WO2011012916A1

WO2011012916A1 - Payload suspension system with arrester unit

Info

Publication number: WO2011012916A1
Application number: PCT/HU2010/000085
Authority: WO
Inventors: Gábor STÉPÁN; Lászlό KOVÁCS; Richárd WOHLFART; Mihály JURÁK; Dániel BACHRATHY; András TÓTH
Original assignee: Budapesti Műszaki és Gazdaságtudományi Egyetem
Priority date: 2009-07-28
Filing date: 2010-07-27
Publication date: 2011-02-03
Also published as: EP2480479A1; EP2480479B1; HUP0900466A2; HU0900466D0

Abstract

A payload suspension system for facilitating three- dimensional movement of a suspended payload especially but not exclusively for aerial tethered/cable suspended robots, rescue systems and crane systems is provided. Keeping the main cables together by an arrester unit can increase the reachable area of a payload and therefore a larger place for positioning is available and less space is required for the suspending cables. A payload platform is suspended by main cables traversing through the arrester unit which keeps the main cables together. The arrester unit is connected to the payload platform by an anchoring cable.

Description

PAYLOAD SUSPENSION SYSTEM WITH ARRESTER UNIT

TECHNICAL FIELD

The invention relates to a payload suspension system for facilitating three-dimensional movement of a suspended payload especially but not exclusively for aerial

tethered/cable suspended robots, rescue systems and crane systems .

BACKGROUND OF THE INVENTION In US-5,585,707 a tendon suspended platform robot is provided comprising of a platform, tendons and a control system. The platform contains proximal reels for the storage, retraction and extension of the tendons, with each tendon having a reel. The distal ends of the tendons are anchored at separate locations. The work space of the robot is primarily determined by the location of the tendon anchors. The platform is translated and rotated in the work space by controlling the lengths of the tendons extending from their respective reels. A master computer located on the platform controls each reel and coordinates their actuation. When used with at least six tendons and reels, the platform has six degrees of freedom: translation in three axes and rotation about each of the foregoing three axes. Numerous types of end effectors can be mounted on the platform, thus enabling the robot to perform a wide variety of tasks. A tea serving robot suspended from ceiling is described in a publication of Takahashi, Y. Nakamura, M. Hirata, E. Dept . of Mech. Syst . Eng., Kanagawa Inst. Of Technol . ; (This paper appears in: Intelligent Robots and Systems, 1998. Proceedings., 1998 IEEE/RSJ International Conference on Publication Date: 13-17 Oct 1998 Volume: 2, On page(s): 1296-1301 vol.2. The duty of the tea serving robot is to serve a drink to a bedridden person. A bedridden person can order the robot to bring a cup of tea without hesitation, and therefore can avoid his dehydration. A hand of the robot is suspended from a ceiling, of a house, and driven three dimensionally in the orthogonal coordinates. No installing area is required to utilize the robot because of the

suspended structure from a ceiling. The hand swings as a pendulum.

As it is seen, the tendon suspended platforms or robots require a lot of place for the tendons above the platform which is a limitation of use in an in-house environment where the suspended robot needs to navigate around

furniture.

SUMMARY

The present invention involves a new system which solves the aforementioned problems, as well as other

problems that will become apparent from an understanding of the following description by providing system for

facilitating three-dimensional movement of a suspended payload. It is particularly an object of the invention to set up a system for facilitating three-dimensional movement of a suspended robot .

The invention is based on the recognition that keeping the main cables together by an arrester unit can increase the reachable area of a payload and therefore a larger place for positioning is available and less space is required for the suspending cables. Using the arrester unit also helps the cable forces keep low, in the worst case situation the largest cable force equal to the total dynamic load.

The payload platform is suspended by main cables traversing through the arrester unit which keeps the main cables together. The arrester unit is connected to the payload platform by an anchoring cable. In possible embodiments the arrester unit is connected to the payload platform by an anchoring cable actuated by a winding mechanism placed on the payload platform or on the arrester unit or on a suspension unit.

In further possible embodiments, the arrester unit forms a ring surrounding the main cables and anchoring the upper end of the anchoring cable at its circumference or constructed as a disk with apertures furnished with rollers.

The most important advantage of the invention is that it increases the reachable area of the payload platform which is highly beneficial in case the payload platform is part of a service robot. Another important advantage is that cable forces are kept low, in the worst case situation the largest cable force is equal to the total dynamic load, while the reachable area is extended.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the essential features of the

invention will be described in detail by showing preferred embodiments, with reference to the figures of the attached drawing.

In the following, for purposes of explanation and not limitation, specific details are set forth for aerial tethered/cable suspended service robots, in order to provide a thorough understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details and can be applied to

facilitating three-dimensional movement of any payload.

FIGURE 1 is a schematic side view illustrating the advantage of the present invention over the prior art.

FIGURES 2/A, 2/B and 2/C show different loading

situations for the cabling system. FIGURE 3 is a perspective view of an embodiment in which the arrester unit is a disk.

FIGURE 4 schematically illustrates an embodiment in which the arrester unit is a ring.

FIGURE 5 shows possible locations of the winding mechanism that actuates the anchoring cable. DETAILED DESCRIPTION

FIGURE 1 shows the advantage of using an arrester unit AU along the main cables MC. Using the cabling system for service robot, unreachable areas can be identified around some furniture like a table. Compared to the cabling system of service robots according to the prior art (right), the unreachable area (dotted) for a cabling system using

arrester unit AU (left) is smaller.

In FIGURE 2/A and 2/B, different loading cases can be seen. In this embodiment, a payload platform PP is suspended by three main cables MC. The upper end of the Main cables MC are attached to three separate winding mechanisms WM, connected to a suspension unit SU such as a pylon, providing the vertical motion to the payload platform PP by actuating the lengths of each main cable MC individually.

Above h the payload platform PP an arrester unit AU is applied keeping the main cables MC together, which arrester unit is anchored to the payload platform PP at a centre point by an anchoring cable AC. As it is seen in FIGURE 2/C, the gravity force G shown only in FIGURES 2/A and 2/B of the payload PL is balanced by forces Kl, K2, K3 applied in the main cables MC and the force K4 of the anchoring cable AC. With respect to the concepts utilizing an arrester unit AU, the forces Kl, K2, K3 applied in the main cables MC are also functions of the distance h between the payload platform PP and the arrester unit AU, i.e. the length of the anchoring cable AC. This means that cable forces Kl, K2, K3 are high if the distance h is small, and are low if the distance h is large. On one hand, very large forces - i.e. much higher than the

aggregated gravitational and accelerational forces - are not reasonable to be provided by the winding mechanisms WM, on the other hand, a very long cable can eliminate the

advantage of the invention described in the previous figure (FIGURE 1). Consequently, the length of the cable is a trade off, the exact value of which is the outcome of a

calculation.

In the worst case situation the largest cable force is equal to the total weight of the unit (see FIGURE 2 /A) if no vertical acceleration of the payload is assumed. In the optimal case, the cable forces are equal to each other, i.e. Kl=K2=K3=G/3 due to symmetry (see FIGURE 2/B) . The force loading the anchoring cable AC can be calculated based on the notation used in the figure as

where h is the distance of the arrester unit AU from the payload platform PP, and 1 is the radius of the circle along which the base points are situated. The friction forces acting upon the arrester unit AU are neglected.

A perspective view in FIGURE 3 shows a better outlook of the relation among the arrester unit AU, the main cables MC, the payload platform PP and the anchoring cable AC. In this embodiment, the arrester unit (AU) is disk with

apertures leading the main cables (MC) through the disk. The arrester unit AU is attached to the payload platform PP by the anchoring cable the upper end of which is anchored to the arrester unit AU and the lower one is anchored to the centre point of the payload platform PP. In this embodiment rollers RO are applied to minimize the friction between the arrester unit AU and the main cables MC. FIGURE 4 depicts a further embodiment of the arrester unit AU. In this case all the main cables MC are bundled with a ring as arrester unit AU, which is fixed to the payload platform PP by the anchoring cable AC. As it is depicted in the enlarged part of the figure, three opposite points of the ring at its circumference are arranged for anchoring the upper end of the anchoring cable AC. The length of the anchoring cable AC is actuated by a further winding mechanism WM placed on the payload platform PP.

However it is possible to place this winding mechanism WM on the arrester unit AU or on a suspension unit SU.

In FIGURES 5/A, 5/B and 5/C, different locations of the winding mechanism WM of the anchoring cable can bee seen. In FIGURE 5/A the winding mechanism WM is placed on the payload platform PP and in FIGURE 5/B it is placed on the arrester unit AU. In FIGURE 5/C the winding mechanism MM is located on a suspension unit (SU) . In this case the anchoring cable is led through a pulley placed on the payload platform PP.

Although the present invention has been described in detail with reference to only a few exemplary embodiments, those skilled in the art will appreciate that various modifications can be made without departing from the

invention. Accordingly, the invention is defined only by the following claims, which are intended to embrace all

equivalents thereof.

Claims

1. A payload suspension system for facilitating three- dimensional movement of a suspended payload attached to a payload platform (PP) suspended by main cables (MC) connected to a suspension unit (SU) , characterized in that,

- the main cables (MC) are traversed through an

arrester unit (AU) keeping the main cables (MC) together,

- the arrester unit (AU) is connected to the payload platform (PP) .

2. The payload suspension system of claim 1 characterized in that the arrester unit (AU) is connected to the payload platform (PP) by an anchoring cable (AC).

3. The payload suspension system of claim 2 characterized in that the length of the anchoring cable (AC) is actuated by a winding mechanism (WM) .

4. The payload suspension system of claim 3 characterized in that the winding mechanism (WM) is placed on the payload platform (PP) .

5. The payload suspension system of claim 3 characterized in that the winding mechanism (WM) is placed on the arrester unit (AU) .

6. The payload suspension system of claim 3 characterized in that the winding mechanism (WM) is placed on the suspension unit (SU) .

7. The payload suspension system of claim 1 characterized in that the arrester unit (AU) is a ring surrounding the main cables (AC) .

8. The payload suspension system of claim 7 characterized in that at least three points of the ring at its circumference are arranged for anchoring the upper end of the anchoring cable (AC) .

9. The payload suspension system of claim 7 characterized in that the lower end of the anchoring cable (AC) is anchored on a centre point of the payload platform (PP)•

10. The payload suspension system of claim 1 characterized in that the arrester unit (AU) is a disk with apertures (A) around its circumference for the main cables (MC) and with an anchor point (AP) in the middle of the disk.

11. The payload suspension system of claim 10 characterized in that the apertures (A) of the arrester unit (AU) are provided with rollers (RO) .