Rosenheim University of Applied Sciences: Fast Control for Three-Phase Synchronous Motors with an EnDat 2.2 Interface on MicroLabBox

One field of research at the Electrical Drive Technology laboratory of the Rosenheim University of Applied Sciences is closed and open open loop controls for servo drives. The algorithms are developed entirely model-based with MATLAB^®/Simulink^®. For rapid control prototyping, several dSPACE systems are used. One subproject addresses the closed loop control of a permanently excited three-phase synchronous motor.

Previously, existing dSPACE systems were used with motors that included incremental encoders which provided analog sinusoidal output signals with signal levels of 1 V_ss. Position measurement devices with a serial interface offer many advantages compared to devices with analog signal transmission. The EnDat 2.2 interface provides numerous benefits, including very short times for position value determination and transmission, automatic commissioning as well as comprehensive functions for diagnostics and functional safety. This is why incremental encoders with an EnDat 2.2 interface were integrated in existing test setups to be able to directly compare analog and digital signal transmission of position information in servo drives with very wide control ranges.

A dSPACE MicroLabBox and the EnDat block of the RTI Electric Motor Control Blockset enabled the researchers to read the position values of the encoders after a very short time with the maximum data rate of 16 MHz. These position values are currently being used as the basis for putting into operation commissioning a field-oriented current control for permanently excited three-phase synchronous motors.

The customer-specific motor control was implemented on the freely programmable FPGA of the MicroLabBox to achieve the fastest possible control sampling rate. This enabled the Rosenheim University of Applied Sciences to rapidly develop both the processor-based part of the controller and the parts executed on the FPGA with a model-based approach. For this, the RTI Electric Motor Control Blockset can be used in combination with the RTI FPGA Programming Blockset.

By using a MicroLabBox with the RTI Electric Motor Control Blockset and the RTI FPGA Programming Blockset, the researchers at the university were able to add the state-of-the-art EnDat 2.2 interface to their lab setup in a very short time and thus quickly perform the first comparison measurements between analog and digital encoders in a real environment.

Alexander Kiermayer is a research associate in the Electrical Drive Technology laboratory of the Rosenheim University of Applied Sciences.