Electronic Mixing-Valve Faucet Control Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electronic thermostatic mixing valves in households face instability and safety issues due to varying inlet conditions, such as temperature and pressure fluctuations, which affect the control of mixed water stream parameters, leading to potential overheating and reduced response times.
Innovation Solution
The implementation of a household electronic mixing-valve faucet with multiple temperature and pressure sensors, a controller that calculates desired valve coefficients based on pressure differentials, and a feedback control scheme to maintain set-point temperatures and flowrates, reducing the need for flow feedback loops and enhancing system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single temperature sensor on the mixed flow is used for feedback control, then the device complexity is reduced, but the control stability and response time deteriorate due to insufficient temperature monitoring accuracy
Solution Approach 1:
The patent divides the temperature monitoring function into multiple independent temperature sensors positioned at different locations (inlet, outlet, and mixed flow). This segmentation allows each sensor to provide specific temperature data for precise control calculations, improving control stability without requiring a single complex sensor system
Solution Approach 2:
The patent introduces pressure sensors as intermediary measurement elements that work together with temperature sensors to provide comprehensive feedback. The pressure data serves as an additional parameter that enhances the accuracy of flow rate calculations and control decisions, thereby improving overall control reliability
2Object-affected harmful factors
If flow restriction devices are installed at the outlet to meet code requirements, then safety is improved, but the response time deteriorates due to reduced convection and lower flow rates
Solution Approach 1:
The patent implements preliminary control actions by continuously monitoring temperature and pressure parameters before dangerous conditions develop. The controller uses feed-forward control based on inlet temperature and pressure data to adjust valve positions proactively, maintaining safety response times despite the presence of flow restriction devices
Solution Approach 2:
The patent replaces reliance on passive mechanical flow restriction with active electronic control of valve members. The powered valves respond dynamically to sensor feedback, allowing the system to maintain appropriate flow rates and response times while still meeting safety requirements through intelligent control rather than purely mechanical restriction
3Measurement precision
If multiple temperature and pressure sensors are installed to improve measurement accuracy, then control precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent designs the controller to perform multiple functions: it processes data from multiple temperature and pressure sensors, calculates flow rates, determines valve positioning, and implements both feed-forward and feedback control. This multi-functionality consolidates what could be separate systems into a single integrated controller, improving measurement precision without proportionally increasing overall device complexity
Solution Approach 2:
The system uses the data from multiple sensors to self-regulate and optimize its own operation. The controller automatically adjusts valve positions based on real-time sensor feedback, eliminating the need for external intervention or complex manual calibration, thereby managing the complexity of multiple sensors through autonomous operation
4Manufacturing precision
If closed-loop control is implemented to maintain set point temperature, then temperature control accuracy is improved, but system stability deteriorates due to potential oscillations and overheating risks
Solution Approach 1:
The patent implements feed-forward control that uses inlet temperature and pressure measurements to predict required valve positions before the mixing occurs. This preliminary action prevents temperature deviations before they happen, avoiding the need for aggressive corrective actions that could cause oscillations and instability
Solution Approach 2:
The patent uses feedback from multiple temperature sensors to continuously monitor the mixed flow temperature and make incremental adjustments to valve positions. The feedback control works in conjunction with feed-forward control to maintain accuracy while the gradual, sensor-guided adjustments prevent overshooting and oscillations, thereby maintaining system stability
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 solution provides a robust and stable control system that maintains accurate temperature and flowrate settings across varying conditions, improving safety and response times while reducing the risk of overheating and system instability.
Implementation Method 1
a first temperature sensor and a second temperature sensor, the sensors associated with the faucet body, and operative to sense, respectively, a first temperature of a first fluid within the hot water flowpath, upstream of the first powered valve and a second temperature of a second fluid within the cold water flowpath, upstream of the second powered valve
Implementation Method 2
at least a first component of a first pressure sensor and at least a first component of a second pressure sensor, the components of the sensors associated with the faucet body, the first component of the first sensor operative to contact the first fluid within the hot water flowpath, upstream of the first powered valve, the component of the second sensor operative to contact the second fluid within the cold water flowpath, upstream of the second powered valve
Implementation Method 3
determine a first desired flowrate (Qh) of the first fluid through the hot water flowpath, and a second desired flowrate (Qc) of the second fluid through the cold water flowpath, based on a desired total mixed stream flowrate input, and a desired mixed stream temperature input
Data Source
AI summary
A household electronic mixing-valve faucet for controlling a temperature of a mixed stream discharging from the faucet, including: (a) a faucet body; (b) a controller; (c) a first powered valve fluidly connected to the hot water flowpath; (d) a second powered valve fluidly connected to the cold water flowpath; (e) an arrangement adapted to determine extents of opening of the valves; (f) temperature sensors, operative to sense a temperature of fluids within the hot and cold water flowpaths; and pressure sensors; the controller adapted to maintain a difference between an actual temperature of the mixed stream and a setpoint temperature thereof within a particular range.