Remote Ultrasonic Occupancy Sensing for Weak Doppler Detection
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Solution Overview
Problem
Existing ultrasonic occupancy and vacancy sensors face challenges in distinguishing small-magnitude Doppler-shifted ultrasonic waves from non-Doppler-shifted waves, limiting their detection range and accuracy, especially in environments where multiple sensors are costly and complex to install.
Innovation Solution
A low-cost ultrasonic sensing system with a remote ultrasonic transmitter and receiver configuration, using a low phase-noise oscillator circuit and synchronous rectifier to enhance the detection of Doppler shifts, allowing for increased detection range without the need for multiple wall-mounted sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ultrasonic sensors are used to detect occupancy, then the sensors can detect Doppler-shifted ultrasonic waves, but the small-magnitude reflected waves from moving objects are difficult to distinguish from non-Doppler-shifted waves, limiting detection accuracy and range
Solution Approach 1:
The patent divides the ultrasonic detection system into separate transmitting and receiving units. The transmitter generates ultrasonic waves at a specific frequency while the receiver captures reflected waves. This segmentation allows independent optimization of transmission power and reception sensitivity, improving the ability to detect weak Doppler-shifted signals from moving objects without increasing overall system complexity
Solution Approach 2:
The system performs preliminary signal processing by continuously monitoring ultrasonic waves and pre-identifying potential Doppler shifts before final occupancy determination. The receiver captures ultrasonic waves and the system pre-processes these signals to enhance Doppler-shifted components, allowing more accurate distinction between moving and stationary objects while reducing the computational burden on subsequent processing stages
2Area of stationary object
If multiple wall-mounted sensors are deployed to increase detection range, then coverage area increases, but installation cost and complexity increase significantly
Solution Approach 1:
The patent transitions from a single wall-mounted sensor to a distributed configuration with separate transmitting and receiving units positioned at different locations. This dimensional change in system architecture allows the detection coverage to be expanded by strategically placing transmitter and receiver pairs throughout the space, achieving broader coverage without requiring multiple complex wall-mounted sensor assemblies
Solution Approach 2:
The ultrasonic transmitting and receiving units are designed to be multi-functional devices that can serve both as occupancy detectors and as spatial reference points. Each unit can independently transmit or receive ultrasonic waves, and the system can flexibly configure which units perform which functions based on installation requirements, reducing the need for specialized wall-mounted sensors in every location
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
The system effectively detects occupancy and vacancy conditions across larger areas with improved accuracy and reduced installation complexity, enhancing the detection range while maintaining cost-effectiveness.
Implementation Method 1
Ultrasonic sensors transmit ultrasonic waves at a predetermined frequency and analyze received ultrasonic waves to determine if there is an occupant in the space
Implementation Method 2
The received ultrasonic waves that are reflected off of moving objects will be characterized by a Doppler shift with respect to the transmitted ultrasonic waves, while the received ultrasonic waves that are produced by reflections off of the walls, ceiling, floor, and other stationary objects of the room will not have a Doppler shift
Data Source
AI summary
A low-cost, simple ultrasonic sensing system has an increased detection range. The ultrasonic sensing system may be implemented as part of a load control system for controlling the power delivered from an AC power source to an electrical load. The load control system may comprise a load control device for controlling the power delivered to the electrical load, an ultrasonic receiver for receiving ultrasonic waves characterized by an ultrasonic frequency, and an ultrasonic transmitter located remotely from the ultrasonic receiver. The load control device controls the power delivered to the electrical load in response to the ultrasonic waves received by the ultrasonic receiver. The load control device may include the ultrasonic receiver and may be a wall-mounted load control device. The ultrasonic receiver may be a wireless ultrasonic receiver for transmitting wireless signals to the load control device in response to the ultrasonic waves received by the ultrasonic receiver.