Remote Center of Compliance

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A Remote Center of Compliance gives in to translational and rotational deviations during an insertion process.

A Remote Center of Compliance (also Remote Center Compliance or RCC ) is a passive compensation element on gripping robots and manipulators. It serves as a joining aid, e.g. B. for inserting bolts, does without additional sensors or measuring systems and enables an industrial robot to compensate for small position errors.

Compliant elements like an RCC are a method of compensating for small position and angle inaccuracies. Other passive joining aids are z. B. the vibration or a floating bearing (lockable air bearing). RCC need auxiliary joining surfaces, such as a bevel (bevel) at the inlet opening or a pointed bolt.

An Instrumented Remote Center of Compliance (IRCC) contains additional optical sensors that register the deformation of the elastomer elements.

The RCC module counts as a robot accessory and is inserted between the robot wrist and the gripping tool. The ability to yield is achieved through the use of elastomeric joints or mechanical spring constructions. With such joining aids, position inaccuracies of approx. ± 3 mm and angular inaccuracies of approx. ± 2 ° can be compensated. Depending on the model, this enables compensation in all three translational and rotational axes (corresponds to six different degrees of freedom of movement). As a result, the industrial robot needs less power for such assembly tasks, but loses its positional accuracy in several axes.

The first RCC module was developed in the US Charles Stark Draper laboratory and patented in 1976.

Designs

  • The simplest design is the one in which two flanges are connected by several elastomer elements. These elastomer elements consist of a high sequence of thin elastomer layers and rigid layers, for example thin metal plates. Rigid elements attached to the long side (as shown in the picture) prevent the elastomers from stretching, but allow the individual layers to shift. This simple version is only used for small masses and slow motion sequences. With higher partial weights and rapid traversing movements, the greatest possible number of such elastomer elements should be used within the RCC module for reasons of stability.
  • Additionally integrated overload bolts limit excessive deflection both when joining and when approaching. The flexibility can be locked by an integrated pneumatic cylinder . Such designs should be used with short cycle times and large masses to be moved.
  • An additional mechanism made up of up to four joints can prevent rotation around the joint axis when torsional moments act . This type of construction should be used when inertial forces lead to strong torsional moments during rapid rotary and swiveling movements, or when a transmission of torsional moments is required when joining (for example, when screwing).

Applications

A typical area of ​​application is inserting bolts into bores. A robot moves its gripper, with which it holds the slightly sharpened bolt , as shown in the adjacent illustration, over a slightly sunk hole into which the bolt is to be inserted. If the insertion position has not been reached 100%, the bolt can still be inserted straight into the hole without the bolt tilting, since the RCC module compensates for the inaccuracy in such a way that it does not allow tilting, but only lateral displacement.

Another area of ​​application is the automatic assembly of printed circuit boards in push-through assembly .

literature

Individual evidence

  1. ↑ a b Jürgen Rogos: Intelligent sensor systems in manufacturing technology . Berlin ; New York: Springer-Verlag, 1989, ISBN 978-3-540-51488-6 , limited preview in the Google book search
  2. ↑ T. Takamori, K. Tsuchija: Robotics, Mechatronics and Manufacturing Systems , in Transactions of the IMACS / SICE International Symposium on Robotics, Mechatronics and Manufacturing Systems, Kobe, Japan September 16-20, 1992, ISBN 0-444-89700-3 , limited preview in Google Book Search
  3. ↑ Manufacturer information (accessed on May 20, 2017)
  4. ↑ Patent US4098001 : Remote center compliance system. Published June 4, 1978 , inventor: Paul C. Watson. ‌
  5. ↑ Dieter W. Wloka: Robot systems 1: Technical basics . Berlin, Heidelberg: Springer Berlin Heidelberg, 1992, ISBN 978-3-642-93510-7 , limited preview in the Google book search