Reference Limiting for Integral Controllers Under Actuator Saturation
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Solution Overview
Problem
Existing anti-wind-up techniques for integral controllers in automotive electronic control systems face challenges in effectively managing actuator saturation, leading to delays and instability, particularly in controlling longitudinal dynamics of motor vehicles, and are limited in applicability to only PID or PI controllers.
Innovation Solution
An innovative anti-wind-up technique with a reference resolver that limits the reference input to the controller based on actuator saturation limits, ensuring the actuator operates within its linear range, using inverse transformations of the control law to compute admissible reference limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing anti-wind-up techniques are used to manage actuator saturation, then the controller can handle saturation conditions, but the system experiences delays and instability in response
Solution Approach 1:
The patent applies preliminary action by computing and limiting the reference input before it reaches the integral controller. The reference resolver calculates admissible reference limits based on actuator saturation characteristics and current system state, preventing the integral term from accumulating excessive values that would cause wind-up. This proactive approach eliminates the need for corrective anti-wind-up actions during saturation, thereby preventing response delays and instability.
2Reliability
If existing anti-wind-up techniques are used, then actuator saturation can be managed, but the techniques are limited to only PID or PI controllers
Solution Approach 1:
The patent achieves universality by designing a reference resolver that is controller-agnostic. The resolver computes admissible reference limits based on the actuator's saturation characteristics and the current system state, without depending on the specific controller structure. This allows the technique to be applied to any controller type (PID, PI, or other configurations) while maintaining effectiveness in preventing actuator saturation and ensuring stable operation.
3Speed
If the reference input is not limited, then the controller can respond to all reference changes, but the actuator operates in saturation and causes instability
Solution Approach 1:
The patent implements feedback by continuously monitoring the current system state (actuator output, process variables) and using this information to dynamically compute admissible reference limits. The reference resolver adjusts the reference input in real-time based on feedback from the system, ensuring that reference changes are accepted at full speed when the actuator is in its linear range, while automatically limiting references that would drive the actuator into saturation and cause instability.
Data Source
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AI summary
An automatic electronic control system (1) to closed-loop control a dynamic system (2). The automatic electronic control system (1) is designed to receive a control quantity representative of a reference (r(t)) to be followed by the dynamic system (2) and a controlled quantity representative of an output (y(t)) of the dynamic system (2) and to output an output (v(t)) to be supplied to the dynamic system (2) to cause the output (y(t)) thereof to follow the reference (r(t)). The automatic electronic control system (1) comprises an actuator (3) to control the dynamic system (2) and a controller (4) to control the actuator (4) based on a control law (f(e(t)). The controller (4) is configured to receive an error (e( t)) indicative of a deviation of the output (y(t)) of the dynamic system (2) from the reference (r(t)) and to output, based on the error (e(t)) and on the control law (f(e(t)) implemented by the controller (4), an output (u(t)) to be supplied to the actuator (3) to cause it to control the dynamic system (2) so that its output follows the reference (r(t)). The actuator (3) is configured to receive the output (u(t)) of the controller (4) and to output an output to be supplied to the dynamic system (2) to cause the output (y(t)) hereof to follow the reference (r(t)). The automatic electronic control system (1) is further designed to implement an anti-wind-up system (5) designed to cause the output (u(t)) of the controller (4) to be such as to cause the actuator (3) to operate in a linearity range of its input/output characteristic. The anti-wind-up system (5) is further designed to cause the excursion of the reference (r(t)) to be limited within an excursion range to cause the actuator (3) to operate in the linearity range of its input/output characteristic.