Pushparaj Mani Pathak

Impedance Control of Space Robots Using Passive Degrees of Freedom in Controller Domain

Impedance control is an efficient and stable method of providing trajectory and force control in robotic systems. The procedure by which the impedance of the manipulator is changed is a very important aspect in the design of impedance based control schemes. In this work, a scheme is presented in which the control of impedance at the interface of the end effector and the space structure is achieved by introduction of a passive degree of freedom (DOF) in the controller of the robotic system. The impedance is shown to depend upon a compensation gain for the dynamics of the passive DOF. To illustrate the methodology, an example of a two DOF planer space robot is considered.

A scheme for robust trajectory control of space robots

Abstract This paper presents a scheme for robust trajectory control of free-floating space robots. The idea is based on the overwhelming robust trajectory control of a ground robot on a flexible foundation and robust foundation disturbance compensation presented elsewhere. No external jets/thrusters are required or used in the scheme. An example of a three-link robot mounted on a free-floating space platform is considered for demonstrating the efficacy of the control scheme. Bond graph technique has been used for the purpose of modeling and simulation. Robustness of the control scheme is guaranteed since the controller does not require the knowledge of the manipulator parameters.

Trajectory control of a two DOF rigid-flexible space robot by a virtual space vehicle

Model based control schemes use inverse dynamics of the robot arm to produce the main torque component necessary for trajectory tracking. For a model-based controller one is required to know the model parameters accurately. This is a very difficult job especially if the manipulator is flexible. This paper presents a control scheme for trajectory control of the tip of a two arm rigid-flexible space robot, with the help of a virtual space vehicle. The flexible link is modeled as an Euler-Bernoulli beam. The developed controller uses the inertial parameters of the base of the space robot only. Bond graph modeling is used to model the dynamics of the system and to devise the control strategy. The efficacy of the controller is shown through simulated and animation results.

Kinematic Calibration of a Multisection Bionic Manipulator

This paper deals with the forward kinematic calibration of a bionic arm inspired from the organic elephant trunk and called compact bionic handling assistant (CBHA). First, a forward kinematic model is developed based on the principle of the constant curvature continuum robot theory. Then, two experimental setups are proposed in order to carry out the model calibration and validation. The first one is based on the trilateration method, while the second one is based on the coupling of the CBHA with a rigid six-degree-of-freedom rigid manipulator. The aim of the calibration is to enhance the precision of the forward kinematic model.

Impedance Control of Space Robot

Abstract The force control of a space robot is a difficult task, as the interaction of robot tip with the environment causes the base to change its position and orientation. Impedance control is an efficient method for trajectory and force control in a robotic system. The procedure by which the impedance of the manipulator is changed is a very important aspect in the design of impedance-based control schemes. This paper presents a scheme in which the control of impedance at the end-effector environment interface is achieved by introduction of a passive degree of freedom (DOF) in the robotic system in the controller. The impedance depends upon a gain compensation for the dynamics of the passive DOF.

Validation of finite element modelling through photoelastic fringe contours

In finite element modelling, apart from proper element selection, selection of an appropriate discretization scheme is crucial in correctly evaluating the intended variables. The role of photoelasticity in selecting an appropriate discretization scheme for modelling problems in stress analysis is presented in this paper.

Reconfiguration of Directional Handling of an Autonomous Vehicle

This article concerns reconfiguration of an autonomous vehicle, called RobuCar, with four independently driven wheels and two independently adjustable steering angles. A bond graph model of the system is constructed for generating the Analytical Redundancy Relations (ARRs) which are evaluated with actual measurements to generate residuals and to perform structural fault isolation. Once the fault list is updated in the equipment availability database, an automaton selects the next best option to reconfigure the system such that the given control objectives are achieved. The developed methodology is validated by considering two different fault scenarios.

Attitude Control of a Free-Flying Space Robot using a Novel Torque Generation Device

In this paper we present a new torque generation device that can be used to control the attitude of space robots. The device is based on the principle of continuously variable transmission. A detailed analytical study of the device has been performed, and the behavior and stability of the overall system have been studied. Bond graph modeling has been used to conceive the device. The advantage of using this device is that many control strategies are possible for the control of a space vehicle.

Modelling of multisection bionic manipulator: Application to RobotinoXT

This paper deals with geometric models of a class of multisection bionic manipulator applied to RobotinoXT. This bio-inspired flexible manipulator is a small version of a multisection pneumatically actuated, called Bionic Handling Assistant robot (BHA), where each segment is composed by a set of backbones tubes. Experimental results are presented to compare the analytical and practical analysis. These models are the first steps to synthesis of kinematic and dynamic model of this class of bionic manipulator, which will be used to design an adequate control for the whole robot.

Control oriented model-based simulation and experimental studies on a compliant legged quadruped robot

Quadruped robots offer better maneuverability over wheeled mobile robots. However, a quadruped robot contains many joint actuators which have to operate in a coordinated fashion to achieve the desired locomotion. Joint actuations cause various degrees of disturbance on the robot body and may even destabilize the system. Thus, prior dynamic analysis plays an important role for development of control laws for quadruped locomotion. Here, a three dimensional dynamic model of a quadruped has been developed using the bond graph technique which can be interfaced with various controller models. This model contains a detailed sub-model for telescopic compliant legs. Results from simulations, animations and experiments are discussed. Turning motion at various leg speeds is studied for dynamic stability of the robot. The effect of leg compliance on locomotion parameters is studied which helps in selecting a suitable compliance. Performance measure is carried out using energy efficiency as deciding criteria. Study on energy efficient quadruped structure, energy efficient locomotion gait and foot trajectory have been carried out for designing an efficient quadruped. Paper presents three dimensional dynamic model of quadruped with compliant legs.Model is verified with simulation, animation and experiment results.Turning motion is demonstrated by providing differential leg tip velocity.Influence of leg compliance on quadruped locomotion is studied.Energy efficient structure, gait and foot trajectory have been carried out.