Design and implementation of an encoder calibration system for improved resolution and accuracy in IPMSM drive with embedded software

ABSTRACT

This paper presents an encoder calibration system to enhance resolution and accuracy in an interior permanent magnet synchronous motor (IPMSM) drive, along with custom embedded software. The system implements closed-loop control with the IPMSM drive, adjusting the encoder resolution through gear ratio adjustments. Communication between the human-machine interface (HMI) and the DSP’s internal 28× CPU is achieved via digital communication RS-422 interface. The embedded software on the 28× CPU processes real-time data and displays calibration information on the HMI. Firmware integration includes external analog/digital converters, comparators, digital communication interfaces, high-accuracy encoders, original encoders, and additional gear ratio adjustments, with computed compensation values stored in EEPROM. The TMS-320F-28335 digital signal processor serves as the control core, enabling encoder signal processing, embedded software execution, HMI operation, and IPMSM drive control. The experimental results validate the practicality of the proposed digitization method, demonstrating its effective applicability in industrial control systems.

CO EDITOR-IN-CHIEF:

• Kuo, Cheng-Chien

ASSOCIATE EDITOR:

• Wang, Wen-June

KEYWORDS:

• Encoder calibration
• enhanced accuracy
• embedded software execution
• digital signal processor
• IPMSM

Nomenclature

$B_m$	=	the motor friction coefficient
$\mathit{E}(\mathit{z})$	=	the error function
$\mathit{G}(\mathit{z})$	=	the discrete transfer function
$i_d$$i_q$	=	the d-axis and q-axis currents
$J_m$	=	the motor inertia
$L_d$$L_q$	=	the d-axis and q-axis inductances
$\mathit{P}$	=	the number of poles
$r_s$	=	the motor stator resistance
$T_e$	=	the electromagnetic torque
$T_L$	=	the load torque
$\mathit{U}(\mathit{z})$	=	the output function
$v_d$$v_q$	=	the d-axis and q-axis stator voltages
${\theta }_A$${\theta }_B$	=	the actual measured position of encoder A and encoder B
${\theta }_{\bar{A}}$	=	the angle of encoder A, after compensation
$\mathit{\theta }$	=	the error amount between encoder A and encoder B
${\omega }_{\mathit{re}}$${\omega }_{\mathit{rm}}$	=	the electrical angular velocity and mechanical angular velocity of the motor shaft
${\lambda }_m$	=	the rotor equivalent flux linked

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Ministry of Science and Technology, Taiwan [112-2622-E-150-014 -].