output encoder vs. motor encoder plus INI

Our customers can choose between motor encoders / Ini switches and igus output encoders (both incremental angle sensors).

Motor encoder / INI (RL-D-RBT-xxxxx-BC):

+) proven industrial standard, double ended signal transmission (A/A-, B/B-), high resolution (500 signals / motorturn * transmission of the joint)

-) 3 cables per axis (motor, encoder, INI), reverse play of the joint is not noticed, mechanical changes in the joint are not noticed (i.e. temperature, load,..)

Output encoder (RL-D-RBT-xxxxx-BC-AE):

+) cheaper, less cables, easy to replace, we measured better repeatability values for multi axis arms in different use cases (detailed results will be shown in ~6 weeks)

-) not industrially proven, single ended signal transmission (A, B) => danger of signal loss is higher,  EMC not proven

Conclusion: We recommend to use our output encoders for non critical (non industrial) applications, for industrial applications we recommend motor encoders or testing of the output encoder in the given environment.

DOWNLOAD SECTION. New data sheets for output encoders:

englisgh version:  RL-D Sensorik Doku (#5)

german version:  RL-D Sensors Doc (E#5)

how to build a robolink arm (videos)

we supply either components (joints, motors, cables,…) or complete electro-mechanical joint arms. compared to industrial robots, the composition of a robolink joint arm is quite easy and can be reproduced by “everybody”. We show the composition of a 5 DOF joint arm in 3 single video clips:

  1. assembly of joints, “motorkits” and “Inikits” (for 0-point reference),
  2. assembly of an arm
  3. cabling of the arm

these films shall help you to understand the idea of our joint kit and how easy it is to change, modify or configure our arms.

Video 1) joint assembly

Video 2) arm assembly

Video 3) cabling of a joint arm

igus open source soccer robot (with University of Bonn), first kicks…

We have been involved in the development of a new open source teen size soccer robot for 2 years now (and the improvement still goes on!). The main development was done by the University of Bonn, institute AIS, Professor Sven Behnke, who also developped our open source robolink software IME (igus motion editor), igus contrubuted the design and technology of the outer shell parts (made by 3D printing / SLS). In the next stage we will improve the cabeling inside the robot with our chainflex know-how for often bending cables.

This youtube video shows the current state of the software development (thanks to Philipp Allgeuer for sharing it).

The open source project is documented by Prof. Behnke here with open source data: http://www.nimbro.net/OP

And the 3D Step data of the robot shell (3D printed parts) are shared here by igus: https://github.com/igusGmbH/HumanoidOpenPlatform

igus open source soccer robot (with University of Bonn), first kicks...

robolink joints and grippers

Some words about grippers in combination with our robolink joint arms:

Different grippers can be attached to our arm tubes. One common solution are pneumatic grippers. They are (often) lightweight and not so expansive. We can adapt several grippers from SCHUNK, FESTO, GIMATIC, FIPA and others easily. Please ask us. Also suction systems are (usually) no problem for us.

But often pneumatics are not possible to be used (for example in mobile robots). In that case, we have the choice between electrical grippers or our robolink wire driven gripper. The igus gripper can not be adapted to 4 or 5 DOF arms because of 2 reasons: 1) the leading of the wire through multiple joints causes friction, as the gripper is spring loaded, the spring may not be sufficient in strength to close the gripper properly. 2) the aditional bowden cable can not be leaded through the lower joint because of space restriction. The igus gripper may thus be combined only with 2 or 3 DOF arms. We are workink on a better solution in this case.

My favorite product in the moment for the combination with our system is the electrical gripper by GIMATIC called MPPM 1606 (2 jaws) or MPTM 1606 (3 jaws). It is lightweight and really easy to control. Datasheets in ENG/IT and DE/FR are attached. We can adapt the grippers and also lead the electrical cable through any of our arms. Please ask us in case of interest!


[forcecaption]various pneumatic grippers


[forcecaption]igus wire driven gripper (spring loaded)        


[forcecaption]GIMATIC electrical gripper



Feedthrough of draw wires

For the series connection of joints, the 4 draw wires of the second (or upper) joint should be conducted through the first (or lower) joint. This feedthrough must be done in such a way that a movement of the lower joint does not alter the wire lengths of the feedthrough, which means Bowden cables are needed.

In the pictures you can see the schematic and actual feedthrough of the 4 draw wires by means of igus® plastic Bowden cables.

In the connecting rods of the joints (“skeleton”), the wires and cables are free in contrast. In total, a maximum of the following elements can be routed through an RL-50 joint:

4 draw wires plus 2 sensor cables (joint 1 and 2) plus 2 additional cables max. d4 (compressed air or electric).

[forcecaption]Diagram of wire arrangement in the feedthrough (white = rotate, yellow = pivot)


[forcecaption]Feedthrough: 1) compressed air hose d=4mm, 2) 4 draw wires, 3) sensor cable