In this thesis, the problem of controlling a surgical masterand slave system with force reflection is studied. The problemof stiff contacts between the slave and the environment isgiven specific attention. The work has been carried out at KTHbased on an initial cooperation with Karolinska Sjukhuset. Theaim of the over all project is to study the possibilities forintroduction of a force reflective teleoperator in neurologicalskullbase operations for the particular task of bone millingand thereby, hopefully, increase patient safety, decreasesurgeon workload and cost forthe society. The main contributions of this thesis are: Derivation of a dynamical model of the master andoperator’s finger system and, experimental identificationof ranges on model parameter values. Based on this model, theinteraction channel controllers optimized for transparency arederived and modified to avoid the influence of the uncertainmodel parameters. This results in a three channel structure. Todecrease the influence of the uncertain parameters locally atthe master, a control loop is designed such that the frequencyresponse of the reflected force is relatively unaffected by theuncertainties, a result also confirmed in a transparencyanalysis based on the H-matrix. The developed teleoperatorcontrol structure is tested in experiments where the operatorcould alter the contact force without facing any problems aslong as the slave is in contact with the environment. As a result of the severe difficulties for the teleoperatorto move from free space motion to in-contact manipulationwithout oscillative behaviour, a new detection algorithm basedon passivity theory is developed. The algorithm is able todetect the non-passive behaviour of the actual teleoperatorinduced by the discrete change in system dynamics occurring atthe contact instant. A stabilization controller to be activatedby the detection algorithm is designed and implemented on themaster side of the teleoperator. The detection algorithm andthe stabilization controller are shown highly effective in realexperiments. All major research results presented in the thesis have beenverified experimentally. KeywordsTeleoperator, Force Feedback, Passivity, StiffContacts, Control, Robustness, Transparency, Bone Milling,Uncertainty

During the last decades, virtual environments have become very popular and are largely used in many domains as, for example, prototyping, trainings for different devices, assistance in completing difficult tasks, etc. The interaction with the virtual reality, as well as the feedback force, is assured by haptic interfaces. Generally, such systems are affected by communication and processing time-delays, resulting in a deterioration of performances. In this thesis, a complete study of the existing methods, as well as theoretical tools and new solutions, are proposed for the haptic framework. First, a comparative study, based on the experimental results obtained on a 1-dof haptic system, highlights the advantages and drawbacks of the most common control algorithms ported from teleoperation to haptics. Next, the theoretical tools needed in analyzing the stability of the delayed systems in different situations, as well as the physical limitations of the experimental platforms considered, are examined. Besides the standard case of constant time-delays, uncertainties are also considered and modeled by different types of distributions (uniform, normal and gamma distribution with gap). In the sequel, for overcoming the drawback of time-delays, two new approaches are proposed. First, the use of Smith predictor-based control is addressed and a specific solution for haptic systems is developed and discussed. The main idea is to introduce into the Smith predictor the environmental forces by using the additional information from the virtual reality regarding the distances between the controlled virtual object and other objects in the scene. To overcome the loss of performances induced by using a fixed gain in the controllers for all situations (free or restricted motions), the second approach proposes a gain-scheduling Proportional Derivative control strategy depending on the distance until a possible collision. Both approaches are experimentally validated on a 3-dof haptic platform, under different scenarios elaborated gradually from simple situations - free and restricted motion, contacts with moving objects, to more complex situations - virtual box with fixed or moving sides.

Industrial robots have been used for a long time in the industry. Despite this thedevelopment of advanced force control system using industrial robots is relativelylimited. Using force controlled robot systems expands the possibility of what canbe done with industrial robots.Previously a force feedback system for a standard industrial robot from ABBhas been developed. The system is developed towards the aircraft industry, where amounted drill machine on the robot has to fulfill the requirements in robot drillingin aircraft structures. This thesis presents experimental results and improvementsof this industrial robot system. Mechanical modifications and tests of a new endeffector are analyzed.

Computers are developed continuously to satisfy the human demands, and typical tools used everywhere for ranging from daily life usage to all kinds of research. Virtual Reality (VR), a virtual environment simulated to present physical presence in the real word and imaginary worlds, has been widely applied to simulate the virtual environment. People’s feeling is limited to visual perception when only computers are applied for simulations, since computers are limited to display visualization of data, while human senses include sight, smell, hearing, taste, touch and so on. Other devices can be applied, such as haptics, a device for sense of touch, to enhance the human perception in virtual environment. A good way to apply VR applications is to place them in a virtual display system, a system with multiply tools displays a virtual environment with experiencing different human senses, to enhance the people’s feeling of being immersed in a virtual environment. Such virtual display systems include VR dome, recursive acronym CAVE, VR workbench, VR workstation and so on. Menus with lots of advantages in manipulating applications are common in conventional systems, operating systems or other systems in computers. Normally a system will not be usable without them. Although VR applications are more natural and intuitive, they are much less or not usable without menus. But very few studies have focused on user interfaces in VR. This situation motivates us working further in this area. We want to create two models on different purposes. One is inspired from menus in conventional system and the sense of touch. And the other one is designed based on the spatial presence of VR. The first model is a two-dimensional pie menu in pop-up style with spring force feedback. This model is in a pie shape with eight options on the root menu. And there is a pop-up style hierarchical menu belongs to each option on the root menu. When the haptics device is near an option on the root menu, the spring force will force the haptics device towards to the center of the option and that option will be selected, and then the sub menu with nine options will pop up. The pie shape together with the spring force effect is expected to both increase the speed of selection and decrease the error rate of selection. The other model is a semiautomatic three-dimensional cube menu. This cube menu is designed with a aim to provide a simple, elegant, efficient and accurate user interface approach. This model is designed with four faces, including the front, back, left and right faces of the cube. Each face represents a category and has nine widgets. Users can make selections in different categories. An efficient way to change between categories is to rotate the cube automatically. Thus, a navigable rotation animation system is built and is manipulating the cube rotate horizontally for ninety degrees each time, so one of the faces will always face users. These two models are built under H3DAPI, an open source haptics software development platform with UI toolkit, a user interface toolkit. After the implementation, we made a pilot study, which is a formative study, to evaluate the feasibility of both menus. This pilot study includes a list of tasks for each menu, a questionnaire regards to the menu performance for each subject and a discussion with each subject. Six students participated as test subjects. In the pie menu, most of the subjects feel the spring force guides them to the target option and they can control the haptics device comfortably under such force. In the cube menu, the navigation rotation system works well and the cube rotates accurately and efficiently. The results of the pilot study show the models work as we initially expected. The recorded task completion time for each menu shows that with the same amount of tasks and similar difficulties, subjects spent more time on the cube menu than on the pie menu. This may implicate that pie menu is a faster approach comparing to the cube menu. We further consider that both the pie shape and force feedback may help reducing the selection time. The result for the option selection error rate test on the cube menu may implicates that option selection without any force feedback may also achieve a considerable good effect. Through the answers from the questionnaire for each subject, both menus are comfortable to use and in good control.

Automation in manufacturing has come far by using industrial robots. However, industrial robots require tremendous efforts in static calibration due to their lack of senses. Force and vision are the most useful sensing capabilities for a robot system operating in an unknown or uncalibrated environment [4]and by integrating sensors in real-time with industrial robot controllers, dynamic processes need far less calibration which leads to reduced lead time. By using robot systems which are more dynamic and can perform complex tasks with simple instructions, the production efficiency will rise and hence also the profit for companies using them. Although much research has been presented within the research community, current industrial robot systems have very limited support for external sensor feedback, and the state-of-the-art robots today have generally no feedback loop that can handle external force- or position controlled feedback. Where it exists, feedback at the rate of 10 Hz is considered to berare and is far from real-time control. A new system where the feedback control can be possible within a real-time behavior, developed at Lund Institute of Technology, has been implemented and deployed at Linköping Institute of Technology. The new system for rapid feedback control is a highly complex system, possible to install in existing robot cells, and enables real-time (250 Hz) sensor feedback to the robot controller. However, the system is not yet fully developed, and a lot of issues need to be considered before it can reach the market in other than specific applications. The implementation and deployment of the new interface at LiTH shows that the potential for this system is large, since it makes production with robots exceedingly flexible and dynamic, and the fact that the system works with real- time feedback makes industrial robots more useful in tasks for manufacturing.

<p>In this thesis, the problem of controlling a surgical masterand slave system with force reflection is studied. The problemof stiff contacts between the slave and the environment isgiven specific attention. The work has been carried out at KTHbased on an initial cooperation with Karolinska Sjukhuset. Theaim of the over all project is to study the possibilities forintroduction of a force reflective teleoperator in neurologicalskullbase operations for the particular task of bone millingand thereby, hopefully, increase patient safety, decreasesurgeon workload and cost forthe society.</p><p>The main contributions of this thesis are:</p><p>Derivation of a dynamical model of the master andoperator’s finger system and, experimental identificationof ranges on model parameter values. Based on this model, theinteraction channel controllers optimized for transparency arederived and modified to avoid the influence of the uncertainmodel parameters. This results in a three channel structure. Todecrease the influence of the uncertain parameters locally atthe master, a control loop is designed such that the frequencyresponse of the reflected force is relatively unaffected by theuncertainties, a result also confirmed in a transparencyanalysis based on the H-matrix. The developed teleoperatorcontrol structure is tested in experiments where the operatorcould alter the contact force without facing any problems aslong as the slave is in contact with the environment.</p><p>As a result of the severe difficulties for the teleoperatorto move from free space motion to in-contact manipulationwithout oscillative behaviour, a new detection algorithm basedon passivity theory is developed. The algorithm is able todetect the non-passive behaviour of the actual teleoperatorinduced by the discrete change in system dynamics occurring atthe contact instant. A stabilization controller to be activatedby the detection algorithm is designed and implemented on themaster side of the teleoperator. The detection algorithm andthe stabilization controller are shown highly effective in realexperiments.</p><p>All major research results presented in the thesis have beenverified experimentally.</p><p><b>Keywords</b>Teleoperator, Force Feedback, Passivity, StiffContacts, Control, Robustness, Transparency, Bone Milling,Uncertainty</p>

Teleoperation of hydraulic manipulators is of potential when the presence of the operator, in a remote location, is inconvenient or dangerous. Augmenting such teleoperated systems using haptic sensation will further enhance performance, safety, and convenience. The advantage of using haptic force becomes more evident when it is employed to compensate for undesirable phenomena such as existence of a delayed and lossy communication channel or excitation of the manipulator base. The focus of this thesis is on haptic-enabled control of base-excited hydraulic manipulators that are controlled through a wireless communication channel. The targeted application is live transmission line maintenance. Both unilateral and bilateral controls of teleoperated hydraulic manipulators are studied. On the unilateral front, position error is shown to be an important issue, especially when the position accuracy of the slave manipulator is violated due to fast motion of the operator’s hand at the master site, lack of responsiveness in actuation system, or poor quality of communication channel. With respect to bilateral control, three main challenges are identified, and solutions to these challenges are investigated: (i) accurate control of the slave manipulator when the communication channel is delayed and/or lossy, (ii) control of the teleoperated system when the slave manipulator is mounted atop a moving platform, and (iii) transparent force feedback to improve the position tracking of the system. First, effects of network quality and slave manipulator base excitation are examined on performance of the teleoperated system. The position error between the haptic device implement and the hydraulic manipulator end-effector is shown to increase when the network is delayed and lossy. Next, excitation of the slave manipulator base deviates the end-effector from its reference trajectory, and the position error therefore becomes larger. To alleviate the position inaccuracy, a position referenced force feedback scheme is proposed. The scheme makes the input dynamics a better match with the slave dynamics. Combined with the virtual fixture force, the virtual fixture is shown to aid the operator in following a predefined virtual fixture trajectory. Due to complexity of dynamics, performance evaluations are mostly conducted using experimental validations on actual system in a laboratory setting.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Telerobotics is a field of robotics interested in controlling robots from a distance. Incorporating visual and haptic (touch) feedback allows the operator greater accuracy in manipulating objects in a remote environment. This project endeavours to develop a telerobotic system by using two similar industrial robotic manipulators, one acting as a haptic input device (known as the Master), the other as the telerobot (known as the Slave). This project makes use of a diverse range of technologies to achieve a telerobotic system. As such it makes use of Systems Engineering and Technology Management principles to guide the development process of converting standard industrial robots into a telerobotic system that allows the operator to “see” and “feel” in the remote environment. The ability of the robot to perceive touch is accomplished by incorporating a multi-axis force and torque sensor to both industrial robots to measure any applied force or torque acting on each robot’s end-effector. A communication system is developed that receives the force and torque readings from each sensor as well as transmit the robot instructions to both Master and Slave. Haptic feedback is achieved by combining the force and torque readings from both sensors within a control system before manipulating the data into a robot instruction that is used to control both Master and Slave. Testing of the developed telerobotic system indicates that a functional system has been developed. However, several issues were identified that limit the control capabilities the operator has over the Slave and as such could lead to safety concerns. / AFRIKAANSE OPSOMMING: Telerobotika is ’n veld van robotika wat belangstel in die beheer van robotte oor ’n afstand. Die insluiting van visuele en hapties (voel) terugvoer stel die operateur instaat om voorwerpe in ’n afgeleë omgewing met hoër akkuraatheid te manipuleer. Hierdie projek streef daarna om ’n telerobotiese stelsel te ontwikkel deur gebruik te maak van twee soortgelyke industriële robot manipuleerders, een wat optree as ’n meganiese invoer toestelle (bekend as die Meester), die ander as die telerobot (bekend as die Slaaf). Hierdie projek maak gebruik van ’n verskeidenheid van tegnologieë om ’n telerobotiese stelsel te ontwikkel. Sodanig word tegnologie bestuur en stelsels ingenieurswese beginsels deur die loop van die projek geïmplementeer om die ontwikkelings proses te lei - van standaard industriële robotte tot ’n telerobotiese stelsel wat dit moontlik maak vir die operateur om te “sien” en “voel” in ’n afgeleë omgewing. Die robot se vermoë om fisiese kontak te ervaar word bereik deur middel van ’n multi-as krag en torsie sensor wat aan beide industriële robotte toegepas word. ’n Kommunikasie stelsel is ontwikkel wat die krag en torsie lesings van beide sensors kan ontvang sowel as die robot instruksies na elke robot (Meester en Slaaf) kan stuur. Haptiese terugvoer word bereik deur die krag en torsie lesings van beide sensors te kombineer in ’n beheer stelsel voordat dit verder gemanipuleer word in die form van ’n robot instruksie wat gebruik word vir die beheer van beide Meester en Slaaf. Toetsing van die ontwikkelde telerobotiese stelsel dui aan dat ’n funksionele stelsel ontwikkel is. Daar is egter verskeie kwessies geïdentifiseer wat die operateur se beheer vermoeëns oor die Slaaf beperk wat sodoende na veiligheids kwessies kan lei.

The automotive industry is currently undergoing a paradigm shift. One such example in the next generation steering is the Steer-by-Wire (SbW) technology. SbW comes with a lot of advantages but one of the big challenges is to provide the driver with a realistic steering feel. More precisely, steering feel can be defined as the relationships between the steering wheel torque, the steering wheel angle and the dynamics of the vehicle. Accordingly, the first contribution of this work will be to present transfer functions between these quantities that resemble those observed in traditional steering systems. The steering feel/feedback is then achieved by an electric motor which can be controlled by different control strategies. In this thesis three different control strategies are investigated. The first straightforward strategy is called open loop since there is no feedback controller in the system. The second strategy is torque feedback control and the third strategy is angle feedback control. All three systems are evaluated in terms of reference tracking, stability, robustness and sensitivity. Here reference tracking is defined as tracking a desired transfer function. The desired transfer function is denoted as the reference generator. When fulfilling the requirements the analysis shows that the torque feedback system has a better reference tracking than the other evaluated systems. It is also concluded that the open loop system has a compromised reference tracking compared to the torque and angle feedback systems. Since the SbW technology is still an undergoing area of research within the automotive sector this work can be used as a basis for choice of control strategy for steering feedback systems and also as a guideline for future hardware choices.

A teleoperated system of dual redundant manipulator will be controlled in this thesis. The robot used with the dual redundant manipulator in this thesis is Baxter. Baxter’s redundant robot arms are 7-degree-of-freedom arms. The problem that will be solved in this thesis is optimization of the 7-degree-of-freedom robot arms. The control algorithm of the 7-degree-of-freedom robot arms will be discussed and built. A simulation program will be built to test the control algorithm. Based on the control algorithm, a teleoperation system will be created for Baxter. The controller used is Omni, which is a six-joint haptic device. Omni will also be used to give force feedback upon collision while the user is controlling the robot. Hence, a collision force feedback system is going to be created and combined with the teleoperation system. The teleoperation system will be tested in common daily applications.