Actuator Position Control Using Simulated Pressure Feedback
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Solution Overview
Problem
Existing control valve systems are rendered inoperative due to failures in position feedback sensors, requiring additional secondary pressure feedback controllers that need configuration and tuning, limiting their application and flexibility.
Innovation Solution
A method and controller that enable control of pneumatic or hydraulic actuators in simulated feedback mode, where a simulated position is derived from actuator pressure using a simulation model, allowing for continued operation without a primary position sensor, and automatically switching between measured and simulated feedback modes when errors exceed predefined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is used for feedback control, then positioning accuracy is improved, but system reliability deteriorates when the sensor fails
Solution Approach 1:
The system implements a simulated feedback mode that acts as a pre-prepared backup mechanism. When the position sensor fails, the controller automatically switches to using actuator pressure as a substitute feedback signal, which has been pre-configured to provide acceptable positioning performance. This cushioning mechanism ensures continuous operation without complete system failure.
Solution Approach 2:
The invention introduces actuator pressure as an intermediary substitute when the primary position sensor fails. The controller uses pressure measurements combined with a simulation model to generate a simulated position feedback signal, serving as a mediator between the failed sensor and the control algorithm, maintaining system functionality through this intermediate representation.
2Reliability
If a secondary pressure feedback controller is added to backup the primary controller, then reliability is improved, but device complexity increases
Solution Approach 1:
The invention merges the backup functionality into the existing primary controller by implementing a simulation model and automatic mode switching capability within the same device. Instead of adding a separate secondary controller, the system combines both normal operation mode and backup simulated feedback mode in one integrated controller, reducing overall system complexity while maintaining reliability.
Solution Approach 2:
The controller is designed with multi-functionality, capable of operating in both normal feedback mode using position sensors and backup simulated feedback mode using pressure measurements. This universal design allows a single controller to perform multiple functions - normal positioning control and fault-tolerant operation - eliminating the need for separate dedicated backup hardware.
3Measurement precision
If position sensors are integrated to the valve positioner, then measurement precision is improved, but ease of operation deteriorates due to installation requirements
Solution Approach 1:
The system uses actuator pressure as an intermediary measurement that can be obtained without direct attachment to the valve or actuator mechanism. Pressure sensors can be mounted remotely on pressure lines, making installation easier compared to integrated position sensors that require direct mechanical coupling. The pressure measurement serves as a mediator that provides sufficient control information without the installation complexity of direct position sensing.
Data Source
AI summary
A controller for controlling a pneumatic or hydraulic actuator of a process device includes a position feedback signal input for receiving a measured position signal representing a position of the actuator or the process device, an actuator pressure output, and a pressure sensor for measuring the actuator pressure. The controller is configured to operate in a measured position feedback mode and a simulated position feedback mode. In the measured position feedback mode the actuator is controlled dependent on a setpoint position and the measured position, and in the simulated position feedback mode the actuator is controller based on the setpoint position and a simulated position of the actuator or the process device. The simulated position is derived from the measured actuator pressure by a simulation model.