Cascaded Control Loop Anti-Windup Using Adaptive Saturation Limits
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing anti-windup systems in control loops are overly conservative and do not fully utilize actuator capabilities, leading to poor control quality and large overshoot during recovery from conditions like sticking or sluggish actuators.
Innovation Solution
An adaptive anti-windup method that calculates inner control loop requests based on actual actuator limits and converts these to outer loop anti-windup request limits using kinematic relationships, allowing for faster and more robust control without exceeding actuator saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard anti-windup systems use conservative rate and range limits based on assumed worst-case actuator capabilities, then integrator anti-windup protection is provided, but control quality deteriorates and actuator capabilities are not fully utilized
Solution Approach 1:
The patent implements dynamic adaptation of anti-windup limits by continuously monitoring actual actuator saturation conditions and adjusting the outer loop anti-windup request limits accordingly. Instead of using static conservative limits, the system dynamically modifies limits based on real-time actuator behavior, allowing full utilization of actuator capabilities while maintaining protection against integral windup.
Solution Approach 2:
The system changes the parameters of anti-windup limits from fixed conservative values to adaptive values that reflect actual actuator capabilities. By calculating inner control loop requests that would cause saturation and converting these to outer loop limits using kinematic relationships, the system optimizes control parameters to match real-world actuator performance rather than worst-case assumptions.
2Device complexity
If simple clamping of controller output to input range is used without anti-windup system, then implementation simplicity is maintained, but controller reaction is delayed and control quality becomes poor
Solution Approach 1:
The patent employs feedback mechanisms by monitoring inner control loop saturation conditions and using this information to adjust outer loop anti-windup limits. This feedback loop enables the system to respond promptly to disturbances and reference changes while preventing integral windup, thereby improving controller reaction speed without sacrificing simplicity.
3Productivity
If adaptive anti-windup calculation based on actual actuator limits is implemented, then full actuator capabilities are utilized and control performance improves, but calculation complexity increases
Solution Approach 1:
The patent segments the control system into inner and outer loops with distinct anti-windup handling. The inner loop manages actuator-level saturation with detailed calculations, while the outer loop uses simplified adaptive limits derived from inner loop saturation conditions. This segmentation allows complex calculations to be confined to where they are most needed while keeping the overall system manageable.
Solution Approach 2:
The system uses an intermediary approach by calculating inner control loop requests that would cause saturation and converting these to outer loop anti-windup request limits using kinematic relationships. This intermediary calculation method bridges the gap between detailed actuator constraints and outer loop control, providing accurate adaptive limits without requiring full complexity in every control calculation.
4Reliability
If conservative anti-windup limits are used, then protection against integral windup is ensured, but overshoot increases during recovery from sticking or sluggish actuator conditions
Solution Approach 1:
The patent implements dynamic adaptation of anti-windup limits that respond to actual actuator conditions. During recovery from sticking or sluggish actuator conditions, the system dynamically adjusts limits to allow faster response while maintaining protection against integral windup. This dynamic approach reduces overshoot by matching limits to real-time actuator capabilities rather than applying static conservative constraints.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A method of adaptive anti-windup protection for a control system (100) with cascaded inner and outer control loops (120, 140). The method includes receiving an inner loop feedback signal (126) indicative of the response of a control device (122) controlled by the inner control loop (120) and calculating an inner control loop request (124) such that, it would cause saturation of the control device (122) controlled by the inner control loop (120). The method also includes converting the calculated inner loop request (124) to outer loop anti-windup request limits using kinematic relationships and transmitting the outer loop anti-windup request limits to a controller (152) of the outer control loop (140). The method may also include applying the outer loop anti-windup request limits to the controller (152) of the outer control loop (140) to limit an inner loop request (124) generated thereby, and executing an outer control loop control law and an inner control loop control law subject to the anti-windup request limits.