An Improved Algorithm for Adaptive Communication Frame Length Based on Modbus Protocol

The original Modbus protocol will inevitably cause high bit error rate when there are link problems in the network. Therefore, many experts have proposed to change the frame length according to the BER (bit error rate) to improve the link utilization. However, the link stability of this algorithm is very poor, which leads to the reduction of transmission efficiency. In order to solve the instability problem caused by the traditional adaptive frame length algorithm, an improved adaptive frame length adjustment algorithm is proposed in this paper. According to the average frame error rate in the time period, the method of “fast decrease, slow increase” is used to adjust the data frame length at different levels of FER (frame error rate). This algorithm not only improves the transmission rate, but also improves the stability of the link. Finally, this paper takes the servo drive data acquisition system as the carrier, and verifies the effectiveness of the algorithm through experiments.