Motor Controller Inertia Estimation and Time Constant Adjustment
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Solution Overview
Problem
Conventional motor controllers face challenges in accurately estimating inertia, leading to unstable position control and inefficiencies during machining due to friction and misalignment, as they rely on estimated inertia that may differ from actual values.
Innovation Solution
A motor controller with a command generating unit, inertia estimating unit, difference computing unit, and comparing unit that adjusts the acceleration or deceleration time constant based on precise inertia estimation, using feedback information and correcting the estimation equation to match actual changes in inertia, thereby improving accuracy and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the acceleration time constant is set short to improve machining efficiency, then productivity increases, but position control stability deteriorates causing vibration
Solution Approach 1:
The patent applies dynamics by making the acceleration time constant adjustable and adaptive rather than fixed. The controller dynamically changes the acceleration time constant based on detected vibration levels, allowing short time constants for high efficiency when stable and longer time constants for stability when vibration occurs, thus resolving the contradiction between productivity and stability
Solution Approach 2:
The patent uses feedback by detecting vibration during motor operation and using this information to adjust the acceleration time constant. The vibration detection unit monitors the system state and feeds this information back to the control unit, which then modifies the acceleration time constant to maintain stability while preserving productivity
2Reliability
If inertia estimation is based on maximum loading capacity to ensure stability, then reliability improves, but measurement precision deteriorates due to friction and misalignment effects
Solution Approach 1:
The patent applies partial action by using only the necessary portion of the maximum loading capacity for estimation rather than the full capacity. By detecting actual vibration characteristics during operation and estimating inertia based on real operating conditions rather than maximum capacity, the system achieves more accurate measurements while maintaining reliability
Solution Approach 2:
The patent changes the estimation approach from using maximum loading capacity to using operation-specific parameters detected during actual machining. The controller adjusts estimation parameters based on detected vibration and operating conditions, improving measurement precision while maintaining reliability through adaptive parameter selection
Data Source
AI summary
A controller of a motor that drives a driven body, the controller includes: a command generating unit that generates a movement command for the motor; an inertia estimating unit that acquires feedback information of the motor and estimates an inertia on the basis of a predetermined estimation equation; a difference computing unit that computes a change in the inertia changed with machining based on the movement command of the command generating unit; and a comparing unit that compares a difference between the estimation results before and after the machining of the driven body estimated by the inertia estimating unit and the change in the inertia computed by the difference computing unit. the estimation equation of the inertia estimating unit is corrected on the basis of a comparison result of the comparing unit so that the difference between the estimation results matches a computation result obtained by the difference computing unit.