Sensorless Control of Brushed DC Motors: A Cost and Space Efficient Approach Using Sliding Mode and State Space Observers

Sensorless control of DC motors is a key solution for reducing system complexity and cost in various applications. Two common techniques used for sensorless control are back electromotive force (BEMF) and current ripple sensing. While the current ripple provides better reliability in varying motor conditions, it requires a high sampling frequency, which increases the cost of the microcontroller, especially for high-speed motors. In contrast, BEMF sensing, although ineffective at low speeds, is highly suitable for high-speed applications such as the one presented in this study. This paper focuses on two distinct sensorless control approaches for a brushed DC motor operating at high speeds. First approach is based on Sliding Mode Observer combined with a Load Torque Observer including filtration functionality. The second approach uses a State Space Observer. Both methods were simulated in MATLAB/Simulink environment and implemented on a 32-bit ARM microcontroller, where they both provided sufficient information about motor speed. This approach aims to provide cost-effective and space efficient sensorless control for high-speed drives.