In recent years, researchers have developed virtual environments, which allow more realistic human-computer interactions and have become increasingly popular for engineering applications such as computer-aided design and process evaluation. For instance, the demand for product service, remanufacture, and recycling has forced companies to consider ease of assembly and disassembly during the design phase of their products. Evaluating these processes in a virtual environment during the early stages of design not only increases the impact of design modifications on the final product, but also eliminates the time, cost, and material associated with the construction of physical prototypes. Although numerous virtual environments for assembly analysis exist or are under development, many provide only visual feedback. A real-time haptic simulation test bed for the analysis of assembly and disassembly operations has been developed, providing the designer with force and tactile feedback in addition to traditional visual feedback. The development such a simulation requires the modeling of collisions between virtual objects, which is a computationally expensive process. Also, the demands of a real-time simulation incorporating haptic feedback introduce additional complications for reliable collision detection. Therefore, the first objective of this work was to discover ways in which current collision detection libraries can be improved or supplemented to create more robust interaction between virtual objects. Using the simulation as a test bed, studies were then conducted to determine the potential usefulness of haptic feedback for analysis of assembly and disassembly operations. The following significant contributions were accomplished: (1) a simulation combining the strengths of an impulse-based simulation with a supplemental constraint maintenance scheme for modeling object interactions, (2) a toolkit of supplemental techniques to support object interactions in situations where collision detection algorithms commonly fail, (3) a haptic assembly and disassembly simulation useful for experimentation, and (4) results from a series of five experimental user studies with the focus of determining the effectiveness of haptic feedback in such a simulation. Additional contributions include knowledge of the usability and functionality of current collision detection libraries, the limitations of haptic feedback devices, and feedback from experimental subjects regarding their comfort and overall satisfaction with the simulation.

It is known that muscles possess both intrinsic and reflexive responses to stretch, both of which have been studied extensively. While much is known about heterogenic and autogenic reflexes during XER, these have not been well characterized during locomotion. In this study, we mapped the distribution of autogenic and heterogenic feedback in hindlimb extensor muscles using muscle stretch in the spontaneously locomoting premammillary decerebrate cat. We used natural stimulation and compared stretch-evoked force responses obtained during locomotion with those obtained during XER. The goal was to ascertain whether feedback was modulated between the two states. We found that heterogenic feedback pathways, particularly those emanating from MG, remained inhibitory during locomotion while autogenic feedback specifically in MG increases in gain. Furthermore, increases in MG gain were due to force-dependent mechanisms. This suggests that rather than an abrupt transition from inhibition to excitation with changes in motor tasks, these pathways coexist and contribute to maintaining interjoint coordination. Increases in autogenic gain provide a localized loading reflex to contribute to the completion of the movement. The results of these experiments are clinically significant, particularly for the rehabilitation of spinal cord injured patients. To effectively administer treatment and therapy for patients with compromised spinal reflexes, a complete understanding of the circuitry is required.

This thesis, for the first time in literature, introduces a comprehensive study about analog controller designs for MEMS vibratory gyroscopes. A controller of a MEMS gyroscope is mandatory for robust operation, which is insensitive to sensor parameters and ambient con- ditions. Errors in the controller design not only deteriorate transient performance, such as settling time and overshoot, but also cause performance degradation due to stability problems. Accordingly, true controller design for a gyroscope is critical work in terms of functionality and system performance. This thesis gives details for modeling, analysis of closed-loop sys- tems, and design procedure for drive and sense modes. Controller loops are implemented both with discrete components and in a CMOS technology as an integrated circuit. Simulation and test results verify the modeling, analysis, and design procedure discussed in this thesis. Drive mode system developed previously at METU is optimized by taking circuit imperfec- tions into account, which results in an improved transient performance of 50 msec settling time with no overshoot for a 4&mu / m drive mode oscillation amplitude. This system has a 60 phase margin with the help of the pole-zero cancellation technique. In addition, a new gener- iv ation and simple drive mode controller for tactical grade applications is designed and verified with a moderate transient performance. Two different sense mode controller design procedures are also developed according to a new base-band equivalent model derived for mismatch operation, as a new contribution to the literature. Firstly, a PID controller is designed for low frequency separation between the drive and sense modes of the gyroscope. Secondly, an integral controller is used for moderate and high mismatch amount. The controller system designed with the new base-band equivalent model improves the linearity, angle random walk, and bias instability by factors of 4, 9, and 3, respectively. Proposed drive and sense mode controllers are also designed and implemented using a 0.6&mu / m standard CMOS process. These chips are the first functional chips developed at METU de- signed for MEMS gyroscopes. Functionality of the proposed three systems, i.e., conventional drive mode controller, new generation drive mode controller, and sense mode controller, are verified with tests. The first prototypes result in 0.033 degree/sqrt/(hr) angle random walk and 3 degree/hr bias instability for open-loop operation, which is very promising and can be improved even further in future designs.

Measuring acoustic pressure gradients is critical in many applications such as directional microphones for hearing aids and sound intensity probes. This measurement is especially challenging with decreasing microphone size, which reduces the sensitivity due to small spacing between the pressure ports. Novel, micromachined biomimetic microphone diaphragms are shown to provide high sensitivity to pressure gradients on one side of the diaphragm with low thermal mechanical noise. These structures have a dominant mode shape with see-saw like motion in the audio band, responding to pressure gradients as well as spurious higher order modes sensitive to pressure. In this dissertation, integration of a diffraction based optical detection method with these novel diaphragm structures to implement a low noise optical pressure gradient microphone is described and experimental characterization results are presented, showing 36 dBA noise level with 1mm port spacing, nearly an order of magnitude better than the current gradient microphones. The optical detection scheme also provides electrostatic actuation capability from both sides of the diaphragm separately which can be used for active force feedback. A 4-port electromechanical equivalent circuit model of this microphone with optical readout is developed to predict the overall response of the device to different acoustic and electrostatic excitations. The model includes the damping due to complex motion of air around the microphone diaphragm, and it calculates the detected optical signal on each side of the diaphragm as a combination of two separate dominant vibration modes. This equivalent circuit model is verified by experiments and used to predict the microphone response with different force feedback schemes. Single sided force feedback is used for active damping to improve the linearity and the frequency response of the microphone. Furthermore, it is shown that using two sided force feedback one can significantly suppress or enhance the desired vibration modes of the diaphragm. This approach provides an electronic means to tailor the directional response of the microphones, with significant implications in device performance for various applications. As an example, the use of this device as a particle velocity sensor for sound intensity and sound power measurements is investigated. Without force feedback, the gradient microphone provides accurate particle velocity measurement for frequencies below 2 kHz, after which the pressure response of the second order mode becomes significant. With two-sided force feedback, the calculations show that this upper frequency limit may be increased to 10 kHz. This improves the pressure residual intensity index by more than 15 dB in the 50 Hz-10 kHz range, matching the Class I requirements of IEC 1043 standards for intensity probes without any need for multiple spacers.

The traveling wave ultrasonic motor is considered for use in haptic devices where a certain input-output relation is desired between the applied force and the resulting motion. Historically, DC motors have been the standard choice for this purpose. Owing to its unique characteristics, the ultrasonic motors have been considered an attractive alternative. However, there are some limitations when using the ultrasonic motor for force-feedback applications. In particular, direct torque control is difficult, and the motor can only supply torque in the direction of motion. To accommodate these limitations we developed an indirect control approach. The experimental results demonstrate that the model reference control method was able to approximate a second order spring-damper system.

Haptic-based Virtual Reality (VR) applications have many merits. What is still obscure, from the designer’s perspective of these applications, is the experience the users will undergo when they use the VR system. Quality of Experience (QoE) is an evaluation metric from the user’s perspective that unfortunately has received limited attention from the research community. Assessing the QoE of VR applications reflects the amount of overall satisfaction and benefits gained from the application in addition to laying the foundation for ideal user-centric design in the future. In this thesis, we address certain issues and concerns regarding QoE of virtual environments. In essence, we propose a taxonomy for the evaluation of the QoE for multimedia applications and in particular VR applications. The taxonomy classifies QoE related parameters into groups. The groups’ organization is generated from the definition we have adopted for the QoE which is the Quality of Service (QoS) plus the user experience (UX). We model this taxonomy using first mathematical modeling based on weighted averages and then a Fuzzy logic Inference System (FIS) to quantitatively measure the QoE of haptic virtual environments. We test both models conducting user study analysis to evaluate the QoE of a VR application. These models serve as engines that facilitate the calculation of QoE with minimal amount of users. We specifically attend to the issue of the new media, haptics, within the context of increasing the QoE of virtual environments (VE). This special attention is important for comparing the effect of tactile and kinesthetic feedback on the QoE. In accordance, we investigate a particular topic that seems to have a colossal effect on QoE throughout our analysis, which is fatigue. Our analysis involved users' studies since the main focus is on the user. The QoE for virtual environments is in its primary stages. This thesis tackles issues that are vital in dealing with and understanding the importance of QoE. The various results suggest a positive user's disposition toward haptics and virtual environments, yet there will always be obstacles and challenges such as fatigue that if minimized will enhance the QoE of haptic-based applications.

ABSTRACT Haptic devices are used to provide multi-modal data transfer between haptic users and computers in virtual reality applications. They enable humans to take force and tactile feedback from any virtual or remote objects. Haptic devices also facilitate the use of data collected from a real object in the virtual environment. Usage of the haptic devices increase more and more in industrial, educational and medical applications in parallel with development of virtual reality technology. As virtual reality technology requires interdisciplinary study with related to its application areas, it creates a lot of different specific working areas (Haptic interface design, freeform model, surgical operations in virtual environment etc.). Especially, some complex modifications which require hand-working can be performed with the system having great potential in medical applications (Brain surgery without error and operations which require great skill etc.). This is only one of the implementations of haptic devices in digital environment. Aim of this study is to design and manufacture a 7 DOF (degrees of freedom) haptic device which serves the mentioned application areas. All different haptic devices in literature have maximum 6 DOF. The designed 7 DOF haptic device has about 20% extra working space and more flexible working capability compared to the other haptic devices with the similar link lengths and joint limitations. This study is important in terms of the development of haptic devices in the world as well as spreading of haptic devices and its applications in Turkey.

Haptic-based Virtual Reality (VR) applications have many merits. What is still obscure, from the designer’s perspective of these applications, is the experience the users will undergo when they use the VR system. Quality of Experience (QoE) is an evaluation metric from the user’s perspective that unfortunately has received limited attention from the research community. Assessing the QoE of VR applications reflects the amount of overall satisfaction and benefits gained from the application in addition to laying the foundation for ideal user-centric design in the future. In this thesis, we address certain issues and concerns regarding QoE of virtual environments. In essence, we propose a taxonomy for the evaluation of the QoE for multimedia applications and in particular VR applications. The taxonomy classifies QoE related parameters into groups. The groups’ organization is generated from the definition we have adopted for the QoE which is the Quality of Service (QoS) plus the user experience (UX). We model this taxonomy using first mathematical modeling based on weighted averages and then a Fuzzy logic Inference System (FIS) to quantitatively measure the QoE of haptic virtual environments. We test both models conducting user study analysis to evaluate the QoE of a VR application. These models serve as engines that facilitate the calculation of QoE with minimal amount of users. We specifically attend to the issue of the new media, haptics, within the context of increasing the QoE of virtual environments (VE). This special attention is important for comparing the effect of tactile and kinesthetic feedback on the QoE. In accordance, we investigate a particular topic that seems to have a colossal effect on QoE throughout our analysis, which is fatigue. Our analysis involved users' studies since the main focus is on the user. The QoE for virtual environments is in its primary stages. This thesis tackles issues that are vital in dealing with and understanding the importance of QoE. The various results suggest a positive user's disposition toward haptics and virtual environments, yet there will always be obstacles and challenges such as fatigue that if minimized will enhance the QoE of haptic-based applications.

This report is aimed at setting up a virtual environment to study and analyze the force feedback during varying dynamic conditions of the virtual environment with the help of a Haptic Device ( Omega.7 ). Adequate Haptic feedback with the virtual object is also implemented. The objective of the project is to perform experiments to study how the subject tries to elude a visioproprioceptive mismatch during robotically arbitrated manipulations in virtual reality when he/she instigates an action, and then to assess the results. The study is also aimed at cognitively characterizing interaction with a virtual object, focusing particularly on stiffness. This might be of relevance for the rehabilitation field, as Virtual Reality and Haptic feedback allows fully controlled interactions and monitoring of subjects’ performances and also to specifically scrutinize how movement and force feedback influence our perception of the virtual environment. In order to set up the virtual environment, CHAI 3D is used, which is an open source set of C++ libraries for computer haptics, visualization and interactive real-time simulation [2]. / Avsikten med denna rapport är att beskriva utvecklingen av en virtuell miljö för att med hjälp av en haptisk utrustning (Omega 7) studera och analysera kraftåterkoppling under varierande dynamiska förhållanden. Haptisk återkoppling från virtuella objekt har utvecklats för detta ändamål. Målet med projektet är att med hjälp av utvecklat system genomföra experiment för att studera hur försökspersoner kan hantera bristande överensstämmelse mellan visuell och proprioceptiv återkoppling. Studien avser också kognitiv karaktärisering av mänsklig interaktion med ett virtuellt objekt, speciellt med fokus på objektets styvhet. Detta bedöms vara relevant inom rehabiliteringsområdet eftersom en virtuell verklighet i kombination med haptisk återkoppling möjliggör full kontroll över, och registrering av, hur interaktionen sker. Av speciellt intresse är att studera hur rörelse i, och kraftåterkoppling från den virtuella miljön påverkar vår upplevelse av densamma. För utveckling av den virtuella miljön har CHAI 3D använts. CHAI 3D är ett C++ bibliotek med öppen källkod avsedd för realtidssimulering av haptisk återkoppling och visualisering.

Automated vehicles (AVs) have been developing at a rapid pace over the past few years. However, many difficulties still remain for achieving full Level-5 AVs. This signifies that AVs still require human operators to intervene or assist, such as taking over control of AVs or selecting their routes. Therefore, teleoperation can be seen as a subsystem of AVs that can remotely control and supervise a vehicle when needed. However, teleoperated driving conditions are largely different from real-life driving, so remote drivers may experience different driving feedback. In such a situation, therefore, the driving behaviour and performance of remote drivers can also be impacted. The following three studies were conducted to investigate these points. First, a seamless comparative study was carried out between teleoperated and real-life driving. Driving behaviour and performance were compared in two scenarios: slalom and lane following. Significant differences in driving behaviour and performance between them were found in the study. The lane following deviation during teleoperated driving is much greater than that of real-life driving. In addition, remote drivers are more likely to drive slower and make more steering corrections in lane following manoeuvres. Second, three types of steering force feedback (SFF) modes were compared separately in both teleoperated and real-life driving to investigate the effect of SFF on driving experience. The three SFF modes consist of Physical model-based steering force Feedback (PsF), Modular model-based steering force Feedback (MsF), and No steering force Feedback (NsF). The difference between PsF and MsF is that the main forces come from different sources, namely the estimated tyre force and steering motor current, respectively. As expected, the experimental results indicate that NsF would significantly reduce the driving experience in both driving conditions. In addition, remote drivers were found to require reduced steering feedback force and returnability. Finally, the influence of motion-cueing, sound, and vibration feedback on driving behaviour and experience was studied in a virtual teleoperation platform based on the IPG CarMaker environment. The prototype of a teleoperated driving station (TDS) with motion-cueing, sound, and vibration feedback was first developed to study human factors in teleoperated driving. Then, the low-speed disturbance scenario and high-speed dynamic scenario were used separately to investigate how these factors affect driving. Experimental results indicate that sound and vibration feedback can be an important factor in speed control by providing remote drivers a sense of speed. In the low-speed disturbance scenario, motion-cueing feedback can help with road surface perception and improve the driving experience. However, it did not significantly improve driving performance in the high-speed dynamic scenario. The research conducted reveals how driving behaviour may change in teleoperated driving and how different driving feedback influences it. These results could provide guidance for improving teleoperated driving in future research and serve as a guide for policymaking related to teleoperation. / Självkörande fordon (AV) har utvecklats i snabb takt de senaste åren. Men det finns fortfarande många utmaningar innan man når  helt självkörande fordon. Följaktligen krävs fortfarande säkerhetsförare när AV-enheter är i drift och i framtida drift kan AV-enheter stöta på oväntade problem som en människa behöver lösa. Fjärrövervakning kan därför ses som ett  backupsystem, som kan fjärrstyra och övervaka fordonet när det inte fungerar. Men situationen  vid fjärrstyrning är helt annorlunda än för körning i verkligheten, där fjärroperatörer kan uppleva olik återkoppling  och känslor jämfört med körning i verkligheten. Därför kan även fjärroperatörernas körbeteende och prestanda ändras i denna situation. För att undersöka detta utfördes följande tre studier. För det första genomfördes en sömlös jämförelsestudie mellan fjärrstyrning och verklig körning. Körbeteende och prestanda jämfördes i två scenarier, nämligen slalom och linjeföljning. Signifikanta skillnader i körbeteende och prestanda hittades mellan fjärrstyrning och körning i verkligheten. Avvikelse från linjeföljning vid fjärrstyrning är betydligt större än för körning i verkligheten. Dessutom är det mer sannolikt att fjärroperatörer kör i lägre hastigheter och gör fler styrkorrigeringar vid fjärrstyrning.  För det andra jämfördes tre typer av styrkraftsåterkopplingsmodeller (SFF) separat i både fjärrstyrning och verklig körning för att undersöka SFF:s inverkan på körupplevelsen. De tre SFF-modellerna inkluderar en  modell för fysisk återkoppling (PsF), modell för modulär återkoppling (MsF) och ingen återkoppling (NsF). Skillnaden mellan PsF och MsF är att huvudkrafterna härrör från olika källor, nämligen respektive från den matematiskt uppskattade däckkraften och från styrmotorströmmen. Som förväntat tyder resultaten av experimentet på att NsF avsevärt skulle minska körupplevelsen vid både fjärrstyrning och körning i verkligheten. Vid fjärrstyrning upptäcktes också  att operatörer kräver minskad styråterkopplingskraft och returförmåga.  Slutligen studerades påverkan av rörelsestyrning, ljud och vibrationsfeedback på körbeteende och upplevelse. Prototypen av fjärrkontrolltorn  med rörelsestyrning, ljud och vibrationsfeedback utvecklades först för att studera mänskliga faktorer vid fjärrstyrning. Sedan användes ett låghastighetsscenario med störningar och det dynamiska höghastighetsscenariot separat för att undersöka hur dessa faktorer påverkar körning vid fjärrstyrning. Resultaten av experimentet indikerar att ljud- och vibrationsåterkoppling kan vara till stor hjälp för att reglera  hastigheten genom att ge operatörerna medvetenhet om hastighet. I låghastighetsscenariot kan återkoppling  från rörelsestyrning underlätta uppfattningen av vägytan och förbättra körupplevelsen. Den ökade dock inte nämnvärt dynamisk körprestanda  i hög hastighet.  Denna forskning undersöker hur körbeteendet kan förändras vid fjärrstyrning och hur olika återkopplingar till operatör påverka körning på distans. Dessa resultat kan  ge vägledning om hur man kan förbättra fjärrstyrning i framtida forskning och fungera som en referens för skapande av regler kopplat till fjärrövervakning och fjärrstyrning. / <p>QC 230504</p>