Design and control of constrained robotic systems for enhanced dexterity and mobility

Abstract

With continued developments in the field of robotics, there has been considerable research on manipulation, mobility, and control. Research in these areas has led to the development of sophisticated mechanisms and systems with enhanced capabilities. While innovations in actuator and sensor technology has significantly contributed towards meeting new challenges, the design problems have become increasingly complex due to greater number of constraints imposed by limitations in space, weight, power, and computational capability. Innovative design and control is often the key to successful implementation of these systems and the subject of this dissertation. Presented herein is the design of three separate systems, each with its own unique challenges in dexterity, mobility, and control. Specifically, we present the design of a dexterous mechanism for minimally invasive surgery, a miniature climbing robot for reconnaissance operation, and the control of a spherical robot which offers to provide maximum mobility and stability. A surgical instrument was designed for minimally invasive surgery with optimized load capacity and dexterity. The instrument fits through a standard 10 mm port and is optimized for bi-directional 180° articulation and unlimited rotation of a pair of forceps at the tip of the instrument. The state-of-the-art in surgical instrumentation does not have similar capabilities. A miniature climbing-robot for inspection and reconnaissance in urban environments is also developed. Similar to the surgical instrument design, which is constrained by space limitations, the climbing-robot design is constrained by weight, size, and power usage. A biped kinematic structure was chosen for the climbing-robot for its inherent advantages. This kinematic structure allows the robot to traverse horizontal and vertical surfaces, and transition between surfaces of different inclination. Similar to the climbing-robot, the spherical robot is intended for reconnaissance missions, but its control problem is more challenging due to the presence of nonholonomic constraints. A unique coordinate system is defined on the sphere for the purpose of control—this results in simple linear and curvilinear motion on the plane for independent control action. These motions are exploited to design trajectories between initial and final configurations of the sphere described by the two Cartesian coordinates of its point of contact and three orientation coordinates. The solution of these trajectories are straightforward and require minimal computation. Among the three problems considered, experimental work was done with the climbing-robot. The robot was designed, built, and tested under computer control.