Modern lightweight robotic systems require a systematic, multidisciplinary approach to design. Bond graphs provide a general paradigm that can be used in design of such complex systems. Modelling of slender manipulator links that typically undergo large translational and rotational motion is not simple. There are several approaches that are developed. In this paper slender robotic links are modelled as collection of finite element beams based on co-rotational formulation. Model of complete robotic system is developed using multi-level bond graph models. Resulting mathematical model is generated in form of a system of differential-algebraic equations (DAEs). One advantage of use of bond graphs is that model formulation is based on velocities (unlike the other that typically use position formulation) and that leads to index 2 semi-explicit DAEs, which can be readily solved with available technique. BondSim, an integrated object-oriented modelling and simulation environment, is used. The method is applied to two flexible multi-link problems and simulation results show that developed models provide excellent numerical performances. The proposed method can be successfully used for modelling other mechatronics systems as well.

Bond Graph Based Modelling and Simulation of Flexible Robotic Manipulators

The aim of this article is to investigate the characteristics of a composite fibre advanced materials used as a robotic link manipulator for replacement of rigid one. The composite material is combination of two and more fibre processed and bonded with epoxy, resulting hybrid form of material component with required properties which are to be analyzed for suitability with respect to its function, reliability, durability, safety and cost-effectiveness. The composites generally have high-strength, high-stiffness (graphite, kevlar, etc.) low-density (epoxy, polyvinyl) strong and stiff with lightweight. In this investigation, five different composite structural fibres are taken as a flexible link with joint flexibility for case study analysis. The rotating structural fibre link, loaded and tested different types of joint stiffness coefficients (kc). The numerical evaluations are conducted for structural fibre material for replacement rigid manipulator. The modeling of structural fibre single flexible link on the basis of Euler-Bernoulli beam theory and Lagrange’s equations of motion is studied and accurate modes of the system are obtained.

Advanced Structural Fibre Material for Single Link Robotic Manipulator Simulation Analysis with Flexibility

In the precise control of robot, the robot joint friction has periodic ripple errors when the LuGre friction model is used for joint torque calculations. An improved LuGre friction model is proposed for this problem, including the steady-state friction force represented by the LuGre friction model, and the velocity-dependent position-dependent term. The friction model is identified in steps, and the steady-state friction parameters are identified using the features of the LuGre friction model, and the position-dependent terms in the model are identified by SVM multiclass classification method, SVR and least squares method to solve the system of equations. The results of the experimental study show that the error can be reduced by more than 50% when using the improved model and the identification method to calculate the joint friction moments. 

Research on joint friction identification of robot based on SVR

In the precise control of robot, the robot joint friction has periodic ripple errors when the LuGre friction model is used for joint torque calculations. An improved LuGre friction model is proposed for this problem, including the steady-state friction force represented by the LuGre friction model, and the velocity-dependent position-dependent term. The friction model is identified in steps, and the steady-state friction parameters are identified using the features of the LuGre friction model, and the position-dependent terms in the model are identified by SVM multiclass classification method, SVR and least squares method to solve the system of equations. The results of the experimental study show that the error can be reduced by more than 50% when using the improved model and the identification method to calculate the joint friction moments.

In this work, a systematic approach is presented for the development of dynamic equations of motion of a robot manipulator with mechanical flexibility. A simple structural lightweight rotating manipulator with joint elastic flexibility is considered for the mechanical flexibility study. The complexity of mathematical equations involved in mechanical flexibility is analyzed. The analytical approach helps the design for controls of flexible manipulator. A set of decoupled dynamic equations are derived incorporating both the structural and joint flexibility. The dynamic equations are compared with a detailed model, and the results are showing that equations are accurate for small joints. Also the results from the simulation show that in a flexible joint system, there is no rigid mode.

Numerical Analysis of Robotic Manipulator Subject to Mechanical Flexibility by Lagrangian Method

In this research, a model of a robotic manipulator flexible structure and an equation of motion for controller design is planned. The structural material for the robot structure is chosen as a hybrid composite for this investigation along with a comparison study is carried out for the aluminium 6082 alloy of flexible manipulator arm application. To analyses, the vibration behavior and control implementation by adding joint flexibility in the system is organized. Using simulation algorithm, system parameter calculation is carried out through MATLAB software for vibration amplitude, transient period, steady-state error, and settling time of flexible robotic arm system. In a systematized way of motion equation, flexible robotic deflections are organized via the assumed mode (AM) and Lagrange techniques (LT). The graph analysis of hybrid composite and AL6082 materials with high stiffness coefficients is plotted. These obtained values from the plot are utilized for Linear Quadratic Regulator (LQR) controller design. The LQR output facts for both aluminium structural robotic arm and composite material robotic arms are established.

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Ramalingam Sengalani

Papers

Numerical Analysis of Robotic Manipulator Subject to Mechanical Flexibility by Lagrangian Method

Vibration Control Using Modern Control System for Hybrid Composite Flexible Robot Manipulator Arm