Mohan Santhakumar

Task Space Control of an Autonomous Underwater Vehicle Manipulator System by Robust Single-Input Fuzzy Logic Control Scheme

In this paper, a robust single-input fuzzy logic control Robust Single Input Fuzzy Logic Controller (RSIFLC) scheme is proposed and applied for task-space trajectory control of an autonomous underwater vehicle manipulator system (AUVMS) employed for underwater manipulation tasks. The effectiveness of the proposed control scheme is numerically demonstrated on a planar underwater vehicle manipulator system [consisting of an underwater vehicle and a two link rotary (2R) serial planar manipulator]. The actuator and sensor dynamics of the system are also incorporated in the dynamical model of an AUVMS. The proposed control law consists of a feedforward term to exaggerate the control activity with immoderation from the known desired acceleration vector and an estimated perturbed term to compensate for the unknown effects namely external disturbances and unmodeled dynamics as a first part and a single-input fuzzy logic control as a feedback portion to enhance the overall closed-loop stability of the system as a second part. The primary objective of the proposed control scheme is to track the given end-effector task space trajectory despite of external disturbances, system uncertainties, and internal noises associated with the AUVMS. To show the efficacy of the proposed control scheme, comparison is made with conventional fuzzy logic control (CFLC), sliding mode control (SMC), and proportional–integral–derivative (PID) controllers. Simulation results confirmed that with the proposed control scheme, the AUVMS can successfully track the given desired spatial trajectory and gives better and robust control performance.

Investigation into the dynamics and control of an underwater vehicle-manipulator system

This study addresses the detailed modeling and simulation of the dynamic coupling between an underwater vehicle and manipulator system. The dynamic coupling effects due to damping, restoring, and inertial effects of an underwater manipulator mounted on an autonomous underwater vehicle (AUV) are analyzed by considering the actuator and sensor characteristics. A model reference control (MRC) scheme is proposed for the underwater vehicle-manipulator system (UVMS). The effectiveness of the proposed control scheme is demonstrated using numerical simulations along with comparative study between conventional proportionalintegral-derivative (PID) control. The robustness of the proposed control scheme is also illustrated in the presence of external disturbances and parameter uncertainties.

Dynamic Modelling Approaches for a 3-PPR Planar Parallel Manipulator

This paper proposes two dynamic modelling approaches for a planar parallel manipulator with a 3-PPR configuration. The planar configuration has three legs each with a Prismatic-Prismatic-Revolute [PPR] configuration where the first joint is actuated. These three legs are joined by an end-effector which is in the form of an equilateral triangle. The dynamics of the manipulator was derived using an energy based Euler-Lagrangian approach and the DeNOC (Decoupled Natural Orthogonal Complement) matrices. Both the formulations are elucidated and the resulting formulation are compared under similar conditions to validate them.

A nonregressor nonlinear disturbance observer-based adaptive control scheme for an underwater manipulator

A new nonlinear disturbance observer-based tracking control scheme for an underwater manipulator is presented in this paper. This observer overcomes the disadvantages of existing disturbance observers, which are designed or analyzed by the linear system techniques. It can be applied in underwater manipulator systems for various purposes such as payload compensation, interaction effects compensation, underwater current or external disturbance compensation, and independent system control. The performance of the proposed tracking control scheme is demonstrated numerically by the payload compensation and interaction effects compensation for a two degrees of freedom vertical underwater manipulator.

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.

Robust nonlinear task space position tracking control of an autonomous underwater vehicle-manipulator system

This paper presents a robust nonlinear control scheme for task-space trajectory control for an autonomous underwater vehicle- manipulator system (AUVMS) based on an improved proportional integral derivative (PID) control scheme used for deep-sea intervention tasks. A planar underwater vehicle manipulator system (consists of an underwater vehicle and two link rotary (2R) serial planar manipulator) with dynamic coupling between them is considered for the study and numerical simulation. The actuator and sensor dynamics of the system are also considered. The proposed controller integrates the known approximated inverse dynamic model output as a model-base portion of the controller; uses a feed forward term to enhance the control activity with indulgence from known desired acceleration vector; carries an estimated perturbed term to compensate for the unknown effects namely external disturbances and un-modelled dynamics and a decoupled nonlinear PID controller as a feedback portion to enhance closed-loop stability and account for the estimation error of uncertainties. The primary objective of the proposed control scheme is to track the given end-effector task-space trajectory despite of external disturbances, system uncertainties and internal noises associated with the AUVMS system, which show the robustness of the proposed control scheme. Simulation results confirmed that the AUVMS can successfully track the given desired spatial trajectory.

A 4PRP Redundant Parallel Planar Manipulator for the Purpose of Lower Limb Rehabilitation

This paper proposes a kinematically redundant planar manipulator for lower limb rehabilitation application, having configuration 4PRP. The challenges in the existing mechanisms has been analyzed and a new configuration is proposed. This configuration helps to improve the effective workspace of the lower limb rehabilitation robot. The lower limb rehabilitation systems are used to treat the post stroke patients and limb injured patients by providing rigorous exercises through the motor nerves recovery. This paper shows the advantages of the proposed 4-PRP kinematically redundant planar manipulator over existing 2PRP-2PPR in providing higher effective workspace with same capability in performing lower limb rehabilitation tasks.

Development of an Amphibian Legged Robot Based on Jansen Mechanism for Exploration Tasks

The paper discusses the development of a linkage based amphibian legged robot for exploration and surveillance tasks. The proposed system can walk on both ground and water surfaces. The proposed system has two major mechanisms for its motion namely a planar eight bar Jansen mechanism as a leg and an Ackermann steering mechanism as for turning. The performance of the proposed mechanisms is verified in terms of motion, force (motion/walking) and structural aspects. The effectiveness and performance of the system is demonstrated by using an in-house fabricated prototype for different working conditions. The Jansen legged mechanism is redesigned in order to improve the drag force during walking on the water surface.

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.