| Since the application of capsule robot in medical diagnosis and treatment,its position and direction are the key factors for doctors to obtain accurate diagnosis and treatment positions.The commonly used capsule robot external positioning system has the disadvantages of low positioning accuracy,complex operation and high cost.Magnetic positioning is widely used in the capsule robot control system because of its advantages of high positioning accuracy,free from the restriction of line-of-sight occlusion,economy,and no damage to human body.Based on the cooperation with Nankai Hospital in the early stage,and according to the actual needs of doctors in clinical medicine,this paper proposes a magnetic positioning method for magnetically controlled capsule robots.First,according to BiotSavart law,the magnetic dipole model of the capsule robot is constructed,and the relevant formula of the magnetic field is analyzed,reducing the number of unknown parameters of the original position and direction from 6 to 3.Secondly,coordinate transformation is applied to the magnetic positioning algorithm to increase the compensation amount,and the least square method is used to compensate the magnetic positioning error of the capsule robot three times to improve the magnetic positioning accuracy of the robot.Finally,the parameters of the coordinate transformation magnetic positioning model are optimized,that is,the optimal location and number of sensor arrays are selected,and then the effectiveness of the magnetic positioning algorithm proposed in this paper is verified by simulation software design and actual experiments.The magnetic field model of permanent magnet is established using ANSYS simulation software,and the distribution of magnetic induction intensity is obtained.By analyzing the relationship between the position,number and positioning error of magnetic sensors,the optimal position and number of sensors are selected for positioning experiment of capsule robot.Several groups of capsule robot simulation positioning experiments were designed in the range of two-dimensional plane and three-dimensional space,and the calculated positioning error was less than 3 mm.The actual positioning experiment of the capsule robot is carried out by building an experimental platform.The positioning experiments of the capsule robot in the X-Y plane,Z-X plane and three-dimensional space are designed respectively.The experimental results show that the positioning errors of the capsule robot in the X-Y plane and Z-X plane are(1.92 mm,1.94 mm,2.15 mm,2.60 mm),(2.26 mm,2.26 mm,2.45 mm,2.46 mm)respectively when it makes straight,S-line,triangle and circular motion paths.n three-dimensional space,the average positioning error of the capsule robot in one-way motion is 2.57 mm,and the average positioning error in reciprocating motion is 2.95 mm.Through simulation and experiment,it is verified that the selection of the position and number of magnetic sensor array and the coordinate transformation magnetic positioning compensation algorithm have good positioning effect,which provides theoretical support for the future application in medical practice. |
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