Compact cable guidance for innovative robot for unloading tyres from lorries

Profile

• What was needed: e-spool energy chain, chainflex cables
• Requirements: Space-saving cable guidance was required to supply the robot. Since it rubs against the concrete floor, it also had to be wear-resistant.
• Industry: Robotics, tyre industry
• Success for the customer: With the e-spool including spring retraction, all cables are rolled up compactly. No special solution had to be designed and the project budget could be met.

Video: This robot drives into lorry trailers from where it unloads tyres autonomously. The motor, control and power cables are guided by a compact e-spool.

Problem

This 7-axis robot arm was installed on a mobile crawler platform and is used in lorries in the tyre industry. Thanks to a sophisticated gripper, vision system and artificial intelligence developed by the Michelin study and research centre in Ladoux, the robot arm identifies and grabs the tyres and places them on a conveyor belt under the robot, which transports the tyre to its processing area.
In manual mode (radio controlled), the platform can travel with the robot in all directions, with the destination being the loading/unloading dock. Once on the dock, it switches to autonomous mode. However, when working in a narrow trailer of a lorry, the robot can only perform limited forward and backward movement and can only rotate slightly to recentre. Especially for the routing of the numerous power, control and pneumatic cables from outside into the trailer where the robot works, this resulted in a space problem. Alternatives such as a battery for energy supply or a motor were out of the question due to size and weight restrictions of the robot.
Instead, an energy chain system was chosen which, with a travel of at least 14m, a speed of 12m/min and acceleration of 1m/s², is pulled horizontally behind the robot over concrete and the wooden or plastic formwork of the lorry trailer. The small difference in height between dock and trailer is also a challenge and required the most wear-free cable guidance possible. Since the chain would be a bit off-centre from the mobile platform's orbit, it needed to be able to accept twisting/deformation.

Solution

In order to meet the special requirements of cable guidance, we searched for the best technical solution in close consultation with the customer.
Finally, an e-spool with spring retraction was chosen, which today allows engineers to safely route all power and data cables as well as pneumatic hoses to the robot platform.
To ensure that the unrolled energy chain could also move in the Y direction, the e-spool was mounted on a turntable with the 1400 series energy chain. Another specification concerned the last gliders of the chain, which were mounted backwards, so that the cable guide is lower above the ground when the e-spool is unrolled.
Additional sensors have also been installed on the energy chain to stop the mobile platform before the chain runs out.  The e-spool made it possible to wind up the cables in a confined space. Thanks to the integrated spring retraction system, the engineers were able to dispense with a motorised system for winding up the chain.
In contrast to a battery or motor-operated system, the robot could be kept as light and thin as possible. In addition, the e-spool also allowed the project team's control budget to be met. In addition to the energy chain, the cables and hoses routed in it were also purchased from us. These primarily concerned chainflex motor cables, chainflex control cables and a pneumatic hose.