Papers by R Prasanth Kumar
Discrete time-delay control of an autonomous underwater vehicle: Theory and experimental results
A discrete time-delay control (DTDC) law for a general six degrees of freedom unsymmetric autonom... more A discrete time-delay control (DTDC) law for a general six degrees of freedom unsymmetric autonomous underwater vehicle (AUV) is presented. Hydrodynamic parameters like added mass coefficients and drag coefficients, which are generally uncertain, are not required by the controller. This control law cancels the uncertainties in the AUV dynamics by direct estimation of the uncertainties using time-delay estimation technique.
The simplest passive dynamic walking model with toed feet: A parametric study
SUMMARY This paper presents a passive dynamic walking model with toed feet that can walk down a g... more SUMMARY This paper presents a passive dynamic walking model with toed feet that can walk down a gentle slope under the action of gravity alone. The model is the simplest of its kind with a point mass at the hip and two rigid legs each hinged at the hip on the one end and equipped with toed foot on the other end. We investigate two cases of the model, one with massless legs and another with infinitesimal leg masses.
Improved stability in lower extremity exoskeletons using foot extensions
Abstract Existing lower extremity exoskeletons lack sufficient foot support area to guarantee saf... more Abstract Existing lower extremity exoskeletons lack sufficient foot support area to guarantee safe operation for rehabilitation of patients, and normal posture/gait for users carrying heavy loads on backpack. In order to enhance the stability of lower extremity exoskeletons, an adaptive foot system is presented. It consists of two foot extensions, one extending behind the toe and another on the heel side that extends the support area behind the heel when the foot is flat and retracts when the heel is off the ground.
Simplest dynamic walking model with toed feet
Abstract This paper presents a dynamic walking model with toed feet that can walk down a gentle s... more Abstract This paper presents a dynamic walking model with toed feet that can walk down a gentle slope under the action of gravity alone. The model is the simplest of its kind with a point mass at the hip and two rigid legs each hinged at the hip on one end and equipped with toed foot at the other end. We investigate two cases of the model, one with massless legs and another with infinitesimal leg masses.
Journal of Mechanical Science and Technology, Jan 1, 2009
A virtual maintenance system in a virtual environment can be used to simulate a real-world mainte... more A virtual maintenance system in a virtual environment can be used to simulate a real-world maintenance system. The efficiency of the simulation depends mainly on the assembly/disassembly task sequence. During simulation, path planning of mechanical parts becomes an important factor since it affects the overall efficiency of the maintenance system in terms of saving energy and time. Therefore, planners must consider the path-planning factors under constraints such as obstacles and the initial/final positions of the parts, as well as the assembly sequence such as number of gripper exchanges and direction changes. We propose a novel optimal assembly algorithm that considers the assembly sequence of mechanical parts and the pathplanning factors for a virtual maintenance simulation system. The genetic algorithm is used to determine the optimal sequence of parts to minimize the numbers of gripper exchanges and direction changes, as well as find a repulsive force radius using the potential field method to generate the shortest optimal distance for transferring each part during the assembly operation. By applying the proposed algorithm to a virtual maintenance system, users can be haptically guided to the optimized assembly solution during mechanical parts assembly operations.
… Modelling Practice and …, Jan 1, 2008
Ocean Engineering, Jan 1, 2005
This paper deals with real-time optimal motion planning for astable AUVs, and presents an approxi... more This paper deals with real-time optimal motion planning for astable AUVs, and presents an approximate analytical solution for the optimal control problem of a symmetric astable AUV with symmetric thruster configuration. The results show that the motion along the target vector is optimal for such underwater vehicles. The numerical solutions are found to be in good agreement with the approximate analytical solution. A relationship between the number of thrusters and the energy consumed is derived analytically for forward motion. The effect of the number of thrusters on optimality is shown to be significant at higher speeds. In the case of omni-directional underwater vehicles, the number of thrusters plays major role in optimal motion planning. For monostable underwater vehicles, the approximate analytical solution can be used as a good starting point for numerical solution. q
Ocean Engineering, Jan 1, 2007
A new control scheme for robust trajectory control based on direct estimation of system dynamics ... more A new control scheme for robust trajectory control based on direct estimation of system dynamics is proposed for underwater vehicles. The proposed controller can work satisfactorily under heavy uncertainty that is commonly encountered in the case of underwater vehicle control. The dynamics of the plant are approximately canceled through the feedback of delayed accelerations and control inputs. Knowledge of the bounds on uncertain terms is not required. It is shown that only the rigid body inertia matrix is sufficient to design the controller. The control law is conceptually simple and computationally easy to implement. The effectiveness of the controller is demonstrated through simulations and implementation issues are discussed. r
A New Tracking Controller Design for Underwater Vehicles Using Quadratic Stabilization
Journal of Dynamic Systems, …, Jan 1, 2008
Résumé/Abstract This paper proposes a new tracking controller for autonomous underwater vehicles ... more Résumé/Abstract This paper proposes a new tracking controller for autonomous underwater vehicles (AUVs) using the concept of simultaneous quadratic stabilization. The nonlinear underwater vehicle system is viewed as a set of locally linear time invariant systems obtained by linearizing the system equations on the reference trajectory about some discrete points. A single stabilizing controller is then designed for the set of systems so obtained. However, this controller requires the exact parameters of the system. Since the ...
Hybrid toe and heel joints for biped/humanoid robots for natural gait
Control, Automation and …
Abstract A biped/humanoid robot with toe and heel joints is capable of more natural locomotion du... more Abstract A biped/humanoid robot with toe and heel joints is capable of more natural locomotion due to the additional degrees of freedom available. Though passive spring loaded joints can help to some extent, they introduce constraints between the joint torque and the joint angular displacement. In this paper, we propose to use hybrid active/passive toe and heel joints in order to accommodate a wide range of step lengths and speeds as well as uneven terrain. The toe joints are spring loaded to minimize the maximum torque ...
A novel dynamic walker with heel, ankle, and toe rocker motions
Robotica
Robotica: page 1 of 11. © Cambridge University Press 2011 doi:10.1017/S0263574711000099 ... A nov... more Robotica: page 1 of 11. © Cambridge University Press 2011 doi:10.1017/S0263574711000099 ... A novel dynamic walker with heel, ankle, and toe rocker motions ... R. Prasanth Kumar, Abdullah¨Ozer, Gabsoon Kim ... School of Mechanical and Aerospace Engineering ...
An adaptive foot device for increased gait and postural stability in lower limb Orthoses and exoskeletons
… Journal of Control, Automation and Systems, Jan 1, 2011
Abstract Assistive devices and exoskeletons have critical importance for people with manipulative... more Abstract Assistive devices and exoskeletons have critical importance for people with manipulative and locomotive disabilities. One of the major purposes of such devices when used for lower extremities is to help provide the postural or gait stability of the user. However, current lower extremity exoskeletons available lack the sufficient foot support area to guarantee a safe operation for the rehabilitation of patients, and normal posture/gait for users carrying heavy loads on backpack. As a result, these devices may require an ...
Test-bed for Navigation and Control of a Thruster based AUV
Abstract A thruster controlled AUV is being developed for the Indian AUV project. All motions and... more Abstract A thruster controlled AUV is being developed for the Indian AUV project. All motions and control is carried out by a set of five thrusters for controlling positions in two attitudes and three linear directions. As a prototype and verification system for the above AUV, a test-bed to develop and validate the control schemes was found necessary and has been developed at IIT Kharagpur. This paper describes the design criteria of the test-bed and the methods used to develop control scheme for such class of underwater vehicles, which are ...
Robust Tracking Control of Underwater Vehicles using Time-Delay Control in Discrete-Time Domain
Abstract This paper discusses the application of time-delay control law for robust trajectory tra... more Abstract This paper discusses the application of time-delay control law for robust trajectory tracking control of underwater vehicles. The idea is based on the cancellation of uncertain dynamics in the plant by estimating a function which closely approximates the plant uncertainty at any given instant. This is done through the feedback of the derivative of the state and the previous control inputs. By deriving the controller in discrete-time the necessity of using state derivative is removed. The controller is computationally simple and easy to ...
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Papers by R Prasanth Kumar