Predictive Control Input Filtering for Vibration-Safe Positioning
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Solution Overview
Problem
Existing control systems face challenges in suppressing vibrations during high-speed positioning of control objects, leading to increased positioning time and deteriorated followability, especially when target commands change in real-time.
Innovation Solution
A control device employing model predictive control with a filter unit for attenuation and an integrator, which forms an extended control object to predict and optimize control inputs based on a prediction model that includes state variables related to the control object, filter state, and jerk input, to minimize vibration and steady-state deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If feedback control is used to cause the control object to follow the command trajectory, then the control system is simple to implement, but the actual trajectory deviates from the command trajectory due to response delay in servo motors
Solution Approach 1:
The patent applies preliminary action by calculating optimal control inputs in advance over a prediction horizon. The model predictive control unit computes a sequence of future control inputs based on the prediction model and evaluation function, then applies the first control input from this sequence. This allows the system to anticipate and compensate for response delays before they cause trajectory deviations, rather than reacting after the deviation occurs.
2Manufacturing precision
If model predictive control is used to prevent trajectory deviation, then trajectory accuracy is improved, but steady-state deviation occurs when the target constantly changes
Solution Approach 1:
The patent implements feedback by incorporating the current state of the control object into the prediction model and evaluation function at each control step. The model predictive control unit continuously updates the prediction based on actual state measurements and recalculates the optimal control sequence. This closed-loop feedback mechanism allows the system to adapt to changing targets and eliminate steady-state deviations while maintaining trajectory accuracy.
3Object-affected harmful factors
If terminal state control is used to suppress vibration during positioning, then vibration is reduced, but the control input must be determined in advance and cannot adapt to real-time target changes
Solution Approach 1:
The patent applies dynamics by making the control system adaptive and flexible rather than fixed. The model predictive control unit recalculates the optimal control sequence at each control step based on current state and target information. This dynamic recalculation allows the system to suppress vibration by optimizing control inputs while simultaneously adapting to real-time target changes, overcoming the rigidity of predetermined terminal state control.
4Speed
If high-speed positioning is performed according to the target command, then positioning speed is improved, but vibration occurs immediately before positioning and followability deteriorates
Solution Approach 1:
The patent applies preliminary action by predicting future states and optimizing control inputs over a prediction horizon before the actual positioning occurs. The model predictive control unit calculates control sequences that anticipate vibration issues and adjust inputs proactively. This allows high-speed positioning to be maintained while vibration is suppressed through advance planning of control actions.
Solution Approach 2:
The patent implements feedback by continuously monitoring the actual state of the control object and updating the prediction model at each control step. This real-time feedback allows the system to detect vibration trends and adjust control inputs dynamically, maintaining both high positioning speed and good followability by responding to actual system behavior rather than relying solely on predetermined commands.
Data Source
AI summary
The present invention is a control device which includes a filter unit for performing an attenuation process at a predetermined frequency on a control input based on a predetermined target command, generates the control input through model predictive control executed by a model predictive control unit and causes an output of a predetermined control object to follow the predetermined target command. A prediction model defines a correlation between the control input and predetermined extended state variables including a state variable related to a predetermined control object and a predetermined filter state variable related to the filter unit, and a predetermined evaluation function for model predictive controls configured to calculate a state quantity cost that is a stage cost with respect to state variables except the predetermined filter state variable among the predetermined extended state variables, and a control input cost that is a stage cost related to the control input.