A Research On Two-degree-of Freedom Motor System In Probe Locating System Applications

The probe locating system is an important part of gas turbine's ejecting blast cooling test bench. The key factor to improve the quality of blowing experiment's airflow field is to control the probe's linear and rotational movement and the coordination motion of various probes with high precision to achieve the distributed measurement of airflow accurately.This subject proposed a probe locating project based on a two-degree-of-freedom motor which can achieve the movement in two degrees of freedom so as to minimize the system's dimension. The direct drive will guarantee the constant speed performance and greater acceleration, thus the control accuracy will be improved greatly. Additionally, the two-degree-of-freedom motor was made up of few component and with a simplify structure, the lubrication requirement was limited too, this means the system will has a longer life and can work cleanlily.The proposed probe locating system was achieved by two-degree-of-freedom motor, the axial and radial movements were achieved by a linear motor and a stepping motor each respectively. The linear motor was built with hollow shaft structure, and its mover was built with the rotational motor's rotor as one component, so the two degrees freedom motion can be realized and the motor's dimension can be reduced too. The determined linear motor for axial movement adopt shorten primary cylinder type radial permanent magnet circuit PMSM structure. No additional excitation circuit is needed, so the motor's structure was simplified to satisfy the probe's narrow space requirement. The PMSM was with good controllability and high position accuracy which can satisfy the probe locating system's control requirement. The shorter primary structure can reduce the cost and radial magnet circuit was simple to manufacture. The cylinder type can suit to high speed linear motion, the primary winding was with high utilization ratio and there is no transverse end-effect which means unilateral magnetic force can be get over easily and its regulation and control is simple, it is with strong adaptability. This linear motor's electromagnetic design and simulation was proposed in this paper, the result show that the design was in reason and feasible.The radial movement part adopt hybrid stepping motor which can integrate the advantages of both reaction stepping motor and PM stepping motor. The stepping angle was small with a cogging torque. The motor's electromagnetic design and simulation was proposed in the paper, the result show that the design was in reason and feasible, it can satisfy the accuracy requirement of probe locating system and can fix the location after deenergizing.The developed control system for two-degree-of-freedom motor was with an axial displacement of 200mm, and its control precision should be up to±0.03mm, the control system adopt position and speed double loop control. The radial movement component is a hybrid stepping motor which can rotate in 360°with the precision of 0.1°, through the control of pulse the position and speed can be controlled. The 180 subdivision control was adopt, the resolution of each step is 1.8°/180=0.01°.