Sensor arrays, methods, systems and devices
In one preferred form of the present invention, there is provided a road-based traffic sensor comprising: a body having a base and an upper portion; the body housing electronic components including a magnetometer and a battery; the magnetometer for monitoring changes in magnetic field; the body having a slim line configuration and being able to support heavy vehicles travelling at speed; the slim line configuration of the body having a height no more than 25 mm and housing the electronic components; the base for being adhesively secured to the upper surface of the road with negligible damage to the upper surface.
1 . A method of road traffic data collection comprising:
providing arrays of two or more wireless sensors mounted-on, in, or at a surface of a road network, each sensor including a magnetometer configured to monitor changes in magnetic field;
receiving magnetic field waveform data from information sent by the sensors;
analysing the magnetic field waveform data from each sensor by computing one or more characteristic values, indices, or signatures derived from the waveform, the analysis comprising at least one of: time-domain analysis, frequency-domain analysis, statistical analysis, or a transformation of the waveform data, wherein the characteristic values are used for event detection, classification, or sensor association;
determining traffic information including vehicle volume or vehicle speed based on the analysed data; and
compensating for sensors that have become separated from the road or are otherwise malfunctioning.
2 . A method as claimed in claim 1 , wherein the step of analysing received information includes configuring each sensor to be agnostic of its placement in the corresponding array.
3 . A method as claimed in claim 1 , including performing the analysing of the information separately of the sensors.
4 . A method as claimed in claim 1 , including the arrays sending magnetometer information to sensor gateways configured to be agnostic of the placement of the sensors.
5 . A method as claimed in claim 1 , including analysing the information separately from the sensor gateways and sensor.
6 . A method as claimed in claim 1 , including analysing the received information using combinations of sensor measurements in each array to improve accuracy.
7 . A method as claimed in claim 6 , including accounting for incorrect physical spacing measurements between the sensors in an array.
8 . A method as claimed in claim 1 , including proactively issuing alerts to report the number of sensors that are separated from the road or are otherwise malfunctioning.
9 . A method as claimed in claim 1 , comprising proactively issuing alerts when an array approaches a single functioning sensor enabling repair while the array continues to operate.
10 . A method as claimed in claim 1 , wherein the analysing includes monitoring measurements to determine whether added sensors provide measurements associated with times indicating that they should be associated with an array.
11 . A method as claimed in claim 1 , wherein sensors in each array are separated by predetermined distances, which may differ between individual sensor pairs, provided that the actual inter-sensor distances are known or determined for use in the analysing.
12 . A method as claimed in claim 1 , wherein each array comprises at least three sensors and the system is configured, upon malfunction of a sensor, to maintain at least two functioning sensors to provide redundancy, while issuing an alert for repair and continuing operation of the array.
13 . A method as claimed in claim 1 , further comprising automatically associating newly added sensors with existing arrays by correlating event timing or waveform-derived characteristics with those of sensors already in the array.
14 . A method as claimed in claim 1 , wherein the analysing includes generating a compact representation of each event comprising a reference point, a weighted-average index, or a signature vector obtained by applying a mathematical function or transformation to the waveform data, and using the compact representation for event detection, classification, or sensor association.
15 . A method as claimed in claim 1 , comprising, for each of the wireless sensors mounted on, in, or at the surface of the road network and configured to provide magnetometer-based traffic data, installing the sensor either (a) by bonding the sensor to the road using an adhesive pad without scouring or mechanically damaging the road surface, or (b) by embedding the sensor in a shallow recess formed in the road surface such that an upper surface of the sensor is coplanar with, or below, the road surface; operating the sensor using a battery housed in the sensor; and recharging the battery, while the sensor remains so installed, using solar energy received by a solar cell carried in an upper portion of the sensor, whereby the sensor is operable over an extended deployment period and is maintainable without digging up and repairing the road surface for maintenance or replacement of the sensor.
16 . A system for traffic analysis comprising:
a. arrays of two or more wireless road-based sensors mounted on, in, or at a surface of a road network, each sensor including a magnetometer;
b. a receiver configured to receive magnetic field waveform data from information sent by the sensors; and
c. an analyser configured to analyse the waveform data by computing one or more characteristic values, indices, or signatures derived from the waveform, the analysis comprising at least one of: time-domain analysis, frequency-domain analysis, statistical analysis, or a transformation of the waveform data, and to determine traffic information including vehicle volume or speed, while compensating for malfunctioning or separated sensors.
17 . A system as claimed in claim 16 , wherein sensors are agnostic of their placement and gateways are agnostic of sensor placement, the system being configured to associate sensors with one or more gateways based on signal strength and to operate with sensor/gateway associations that change over time without manual reconfiguration.
18 . A system as claimed in claim 17 , wherein the analyser is provided by a system facility that is separate from the sensor gateways and the sensors and the analyser are configured to use combinations of sensor measurements in each array to improve accuracy.
19 . A system as claimed in claim 17 , wherein the analyser is configured to account for incorrect physical spacing measurements between the sensors in an array.
20 . A system as claimed in claim 16 , including a notifier for proactively issuing alerts to report the number of sensors that become separated from the road or are otherwise malfunctioning.
21 . A system as claimed in claim 16 , including a notifier for proactively issuing alerts when an array approaches a single functioning sensor due to sensors having become separated from the road or are otherwise malfunctioning.
22 . A system as claimed in claim 16 , wherein at least some of the arrays each comprise at least three surface mounted wireless road-based sensors spaced along a corresponding section of road.
23 . A system as claimed in claim 16 , including an authorization store and authentication protocols that ensure only authorized sensors can associate with specific gateways.
24 . A system as claimed in claim 16 , wherein the sensors in each array are separated by predetermined distances, which may differ between individual sensor pairs, provided that the actual inter-sensor distances are known or determined for use in the analysis.
25 . A system as claimed in claim 16 , wherein the analysis generates a compact representation of each event comprising a reference point, a weighted-average index, or a signature vector obtained by applying a mathematical function or transformation to the waveform data, and uses the compact representation for event detection, classification, or sensor association.
26 . A system as claimed in claim 16 , wherein the sensor includes a sampler to sample changes in magnetic field by activating the magnetometer; the sampler using the sampled magnetic field to control the sampling to:
(i) provide early warning of nearby vehicular traffic; and
(ii) increasing magnetic field sampling in response thereto.
27 . A system as claimed in claim 16 , wherein the wireless road-based sensors are configured for installation on, in, or at a surface of the road network either by bonding to the road using an adhesive pad without scouring or mechanically damaging the road surface, or by embedding in a shallow recess such that an upper surface of each sensor is coplanar with, or below, the road surface; and wherein each sensor is battery-powered and includes a solar cell positioned at an upper portion of the sensor to recharge the battery while the sensor remains installed, the battery powering the magnetometer during deployment.