Table 1.
Emerging magnetic-based localization strategies.
| Ref (Year) | Technique/ Algorithm |
WC, EC | Validation Environment | Error/Accuracy | Notes |
|---|---|---|---|---|---|
| [27] (2023) | Active Locomotion/ Jacobian-based iterative method |
WC: IMU + 3-axis magnetic field sensor, EC: External PM | Experimental evaluation: Different translational and rotational motion | Average Positional Error (PE): 6.29 mm, Average Orientation Error (OE): 2.93° | 6 DoF reported and magnetic moment is optimized for the magnetic dipole model. |
| [28] (2022) | Active Locomotion/direct estimation + Kalman filter | WC: IPM + BLE + IMU EC: 5 × 5 Hall sensors | Experimental evaluation: work ranges from 25 to 72 mm | Mean AE: 1.46 mm, Mean OE: 0.41° | 6 DoF reported and, instead of using a PM, a magnetic capsule shell is proposed. |
| [29] (2020) | Passive Locomotion/Jacobian matrix | WC: IPM, EC: 4 triple-axis sensors | Experimental evaluation | Mean PE: 2.1 ± 0.8 mm, Mean OE: 6.7 ± 4.3° | Triple-axis sensors were utilized with the Jacobian method to achieve 5 DoF localization. |
| [31] (2023) | Active Locomotion/PSO + L-M | WC: IPM EC: Hall effect sensors | Experimental evaluation: static and dynamic | Mean AE: 1.46 mm, Mean OE: 0.41° | Fast tracking and 6 DoF localization are reported by combining the algorithms. |
| [32] (2019) | Passive Locomotion/ Variance-based algorithm | WC: IPM EC: 16 Hall effect sensor + IMU | Experimental evaluation: static capsule | Average PE: 9.73 mm, Average OE: 12° | The variance-based algorithm combined with weighted optimization is used to achieve 6 DoF localization. |
| [33] (2022) | Passive Locomotion/Fusion algorithm | WC: IPM EC: 36 Hall effect sensor + IMU | Experimental evaluation | Average PE: 1.8 mm, Average OE: 5.11° | The fusion algorithm calculates the quaternion rotation and 6 DoF localization is reported. |
| [34] (2021) | Active Locomotion/L-M + differential signals | WC: IPM EC: 16 tri-axis sensors | Experimental evaluation: static and dynamic motion | PE: 7.5 mm, Average OE: 13.8° | A symmetrically arranged cell of four sensors combined with different algorithms are used to achieve 6 DoF localization. |
| [35] (2022) | Passive Locomotion/L-M | WC: IPM EC: 12 Hall effect sensors | Experimental evaluation with different magnets | Relative PE: 4.3 ± 3.3 mm, Relative OE: 2 ± 0.6° | Neodymium N52 cylindrical permanent magnets with different diameters are used to achieve 6 DoF localization. |
| [36] (2021) | Active Locomotion/Differential method | WC: IPM EC: 8 Hall effect sensors | Experimental evaluation: multi-point simultaneous tracking | Average PE: 4.06 ± 0.29 mm, Relative OE: 5.63 ± 4.24° | The reported calculation time is 80 ms, and the algorithm can compensate for patients’ movements for 5 DoF localization. |
| [40] (2022) | Passive Locomotion | WC: IPM EC: 12 sensors, + orthogonal coils | Experimental evaluation: Dynamic magnetic field | Mean PE: 3.8 ± 1.1 mm, Maximum OE: 3° | The system used two orthogonal reference coils alternately switching on and off with a low switching speed for 6 DoF localization. |
| [41] (2021) | Active Locomotion/RMSD | WC: IPM + tri-axial sensors EC: 4 electromagnets | Experimental evaluation: Dynamic and static magnetic fields | Position accuracy (PA): 5 mm, Orientation accuracy (OA) 5° | The optimization process utilized a dual-step approach for 6 DoF localization. |
| [45] (2021) | Active Locomotion/Linear prediction | WC: RX coils EC: TX coils | Experimental evaluation: Dynamic magnetic field | PE: 12 mm | A dual-purpose use of WPT, not only for powering the capsule, but also for 3 DoF localization within the GI tract, is proposed. |
| [46] (2024) | Passive Locomotion/LSE, SD | WC: Orthogonal Coils EC: TPT | Experimental: VNA Measurement | Accuracy < 1 cm | The study utilizes QS-MI for precise localization, and the method is validated through simulation and VNA measurements. |
| [47] (2020) | Active Locomotion/L-M + PSO | WC: Induction coil EC: Electromagnets | Experimental evaluation: Dynamic and static magnetic fields | Average PE: 2.3 mm, Average OE 0.2° | An innovative feature of the methodology is the use of nine-channel sinusoidal signals to stimulate the transmitting coils for 6 DoF localization. |
| [48] (2024) | Passive Locomotion/L-M | WC: Induction coil + AFE + Modulator EC: 8 TX coils | Experimental evaluation: Dynamic magnetic fields | PA: 0.8 mm, OE 1.1° | On-chip sensing method utilizing CMOS 65 nm technology for a compact and cheap design for 5 DoF localization. |
| [51] (2023) | Passive Locomotion/FDMML + Welch’s method + ANNs | WC: Induction coil + wireless TX + battery EC: 6 TX coils | Experimental evaluation: Dynamic magnetic fields | PA: <1mm | The FDMML technique assigns unique offset frequencies to external magnetic beacons, allowing them to operate simultaneously and eliminating the need for sequential activation. |