A mobile vibro-robot for locomotion through pipelines

The subject of our work is the creation of different designs of mobile robots for the movement through pipelines and similar technical systems. Using the transversal vibrations of an elastic bristle body, allows us to develop a new crawling vibro-robot. The motion is mainly realized by anisotropic friction forces. For the design process, we use the well-known construction principle of combination of alternative systems. It enables the transfer of structural characteristics (i.e. its kinematics) from one object to another, leading to new desirable characteristics or optimisations of existing technical objects. An analytical model of the motion of the bristles is presented

Design, fabrication and mechanical optimization of multi-scale anisotropic feet for terrestrial locomotion

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 67-69).Multi-scale surface interaction methods have been studied to achieve optimal locomotion over surface features of differing length scales. It has been shown that anisotropy is a convenient way of transferring an undirected force to a preferred direction or movement. In this thesis, the fundamentals of friction were studied to achieve a better understanding of how to design multi-scaled robotic feet that use anisotropy for terrestrial locomotion. Static and kinetic friction coefficients were found for novel test geometries under varying load conditions. The test geometries were manufactured with materials of variable durometer and were tested using unconventional rheometry methodology. Test results were then compared to standard friction laws. As predicted, the effects of contact area were shown to have an effect on the friction forces experienced by the softer materials. The contact area effects were then modeled as Hertzian contacts for a given material. Verification of the area dependencies for the materials with adhesive effects was performed for the samples used in the friction tests. The samples were subjected to varying compressive force and images of the corresponding contact areas were obtained using an inverted microscope. The microscope images were then processed using MATLAB's image processing toolbox to find the actual contact area for the samples. The contact area results were shown to be in accordance with Herztian contact principles. The effects of varying surface roughness were also studied for a given anisotropic arrangement of bristles. The array of bristles was used to provide propulsion to a controllable robot called BristleBot. The untethered nature of the robot allowed for unhindered velocity and force measurements that were used to analyze the effects of surface roughness. The force input for the robot was provided by two vibration motors that created an excitation which was then translated to horizontal movement by the anisotropic formation of the bristles. It was found that the BristleBot was able to achieve optimal locomotion when roughness conditions were minimized. Results of the anisotropic friction and adhesion tests were used to improve footpad development for soft robotic platforms.by Jeffrey W. Morin.S.M

Toward a Distributed Actuation and Cognition Means for a Miniature Soft Robot

This thesis presents components of an on-going research project aimed towards developing a miniature soft robot for urban search and rescue (USAR). The three significant contributions of the thesis are verifying the water hammer actuation previous work, developing an estimator of water hammer impulse direction from hose shape, and creating the infrastructure for distributed cognitive networks. There are many technical issues in designing soft robots, in terms of perception, actuation, cognition, power, physical structure and so on. We are focusing on actuation and cognition issues in this thesis. We investigated water hammer actuation as an alternative system which provides a continuously distributed form of actuation results from water hammer effect. It is special because it is a soft actuation method. We generated some comparison experiments and verified the benefits of the water hammer actuation, and also designed our soft robot to be hose-like in order to utilize the water hammer actuator. For the cognition part, we first addressed and verified that the shape of the hose-like robot has impact on impulse direction from the water hammer actuation. And then we implemented an emulated synthetic neural network (ESNN) to analyze the direction of the impulse from the water hammer actuation. Then in order to achieve the long-term goal, we distributed the emulated synthetic neural network onto many embedded system boards to achieve a distributed cognitive network. The distributed nodes in the network are using Bluetooth communication. In the comparison experiments between the active tether system and passive tether system, we can clearly see the benefits of active tether in momentum transfer and friction reduction. For example, in the drag test, with the water hammer actuation the burden that the tether can pull was increased by about 1.6 times. For the distributed cognitive network, we successfully built an emulated synthetic neural network on distributed embedded system boards. With the shape information as the inputs, the difference on outputs from the ESNN and the experimental results is less than 3%

Dynamics of a Vibration Driven Bristle Bot

Vibration driven robots utilize periodic forced vibration of an internal mass to achieve directed locomotion. Bristle bots are a class of vibration driven robots which are characterized by the presence of bristles or cilia on their surface and contain an internal mass that is driven to oscillate at a high frequency. Besides well-known applications in investigating swarming behaviour, such robots have potential applications in rescue operations in the rubble, inspections of pipes and other inaccessible confined areas and in medical devices where conventional means of locomotion is ineffective. Bristle bot or its commercially available variants such as hexbugs are popular toy robots. Despite the apparent simplicity of these robots, their dynamic behaviour is very complex. Vibration robots have attracted surprisingly few analytical models all which can only explain some regimes of locomotion. In this work, a wide range of motion dynamics of a bristlebot is explored using a mathematical model which accounts for the slip-stick motion of the bristles with the substrate. Analytical conditions for the system to exhibit a particular type of motion are formulated and the system of equations defining the motion are solved numerically using these conditions. The numerical simulations show transitions in the kinds of locomotion of a bristlebot as a function of the forcing frequency and amplitude. These different kinds of locomotion include stick-slip and pure slip motions along with the important phenomenon of the reversal of the direction of motion of the robot. In certain ranges of frequencies, the robot can lose contact with the ground and `jump\u27. These different regimes of locomotion are a result of the nonlinear vibrations of the robot and the friction between the robot\u27s bristles and the ground. The results of this work can potentially lead to more versatile vibration robots with predictable and controllable dynamics

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