Cable-Driven Parallel Robot with Reconfigurable End Effector Controlled with a Compliant Actuator

Abstract

Redundancy in cable-driven parallel robots provides additional degrees of freedom that can be used to achieve different objectives. In this robot, this degree of freedom is used to act on a reconfigurable end effector with one degree of freedom. A compliant actuator actuated by one motor exerts force on both bodies of the platform. Due to the high tension that appears in this cable in comparison with the rest of the cables, an elastic model was developed for solving the kinestostatic and wrench analysis. A linear sensor was used in one branch of this cable mechanism to provide the needed intermediate values. The position of one link of the platform was fixed in order to focus this analysis on the relationship between the cables and the platform’s internal movement. Position values of the reconfigurable end effector were calculated and measured as well as the tension at different regions of the compliant actuator. The theoretical values were compared with dynamic simulations and real prototype results.

Potential Energy Distribution of Redundant Cable-Driven Robot Applied to Compliant Grippers: Method and Computational Analysis

“…In this section, the mechanism proposed in Figure 1 is analyzed to control the movement of the gripper. This mechanism is based on the CDPR with compliant actuators shown in [7] and allows two different bodies of the same end-effector to move by taking advantage of the redundancy and elasticity of the cables. The application of the proposed method determines the range of movement of one or several grippers to identify whether it is possible to close it and to determine the size of object that the gripper can handle for certain positions and the wrench applied to the end-effector.…”

“…One of the main differences between a CDPR and a usual parallel robot [5] is the flexibility and elasticity of the cables [6]. This characteristic is used to control reconfigurable end-effectors with compliant actuators, as seen in [7], where the actuation of a single cable exerts an influence on two different bodies. The scope of this article is to use energy analysis to simplify the resolution of this problem and apply it to the movement of two grippers attached to two cables.…”

“…This energy analysis allows the range of movement of those cables that exert their actuation on more than one body of the end-effector to be known. In Figure 1, a compliant actuator is proposed based on the previous developments shown in [7]. This mechanism takes advantage of the system redundancy to move a gripper attached to the main body.…”

“…The imposed values of tension in redundant cables could be used to set softer variations in the torque of the motor or for modifying the stiffness of the links if they have nonlinear springs. If the linear deformation is imposed, it can be used for controlling reconfigurable end-effectors, like in [7].…”

Rotational Workspace Expansion of a Planar CDPR with a Circular End-Effector Mechanism Allowing Passive Reconfiguration

“…In Reference [17], the orientation workspace was increased by mobilizing the support bases of the cables in the robot configuration. Rodriguez-Barroso et al [18] adapted the robot's workspace to different tasks by reconfiguring the EE. Duan et al [19] incorporated springs in the robot's structure and analyzed their effects on the workspace.…”