Browsing by Subject "Controller structures"
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Item Open Access Control of underactuated planar hexapedal pronking through a dynamically embedded SLIP monopod(IEEE, 2010) Ankarali, M.M.; Saranlı, Uluç; Saranli, A.Pronking (aka. stotting) is a gait in which all legs are used in synchrony, resulting in long flight phases and large jumping heights that may potentially be useful for mobile robots on rough terrain. Robotic instantiations of this gait suffer from severe pitch instability either due to underactuation, or the lack of sufficient feedback. Nevertheless, the dynamic nature of this gait suggests that the Spring-Loaded Inverted Pendulum Model (SLIP), a very successful predictive model for both natural and robotic runners, would be a good basis for more robust and maneuverable robotic pronking. In this paper, we describe how "template-based control", a controller structure based on the embedding of a simple dynamical "template" within a more complex "anchor" system, can be used to achieve stable and controllable pronking for a planar, underactuated hexapod model. In this context, high-level control of the gait is regulated through speed and height commands to the SLIP template, while the embedding controller based on approximate inverse-dynamics and carefully designed passive dynamics ensures the stability of the remaining degrees of freedom. We show through extensive simulation experiments that unlike existing open-loop alternatives, the resulting control structure provides stability, explicit maneuverability and significant robustness against sensor and actuator noise. ©2010 IEEE.Item Open Access On Smith predictor-based controller design for systems with integral action and time delay(IEEE, 2013-06) Taşdelen, Uğur; Özbay, HitayA new Smith predictor based controller is proposed for systems with integral action and flexible modes under input-output time-delay. The design uses controller parametrization and aims to achieve a set of performance and robustness objectives. Compared to existing Smith predictor based designs, disturbance attenuation property is improved, with respect to periodic disturbances at a known frequency. A two-degree of freedom controller structure is shown to be helpful in shaping the transient response under constant reference inputs. Stability robustness properties of this system are also investigated. Simulation results demonstrate the effectiveness of the proposed controller. © 2013 IEEE.Item Open Access Quadrupedal bounding with an actuated spinal joint(IEEE, 2011) Çulha, Utku; Saranlı, UluçMost legged vertebrates use flexible spines and supporting muscles to provide auxiliary power and dexterity for dynamic behaviors, resulting in higher speeds and additional maneuverability during locomotion. However, most existing legged robots capable of dynamic locomotion incorporate only a single rigid trunk with actuation limited to legs and associated joints. In this paper, we investigate how quadrupedal bounding can be achieved in the presence of an actuated spinal joint and characterize associated performance improvements compared to bounding with a rigid robot body. In the context of both a new controller structure for bounding with a body joint and existing bounding controllers for the rigid trunk, we use optimization methods to identify the highest performance gait parameters and establish that the spinal joint allows increased forward speeds and hopping heights. © 2011 IEEE.