Rotating Body Yaw Estimation Using GNSS Velocity and IMU
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Solution Overview
Problem
Existing methods for estimating the yaw of rotating machines, such as excavators, are prone to high errors due to low precision GNSS receivers and short antenna separations, especially in poor signal environments, leading to potential operational deviations and collisions.
Innovation Solution
A method that determines a motion state of a machine with a rotating body, obtaining velocity measurements from GNSS antennas and using inertial measurement units to calculate unit vectors and estimate yaw based on rotation angles between these vectors, improving accuracy by considering the direction of yaw rates and lever arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the distance separating the two antennas is decreased, then device size is reduced, but the error in yaw estimate increases
Solution Approach 1:
The patent substitutes the mechanical position-difference method with a dynamic measurement approach using velocity, acceleration, and angular rate sensors. This substitution eliminates the direct dependence on antenna separation distance, allowing small antennas to be used without sacrificing yaw estimation accuracy.
Solution Approach 2:
The patent introduces IMU measurements (accelerometers and gyroscopes) as intermediary sensors that bridge the gap between limited antenna separation and accurate yaw estimation. These intermediary measurements provide additional information about machine motion that compensates for the reduced baseline between antennas.
2Ease of manufacture
If mid-precision or low-precision GNSS receivers are used, then cost is reduced, but position measurement accuracy decreases leading to higher yaw estimation error
Solution Approach 1:
The patent changes from using position measurements to using velocity measurements combined with IMU data. This parameter change allows the system to achieve accurate yaw estimation even with lower-precision GNSS receivers, as the velocity and acceleration data from IMU compensate for the reduced position measurement quality.
Solution Approach 2:
The patent creates a composite sensing system that combines GNSS velocity measurements with IMU measurements (accelerometers and gyroscopes). This composite approach leverages the strengths of each sensor type to achieve accurate yaw estimation without requiring high-precision GNSS receivers, thereby reducing overall system cost.
3Measurement precision
If velocity measurements and IMU data are combined, then yaw estimation accuracy is improved in poor signal environments, but device complexity increases
Solution Approach 1:
The patent makes the system multi-functional by using the IMU for multiple purposes: providing acceleration data for velocity integration, providing angular rate data for direct yaw rate measurement, and providing orientation data for coordinate transformation. This multi-functionality justifies the added complexity by extracting maximum value from the IMU sensors.
Solution Approach 2:
The patent implements feedback mechanisms where IMU measurements continuously correct and refine the yaw estimation based on velocity measurements. The system uses feedback loops to integrate acceleration data, differentiate position data, and combine multiple sensor inputs in a way that compensates for individual sensor errors, thereby improving accuracy despite increased complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces yaw estimation errors by enhancing accuracy even in low-precision environments and short antenna separations, enabling precise control and operation of rotating machines.
Implementation Method 1
an inertial measurement unit (IMU) that is mounted on the motor grader... Three orthogonal accelerations and three orthogonal angular rotation rates are measured with each IMU
Implementation Method 2
GNSS navigation signals are received with each GNSS antenna, and a position of each GNSS antenna is computed
Data Source
AI summary
A method for estimating a yaw (or heading) of a rotating body of a machine is disclosed. The method may include obtaining measurements related to a velocity of a global navigation satellite system (GNSS) antenna coupled to the rotating body based on a motion state associated with the machine satisfying one or more conditions, calculating a first unit vector of a lever arm from a rotation axis to the GNSS antenna, and calculating a second unit vector orthogonal to the one or more measurements related to the velocity of the GNSS antenna in a direction towards the rotation axis (e.g., based on a velocity of another GNSS antenna coupled to the rotating body and/or a yaw rate measurement obtained by an inertial measurement unit). Accordingly, the yaw of the rotating body may be estimated based on a rotation angle between the first unit vector and the second unit vector.