The Design and Implementation of a Sensorless Power Tool Based on a Microcontroller

Abstract

Power tools are basic working tools used for production and manufacturing in the machinery and mechanical industries. The motor drive plays an important role in power tool applications. The performance of the motor drive will then directly or indirectly affect the quality and precision of the processing metal components. Most of the traditional motor drive control of a brushless direct current (BLDC) motor employs the Hall-effect position sensors to detect the rotor position. However, the installing sensors are prone to degrading the performance due to variations in temperature and the harsh environment. This disadvantage can be overcome with sensorless solutions. Among these sensorless solutions, the zero-crossing point detection of the back electromotive force (BEMF) is popular. Nevertheless, for the 180-degree conduction mode, it is impossible to directly detect the BEMF because of the three terminals of the motor which are conducted at any time for an electrical cycle. Therefore, a novel sensorless circuit approach based on the terminal line to line voltage is proposed in this paper. Moreover, an improved circuit scheme with a Schmitt trigger for sensing the BEMF is also proposed and implemented to obtain the precisely resembling Hall-effect signals. Finally, a prototype of a sensorless BLDC motor drive with a 180-degree conduction mode speed control for power tools is designed and implemented in this paper. The experimental results show that the proposed circuit works properly and validates the feasibility and fidelity of the motor drive system.

Performance Evaluation of Brushless Direct Current Motor Control Methods through Low-Cost Microcontroller-Based Real-Time Experiments

“…These commutation modes have some pros and cons according to each other. To mention a few, the detection of zero-crossing points of back-EMF can be easily achieved and extracted from the unenergized phase in 120° commutation mode, while it is not possible in 180° commutation mode since there is no unenergized phase [10]. If the application needs more torque, 180° commutation mode can be preferred because all of the threephases contribute to torque at each commutation state [11].…”

BLDC Motor Drives with A Programmable Simplified C-Block to Generate Accurate Six-Step PWM Based on STM32 Microcontroller

“…The microcontroller is used because it has several advantages, including faster speed, low cost, small chip size, and ease of troubleshooting [1]. Some of the work done using microcontrollers such as Texas Instruments as in [2] [3], ATMega as in [1][4] [5] [6], Microchip as in [7] [8], and STM32 as in [9] [10].…”

Non-Zero Crossing Point Detection in a Distorted Sinusoidal Signal Using Logistic Regression Model

“…A digital frequency measurement method is proposed is proposed in [17] to overcome the difficulty that the single zero-crossing point detection is sensitive to noise in the traditional dual mixer time difference measurement method.The proposed method uses sinusoidal beat technology, multi-channel synchronous acquisition technology, and digital frequency measurement technology. Sensor less control of BLDC motor based on zero-crossing point detection of the back electromotive force (BEMF) is proposed in [18]. Micro-controller based and low cost speed controller for BLDC motors up to 500 W is developed in [19] by employing the zero crossing point (ZCP) detection of the back-electromotive forces.…”