Kinetostatic Modeling of a Cable-Driven Parallel Robot Using a Tilt-Roll Wrist

Abstract

This paper introduces the concept of a new Cable-Driven Parallel Robot (CDPR) applicable for tasks requiring large rotation and translation workspaces, e.g., camera orienting devices, visual surveillance over vast areas and tomography scanners. The manipulator consists of a fixed frame and a tilt-roll wrist attached to a Moving-Platform (MP). The MP is an under-constrained and articulated mechanism connected to the fixed frame with six cables. The power is transmitted directly from the motors fixed on the frames to the tilt-roll wrist through cable loops. While most of the CDPRs only provide a limited range of rotation of the MP, the proposed manipulator is applicable for a relatively large and singularity-free rotation workspace thanks to its articulated MP.

A Deployable Cable-Driven Parallel Robot With Large Rotational Capabilities for Laser-Scanning Applications

“…Thanks to the inclinometer feedback, the pins are elongated/retracted so as to align the z-axis with the earth gravity direction before any robot operation. On the 4th level, the self-deployable EE is composed of a main brass body (14), which is referenced in its home configuration to the frame (15) by 3 spikes, an optical-grade mirror (16 -Edmund Optics λ/20 enhanced aluminium mirror) and 3 petals (17), which can rotate with respect to the main body about radial bearings (18). In order to minimize frictional effects, cables (19 -Daiwa Saltiga 12 braids, 0.55mm diameter) have a special silicon cover that ensures high roundness of their cross-section and low friction coefficient.…”

“…In order to minimize frictional effects, cables (19 -Daiwa Saltiga 12 braids, 0.55mm diameter) have a special silicon cover that ensures high roundness of their cross-section and low friction coefficient. They exit the tefloncovered routing tube (20) from proximal eyelets (21) and are attached in pairs inside a distal eyelet (22) onto each petal.The weight ratio between the platform components (14,16,17,18) and the total amount of cable installed in the machine (12 m) is greater than 10 2 , thus allowing cable to be assumed massless. When the main body is constrained by the frame, the petals can be closed by coiling the cables: this operation is performed when homing the machine before scanning (see the attached media).…”

“…On the other hand, common CDPR designs usually ensure a large translational workspace, while the orientation capability of the EE is limited by the necessity to avoid cable collisions [12], or to prevent cables from becoming slack [13]. New CDPR designs that allow for a larger orientation workspace are emerging in recent years, with their key features being articulated end-effectors [14]- [16], reconfigurable bases [17] or additional constraining mechanisms [18].…”

A Cable-Driven Parallel Robot With an Embedded Tilt-Roll Wrist

“…The last two rows of W correspond to the static model of the tilt-roll wrist presented in kinetostatic model of the tilt-roll wrist of [11]. t is the vector containing the tensions exerted by the eight actuators to the cables.…”

“…The other application of cable-loops is the actuation of embedded end-effectors on the moving-platforms (hybrid mechanisms) through cableloops and drums, so that no motor is required to be mounted on the moving-platform. In [10,11], two concepts of hybrid CD-PRs were detailed. In [10], a hoist was combined with a CDPR, with granted large rotation amplitudes of the hoist for adjusting height of a payload.…”