The OmniTread OT-4 serpentine robot—design and performance

Serpentine robots are slender, multi-segmented vehicles designed to provide greater mobility than conventional mobile robots. Serpentine robots are ideally suited for urban search and rescue, military intelligence gathering, and inspection tasks in hazardous or inaccessible environments. One such serpentine robot, developed at the University of Michigan, is the “OmniTread OT-4.” The OT-4 comprises seven segments, which are linked to each other by six joints. The OT-4 can climb over obstacles that are much higher than the robot itself, propel itself inside pipes of different diameters, and traverse difficult terrain, such as rocks or the rubble of a collapsed structure. The foremost and unique design characteristic of the OT-4 is the use of pneumatic bellows to actuate the joints. The pneumatic bellows allow the simultaneous control of position and stiffness for each joint. Controllable stiffness is important in serpentine robots, which require stiff joints to cross gaps and compliant joints to conform to rough terrain for effective propulsion. Another unique feature of the OmniTread design is the coverage of all four sides of each segment with drive tracks. This design makes the robot indifferent to rollovers, which are bound to happen when the slender bodies of serpentine robots travel over rugged terrain. This paper describes the OmniTread concept and some of its technical features in some detail. In the Experiment Results Section, photographs of successful obstacle traverses illustrate the abilities of the OT-4. © 2007 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56171/1/20196_ftp.pd

An optimization approach for the inverse kinematics of a highly redundant robot

This paper describes a robot with 12 degrees of freedom for pick-and-place operations using bricks. In addition, an optimization approach is proposed, which determines the state of each joint (that establishes the pose for the robot) based on the target position while minimizing the effort of the servomotors avoiding the inverse kinematics problem, which is a hard task for a 12 DOF robot manipulator. Therefore, it is a multi-objective optimization problem that will be solved using two optimization methods: the Stretched Simulated Annealing method and the NSGA II method. The experiments conducted in a simulation environment prove that the proposed approach is able to determine a solution for the inverse kinematics problem. A real robot formed by several servomotors and a gripper is also presented in this research for validating the solutions.info:eu-repo/semantics/publishedVersio

Octopus-Inspired Grasp-Synergies for Continuum Manipulators

Human operation of continuum “continuous-backbone” manipulators remains difficult, because of both the complex kinematics of these manipulators and the need to coordinate their many degrees of freedom. We present a novel synergy-based approach for operator interfaces, by introducing a series of octopus-arm inspired grasp-synergies. These grasp-synergies automatically coordinate the degrees of freedom of the continuum manipulator, allowing an operator to perform kinematically complex grasping motions through simple and intuitive joystick inputs. This effectively reduces the complexity of operation and allows the operator to devote more of his attention to higher-level concerns (e.g. goal, environment). We demonstrate the grasp-synergies interface design in both simulation and hardware using the nine degree of freedom Octarm continuum manipulator

Development and Optimisation of 3D Printed Compliant Joint Mechanisms for Hypermobile Robots

Hypermobile robots are an area of robotics that are often used as exploratory robots, but have facets that feature in other areas of the field. Hypermobile robots are robots that feature multiple body segments or modules, with joints between each. These robots are often used for exploratory purposes due to being able to maintain contact with the ground due to their flexible bodies. Wormbot was a hypermobile robot developed at the University of Leeds, which used a locomotion gait based on that of a Caenorhabditis elegans nematode worm, otherwise known as C.elegans. This movement pattern is reliant on compliance; a mechanism where the joints are slightly sprung and comply to the environment. The next iteration of Wormbot needs to be reduced in size, which would also require a new actuation and compliance system. This thesis describes the process of investigating a method of compliance to be used in the next version of Wormbot, while utilising the multi-material 3D printing capabilities available at the University. 3D printing provides quick manufacturing, allowing for fast changes to made to prototype components if required. During the process of this research, two 3D printed compliant actuation systems were produced; a pneumatic bellow and a Series Elastic Element (SEE) to be used in tandem with a servo motor. Both methods were tested to analyse their performance. The bellow was produced to utilise the capabilities of multi-material printing to strengthening suspected weak areas of the actuator. However, the performance of the bellow was unsatisfactory, failing twice in two actuation tests tests due to the device breaking. The SEE on the other hand, designed with two stiffer plates and a rubber-like spring element in the middle, initially proved to be reliable and repeatable in performance, with potential to behave linearly to a set spring constant. These results were acquired by performing rotational step response tests and fitting a spring-damper model to the results. However, issues with the plastic material were discovered when it was found to deform much more than anticipated, behaving in a similar manner to an additional spring element, complicating the model. Simulation work to explore the potential for using different spring constants of joint compliance in varying environments was also explored. This involved testing a virtual Wormbot in a range of environments while altering joint compliance. These simulations revealed that softer joints allow for favourable performance in constricting environments, while stiffer joints lend themselves more to quicker movement

Space-Capable Long and Thin Continuum Robotic Cable

Design of continuum robots, i.e. robots with continuous backbones, has been an active area of research in robotics for minimally invasive surgery, search and rescue, object manipulation, etc. Along the same lines, NASA developed Tendril , the first long and thin continuum robot of its kind, intended for in-space inspection applications. The thesis starts with describing and discussing the key disadvantages of the current state of the art mechanical design of Tendril\u27\u27 producing undesirable effects during operation. It then includes the design specifics of a novel concept for construction of a next generation long and thin, space-cable, multi-section, continuum cable-like robot, with a modified mechanical design for better performance. The new design possesses key features including controllable bending along its entire length, local compression and a compact actuation package. This new design is detailed in two versions. The first is a planar variant (suited for a 2D workspace), explaining the principle which allows the cable robot to achieve the above mentioned features. It is followed by a refined spatial version (suited for 3D workspace), where the functional characteristics are achieved within the desired aspect ratio of thin (less than 1 cm diameter) and relatively longer length (more than 100 cm) of the robotic cable. A new forward kinematic model is then developed extending the established models for constant-curvature continuum robots, to account for the new design feature of controllable compression (in the hardware) and is validated by performing experiments with the robot in (2D) planar and (3D) spatial scenarios. This new model is found to be effective as a baseline to predict the performance of such a long and thin continuum cable\u27\u27 robot