ABSTRACT
Objective Based on the existing clinical drainage device, two novel mechanisms were designed for the connection between the drainage tube of the patient and the drainage tube of the drainage bag, so as to compare such two mechanisms and validate whether the mechanisms can meet the design requirements for clinical use. Methods Mechanism 1 used the method of electromagnetic drive to pull in and Mechanism 2 used the magnetization method of permanent magnet to pull in. The finite element model of static electromagnetic field was established. The force of the two mechanisms under different currents was compared, and the distribution of magnetic field lines and magnetic induction intensity was analyzed. Simulation experiments were designed for preliminary experimental research. Results Under the pull-in state, the maximum magnetic induction of Mechanism 1 and Mechanism 2 at the closed end surface was found in contact area of the two iron cores. The suction force of Mechanism 1 could be adjusted by the current. When the current was 1 A, the maximum magnetic induction intensity at the closed end was 0.76 T, the electromagnetic force measured by the experiment was 6.08 N, the magnetic force of Mechanism 2 was 6.68 N, which was smaller than the 8 N suture tension. Mechanism 2 was separated by supplying the driving coil with a reverse magnetic field. Conclusions When the current was 1 A, Mechanism 1 could meet the magnetic attraction requirements, and Mechanism 2 could be separated when the current reached 1.8 A. Both mechanisms met the requirements of clinical design, but Mechanism 2 was more secure in the process of application. The feasibility of the mechanism structure was verified by finite element analysis and experimental test.
ABSTRACT
Objective:This paper studied the electromagnetic-driven pressure control system in the automatic measurement of intraocular pressure (IOP).The accuracy of pressure control directly impacts on the accuracy of IOP measurements,so it calls for precise pressure to achieve closed-loop control.Methods:According to the actual needs of IOP measuring,we got the structural and electromagnetic parameters of the electromagnetic drive system by combining the methods of numerical calculation and ANSYS simulation.Using the FC bus and digital-analog conversion,the microcontroller module controlled the drive current digitally and precisely in order to achieve closed-loop control of pressure.Results:The experimental results showed that in the electromagnetic pressure control system,the pressure range was 0 N～0.48982 N,the accuracy 0.00058 N,the drive current control error about 1% on average.Besides,the electromagnetic force and the excitation current showed a good linear relationship in the same stroke.Conclusions:The electromagnetic pressure control system achieved a good result in closed-loop control of pressure.The control pressure range and control accuracy were in line with the standard of Goldmann applanation tonometer.According to the results,this study laid the foundation for the further development of IOP automatically measuring instruments.