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 Rotary Angle Accuracy Measurement

In this section, the angle accuracy when the motor is running on constant speed is tested. On test platform, the servo motor drives the tested motor at 30RPM. The host controller can send position data request command at 16kHz frequency and collect the reference encoder and TIDA-010947 position data. Compare the reference encoder and TIDA-010947 data to get the rotary angle accuracy.

For help simulating magnetic systems, the TI Magnetic Sense Simulator (TIMSS) tool can accelerate design and evaluation of magnetics systems.

Keep the airgap at 0.8mm and collect 30000 angle samples over one revolution. The rotary accuracy is shown in Figure 4-14. The peak to peak error is 0.28° without any offset and gain calibration. By using post-calibration to compensate 1st and 2nd harmonic, the error can be reduced to +/-0.032°, which is shown in Figure 4-14.

TIDA-010947 Uncalibrated Rotary Angle Accuracy at 0.8mm AirgapFigure 4-14 Uncalibrated Rotary Angle Accuracy at 0.8mm Airgap
TIDA-010947 Rotary Angle Accuracy with Offset Calibration at 25°C AmbientFigure 4-15 Rotary Angle Accuracy with Offset Calibration at 25°C Ambient

To do the repeatability test, continuously sample the angle data over two revolutions. After using same calibration parameter, compare the calibration results of two cycles. Figure 4-16 shows the results. Cycle1 and cycle2 data almost complete overlap, this means the good repeatability of TIDA-010947.

TIDA-010947 Rotary Angle Accuracy with Offset Calibration at 25°C Ambient, Repeated Test RunFigure 4-16 Rotary Angle Accuracy with Offset Calibration at 25°C Ambient, Repeated Test Run