Workspace Of Cable-driven Parallel Robots Research Articles

Data-Driven Dynamics Modeling and Control Strategy for a Planar n-DOF Cable-Driven Parallel Robot Driven by n + 1 Cables Allowing Collisions

Abstract Scholars have proposed to allow collisions of cables with the base, the end-effector, or obstacles to expand the workspace of cable-driven parallel robots (CDPRs) in recent years. However, allowing collisions also leads to new challenges in kinematics and dynamics modeling for CDPRs. To this end, this article focuses on a planar fully constrained n-degree-of-freedom (DOF) CDPR driven by n + 1 cables allowing collisions and develops a data-driven dynamics modeling strategy. The data-driven dynamics modeling strategy can address the collisions and optimal tension distribution issues simultaneously. Based on the data-driven dynamics modeling strategy, this article proposes a data-driven dynamics-based control strategy for the planar CDPR allowing collisions. A planar two-DOF CDPR prototype driven by three cables is established to evaluate the data-driven dynamics modeling strategy and data-driven dynamics-based control strategy.

Stiffness feasible workspace of cable-driven parallel robots with application to optimal design of a planar cable robot

In this paper stiffness of cable-driven parallel robots (CDPRs) is analyzed in detail and based on this analysis, the stiffness-feasible workspace is introduced. This workspace includes all stable poses which increasing the internal forces can modify the total stiffness of the robot. It has been shown that in the CDPRs, the concept of the internal forces can be applied for keeping cables in tension and increasing stiffness. However, it should be noted that increasing the internal forces may decrease the overall stiffness of the mechanism and it is only applicable in stabilizable poses of the workspace. Therefore, stiffness-feasible workspace determines the allowable internal forces range which can increase the stiffness and it will guarantee that in this range of the internal forces, the structure of the robot is stable. In this paper, by employing this criterion and evolutionary algorithms, a CDPR is optimally designed, and a set of answers is presented. In this design, in addition to the stiffness-feasible workspace, another criterion as stiffness number is presented which is useful for specifying the distribution of the stiffness and stiffness-feasibility of the robot.

Effect on wrench-feasible workspace of cable-driven parallel robots by adding springs

Cable-driven parallel robots (CDPRs) possess a number of promising advantages over conventional rigid-link robots, such as light weight, large payload handling capacity, considerably large workspace, and simpler dynamics. However, since cables can only pull but not push its attachment point on the end-effector, it is usually challenging for the wrench-feasible workspace (WFW) of CDPRs to meet the design requirements. Therefore, redundant cables or load on the end-effector is used to attain the required workspace. In this paper, springs are added between the end-effector and a base with the goal to modulate the workspace. The effects of different parameters of the spring on CDPR's wrenches are investigated and an optimization is proposed to determine the feasible spring parameters. Workspaces of two planar and spatial examples are presented. A reshaped workspace validation experiment was conducted. These results show that springs, with properly chosen parameters, can increase or reshape the WFW of CDPRs to meet the specified design requirements.