TIDUF97 September   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 TMAG6180-Q1
      2. 2.3.2 MSPM0G3507
      3. 2.3.3 THVD1454
  9. 3System Design Theory
    1. 3.1 Hardware Design
      1. 3.1.1 Angle Sensor Schematic Design
      2. 3.1.2 MSPM0G3507 Schematic Design
      3. 3.1.3 RS485 Transceiver Schematic Design
      4. 3.1.4 Power Supply and Reference Voltage
    2. 3.2 Software Design
      1. 3.2.1 Angle Calculation Timing
      2. 3.2.2 Rotary Angle Calculation
      3. 3.2.3 Rotary Angle Error Sources and Compensation
      4. 3.2.4 Encoder Communication Interface
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
      1. 4.1.1 PCB Overview
      2. 4.1.2 Encoder and JTAG Interface
      3. 4.1.3 Software Requirements
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 AMR Sensor Sin and Cos Outputs Measurement
      2. 4.3.2 Static Angle Noise Measurement
      3. 4.3.3 Rotary Angle Accuracy Measurement
        1. 4.3.3.1 Impact of Airgap on Noise, Harmonics, and Total Angle Accuracy
      4. 4.3.4 RS485 Interface and Signal Integrity
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout
      4. 5.1.4 Altium Project Files
      5. 5.1.5 Gerber Files
      6. 5.1.6 Assembly Drawings
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Authors

4.3.3.1 Impact of Airgap on Noise, Harmonics, and Total Angle Accuracy

With the airgap increasing, the magnetic field can reduce and leads to higher noise of position sensor. This section analyzes the airgap’s influence on TIDA-010947. By using gasket, the airgap changes from 0.3mm to 2.3mm. Repeat the test procedure described in Section 4.3.3, the test results are shown in Figure 4-17 to Figure 4-20. Under all airgap, the error with calibration are lower than ±0.037°.

TIDA-010947 Uncalibrated Rotary Angle Accuracy with Calibration at 0.8mm AirgapFigure 4-17 Uncalibrated Rotary Angle Accuracy with Calibration at 0.8mm Airgap
TIDA-010947 Rotary Angle Accuracy with Calibration at 0.8mm AirgapFigure 4-18 Rotary Angle Accuracy with Calibration at 0.8mm Airgap
TIDA-010947 Rotary Angle Accuracy with Calibration at 1.3mm AirgapFigure 4-19 Rotary Angle Accuracy with Calibration at 1.3mm Airgap
TIDA-010947 Rotary Angle Accuracy with Calibration at 2.3mm AirgapFigure 4-20 Rotary Angle Accuracy with Calibration at 2.3mm Airgap

To further analyze the airgap influence on harmonics, FFT analysis is used. The results are listed on the Table 4-9. 4th harmonic is from signal chain gain mismatch, which is not influenced by airgap. 8th harmonic is caused by AMR sensor and signal chain's non linearity, higher airgap can lead to increasing value of the 8th harmonic.

Table 4-9 Angle Error and Harmonics vs Airgap
Airgap Offset calibrated angle error [°] 4th harmonic [°] 8th harmonic [°]
0.3mm <0.04° 0.0086 0.0015
0.8mm <0.04° 0.006 0.0012
1.3mm <0.04° 0.0062 0.0041
2.3mm <0.04° 0.0058 0.0113