Kinematic Stability based AFG-RRT Path Planning for Cable-Driven Parallel Robots

Abstract

Motion planning for Cable-Driven Parallel Robots (CDPRs) is a challenging task due to various restrictions on cable tensions, collisions and obstacle avoidance. The presented work aims at proposing an optimal path planning strategy in order to both maximize the wrench capability and the dexterity of the robot in a cluttered environment. First, an asymptoticallyoptimal path finding method based on a variant of rapidly exploring random trees (RRT) is implemented along with the GilbertJohnsonKeerthi (GJK) algorithm to account for the collision detections. Then, a goal biased Artificial Field Guide (AFG) is employed to reduce convergence time and ensure directional exploration. Finally, a post-processing algorithm is added to get a short and smooth resultant path by fitting appropriate splines. The proposed path planning strategy is analyzed and demonstrated on a simulated and experimental setup of a six-DOF spatial CDPR.

Polytope-based Continuous Scalar Performance Measure with Analytical Gradient for Effective Robot Manipulation

“…The key characteristic property of this proposed methodology, is that the sigmoid activation is conservative. Regardless of the input value in (19), the output is always bounded between 0 and 1. The characteristic "S" shape curve behaviour of the sigmoid function ensures that the function is smooth, continuous and does not have any sharp spikes or discontinuities.…”

“…Guay et al [16] introduced the Capacity margin (CM), a polytope based minimum degree of constraint satisfaction index, that quantifies the robustness of equilibrium of an object using a single scalar function. This kinetostatic index is applied to Cable-Driven Parallel Robots (CDPR), to determine Wrench Feasible Workspace (WFW) [16], [17], [18] with bounded forces/tensions, for path planning [19], designing optimal cable winches [20] for Aerial Cable Towed System (ACTS), reconfiguration planning [21], and subsequently for their dimensional [22] synthesis. Similar to wrench analysis, the CM also provides a good estimate of the available acceleration set for motion generation [23].…”

“…Prior work has utilized CM [19] [21], as cost functions with only heuristic based planners, which can have good, but not guaranteed convergence. The index in its original form is based on a discontinuous min function which renders it inconvenient for many optimization algorithms.…”

A collaborative path planning method for mobile cable-driven parallel robots in a constrained environment with considering kinematic stability

“…Bak et al [19] proposed a modified goal-biased RRT method to obtain the feasible path for CDPR in a cluttered environment. More recently, Mishra et al [20] generated the optimal path for CDPRs by deploying the combination of the artificial field guide (AFG) method and RRT*. However, the aforementioned studies were restricted to CDPR.…”

Human-cable collision detection with a cable-driven parallel robot

“…Another method using Rapidly exploring Random Trees (RRT) considering both internal and external collisions was proposed in [21]. This was expanded with an AFT-RRT* algorithm simulated in a cluttered environment to obtain near optimal point-to-point motion in [22]. In the context of collaborative robotics, a method introducing a repulsive force in the admittance control, preventing two cables to fold onto one another [23].…”