In this work, we present the design and the implementation of an innovative knee locking mechanism for a dynamically walking robot. The mechanism consists of a fourbar linkage that realizes a mechanical singularity for locking the knee when the leg is in the extended position. Once extended, the knee remains locked without energy consumption, while unlocking it only costs a small amount of energy. Tests showed that the robot walks robustly and that the energy consumption of the new system is low.
A rail-guided robotic system is currently being designed for the inspection of ballast water tanks in ships. This robotic system will manipulate sensors toward the interior walls of the tank. In this paper, the influence of rail compliance on the end-effector position error due to ship movement is investigated.An analytical model of the six degrees-of-freedom (DOF) rail stiffness is presented and implemented in a reduced-order analytical frequency response model. This model describes the transfer function between ship acceleration and end-effector position as a function of rail geometry and material properties.Moreover, the influence of the robot compliance is investigated, resulting in design parameters for the robot. The models and calculations are evaluated and compared with a multibody model and prove to be accurate. The analytic models indicate whether or not a proposed robotic system is feasible and if so, optimize rail dimensions, material and robot design.A use-case scenario has been developed which shows that the proposed design will be unlikely to meet the requirements of this robot system design; therefore an alternative design strategy is recommended.978-1-4799-6934-0/14/$31.00 ©2014 IEEE
For special purpose robotic arms, such as a rail mounted ballast-water tank inspection arm, specific needs require special designs. Currently, there is no method to efficiently design robotic arms that can handle not quantifiable requirements. In this paper, an efficient method for the design and evaluation of the kinematics of manipulator arms on mobile platforms, with certain reach requirements within a limited space, is presented. First, the design space for kinematic arm structures is analyzed and narrowed down by a set of design rules. Second, key test locations in the workspace are determined and reduced based on, for example, relative positions and symmetry. Third, an algorithm is made to solve the inverse kinematics problem in an iterative way, using a virtual elastic wrench on the end effector to control the candidate structure toward its desired pose. The algorithm evaluates the remaining candidate manipulator structures for every required end-effector positions in the reduced set. This method strongly reduces the search space with respect to brute force methods and yields a design that is guaranteed to meet specifications. This method is applied to the use case of a rail-guided robot for ballast-water tank inspection. The resulting manipulator design has been built and the proof of concept has been successfully evaluated in a ballast-water tank replica.
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