Abstract For the sensorless control systems based on high-frequency (HF) signal injection in zero and low speed range, issues of harsh audible noise occur, as well as large estimation errors within the stages of acceleration and deceleration in ramp. To address the two problems, this paper proposes corresponding optimization methods. First, to remove the harsh discrete components in the responsive current and make the noise quiet and consistent, a single pair of complementary random HF pulses is injected only into the rotating estimated γ axis. Furthermore, an enhanced phase-locked loop (PLL) with a straightforward construction and simple parameter tweaking is proposed, which can eliminate transient errors completely. The accuracy and efficacy of the proposed approaches have been validated through simulation and experimental verification. Experimental results demonstrate that the proposed PLL can reduce the position error from 20° and 17.4° to zero under no-load and rated load, respectively. In addition, during the sudden removal of rated load at zero speed, the position error is reduced from 5.6° to 4.6°.
Li et al. (Mon,) studied this question.