Model-Based Control Concept of 6-DOF Parallel Kinematics Machine for High Dynamic Automation

摘要

The integration of robotics in manufacturing systems still remains an important issue inflexible and intelligent automation. New and modern machine tool concepts such as parallel kinematics machines (PKM) become more and more important especially in high speed manufacturing. Operating PKM in the range of high dynamics requires a sophisticated model-based control concept due to the complex structure of such systems which is characterized by highly nonlinear and coupled dynamics. This paper presents an integral concept by systematically taking into account the majority of relevant dynamic influences. For such machines orderly lacks of dynamic accuracy are caused by conventional Single Joint Control. These lacks require the implementation of "Computed-Force Control" or "Feedforward Control". The complex rigid-body dynamics as well as the friction forces in all active and passive joints are considered by the real-time computation of the inverse dynamics. Furthermore the design and parameterization of the actuator PID-controllers is achieved by a model-based approach. Since the inertia and structural stiffness of parallel kinematics machines depend on the actual spatial configuration, their consideration by online calculation of mass- and stiffness-matrix with high efficient algorithms becomes necessary. The Single Joint Control parameters are then adapted online. This assures that the adjustment of the constant desired control dynamics does not depend on the configuration. The concept's successful implementation on the high speed hexapod PaLiDA is illustrated with experimental results.