Position and Velocity Estimation by Ultrasonic Sensor

Transcription

1 Positio ad Velocity Estimatio by Ultrasoic Sesor N Ramarao 1, A R Subramayam 2, J Chara Raj 2, Lalith B V 2, Varu K R 2 1 (Faculty of EEE, BMSIT & M, INDIA) 2 (Studets of EEE, BMSIT & M, INDIA) Abstract: Velocity ad positio are the most importat sigals used i idustrial cotrollers such as proportioal itegral derivative cotrollers. While i some real-time applicatios like structural cotrol, acceleratio measuremets are easily accessible via accelerometers. The velocity ad positio have to be estimated from the measured acceleratio. This project proposes a strategy to estimate the velocity ad positio of eighbor agets usig distace measuremets oly. I. INTRODUCTION A ultrasoic sesor trasmit ultrasoic waves ito the air ad detects reflected waves from a object. There are may applicatios for ultrasoic sesors, such as i itrusio alarm systems, automatic door opeers ad backup sesors for automobiles. Accompaied by the rapid developmet of iformatio processig techology, ew fields of applicatio, such as factory automatio equipmet ad car electroics, are icreasig ad should cotiue to do so. Usig its uique piezoelectric ceramics maufacturig techology developed over may years. A Ultrasoic sesor is a device that ca measure the distace to a object by usig soud waves. It measures distace by sedig out a soud wave at a specific frequecy ad listeig for that soud wave to bouce back. By recordig the elapsed time betwee the soud wave beig geerated ad the soud wave boucig back, it is possible to calculate the distace betwee the soar sesor ad the object. Sice it is kow that soud travels through air at about 344 m/s (1129ft/s), you ca take the time for the soud wave to retur ad multiply it by 344 meters (or 1129 feet) to fid the total roud-trip distace of the soud wave. Roud-trip meas that the soud wave traveled 2 times the distace to the object before it was detected by the sesor; it icludes the 'trip' from the soar sesor to the object AND the 'trip' from the objectto the Ultrasoic sesor (after the soud wave bouced off the object). To fid the distace to the object, simply divide the roud-trip distace i half. It is importat to uderstad that some objects might ot be detected by ultrasoic sesors. This is because some objects are shaped or positioed i such a way that the soud wave bouces off the object, but are deflected away from the ultrasoic sesor. It is also possible for the object to be too small to reflect eough of the soud wave back to the sesor to be detected. Other objects ca absorb the soud wave all together (cloth, carpetig, etc.), which meas that there is o wayfor the sesor to detect them accurately. These are importat factors to cosider whe desigig ad programmig a robot usig a ultrasoic sesor. Ultrasoic sesors emit short, high-frequecy soud pulses at regular itervals. If they strike a object, the they are reflected back as echo sigals to the sesor, which itself computes the distace to the target based o the time-spa betwee emittig the sigal ad receivig the echo.i this study, a room temperature of 20 C is assumed hece the velocity of ultrasoud i the air is take as 343m/s. because the travel distace is very short the travel time is little affected by temperature. it takes approximately 29.15μsec for the ultrasoic to propogate wave through 1cm distace; therefore it is possible to have 1cm resolutio i the system. 82 Page

2 II. EXISTING METHODS OF OBJECT TRACKING: Trackig ca be defied as the problem of approximatig the path of a object i the image plae as it moves aroud a scee. The purpose of a object trackig is to geerate the route for a object above time by fidig its positio i every sigle frame of the video. Object is tracked for object extractio, object recogitio ad trackig, ad decisios about activities. Object trackig ca be classified as poit trackig, kerel based trackig ad silhouette based trackig. For illustratio, the poit trackers ivolve detectio i every frame, while geometric area or kerel based trackig or cotours-based trackig require detectio oly whe the object first appears i the scee. Trackig methods ca be divided ito followig categories. 2.1 Poit Trackig I a image structure, movig objects are represeted by their feature poits durig trackig. Poit trackig is a complex problem particularly i the icidece of occlusios, false detectios of object. Recogitio ca be doe relatively simple, by thresholdig, at of idetificatio of these poits. 2.2 Kerel Based Trackig Kerel trackig is usually performed by computig the movig object, which is represeted by a embryoic object regio, from oe frame to the ext. The object motio is usually i the form of parametric motio such as traslatio, coformal, affie, etc. These algorithms diverge i terms of the presece represetatio used, the umber of objects tracked, ad the method used for approximatio the object motio. I real-time, illustratio of object usig geometric shape is commo. But oe of the restrictios is that parts of the objects may be left outside of the defied shape while portios of the backgroud may exist iside. This ca be detected i rigid ad o-rigid objects.they are large trackig techiques based o represetatio of object, object features,appearace ad shape of the object. 2.3 Silhouette Based Trackig Approach Some object will have complex shape such as had, figers, shoulders that caot be well defied by simple geometric shapes. Silhouette based methods afford a accurate shape descriptio for the objects. The aim of a silhouette-based object trackig is to fid the object regio i every frame by meas of a object model geerated by the previous frames. Capable of dealig with variety of object shapes, Occlusio ad object split ad merge 83 Page

3 3.1 Methodology Model III. FIGURES AND TABLES S=(c*t)/2 cm X=s2*si(b) cm Y=s1*si(a) cm r= (x²+y²); velocity = Δd/ΔtΔd =chage i positio, Δt =chage i time a ad b are agles(radia) made by servomotor preset at X ad Y axis respectively s1 ad s2 are the distaces of object(i cm) with respect to sesors preset at x ad y respectively. r distace from origi (cm) X horizotal distace (X-axis) Y vertical distace (Yaxis) Mathematical Model Implemeted Fial usig of ultrasoic sesor for fidig distace is doe by moutig ultrasoic sesor o a servomotor where two servomotors are used alog with ultrasoic sesor placed at right agles to each other as show below. 84 Page

4 3.2 Positio Estimatio S l o. Compute r time Time(ms ) S1 (cm) S2 (cm) X (c m) Y (c m) r(cm ) A gl e 1 A gl e Velocity Determiatio Highlighted row idicates the positio of object at two differet cycles of rotatio agles, the chage i distace from origi idicates that the object has bee displaced from oe positio to other positiovelocity foud for object at two differet positios Here velocity is foud for marked readigs usig excel operatios of row operatio. 85 Page

5 IV. CONCLUSION Hece by usig two ultrasoic sesors mouted o servomotor placed each at right agles are able to give the approximately positio ad velocity i the give rage. Hece velocity ad positio are estimated from the measured acceleratio. Thus this project proposes a strategy to estimate the velocity ad positio of eighbor agets usig distace measuremets oly. V. ACKNOWLEDGEMENTS The satisfactio ad euphoria that accomplished the successful completio of ay task would be icomplete without the people who made it possible, whose costat guidace ad ecouragemet crowed out effort with the success. Our deepest thaks to our guide, Dr. N R Ramarao, Associate Professor, Departmet of Electrical ad Electroics, BMSIT & Maagemet for his excellet guidace without which the successful completio of the project would have ot bee possible. I would like to express my sicere gratitude towards the Head of the Departmet, Dr. T C Balachdra ad etire staff of EEE departmet, BMSIT&M for their valuable suggestio ad guidace Heartfelt thaks to Dr. Moha Babu G.N, Pricipal, BMSIT&M for havig provided the facilities ad the edless ecouragemet.last but ot the least we thak our parets for their moral ad fiacial support without which we would ot have bee able to do this. REFERENCES Gettig Started with Arduio(3 rd editio) -Massimo Bazico-fouder of Arduio & Michael Shiloh Sesors ad Actuator with Arduio -Has-PetterHalvorse, M.Sc. Iterfacig Arduio with ultrasoic sesor alog with servomotor Parallax data acquisitio software Micro epsilo data for excistig distace sesors Examples follow: Joural Papers: [1]. Ravichadra A ad Dr. b Kalavathi Multi objects trackig methods based o particle filter ad HMM, Iteratioal Joural for treds i Egieerig ad techology volume 3 issue 1 jauary 2015 Books: [2]. Gettig Started with Arduio(3 rd editio) -Massimo Bazico-fouder of Arduio& Michael Shilo 86 Page