New Solutions for the Automotive Industry

Hexapods Support Industrial Robots

Because the need for multi-axis and also precision robots in production and quality processes is on the increase, industry is looking out for new types of robotics. PI offers parallel-kinematic hexapods for these tasks. The six-axis robots are able to move tools, workpieces or even complex components with weights of several kilograms to several tons with high precision in any spatial orientation, irrespective of the mounting orientation. Because hexapods can communicate directly with PLC or CNC controllers via Fieldbus interfaces, users can easily integrate the positioning systems into the automation environment.

The automotive industry has been taking advantage of parallel kinematics since the early 20th century, for example, for testing car tires. System suppliers also use this technology today. Among other things, they integrate hexapods into coordinate measuring machines to calibrate headlamps in order to comply with the high demands on precision. Hexapod robots can also be used on the production line together with industrial robots for compensating the inaccuracies of the robot arm.

Quality Assurance Testing

Positioning headlamps in a coordinate measuring machine
>> Hexapods in measuring

Production and Tool Control

Positioning a tool, a workpiece or an inspection system
>> Hexapods in mechanical engineering

Advantages of Parallel Kinematics for Industry

In the case of hexapods, all actuators act on the same platform. This allows a considerably more compact set-up than is the case with serial stacked multi-axis system. That simplifies safety circuits because the motion of the hexapod remains in a comparatively manageable workspace. Because only a single platform is set in motion, the mass to be moved is significantly lower. This results in a considerably faster response and improved dynamics. Furthermore, hexapods have a higher accuracy, because there are usually no guidings with the associated guiding errors and therefore errors do not accumulate in the individual drives.

    Compact design
    High dynamics
    High precision
    Freely definable pivot point





    Advantages of parallel kinematics from PI
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    Hexapod Systems as Intelligent Multi-Axis Drive

    In the case of a parallel-kinematic system, the Cartesian axes do not correspond to the motor axes. Coordinate transformation is therefore necessary, which cannot generally be solved in an analytical sense. Generally, there is no solution to this from an analytical point of view and therefore, a CPU-intensive, iterative algorithm is used, which recalculates the complex hexapod kinematics for each step.

    Because a digital hexapod controller takes care of the calculations and controls the individual motors in real time, users do not need to worry about complex parallel-kinematic algorithms. Displacements and rotations of the platform are simply commanded in Cartesian coordinates.

    With the help of simulation tools, it is possible to calculate the workspace during the planning phase, for example, to prevent collisions with other objects. Development libraries and application examples simplify implementation even further. An essential feature is the possibility to adapt both the position and the alignment of the reference coordinate system and the pivot point using the software.

    To adapt the trajectory perfectly to the requirements of the application, it is possible to define various coordinate systems, for example, work and tool coordinate systems, which refer to the position of the workpiece or tool.

    All functions of the PLC standard languages can be used for controlling the hexapod systems, which means that a proprietary language is not necessary. The controller communicates with the hexapod via a standard protocol. In addition to RS-232 and TCP/IP, established fieldbus protocols such as EtherCAT or PROFINET are available for this purpose. 

    With the help of these interfaces, it is possible exchange time-synchronized data in real time both with the hexapod system and any other components in the network, for example, target and actual positions or status information.

    In a typical automation application, the corresponding Cartesian target positions or trajectories are generated by a controller acting as master (e.g., a standard software PLC with TwinCAT). The target positions are then transmitted to the hexapod system, for example, via the EtherCAT protocol, and in return, the actual positions and status information can be read out.

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