SPRACO3 October   2019 INA240 , LMG5200 , TMS320F280021 , TMS320F280021-Q1 , TMS320F280023 , TMS320F280023-Q1 , TMS320F280023C , TMS320F280025 , TMS320F280025-Q1 , TMS320F280025C , TMS320F280025C-Q1 , TMS320F280040-Q1 , TMS320F280040C-Q1 , TMS320F280041 , TMS320F280041-Q1 , TMS320F280041C , TMS320F280041C-Q1 , TMS320F280045 , TMS320F280048-Q1 , TMS320F280048C-Q1 , TMS320F280049 , TMS320F280049-Q1 , TMS320F280049C , TMS320F280049C-Q1 , TMS320F28374D , TMS320F28374S , TMS320F28375D , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376D , TMS320F28376S , TMS320F28377D , TMS320F28377D-EP , TMS320F28377D-Q1 , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378D , TMS320F28378S , TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379S

 

  1.   Dual-Axis Motor Control Using FCL and SFRA On a Single C2000 MCU
    1.     Trademarks
    2. 1 Introduction
      1. 1.1 Acronyms and Descriptions
    3. 2 Benefits of the C2000 for High-Bandwidth Current Loop
    4. 3 Current Loops in Servo Drives
    5. 4 PWM Update Latency for Dual Motor
    6. 5 Outline of the Fast Current Loop Library
    7. 6 Evaluation Platform Setup
      1. 6.1 Hardware
        1. 6.1.1 LAUNCHXL-F28379D or LAUNCHXL-F280049C
          1. 6.1.1.1 DACs
          2. 6.1.1.2 QEPs
        2. 6.1.2 Inverter BoosterPack - GaN + INA240
        3. 6.1.3 Two Motor Dyno
        4. 6.1.4 System Hardware Connections
        5. 6.1.5 Powering Up the Setup
      2. 6.2 Software
        1. 6.2.1 Incremental Build
        2. 6.2.2 Software Setup for Dual-Axis Servo Drive Projects
    8. 7 System Software Integration and Testing
      1. 7.1 Incremental Build Level 1
        1. 7.1.1 SVGEN Test
        2. 7.1.2 Testing SVGEN With DACs
        3. 7.1.3 Inverter Functionality Verification
      2. 7.2 Incremental Build Level 2
        1. 7.2.1 Connecting motor to INVs
        2. 7.2.2 Testing the Motors and INVs
        3. 7.2.3 Setting Over-current Limit in the Software
        4. 7.2.4 Setting Current Regulator Limits
        5. 7.2.5 Position Encoder Feedback
      3. 7.3 Incremental Build Level 3
        1. 7.3.1 Observation One – Latency
      4. 7.4 Incremental Build Level 4
        1. 7.4.1 Observation
        2. 7.4.2 Dual Motor Run With Speed Loop
      5. 7.5 Incremental Build Level 5
        1. 7.5.1 Dual Motor Run with Position Loop
      6. 7.6 Incremental Build Level 6
        1. 7.6.1 Integrating SFRA Library
        2. 7.6.2 Initial Setup Before Starting SFRA
        3. 7.6.3 SFRA GUIs
        4. 7.6.4 Setting Up the GUIs to Connect to Target Platform
        5. 7.6.5 Running the SFRA GUIs
        6. 7.6.6 Influence of Current Feedback SNR
        7. 7.6.7 Inferences
        8. 7.6.8 Phase Margin vs Gain Crossover Frequency
    9. 8 Summary
    10. 9 References

1 Introduction

High performance motor drives in servo control and robotics applications are expected to provide high precision and high bandwidth control of current, speed and position loops for superior control of end applications such as robotic arm, CNC machines, and so forth. Since the current loop makes up the inner most control loop, it must have a high bandwidth to enable the outer speed or position loops to be faster. Hence, a high bandwidth FCL is needed in high performance industrial servo control applications. However, the delays due to ADC conversion and algorithm execution limit the current controller bandwidth to about a tenth of the sampling frequency.

Until recently, because of the time critical computational demand of the control algorithm and interface demands of various position encoders, FPGAs and external ADCs were needed to implement the fast current loop. However, with the advent of latest C2000 Delfino and Piccolo family of microcontrollers, it is now possible to replace FPGAs and external ADCs with these MCUs for a cost effective solution. This paper outlines the implementation of fast current loop on a C2000 platform running two motors, and verifies the frequency response of the control loops using TI’s Software Frequency Response Analyzer (SFRA) software library. Dynamic frequency response analysis in real-time on a motor drive system is unique among MCU suppliers and is currently capable only on C2000 MCUs.

Using the released FCL algorithm for this device and the Software Frequency Response Analyzer (SFRA) library for C2000 MCUs from TI, the control bandwidth of fast current loop and the operating speed range of motor are experimentally verified. This design guide documents the test platform setup, procedure and the quantitative results obtained. It is important to note that when the PWM carrier frequency is 10 KHz, the current loop bandwidth obtained is 5 KHz for a phase margin of 45° over a wide speed range. Compared to the traditional MCU based systems, FCL software can potentially triple a drive system’s torque response and double its maximum speed without increasing the PWM carrier frequency.

The Delfino F2837x and Piccolo F28004x series of C2000 microcontroller enable a new value point for dual-axis drives that also delivers very robust motion-control performance. The value comes not only from the achievable control performance and ability to drive two motors concurrently, but also from the high degree of on-chip integration of other key electronic system functions. Since both F2837x and F28004x devices support CPU and CLA cores, CPU offload encoder-feedback and torque control processing to the control law accelerator (CLA) to maximize the performance of dual-axis servo drive.