Real-time control of load cell based two-wheel balancing robot using PID controller

Abstract

In this study, real-time application of load cell-based two-wheel balancing robot (TWBR) has been realized. The control of the system is provided by the PID controller with four load cells placed on the twowheel balancing robot. The analog signals of the weight information coming from the load cell are converted into digital signals with the 24-bit resolution HX711 module. The data converted into digital signals are interpreted through the microprocessor over the synchronous serial communication protocol. The output of the dynamic model of the system can be updated instantly, according to the measured weight information. This process updates the maximum pitch attitude. Thus, the control of the two-wheel balancing robot is facilitated and the risk of the user falling off the vehicle is reduced. The control of the system is carried out using an ARM architecture based STM32F103C8T6 microprocessor. Current values and motor rotation speed information of the Brushless Direct Current Motor (BLDC) are obtained during the real time application of the vehicle. In addition, 12 different data are recorded on the SD card with using the SD card module. As a result of the data recorded on the card, the correlation value of each load cell is obtained as 0.99 in the repetition test of the load cells. As a result, the measurement error rate of the weight on the two-wheel balancing robot is obtained as 1%.

Keywords

• Two-Wheel balancing robot (TWBR)
• Loadcell
• Electrical vehicle
• PID controller
• Microprocessor

Yük hücresi temelli iki tekerlekli denge robotunun PID kontrolör kullanarak gerçek zamanlı kontrolü

Öz

Bu çalışmada, yük hücresi temelli iki tekerlekli denge robotu (İTDR)’nin gerçek zamanlı uygulaması gerçekleştirilmiştir. İki tekerlekli denge robotun üzerine yerleştirilen dört adet yük hücresi ile sistemin kontrolü PID kontrolör tarafından sağlanmaktadır. Yük hücresinden gelen kütle bilgilerine ait analog sinyaller 24 bit çözünürlüklü HX711 tümleşik entegre ile sayısal sinyallere dönüştürülmektedir. Sayısal sinyallere dönüştürülen veriler senkron seri haberleşme protokolü üzerinden mikroişlemci ile aracılığı ile anlamlandırılmaktadır. Ölçülen kütle bilgisine göre sistemin dinamik modelinin çıkışı anlık olarak güncellenebilmektedir. Bu işlem maksimum yunuslama açısını güncellemektedir. Böylelikle iki tekerlekli denge robotunun kontrolü kolaylaşmakta ve kullanıcının araç üzerinden düşme riski azaltılmaktadır. Sistemin kontrolü ARM mimariye sahip STM32F103C8T6 mikroişlemci kullanılarak gerçekleştirilmiştir. Aracın gerçek zamanlı uygulaması sırasında Fırçasız Doğru Akım Motoru’nun (FDAM) akım değerleri ve motor dönüş hız bilgileri elde edilmektedir. Ayrıca SD kart modülü yardımıyla 12 adet farklı veri SD kart üzerine kaydedilmektedir. Karta kaydedilen veriler sonucunda yük hücrelerinin tekrarlama testinde her bir yük hücresinin korelasyon değeri 0,99 olarak elde edilmiştir. Sonuçta iki tekerlekli denge robotun üzerindeki kütlenin ölçüm hata oranı %1 olarak elde edilmiştir.

Anahtar Kelimeler

• İki tekerlekli denge robotu (İTDR)
• Yük hücresi
• Elektrikli araç
• PID kontrolör
• Mikrodenetleyici

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