Robin Chhabra

Concurrent synthesis of robot manipulators using Hardware-in-the-loop Simulation

This paper discusses a practical approach to the concurrent synthesis of robot manipulators, which is based on the alternative design methodology of Linguistic Mechatronics (LM) as well as the utilization of a modular Robotic Hardware-in-the-loop Simulation (RHILS) platform. The RHILS platform involves physical joint modules and the control unit to reduce modeling complexities while taking into account various physical phenomena. The LM methodology simplifies the multi-objective constrained optimization problem into a single-objective unconstrained formulation and also brings subjective notions of design into the scope. The new approach is applied to redesigning kinematic, dynamic and control parameters of an industrial manipulator.

A holistic approach to concurrent engineering and its application to robotics

This article details a holistic concurrent design framework, based on fuzzy logic, which is suitable for multidisciplinary systems. The methodology attempts to enhance communication and collaboration between different disciplines through introducing the universal notion of satisfaction and expressing the holistic behavior of multidisciplinary systems using the notion of energy. Throughout the design process, it uses fuzzy logic to formalize subjective aspects of design including the impact of the designer’s attitude, resulting in the simplification of the multi-objective constrained optimization process. In the final phase, the methodology adjusts the designer’s subjective attitude based on a holistic system performance by utilizing an energy-based model of multidisciplinary systems. The efficiency of the resulting design framework is illustrated by improving the design of a 5-degree-of-freedom industrial robot manipulator.

Concurrent Engineering of Robot Manipulators

Robot manipulators are good examples of complex engineering systems, where designers occasionally employ a subsystem-partitioning approach for their analysis and synthesis. The design methodology is traditionally based on the sequential decomposition of mechanical, electromechanical, and control/instrumentation subsystems, so that at each step a subset of design variables is considered separately (Castano et al., 2002). Although conventional decoupled or loosely-coupled approaches of design seem intuitively practical, they undermine the interconnection between various subsystems that may indeed play a crucial role in multidisciplinary systems. The necessity of communication and collaboration between the subsystems implies that such systems ought to be synthesized concurrently. In the concurrent design process, design knowledge is accumulated from all the participating disciplines, and they are offered equal opportunities to contribute to each state of design in parallel. The synergy resulting from integrating different disciplines in concurrent design has been documented in several case studies, to the effect that the outcome is a new and previously unattainable set of performance characteristics (Hewit, 1996). However, the challenge in a concurrent design process is that the multidisciplinary system model can become prohibitively complicated; hence computationally demanding. Plus, a large number of multidisciplinary objective and constraint functions must be taken into account, simultaneously, with a great number of design variables. As the complexity of the system model increases, in terms of the interactions between various subsystems, the coordination of all the constraints distributed in different disciplines becomes more difficult, in order to maintain the consistency between performance specifications and design variables. Within the context of robotics, several ad hoc techniques of concurrent engineering have been reported in the literature. They are innovative design schemes for specific systems, such as Metamorphic Robotic System (Chirikjian, 1994), Molecule (Rus & McGray, 1998), Miniaturised Self-Reconfigurable System (Yoshida et al., 1999), Crystalline (Rus & Vona, 2000), and Semi-Cylindrical Reconfigurable Robot (Murata et al., 2000). But, more systematic approaches have been suggested by other researchers beyond the robotics community to tackle the challenge of high dimensionality in concurrent design. These approaches can be divided into two major groups. The first group translates the model complexity into a large volume of computations, and then attempts to find efficient algorithms or parallel 12

Dynamical reduction and output-tracking control of the Lunar Exploration Light Rover (LELR)

This paper presents the dynamical reduction and feedback linearization of the Lunar Exploration Light Rover to design an output-tracking torque controller for such a system. The rover is dynamically modeled as a system of rigid bodies that could be considered as a symmetric mechanical system. Its dynamical equations are reduced using the Chaplygin reduction of nonholonomic systems. The reduced dynamical system only involves the rotation and steering angles of the port front wheel. The steering angle and the travelled distance of the vehicle are considered the outputs of the resulting control system. Feedback linearization in the reduced phase space is then employed to derive a proportional-integral-derivative feedback, feedforward torque controller for the rover. Finally, a series of simulation studies are provided to show the robustness of the resulting controller under uncertainties of the dynamical parameters and the disturbance force in the form of friction at the rear wheels.

Elastica as a dynamical system

Abstract The elastica is a curve in R 3 that is stationary under variations of the integral of the square of the curvature. Elastica is viewed as a dynamical system that arises from the second order calculus of variations, and its quantization is discussed.

Reduction of Hamiltonian Mechanical Systems with Affine Constraints: A Geometric Unification

This paper presents a geometrical approach to the dynamical reduction of a class of constrained mechanical systems. The mechanical systems considered are with affine nonholonomic constraints plus a ...

A linguistic approach to concurrent design

This paper outlines a concurrent design methodology for multidisciplinary systems, which employs tools of fuzzy theory for the tradeoff in the design space. This methodology enhances communication between designers from various disciplines through introducing the universal notion of satisfaction and expressing the behaviour of multidisciplinary systems using the notion of energy. It employs fuzzy rule-bases, membership functions and parametric connectives in fuzzy logic to formalize subjective aspects of design, resulting in a two-phase simplification of the multi-objective constrained optimization of a design process. The methodology attempts to find a pareto-optimal solution for the design problem. In the primary phase of the methodology, a fuzzy-logic model is utilized to identify a region in the design space that contains the pareto-optimal design state, and a proper initial state is suggested for the optimization in the secondary phase, where the pareto-optimal solution is found. Finally, the impact of the designers subjective attitude on the design is adjusted based on a system performance by utilizing an energy-based model of multidisciplinary systems. As an application, it is shown that the design of a five-degree-of-freedom industrial robot manipulator can be enhanced by using the methodology.