Valve Actuator Backlash Compensation via Dual-Sensor Feedback
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Solution Overview
Problem
Valve actuators face inefficiencies due to gear wear, controller saturation, wind-up, and stick-slip issues, leading to control loop instability and high costs associated with high-grade gears and expensive motors.
Innovation Solution
A valve actuator design utilizing two sensors for feedback control, a PID controller, and a high-speed control loop to overcome stick-slip problems, combined with a failsafe mechanism using ultra-capacitors for power during failures, and a locking latch for maintaining position without power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-grade gears and expensive stepper motors are used to minimize backlash, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical solutions (high-grade gears, expensive stepper motors) with a control-based approach. A sensor detects actual valve position, and a controller calculates and commands motor positions to compensate for backlash, achieving precision through software control rather than mechanical perfection.
Solution Approach 2:
The patent implements feedback control by sensing actual valve position and using this information to adjust motor positioning commands. The controller calculates the effect of backlash and compensates for it dynamically, creating a closed-loop system that maintains precision without requiring expensive mechanical components.
2Measurement precision
If high-grade gears and low gear ratio are used to reduce backlash, then control precision is improved, but productivity decreases due to longer operation time
Solution Approach 1:
The patent applies preliminary action by pre-calculating backlash compensation values and incorporating them into motor positioning commands before execution. This allows the system to move the valve directly to the correct position without waiting for mechanical backlash to naturally resolve, maintaining both speed and precision.
3Force
If controller saturation is used to overcome heavy initial load, then force capability is improved, but stability deteriorates due to wind-up action and overshoot
Solution Approach 1:
The patent applies dynamics by making the controller adaptive - it changes its behavior based on operating conditions. The controller detects when backlash compensation is needed and adjusts its output accordingly, preventing saturation and wind-up while maintaining the ability to overcome heavy loads when necessary.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves high accuracy and reliability while reducing costs by eliminating the need for expensive gears and providing a cost-effective, torque/thrust-controlled failsafe mechanism, enhancing control precision and stability.
Implementation Method 1
A valve actuator design utilizing two sensors for feedback control, a PID controller, and a high-speed control loop to overcome stick-slip problems, combined with a failsafe mechanism using ultra-capacitors for power during failures
Implementation Method 2
A valve actuator design utilizing two sensors for feedback control, a PID controller, and a high-speed control loop to overcome stick-slip problems
Data Source
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AI summary
A valve actuator having an electric drive motor with a motor shaft and having an output shaft linked to the motor shaft to drive movement of a valve, the actuator further having a control system arranged to provide a first closed loop control of the actuator output shaft and including a controller coupled to a first position sensor to sense the position of the actuator output shaft, and to a second position sensor to sense the position of the motor shaft and to enable determination of the speed of the motor shaft, the control system being configured to respond to sensed signals from the first and second sensors and adjust the motor speed/ position accordingly.