Control System Research For A Nano-Material Mixer

When some polymer solutions are mixed through stirring, their viscosity will produce complex change during the reaction process. In order to assure the response run smoothly, demanding the stirring rate should be adjusted timely according to the change of the viscosity. The paper contrapose this process, designed a kind of mixer control system, which can regulate the mixer's stirring rate by detecting the change of solution's viscosity automatically, and realize control process automation.The research in this paper was carried out based on the principle that solution viscosity changes would lead to changes of mixer's load torque. Research method: detect the mixer's principal axial torque and rotate speed by relevant sensor, then send the signals to PC , use software to process, calculate the ratio of torque and rotate speed, and regard this value as the controlled variable to create motor control signal, output through the DAQ Card as motor drive circuit's control signal to control mixer speed. The emphasis of system design is measuring the rotational axle torque accurately and the signal transmission error-free, and the motor's automatic speed regulation stepless.The article confirmed design scheme through comparing the current commonly used method of torque detector and motor control. System chose strain torque measuring system to detect the mixer's principal axis torque signal, and realized the signal's stable amplification through signal conditioning circuit composed by instrument amplifier AD623. After transforming the torque signal through A/D conversion circuit which was composed of AT89S52 and ADC0809, drew the signal out through the way of wireless transmission, then passed through serial port circuit to computer, and concluded the torque values by LabVIEW program manipulation. Taking the torque as controlled variable, used LabVIEW writing motor control program, and output through the DAQ Card as motor drive circuit's control signal, realized the motor's speed control.System innovatively apply the Virtual Instrumentation into detection and control, the interface is simple and easy operation, the control is flexible, user can regulate relevant parameter in front panel to apply the system in different working condition. In order to prove the system control performance, we did software and hardware simulation test after design completion. Simulation test shouede that the system had small torque value measurement error, smooth motor speed control process, small time delay, and fast running speed, which basically achieved the intended purpose, and contended the actual operating requirement.