An Improved Simultaneously Magnetic Actuation and Localization Method based on Magnetic Sensor Array Qinyuan Shi 1 , Min Wang 1 , Shuang Song 1* and Max Q.-H. Meng 2 1 Shenzhen Engineering Lab for Medical Intelligent Wireless Ultrasonic Imaging Technology, Harbin Institute of Technolgoy, Shenzhen, China 2 Department of Electronic Engineering, Chinese University of Hong Kong, Hong Kong, China Abstract—Magnetically actuated wireless capsule robot has been a promising medical apparatus for minimally invasive examination and operation in the gastrointestinal tract. Position and orientation information of the robot are essential for an effective and safe feedback control. However, simultaneous actuation and localization is still a challenge. In our previous work, we proposed a multi-magnet based method. To further improve the tracking accuracy, in this paper we propose a method which utilizes the prior known pose information of the external actuation magnet. Moreover, the method also can simplify the calculation. A magnetic sensor array is used to sample the magnetic field from the external magnet and internal magnet. By subtracting the magnetic field of the external magnet according to the prior pose information, pose of the internal magnet then can be estimated by using nonlinear optimization algorithm. Experimental results verified the proposed method. Keywords—simultaneously magnetic actuation and localization; magnetic sensor array; position and orientation information; I. INTRODUCTION Magnetic actuation method can realize remote control without the magnetic source occlusion problem, showing great potential for minimally invasive surgery (MIS), which makes it a popular subject. Generally, a magnet is embedded in the operation device and driven by the external magnetic field in this method. To accurately manipulate the magnet, its real-time pose information is required. Many tracking technologies have already been proposed, such as vision [1] and ultrasound methods [2]. Compared with the above mentioned methods, magnetic tracking method has no line-of-sight problem [3]-[5] and can be divided into two types according to the excitation source: permanent magnet-based tracking [6], [7] and electromagnetic coil-based tracking [8]-[10]. The permanent tracking method has a great advantage of no need for power supply over electromagnetic tracking, which enables it to be widely used in MIS. Magnetic tracking measures the spatial magnetic field using sensors and then estimates pose information of targets by solving the sensing data. Sensor array has been widely used for localization [11]-[12]. * Corresponding author: S.Song (songshuang@hit.edu.cn). This work was supported in part by National Key R&D Program of China (2018YFB1307700), in part by National Natural Science Foundation of China (61803123), and in part by the Science and Technology Innovation Committee of Shenzhen (JCYJ20170413110250667). A traditional magnetic tracking method cannot work well with magnetic manipulation simultaneously because of the magnetic disturbance. To be specific, when using a magnet to manipulate magnetic robot, the strong magnetic field from the driving magnet may interfere with the sensor array which will lead to low accuracy of localizing the robot. Mounting magnetic sensors on the passive magnet has been proposed in [13] and extracting the fed magnetic field generated by electromagnetic coils from the measured magnetic field has been used in [14] to solve this problem. In the previous work, a multi-object positioning and identification method has been introduced in [15] and a real-time pose tracking and navigation method has been proposed in [16]. Both the active and the passive magnets can be localized by setting the driving one as one of the tracking targets. Due to the different magnetic moment value, both magnets can be identified. However, the ratio of the magnetic moment value in [16] is relatively small which cannot realize effective actuation in practical application scenario and will not cause severe interference. To further improve the tracking accuracy, in this paper we propose a method which utilizes the prior known pose information of the external actuation magnet. A magnetic sensor array is used to sample the magnetic field from the external magnet and internal magnet. By subtracting the magnetic field of the external magnet according to the prior pose information, the pose of the internal magnet then can be estimated. The proposed method not only can improve the tracking accuracy, but also improve the ratio between the external magnet and internal magnet, which can lead to a better actuation result. Moreover, the method also can simplify the calculation. The organization of the paper is as follows. In Section II, the proposed tracking method will be introduced. Experimental results will be presented in details in Section III. Finally, conclusions will be drawn in Section IV. II. THE PROPOSED TRACKING METHOD As shown in Fig.1, the proposed method has two parts: two cylindrical magnets with different size, and a magnetic sensor array. Magnet 1 with ܭ ଵ is the passive (or internal) magnet and magnet 2 with ܭ ଶ is the active (or external) one. According to 978-1-7281-1634-1/19/$31.00 ©2019 IEEE