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Actuators and sensors: terminology and ontology

From: <Laurent.Lefort@csiro.au>
Date: Mon, 1 Feb 2010 21:29:26 +1100
To: <simon.cox@jrc.ec.europa.eu>, <Michael.Compton@csiro.au>
CC: <public-xg-ssn@w3.org>
Message-ID: <B484B32EAEABE14AA5409575229CECF3A68A6F3741@EXNSW-MBX05.nexus.csiro.au>
Hi Simon,

Your definition (which is roughly aligned with the SWE practice - see below) but fails to capture the idea that an actuator is providing a control capability (which is somewhat present in the Wikipedia definition and implicit in IEEE P1451). Have a look at the definitions below (1).

Please also note that the references I have recently added to the wiki e.g. OntoCAPE and the papers by Garbacz and Borst et al. cover some of the tricky issues we have discussed in recent teleconfs. More info in (2). 

I hope this helps.


(1) I have added the relevant IEEE 1451 definitions of the SWE terms page to contrast them with the SensorML ones (this was on my TO DO list): http://www.w3.org/2005/Incubator/ssn/wiki/SWE_terms 

Actuator (SensorML): A type of transducer that is a simple element that converts a signal to some action or real world phenomenon. In SensorML a actuator is a particular type of Process Model.

actuator (IEEE P1451): A transducer that accepts an electrical signal and converts it into a physical action.

Sensor (SensorML): An entity capable of observing a phenomenon and returning an observed value. In SensorML, modeled as a specific type of System representing a complete Sensor. This could be for example a complete airborne scanner which includes several Detectors (one for each band).

sensor (IEEE P1451): A transducer which converts a physical, biological, or chemical parameter into an electrical signal.

smart actuator(IEEE P1451): An actuator version of a smart transducer.

smart sensor(IEEE P1451): A sensor version of a smart transducer.

smart transducer(IEEE P1451): A transducer that provides functions beyond those necessary for generating a correct representation of a sensed or controlled quantity. This functionality typically simplifies the integration of the transducer into applications in a networked environment.

Transducer (SensorML): An entity that receives a signal as input and outputs a modified signal as output. Includes detectors, actuators, and filters.

Transducer (IEEE P1451): A device converting energy from one domain into another. The device may either be a sensor or an actuator.

Note: IEEE 1451 and Wikipedia are roughly consistent. See http://www.w3.org/2005/Incubator/ssn/wiki/Wikipedia_terms  

Actuator (Wikipedia) An actuator is a mechanical device for moving or controlling a mechanism or system. An actuator typically is a mechanical device that takes energy, usually created by air, electricity, or liquid, and converts that into some kind of motion.

Transducer (Wikipedia) A transducer is a device that converts one type of energy to another. The conversion can be to/from electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy. While the term transducer commonly implies use as a sensor/detector, any device which converts energy can be considered a transducer.


(2) These references can help us to clarify those aspects which are at the frontier between sensors and actuators: http://www.w3.org/2005/Incubator/ssn/wiki/Metrology_(hard_and_soft)#Ontology_.28practical.29 

Garbacz defines the following function hierarchy which helps to explain why the opposition of sensors vs. actuators cannot be used in a general context. 

Control Magnitude

Garbacz, P. 2006. Towards a standard taxonomy of artifact functions. Appl. Ontol. 1, 3-4 (Aug. 2006), 221-236. http://www.pawelgarbacz.webpark.pl/taxonomy.pdf page 7-8

OntoCAPE defines Sensor Function and Actuator Functions as: 
- Actuator function transforms the output of the controller into the input of the controlled system.
- Sensor function comprises the entire function of recording, relaying, and writing out process quantities within other control components.

A. Wiesner, J. Morbach, A. Yang, B. Bayer, W. Marquardt Chemical Process Systems Technical Report LPT-2008-29  July 2008

The OWL files and documentation of OntoCAPE (which represents a significant effort that we should take into account) are available from here: http://www.avt.rwth-aachen.de/AVT/index.php?id=730 

The OntoCAPE designers cite the work by Borst who separates the component, process and EngMath aspects of the model. 
See Figure 3.1 of the PhD thesis page 43 (or 27) and Figure 3.11: Interdependencies between the component, process and mathematical ontologies [.] a component is the carrier of physical processes that are described by mathematics.

J. Morbach, B. Bayer, A. Wiesner, A. Yang, W. Marquardt OntoCAPE 2.0 The Upper Level July 2008 http://www.avt.rwth-aachen.de/AVT/fileadmin/files/Service_software/Software_Simulation/The_Upper_Level.pdf 

im Borst, Hans Akkermans, Anita Pos and Jan Top The PhysSys Ontology for Physical Systems http://www.qrg.northwestern.edu/papers/Files/qr-workshops/QR95/Borst_1995_PhysSys_Ontology_Physical_Systems.pdf  
Pim Borst and Hand Akkermans (1997) Engineering ontologies Int . J . Human - Computer Studies (1997) 46 , 365 - 406 http://doc.utwente.nl/18019/1/Borst97engineering.pdf  
W. N. Borst Construction of Engineering Ontologies for Knowledge Sharing and Reuse, PhD Thesis Enschede http://doc.utwente.nl/17864/   

From: public-xg-ssn-request@w3.org [mailto:public-xg-ssn-request@w3.org] On Behalf Of Simon Cox
Sent: Monday, 1 February 2010 6:59 PM

Transducer is the general class that includes both sensors and actuators. 
However, actuators only generate mechanical effects. 
I don't think there is a general term for the inverse of sensor - i.e. a device that converts a (electrical) signal into another kind of effect. 
Received on Monday, 1 February 2010 10:30:07 UTC

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