Parvathi Sunilkumar

Bio: Parvathi Sunilkumar is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Parallel manipulator & Motion control. The author has an hindex of 1, co-authored 4 publications receiving 3 citations.

Dynamics and Motion Control of a Three Degree of Freedom 3-PRRR Parallel Manipulator

Abstract: This work focuses on the dynamic modelling and motion control scheme of a parallel manipulator which has three legs of prismatic-revolute-revolute-revolute joint setup. In each of the legs, the prismatic (P)-joint is active and the rotary (R)-joints are passive. The three legs further join into an end-effector in a right-angled triangle shape. The Euler-Lagrangian approach is followed to achieve the dynamics of the manipulator. The formulations are detailed and simulated. This paper also presents an augmented proportional-derivative (PD) controller along with gravity compensation for the motion control. This control method transforms the closed-loop dynamics of the manipulator into decoupled, and thus it becomes easier to quantify the motion performance. The trajectory tracking performance and its accompanying errors are also discussed.

Conceptual Design and Control of a Sitting-Type Lower-Limb Rehabilitation System Established on a Spatial 3-PRRR Parallel Manipulator

Abstract: The conceptual design of a new sitting-type lower-limb rehabilitation robot along with simplified motion control for its passive range of motion therapies is put forth here The suggested system’s design is demonstrated and verified using computer-based numerical simulations For this, the desired motion trajectory is generated with the help of a clinically obtained gait data-set The robustness of the proposed simplified motion control scheme is verified with the variation of the physical parameters of the patients’ limb

Graphical interactive user interface system for a stationary trainer to perform lower limb rehabilitation tasks

Abstract: The graphical interactive user interface system of a stationary trainer for performing lower-limb rehabilitation tasks is presented in this article. The stationary trainer considered here for the interactive system development is based on a foot-plate operating system. The foot-plate is an end-effector of a parallel Cartesian manipulator. The interactive system primarily designed for the therapeutic tasks associated with passive range of motion (PROM) of the lower limbs. Further, the interactive system concentrated on the hip and knee joint motion therapies which include flexion/extension of knee and hip as well as abduction/adduction of hip. Various clinically suggested motions along with their working nature are designed in the interactive user interface. The suggested interface would generate the system settings (the various system parameters to be fixed during the real-time training) are generated based on the patient’s physical parameters such as limb length, patient’s weight, height, etc. The interactive simulator of the stationary trainer is demonstrated and verified using computer-based numerical simulations.

Investigation of Interference-Free Workspace of a Cartesian (3-PRRR) Parallel Manipulator

Abstract: This work focuses on determining the link interference-free workspace of a Cartesian (3-PRRR) parallel manipulator. An algorithm for obtaining the largest volume cuboid that inscribes the interference-free workspace is proposed, which can be used as a performance index for the mechanism under investigation. The effect of link dimensions and the size of the moving platform on the interference-free workspace is also analysed in this work.

Design of mechanisms of a robotic system for rehabilitation of the lower limbs

Abstract: The article describes the main stages of developing a robotic system for the rehabilitation of the lower limbs based on the "tripteron" robot. The structure of a robotic system has been designed, consisting of a 3-PRRR parallel mechanism, which provides the angles of rotation of all joints of the patient's leg required for rehabilitation and a passive orthosis for supporting the limb. At the first stage, the positions of the active mechanism links are determined. The output link of only one kinematic chain, making a translational movement in the vertical direction, will experience a maximum load. A design diagram of this kinematic chain was built, and the reactions of the supports were determined at the second stage. At the third stage, kinematic dependences were obtained, and an engine was selected that would provide the required torque at the required speeds.

Numerical investigations, development and control of a cartesian (3-PRRR) parallel manipulator

Abstract: This paper focusses on the development of a Cartesian parallel manipulator (CPM) having multiple limb assembly configurations. An optimal configuration of the 3-PRRR CPM is identified after analysing the interference-free workspace of various limb assembly conditions, where each leg comprises an active prismatic joint followed by three revolute joints. The validation of the link interference detection algorithm is carried out using a virtual prototype. The Euler–Lagrange dynamic modelling of the CPM is validated using one of the well-known multi-body simulation packages namely, ADAMS. The paper proposes a detailed design and performance analyses of a motion controller for the proposed manipulator, based on a finite-time sliding mode scheme. A Graphical User Interface (GUI) is also developed using the MATLAB App Designer, which ensures easier and intuitive synthesis of the CPM. The development of an in-house functional prototype is also presented in this work.

Investigation of Interference-Free Workspace of a Cartesian (3-PRRR) Parallel Manipulator

Abstract: This work focuses on determining the link interference-free workspace of a Cartesian (3-PRRR) parallel manipulator. An algorithm for obtaining the largest volume cuboid that inscribes the interference-free workspace is proposed, which can be used as a performance index for the mechanism under investigation. The effect of link dimensions and the size of the moving platform on the interference-free workspace is also analysed in this work.

Robotic control system for lower limb rehabilitation with force feedback

Abstract: The paper proposes the structure of the robotic system (RS) control system with and without the patient’s force feedback, describes the conditions for using each of them. The method for improving data reliability on applied forces using strain gauge readings in the absence of patient activity was developed. The method of motivating a patient to perform “correct” movements thus “assisting” the mechanism, which consists in changing the speed of movement to create an impression that the mechanism moves due to patient’s efforts was developed. Mathematical RS model was constructed, graphs reflecting the accuracy of the specified trajectory were obtained.

A Graphical User Interface (GUI) System for a Stationary Trainer Used in Lower Limb Rehabilitation

Abstract: This paper presents a graphical user interface system for a lower limb rehabilitation robot. The mechanism considered for this application is a stationary trainer based on Cartesian parallel manipulator. The trainer is configured with three legs of PRRR (prismatic-revolute-revolute-revolute) configuration connected to the end-effector. The end-effector of the mechanism is a footplate to which the subject’s foot can be attached for therapeutic procedures. The interactive simulator is designed primarily for carrying out the therapeutic procedures of PROM (passive range of motion) of the lower limb. Specifically, the application developed can demonstrate the mechanism motion for hip abduction–adduction, hip flexion–extension, knee flexion–extension and gait training. In addition to these options, the simulator also enables the user to vary the subject parameters like thigh and crus lengths. The proposed interactive simulator design is demonstrated and verified using computer-based numerical simulations.