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Full Dynamics LQR Control of a Humanoid Robot: An Experimental Study on Balancing and Squatting


Conference Paper



Humanoid robots operating in human environments require whole-body controllers that can offer precise tracking and well-defined disturbance rejection behavior. In this contribution, we propose an experimental evaluation of a linear quadratic regulator (LQR) using a linearization of the full robot dynamics together with the contact constraints. The advantage of the controller is that it explicitly takes into account the coupling between the different joints to create optimal feedback controllers for whole-body control. We also propose a method to explicitly regulate other tasks of interest, such as the regulation of the center of mass of the robot or its angular momentum. In order to evaluate the performance of linear optimal control designs in a real-world scenario (model uncertainty, sensor noise, imperfect state estimation, etc), we test the controllers in a variety of tracking and balancing experiments on a torque controlled humanoid (e.g. balancing, split plane balancing, squatting, pushes while squatting, and balancing on a wheeled platform). The proposed control framework shows a reliable push recovery behavior competitive with more sophisticated balance controllers, rejecting impulses up to 11.7 Ns with peak forces of 650 N, with the added advantage of great computational simplicity. Furthermore, the controller is able to track squatting trajectories up to 1 Hz without relinearization, suggesting that the linearized dynamics is sufficient for significant ranges of motion.

Author(s): Mason, S and Righetti, L. and Schaal, S.
Book Title: 2014 IEEE-RAS International Conference on Humanoid Robots
Pages: 374--379
Year: 2014
Publisher: IEEE

Department(s): Autonomous Motion, Movement Generation and Control
Bibtex Type: Conference Paper (inproceedings)

DOI: 10.1109/HUMANOIDS.2014.7041387

Address: Madrid, Spain
URL: https://ieeexplore.ieee.org/abstract/document/7041387/


  title = {Full {Dynamics} {LQR} {Control} of a {Humanoid} {Robot}: {An} {Experimental} {Study} on {Balancing} and {Squatting}},
  author = {Mason, S and Righetti, L. and Schaal, S.},
  booktitle = {2014 {IEEE}-{RAS} {International} {Conference} on {Humanoid} {Robots}},
  pages = {374--379},
  publisher = {IEEE},
  address = {Madrid, Spain},
  year = {2014},
  url = {https://ieeexplore.ieee.org/abstract/document/7041387/}