Active Sensor Cross-Interference Detection via Dual-Pulse Signal Processing
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Solution Overview
Problem
Cross-interference among active sensors in presence sensing systems, such as ultrasound and radio frequency sensors, affects proper operation and detection accuracy, especially in varying environments due to changes in object presence or movement, leading to sensor detection errors and interference challenges in wireless sensor networks.
Innovation Solution
A control system comprising a first active sensor transmitting a probe signal with two non-zero pulses in a timeslot and a second active sensor receiving and processing these signals to detect cross-interference by determining the difference between signal parts, allowing for improved detection and mitigation of interference without requiring the second sensor to transmit a probe signal, and enabling the addition of new sensors to the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple active sensors are deployed to improve detection coverage in large spaces, then detection coverage and reliability are improved, but cross-interference between sensors increases causing detection errors
Solution Approach 1:
The patent applies periodic action by using time-division multiplexing where sensors transmit probe signals in alternating timeslots rather than simultaneously. Each sensor has designated transmission and reception periods, creating a periodic pattern that prevents cross-interference while maintaining detection coverage across the monitored space.
Solution Approach 2:
The patent segments the operation of the sensor network into distinct timeslots, dividing the continuous monitoring task into discrete time segments. Each sensor is assigned specific timeslots for transmission and reception, segmenting the overall system operation to eliminate interference between simultaneous sensor activities.
2Object-affected harmful factors
If sensors are scheduled to avoid cross-interference by having only one sensor sense per timeslot, then cross-interference is reduced, but system complexity and synchronization requirements increase
Solution Approach 1:
The patent merges transmission and reception functions into a single integrated sensor unit that can alternately perform both functions. Each sensor combines the capabilities of transmitter and receiver, switching between modes according to the timeslot assignment, which simplifies the overall system architecture compared to having separate dedicated transmit and receive sensors.
Solution Approach 2:
The periodic timeslot structure provides a regular, predictable pattern for sensor operation that simplifies synchronization. By establishing fixed periodic intervals for transmission and reception across all sensors, the system reduces the complexity of real-time coordination while effectively preventing cross-interference.
3Object-affected harmful factors
If the timeslot period is made larger than the die-out time of ultrasonic waves to avoid interference, then cross-interference is eliminated, but detection speed and productivity decrease
Solution Approach 1:
The patent implements periodic action with carefully optimized timeslots that are just long enough to accommodate the ultrasonic wave die-out time. This periodic structure ensures complete signal clearance between transmissions while minimizing the total cycle time, thereby maintaining high detection speed without sacrificing interference elimination.
Solution Approach 2:
The system dynamically adjusts the timeslot duration parameter based on the specific ultrasonic wave characteristics and environmental conditions. By optimizing this parameter to match the actual die-out time rather than using excessive margins, the system achieves the minimum necessary period to eliminate interference while maximizing detection productivity.
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 approach enhances the performance of presence detection systems by effectively detecting and managing cross-interference, improving accuracy and system operation in dynamic environments, and facilitating the integration of new sensors into existing networks.
Implementation Method 1
active sensors, such as ultrasound based sensors
Implementation Method 2
a second active sensor comprising a receiving sensor array arranged to receive the first probe signal
Implementation Method 3
detect cross-interference between the active sensors, cross-interference being detected if the power in the difference signal has an absolute value that is larger than a predefined threshold value
Data Source
AI summary
A network of active sensors in a control system is considered. The active sensors, which may be fixed-infrastructure sensors, provide presence detection information to a distributed lighting system. The active sensors communicate by transmitting probe signals. The communication of probe signals may result in cross-interference which may vary in time. Cross-interference is detected, and can later be avoided, by determining a difference between signals received in a first part of a timeslot and signals received in a second part of the timeslot. In order to do so probe signals comprising two non-zero pulses are transmitted in respective parts of the timeslot. Applications are, for example, active presence sensors in lighting control applications in indoor as well as outdoor environments.