@conference {159,
	title = {Multi-robot manipulation controlled by a human with haptic feedback},
	booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
	year = {2015},
	abstract = {The interaction of a single human with a team of cooperative robots, which collaboratively manipulate an object, poses a great challenge by means of the numerous possibilities of issuing commands to the team or providing appropriate feedback to the human. In this paper we propose a formationbased approach in order to avoid deformations of the object and to virtually couple the human to the formation. Here the human can be interpreted as a leader in a leader-follower formation with the robotic manipulators being the followers. The results of a controllability analysis in such a leader-follower formation suggest that it is beneficial to measure the state of the human (leader) by all physically cooperating manipulators (followers). The proposed approach is evaluated in a full-scale multi-robot cooperative manipulation experiment with humans.},
	author = {D. Sieber and S. Music and S. Hirche}
}
@conference {160,
	title = {Dynamic Movement Primitives for Cooperative Manipulation and Synchronized Motions},
	booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},
	year = {2014},
	author = {J. Umlauft and D. Sieber and S. Hirche}
}
@conference {162,
	title = {Formation-based approach for multi-robot cooperative manipulation based on optimal control design},
	booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},
	year = {2013},
	abstract = {Cooperative manipulation, where several robots collaboratively transport an object, poses a great challenge in robotics. In order to avoid object deformations in cooperative manipulation, formation rigidity of the robots is desired. This work proposes a novel linear state feedback controller that combines both optimal goal regulation and a relaxed form of the formation rigidity constraint, exploiting an underlying distributed impedance control scheme. Since the presented control design problem is in a biquadratic LQR-like form, we present an iterative design algorithm to compute the controller. As an intermediate result, an approximated state-space model of an interconnected robot system is derived. The controller design approach is evaluated in a full-scale multi-robot experiment.},
	url = {;},
	author = {D. Sieber and F. Deroo and S. Hirche}
}
@conference {163,
	title = {An impedance-based control architecture for multi-robot cooperative dual-arm mobile manipulation},
	booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems},
	year = {2013},
	address = {Tokyo},
	doi = {10.1109/IROS.2013.6696370},
	url = {;},
	author = {S. Erhart and D. Sieber and S. Hirche}
}
@conference {161,
	title = {Iterative optimal feedback control design under relaxed rigidity constraints for multi-robot cooperative manipulation},
	booktitle = {Proceedings of the 52nd IEEE Conference on Decision and Control (CDC)},
	year = {2013},
	address = {Florenz, Italien},
	abstract = {Cooperative manipulation of multiple robots presents an interesting control application scenario of coupled dynamical systems with a common goal. Here, we treat the problem of moving a formation of physically interconnected robots to a desired goal while maintaining the formation. This control problen is for example relevant in cooperative transport of an object from an initial to a final configuration by mobile robotic manipulators. To achieve the control goal we formulate an LQR-like optimal control problem that, in addition to goal regulation and minimization of input energy, includes the formation rigidity constraint in a relaxed form expressed as a biquadratic penalty term. The control problem is solved by two different iterative algorithms, a gradient descent using adjoint states and a quasi-Newton method, that determine a static linear state-feedback matrix. The proposed control design and the iterative algorithms are validated and compared in numerical simulations showing the efficacy of both approaches.},
	url = {;},
	author = {D. Sieber and F. Deroo and S. Hirche}
}
