Delta robot

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Sketchy, a portrait-drawing delta robot[1]

A delta robot is a type of parallel robot.[2] It consists of three arms connected to universal joints at the base. The key design feature is the use of parallelograms in the arms, which maintains the orientation of the end effector. By contrast a Stewart platform, can change the orientation of its end effector.[3]

The delta robots have popular usage in picking and packaging in factories because they can be quite fast, some executing up to 300 picks per minute.[4]

Contents

History [edit]

Commercial pick and place robots

The delta robot (a parallel arm robot) was invented in the early 1980s by the research team led by professor Reymond Clavel at the École Polytechnique Fédérale de Lausanne (EPFL, Switzerland).[5] The purpose of this new type of robot was to manipulate light and small objects at a very high speed, an industrial need at that time. In 1987, the Swiss company Demaurex purchased a license for the delta robot and started the production of delta robots for the packaging industry. In 1991 Reymond Clavel presents his doctoral thesis 'Conception d'un robot parallèle rapide à 4 degrés de liberté',[6] and receives the golden robot award in 1999 for his work and development of the delta robot. Also in 1999, ABB Flexible Automation starts selling its delta robot, the FlexPicker. By the end of 1999 the delta robots are also sold by Sigpack Systems.

Design [edit]

The delta robot is a parallel robot, i.e. it consists of multiple kinematic chains interconnecting the base with the end-effector. The robot can also be seen as a spatial generalisation of a four-bar linkage.[7]

The key concept of the delta robot is the use of parallelograms. These parallelograms restrict the movement of the end platform to pure translation (only movement in the X, Y or Z direction, with no rotation).

The robot's base is mounted above the workspace and all the actuators are located on it. From the base, three middle jointed arms extend. The ends of these arms are connected to a small triangular platform. Actuation of the input links will move the triangular platform along the X, Y or Z direction. Actuation can be done with linear or rotational actuators, with or without reductions (direct drive).

Since the actuators are all located in the base, the arms can be made of a light composite material. As a result of this, the moving parts of the delta robot have a small inertia. This allows for very high speed and high accelerations. Having all the arms connected together to the end-effector increases the robot stiffness, but reduces its working volume.

The version developed by Reymond Clavel has four degrees of freedom:[6] three translations and one rotation. In this case a fourth leg extends from the base to the middle of the triangular platform giving to the end effector a fourth, rotational degree of freedom around the vertical axis.

Currently other versions of the delta robot have been developed:

  • Delta with 6 degrees of freedom: developed by the company Fanuc, on the end effector is placed a serial kinematic of 3 rotational degrees of freedom
  • Delta with 4 degrees of freedom: developed by the company Adept, instead of having a forth leg coming in the middle of the end-effector, it has directly 4 parallelogram connected to the end-platform
  • Delta direct drive: a 3 degrees of freedom delta having the motor directly connected to the arms. Accelerations can be very high, from 30[8] up to 100 g.
  • Pocket Delta: developed by the company Asyril, a version of the delta Robot adapted for high-precision applications.
  • Delta Cube: developed by the LSRO, a delta robot built in a monolithic design, having flexure-hinges joints. This robot is adapted for ultra-high-precision applications.
  • Several "linear delta" arrangements have been developed where the motors drive linear actuators rather than rotating an arm. Such linear delta arrangements can have much larger working volumes than rotational delta arrangements.[9][10]

The majority of delta robots use rotary actuators. Vertical linear actuators have recently been used to produce a novel design of 3D printer.[11][12] These offer advantages over conventional leadscrew-based 3D printers of quicker access to a larger build volume, for a comparable investment in hardware.

Applications [edit]

 This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2012)

Industries that take advantage of the high speed of the delta robot are the packaging industry, medical and pharmaceutical industry. For its stiffness it is also used for surgery. Other possible applications include assembly tasks or operation in a clean room for electronic components. The structure of the delta robot can also be used to create haptic controllers,[13] such as the Force Dimension omega.x, delta.x and sigma.x devices, or the Novint Falcon game controller.

References [edit]

  1. ^ "Sketchy, a home-constructed drawing robot". Jarkman. 
  2. ^ Bonev, I. (2001) Delta Parallel Robot — the Story of Success, Online article available at http://www.parallemic.org/Reviews/Review002.html
  3. ^ Bonev, I. The True Origins of Parallel Robots. Online article available at http://www.parallemic.org/Reviews/Review007.html
  4. ^ http://www.botjunkie.com/2009/11/03/adept-quattro-is-fastest-ever-for-the-moment/
  5. ^ US 4976582 
  6. ^ a b Clavel, R. (1991) Conception d'un robot parallèle rapide à 4 degrés de liberté. Ph.D. Thesis, EPFL, Lausanne, Switzerland
  7. ^ Merlet, J.-P., Parallel Robots, Kluwer Academic Publishers, 2000.
  8. ^ Miller, K., "Modeling of Dynamics and Model-Based Control of DELTA Direct-Drive Parallel Robot," Journal of Robotics and Mechatronics, Vol. 17, No. 4, pp. 344-352, 1995.
  9. ^ "Gallery of robots - prof. Reymond Clavel"
  10. ^ Reymond CLAVEL. "Robots parallèles"
  11. ^ Johann Rocholl (6 Feb, 2012). "Rostock (delta robot 3D printer)". Thingiverse. 
  12. ^ Mike Szczys (13 July 2012). "3D printing with a delta robot that seems to simplify the concept". 
  13. ^ Sunny Bains (8 August 2007). "Feeling virtual worlds". 

External links [edit]

Wikimedia Commons has media related to: Delta robots
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