US 11,733,023 B2
System and method for angle calculations for a plurality of inertial measurement units
Pablo Abad, San Francisco, CA (US); Prudhvi Tej Chinimilli, San Francisco, CA (US); and Ivan Vican, Imotski (HR)
Assigned to Muvr Labs, Inc., San Francisco, CA (US)
Filed by Muvr Labs, Inc., San Francisco, CA (US)
Filed on Mar. 20, 2019, as Appl. No. 16/359,599.
Claims priority of provisional application 62/645,788, filed on Mar. 20, 2018.
Prior Publication US 2019/0293404 A1, Sep. 26, 2019
Int. Cl. G01B 7/30 (2006.01); G01C 25/00 (2006.01); G01P 21/00 (2006.01); G01C 21/18 (2006.01); G01C 21/16 (2006.01)
CPC G01B 7/30 (2013.01) [G01C 21/166 (2020.08); G01C 21/18 (2013.01); G01C 25/005 (2013.01); G01P 21/00 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A system, comprising: at least one first inertial measurement unit (IMU) is positioned on a first member of a joint; at least one second inertial measurement unit (IMU) is positioned on a second member of the joint; wherein the joint is a knee joint of a leg, the first member is a thigh of the leg, and the second member is a calf of the leg; wherein each of the at least one first IMU and the at least one second IMU lacks a magnetometer unit; wherein the at least one first IMU and the at least one second IMU respectively output at least one first IMU sensor data and at least one second IMU sensor data; at least one processing device configured to determine at least one mobility metric of the joint based at least in part on a yaw-constrained computation of: at least one first quaternion based on the at least one first IMU sensor data and at least one second quaternion based on the at least one second IMU sensor data; wherein the at least one first quaternion is a representation relating an Earth coordinate frame to a coordinate frame of the at least one first IMU worn on the first member; wherein the at least one second quaternion is a representation relating the Earth coordinate frame to a coordinate frame of the at least one second IMU worn on the second member; and wherein the at least one processing device is configured to determine the at least one mobility metric of the joint by executing programming instructions that cause the at least one processing to: receive, from the at least one first IMU, the at least one first IMU sensor data; receive, from the at least one second IMU, the at least one second IMU sensor data; input the at least one first IMU sensor data into a quaternion computation algorithm to compute the at least one first quaternion; input the at least one first quaternion and the at least one second IMU sensor data into the quaternion computation algorithm to compute the at least one second quaternion; wherein the inputting of the at least one first quaternion imposes a yaw constraint that reduces an uncertainty in: at least one first yaw axis value in the coordinate frame of the at least one first IMU and at least one second yaw axis value in the coordinate frame of the at least one second IMU; and input the at least one first quaternion and the at least one second quaternion into a calibration parameter algorithm to determine the at least one mobility metric of the joint; wherein the at least one mobility metric comprises at least one joint position and at least one joint angle based on: at least one first orientation and at least one first position of the at least one first IMU on the first member of the joint and at least one second orientation and at least one second position of the at least one second IMU on the second member of the joint.