P1.10 - MEMS Based Position and Motion Sensors for Controlling Complex Parallel Mechanisms

SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
Proceedings SENSOR 2009, Volume II
P1 - Mechanical Sensors
T. Mekonnen, J. Schlattmann - Hamburg University of Technology, Hamburg, Germany
271 - 276


In order to effectively control motion in machines, measurements of positions, displacements, tilts, velocities, accelerations, vibrations, etc. are necessary. Sensors employed to measure such parameters have to be optimally selected and integrated based on given applications in order to assure efficient, accurate, and reliable functioning of the machine system. The general objective of this application research is to develop and validate sensor based techniques for real time pose determination and control of parallel mechanisms. Specifically, it deals with the implementation of stable walking of the biped robot Centaurob. For the stability control, motion sensors are to be selected systematically.
Centaurob is a statically stable walking robot, whose basic working principle was successfully verified in a previous research work. The basic mechanical structure of Centaurob is made up of two serially coupled Stewart platforms (hexapods). The position and orientation in space (pose) of the robot have to be determinable using selected motion sensors. In hexapod structure the control variables are the lengths of the actuator links. But since solving forward kinematic equations of motion for such parallel mechanisms is not deterministic, it is not possible to compute the pose of moving platforms in absolute terms based on the lengths. Therefore, sensor-based solution methods are to be employed to compute the robot’s forward kinematics and hence pose. Because of a stringent size/shape and precision requirements, it is challenging to find a fitting sensor solution. In order to identify the measured parameters, first a mathematical model of static walking robot has to be developed. In the following sections, the robot control model approaches and involved problems will be briefly discussed followed by a systematic motion sensor selection and integration methods.