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 2010 Microchip Technology Inc. DS70640A-page 1

AN1292 Tuning Guide

This document provides a step-by-step procedure on running a motor with the

algorithm described in AN1292 “Sensorless Field Oriented Control (FOC) for a

Permanent Magnet Synchronous Motor (PMSM) Using a PLL Estimator and Field

Weakening (FW)” (DS01292).

1.1 SETTING SOFTWARE PARAMETERS

All of the main configurable parameters are defined in the userparms.h file. The

adaptation of the parameters to the internal numerical format is done using the

tuning_params.xls Excel

spreadsheet (see Figure 1-1). This file is included with

the AN1292 archive file, which is available for download from the Microchip website

(www.microchip.com).

After entering the motor and hardware information into the spreadsheet, the calculated

parameters need to be entered into the userparms.h header file, as indicated by the

following steps.

FIGURE 1-1: tuning_params.xls

STEP 1 – Fill in the tuning_params.xls Excel spreadsheet with the following parameters:

a) Peak Voltage

Peak voltage represents the peak voltage on the DC link capacitors. It also

represents the DC voltage itself when a DC power supply is connected to the DC

link. If the DC link is supplied from a single-phase rectifier bridge, the AC peak

voltage is connected to the rectifier:

A 24 V

DC power supply was used in the demonstration software, so the Excel

spreadsheet contains the corresponding value. If you are using a high voltage

PMSM, peak voltage for 115 VAC is 163V.

ACpeak

ACrms

2=

Summary of content (14 pages)

PAGE 1
AN1292 Tuning Guide This document provides a step-by-step procedure on running a motor with the algorithm described in AN1292 “Sensorless Field Oriented Control (FOC) for a Permanent Magnet Synchronous Motor (PMSM) Using a PLL Estimator and Field Weakening (FW)” (DS01292). 1.1 SETTING SOFTWARE PARAMETERS All of the main configurable parameters are defined in the userparms.h file. The adaptation of the parameters to the internal numerical format is done using the tuning_params.
PAGE 2
b) Peak Current Peak current represents the maximum real value of the current that can be internally represented, which depends on the acquisition block. Considering the maximum input to the ADC of 3.3V, the gain of the acquisition circuitry and the value of the current shunts determine the maximum value of the current that will fit to the dsPIC® DSC internal number representation.
PAGE 3
AN1292 Tuning Guide e) Nominal and Maximum Speed Nominal speed is a parameter provided by the manufacturer and represents the speed achievable with the nominal current and voltage provided on the motor’s plate. Maximum speed is a parameter provided by the manufacturer and depends mostly on the mechanical parameters of the motor.
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STEP 2 – Export produced parameters to userparms.h. The resulting values in the right side columns grouped as Output parameters are to be entered in the userparms.h file corresponding definitions. Notice that the items on the Output parameters are colored differently, indicating precisely which of them are to be copied and pasted directly into the software code. userparms.h DS70640A-page 4  2010 Microchip Technology Inc.
PAGE 5
AN1292 Tuning Guide STEP 3 – First, tune the open loop a) Activate Open Loop Functioning The open loop tuning can be operated separately, by enabling a special #define in the FOC software code; otherwise, the transition to close loop control is automatically done. Make sure you disable closed loop transition for the initial tuning of open loop. userparms.
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• End Speed End speed value setup is a trade-off between the efficiency of the control and the estimator’s minimum speed limit to accurately estimate speed and position. Normally, the user would want to set the open loop end speed value as low as possible so that the transitions to closed loop functioning occur as soon as possible from the startup. Keeping in mind the compromise stated above, consider an end speed of one third of nominal speed of the motor under tuning for the beginning. userparms.
PAGE 7
AN1292 Tuning Guide • PI Current Controllers Some general guidelines for effective tuning of this application’s PI controllers are: - Both controllers, on the D and Q axis, will have the same values for corresponding Proportional (D_CURRCNTR_PTERM, Q_CURRCNTR_PTERM), Integral (D_CURRCNTR_ITERM, Q_CURRCNTR_ITERM), Anti-windup Compensation (D_CURRCNTR_CTERM, Q_CURRCNTR_ITERM), and Minimum-Maximum (D_CURRCNTR_OUTMAX, Q_CURRCNTR_OUTMAX, D_CURRCNTR_OUTMIN, Q_CURRCNTR_OUTMIN) terms.
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STEP 4 – Tuning the Closed Loop Operation a) Enable Close Loop Transition Step forward to close loop tuning once the open loop is running fine, by removing the define of the OPEN_LOOP_FUNCTIONING macro definition. userparms.h b) Set Up Close Loop Parameters • Initial Angle Offset Tuning The transition between open loop to close loop implies an initial estimation error, for which pre-selection of an initial offset angle is required: userparms.
PAGE 9
AN1292 Tuning Guide STEP 5 – Optionally, Tune the High-Speed Field Weakening Parameters CAUTION Usually, the motor manufacturer indicates the maximum speed achievable by the motor without it being damaged (which could be higher than the brake point speed at rated current). If not, it is possible to run it at higher speeds but only for small periods (intermittent) assuming the risks of demagnetization or mechanical damage of the motor or of the devices attached to it.
PAGE 10
• D-axis Current Reference D-axis reference current lookup table (ID) has values between 0 and the nominal stator current, distributed evenly on 18 entries of the lookup. The nominal stator current can be taken from the motor specification. If it is unknown, this value can be approximated by dividing the rated power over the rated voltage. userparms.
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AN1292 Tuning Guide • Inductance Variation For the inductance variation (LsOver2Ls0) lookup table, the first value in the table should always be one-half since the base speed inductance is divided by its own doubled value. These values should work for most motors. userparms.
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It is always better to have a software speed reference instead of the standard potentiometer/DMCI slider control since it is more stable and it can offer better granularity. For testing purposes, a slow software ramp is implemented as a speed reference, being activated using the following definition: userparms.h The smaller the value of the delay of ramp, the slower the ramp will increase.
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Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature.
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