Advanced Strategies for Robot Manipulators

Amongst the robotic systems, robot manipulators have proven themselves to be of increasing importance and are widely adopted to substitute for human in repetitive and/or hazardous tasks. Modern manipulators are designed complicatedly and need to do more precise, crucial and critical tasks. So, the simple traditional control methods cannot be efficient, and advanced control strategies with considering special constraints are needed to establish. In spite of the fact that groundbreaking researches have been carried out in this realm until now, there are still many novel aspects which have to be explored

Low-Cost Technologies for Flexible Endoscopy: Design, Control and Autonomy for a Water-Jet Actuated Soft Continuum Endoscope

Despite the outstanding diagnostic performance brought by new technologies in medicine, cancer remains a significant burden worldwide. In addition to prevention strategies, the ability to detect malignancy early is crucial in enabling effective treatment and dramatically increasing the survival rate of patients. In the case of gastric cancer, diagnosis is generally performed using Flexible Endoscopy (or Endoscope) (FE). The FE has been proven to be a powerful, reliable and cost-effective tool in the fight against gastric cancer. However, its effectiveness strongly depends on the skills of trained Gastro Enterologists (GE) who perform the procedures. Moreover, accessibility and availability of such tools are often limited to people residing in major cities, while remote and rural areas remain poorly served by their health systems. The advent of robotics in medicine offers a new solution to these problems. When possible, automating diagnostic procedures or surgical tasks has the potential to deliver reliable, repeatable and cost-effective alternatives to standard human-in-the-loop procedures. Embedding autonomous capabilities into a machine, optimally designed to execute a specific task, could enable the device to automatically adapt to different conditions and non-skilled personnel to perform the procedure by supervising the actions of the robotic platform. In these scenarios, safety represents a major concern and in the majority of the cases, a safe interaction between the robot and the tissues can be guaranteed by building compliant robots made of soft materials. However, if the possibility of using compliant devices offers a number of advantages to the final user or patient, it defines a series of technical challenges that have to be addressed to deliver a stable and reliable control of the platform. Finally, by adopting low-cost designs, single-use solutions can be realised to address the issue and complication of sterilisation. This dissertation discusses the research effort targeted at the development of a water-jet actuated low-cost, disposable gastroscopy platform to offer a safe, cost-effective, fault-free alternative to standard FE

Control techniques for mechatronic assisted surgery

The treatment response for traumatic head injured patients can be improved by using an autonomous robotic system to perform basic, time-critical emergency neurosurgery, reducing costs and saving lives. In this thesis, a concept for a neurosurgical robotic system is proposed to perform three specific emergency neurosurgical procedures; they are the placement of an intracranial pressure monitor, external ventricular drainage, and the evacuation of chronic subdural haematoma. The control methods for this system are investigated following a curiosity led approach. Individual problems are interpreted in the widest sense and solutions posed that are general in nature. Three main contributions result from this approach: 1) a clinical evidence based review of surgical robotics and a methodology to assist in their evaluation, 2) a new controller for soft-grasping of objects, and 3) new propositions and theorems for chatter suppression sliding mode controllers. These contributions directly assist in the design of the control system of the neurosurgical robot and, more broadly, impact other areas outside the narrow con nes of the target application. A methodology for applied research in surgical robotics is proposed. The methodology sets out a hierarchy of criteria consisting of three tiers, with the most important being the bottom tier and the least being the top tier. It is argued that a robotic system must adhere to these criteria in order to achieve acceptability. Recent commercial systems are reviewed against these criteria, and are found to conform up to at least the bottom and intermediate tiers. However, the lack of conformity to the criteria in the top tier, combined with the inability to conclusively prove increased clinical benefit, particularly symptomatic benefit, is shown to be hampering the potential of surgical robotics in gaining wide establishment. A control scheme for soft-grasping objects is presented. Grasping a soft or fragile object requires the use of minimum contact force to prevent damage or deformation. Without precise knowledge of object parameters, real-time feedback control must be used to regulate the contact force and prevent slip. Moreover, the controller must be designed to have good performance characteristics to rapidly modulate the fingertip contact force in response to a slip event. A fuzzy sliding mode controller combined with a disturbance observer is proposed for contact force control and slip prevention. The robustness of the controller is evaluated through both simulation and experiment. The control scheme was found to be effective and robust to parameter uncertainty. When tested on a real system, however, chattering phenomena, well known to sliding mode research, was induced by the unmodelled suboptimal components of the system (filtering, backlash, and time delays). This reduced the controller performance. The problem of chattering and potential solutions are explored. Real systems using sliding mode controllers, such as the control scheme for soft-grasping, have a tendency to chatter at high frequencies. This is caused by the sliding mode controller interacting with un-modelled parasitic dynamics at the actuator-input and sensor-output of the plant. As a result, new chatter-suppression sliding mode controllers have been developed, which introduce new parameters into the system. However, the effect any particular choice of parameters has on system performance is unclear, and this can make tuning the parameters to meet a set of performance criteria di cult. In this thesis, common chatter-suppression sliding mode control strategies are surveyed and simple design and estimation methods are proposed. The estimation methods predict convergence, chattering amplitude, settling time, and maximum output bounds (overshoot) using harmonic linearizations and invariant ellipsoid sets