Design and Experiment of Motor Driving Bus Control System for Corn Vacuum Seed Meter

Abstract

The travel speed has great impact on motor driving planting performance. A motor driving planting system with CAN bus control was designed to explore the effect of travel speed on seed meter by using the method of CAN bus communication. The system mainly included an HMI, a planting monitoring ECU and a planting driving ECU, according to the ISO 11783 protocol, the planting machine bus system was designed. A four-channel air suction corn seed metering device was used as the test object, and a test platform was set up to test the bus control speed control accuracy of the seed plate. The problems of long regulation time at low speed and large overshoot in the traditional PID adjustment process were found from the bus extraction data. The piecewise PID parameter control method was adopted to optimize the control results. Based on the experimental results, the speeds of the seed plate were divided into three parts: the low rotation speed (15~20r/min), the middle rotation speed (20~40r/min) and the high rotation speed (40~55r/min). In each part, the PID control set different parameter values. The optimizing system results showed that the average regulating time and the average overshoot were 1.84s and 38.51% with 1.63s and 34.41% decreases, respectively, at low rotation speed, when within the range of 15~55r/min, the absolute value of steady-state error was 0.97r/min on average, the variance was 0.76r/min, and the absolute value of steady-state error was reduced by 0.13r/min on average. In the monitoring planting accuracy test of the bus system, the seed space was 20cm, the number of holes of the seed plate was 26, the travel speed was 4~12km/h, the results showed that the average accuracy of system monitoring was 97.53% with standard deviation of 0.48%. According to the experimental results of the planting bus system performance influenced by travel speed, when the rotational speed of fan was 540r/min and the travel speed was 4~8km/h, the wind pressure was -6.0~-5.9kPa and the mean qualified index of seeding was 95.68% with the standard deviation of 2.29%. When the travel speed reached 9km/h, the qualified index dropped below 90%, and the miss-seeding index was high. The performance evaluation of planting bus system response performance influenced by a step change travel speed was done by monitoring the travel speed and four planting driving motors, when the travel speed was in the range of 4~12km/h with an increment of 2km/h, the average response time of the system to the speed of seed plate was 2.00s with standard deviation of 0.34s. When the travel speed was in the range of 4~12km/h with a decrement of 2km/h, the average response time of the system to the speed of seed plate was 1.83s with standard deviation of 1.07s, the planting bus control system had a short response time when influenced by travel speed step changing.

Keywords: air suction corn seed metering device, motor driving, bus control system