Introduction
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SPRA605A–February 2000–Revised August 2017
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TMS320F240 DSP Solution for Obtaining Resolver Angular Position and
Speed
5.3 PGA411-Q1 Software Design ................................................................................... 16
5.4 PGA411-Q1 Troubleshooting Guide ........................................................................... 16
5.5 PGA411-Q1 System Modelling in MATLAB Simulink ........................................................ 17
6 TMS320F240 Results...................................................................................................... 17
6.1 Processor Utilization .............................................................................................. 17
6.2 Angular Accuracy and Transient Response ................................................................... 17
7 Conclusion .................................................................................................................. 19
8 References - make clickable links ....................................................................................... 20
List of Figures
1 Resolver, Simplified Functional Diagram and Corresponding Signals................................................ 3
2 Amplitude Spectrum of the Resolver Signals u
1
, u
2
..................................................................... 4
3 Resolver-to-Digital Conversion Using Undersampling and Inverse Tangent ........................................ 4
4 Block Diagram of the Improved Resolver-to-Digital Converter ........................................................ 5
5 FIR Decimation Bandpass Filter Magnitude Response................................................................. 6
6 Angular Error as Function of the Rotational Speed After the FIR Filter .............................................. 7
7 Closed-Loop Position and Speed Interpolator ........................................................................... 7
8 Functional Block Diagram of the TMS320F240 R/D Converter Realization ......................................... 8
9 Signal Conditioning for Resolver to TMS320F240 Interface ........................................................... 9
10 Signal Conditioning for Single-Ended Resolver Signals .............................................................. 10
11 Flowchart of timer3_int .................................................................................................... 12
12 Magnitude Response of the 17-Tap FIR Filter ......................................................................... 14
13 Closed-Loop Angle and Speed Interpolator ............................................................................ 15
14 Normalized Step Response of the Interpolated Angle ................................................................ 15
15 Measured Normalized Step Response for a 1º Angular Step (1º ~ 180) ........................................... 18
16 Resolver Angular Position and Angular Speed ........................................................................ 18
17 Angular Position Error for a Speed Reversal From –180 rpm to +180 rpm ........................................ 19
18 As , but Y-Axis Zoomed ................................................................................................... 19
List of Tables
1 Source Modules and Functional Description ........................................................................... 10
2 Angular Resolution and Bandwidth as Function of KI and KP ....................................................... 16
3 TMS320F240 CPU Loading .............................................................................................. 17
4 TITLE NEEDED ............................................................................................................ 18
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1 Introduction
Digital signal processors are going to become more common in digital motor control applications. They
permit sophisticated real-time control applications to be implemented, which improve dynamic response,
precision, and efficiency. In addition, they enable sensorless control, which reduces total system operating
by eliminating mechanical sensors.
TMS320F240 has been successfully used in sensorless applications. Mechanical sensors, which provide
information on speed or position of the drive, can be eliminated and replaced by high-sophisticated
position and speed estimation algorithms. Typical estimation algorithms include Extended-Kalman-Filters,
INFORM, and Sliding Mode Observers. A further cost reduction can be achieved by the elimination of
phase current sensors by a new algorithm that estimates the actual value of the three phase currents
using only the DC-link current with a shunt resistor. However, there are still applications where sensorless
control cannot achieve the required accuracy and reliability. This is especially true with respect to the
angular position. Examples include servo applications, like robotics and numerically-controlled machine
tools. Mechanical sensors used there are usually incremental encoders and resolvers. Incremental TTL-
encoders provide a pulse train, where each pulse is equivalent to an incremental step. Incremental