Variable Rate Wireless Sensor for Battery Life Extension
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Solution Overview
Problem
Existing load control systems face challenges in efficiently managing electrical loads using battery-powered wireless sensors due to high power consumption from frequent RF signal transmissions, which shortens battery life and limits their use in retrofit installations where running additional wires is undesirable.
Innovation Solution
Implementing a sensor system that transmits wireless signals only when significant errors occur between sampled and predicted parameter values, using a variable transmission rate based on parameter changes, thereby reducing unnecessary transmissions and conserving battery power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor transmits digital messages frequently to ensure accurate load control, then the control accuracy is improved, but the battery life is shortened due to high power consumption
Solution Approach 1:
The transmission rate of the sensor is made dynamic rather than fixed. The controller adjusts the transmission frequency based on the rate of change of the measured parameter. When the parameter changes rapidly, transmission frequency increases to maintain control accuracy. When the parameter is stable, transmission frequency decreases to conserve battery power. This dynamic adaptation resolves the contradiction between maintaining accurate control and extending battery life.
Solution Approach 2:
The system changes the transmission parameter (transmission interval) based on the measured parameter's behavior. By monitoring whether the parameter is changing rapidly or slowly, the system adjusts the transmission interval accordingly. This parameter change strategy allows the system to maintain control accuracy when needed while extending battery life during stable conditions.
2Speed
If the sensor transmits digital messages at a high rate to capture rapid parameter changes, then the response speed is improved, but the energy consumption increases
Solution Approach 1:
The transmission rate is dynamically adjusted based on the rate of change of the measured parameter. When rapid changes are detected, the transmission rate increases to improve response speed. When changes are slow, the transmission rate decreases to reduce power consumption. This dynamic adjustment resolves the contradiction between response speed and energy consumption.
Solution Approach 2:
The sensor employs periodic transmission with variable intervals rather than continuous transmission. The transmission occurs at periodic intervals that are adjusted based on parameter stability. This periodic action with adaptive intervals maintains system responsiveness while significantly reducing average power consumption compared to continuous high-rate transmission.
3Loss of energy
If the sensor uses a fixed low transmission rate to conserve battery power, then the energy efficiency is improved, but the control accuracy deteriorates during rapid parameter changes
Solution Approach 1:
The system transitions from a fixed transmission rate to a dynamic transmission rate that adapts to parameter changes. When parameter changes exceed a threshold, the transmission rate automatically increases to maintain control accuracy. This dynamic behavior allows the system to achieve high energy efficiency during normal operation while maintaining control accuracy during rapid changes.
Solution Approach 2:
The controller monitors the rate of change of the measured parameter and uses this feedback to adjust the transmission rate. When the parameter changes rapidly, the feedback triggers increased transmission frequency to maintain control accuracy. This feedback mechanism ensures that energy efficiency is optimized during stable conditions while control accuracy is maintained during dynamic conditions.
Data Source
AI summary
A sensing device transmits wireless signals when an error between at least one sampled parameter value and at least one predicted parameter value is too great, such that the sensing device transmits wireless signals to a load control device using a variable transmission rate that is dependent upon the amount of change in a value of the parameter. The sensing device uses the one or more estimators to determine the predicted parameter value, and may transmit the estimators to the load control device if the error is too great. The load control device uses the estimators to determine at least one estimated parameter value and controls the electrical load in response to the estimated parameter value. The sensing device may comprise, for example, a daylight sensor for measuring a total light intensity in the space around the sensor or a temperature sensor for measuring a temperature around the sensor.