JAJU837 March   2022

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TMAG5170
      2. 2.2.2 DRV5055A4
    3. 2.3 Design Considerations
      1. 2.3.1 Magnet Selection
      2. 2.3.2 Magnet Shape
      3. 2.3.3 Magnet Rotation Speed
      4. 2.3.4 Sensor Location
      5. 2.3.5 Expected Performance
      6. 2.3.6 Layout for Sensor Location
      7. 2.3.7 45° Alignment
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
      1. 3.2.1 Test Equipment
      2. 3.2.2 Test Hardware Configuration
      3. 3.2.3 Test Software Configuration and Initial Data Capture
    3. 3.3 Test Results
      1. 3.3.1 Calibration Methods
      2. 3.3.2 TMAG5170 On-Axis
      3. 3.3.3 TMAG5170 In-Plane
      4. 3.3.4 TMAG5170 Off-Axis
      5. 3.3.5 TMAG5170 45° Alignment
      6. 3.3.6 DRV5055 Off Axis Result
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 サポート・リソース
    5. 4.5 Trademarks

Magnet Rotation Speed

As the speed of the motorized system increases, this impacts a fixed-phase delay error from the sensor due to the actual propagation delay in the system. The ability of the controller to manage this delay impacts device settings and end performance.

For instance, TMAG5170 offers averaging modes which can help improve the observed input referred noise. Minimizing this noise helps achieve the highest accuracy result, but proportionally increases the overall integration time. This increase in integration time determines the resulting phase-related error.

AVERAGING MODESAMPLING PATTERNTOTAL CONVERSION TIME
1 ×

XY

75 μs

32 ×

XY

1.625 ms

1 ×

XYZZYX

175 μs

32 ×

XYZZYX

4.825 ms

This integration delay can cause speed limitations for a sensor. In the case of the 32 × sampling using the XYZZYX conversion pattern, the total integration time is 4.825 ms. At a motor speed of about 35 RPM, the magnet will rotate 1° over the duration of a single conversion. By contrast, comparing the fastest integration time of 75 μs, the magnet would have to spin 64 × faster to similarly rotate by 1° during one conversion.

For any motor, especially when loaded, there must be a deceleration period as the shaft approaches the target position. It is necessary, therefore, to understand the phase delay to predict when to begin the deceleration. As the shaft speed is increased or decreased, the system must account for this delay to accurately understand the actual motor position.

While increased averaging reduces the impact of noise on the measurement, Figure 2-3 demonstrates that the increased sample time results in a greater discrepancy between actual motor shaft angle and the collected data from the sensor.

Figure 2-3 Angle Phase Error vs Motor Speed