EtherCAT-based connected servo drive using fast current loop on PMSM
Modern AC servo drives, depending on the end application, need high-bandwidth current control and speed control to enable superior performance, such as in CNC machines or in fast and precision control applications. Because of the highly time critical computational burden of these systems and the need for flexible PWMs, a combination of FPGAs, fast external ADCs, and multiple MCUs are used by many designers.
With the TMS320F2838x MCU, due to its higher level of integration, it is possible to implement fast current loop (FCL) algorithms that provide a high current loop bandwidth with the same external hardware as used in classical FOC methods. TI has developed the FCL algorithm on this MCU and implemented it on the Design DRIVE IDDK platform.
With a 10kHz PWM carrier, the current loop gain crossover frequency is expected to exceed 3kHz, and the closed loop bandwidth is expected at about 5 KHz (per NEMA ICS 16 and Chinese GBT 16439-2009 guidelines) and the maximum duty cycle is expected to be approximately 96%.
Using TI's Software Frequency Response Analyzer (SFRA) library, frequency response analysis of the current loops can be performed in real time to verify the above benchmarks. 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.
To read the full paper from Texas Instruments, click here.
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