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Renesas RX62T Application Note
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Renesas RX62T Application Note

Renesas RX62T Application Note

120-degree trapezoidal-wave with sensorless
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RX62T
120-degree Trapezoidal-wave with Sensorless
Introduction
This document provides an idea that using back Electromotive Force (back-EMF) signal to realize sensorless control.
Without any sensor signal input, the rotor's location is unknown, so driving rotor to get PWM pulse via six-step
trapezoidal control method phase by phase for startup period, once the BEMF is captured by MCU successfully, change
back-EMF signal as input signal source. The control algorithm and experimental result are shown in the following
chapters.
The reader should already have some understanding of six-step commutation methods, such as Hall sensor commutation,
to provide background to the techniques described here. Besides, please read the six-step motor drive with Hall sensor
application note referred to in the Reference section at the end of this document.
Target Device
RX62T
Contents
 
1.
System Configuration ........................................................................................................................ 2
 
2.
Block Diagram ................................................................................................................................... 3
 
3.
Idea for Capturing BEMF Signal ....................................................................................................... 4
 
4.
Flowchart ........................................................................................................................................... 6
 
5.
Implementation and Testing ............................................................................................................ 11
 
6.
Reference ........................................................................................................................................ 13
R01AN1192ET0100 Rev.1.00
Jun 01, 2012
APPLICATION NOTE
R01AN1192ET0100
Rev.1.00
Jun 01, 2012
Page 1 of 14
 
 
 
 
 
 

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Summary of Contents for Renesas RX62T

  • Page 1: Table Of Contents

    APPLICATION NOTE RX62T R01AN1192ET0100 Rev.1.00 120-degree Trapezoidal-wave with Sensorless Jun 01, 2012 Introduction This document provides an idea that using back Electromotive Force (back-EMF) signal to realize sensorless control. Without any sensor signal input, the rotor’s location is unknown, so driving rotor to get PWM pulse via six-step trapezoidal control method phase by phase for startup period, once the BEMF is captured by MCU successfully, change back-EMF signal as input signal source.

  • Page 2: System Configuration

    120-degree Trapezoidal-wave with Sensorless System Configuration Target board is RX62T Motor Control Development Board designed by Renesas Electronics Taiwan. Table 1-1 lists the jumper setting that switch input signal as BEMF source, which will be compared by V /2 and input into RX62T. Use three timer channels to realize this sensorless control.

  • Page 3: Block Diagram

    RX62T 120-degree Trapezoidal-wave with Sensorless Block Diagram MTU3 is the main module that is used in this application. Ch3 and ch4 are used for PWM output, which is set as reset- synchronized mode. Ch2 is used for calculating rotational speed. Ch0, ch6 and ch7 are used for calculating BEMF signal which is generated by phase U, V, and W.

  • Page 4: Idea For Capturing Bemf Signal

    RX62T 120-degree Trapezoidal-wave with Sensorless Idea for Capturing BEMF Signal Without any hall sensor detection, BEMF is one of many possible methods for sensorless control. In this application note, it is used to realize sensorless control. As shown in Figure 3-1, Phase U BEMF is an example for explanation.
  • Page 5 RX62T 120-degree Trapezoidal-wave with Sensorless Figure 3-2 Calculation of Fictitious Signal *1 ‘Temp’ value in Figure 3-2 is an example for explanation. The value should be performed in realistic condition. Three phases BEMF relationship is shown in Figure 3-3. Red arrow ( ) indicates the rising edge of fictitious hall signal timing.

  • Page 6: Flowchart

    RX62T 120-degree Trapezoidal-wave with Sensorless Flowchart Chapter 4 shows setting procedure of main, PWM, and BEMF in sample program. In addition, speed calculation method is also described in this chapter, too. Main: [1] After power on reset, initial the peripheral function in hardware setup.
  • Page 7 RX62T 120-degree Trapezoidal-wave with Sensorless Figure 4-3 shows the PWM duty output setting procedure that includes no BEMF signal input (i.e. open-loop control), and BEMF signal input (i.e. close-loop control). MTU3, MTU4 PWM Interrupt [1] Check the hall location with previous saved value...
  • Page 8 RX62T 120-degree Trapezoidal-wave with Sensorless Procedure ‘A’: [1] Because the rotor’s location is unknown, we enable one phase PWM to constrain rotor at a fixed location. [2] Check spinning direction. If changed, output higher PWM duty to force rotor’s location.
  • Page 9 RX62T 120-degree Trapezoidal-wave with Sensorless Procedure ‘C’: [1] After changing Motor status to ‘Close Loop Control’, PWM duty will be calculated according to rotational speed. [2] Check direction. If changed, turn off the PWM output and set Motor Status to ‘STOP’ to restart.
  • Page 10 RX62T 120-degree Trapezoidal-wave with Sensorless Three phase BEMF signals are used the same procedure, and idea for this flowchart please see Chapter 3. BEMF process [1] Count operation is stopped, k = U, V, W. [2] Check counter value bigger than 500, and save counter value in different conditions happened.

  • Page 11: Implementation And Testing

    Timer Used channel Input BUS voltage Table 5-1 Capability of RX62T Motor Control Development Board Figure 5-2 is the relation between three phase fictitious hall signals and phase U current. And rotational speed is 3021 rpm with loading. R01AN1192ET0100 Rev.1.00...
  • Page 12 RX62T 120-degree Trapezoidal-wave with Sensorless Phase U Current Hall A Hall B Hall C Figure 5-2 Phase U Current with Loading Figure 5-3 shows three phase BEMF signal. Phase U Phase V Phase W Figure 5-3 Three Phase BEMF Signal R01AN1192ET0100 Rev.1.00...

  • Page 13: Reference

    Application Notes REU05B0074-0100/Rev 1.00 Six-Step Trapezoidal Control of a BLDC Motor Using Hall Sensors Hardware Manual RX62T Group, Hardware Manual Rev. 1.3 (Use the latest version on the home page: http://www.renesas.com) R01AN1192ET0100 Rev.1.00 Page 13 of 14 Jun 01, 2012...
  • Page 14 RX62T 120-degree Trapezoidal-wave with Sensorless Website and Support Renesas Electronics Website http://www.renesas.com/ Inquiries http://www.renesas.com/inquiry All trademarks and registered trademarks are the property of their respective owners. R01AN1192ET0100 Rev.1.00 Page 14 of 14 Jun 01, 2012...
  • Page 15 Revision Record Description Rev. Date Page Summary 1.00 Jun.01.12 — First edition issued...
  • Page 16 General Precautions in the Handling of MPU/MCU Products The following usage notes are applicable to all MPU/MCU products from Renesas. For detailed usage notes on the products covered by this document, refer to the relevant sections of the document as well as any technical updates that have been issued for the products.
  • Page 17 "Specific" without the prior written consent of Renesas Electronics. Further, you may not use any Renesas Electronics product for any application for which it is not intended without the prior written consent of Renesas Electronics. Renesas Electronics shall not be in any way liable for any damages or losses incurred by you or third parties arising from the use of any Renesas Electronics product for an application categorized as "Specific"...