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Inspired by nature, swarm robotics aims to increase system robustness while utilizing simple agents. In this work, we present a novel approach to achieve decentralized coordination of forces during collective manipulation tasks resulting in a highly scalable, versatile, and robust solution. In this approach, each robot involved in the collective object manipulation task relies on the behavior of a cooperative ``virtual teammate' in a fully decentralized architecture, regardless of the size and configuration of the real team. By regulating their actions with their corresponding virtual counterparts, robots achieve continuous pose control of the manipulated object, while eliminating the need for inter-agent communication or a leader-follower architecture. To experimentally study the scalability, versatility, and robustness of the proposed collective object manipulation algorithm, a new swarm agent, Δρ is introduced which is able to apply linear forces in any planar direction. Efficiency and effectiveness of the proposed decentralized algorithm are investigated by quantitative performance metrics of settling time, steady-state error, path efficiency, and object velocity profiles in comparison with a force-optimal centralized version that requires complete information. Employing impedance control during manipulation of an object provides a mean to control its dynamic interactions with the environment. The proposed decentralized algorithm is extended to achieve a desired multi-dimensional impedance behavior of the object during a collective manipulation without inter-agent communication. The proposed algorithm extension is built upon the concept of ``virtual coordination' which demands every agent to locally coordinate with one virtual teammate. Since the real population of the team is unknown to the agents, the resultant force applied to the manipulated object would be directly scaled with the team population. Although this scaling effect proves useful during position control of the object, it leads to a deviation from the desired dynamic response when employed in an impedance control scheme. To minimize such deviations, a gradient descent algorithm is implemented to determine a scaling parameter defined on the control action. The simulation results of a multi-robot system with different populations and formations verify the effectiveness of the proposed method in both generating the desired impedance response and estimating the population of the group. Eventually, as two case studies, the introduced algorithm is used in robotic collective manipulation and human- assistance scenarios. Simulation and experimental results indicate that the proposed decentralized communication- free algorithm successfully performs collective manipulation in all tested scenarios, and matches the performance of the centralized controller for increasing number of agents, demonstrating its utility in communication- limited systems, remote environments, and access-limited objects.

This thesis investigates human behaviour when controlling Six Degree of Freedom (DoF) Interfaces. A substantial literature review forms the basis for the design of an experimental framework. An assertion is made which states that effective control interfaces will support a broad range of activity in a virtual environment. A review of motor control facilitates the design of a set of appropriate tasks and measures A series of seven experiments are presented. The series of experiments are [sic] partitioned into three studies: Object Rotation in 3DoF (three experiments); Object Manipulation in 6DoF (three experiments); Egomotion in a 3D environment (one experiment). A new rotation controller which maps 2D mouse input to 3DoF rotation is designed and implemented. It is then compared against an "integrated" 6DoF controller. The purpose of these studies is to establish an experimental paradigm that will enable designers to examine operator strategies with input devices and interfaces. From the experiments described in the studies a number of conclusions are made: (1) operator strategies cannot be identified by single measures—rather a variety of measures help disambiguate singular performance scores; (2) control strategies can be employed due to the characteristics of one interface component but can leak into behaviour with other interface components which are related in terms of the task; (3) a variety of tasks must be employed to develop a rich picture of operator behaviour with a particular interface; (4) certain characteristics of an interface can mask other performance issues when comparing interfaces; (5) travel can be analysed with a traditional tracking task; (6) the control structure of the interface must match the control structure of the task domain—if this is exceeded then in some cases performance can actually be degraded.

Coherence describes the validity of the internal rules that drive the behaviors of a virtual environment (VE) in presenting a credible scenario. A VR system with a high level of coherence could lead to strong plausibility illusion, which is a key component of the sense of presence. There are few existing studies centered around coherence, and they tend to put the user in a passive role when experiencing the VE without emphasizing on their active participation in the interaction. This dissertation makes up this gap by connecting the concept of coherence with fundamental 3D user interface design that focuses on the algorithms that map the user's actions to the VE's behaviors. Specifically, we inspect the design of coherent interactions for two complicated tasks, namely travel and object manipulation. For travel, we propose a family of redirected walking techniques called "narrative driven cell-based redirection", which lets the user traverse a VE that's much larger than the physical space without breaking the coherence of the scenario. For object manipulation, we propose the novel concept of physics coherence to capture whether an interface conforms to the rules of physics and design several novel techniques that try to balance between physics coherence and usability. Together, we provide some useful tools for designing coherent interactions and discuss how coherence affects user experience in VR interaction. / Doctor of Philosophy / To create a virtual reality (VR) experience that feels plausible, it’s important to consider the validity of the internal rules that drive the behaviors of the virtual environment (VE), which we call “coherence” of a VR system. We discuss how to support coherence in two types of fundamental VR interaction. The first one is travel, which concerns moving the viewpoint around following the user’s intention. For this task, we propose a family of novel interaction techniques called “narrative driven cell-based redirection”, which lets the user traverse a VE that’s much larger than the physical space without breaking the coherence of the scenario. The second one is object manipulation, which is about controlling a virtual object using hand input. For this task, we propose the novel concept of physics coherence to capture whether the interaction conforms to the rules of physics and design several novel techniques that try to balance between physics coherence and controllability. Together, we provide some useful tools for designing coherent interactions and discuss how coherence affects user experience in VR interaction.

Coherence describes the validity of the internal rules that drive the behaviors of a virtual environment (VE) in presenting a credible scenario. A VR system with a high level of coherence could lead to strong plausibility illusion, which is a key component of the sense of presence. There are few existing studies centered around coherence, and they tend to put the user in a passive role when experiencing the VE without emphasizing on their active participation in the interaction. This dissertation makes up this gap by connecting the concept of coherence with fundamental 3D user interface design that focuses on the algorithms that map the user's actions to the VE's behaviors. Specifically, we inspect the design of coherent interactions for two complicated tasks, namely travel and object manipulation. For travel, we propose a family of redirected walking techniques called "narrative driven cell-based redirection", which lets the user traverse a VE that's much larger than the physical space without breaking the coherence of the scenario. For object manipulation, we propose the novel concept of physics coherence to capture whether an interface conforms to the rules of physics and design several novel techniques that try to balance between physics coherence and usability. Together, we provide some useful tools for designing coherent interactions and discuss how coherence affects user experience in VR interaction. / Doctor of Philosophy / To create a virtual reality (VR) experience that feels plausible, it’s important to consider the validity of the internal rules that drive the behaviors of the virtual environment (VE), which we call “coherence” of a VR system. We discuss how to support coherence in two types of fundamental VR interaction. The first one is travel, which concerns moving the viewpoint around following the user’s intention. For this task, we propose a family of novel interaction techniques called “narrative driven cell-based redirection”, which lets the user traverse a VE that’s much larger than the physical space without breaking the coherence of the scenario. The second one is object manipulation, which is about controlling a virtual object using hand input. For this task, we propose the novel concept of physics coherence to capture whether the interaction conforms to the rules of physics and design several novel techniques that try to balance between physics coherence and controllability. Together, we provide some useful tools for designing coherent interactions and discuss how coherence affects user experience in VR interaction.

abstract: The interaction between visual fixations during planning and performance in a dexterous task was analyzed. An eye-tracking device was affixed to subjects during sequences of null (salient center of mass) and weighted (non salient center of mass) trials with unconstrained precision grasp. Subjects experienced both expected and unexpected perturbations, with the task of minimizing object roll. Unexpected perturbations were controlled by switching weights between trials, expected perturbations were controlled by asking subjects to rotate the object themselves. In all cases subjects were able to minimize the roll of the object within three trials. Eye fixations were correlated with object weight for the initial context and for known shifts in center of mass. In subsequent trials with unexpected weight shifts, subjects appeared to scan areas of interest from both contexts even after learning present orientation. / Dissertation/Thesis / Masters Thesis Biomedical Engineering 2017

The affordability and availability of fast motion cameras presents an ideal opportunity to build computer systems that create real-time feed- back loops. These systems can enable users to learn at a faster rate than traditional systems, as well as present a more engaging experience. In this dissertation, I document the development and evaluation of a real- time audio and visual feedback system for geometric poi manipulation. The goal of the system is to present an experiential and objectively su- perior learning tool when compared to traditional learning techniques in the object manipulation community. For the evaluation, I conduct an experiment that compares the feedback training system with traditional learning techniques in the object manipulation community. The results suggest that the feedback system presents a more engaging experience than traditional mirror feedback training, and conclude that further re- search is warranted.

This thesis explores social learning in mother-reared and “enculturated” capuchin monkeys (Cebus apella). At the outset a framework for understanding the social influence on learning is discussed, followed by a review of the social and cognitive abilities of capuchin monkeys, establishing the rationale for studying social learning in this species. Studies of wild capuchins suggest an important role for social learning but experiments with captive subjects have generally failed to support this. Some potential reasons for the lack of evidence in experimental settings are given. An example of using the two - method design to test social learning in acquiring behaviour by enculturated subjects is addressed. The results are related to findings with other species tested with a similar apparatus. Before testing mother-reared monkeys, an observational study of the object manipulation and tool-use repertoire of the subjects was carried out in order to facilitate the design of suitable social learning tasks for these monkeys. The first empirical study in Chapter 6 reports results of experiments with the enculturated and mother-reared capuchin monkeys employing the two -action method together with a third control group. The enculturated monkeys exhibited high fidelity copying that included the specific tool use technique witnessed while opening the foraging box. Mother-reared monkeys exhibited fidelity at a lower level, tending only to re-create the results the model had achieved. The second empirical study in Chapter 7 tested whether capuchin monkeys could show cumulative cultural learning manifested in the ability to switch from an established mode of manipulating a dipping box to a complex yet more advantageous one. Both populations were able to do so. The enculturated monkeys, as in the previous study, showed higher fidelity copying of the model. The last experiment was a preliminary study employing the “do as I do” method which was carried out with four of the enculturated monkeys. It provides suggestive evidence for at least one monkey's understanding of the task. The results of the studies are discussed in relation to previous experimental research as well as to data from capuchin monkeys in nature. The possible role of enculturation in social learning ability is considered.

The da Vinci Surgical System is one of the most established robot-assisted surgery device commended for its dexterity and ergonomics in minimally invasive surgery. Conversely, it inherits disadvantages which are lack of autonomy and haptic feedback. In order to address these issues, this work proposes an industry-inspired solution to the field of force control in medical robotics. This approach contributes to shared autonomy by developing a controller for cooperative object manipulation with force tracking utilizing available manipulators and force feedback. To achieve simultaneous position and force tracking of the object, master and slave manipulators were assigned then controlled with Cartesian position control and impedance control respectively. Because impedance control requires a model-based feedforward compensation, we identified the lumped base parameters of mass, inertias, and frictions of a three degree-of-freedom double four-bar linkage mechanism with least squares and weighted least squares regression methods. Additionally, semidefinite programming was used to constrain the parameters to a feasible physical solution in standard parameter space. Robust stick-slip static friction compensation was applied where linear Viscous and Coulomb friction was inadequate in modeling the prismatic third joint. The Robot Operating System based controller was tested in RViz to check the cooperative kinematics of up to three manipulators. Additionally, simulation with the dynamic engine Gazebo verified the cooperative controller applying a constant tension force on a massless spring-damper virtual object. With adequate model feedback linearization, the cooperative impedance controller tested on the da Vinci Research Kit yielded stable tension force tracking while simultaneously moving in Cartesian space. The maximum force tracking error was +/- 0.5 N for both a compliant and stiff manipulated object.

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