Vassilis C. Moulianitis

A knowledge-based system for the conceptual design of grippers for handling fabrics

The paper presents a knowledge-based system (KBS) for the conceptual design of grippers for handling fabrics. Its main purpose is the integration of the domain knowledge in a single system for the systematic design of this type of grippers. The knowledge presented, in terms of gripper, material and handling process, are classified. The reasoning strategy is based upon a combination of a depth-first search method and a heuristic method. The heuristic search method finds a final solution from a given set of feasible solutions and can synthesize new solutions to accomplish the required specifications. Details of the main features of the system are given, including its ability to take critical design decisions according to four criteria, weighted by the designer. The knowledge-based system was implemented in the Kappa P. C. 2.3.2 environment. Two examples are given to illustrate some critical aspects concerning the KBS development, to explain the operation of the proposed searching heuristic method, and to show its effectiveness in producing design concepts for grippers.

Kinematic Synthesis of Structures for Metamorphic Serial Manipulators

In this work a method for the kinematic synthesis of structure topologies for modular metamorphic serial manipulators is presented. A detailed description of this class of robot manipulators is presented, in order to clarify their basic elements and their basic structural definitions. Based on these, the Metamorphic Structure Representation (MSR) is proposed for the systematic representation of this type of metamorphic manipulator structures. A thorough examination of the possible metamorphic links that can be constructed is presented and used for the definition of the manipulator’s structure evaluation criteria, to formulate a multi criteria evaluation index. The problem of the optimal kinematic synthesis of metamorphic structures is formulated and the process of automated generation of structures according to the specified requirements is presented. The results are presented in detail, in order to reflect their validity and the advantages that the proposed process for the kinematic synthesis of topologies for the modular metamorphic manipulator provides to the designer.

Multi-objective optimization with fuzzy measures and its application to flow-shop scheduling

Most of the research in multi-objective scheduling optimization uses the classical weighted arithmetic mean operator to aggregate the various optimization criteria. However, there are scheduling problems where criteria are considered interact and thus a different operator should be adopted. This paper is devoted to the search of Pareto-optimal solutions in a tri-criterion flow-shop scheduling problem (FSSP) considering the interactions among the objectives. A new hybrid meta-heuristic is proposed to solve the problem which combines a genetic algorithm (GA) for solutions evolution and a reduced variable neighborhood search (RVNS) technique for fast solution improvement. To deal with the interactions among the three criteria the discrete Choquet integral method is adopted as a means to aggregate the criteria in the fitness function of each individual solution. Experimental comparisons (over public available FSSP test instances) with five existing multi-objective evolutionary algorithms (including the well known SPEA2 and NSGAII algorithms as well as the recently published L-NSGA algorithm) showed a superior performance for the developed approach in terms of diversity and domination of solutions.

A dimensional tolerancing knowledge management system using Nested Ripple Down Rules (NRDR)

This paper proposes to use a knowledge acquisition (KA) approach based on Nested Ripple Down Rules (NRDR) to assist in mechanical design focusing on dimensional tolerancing. A knowledge approach to incrementally model expert design processes is implemented. The knowledge is acquired in the context of its use, which substantially supports the KA process. The knowledge is captured which human designers utilize in order to specify dimensional tolerances on shafts and mating holes in order to meet desired classes of fit as set by relevant engineering standards in order to demonstrate the presented approach. The developed dimensional tolerancing knowledge management system would help mechanical designers become more effective in the time-consuming tolerancing process of their designs in the future.

Manipulator performance constraints in Cartesian admittance control for human-robot cooperation

This paper addresses the problem of providing feedback to the operator about the manipulators performance during human-robot physical interaction. A method is proposed that implements virtual constraints in Cartesian admittance control in order to prevent the operator from guiding the manipulator to low-performance configurations. The constraints are forces expressed in the Cartesian frame, which restrict the translation of the end-effector when the operator guides the robot below a certain performance threshold. These forces are calculated online by numerically approximating the gradient of the performance index with respect to the Cartesian frame attached to the end-effector. An experimental evaluation is conducted involving human-robot interaction with a 7-DOF LWR serial manipulator under Cartesian admittance control, using the kinematic manipulability index of the manipulator as the performance measure for singularity avoidance.

Design and fuzzy control of a robotic gripper for efficient strawberry harvesting

Strawberry is a very delicate fruit that requires special treatment during harvesting. A hierarchical control scheme is proposed based on a fuzzy controller for the force regulation of the gripper and proper grasping criteria, that can detect misplaced strawberries on the gripper or uneven distribution of forces. The design of the gripper and the controller are based on conducted experiments to measure the maximum gripping force and the required detachment force under a variety of detachment techniques. It is demonstrated that the hand motion for detaching the fruit from the stem has a significant role in the process because it can reduce the required force. By analysing those results a robotic gripper with pressure profile sensors is developed that demonstrates an efficiency comparable to the human hand for strawberry grasping. The designed gripper and fuzzy controller performance is tested with a considerable number of fresh fruits to demonstrate the effectiveness to the uncertainties of strawberry grasping.

A fuzzy approximation to dexterity measures of mobile manipulators

In this paper, a fuzzy system is trained to approximate the manipulability index and the inverted condition number of a mobile manipulator. The kinematic model of a mobile platform with the attached manipulator is fused using twist theory and certain dexterity measures are examined throughout the configuration space. A Takagi–Sugeno–Kang fuzzy system is designed to approximate the dexterity measures and it is evaluated both for its error and its efficiency in computational cost. The proposed methodology is proved as a very efficient approximation that can be utilized in real-time motion planning algorithms without significantly adding computational cost to the controller.

An innovative virtual-engineering system for supporting integrated footwear design

This paper presents a new virtual-engineering platform, called as virtual shoe test bed (VSTB), for supporting the design of footwear from the engineering point of view. The proposed VSTB system includes various functional design criteria in order to support the definition of the best solution for each product utilising scenarios based on user needs and preferences. Using the proposed virtual-engineering system a designer is able to simulate the behaviour of footwear components and the interaction between shoe and user in order to derive a predictive estimation of the fitting, thermal comfort and performance ratings without the necessity to manufacture and validate physical prototypes. The present paper describes the architecture, the tests implemented in the final system along with corresponding lab experiments conducted in terms of industrial validation. All results and hints for future research are reported and discussed.

Metamorphic Structure Representation: Designing and Evaluating Anatomies of Metamorphic Manipulators

In this work the metamorphic structure representation (MSR) is proposed for the systematic development and evaluation of structures of metamorphic serial manipulators. The basic elements of MSR are presented, in terms of module and connection type. The conceptual design of metamorphic structures using MSR is presented. The criteria for evaluating emerging structures are introduced in terms of simplicity and solvability of inverse kinematics. Finally, a case study of two different structures is presented along with their subsequent evaluation.

A closed-loop drop-foot correction system with gait event detection from the contralateral lower limb using fuzzy logic

In the present paper a closed loop fuzzy control scheme for the correction of the drop-foot syndrome is presented. The control scheme is based on EMG signals from the contralateral, unimpaired lower limb and its efficiency is tested by the application of the controller to a simulated bipedal locomotion with one lower limb suffering from the Drop-Foot Syndrome. Two are the major characteristics of the controller: identification of the phase where the stimulation must be provided using EMG signals from the contralateral, unimpaired lower limb and correction of the excitation signal according to the phase using EMG signals from the collateral impaired lower limb.