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An Inertial and Optical Sensor Fusion Approach for Six Degree-of-Freedom Pose Estimation.

He C, Kazanzides P, Sen HT, Kim S, Liu Y - Sensors (Basel) (2015)

Bottom Line: In contrast, inertial sensing does not require line-of-sight but is subject to drift, which may cause large cumulative errors, especially during the measurement of position.When all the markers are occluded, the position tracking relies on the inertial sensors that are bias-corrected by the optical tracking system.Experiments are performed with an augmented reality head-mounted display (ARHMD) that integrates an optical tracking system (OTS) and inertial measurement unit (IMU).

View Article: PubMed Central - PubMed

Affiliation: Beijing Engineering Research Center of Mixed Reality and Advanced Display, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China. wosipo007@163.com.

ABSTRACT
Optical tracking provides relatively high accuracy over a large workspace but requires line-of-sight between the camera and the markers, which may be difficult to maintain in actual applications. In contrast, inertial sensing does not require line-of-sight but is subject to drift, which may cause large cumulative errors, especially during the measurement of position. To handle cases where some or all of the markers are occluded, this paper proposes an inertial and optical sensor fusion approach in which the bias of the inertial sensors is estimated when the optical tracker provides full six degree-of-freedom (6-DOF) pose information. As long as the position of at least one marker can be tracked by the optical system, the 3-DOF position can be combined with the orientation estimated from the inertial measurements to recover the full 6-DOF pose information. When all the markers are occluded, the position tracking relies on the inertial sensors that are bias-corrected by the optical tracking system. Experiments are performed with an augmented reality head-mounted display (ARHMD) that integrates an optical tracking system (OTS) and inertial measurement unit (IMU). Experimental results show that under partial occlusion conditions, the root mean square errors (RMSE) of orientation and position are 0.04° and 0.134 mm, and under total occlusion conditions for 1 s, the orientation and position RMSE are 0.022° and 0.22 mm, respectively. Thus, the proposed sensor fusion approach can provide reliable 6-DOF pose under long-term partial occlusion and short-term total occlusion conditions.

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Related in: MedlinePlus

Cadaver experiment with head mounted tracking system and display.
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sensors-15-16448-f001: Cadaver experiment with head mounted tracking system and display.

Mentions: In our previous work [18,19], we proposed a head-mounted optical tracking system for a surgical navigation application, as shown in Figure 1. Optical tracking provides drift-free measurement of position and orientation, but is subject to a line-of-sight constraint and suffers from slower update rates and higher latency [20]. In contrast, inertial sensing, which includes gyroscopes, accelerometers, and magnetometers, provides low latency and high frequency measurement, but these sensors either provide derivatives of position/orientation and are subject to drift, or provide absolute orientation but are subject to bias (e.g., magnetometer) [4,15]. In [21], the authors propose fusion of OTS and IMU measurements to estimate position and orientation in cases of brief occlusions of tracking markers, but only the accelerometer bias is estimated in the EKF. However, in long-term use of the IMU, the accuracy of orientation tracking will be influenced by the biases in the gyroscope and magnetometer. So, in [22] we proposed a sensor fusion approach where the 9-axial measurement from the IMU is bias-corrected by an OTS and used to track the orientation.


An Inertial and Optical Sensor Fusion Approach for Six Degree-of-Freedom Pose Estimation.

He C, Kazanzides P, Sen HT, Kim S, Liu Y - Sensors (Basel) (2015)

Cadaver experiment with head mounted tracking system and display.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541887&req=5

sensors-15-16448-f001: Cadaver experiment with head mounted tracking system and display.
Mentions: In our previous work [18,19], we proposed a head-mounted optical tracking system for a surgical navigation application, as shown in Figure 1. Optical tracking provides drift-free measurement of position and orientation, but is subject to a line-of-sight constraint and suffers from slower update rates and higher latency [20]. In contrast, inertial sensing, which includes gyroscopes, accelerometers, and magnetometers, provides low latency and high frequency measurement, but these sensors either provide derivatives of position/orientation and are subject to drift, or provide absolute orientation but are subject to bias (e.g., magnetometer) [4,15]. In [21], the authors propose fusion of OTS and IMU measurements to estimate position and orientation in cases of brief occlusions of tracking markers, but only the accelerometer bias is estimated in the EKF. However, in long-term use of the IMU, the accuracy of orientation tracking will be influenced by the biases in the gyroscope and magnetometer. So, in [22] we proposed a sensor fusion approach where the 9-axial measurement from the IMU is bias-corrected by an OTS and used to track the orientation.

Bottom Line: In contrast, inertial sensing does not require line-of-sight but is subject to drift, which may cause large cumulative errors, especially during the measurement of position.When all the markers are occluded, the position tracking relies on the inertial sensors that are bias-corrected by the optical tracking system.Experiments are performed with an augmented reality head-mounted display (ARHMD) that integrates an optical tracking system (OTS) and inertial measurement unit (IMU).

View Article: PubMed Central - PubMed

Affiliation: Beijing Engineering Research Center of Mixed Reality and Advanced Display, School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China. wosipo007@163.com.

ABSTRACT
Optical tracking provides relatively high accuracy over a large workspace but requires line-of-sight between the camera and the markers, which may be difficult to maintain in actual applications. In contrast, inertial sensing does not require line-of-sight but is subject to drift, which may cause large cumulative errors, especially during the measurement of position. To handle cases where some or all of the markers are occluded, this paper proposes an inertial and optical sensor fusion approach in which the bias of the inertial sensors is estimated when the optical tracker provides full six degree-of-freedom (6-DOF) pose information. As long as the position of at least one marker can be tracked by the optical system, the 3-DOF position can be combined with the orientation estimated from the inertial measurements to recover the full 6-DOF pose information. When all the markers are occluded, the position tracking relies on the inertial sensors that are bias-corrected by the optical tracking system. Experiments are performed with an augmented reality head-mounted display (ARHMD) that integrates an optical tracking system (OTS) and inertial measurement unit (IMU). Experimental results show that under partial occlusion conditions, the root mean square errors (RMSE) of orientation and position are 0.04° and 0.134 mm, and under total occlusion conditions for 1 s, the orientation and position RMSE are 0.022° and 0.22 mm, respectively. Thus, the proposed sensor fusion approach can provide reliable 6-DOF pose under long-term partial occlusion and short-term total occlusion conditions.

Show MeSH
Related in: MedlinePlus