Intelligent Bearing Solution for Parallel Kinematic Robots: Fewer Components, Higher Efficiency


Triple Ring Bearing Saves Installation Space and Time

At the Productronica trade fair, Schaeffler Group Industrial presents its developmental work performed on a new triple ring bearing which helps to simplify the structure of handling robots with parallel kinematics and significantly increases their operating efficiency. Parallel kinematic robots are compact handling devices with large stroke. Their main field of application is found in semi-conductor production, for example in wafer and flat panel transfer systems.

Deployment of the newly developed triple ring bearings helps to reduce the number of components and thus simplifies the structure and assembly of the robot. At the same time, it permits a more precise selection of the bearings as these are used according to the loads rather than geometric boundary conditions. The bearings are thus optimally adjusted to the robot movements, which ensures much greater operating efficiency. Moreover, Schaeffler's smart bearing solution enables the reduction of the number of drives and simplifies their connection. Stationary mounting onto the base frame thus also enables different application-optimized drive variants to be used.
Conventional parallel kinematic designs comprise two parallel-actuated arms starting from the load gripper that are connected to the ankles via the wrists and intermediate pivotal points (elbow joints). These ankles are attached to a rotatable base plate which is needed as an adapter between the center bearing and the base bearings. The dimensions of the individual bearings are determined by the mass of goods to be transported and by the bending moment resulting from the lever between the masses and rotating bearing axis. In straight position the largest moments develop in the center bearing. The large diameter of the center bearing is due to this fact - and to the fact that it has to accommodate the two base bearings next to each other (see illustration below).

Schaeffler Group Industrial's triple ring bearings replace the ankles and wrists as well as the robot's center bearing. The two elbow joints remain unchanged. So only four bearings are used instead of seven previously. The number of components and the assembly expenses are significantly reduced. The size of the bearing in the base frame is only determined with the new solution by the bending moment resulting from the level between the center of mass and the bearing rotating axis. Only one drive each is needed for controlling the two parallel-actuated arms. The drives cause the arm-in and arm-out movements as well as the rotation of the entire assembly. Since the drives are connected to the base frame stationary, a straightforward power supply is guaranteed and, depending on the demands, a range of different drive variants can be used: gears, toothed belts or torque motors.

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