8 Introduction

The rotor speed and position estimation are not reliable when the motor runs at low speeds. Hence, rotor speed and position information cannot be used to control the motor at start-up and low speeds in sensor-less mode. The motor must be started with a forced angle (open-loop angle) instead of an estimated angle. The open-loop angle, along with the current reference generation, is managed by the Open-Loop Manager.

The Open-Loop Manager performs the following functions:

  • Generates open-loop angle based on the following equation:

where,

θ is the angle generated

ω* is the speed reference input

θbuffer is the previous theta (generated angle) value

θfactor is a constant

scale is a scaling value

  • Switches the angle between open-loop angle and estimated angle based on closed-loop status
  • Generates init values for speed and Iq PI controllers based on direction.
Note: θ factor is computed as:

where,

Nrpm is rated motor speed in RPM

Npp is number of pole pairs

fsw is switching frequency

Summary

Core VersionThis document applies to Open-Loop Manager v4.2.
Supported Device Families
  • PolarFire® SoC
  • PolarFire
  • RTG4™
  • IGLOO® 2
  • SmartFusion® 2
Supported Tool FlowRequires Libero® SoC v11.8 or later releases.
LicensingComplete encrypted RTL code is provided for the core, enabling the core to be instantiated with SmartDesign. Simulation, Synthesis, and Layout can be performed with Libero software. Open-Loop Manager is licensed with encrypted RTL that must be purchased separately. For more information, see Open-Loop Manager.

Features

Open-Loop Manager has the following key features:

  • At low speeds, it computes the rotor speed and its position
  • Transition from open-loop speed to closed-loop speed based on closed-loop status input

Implementation of IP Core in Libero Design Suite

IP core must be installed to the IP Catalog of the Libero® SoC software. This is done automatically through the IP Catalog update function in the Libero SoC software, or the IP core can be manually downloaded from the catalog. Once the IP core is installed in the Libero SoC software IP Catalog, the core can be configured, generated, and instantiated within the SmartDesign tool for inclusion in the Libero project list.