Excavator Swing Boom Angle Sensing via Centripetal Acceleration
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Solution Overview
Problem
Existing excavator grade control systems face challenges in accurately determining the swing boom angle without long-term drift and require additional sensors or software, as they cannot rely on gravity due to the alignment of the rotational axis with gravity, and existing IMU-based methods suffer from integration drift and noise.
Innovation Solution
A system using a first IMU mounted on the swing boom to determine the direction of centripetal acceleration, combined with a processing unit to calculate the swing boom angle, and optionally utilizing a second IMU on the upper part to remove gravitational components, along with sensor fusion algorithms to compensate for drift and integrate gyroscope data for precise angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If IMU-based measurement is used to determine swing boom angle, then measurement capability is provided, but long-term drift occurs due to integration of gyroscope measurement
Solution Approach 1:
The system uses feedback by continuously monitoring the direction of centripetal acceleration and using it to correct the integrated gyroscope measurements. The accelerometer provides feedback on the actual orientation relative to the rotation axis, which compensates for the drift accumulating in the gyroscope integration over time.
Solution Approach 2:
The centripetal acceleration direction acts as an intermediary between the gyroscope measurements and the final angle determination. Instead of directly integrating gyroscope data, the system uses the accelerometer-measured centripetal acceleration direction as an intermediate reference that corrects the gyroscope drift, providing more reliable long-term measurements.
2Stability of the object's composition
If gravity is used to determine boom position, then stabilization is achieved for fixed boom excavators, but it cannot be used for swing boom excavators due to axis alignment with gravity
Solution Approach 1:
The system segments the acceleration measurement into distinct components: gravitational acceleration and centripetal acceleration. By separating these components, the system can use centripetal acceleration (which depends on the rotation axis orientation) instead of gravity (which is unavailable due to axis alignment), making the solution adaptable to swing boom configurations while maintaining stabilization capability.
Solution Approach 2:
The system changes the reference parameter from gravity direction to centripetal acceleration direction. Since the centripetal acceleration direction is perpendicular to the rotation axis and provides information about the swing boom angle, this parameter change enables the system to work with swing boom excavators while maintaining measurement stability.
3Measurement precision
If wire sensor is used to measure swing boom angle, then accurate measurement is achieved, but additional sensors and complex installation are required
Solution Approach 1:
The IMU unit is designed to be multi-functional, serving both as an inertial reference frame tracker and as a swing boom angle sensor. By mounting the IMU on the swing boom and using the centripetal acceleration direction, the same sensor provides multiple measurement functions, eliminating the need for separate wire sensors or angular encoders and reducing overall system complexity.
Solution Approach 2:
The system uses the motion of the excavator itself (the rotation of the upper part) to generate the centripetal acceleration signal needed for measurement. Instead of requiring an external wire sensor or encoder, the system leverages the existing operational dynamics of the machine to provide the measurement signal, making the system self-sufficient and reducing component 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
The system provides accurate and stable determination of the swing boom angle by isolating centripetal acceleration, reducing long-term drift and enhancing precision through sensor fusion, enabling reliable operation without reliance on wire sensors or additional initialization.
Implementation Method 1
determine a direction of a centripetal acceleration acting on the first IMU based on the received first IMU data when the upper part rotates about the first vertical rotation axis relative to the lower part
Data Source
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AI summary
The invention relates to a system for determining a swing boom angle 2 of an excavator 1, wherein the excavator 1 comprises a lower part 3, an upper part 4 comprising a cabin 5, the upper part 4 being arranged on the lower part 3 and configured to be rotated relative to the lower part 3 about a first rotation axis 7 and a swing boom 6 arranged on the upper part 4 and configured to be rotated relative to the upper part 4 about a second rotation axis 8 that an actual swing boom position defines a swing boom angle 2. The system comprises a first inertial measurement unit (IMU) 12 configured to be mounted on the swing boom 6 and to generate first IMU data, wherein the first IMU 12 comprises at least one acceleration sensor and a processing unit. The processing unit is configured to receive the first IMU data, determine a direction of a centripetal acceleration acting on the first IMU based on the received first IMU data when the upper part 4 rotates about the first rotation axis 7 relative to the lower part 3 and determine the swing boom angle 2 based on the direction of the centripetal acceleration.