter is based on the reference impedance of 50 Ω, it can be converted into new S-parameter based on the new Z 0 , which is calculated using Equation (14). In the equation, l coax is 18 mm, and l SW is 14 mm, respectively, and if Z C,coax = Z C,SW = Z 0 , then we have Z in = Z 0 , as expected.…”

“…In the equation, l coax is 18 mm, and l SW is 14 mm, respectively, and if Z C,coax = Z C,SW = Z 0 , then we have Z in = Z 0 , as expected. S sol in Figure 5b represents the de-embedded S-parameter of the solenoid using Equation (14). Keysight's E5061B model of the vector network analyzer was used for the two-port measurement, and the measurement was performed with 1601 points from 1 kHz to 250 MHz on a linear scale.…”

A Self-Sensing Method for Electromagnetic Actuators with Hysteresis Compensation

“…State-of-the-art self-sensing techniques for reluctance actuators mainly exploit three physical quantities: the back-induced voltage of the actuator during motion [8,9], the differential respectively the incremental inductance [5,[10][11][12][13][14][15][16][17][18][19][20][21][22][23] as well as the eddy current losses [24][25][26][27]. Methods based on the back-induced voltage usually apply an observer for position tracking.…”