University of Twente Student Theses


User-input device based command and control of the youBot using a RaMstix embedded board

Spil, T.A. (2016) User-input device based command and control of the youBot using a RaMstix embedded board.

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Abstract:The youBot is a mobile manipulator developed by KUKA to be used in research and education. The youBot consists of a base with four omniwheels and an arm with five joints. Reusable software was developed termed the motion stack for use with the youBot, but (mis)use of this software during several research projects resulted in broken gearboxes in the youBot. A new method of control has been realized termed the Inverse Kinematics with Kinematic Constraints (IKwKC) solver, which replaces the motion stack. The IKwKC solver utilizes an analytic closed formInverse Kinematic solver, but when the formulas of the IK solver calculate unreachable joint positions the Kinematic Constraints solver recalculates the IK formulas with different redundancy parameters such that reachable joint positions are calculated and the desired end effector position is reached. With the IKwKC solver the range ofmotion is almost doubled compared with the IK solver it is based on. A connection between the youBot and the RaMstix is realized using EtherCAT such that the youBot can be controlled with the 20-sim 4C toolchain. Advantages of the connection between the youBot and RaMstix are: the motors in the joint can be commanded at PWM level, the youBot is controlled hard real-time and safety features are built in the toolchain. This connection has been realized successfully, all inputs and outputs of the youBot are accessible. The execution time of one cycle is on average È 150 us, but peaks every 30 cycles to 300 us. The cause is likely a result of the network stack which is not real-time. Nevertheless, the youBot can be controlled with a frequency of up to 2 kHz. The implementation of a real-time network communication, like RTNet, is recommended. To showcase the toolchain and the new method of control a demo has been developed. For this demo the toolchain has been expanded to allow for set-point generation and communication. This allows the youBot to be controlled wirelessly via wifi with either an Xbox controller or a keyboard.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Programme:Electrical Engineering MSc (60353)
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