Experimental Verification of a Practical Digital Driver With Switched Gain-Tuning for Five-Phase Stepping-Motors

Abstract

A digital driver that has a switched self-tuning gain in its current regulator is designed for five-phase stepping motors so that their performance could be improved and adjusted more easily, than with an analog driver. The regulator has a fixed gain block in its feedback loop and an adjustable gain in the feedforward path, replacing the integrator and the high gain that were required in previous designs to achieve good steady-state performance and fast response. Extensive experiments have been conducted under typical and extreme actuation conditions, and revealed that the proposed driver performs better than the analog drivers or their discretized equivalents, especially in eliminating undershoots, which were problematic with previous drivers.

Digital Control of a Stepping Motor for Eliminating Rotation Speed Fluctuations Using Adaptive Gains

“…In this paper, as a countermeasure to this problem, we use a control structure that is an extension of the constant current control method with variable adaptive gain proposed by Yagi et al [16]. This control structure is a two-degrees-of-freedom system, and after creating a stable closed-loop system, the characteristics of the entire system can be changed by adjusting the gain in the adaptive mechanism, which is the outer loop.…”

“…As a countermeasure to this problem, the integral adjustment law of the adaptive mechanism suppresses the windup by using a switch with a threshold value of u sat , the saturation value of the plant input. This switching structure prevents the adaptive gain from diverging [16].…”

“…The function V k defined by ( 22) is positive definite and its derivative is negative definite, thus, V k is a Lyapunov function, and η k → 0, i.e., ζ k → 0 is guaranteed. Therefore, satisfying with the condition of |u k | < |u sat | and using (16) as the executable of the variable gain update rule defined in (26), the convergence of (15) to 0 is guaranteed for all T.…”

“…However, these so-called digital controllers are just an implementation of the conventional analog controllers on a computer. Recently, Yagi et al proposed a digital current control method for a stepping motor using an adaptive gain tuning [16]. This method allows a control system designer to focus only on the transient response of the plant output to remove the steady-state deviation, without considering the internal model principle [17] for the closed-loop system.…”