Forklift IMU Bias Estimation Using Stationary-State Detection
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Solution Overview
Problem
Existing methods for estimating the bias in inertial measurement unit (IMU) values for forklifts are inadequate, particularly in operational environments where the vehicle is not stationary, leading to inaccurate position determination.
Innovation Solution
A bias estimation device and method that utilizes sensors to determine when a forklift is stationary, accumulates IMU measurements during this state, and calculates bias by excluding sudden changes, ensuring accurate compensation of IMU values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bias estimation is performed using IMU measurement values during forklift operation, then position determination can be continuously maintained, but the estimation accuracy deteriorates due to vehicle movement and vibrations
Solution Approach 1:
The system dynamically adjusts the bias estimation process by switching between stationary-state estimation (high accuracy) and movement-state estimation (continuous maintenance). The determination unit detects whether the forklift is stationary or moving, and the accumulation unit selectively accumulates IMU measurement values based on this state, thereby adapting the estimation process to current operational conditions.
Solution Approach 2:
The bias estimation process is segmented into two distinct modes: stationary-state estimation using accumulated IMU values when the forklift is stopped, and movement-state estimation using GPS or other positioning data when the forklift is moving. This segmentation allows each mode to operate under its optimal conditions, maintaining overall system reliability while preserving accuracy during stationary periods.
2Measurement precision
If IMU measurement values are accumulated during stationary state for bias calculation, then bias estimation accuracy is improved, but sudden changes in measurement values may contaminate the accumulated data
Solution Approach 1:
The sudden change portion detection unit continuously monitors the accumulated IMU measurement values and detects abrupt changes that indicate external disturbances. When a sudden change is detected, the system excludes the contaminated data portion from bias calculation, providing feedback control that maintains data quality while preserving the benefits of accumulated stationary-state measurements.
Solution Approach 2:
The system extracts and excludes the sudden change portions from the accumulated IMU measurement values before performing bias calculation. This extraction process removes contaminated data segments while retaining the valid stationary-state measurement values, thereby maintaining both accuracy and reliability in the bias estimation.
3Ease of manufacture
If bias estimation is performed immediately after IMU activation, then the process is simplified, but the forklift may be in motion causing inaccurate stationary determination
Solution Approach 1:
Instead of assuming the forklift is stationary immediately after IMU activation, the system performs preliminary verification by detecting whether the forklift is actually stationary using multiple sensors (encoder, lifting height sensor, load sensor). This preliminary action ensures accurate stationary state determination before initiating bias estimation, preventing contamination from movement-induced vibrations.
Data Source
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AI summary
Object Provided is a bias estimation device that accurately estimates a bias of a measurement value of an inertial measurement unit. Solving Means A bias estimation device includes a determination unit configured to determine whether a forklift is stationary based on a measurement value from a first sensor configured to detect information regarding movement of the forklift and a measurement value from a second sensor configured to detect information regarding a cargo handling device included in the forklift, an accumulation unit configured to accumulate an IMU measurement value that is a measurement value from an inertial measurement unit included in the forklift when the determination unit determines that the forklift is stationary and stop accumulation of the IMU measurement value when the determination unit determines that the forklift is not stationary, and a calculation unit configured to calculate a bias of the IMU measurement value based on the IMU measurement value accumulated in the accumulation unit.