Measurement and Control of Solenoid Stroke using Its Electrical Characteristics

TL;DR

The work addresses non-contact measurement and control of solenoid stroke by exploiting the position dependence of inductance, using $x_P = -0.0843 L + 9.656$ to estimate plunger position from inductance. It develops a PWM-based inductance measurement strategy, including explicit current relations $I_1^E$ and $I_1^S$ as functions of $R_s$, $L_s$, $V_s$, $T$, and $T_1$, and introduces bilinear interpolation on a precomputed $I(T_1,L_s)$ table to estimate $L_s$ and thus $x_P$. The approach is validated experimentally with an Arduino setup, revealing practical considerations such as non-ideal diode effects and sensitivity to PWM timing. A simple PID-like control then uses the estimated position to adjust PWM duty to reach intermediate target strokes, though mechanical dynamics cause overshoot and oscillation, highlighting avenues for refinement and temperature-dependent effects in future work.

Abstract

In this paper, we describe the algorithm to measure the stroke of solenoid using the electric characteristics of the solenoid, without mechanical attachments. We also describe the experimental results of controlling the solenoid stroke at intermediate position.

Figures (16)

• Figure 1: Solenoid (Takaha's CBS07300580)
• Figure 2: Equivalent circuit of solenoid
• Figure 3: Measured induncance and plunger position
• Figure 4: Driving circuit of solenoid
• Figure 5: Equivalent Circuit for OFF-to-ON transition