Generalized Scattering-Based Stabilization of Nonlinear Interconnected Systems

The research presented in this thesis is aimed at development of new methods and techniques for stability analysis and stabilization of interconnections of nonlinear systems, in particular, in the presence of communication delays. Based on the conic systems\u27 formalism, we extend the notion of conicity for the non-planar case where the dimension of the cone\u27s central subspace may be greater than one. One of the advantages of the notion of non-planar conicity is that any dissipative system with a quadratic supply rate can be represented as a non-planar conic system; specifically, its central subspace and radius can be calculated using an algorithm developed in this thesis. For a feedback interconnection of two non-planar conic systems, a graph separation condition for finite-gain L2-stability is established in terms of central subspaces and radii of the subsystems\u27 non-planar cones. Subsequently, a generalized version of the scattering transformation is developed which is applicable to non-planar conic systems. The transformation allows for rendering the dynamics of a non-planar conic system into a prescribed cone with compatible dimensions; the corresponding design algorithm is presented. The ability of the generalized scattering transformation to change the parameters of a system\u27s cone can be used for stabilization of interconnections of non-planar conic systems. For interconnections without communication delays, stabilization is achieved through the design of a scattering transformation that guarantees the fulfilment of the graph separation stability condition. For interconnected systems with communication delays, scattering transformations are designed on both sides of communication channel in a way that guarantees the overall stability through fulfilment of the small gain stability condition. Application to stabilization of bilateral teleoperators with multiple heterogeneous communication delays is briefly discussed. Next, the coupled stability problem is addressed based on the proposed scattering based stabilization techniques. The coupled stability problem is one of the most fundamental problems in robotics. It requires to guarantee stability of a controlled manipulator in contact with an environment whose dynamics are unknown, or at least not known precisely. We present a scattering-based design procedure that guarantees coupled stability while at the same time does not affect the robot\u27s trajectory tracking performance in free space. A detailed design example is presented that demonstrates the capabilities of the scattering-based design approach, as well as its advantages in comparison with more conventional passivity-based approaches. Finally, the generalized scattering-based technique is applied to the problem of stabilization of complex interconnections of dissipative systems with quadratic supply rates in the presence of multiple heterogeneous constant time delays. Our approach is to design local scattering transformations that guarantee the fulfilment of a multi-dimensional small-gain stability condition for the interconnected system. A numerical example is presented that illustrates the capabilities of the proposed design method

The Benefits of Haptic Feedback in Mobile Phone Camera

Communication is basically the act of transferring information from one place to another. Feedback is a system where the reaction or response of the receiver arrives at the sender after he/she has interpreted the message. Feedback is inevitably essential to make two way communications effective. In fact, without feedback communication remains incomplete. At times, feedback could be verbal such as written and oral. Then in some cases, it could be nonverbal. Feedback is mainly a response from your audiences; it allows you to evaluate the effectiveness of your message. In fact research shows that the majority of the messages that have been sent are nonverbal and the ability to understand and use nonverbal communication is powerful tools that will help people connect with each other. As well as communication where nonverbal shows much more impressive, a sense of touch as known as haptics plays an important role in our new phase of technology. It is the science of applying touch sensation and control to interaction with computer applications by using special input/output devices. It gives users a slight jolt of energy at the point of touch, providing instant sensory feedback, while reducing the audio, visual or audio-visual demand. Haptic technology is an evolutionary step into interacting with objects as an extension of our mind and allows for more socially appropriate and subtle interaction. In this thesis, the benefits of haptic feedback in a mobile phone camera are explored and compared to the existing feedback mechanisms. Discovering expectations from users and gathering ideas in order to improve user experience in haptic feedback of a mobile phone camera will be the main focus as well as to understand “What make end users to use or not to use mobile phone camera?” and “What qualities of haptics could be used in the design of the user interface for mobile phone camera?”. Depending on the settings and the quality of the mobile phones, the feedback from the camera can affect the user experience in many ways. I believe that to improve the existing feedback by applying haptic output such as a vibration or a vibrotactile signal may also considerably improve the user experience. Because haptic feedback is a new technology and proved to be efficient, to apply it to the mobile phone camera feedback should provide better support for users when compared to the existing feedback signals, which are audio and visual only. One of the main objectives was to analyze the users’ needs and expectations regarding the mobile phone camera haptic feedback and applications in various types of difficult situations and challenges users have encountered. Therefore, a user study was done at the beginning of the thesis work. Its aim was to get general results, which can be applied to haptic interaction on the mobile phone camera in order to improve existing applications and help easing users in their photo taking activities with their mobile phone camera. In addition, the results are considered to provide input for further studies as well as to offer concrete input to the development of a prototype