| 1. |
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| 2. |
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| 3. |
- Borg, Johan, et al.
(författare)
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Projekt: ESIS
- 2010
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Annan publikation (populärvet., debatt m.m.)abstract
- Samlingsprojekt för alla ESIS-projekt
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| 4. |
- Delsing, Jerker, et al.
(författare)
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The IP-meter, design concept and example implementation of an Internet enabled power line quality meter
- 2000
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Ingår i: Smart connectivity: integrating measurement and control. - Piscataway, NJ : IEEE Communications Society. - 0780358902 ; , s. 657-660
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Konferensbidrag (refereegranskat)abstract
- An Internet Protocol enabled meter, IP-meter, has been designed. As an example of the IP-meter a power line quality meter fully accessible over the Internet has been implemented. The meter is capable of measuring line frequency harmonics with spectral information, transients, line voltage RMS with sags and swells analysis. The Internet access for this application is made over a thin Ethernet medium. The Internet connection is made with a three part design concept: sensor part, microprocessor part and communication part. Served by the built in Webserver the meter is fully accessible via a standard internet browser. Meter setup, data display etc. are made using html pages and Java applets.
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| 5. |
- Enohnyaket, Mathias, et al.
(författare)
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Characteristic signature of electromagnetic emissions from power converters
- 2009
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Ingår i: 2009 IEEE Vehicle Power and Propulsion Conference. - Piscataway, NJ : IEEE Communications Society. - 9781424426003 ; , s. 1036-1042
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Konferensbidrag (refereegranskat)abstract
- Switching operations in power converters controlling electric machines in a hybrid drive train constitute a major source of electromagnetic related disturbances. The emissions from power converters seem to have a characteristic pattern or signature and can be picked up at different locations in the vehicle. This study aims at investigating the signature of emissions from power converters using an H-bridge driving a dc motor. PSpice model of the motor and drive circuit was made and current, voltage, and field measurements were performed on a constructed prototype. Current transients and oscillations generated during voltage transitions have been investigated using the PSpice model. A correlation between the common mode currents and the magnetic field emissions was observed.
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| 6. |
- Enohnyaket, Mathias, et al.
(författare)
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Parameter characterization of low frequency pulsating emissions from space vector PWM drives
- 2011
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Ingår i: Proceedings of 2010 IEEE Vehicle Power and Propulsion Conference, VPPC 2010. - Piscataway, NJ : IEEE Communications Society. - 9781424482207
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Konferensbidrag (refereegranskat)abstract
- Power converters in hybrid electric drives constitute a major source of electromagnetic disturbances. Recent studies have established that the space vector PWM scheme commonly employed in drive systems, generates low frequency pulsating (LFP) emissions, at a frequency of 6f0, where f0 is the fundamental frequency the phase voltages. The switching of voltage vectors generates common mode current (icm) spikes due to the presence of stray capacitances and inductances. Across sector boundaries, the icm spikes superpose forming spikes of double or tipple amplitude which constitute the LFP emissions. These pulsating emissions could pose EMC issues, and functionality issues like torque pulsations and speed fluctuations that could affect the reliability of the drive. This paper investigates the effects of drive speed, load, and converter slew rates, on the amplitude of the LFP emissions, using theoretical models.
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| 7. |
- Fredriksson, Håkan, et al.
(författare)
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GIMnet on the MICA wheelchair
- 2010
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes the implementation of GIMnet on the MICA wheelchair.
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| 8. |
- Fredriksson, Håkan, et al.
(författare)
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Gyro feedback of a hydraulic steering system
- 2011
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Ingår i: International Journal of Vehicle Autonomous Systems. - 1471-0226 .- 1741-5306. ; 9:3/4, s. 189-202
-
Tidskriftsartikel (refereegranskat)abstract
- We study the problem to steer, teleoperated as well as autonomously, a tractor that is to operate on a rough and slippery surface. The main idea is to control the effective steering angle of the vehicle. A benefit with this approach is that the vehicle will strive to move in a predefined way irrespective of the surface conditions. To test if the approach is usable we implemented a straight forward p-controller in combination with an estimator of the effective steering angle of the tractor. Our tests indicates that the approach can be useful. Future work would include studies on more advanced control strategies and estimators to reduce some of the problems that we address.
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| 9. |
- Fredriksson, Håkan, et al.
(författare)
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Multisource flash system for retroreflective beacon detection in CMOS cameras
- 2008
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 47, s. 103001-
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Tidskriftsartikel (refereegranskat)abstract
- We present a method for improving a flash system for retroreflective beacon detection in CMOS cameras. Generally, flash systems are designed in such a manner that makes them suited for beacon detection in a small range interval. We strive to increase the flash system range interval by exploiting the directional properties of the retroreflector. Thus, light sources placed relatively far away from the optical axis of the camera will contribute only when the retroreflector is far away. This fact can be used to compensate for the 1/distance2 dependency of optical power. We present underlying theory and formulae, then describe a flash system consisting of several light-emitting diodes that was designed by considering the presented method. Simulations show that the usable flash range of the improved system can be almost doubled compared to a general flash system. Tests were performed indicating that the presented method works according to theory and simulations.
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| 10. |
- Fredriksson, Håkan, et al.
(författare)
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Range data in vehicle dynamic simulation
- 2009
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Konferensbidrag (refereegranskat)abstract
- This paper presents a way to merge range data into the vehicle dynamic simulation software CarSim7.1. The range data consists of measurements describing the surface of a road, and thus, creates a close to reallife 3D simulation environment. This reduces the discrepancy between the real life tests and simulation ofvehicle suspension systems, dampers, springs, etc. It is important for the vehicle industry to represent a reallife environment in the simulation software in order to increase the validity of the simulations and to studythe effects that uneven roads have on the systems. Furthermore, a 3D environment based on real life data isalso useful in driving simulators, when for example, analysing driver behaviour, testing driver response, andtraining for various driving conditions. To measure and collect data, a car was equipped with instruments anda computer. On top of the car, a SICK LMS200 2D lidar was mounted tilted downwards, facing the roadin front of the car. To create the 3D environment, all the individual measurements were transformed to aglobal coordinate system using the pose (position and orientation) information from a high-class navigationsystem. The pose information made it possible to compensate for the vehicle motion during data collection.The navigation system consisted of a GPS/IMU system from NovAtel. To reach high navigation performance,the raw GPS/IMU data were post-processed and fused with data from three different fixed GPS base stations.The range data were modified with a Matlab script in order to parse the data into a file that could be read byCarSim software. This created the 3D road used in the vehicle dynamic simulations. The measurements werecollected at a go-kart track in Lule°a, Sweden. Finally, tests have been performed to compare simulation resultsbetween using a 2D surface (i.e. flat) and a 3D surface (close to real life). It is seen that the simulation resultsusing the 2D surface is clearly different from the 3D surface simulation.
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| 11. |
- Fredriksson, Håkan, et al.
(författare)
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snowBOTS: a mobile robot on snow covered ice
- 2007
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Ingår i: Proceedings of the 13th IASTED International Conference on Robotics and Applications. - Anaheim, Calif. : ACTA Press. - 9780889866850 ; , s. 222-228
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Konferensbidrag (refereegranskat)abstract
- We introduce snowBOTs as a generic name for robots working in snow. This paper is a study on using scan ning range measuring lasers towards an autonomous snow cleaning robot, working in an environment consisting al most entirely of snow and ice. The problem addressed here is using lasers for detecting the edges generated by "the snow meeting the road". First the laser data were filtered using his togram/median to discriminate against falling snowflakes and small objects. Then the road surface was extracted us ing the range weighted Hough/Radon transform. Finally the left and right edges of the road was detected by thresh olding. Tests have been made with a laser on top of a car driven in an automobile test range just south of the Arctic Circle. Moreover, in the campus area, the algorithms were tested in closed loop with the laser on board a robotized wheelchair.
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| 12. |
- Fredriksson, Håkan, et al.
(författare)
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snowBOTs: Gyro guided steering of a teleoperated tractor during winter conditions
- 2008
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This article describes the steering system implemented on the tractor IceMaker I. No direct position feedback is used for the steering angle of the front wheels. Instead, the steering angle is estimated by a motion model of the vehicle using gyro and odometer information. This estimated angle is used as feedback to a regulator that controls the steering system. The operator sets the requested steering angle and the regulator controls the hydraulic steering system to maintain the requested steering angle. Within certain limits, the tractor can be expected to behave according to the motion model irrespective of the surface conditions. The tractor can be teleoperated from a remote computer through a wireless network, WLAN. To enable teleoperation, the tractor has been equipped with a computer, some sensors, and other necessary equipment. During teleoperation, the operator controls the steering angle of the front wheels and the speed of the tractor using a joystick. The steering system has been tested both during winter conditions on a low friction surface and also on dry asphalt. The results indicates good performance when teleoperating the tractor. When driving carefully it is possible to operate the tractor up to full speed (25km/h). However, the steering regulator tends to exaggerate the real steering angle during sharp turns when driving on very slippery surface.
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| 13. |
- Fredriksson, Håkan, et al.
(författare)
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Track loader kinematics
- 2010
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Ingår i: Preprints. - Timisoara : Ed. Politehnica. ; , s. 139-142
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Konferensbidrag (refereegranskat)abstract
- We study the problem to teleoperate a Caterpillar 973c track loader. The track loader and a system for teleoperation are described. A tested and working kinematic model used for dead reckoning is also presented. Track speed sensors combined with a rate gyro are used as input to the model. The model shows good results when tested and compared to a GPS navigation system.
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| 14. |
- Hakapää, Liisa, et al.
(författare)
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MICA - Mobile Internet Connected Assistant
- 2005
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Ingår i: First International Conference on Lifestyle, Health and Technology. - Luleå : Luleå tekniska universitet.
-
Konferensbidrag (refereegranskat)
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| 15. |
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| 16. |
- Hyyppä, Kalevi
(författare)
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Competition - an efficient method to get students committed
- 2004
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Ingår i: Proceedings. - Los Alamitos, Calif : IEEE Communications Society. - 0769521819 ; , s. 211-215
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Konferensbidrag (refereegranskat)abstract
- The mechatronics course at Lulea University of Technology is divided into a traditional part with lectures, problem solving, lab exercises, and a project part. During 2002-2003, the project has been to design and build autonomous model race cars. A public race is arranged at the end of the course. The race track is an outdoor track. In year 2002, it was defined by a painted white line on asphalt. In 2003, it was defined by an electrical wire carrying 100 mA of current at 10 kHz frequency. The students had to design and build sensors, amplifiers, filters and interface circuits for the onboard PICI6F876 microcontroller as well as some power electronics to control the drive DC-motor. The race is obviously extremely challenging for the students and as a result, they spend much more time on the course than before.
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| 17. |
- Hyyppä, Kalevi
(författare)
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Design considerations in a laser navigation system for mobile robots
- 1994
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Ingår i: Mechatronics (Oxford). - : Elsevier BV. - 0957-4158 .- 1873-4006. ; 4:2, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- A navigation system for mobile robots is discussed. The system utilizes a laser anglemeter which measures heading angles to beacons made of retroreflective tape. It is shown that the motion restrictions of a typical mobile robot can be utilized to simplify the angle measurement task considerably. Beam properties of typical HeNe-lasers and collimated GaAs-laser diodes are discussed. The collimated GaAs-laser is shown to be superior for the anglemeter. A design rule is given for the anglemeter receiver optics. Noise sources in the anglemeter receiver are discussed. Reference is made to a new low-noise photodiode-amplifier circuit which has the photodiode in the feedback path.
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| 18. |
- Hyyppä, Kalevi
(författare)
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Dielectric absorption in memory capacitors
- 1972
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; IM-21:1, s. 53-56
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Tidskriftsartikel (refereegranskat)abstract
- Experience from experiments with a sample and hold circuit showed that dielectric absorption constitutes a fundamental limitation of the accuracy in analog memories. To gain more insight into the problem several materials commonly used as dielectrics in capacitors have been investigated. The theory of dielectric absorption is discussed. Results from measurements on capacitors with paper, cellulose acetate, parylene, polyester, polycarbonate, and polystyrene dielectrics are reported. The components in Dow's model, which describes the dielectric absorption, are calculated for the polycarbonate dielectric. A compensation circuit is suggested, which considerably reduces the effect of dielectric absorption in analog memories and electronic integrators.
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| 19. |
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| 20. |
- Hyyppä, Kalevi, et al.
(författare)
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Low-noise photodiode-amplifier circuit
- 1994
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Ingår i: IEEE Journal of Solid-State Circuits. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9200 .- 1558-173X. ; 29:3, s. 362-365
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Tidskriftsartikel (refereegranskat)abstract
- A photodiode-amplifier circuit with the photodiode in the feedback path is presented. It is named the PIF-circuit. No resistor is needed at the amplifier input to provide a path to ground for the signal and leakage currents from the photodiode and the amplifier input bias current. Therefore, one potentially dominating noise source is eliminated. At frequencies below 10 kHz, the implemented PIF-circuit has an NEP≈3 fW/√Hz
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| 21. |
- Hyyppä, Kalevi
(författare)
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Lulea Turbo Turtle (LTT)
- 1989
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Ingår i: The Autonomous Mobile Robots and Its Applications. ; , s. 620-623
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Konferensbidrag (refereegranskat)
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| 22. |
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| 23. |
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| 24. |
- Hyyppä, Kalevi
(författare)
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On a laser anglemeter for mobile robot navigation
- 1993
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A laser anglemeter for use in a navigation system for mobile robots has been developed. The anglemeter measures heading angles to beacons made of vertical stripes of retroreflective tape. The anglemeter uses an- optical system with a rotating mirror. It scans a laser beam which illuminates the beacons and receives pulses of reflected light from them. The pulses are amplified by a low-noise amplifier and then fed to a comparator. When the comparator trips it is assumed that the laser beam has hit a beacon. Then the angle is measured with a counter which is fed with pulses from an incremental encoder fixed on the axis of the mirror. A navigation system using the anglemeter has been developed. The system includes an algorithm that associates measured angles with beacon identities. The algorithm has been patented by the author. The navigation system has been implemented on a test vehicle. The optical and electronic parts of the anglemeter have been thoroughly analysed and simulated. The performance limits of the anglemeter are stated and design criteria for the optical and electronic parts are proposed. Measurements support the simulations and the theoretical analysis. Some results of the analysis of the optical part of the anglemeter are: A Gaussian expression describing the bidirectional reflection distribution function (BRDF) of the beacons is proposed. The shape and power of the received light pulses from the beacons are found to be determined by the (Gaussian) intensity distribution and the divergence of the laser beam, the scan velocity, the width of the beacons and their BRDFs. No signal is received from beacons at close range. At long range the laser beam diameter is much larger than the width of the beacons which causes the range-dependence of the width of the received pulses to disappear. The shape of the pulses is approximately Gaussian in this region due to the intensity distribution of the laser beam. The width of the pulses is determined by the laser beam divergence and the scan velocity. Optical misalignments in the anglemeter cause the dominating systematic error in measured angles. Another important error source is the range dependence of the received signal. Furthermore a non-circular cross-section of the laser beam is a potential source of large systematic errors while random errors due to electronic noise are surprisingly small. Some results of the analysis of the electronic part of the anglemeter axe: A low-noise photodiode-amplifier circuit with the photodiode in the feedback path has been developed. No noise generating resistor is needed to provide a DC-path to ground for signal and bias currents at the amplifier input. It is possible to design the amplifier as a matched filter for square shaped pulses. An implementation of the amplifier was found to have a NEP~ 3 fW/√Hz at frequencies below 10 kHz.
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| 25. |
- Hyyppä, Kalevi
(författare)
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Optical navigation system using passive, identical beacons
- 1987
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Ingår i: Intelligent autonomous systems. - Amsterdam : Elsevier. - 0444701680 ; , s. 737-741
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Konferensbidrag (refereegranskat)abstract
- A prototype of an optical navigation system for autonomous vehicles has been built. It consists of an He-Ne laser, a rotating mirror, an incremental encoder, a receiving optical system, a low-noise detection system and some controlling and computing microcomputers. The prototype is mounted on-board an experimental autonomous vehicle. The vehicle is of the tricycle type with the drive and steer functions implemented in the front wheel. The number of beacons visible from the vehicle is normally much greater than three, which is the minimum needed to evaluate the position and direction of the vehicle uniquely. This redundancy makes the system robust against false detections and blocked beacons and also improves the accuracy. Another benefit from the great number of beacons is that the pattern of angles measured to the beacons gives the position and direction of the vehicle without the beacons identities' being known before-hand. The experimental set-up and some measurement results are presented
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| 26. |
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| 27. |
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| 28. |
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| 29. |
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| 30. |
- Hyyppä, Kalevi, et al.
(författare)
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Projekt: Seende rullstol
- 2012
-
Annan publikation (populärvet., debatt m.m.)abstract
- Projektet syftar till att göra det möjligt för personer med funktionsnedsättning, som inte själva har full förmåga att styra en rullstol, att ändå nyttja den. Sensorer på rullstolen upptäcker automatiskt hinder i omgivningen och ger därmed den rörelsehindrade hjälp med styrningen.En virtuell blindkäpp som består av en haptisk robotarm kopplad till en laser som mäter avstånd till föremål i omgivningen har även tagits fram. Utifrån informationen skapas en 3D-bild som brukaren av den virtuella blindkäppen kan känna på med robotarmen.Fortsatt forskning kommer att fokusera på den virtuella vita käppen som kommer att ha en mycket längre räckvidd än en vanlig vit käpp. Vi avser att göra den handhållen så att rullstolen inte behövs som bärare av laserskanner och haptisk robot. En mycket viktig del i vår forskning är att åstadkomma en bra användarupplevelse. Synskadade, som har stor erfarenhet av den vanlig vita käppen, skall snabbt lära sig att använda den virtuella vita käppen.
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| 31. |
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| 32. |
- Hyyppä, Kalevi
(författare)
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Signal response of a laser beam scanner
- 1994
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 33:8, s. 2770-2776
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Tidskriftsartikel (refereegranskat)abstract
- A laser beam scanner, used as an angle measuring device in a particular navigation system for mobile robots, has been developed. It measures heading angles to beacons made of vertical stripes of retroreflective tape. Expressions giving the received power and energy in the pulse, which is generated when a beacon is traversed by the laser beam, are given. Measurements support the derived expressions. The shape and amplitude of the pulse are functions of the range R to the beacon, but at long range the pulse shape and width become independent of range while the dependence of the received amplitude on range becomes R-3. At long range the pulse shape is determined by the Gaussian irradiance distribution in the laser beam and the pulse width is governed by the laser beam divergence and the scanning speed. Design rules for the optimum field of view of the receiving optics and for an electrical filter, which maximizes the signal-to-noise ratio, are proposed. An expression giving a conservative estimate of the signal-to-noise ratio is derived.
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| 33. |
- Innala Ahlmark, Daniel, et al.
(författare)
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An Initial Field Trial of a Haptic Navigation System for Persons with a Visual Impairment
- 2015
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Ingår i: Journal of Assistive Technologies. - 1754-9450 .- 2042-8723. ; 9:4, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- Purpose– The purpose of this paper is to describe conceptions of feasibility of a haptic navigation system for persons with a visual impairment (VI). Design/methodology/approach– Six persons with a VI who were white cane users were tasked with traversing a predetermined route in a corridor environment using the haptic navigation system. To see whether white cane experience translated to using the system, the participants received no prior training. The procedures were video-recorded, and the participants were interviewed about their conceptions of using the system. The interviews were analyzed using content analysis, where inductively generated codes that emerged from the data were clustered together and formulated into categories. Findings– The participants quickly figured out how to use the system, and soon adopted their own usage technique. Despite this, locating objects was difficult. The interviews highlighted the desire to be able to feel at a distance, with several scenarios presented to illustrate current problems. The participants noted that their previous white cane experience helped, but that it nevertheless would take a lot of practice to master using this system. The potential for the device to increase security in unfamiliar environments was mentioned. Practical problems with the prototype were also discussed, notably the lack of auditory feedback. Originality/value– One novel aspect of this field trial is the way it was carried out. Prior training was intentionally not provided, which means that the findings reflect immediate user experiences. The findings confirm the value of being able to perceive things beyond the range of the white cane; at the same time, the participants expressed concerns about that ability. Another key feature is that the prototype should be seen as a navigation aid rather than an obstacle avoidance device, despite the interaction similarities with the white cane. As such, the intent is not to replace the white cane as a primary means of detecting obstacles.
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| 34. |
- Innala Ahlmark, Daniel, et al.
(författare)
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Den seende rullstolen
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In its current form, the white cane has been used by visually impaired people for almost a hundred years. It is an intuitive device that helps visually impaired people navigate independently. For people who, in addition to a visual impairment, also have impaired movement, this independence is not as certain. If a wheelchair or a walker is needed, human assistance might be a necessity.MICA (Mobile Internet Connected Assistant) is a computerized wheelchair that has been equipped with a laser rangefinder that can measure the distance to obstacles in the environment. This information has been used to make the wheelhair able to drive on its own, avoiding obstacles, so that users unable to drive a wheelchair themselves are able to use it.The latest addition to MICA - a virtual white cane - allows visually impaired wheelchair users to virtually touch obstacles in their environment, and thus navigate in a similar way to those using a regular white cane. This is accomplished by generating a simplified 3D model based on the data acquired from the laser rangefinder, and sending this data to a haptic device, allowing users to feel the 3D model.The virtual white cane is still in an early development stage. The first test drive of MICA with the virtual white cane (together known as "The Sighted Wheelchair") was performed on 2011-05-10. A short video called "The Sighted Wheelchair" can be found on YouTube.Future work will focus on developing the software that communicates with the laser rangefinder and the haptic device to improve the user experience. Efforts will also be made to overcome the limitations of the laser rangefinder, improving the 3D model.
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| 35. |
- Innala Ahlmark, Daniel, et al.
(författare)
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Hand-held navigation aid for visually impaired using haptic feedback
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The white cane is used by many visually impaired individuals as the primary aid for avoiding obstacles. In this it is unparalleled, but it cannot provide a large-scale view of the surroundings the way vision does. This makes navigating independently a challenge for the visually impaired. We are developing the Virtual White Cane (VWC), a device that uses sensors and haptic technologies to complement the limited view of the cane. Sensors makes it possible to probe obstacles far beyond the range of the white cane, and haptic feedback is familiar to users of the regular cane. The purpose of this device is to act as a complement to the standard cane, providing information about the surroundings that are beyond the cane's reach. This kind of extended view not only helps in anticipating obstacles, but also to navigate. The presentation will focus on the hardware of the currently developed prototype, in addition to some initial user experiences.
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| 36. |
- Innala Ahlmark, Daniel, et al.
(författare)
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Obstacle Avoidance Using Haptics and a Laser Rangefinder
- 2013
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Ingår i: 2013 IEEE Workshop on Advanced Robotics and its Social Impacts. - Piscataway, NJ : IEEE Communications Society. - 9781479923687 ; , s. 76-81
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Konferensbidrag (refereegranskat)abstract
- In its current form, the white cane has been used by visually impaired people for almost a century. It is one of the most basic yet useful navigation aids, mainly because of its simplicity and intuitive usage. For people who have a motion impairment in addition to a visual one, requiring a wheelchair or a walker, the white cane is impractical, leading to human assistance being a necessity. This paper presents the prototype of a virtual white cane using a laser rangefinder to scan the environment and a haptic interface to present this information to the user. Using the virtual white cane, the user is able to "poke" at obstacles several meters ahead and without physical contact with the obstacle. By using a haptic interface, the interaction is very similar to how a regular white cane is used. This paper also presents the results from an initial field trial conducted with six people with a visual impairment.
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| 37. |
- Innala Ahlmark, Daniel, et al.
(författare)
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Presentation of Spatial Information in Navigation Aids for the Visually Impaired
- 2015
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Ingår i: Journal of Assistive Technologies. - 1754-9450 .- 2042-8723. ; 9:3, s. 174-181
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The purpose of this article is to present some guidelines on how different means of information presentation can be used when conveying spatial information non-visually. The aim is to further the understanding of the qualities navigation aids for visually impaired individuals should possess.Design/methodology/approach: A background in non-visual spatial perception is provided, and existing commercial and non-commercial navigation aids are examined from a user interaction perspective, based on how individuals with a visual impairment perceive and understand space.Findings: The discussions on non-visual spatial perception and navigation aids lead to some user interaction design suggestions. Originality/value: This paper examines navigation aids from the perspective of non-visual spatial perception. The presented design suggestions can serve as basic guidelines for the design of such solutions.
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| 38. |
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| 39. |
- Johansson, Gustav, et al.
(författare)
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DE-Link, an antenna pointing system for stratospheric balloons
- 2005
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Ingår i: ICECS 2005. - Piscataway, N.J : IEEE Communications Society. - 9789972611001
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Konferensbidrag (refereegranskat)abstract
- The DE-Link attitude determination and pointing system onboard stratospheric balloons provides a low cost, low weight and high accuracy method to increase the efficiency of WLAN communication between balloon and ground station. By determination of the 6-dimensional pose of the balloon gondola in real-time, the WLAN antenna can be pointed toward a known position on the ground. This removes the need for power-consuming omnidirectional antennas. It also gives an improvement in communication speed and reduction of overall weight by the removal of heavy RF power amplifiers. The design uses a combination of GPS receivers, accelerometers and magnetoresistive circuits to determine the absolute attitude and position of the gondola in real-time, and two DC motors to point the antenna in azimuthand elevation directions to compensate for the movements of the gondola. Ground based tests have shown the system to function well with a pointing error of less than ±2 deg.
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| 40. |
- Johnsson, Helena, et al.
(författare)
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En pedagogisk idé för ingenjörsutbildningarna vid Luleå tekniska universitet
- 2009
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Konferensbidrag (refereegranskat)abstract
- Utmärkande för Luleå tekniska universitet (LTU) har länge varit närheten mellan studenterna och lärarna vilket har manifesterats genom klassrumsundervisning, lärartillgänglighet, mindre studiegrupper, koncentrerade campus etc. Undervisningsformerna har dock ändrats till att idag omfatta dels klassiska föreläsningar i stora studentgrupper, men också projektarbete i team där totalt sett 1/3 av all undervisning vid Luleå tekniska universitet sker i projektform. En fråga har ställts: Har Luleå tekniska universitet idag en gemensam pedagogisk idé för ingenjörsutbildningarna? I så fall är ytterligare en fråga hur denna pedagogiska idé tar sig uttryck i organisationen?Intervjuer med 40 aktiva lärare vid Luleå tekniska universitet har genomförts av projektgruppen (tillika författarna) varpå svaren har grupperats och analyserats i fjorton olika teman. Från dessa teman har sedan fyra hörnstenar i en definition av en pedagogisk idé aggregerats. Formuleringen av den pedagogiska idén lyder: Ett aktivt lärande för yrkeslivet – i branschnära projekt och med god vetenskaplig grund tränas förmågan att arbeta som ingenjör genom coachning från lärare i ett nära och öppet klimat. Idén har antagits av den tekniska fakultetsnämnden vid Luleå tekniska universitet och verifierats på institutionerna. Exempel på implementering och hur den pedagogiska idén aktivt verkar presenteras i artikeln.
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| 41. |
- Kozmin, Kirill, et al.
(författare)
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Memory-efficient algorithm for lens distortion compensation
- 2003
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Ingår i: Optics and Spectroscopy. - : Pleiades Publishing Ltd. - 0030-400X .- 1562-6911. ; 95:1, s. 139-141
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Tidskriftsartikel (refereegranskat)abstract
- Distortion introduced by a lens in a measurement system based on an image sensor usually must be compensated. The memory used for distortion compensation by a lookup table is proportional to the image sensor size. To reduce the memory usage, a compression algorithm is proposed and implemented.
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| 42. |
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| 43. |
- Larsson, Ulf, et al.
(författare)
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Navigating an articulated vehicle and reversing with a trailer
- 1994
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Ingår i: Proceedings, 1994 IEEE International Conference on Robotics and Automation. - Los Alamitos, Calif : IEEE Computer Society Press. - 0818653302 ; , s. 2398-2404
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Konferensbidrag (refereegranskat)abstract
- This paper describes two related tests; to navigate an articulated lawn mower and to reverse a mobile robot with a trailer. In both cases the vehicles are to follow a prespecified trajectory. The navigation principal is based on measured directions to several identical beacons, consisting of strips of reflective tapes. The angular sensor is a rotating laser for the illumination of the beacons and a highly sensitive electro-optical receiver for detecting the directions to the beacons. A Kalman filter is used to combine the measurements from the odometers with the detected angles to the known position of the beacons. To measure the angle between the robot and the trailer the same laser was used. This was done by placing two reflective beacons on the trailer. The repeatability was within 2 centimetre at low speed. The navigation of these two different types of vehicles turns out to be, essentially, the same problem. The sensitivities are different. Emphasis is on robust state estimation
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| 44. |
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| 45. |
- Möller, Björn
(författare)
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Design, development and implementation of a mechatronic log traceability system
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis concerns a mechatronic system, designed and developed for the forest industry, to trace logs from forest to sawmill. The research is a key part of a large research project launched by the EU in 2006 called the Indisputable Key project. Wood waste during harvesting, transportation and refinement is a major concern for the wood industry worldwide. Some raw materials are not suited for specific end products, and acknowledging this late in the wood value chain is cost inefficient. Pinpointing specific raw material suitable for a particular end product could increase quality, reduce waste and environmental impact; to accomplish this, traceability is essential. To trace the raw material of a final wood product to its origin, marking and reading of the different specimens must occur at each refining stage in the wood value chain. The traceability chain can be divided into three main stages: forest to sawmill, inside the sawmill, and from sawmill to second manufacturer. The research presented here covers the first part of the wood value chain, namely, forest to sawmill. In Scandinavian countries, logs are cut to length in the forest using a harvester machine. To trace logs, a unique identity code needs to be associated with each log at harvesting time in the forest and detected before further processing at the sawmill. Earlier research using RFID transponders as code carriers have been functionally verified but too costly. Although the cost of RFID transponders is declining, alternative methods are considered a necessity. This constitutes the main driver behind this thesis. The thesis presents a promising alternative log marking method comprising a harvester saw-integrated log code printer and a sawmill code detection system. An identity code in the form of a standard matrix code is applied via the harvester saw bar during cutting. A prototype has been designed and realized and the results point towards a both time and cost efficient solution. The code detection system, to be placed in one or more locations at the sawmill, is based on vision technology and image processing to detect the applied log codes. Both log code marking and reading systems communicate with an ICT system which maintains the traceability database. A major advantage of the system is that both marking and reading is performed without any time-loss and hence do not disturb the high pace production flow in todays forestry. Also, the item cost of each code mark is very low, compared to e.g.a transponder. The marking technology is patent pending. A field test was performed in December 2009 in northern Sweden. A test batch of 320 logs was marked and read. Two code structures (i.e., matrix and barcode) were applied, where 210 barcoded logs were used to demonstrate log traceability between forest and sawmill. This result indicates that this technology has potential. The prototype is not intended for commercial use, but serves merely to demonstrate the potential of the method; further research is needed to improve its functionality.
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| 46. |
- Nayl, Thaker
(författare)
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Modeling, control and path planning for an articulated vehicle
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis is focusing on the modeling, control and path planning problems for an articulated vehicle. Based on a novel error dynamics modeling approach, the nonlinear kinematic model of the vehicle has been transformed in a linear switching model representation, which is also able to take under consideration the effect of slip angles, a factor that significantly deteriorates the overall system approach.According to the proposed switching modeling, a switching model predictive control scheme has been established. Each of the controllers has been fine tuned for dealing with a specific model representation, translational speed, magnitude of slip angles and physical / mechanical constraints. In the proposed control scheme the varying slip angle and speed have been considered as the switching signal for selecting the active controller.The final contribution is related to the path planning problem where an on line path planning algorithm, being able to consider the full kinematic model of the vehicle, have been proposed.The presented algorithm is a variation of the well known Bug-like path planning scheme.The efficiencies of the presented approaches have been evaluated by multiple simulation results.
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| 47. |
- Nordin, Daniel, et al.
(författare)
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Advantages of a new modulation scheme in an optical self mixing frequency-modulated continuous-wave system
- 2002
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Ingår i: Optical Engineering. - : SPIE-Intl Soc Optical Eng. - 0091-3286 .- 1560-2303. ; 41:5, s. 1128-1133
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Tidskriftsartikel (refereegranskat)abstract
- A new frequency-modulated continuous wave modulation scheme, which gives correct results even when the Doppler shift is larger than the frequency difference associated with the range, is presented and tested with a tunable laser diode and fiber-based system. By inserting a constant frequency region in the modulation scheme, both the magnitude and the sign of all beat frequencies can be determined. When they are known, the correct frequency difference as a result of the range can be calculated. This new scheme gives more freedom when choosing the modulation parameters of the laser, because increasing the modulation frequency, and/or the frequency sweep, to avoid ambiguities resulting from a large Doppler shift no longer becomes necessary. This is especially useful when using a somewhat cheaper laser diode source, since the maximum obtainable modulation frequency and frequency sweep can be somewhat limited. The suggested modulation scheme makes it possible to use some laser diodes in an application they otherwise would not be suited for.
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| 48. |
- Nordin, Daniel, et al.
(författare)
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Dividing optical power for maximum signal-to-noise ratio in a self mixing FMCW system
- 2001
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Ingår i: Atmospheric Propagation, Adaptive Systems, and Laser Radar Technology for Remote Sensing. - : SPIE - International Society for Optical Engineering. ; , s. 289-294
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Konferensbidrag (refereegranskat)abstract
- An examination on how to divide the optical power between the local oscillator radiation and radiation sent towards the target for maximized signal-to-noise ratio, has been carried out. From the self-mixing equations, by substituting electrical fields with optical power and including relevant noise sources, an expression for the signal-to-noise ratio (SNR) for the photodiode has been obtained. From this equation the conditions for maximum SNR has been derived.
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| 49. |
- Nordin, Daniel, et al.
(författare)
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Finding the thermal time constants of a DFB laser module used in a FMCW ranging System
- 2004
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Ingår i: Proceedings of ODIMAP IV, 4th Topical Meeting on Optoelectronic Distance/Displacement Measurements and Applications. - Oulu. - 9514273680
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Konferensbidrag (refereegranskat)abstract
- In a frequency modulated continuous wave (FMCW) range and velocity-measuring system, knowledge of the thermal time constants of the laser module source is useful to obtain linear modulation. For each part of our DFB laser module a thermal resistance and capacitance were calculated, but measurements showed that our model was missing one significant time constant. FEMLAB simulations revealed that the missing time constant is of the same order of magnitude as the time it takes to heat up the area above the active region.
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| 50. |
- Nordin, Daniel, et al.
(författare)
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Single-stage photodiode op-amp solution suited for a self-mixing FMCW system
- 2003
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456 .- 1557-9662. ; 52:6, s. 1820-1824
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Tidskriftsartikel (refereegranskat)abstract
- The current delivered by the photodiode in a self-mixing frequency modulated continuous wave or optical frequency domain reflectometry system consists of a dc-current resulting from the local oscillator, the reflected signal, dark current in the photodiode, and current generated from background light. The current also contains the useful harmonic signal with a beat frequency corresponding to the range and radial velocity of a target. To avoid saturation and clipping due to the dc current generated in the photodiode, it is desirable to minimize the gain at dc while maintaining a high gain in the beat frequency region. We have investigated some different solutions and present a modified current-to-voltage converter using bootstrapping and added voltage gain, which addresses this problem using only one OP-amp and no dc shorting inductors.
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