?# Cogging Torque Measurement Rig By Alsaleh Almughir, Abdulrahman and Hemaz, Said

1) Cogging Torque Measurement Rig

The project focuses on designing and building a mechanical test rig for measuring the cogging torque in three-phase BLDC and PMSM motors. The motivation behind the project is that cogging torque ¡ª the magnetic interaction between the rotor and stator when no current is applied ¡ª causes vibration and noise in precision robots and electric vehicles. By developing an automated measurement system capable of detecting torque variations with high accuracy, we can create improved compensation models for smoother and more efficient motor control. The project combines mechanical design (CAD modeling and assembly of the rig), electronics (sensors, encoder, load cells, FPGA), and software (data acquisition, control, and torque analysis). This project directly supports one group member¡¯s master¡¯s thesis in robotics, which focuses on estimating and compensating for cogging torque.

2) Goals

The goal of this project is to build a static and semi-automated test rig capable of measuring the cogging torque in motors of various sizes.

The rig will: ? Measure torque as a function of rotor angle using load cells and an encoder. ? Be able to test motors of different sizes and types.

Optimization: The software will be optimized to filter noise from the load cells and calculate the torque curve more accurately. In addition, the collected data will be analyzed to identify patterns in the cogging torque.

Inspiration: The design of the measurement setup was inspired by the article ¡°Automated Laboratory Stand for Determining the Cogging Torque of a Small Permanent Magnet Electric Machine Using the MATLAB Environment 1..¡± This paper describes an automated laboratory stand for measuring cogging torque using sensors and MATLAB-based data acquisition, which provided valuable insight into both the structure and methodology for this project.

Additionally, the video ¡°Introduction to Torque Ripple and Cogging Torque in Electric Machines 2.¡± from HBK Electric Power Testing offered a clear theoretical explanation of how cogging torque and torque ripple occur in electric machines. This video contributed to the theoretical understanding and formed the foundation for the scientific part of the project.

3) Sketch

The rig consists of:

• A baseplate with two motors: one driving motor that moves the system via a belt, and one test motor connected to a vertical coupler and an arm.
• The arm extends upward between two vertical walls, each equipped with a load cell that measures the force when the arm moves.
• At the lower end of the arm, a collet chuck is mounted to connect the encoder on one side and the motor shaft on the other.
• A gear is attached to the driving motor, and a belt runs around this gear and the coupler connected to the motor under test.
• An encoder on the test motor shaft records the rotational angle.
• Sensors: INA260 (for voltage and current measurement).
• Electronics: FPGA and power supply, mounted in a separate box next to the rig.

4) Bill of materials (BOM)

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5) Plan

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