Cable-driven parallel robots (also called cable robots, cable-suspended robots or wire-driven robots) are a type of

parallel manipulator A parallel manipulator is a mechanical system that uses several computer-controlled serial chains to support a single platform, or end-effector. Perhaps, the best known parallel manipulator is formed from six linear actuators that support a mo ...

s in which flexible

cables Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a he ...

are used as

actuator An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an ...

s. One end of each cable is reeled around a

rotor ROTOR was an elaborate air defence radar system built by the British Government in the early 1950s to counter possible attack by Soviet bombers. To get it operational as quickly as possible, it was initially made up primarily of WWII-era syst ...

twisted by a

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gene ...

, and the other end is connected to the

end-effector An end effector is the device at the end of a robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot. In the strict definition, which originates from serial robotic manipu ...

. One famous example of cable robots is

Skycam __NOTOC__ Skycam is a computer-controlled, stabilized, cable-suspended camera system. The system is maneuvered through three dimensions in the open space over a playing area of a stadium or arena by computer-controlled cable-drive system. It is r ...

which is used to move a suspended

camera A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photograp ...

stadium A stadium (: stadiums or stadia) is a place or venue for (mostly) outdoor sports, concerts, or other events and consists of a field or stage completely or partially surrounded by a tiered structure designed to allow spectators to stand or sit ...

s. Cables are much lighter than rigid linkages of a serial or

parallel robot {{Cat main, Robot kinematics Kinematics In physics, kinematics studies the geometrical aspects of motion of physical objects independent of forces that set them in motion. Constrained motion such as linked machine parts are also described as k ...

, and very long cables can be used without making the mechanism massive. As a result, the end-effector of a cable robot can achieve high

acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Acceleration is one of several components of kinematics, the study of motion. Accelerations are Euclidean vector, vector ...

s and

velocities Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector quantity, meaning that both m ...

and work in a very large workspace (e.g. a stadium). Numerous

engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

articles have studied the

kinematics In physics, kinematics studies the geometrical aspects of motion of physical objects independent of forces that set them in motion. Constrained motion such as linked machine parts are also described as kinematics. Kinematics is concerned with s ...

and dynamics of cable robots (e.g. see In The International Journal of Robotics Research 27.9 (2008): 1007–1026. for an enhanced of the concept). Dynamic analysis of cable robots is not the same as that of other parallel robots because cables can only pull an object but they cannot push. Therefore, the manipulator is able to perform a task only if the

force In physics, a force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. In mechanics, force makes ideas like 'pushing' or 'pulling' mathematically precise. Because the Magnitu ...

in all cables are non-negative. Accordingly, the workspace of cable robots is defined as a region in space where the end-effector is able to exert the required wrench (force and moment vectors) to the surroundings while all cables are in tension (non-negative forces). Many research works have focused on workspace analysis and optimization of cable robots. Workspace and controllability of cable robots can be enhanced by adding cables to structure of the robot. Consequently, redundancy plays a key role in design of cable robots. Skycam Husky Stadium

However, workspace analysis and obtaining positive tension in cables of a

redundant Redundancy or redundant may refer to: Language * Redundancy (linguistics), information that is expressed more than once Engineering and computer science * Data redundancy, database systems which have a field that is repeated in two or more table ...

cable robot can be complicated. In general, for a redundant robot, infinite solution may exist, but for a redundant cable robot a solution is acceptable only if all the elements of tension vector are non-negative. Finding such a solution can be challenging, especially if the end-effector is working along a

trajectory A trajectory or flight path is the path that an object with mass in motion follows through space as a function of time. In classical mechanics, a trajectory is defined by Hamiltonian mechanics via canonical coordinates; hence, a complete tra ...

and a continuous and smooth distribution of tensions is desired in cables. In literature, several methods have been presented to solve such problems a

computational method A computation is any type of arithmetic or non-arithmetic calculation that is well-defined. Common examples of computation are mathematical equation solving and the execution of computer algorithms. Mechanical or electronic devices (or, historica ...

is introduced based on

Particle Swarm Optimization In computational science, particle swarm optimization (PSO) is a computational method that Mathematical optimization, optimizes a problem by iterative method, iteratively trying to improve a candidate solution with regard to a given measure of qu ...

method to find continuous smooth solutions along a trajectory for a general redundant cable robot). In addition to parallel cable robots, cables have been used as

s in serial robots as well. By employing cables as actuators a mechanism can be designed much smaller and lighter (e.g. a human-like finger mechanism actuated by cables is presented in S. Abyaneh, O. Saber, H. Zohoor (2013), "A Cable Driven Grasping Mechanism Using Lock/Unlock Constraints", In Proceedings of the ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE), August 4–7, Portland, OR, DETC2013-13109.).

References

{{reflist Mechanisms (engineering) Robots

See also

References