IMU: Difference between revisions
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{{see also|Terms|Technical Terms}} | {{see also|Terms|Technical Terms}} | ||
An '''Inertial Measurement Unit''' ('''IMU''') is an electronic [[sensor]] [[device]] that measures and reports a body's specific force, angular rate, and sometimes the orientation of the body, using a combination of [[accelerometer]]s, [[gyroscope]]s, and often [[magnetometer]]s.<ref name="TDK_IMU_Overview"> | An '''Inertial Measurement Unit''' ('''IMU''') is an electronic [[sensor]] [[device]] that measures and reports a body's specific force, angular rate, and sometimes the orientation of the body, using a combination of [[accelerometer]]s, [[gyroscope]]s, and often [[magnetometer]]s.<ref name="TDK_IMU_Overview"> | ||
TDK InvenSense. “What is an Inertial Measurement Unit (IMU)?” | |||
[https://invensense.tdk.com/products/motion-tracking/6-axis/ TDK InvenSense Website]. Accessed May 3, 2025.</ref> IMUs are fundamental components in [[virtual reality|Virtual Reality (VR)]] and [[augmented reality|Augmented Reality (AR)]] systems for tracking the orientation of [[Head-Mounted Display|HMDs]] and [[Input Devices]] like controllers. | |||
==Components and Function== | ==Components and Function== | ||
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==Sensor Fusion== | ==Sensor Fusion== | ||
Raw data from individual sensors can be noisy (for example accelerometers during fast movement) and inaccurate (for example gyroscopes drift). [[Sensor fusion]] algorithms, such as [[Kalman filter]]s or complementary filters, are essential.<ref name="Mahony_Filter"> Mahony, | Raw data from individual sensors can be noisy (for example accelerometers during fast movement) and inaccurate (for example gyroscopes drift). [[Sensor fusion]] algorithms, such as [[Kalman filter]]s or complementary filters, are essential.<ref name="Mahony_Filter"> | ||
Mahony, R.; Hamel, T.; Pflimlin, J‑M. “Nonlinear Complementary Filters on the Special Orthogonal Group.” | |||
IEEE Transactions on Automatic Control, 53 (5) (2008): 1203‑1218. | |||
[https://doi.org/10.1109/TAC.2008.923738 DOI link]</ref> These algorithms intelligently combine the data from the accelerometers, gyroscopes (and magnetometers, if present) to produce a single, more accurate, stable, and low-latency estimate of the device's orientation in real-time. | |||
== Role in VR/AR == | == Role in VR/AR == | ||
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===6DoF Tracking Systems=== | ===6DoF Tracking Systems=== | ||
For full [[6DoF]] tracking (which includes [[positional tracking]] | For full [[6DoF]] tracking (which includes [[positional tracking]] translation along X, Y, and Z axes), IMU data is combined via sensor fusion with data from other tracking systems. These can include: | ||
* [[Inside-out tracking]]: Cameras on the HMD observe the external environment. | * [[Inside-out tracking]]: Cameras on the HMD observe the external environment. | ||
* [[Outside-in tracking]]: External sensors (like cameras or [[lighthouse tracking|base stations]]) observe markers on the HMD and controllers. | * [[Outside-in tracking]]: External sensors (like cameras or [[lighthouse tracking|base stations]]) observe markers on the HMD and controllers. | ||
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* '''MPU-6050''': A popular low-cost 6-axis IMU (accelerometer + gyroscope) from InvenSense, used in hobbyist projects and early devices like the [[Oculus Rift DK1]].<ref name="MPU6050_Datasheet"> InvenSense Inc. MPU-6000 and MPU-6050 Product Specification Revision 3.4. [https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-6000-Datasheet1.pdf Datasheet Link]</ref> | * '''MPU-6050''': A popular low-cost 6-axis IMU (accelerometer + gyroscope) from InvenSense, used in hobbyist projects and early devices like the [[Oculus Rift DK1]].<ref name="MPU6050_Datasheet"> InvenSense Inc. MPU-6000 and MPU-6050 Product Specification Revision 3.4. [https://invensense.tdk.com/wp-content/uploads/2015/02/MPU-6000-Datasheet1.pdf Datasheet Link]</ref> | ||
* '''MPU-9250''': An InvenSense 9-axis IMU (adds a magnetometer to the MPU-6xxx series capabilities).<ref name="MPU9250_Datasheet"> InvenSense Inc. MPU-9250 Product Specification Revision 1.1. [https://invensense.tdk.com/wp-content/uploads/2015/02/PS-MPU-9250A-01-v1.1.pdf Datasheet Link]</ref> Used in some dev kits and controllers. | * '''MPU-9250''': An InvenSense 9-axis IMU (adds a magnetometer to the MPU-6xxx series capabilities).<ref name="MPU9250_Datasheet"> InvenSense Inc. MPU-9250 Product Specification Revision 1.1. [https://invensense.tdk.com/wp-content/uploads/2015/02/PS-MPU-9250A-01-v1.1.pdf Datasheet Link]</ref> Used in some dev kits and controllers. | ||
* '''ICM-42688-P''': A high-performance 6-axis IMU from TDK InvenSense, known for its low noise and stability, used in the Meta [[Quest 2]] headset.<ref name="Quest2_Teardown_iFixit"> iFixit. | * '''ICM-42688-P''': A high-performance 6-axis IMU from TDK InvenSense, known for its low noise and stability, used in the Meta [[Quest 2]] headset.<ref name="Quest2_Teardown_iFixit"> | ||
iFixit. “Oculus Quest 2 Disassembly.” | |||
[https://www.ifixit.com/Guide/Oculus+Quest+2+Disassembly/139759 iFixit Repair Guide]. Accessed May 3, 2025.</ref> | |||
* '''BMI085/BMI270''': Bosch IMUs optimized for VR/AR applications, found in devices like the [[Valve Index]] controllers.<ref>Nield, David. "How VR Headsets Are Getting Better Through Improved Tracking." TechRadar, 2022.</ref> | * '''BMI085/BMI270''': Bosch IMUs optimized for VR/AR applications, found in devices like the [[Valve Index]] controllers.<ref>Nield, David. "How VR Headsets Are Getting Better Through Improved Tracking." TechRadar, 2022.</ref> | ||
* '''LSM6DSO/LSM6DSOX''': STMicroelectronics 6-axis IMUs used in various HMDs and AR glasses, including the [[HoloLens 2]]. | * '''LSM6DSO/LSM6DSOX''': STMicroelectronics 6-axis IMUs used in various HMDs and AR glasses, including the [[HoloLens 2]]. | ||