Motor Inertia Correction for Stable Acceleration Time Control
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Solution Overview
Problem
Conventional motor controllers face challenges in setting acceleration or deceleration time constants based on inertia, leading to unstable position control and excessive acceleration due to friction and misalignment, as they struggle to accurately account for differences between estimated and actual inertia.
Innovation Solution
A motor controller that includes an inertia estimating unit, a computing unit, a storage unit, and a correction unit to calculate and correct acceleration or deceleration time constants using polynomial fitting based on inertia and time constant differences, ensuring the time constants fall within appropriate ranges to prevent excessive acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the acceleration time constant is set short to improve productivity, then the acceleration time is reduced and productivity increases, but the position control becomes unstable and vibration occurs
Solution Approach 1:
The patent dynamically adjusts the acceleration time constant parameter based on the relationship between commanded acceleration and actual acceleration. When the difference exceeds a threshold, the controller modifies the acceleration time constant to bring the actual acceleration closer to the commanded value, thereby maintaining stability while optimizing productivity.
Solution Approach 2:
The patent employs feedback control by continuously monitoring the difference between commanded acceleration and actual acceleration. This feedback mechanism allows the controller to detect when position control is becoming unstable and adjust the acceleration time constant accordingly, preventing vibration while maintaining efficient acceleration.
2Speed
If the acceleration time constant is set based on estimated inertia to improve response, then the acceleration response is optimized, but the estimation error causes excessive acceleration
Solution Approach 1:
The patent uses feedback from the actual acceleration measurement to correct for inertia estimation errors. By comparing commanded acceleration with actual acceleration, the system detects deviations caused by estimation inaccuracies and adjusts the acceleration time constant to compensate, ensuring accurate acceleration control despite initial estimation errors.
Solution Approach 2:
The patent performs preliminary inertia estimation to set an initial acceleration time constant, then refines this setting through continuous monitoring and adjustment. This two-stage approach allows the system to quickly establish a baseline response while subsequently correcting for estimation inaccuracies through feedback-based adjustments.
3Speed
If the gain is increased to improve position control when load inertia is large, then the control responsiveness is improved, but the system becomes sensitive to inertia estimation errors
Solution Approach 1:
The patent implements dynamic gain adjustment by making the acceleration time constant variable rather than fixed. The controller adapts the effective gain through real-time modification of the acceleration time constant based on the difference between commanded and actual acceleration, allowing the system to maintain high responsiveness while automatically compensating for inertia estimation errors.
Solution Approach 2:
The patent changes the acceleration time constant parameter dynamically based on operational conditions and measured acceleration performance. This parameter adaptation allows the control gain to effectively adjust itself, improving responsiveness when needed while maintaining stability even when inertia estimation is inaccurate.
Data Source
AI summary
A controller of a motor that drives a driven body includes: an inertia estimating unit that estimates inertia on the basis of feedback information (torque and current) of the motor; a computing unit that computes an acceleration or deceleration time constant of the motor from the estimation inertia estimated by the inertia estimating unit; a storage unit that stores an inertia difference which is a difference between the estimation inertia and at least one known actual inertia and a time constant difference which is a difference between an actual acceleration or deceleration time constant corresponding to the actual inertia and an acceleration or deceleration time constant calculated on the basis of the estimation inertia; and a correction unit that corrects the acceleration or deceleration time constant calculated by the computing unit using the inertia difference and the time constant difference stored in the storage unit.