A New Geometric Subproblem to Extend Solvability of Inverse Kinematics Based on Screw Theory for 6R Robot Manipulators

Geometric inverse kinematics procedures that divide the whole problem into several subproblems with known solutions, and make use of screw motion operators have been developed in the past for 6R robot manipulators. These geometric procedures are widely used because the solutions of the subproblems are geometrically meaningful and numerically stable. Nonetheless, the existing subproblems limit the types of 6R robot structural configurations for which the inverse kinematics can be solved. This work presents the solution of a novel geometric subproblem that solves the joint angles of a general anthropomorphic arm. Using this new subproblem, an inverse kinematics procedure is derived which is applicable to a wider range of 6R robot manipulators. The inverse kinematics of a closed curve were carried out, in both simulations and experiments, to validate computational cost and realizability of the proposed approach. Multiple 6R robot manipulators with different structural configurations were used to validate the generality of the method. The results are compared with those of other methods in the screw theory framework. The obtained results show that our approach is the most general and the most efficient.

     

Applying TRIZ and AHP to develop innovative design for automated assembly systems

Innovative design in the development of new product and process has become the core value in most business establishments. These innovative designs are often associated with the long-established trade-off compromises or conflicting performance parameters where speed and reliability or quality and cost are readily acknowledged. The rate of change in technology and the commercial environment suggests that the opportunity for innovative design is accelerating and systematic support for innovation process is needed. This study combines the Russian theory of inventive problem solving (TRIZ) and the analytical hierarchy process (AHP) for designing the automated manufacturing systems. This study applied the contradiction matrix table, 40 innovative principles, and 39 engineering parameters to compromise the trade-off between design contradictions and engineering parameters. The design engineers can acquire more feasible solutions and inspiration through the proposed approach. However, due to vagueness and uncertainty in the decision maker’s judgment, an AHP is employed as a decision support tool that can adequately represent qualitative and subjective assessments under the multiple criteria decision making environment. Moreover, the proposed approach can help decision makers facilitate the selection and evaluation of innovative designs in the presence of intangible attributes and uncertainty. In short, the objectives of this research are to use TRIZ to propose the automated design alternatives under the innovative design consideration and to use an AHP to evaluate and select the best feasible alternative under multiple criteria. A case study of designing automated connector assembly line has been used to demonstrate the applicability of the proposed approach.     

A hierarchical multiple-model approach for detection and isolation of robotic actuator faults

Modern robotic systems perform elaborate tasks in complicated environments and have close interactions with humans. Therefore fault detection and isolation (FDI) schemes must be carefully designed and implemented on robotic systems in order to guarantee safe and reliable operations. In this paper, we propose a hierarchical multiple-model FDI (HMM-FDI) scheme to detect and isolate actuator faults of robot manipulators. The proposed algorithm performs FDI in stages and refines the associated model set at each stage. Consequently only a small number of models are required to detect and isolate various types of unexpected actuator faults, including abrupt faults, incipient faults, and simultaneous faults. In addition, the computational load is alleviated due to the reduced-sized model set. The relation between the fault detection stage of the HMM-FDI scheme and the likelihood ratio test is explicitly revealed and theoretical upper bounds of the false alarm and missed detection probabilities are evaluated. Then we conduct experiments to demonstrate the ability of the HMM-FDI scheme in successful and immediate detection and isolation of actuator faults.