Gearbox Inertia Estimation Using Maximum Gear Ratio
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Solution Overview
Problem
Existing inertia estimation methods in motor control systems suffer from inaccuracies due to varying gear ratios, leading to significant estimation errors, especially when the gear ratio is small, making precise control of the movable portion's inertia challenging.
Innovation Solution
An inertia estimation apparatus and method that involves performing acceleration/deceleration operations with a changed gear ratio, specifically at the maximum gear ratio, to accurately estimate the inertia of a movable portion comprising a motor, gearbox, and a member to be driven, using the motor's acceleration and output torque to calculate the workpiece inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inertia estimation is performed using existing methods with varying gear ratios, then the estimation process can be implemented, but the estimation accuracy deteriorates significantly when the gear ratio is small
Solution Approach 1:
The patent changes the gear ratio parameter from its normal operating value to a maximum gear ratio specifically for the inertia estimation process. This parameter change ensures that the estimation is performed under optimal conditions (maximum gear ratio) where estimation accuracy is highest, then the estimated inertia value is used for control at any gear ratio. The solution directly addresses the contradiction by modifying the operating parameter during the measurement phase.
2Measurement precision
If the gear ratio is changed to maximum gear ratio for inertia estimation, then the estimation accuracy is improved, but the operation time and system complexity increase
Solution Approach 1:
The patent performs inertia estimation as a preliminary action before actual machining operations begin. By completing the gear ratio change and inertia estimation in advance (before workpiece machining), the time loss does not affect production efficiency. The estimated inertia value is then stored and reused for control during subsequent operations, making the process efficient despite the initial time investment.
Data Source
AI summary
An inertia estimation apparatus that estimates the inertia of a movable portion including a motor, a gearbox, and a member to be driven includes a controller configured to estimate the inertia of the movable portion based on an acceleration a and an output torque τ of the motor, and a gear ratio R (R=m/n), which is a ratio of an output-side velocity m with respect to an input-side velocity n, of the gearbox when the motor is caused to perform an acceleration/deceleration operation for estimating inertia. The controller is configured to cause execution of the acceleration/deceleration operation for estimating the inertia in a state in which the gear ratio R is changed to a gear ratio for estimating inertia.