Development and experiment of measure and control system for stalk cutting test bench

In order to provide a theoretical basis and technical support for developing the high efficient stalk harvest equipment, effects of the factors, such as the cutting speed, the feeding speed, and the cutting angle etc on the cutting properties of the stalk during cutting process was studied, and the parameters of the stalk cutter would be optimized. A measure-control system for the stalk cutting test bench was designed based on LabVIEW. The system consists of three sections, namely a motor control system, a data acquisition system and a host computer system. The motor control system consisted of an inverter, a cutting motor, a feeding motor and a RS-232/485 interface converter. It was used to control precisely the cutting speed and the feeding speed respectively with the inverter by inputting the frequency, which was calculated according to the desired rotation speed of the motor and the PID (proportion integration differentiation) control strategy. The data acquisition system consisted of a PCI1710HG acquisition card, a tension-compression force sensor, a torque sensor, an encoder and a signal conditioning circuit. Before the data acquisition system working, the number of the PCI1710HG card, the communicating channel and the acquisition frequency of the data should be selected at first. The data outputted by the torque sensor and the force sensor were recorded high-speed accurately in the circulation way. Meanwhile, the real-time motor rotation speed was measured by the encoder, and the PID control of the motor could be carried out on the basis of the real-time rotation speed. The host computer system consisted of an industrial personal computer and the measure-control software, which was developed with LabVIEW and characteristic of the friendly human-computer interface. Therefore, the data could be displayed and analyzed in real-time. The test results showed that the cutting speed and the feeding speed were continuously regulated from 0 to 2 m/s, the signals of the cutting force and cutting torque could be fast gathered from 0 to 10 kHz and displayed, and the data could be recorded and replayed. To verify the reliability and the accuracy of the measure-control system, some experiments were performed with some crop stalks, including cotton (Innovation cotton "958") stalk and the corn (Jinhai 5) stalk. The diameter, the moisture content of the cotton stalk were respectively 15-16 mm and 25.1% with plant space of 300 mm and row space of 600 mm. The diameter, the moisture content of the corn stalk were respectively 23-25 mm and 70.4% with plant space of 210 mm and row space of 600 mm. It was found that the peak cutting force and the peak torque for the cutting stalk decreased with the increase of the cutting speed when the cutting ratio (the ratio of the cutting speed to the feeding speed) and the cutting angle were constant. In addition, under the same cutting speed and the cutting speed ratio, the peak cutting force and peak torque decreased with the increase of the cutting angle at first and then increased, and the minimum value of the cutting force and the torque occurred when the cutting angle was about 13°. The results indicated that the measuring and controlling system could have any combination of the different cutting speed and the feeding speed to simulate the different cutting conditions, and it also could have the capacities of measuring and analyzing the data of the cutting toque and cutting speed as well as the rotation speed of the motor with the high reliability and the accuracy.