Dynamic Deadband Control for On-Off Precision and Equipment Wear
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Solution Overview
Problem
On-off control systems face challenges in determining optimal deadband values, leading to suboptimal performance due to either limit cycling from small deadbands or compromised comfort from large deadbands, regardless of system type.
Innovation Solution
An on-off control system that includes a deadband controller capable of generating an optimal deadband value by minimizing a cost function, which considers factors like mean squared error, peak-to-trough amplitude, and equipment wear, using extremum seeking control and empirical relationships to adjust the deadband value dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a small deadband value is used in an on-off controller, then the control precision is improved, but limit cycling occurs causing equipment wear and reduced reliability
Solution Approach 1:
The deadband value is made dynamic rather than fixed. The system continuously adjusts the deadband value based on real-time system state, operational conditions, and performance metrics. This dynamic adjustment allows the controller to maintain small deadband values for precision when appropriate while increasing deadband values when limit cycling is detected, thereby preventing equipment wear and improving reliability
Solution Approach 2:
The system implements feedback mechanisms that monitor control precision, equipment operation cycles, and system performance. This feedback is used to continuously optimize the deadband value, allowing the system to learn from past performance and adjust the deadband to prevent both precision loss and excessive equipment cycling, thus resolving the contradiction between precision and reliability
2Reliability
If a large deadband value is used in an on-off controller, then equipment wear is reduced, but control precision deteriorates leading to compromised comfort
Solution Approach 1:
The deadband value transitions from a static large value to a dynamic parameter that adapts to current system needs. By continuously adjusting the deadband based on system state and performance feedback, the system can maintain larger deadband values when equipment protection is prioritized while reducing deadband values when precision and comfort are critical, thus resolving the contradiction between reliability and precision
3Device complexity
If a fixed deadband value is used, then device complexity is reduced, but adaptability to different operating conditions deteriorates
Solution Approach 1:
The controller implements self-service by automatically adjusting its own deadband value based on monitored system performance and operational conditions. This self-adjusting capability eliminates the need for manual intervention or complex external tuning mechanisms, maintaining relatively simple device architecture while achieving high adaptability to varying operating conditions through autonomous optimization
Data Source
AI summary
An on-off control system includes on-off equipment configured to operate in either an on state or an off state, an on-off controller configured to cause the equipment to transition between the on state and the off state based on a setpoint value and a deadband value to drive a control variable toward the setpoint value, and a deadband controller, according to some embodiments. In some embodiments, the deadband controller is configured to generate the deadband value used by the on-off controller. In some embodiments, the deadband controller is configured to generate the deadband value by obtaining a cost function that defines a cost based on at least a set of control values and the deadband value and selecting the deadband value that results in an optimal value of the cost function over a range of possible deadband values, the selected deadband value defining an optimal deadband value.