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Compliant Modular Robot for climbing obstacles, stairs and Multi-Agent System applicationsAuthor: Sri Harsha Turlapati Turlapati Date: 2017-07-19 Report no: IIIT/TH/2017/66 Advisor:Madhava Krishna AbstractUneven terrain navigation and Urban Search and Rescue (USAR) Robots have been in demand in the past decade. Though tracks and legs have better traversing ability on an uneven terrain, they are still slower than wheeled robots with the same actuator system. Hence there is an added advantage for articulated wheeled robots for stair climbing. Stair Climbing is also a key functionality desired for robots deployed in USAR scenarios. Additionally, for USAR operations, a design that is capable of navigating rough terrain as well as crammed spaces is very beneficial. Keeping all these points in mind, a prototype is proposed consisting of three modules connected with each other through passive joints. It is propelled using an active pair of wheels per module. Since there are no actuators at the joints, the joints are not susceptible to losing operability while traversing on rugged terrain. However with the absence of actuators, we face the issue of the robot toppling over when an abnormally large obstacle is encountered. This shortcoming is overcome with the use of compliant joints. The compliant joints are designed by employing springs of optimal stiffness, which is calculated through an optimization formulation aided with the constraints presented by the static analysis of the robot. With this overall design considerations, variants of the design capable of carrying out various tasks is presented. This work presents the design process of the compliant modular robot (CMR) that is suitable for steep step descent, stair climbing and finally a reconfigurable multi agent system. An additional spring pair to help in the steep step descent was initially proposed and the analysis needed for its design was carried out. Experimental validation corroborated the prototype's performance. In the stair climbing conception of the CMR, necessary quasi static analyses were carried out and appropriate compliance was deployed at the joints of the CMR. The main contribution here was to use the Locus method to enumerate the phases through which the robot goes while climbing stairs. Following this, quasi static analysis was performed on each phase to determine the optimal stiffness of the compliant springs deployed at the joints. Numerical Simulations were carried out and experimental results were shown with an in-house fabricated prototype. Trials were run on various types of staircases to validate robustness of the prototype. Post this, the stair climbing compliant modular robot was improved to tackle overhang on stairs. A Multi Objective Optimization formulation was solved using Taguchi Grey Analysis and a multi-parameter based design was determined as a result that could climb stairs with overhang. Each module pushing the preceding module as the robot climbs its way across uneven terrain was one of the novelties of this project. Leveraging this modularity further, the Detachable Compliant Modular Robot (DCMR) was conceived. This is special in the sense of combining the two fields of Multi Agent Systems and Uneven Terrain Navigation. The idea is to be able to have multiple modules (capable of individual actions and exploration) collaborate to climb stairs and other uneven terrain. A spring is designed and used in the modular robot taking the worst-case-scenario of stairs encountered in an urban setting. In addition to the actuators at the wheels, an additional set of actuators per module are introduced to enable the detachment and re-attachment. The design additions and their trade-offs are discussed. Potential applications are presented with special focus on improving coverage of a map with obstacles/slabs large enough to merit exploration by climbing them. The problem of turning in crammed spaces is solved using the ability to detach of DCMR. The detaching & re-attaching capability, and stair climbing of the composite modular robot are demonstrated through experimentation using the prototype. Full thesis: pdf More details Centre for Robotics |
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