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This paper presents a coupled observer that uses accelerometer, gyrometer and vision sensors to provide estimates of pose and linear velocity for an aerial robotic vehicle. The observer is based on a non-linear complimentary filter framework and incorporates adaptive estimates of measurement bias in gyrometers and accelerometers commonly encountered in low-cost inertial measurement systems. Asymptotic...
In this paper, we provide an answer to the long-standing question of designing global asymptotically stable proportional-integral-derivative (PID) regulators with only position feedback for uncertain robots. Our main contribution is to establish the global asymptotic stability of the controlled system by using Lyapunov direct method and LaSalle's invariance principle. We provide explicit conditions...
This paper presents improvements over the dynamics window approach (I-DWA), used for computing in real time autonomous robot navigation. A novel objective function that includes Lyapunov stability criteria is proposed. It allows to guarantee a global and asymptotic convergence to the goal, resulting in a more simple and self-contained approach. Experimental results with simulated and real environments...
Based on the methodology of sliding mode, this paper presents a robust controller for a class of under-actuated systems with mismatched uncertainties. Such a system consists of a nominal system and the mismatched uncertainties. The structural characteristic of the nominal system is that it is made up of several subsystems. Based on this characteristic, the hierarchical structure of the sliding mode...
Various forms of animal locomotion have been studied in the biological literature. Neuroscience research suggests the existence of central pattern generators (CPGs), neural networks that generate periodic signals for locomotion. We study simplified modular architectures based on CPGs for robotic applications, and show their global exponential stability using partial contraction analysis. The proposed...
The paper describes the modeling and control of a robot with flexible joints (the DLR medical robot), which has strong mechanical couplings between pairs of joints realized with a differential gear-box. Because of this coupling, controllers developed before for the DLR light-weight robots cannot be directly applied. The previous control approach is extended in order to allow a multi-input-multi-output...
Aimed at achieving ultra-high precision control performance for high-end applications of robots equipped with harmonic drives, an adaptive joint torque controller developed previously is extended to all the joints of seven degrees of freedom (DOF) robot manipulator using four different types of harmonic drives. The developed adaptive joint torque controller uses additional sensing including the joint...
This paper gives new motion generation methods for mechanical port-Hamiltonian systems. First, we propose a generation method based on an asymptotic stabilization method without damping assignment. This asymptotic stabilization method preserves the Hamiltonian structure in the closed-loop system although the controller itself is not a port-Hamiltonian system. Second, we propose another method based...
The advantages of reconfigurable robots have been discussed in the specialized literature. Conventionally, reconfigurability was a direct result of using modular joints. In this paper we discuss the configuration control and recalibration of a different class of reconfigurable robots, one which is equipped with lockable cylindrical joints with no actuators or sensors. Such a robot can be as versatile...
This paper considers a feedback control technique for cable suspended robots under input constraints, using control Lyapunov functions (CLF). The motivation for this work is to develop an explicit feedback control law for cable robots to asymptotically stabilize it to a goal point with positive input constraints. The main contributions of this paper are as follows: (i) proposal for a CLF candidate...
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