Yogesh Singh

Robust nonlinear PID-like fuzzy logic control of a planar parallel (2PRP-PPR) manipulator.

In this paper, a robust nonlinear proportional-integral-derivative (PID)-like fuzzy control scheme is presented and applied to complex trajectory tracking control of a 2PRP-PPR (P-prismatic, R-revolute) planar parallel manipulator (motion platform) with three degrees-of-freedom (DOF) in the presence of parameter uncertainties and external disturbances. The proposed control law consists of mainly two parts: first part uses a feed forward term to enhance the control activity and estimated perturbed term to compensate for the unknown effects namely external disturbances and unmodeled dynamics, and the second part uses a PID-like fuzzy logic control as a feedback portion to enhance the overall closed-loop stability of the system. Experimental results are presented to show the effectiveness of the proposed control scheme.

Performance investigations on optimum mechanical design aspects of planar parallel manipulators

Abstract This paper presents a comparative analysis of three degrees of freedom planar parallel robotic manipulators (x, y and θz motion platforms) namely 2PRP-PPR, 2PRR-PPR, 3PPR (Hybrid), 3PRP (Hephaist) and 3PPR U-base in terms of optimal kinematic design performance, static structural stiffness and dynamic performance (energy and power consumption). Kinematic and dynamic performance analyses of these platforms have been done using multibody dynamics software (namely ADAMS/View). Static stiffness of the above-mentioned manipulators have been analysed, compared using the conventional joint space Jacobian stiffness matrix method, and this method has been verified through a standard finite-element software (namely NASTRAN) as well. The size of the fixed base or aspect ratio (width/height) can be varied for various working conditions to understand its design parameters and optimal design aspects which are depending on the fixed base structure. Different aspect ratios (fixed base size) are considered for the comparative analyses of isotropy, manipulability and stiffness for the above-mentioned planar parallel manipulators. From the numerical simulation results, it is observed that the 2PRP-PPR manipulator is associated with a few favourable optimum design aspects such as singularity-free workspace, better manipulability, isotropy, higher stiffness and better dynamic performance in terms of power and energy requirement as compared to other planar parallel manipulators.

Task space position tracking control of an autonomous underwater vehicle with four tilting thrusters

Underwater vehicles are usually designed with additional degrees of freedom than those required to accomplish given manipulator tasks. A robot platform should be effective to maintain its position and orientation in order to attain diverse underwater tasks. This study addresses the dynamic modeling of an autonomous underwater vehicle (AUV) which consists of tilting thrusters for hovering motion to oppose reaction force of the manipulator and ocean current. The suggested system consists of four tilting thrusters with six degrees-of-freedom (DOF). The tilting movements of the thrusters make the system unstable due to complex coupling. A robust position tracking controller is designed based on redundancy resolution scheme has been posited. The trajectory tracking potentiality of the manipulator has been analyzed. The numerical results of the proposed redundancy resolution scheme indicate that this approach shows a significantly revamped outcome when compared with the conventional counterpart.

Development of a Planar 3PRP Parallel Manipulator using Shape Memory Alloy Spring based Actuators

This paper presents the development of a SMA (shape memory alloy) spring actuation based 3-dof (three degree of freedom) 3PRP (prismatic-rotary-prismatic) planar parallel manipulator where each limb (3 stands for three limbs) of the manipulator having PRP joint arrangement. The active prismatic actuators are made of SMA springs. This 3PRP planar parallel manipulator has a parallel structure including a fixed base and a moving platform (end-effector) and placed in xy plane. Base and the end-effector of the manipulator are linked together by three limbs consisting of prismatic-revolute-prismatic (PRP) joint arrangement in which each limb has one active prismatic joint made of SMA springs. Forward and inverse kinematic analysis of the 3PRP planar parallel manipulator has been studied. Suitability and usage of SMA spring based actuators replacing highly bulky prismatic actuators has been investigated. In addition, the detailed study of the actuation or deflection of the SMA springs in the application of driving the manipulator has been presented experimentally. From the experimental results, it is observed that the 3PRP manipulator associated with SMA spring based actuators has larger workspace to total area required ratio as all the three active prismatic actuators actuates properly and in same time. In overall, this paper shows the 3PRP planar parallel manipulator associated with SMA spring actuators is superior alternatives to conventional motion stages for high precise micro-positioning and tracking applications.

A robust task space position tracking control of an underwater vehicle manipulator system

This paper addresses a robust tracking control of an autonomous underwater vehicle-manipulator system (UVMS) based on terminal sling mode control in task space along with a disturbance observer. The effectiveness of the proposed scheme is demonstrated using numerical simulations having a serial planar manipulator (two rotary joints) on an underwater vehicle in a horizontal plane. An inverse dynamic solution for the system is obtained using the Newton-Euler method incorporating hydrodynamic and dynamic coupling effects. Performance of the proposed scheme is compared under various control schemes and demonstrated numerically for a predefined trajectory of the end effector (in task space).

Comparative kinematic and dynamic performance analysis of planar parallel manipulators

This paper addresses a comparative analysis of a three degree of freedom (DOF) planar parallel manipulators (x, y and ϕ) namely 3RRR, 3PRP, 3PRR, 3PPR Δ base, 3PPR U base and 2PRP-PPR in terms of optimal kinematic design performance and dynamic performance. Kinematic and dynamic performance analyses of these six different configurations have been done using MATLAB and Adams/View software. From the simulation results, it is observed that the 2PRP-PPR planar parallel manipulator is associated with a few favorable optimum design aspects namely singularity free workspace, isotropy and better dynamic performance in terms of energy requirement as compare to other planar parallel manipulators discussed here.

Robust disturbance observer based sliding mode control of a planar parallel (3-PPR) manipulator

This study proposes a robust controller in conjunction with the dynamic modeling of an existing three degrees of freedom planar parallel manipulator which can perform effectually in the presence of parameter uncertainties and external disturbances. The planar manipulator discussed here has three legs each with a prismatic-prismatic-revolute (3-PPR) joint configuration and located on the same plane connecting the moving platform which is in the form of an equilateral triangle. Each leg consists of an active prismatic joint, a passive prismatic joint and a passive rotary joint. The dynamic model has been obtained using the Euler-Lagrangian formulation method which is based on the kinetic and potential energies of the system. The proposed controller is based on a sliding mode control scheme with a nonlinear disturbance observer incorporated which aids in eliminating disturbances present in the system which is a result of both disturbances (internal and external disturbances) and parameter uncertainties which might arise due to un-modeled dynamics. Computer based numerical simulations are performed to demonstrate the effectiveness of the proposed control and results confirming the same in the presence of disturbances.