This work presents a trajectory planning strategy for a dual-arm planar space robot in workspace that is intended to minimize vehicle attitude disturbance that may occur due to dynamic coupling between the arms and the vehicle of the space robot. The strategy is based on the principle of dynamic coupling between the tip motion and the vehicle motion of the space robot. The strategy uses the two arms of manipulator. One arm, called the mission arm, achieves the trajectory control task while the other arm, called the balance arm, moves in such a way as to reduce the attitude of the vehicle. A robust overwhelming controller is used for trajectory control of the tip of the mission arm. The balance arm first-joint rotation is based on the mission arm first-joint rotation, whereas the balance arm second-joint rotation is carried out such that a small attitude disturbance of the vehicle takes place. An example of the two degrees of freedom planar space robot is considered to illustrate the methodology. A bond graph has been adopted as the modeling tool, as it facilitates the system modeling from the physical paradigm itself and it is easy to develop various control strategies by modifying the physical paradigm.
Natural fiber composite materials are gradually becoming more popular due to light weight, low cost, bio degradability, easy to manufacture, lower environmental impact and less energy requirement for manufacturing. These properties of natural fiber make it suitable for automobile, aerospace and other industrial applications. In present study, analysis of mechanical properties like tensile strength, flexural strength, impact strength and Young's modulus are carried out for various composites. Free vibration characteristics of natural fiber composite beams are also studied analysed. In addition to analytical study, finite element analysis also carried out using ANSYS. In this, the test specimens were modelled in accordance to experimental test specimen and model analysis is performed.
This work presents the design of virtual foundation through which impedance control is achieved in a dual arm space robot for cooperative manipulation of arms. A docking operation by the two arms of the space robot has been carried out. During this docking operation, the space robot has a mechanical interaction with the compliant objects which encounter force and motion constraints. The docking operation requires that the object must be gripped and follows a specific path to dock the selected object. By use of the virtual foundation, impedance control is achieved to fulfill both objectives, i.e. force control during gripping and trajectory control during docking. The space robot base compensation is designed to achieve the desired trajectory to control the interaction forces. The methodology has been validated with simulated results.
To safely hold an unidentified object by means of an intelligent hand of robot, the hand has to recognize the weight of it. By attaching six-axis Force/Torque (F/T or Force/Moment) sensor to an intelligent robot's hand the weight can be calculated by measuring forces F x , F y and F z . Forces should be measured in order to precisely pull and push an object. To securely grasp an unidentified object with an intelligent robot's gripper, the forces in the gripping direction and in the gravitational direction needs to be detected, but it also requires to perceive the moments to accurately recognize the position of the object in the grippers. A robot joint can be controlled in better way if three forces and three moments exerted at the joint are measured. The available Force/Torque sensors are bulky, not customized and costly. Therefore, it is essential to customize and develop low cost six axis Force/Torque sensor with new appropriate dimensions for an intelligent robot's joints. Six axis Force/Torque sensor is designed using strain gauge. The strain gauges are selected for Aluminium and its working conditions. The sensor design is based on results of parametric analysis done in ANSYS software to obtain the strain values in the measurable range. The analytical results are compared with Finite Element Analysis (ANSYS) results. The percentage error in deviation is 0.75% maximum.
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