Monitor - ISSN 1472-0221
The Newsletter for PC-Based Data Acquisition and Control
Issue 205, August 2015
Welcome to Monitor, the data acquisition and control newsletter. Data acquisition doesn't just cover the measurement of physical parameters like temperature or pressure, it is wide ranging with new applications emerging all the time. This month we discuss the technical challenges of human sensing. The Excel corner is on its holidays in Ireland, but will be back next month.
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Researchers have identified five technology challenges in human sensing systems.
Thiago Teixeira, Gershon Dublon and Andreas Savvide of Yale University and Massachusetts Institute of Technology addressed the increasingly common requirement of computer systems to extract information about the people present in an environment. They pin-pointed five requirements that the most accurate systems need to meet.
Human sensing covers not just whether any people are present, but how many and where they are.
There are several methods of human sensing, including those using infra-red sensors, cameras, pressure mats, break beams, movement sensors or turnstiles.
1. Environmental Variations
Unexpected or sudden changes in environmental conditions are common sources of errors in some real-world scenarios. Radar signals, for instance, can be dampened by rain or fog. Passive infra-red sensors are often triggered by heat currents flowing through HVAC (heating, ventilation and air conditioning) systems. A large portion of the computer vision literature is aimed at dealing with variations in lighting, shadows and so forth.
Some of the most accurate human sensing systems are those employing video technology with software algorithms to differentiate people from the background. Users can configure the software for each individual sensing station: adjusting for dark shadows and changes in lighting. Tests show that video technology achieves over 98% accuracy in human sensing.
2. Similarity to Background Signal
Clearly, separating a person from the background signal is a core requirement for human-sensing the scientists write. The latest video people sensing systems freeze the background at the moment a person enters and easily distinguishes the moving person from her surroundings. Users can set in software how long a person can stand perfectly still before the system sees them as part of the background.
. In other domains, such as with ranging sensors (radars, sonars), the presence of unwanted signals with the correct frequency spectrum or timing characteristics can often fool the system into producing phantom detections.
Passive thermal sensors have problems differentiating people in warm environments. The sensor works by monitoring the temperature difference between a person and the background. If the temperature of the background and the person are similar then the sensor doesn't "see" the person. Also, if a person stands still she becomes part of the background.
3. Appearance variability and unpredictability
People look different and wear a vast assortment of different types of clothes and hats, they push trollies and pushchairs, and carry back-packs and hand-bags.
This at first looks like a problem for video systems, but is solved by the software converting an individual to a "blob".
In a tricky situation - outdoors with people pushing prams - the computer vision system simplifies the picture and accurately distinguishes people, converting them to "blobs". Screen shot courtesy Retail Sensing
4. Similarity to Other People
Some tracking systems use identifying features of a person to track them - presenting a challenge if people are all wearing similar clothes or uniforms. Video sensing technology follows the "blob" that has been identified as a person so it doesn't matter if everyone looks alike. Each blob is seen as unique and distinguished from the others, even in crowded situations.
5. Active Deception
The researchers' final point is when a human sensing system may be deliberately debilitated, perhaps by people walking slowly to fool motion sensors, covering a break beam with their hands or turning the lights off to fool the cameras. A cctv system lets users remotely play back the video over the internet to see why counting has suddenly stopped and rectify the problem.
And the best human sensing systems?
The researchers conclude that the best system is computer vision, saying "Computer vision is far ahead from other instrumented modalities not only with respect to spatial-resolution and precision metrics, but also in terms of having the most field-tested solutions".
You can read the research at A Survey of Human-Sensing: Methods for Detecting Presence, Count, Location, Track, and Identity T TEIXEIRA, G DUBLON, A SAVVIDES ENALAB technical report
How a CCTV People Counting System Works, Retail Sensing
After taking a look at Your products for data acquisition and control (https://www.windmillsoft.com/), I have been really impressed by the potentialities of these devices as well as by the fact that many of them are provided with a control software included in the price.
I was wondering whether one of such devices might fit my needs (as further described below):
I need to control the temperature on a small solid surface (2 cm x 2 cm) heated by a Peltier.
There will be a thermocouple measuring the temperature at the surface and a power supply (12V) providing voltage/current to the Peltier.
I was wondering whether your device (and related software) may be used to create "a control loop", I mean use it to adjust the voltage (or cut it temporarily) according to the temperature measured by the thermocouple, on the basis of the following scheme:
Temperature larger that a desired value -> cut or decrease voltage,
Temperature smaller than the desired value -> enable or increase voltage.
Please let me know whether this would be feasible and the most relevant device among those described at the http address reported above.
Thanking in advance
Yes, one of our systems will fit your needs. Which one depends on how you are controlling your power supply. If by an analogue input then a Microlink 752 might fit the bill, together with a 593 thermocouple connection box. To create the control loop you would need the Windmill Test Sequence software. This lets you, for example, check if a condition is true before doing something - eg if a temperature is greater than 20 oC then switch off the heater.
If the power supply was otherwise controlled a different set up might be more appropriate, but still with the Test Sequence software to create the control loop.
These web pages give more details
Any questions on using Windmill you'd like to see answered here, just ask: [email protected].
Global pressure sensor market to grow by 5%
A pressure sensor converts changes in the pressure of a gas or a liquid into an electrical signal. It then generates an analogue output proportional to the pressure, or switches a digital output when a particular pressure level is reached. Pressure sensors are used for controlling and monitoring thousands of applications. The global pressure sensor market is expected to reach USD 9.48 billion by 2020, according to Research and Markets. The primary driving force is the automotive industry's increased demand for pressure sensors.
Source: Research and Markets
Robots to measure marine wildlife
Two robotic vehicles will work together over the next three weeks to investigate why the deep area of the Celtic sea (between Ireland, UK and France) is particularly attractive to marine predators like dolphins and whales.
Source: SCUBA News
Sensor mimics bats to detect dangerous structural cracks
An ultrasound sensor for detecting dangerous cracks in structures such as aircraft engines, oil and gas pipelines and nuclear plants, has been developed by researchers at the University of Strathclyde – with inspiration from the natural world.
Source: University of Strathclyde Glasgow University
Piezo sensor predicts wind farm failure
Engineers have developed a novel technique to predict when bearings inside wind turbines will fail. The method uses ultrasonic waves to measure the load transmitted through a ball bearing in a wind turbine. The stress on wind turbine is recorded and then engineers can forecast its remaining service life. A custom-built piezoelectric sensor is mounted in the bearing to measure the time of flight of an ultrasound wave and determine the load.
Source: The University of Sheffield
Robot whiskers sense their environment
Robotic whisker detects air currents and builds two-dimensional images of what it senses using tomography, an imaging technique commonly implemented in MRI or CT scans.
The quarterly update of data acquisition and control exhibitions around the world.
14-18 September 2015
Brno Czech Republic
Industrial automation, measuring and control equipment.
Automotive Testing Expo 2015 China
15-17 September 2015
Data acquisition, engine and emissions analysis, materials testing, sensors, transducers, quality testing, environmental testing - meet test equipment manufacturers and test service providers.
SPIE Remote Sensing 2015
21-24 September 2015
For engineers, scientists and researchers to gain access to the most recent satellite-based imaging systems and the data generated by them.
Sensors and Instrumentation
30 September - 1 October 2015
For test, measurement and control.
13-14 October 2015
Automation technology, including control hardware and software.
Testing Expo 2015 North America
20-22 October 2015
Novi MI USA
Latest technologies and services to ensure that the highest standards are met in terms of product quality, reliability, durability and safety providers.
21-23 October 2015
Saint Petersburg Russia
Exhibition on industrial automation - software and hardware automation tools, control and communication systems.
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