The demand of lightweight robots that can operate with high dynamics and a high degree of precision is increasing. This cannot be achieved with one component alone as Ralf Moseberg, Head of Business Field Industrial Automation at Schaeffler explains, "Schaeffler has addressed this challenge head-on by developing new main bearings, motors, gears and a fully integrated sensor system for lightweight robots and cobots. Our solution package will enable cobots to operate around 50% faster and simultaneously transport 30% heavier loads, while our innovative concept in the form of sensor-based strain wave gears will provide the required sensitivity. This will enable us to explore other areas of application.”
Cobots that combine high dynamics and sensitivity offer much greater flexibility in use, from collaborative applications to classic industrial robots, which not only result in a much faster return on investment and significantly increased productivity, but also in stimulated demand for cobots.
Precision strain wave gears
Schaeffler has expanded its range of precision strain wave gears to accommodate a broader range of applications in its robotics portfolio with two series for lightweight robots: RT1 for the high-torque range and RT2 for standard torque applications.
Thanks to the high torque density, RT1 strain wave gears permit particularly compact articulated arms for higher-than-average loads. Their low weight and compact design make them an ideal choice for use in cobots. The backlash-free and wear-resistant tooth system of the strain wave gears guarantees excellent positional accuracy over the entire operating life.
In both series, the high tilting rigidity of Schaeffler's XZU double row angular contact needle roller bearings enable a cobot structure with considerably increased rigidity.
Torque sensor system
The precision strain wave gears now come with the added option of a fully integrated torque sensor system, which delivers high-precision torque signals without the need for additional installation space, or any resulting loss of rigidity in the overall mechanical system.
A durable sensor solution suitable for volume application has been unavailable in the market to date – a gap which Schaeffler has now succeeded in closing with its sensor-based precision strain wave gears.
Unlike other solutions available on the market, the torque sensor structure in sensor-based strain wave gears is applied to the flexspline on a permanent basis using thin-layer technology. The sensor system not only supports safety functions but also provides precise, sensitive position and process control. The torque signals can also be used in the development of an active vibration compensation system, with the aim of achieving shorter transient response times for highly dynamic motion profiles.
Dynamic motors
The motors in Schaeffler’s UPRS series offer a smaller design envelope, reduced weight, a higher torque density, and speeds that are, on average, 80% higher than conventional drives available on the market.
The newly developed motors are designed as axial flux machines, with coils designed in a PCB configuration. The special circuit board design permits a high copper content by volume, good heat dissipation, and improved energy efficiency.
By optimising the motor design, Schaeffler engineers have succeeded in reducing the cogging torque to almost zero with noticeably positive effects in areas including teaching mode. The systematic use of innovative materials in the active components of the motor reduces the weight of the motors and increases their energy efficiency. As is standard with frameless motors, the bearing supports of the adjacent construction are also used, thus reducing both the design envelope and weight.
With these developments, Schaeffler's Ralph Moseberg concludes " Robots is a field with considerable growth potential and we have everything we need to fulfill the future system component requirements".
