CARDAN JOINTS WITH AXIS OFFSET IN （万向关节轴偏移量的）.PDFVIP

CARDAN JOINTS WITH AXIS OFFSET IN SINGULARITY FREE HEXAPOD STRUCTURES FOR NANOMETER RESOLUTION Rainer Gloess Advanced Mechatronics Physik Instrumente (PI) GmbH Co. KG Karlsruhe, GERMANY INTRODUCTION The main advantages of hexapod systems are conditions or special scan routines demand user-friendly compact shipment design and high different structure design. [1] stiffness. Two different parallel-kinematic designs are An improvement in the accuracy of hexapod realized at PI: systems can be achieved via better Systems with constant length of the struts: actuator/sensor, cable outlet and joint design. vertical motion of the lower joints For most applications the use of external 6 DOF horizontal motion of the lower joints sensor systems at the platform is not suitable due to the sensor performance, the size or the price of such sensor systems. Therefore, sensor systems inside the struts have to be used as a reference for each single axis of the hexapod. The platform position will be determined by the strut-sensor systems, the joints – and the mechanical tolerances (which can be calibrated). This paper describes different joints used in FIGURE 2. a: Vertical moving joints – for small nanometer repeatable, parallel-kinematic and high load and vacuum flange mounted systems. Such joint designs require large hexapods. b: Horizontal moving joints – for low computing power of the controller.