طراحی یک مسافت سنج الکترونیکی برای موتورهای جریان مستقیم
Abstract
1- Introduction
2- Our method
3- Simulation and design
4- Digital processing
5- Experiment
6- Conclusion
References
Abstract
The paper proposes an innovative electronic sensor for odometry in mobile robotics. The sensor is based on measurement of current peaks caused by commutation of a DC electric motor. The signal is preprocessed by analog filters, then digital processing in microcontroller is applied. The sensor utilizes small low-power MCU AtTiny44 and provides SPI interface for the communication with the master robot controller. The main advantage of the proposed sensor is the lack of any mechanical parts, which results in high durability. The sensor has been simulated in Simulink and then a fully-functional sample was created and tested.
Introduction
Brushed DC motors with permanent magnets are widely used in many industrial, automotive or household applications. Their great advantage over modern brushless DC motors (BLDC) is the simplicity of the control driver (single H-bridge with PWM control signal is sufficient). On the other hand, BLDC motors have greater efficiency and durability (no mechanical commutator is present). While the position and speed control of BLDC motors is straightforward (BLDC is a synchronous motor), brushed DC motors require sensing of the current speed. In mobile robotics, the position of the motor’s rotor is required to estimate the position of the robot. The commonly-used approach utilizes an external permanent magnet mounted at the end of the motor’s shaft. The orientation of the magnet is then sensed by Hall effect sensors (Rapos et al. (2016)). The output voltage of the Hall effect sensor contains pulses corresponding to the presence of the permanent magnet nearby the sensor. Rotating permanent magnet may cause electromagnetic interference in nearby electronics and mechanical vibrations of the shaft. It increases the overall length of the motor and requires non-metallic enclosing to prevent pollution of the magnet by ferromagnetic dust. If the shaft of the DC motor is not designed (long enough) to bear the external sensor, an additional installation of the sensor may be problematic.