Digital Position Control Using Sinusoidal Constant Lookup
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Solution Overview
Problem
Conventional position control systems struggle to accurately suppress unknown disturbance frequencies in disk apparatuses, leading to ineffective position following due to the analog adaptive law being directly converted into a digital control system, which results in inadequate disturbance suppression.
Innovation Solution
A digital control module calculates the control value using a table storing control constants corresponding to sin(ωT/2), where ω is the angular frequency of the disturbance, and updates these constants based on adaptive laws to perform disturbance adaptive control, enabling precise estimation and suppression of disturbance frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an analog adaptive law is directly converted into a digital control system, then the system structure is simplified, but the disturbance suppression accuracy deteriorates
Solution Approach 1:
The patent replaces the direct digital implementation of analog adaptive law with a hybrid approach that uses a table storing pre-calculated control constants corresponding to sin(ωT/2) values. This substitution allows the digital control module to accurately estimate disturbance frequencies by referencing the table rather than directly implementing the analog mathematical operations, thereby maintaining disturbance suppression accuracy while using a digital control architecture.
Solution Approach 2:
The patent pre-calculates and stores control constants corresponding to various sin(ωT/2) values in a table before the actual control operation. This preliminary action enables the digital control module to quickly and accurately determine the appropriate control constant for the current disturbance frequency without performing complex real-time calculations, thus maintaining accuracy while simplifying the runtime control structure.
2Measurement precision
If a table storing control constants is introduced, then the disturbance suppression accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent creates a digital copy of the control constants that would otherwise be calculated in real-time through complex analog mathematics. By storing these constants in a table, the system replicates the functionality of the analog system in a digital format that is easier to implement and more accurate, without requiring complex computational hardware.
3Adaptability or versatility
If the control constant is updated based on adaptive law, then the adaptability to unknown disturbance frequencies is improved, but the calculation complexity increases
Solution Approach 1:
The patent pre-calculates and stores control constants for various disturbance frequencies in a table. When an unknown disturbance frequency is detected, the system simply looks up the corresponding constant in the table and updates the control parameter, rather than performing complex real-time calculations. This maintains adaptability to unknown frequencies while significantly reducing the computational complexity during operation.
Data Source
AI summary
According to one embodiment, a position control apparatus includes: a digital control module that performs position control including disturbance adaptive control with a predetermined sampling period with the use of a control constant, in accordance with a position error between a target position and a current position of the object; and a table that stores the control constant corresponding to a value of sin(ωT/2), wherein the digital control module determines a control value of the actuator in accordance with the position error, calculates the value of sin(ωT/2) according to an adaptive law from a signal based on the position error, reads the corresponding control constant from the table in accordance with the calculated value of sin(ωT/2), and updates the control constant.