Panagiotis Chatzakos | National Technical University of Athens (original) (raw)
Papers by Panagiotis Chatzakos
2009 IEEE International Conference on Robotics and Automation, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilizes passively. In this paper, we show that a quadruped robot could be able to perform selfstable running behavior in significantly broader ranges of forward speed and pitch rate with suitable mechanical design. The results presented here are derived by studying the stability of passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and can be summarized as: (a) the self-stabilized behavior of a quadruped robot for a particular gait is related to the magnitude of its dimensionless inertia, (b) the values of hip separation, normalized to rest leg length, and the leg relative stiffness of a quadruped robot affect the stability and should be in inverse proportion to its dimensionless inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds.
Advances In Mobile Robotics - Proceedings of the Eleventh International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2008
In this paper the influence of knee joint on the motion of the robot and the effect of leg segmen... more In this paper the influence of knee joint on the motion of the robot and the effect of leg segmental proportions and angle between leg segments on the performance of the robot is explored via parametric analysis. The spring loaded inverted pendulum (SLIP) running in the sagittal plane, which is a simple model commonly used to analyze the basic qualitative properties of running, is used. The performance index is the cost of locomotion, which is given as the actuator power to sustain a certain motion, very close to a passive one, normalized to forward velocity per body length and robot weight. Simulation results show that the effect of leg configuration is great and that considerable variations exist on the value of the energetic cost of locomotion that makes some leg configurations more desirable than others.
2009 17th Mediterranean Conference on Control and Automation, 2009
This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and e... more This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and explores its use in formulating design guidelines that would: a) reduce steady-state roll and b) self-stabilize the rolling motion, thus making the control of the robot more straightforward. To study the effect of mechanical design in the rolling motion, a simple bounding-in-place (BIP) template is introduced as a candidate frontal plane model that captures the targeted steady-state behavior of a straight-ahead level ground running quadruped robot. This model is parametrically analyzed and local stability analysis shows that the dynamics of the open loop passive system alone can confer stability of the motion! These results might explain the success of simple, open loop running controllers on existing experimental robots and can be further used in developing control methodologies for legged robots that take advantage of the mechanical system.
Applied Bionics and Biomechanics, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.
2008 IEEE International Conference on Robotics and Automation, 2008
In legged systems design an important question applies to: "What can be inferred from the perform... more In legged systems design an important question applies to: "What can be inferred from the performance of a legged robot of a similarly configured system, but scaled to a smaller or larger size?" Our work attempts to answer this question and set the basis for a systematic approach in sizing legged robots. This paper focuses on the influence of permanent magnet DC electric drives on the size of quadruped running robots. The reason is twofold. First, many of the existing legged machines have used such actuators for propulsion. The second, the performance of electric motors scales differently from torquespeed requirements of legged robots. Specifically, we show that there exists a particularly sized quadruped running robot that is superior according to desired performance criteria, and under the existing technologic limitations and economic restraints. Therefore, valuable information on legged systems design and insight for optimizing the size of a quadruped robot emerges.
2007 Mediterranean Conference on Control & Automation, 2007
This paper attempts to set the basis for a systematic approach in designing legged robots. A dyna... more This paper attempts to set the basis for a systematic approach in designing legged robots. A dynamically stable quadruped robot running in the sagittal plane with a bounding gait is used, and a non-dimensional criterion that is based on the robot's forward speed and the required power to sustain a passive motion, is introduced. Dimensionless robot parameters ratios and desired motion variables are inputs to an optimization scheme that takes into consideration findings from experimental biology and environment specifications. Basic design guidelines, which derive from simulation results, are provided.
ASME 2010 Dynamic Systems and Control Conference, Volume 2, 2010
This paper presents a multipart pronking/ bounding controller for a quadruped robot, as well as t... more This paper presents a multipart pronking/ bounding controller for a quadruped robot, as well as the corresponding experimental results. The controller achieves given apex height and forward velocity in a quadruped robot with only one actuator per leg. A quadruped is designed and built and described in some detail. Experimental results obtained using internal sensors and highspeed camera captions show that the implemented quadruped robot performs pronking gaits and achieves bounding gaits with the desired characteristics.
Mechanism and Machine Theory, 2009
This paper attempts to set the basis for a systematic approach in designing quadruped robots empl... more This paper attempts to set the basis for a systematic approach in designing quadruped robots employing a dynamically stable quadruped running in the sagittal plane with a bounding gait, which is a simple model commonly used to analyze the basic qualitative properties of quadruped gaits that use the legs in pair. The outcome of the proposed methodology is the optimal shape of the bounding quadruped robot, i.e., the relation between its physical parameters, and the optimal size of the bounding quadruped robot, i.e., the physical magnitude of it, according to desired performance criteria. The performance criterion introduced is based on: (a) the actuator effort to sustain an active gait, very close to a passive one, and (b) the maximum payload capability of the robot for a target overall mass. The parametric study examines the behavior of the performance criterion over a range of non-dimensional variables connected to robot physical parameters and gait characteristics. The study takes into consideration data from experimental biology and ground surface properties, while it is subject to the existing technological limitations and economic restraints, i.e., the fact that there is a limited number of motor/gearbox combinations available from a practical point of view. The findings from simulation results indicate that the proposed methodology can assist in the design of new, and modifications of existing quadruped robots.
Applied Bionics and Biomechanics, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.
This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and e... more This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and explores its use in formulating design guidelines that would: a) reduce steady-state roll and b) self-stabilize the rolling motion, thus making the control of the robot more straightforward. To study the effect of mechanical design in the rolling motion, a simple bounding-in-place (BIP) template is introduced as a candidate frontal plane model that captures the targeted steady-state behavior of a straight-ahead level ground running ...
Proc. Int. Conf. on Robotics and Applications, Dec 31, 2005
In this paper, a model-based impedance controller for electrohydraulic servosystems is developed.... more In this paper, a model-based impedance controller for electrohydraulic servosystems is developed. Rigid body and electrohydraulic models, including servovalve models are employed and described by a set of integrated system equations. Friction and leakage of hydraulic elements are also included. The control law consists of two signals, a feedback and a feedforward signal. An impedance filter modifies a desired trajectory according to a specified behaviour. The modified trajectory is fed to a simplified system ...
Proceedings of RAAD, 2003
ABSTRACT-Electrohydraulic servosystems exhibit highly nonlinear behavior to the effect that class... more ABSTRACT-Electrohydraulic servosystems exhibit highly nonlinear behavior to the effect that classical linear controllers, eg, PD, usually achieve a limited performance. Load static and dynamic parameters variations are also contributing to the limitation of their position and force tracking performance. This paper presents a modelbased controller applied to a fully detailed model of an electrohydraulic servosystem aiming at improving its position and force tracking performance. Fluid, servovalve, cylinder and load dynamics are taken into ...
2009 IEEE International Conference on Robotics and Automation, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilizes passively. In this paper, we show that a quadruped robot could be able to perform selfstable running behavior in significantly broader ranges of forward speed and pitch rate with suitable mechanical design. The results presented here are derived by studying the stability of passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and can be summarized as: (a) the self-stabilized behavior of a quadruped robot for a particular gait is related to the magnitude of its dimensionless inertia, (b) the values of hip separation, normalized to rest leg length, and the leg relative stiffness of a quadruped robot affect the stability and should be in inverse proportion to its dimensionless inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds.
Advances In Mobile Robotics - Proceedings of the Eleventh International Conference on Climbing and Walking Robots and the Support Technologies for Mobile Machines, 2008
In this paper the influence of knee joint on the motion of the robot and the effect of leg segmen... more In this paper the influence of knee joint on the motion of the robot and the effect of leg segmental proportions and angle between leg segments on the performance of the robot is explored via parametric analysis. The spring loaded inverted pendulum (SLIP) running in the sagittal plane, which is a simple model commonly used to analyze the basic qualitative properties of running, is used. The performance index is the cost of locomotion, which is given as the actuator power to sustain a certain motion, very close to a passive one, normalized to forward velocity per body length and robot weight. Simulation results show that the effect of leg configuration is great and that considerable variations exist on the value of the energetic cost of locomotion that makes some leg configurations more desirable than others.
2009 17th Mediterranean Conference on Control and Automation, 2009
This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and e... more This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and explores its use in formulating design guidelines that would: a) reduce steady-state roll and b) self-stabilize the rolling motion, thus making the control of the robot more straightforward. To study the effect of mechanical design in the rolling motion, a simple bounding-in-place (BIP) template is introduced as a candidate frontal plane model that captures the targeted steady-state behavior of a straight-ahead level ground running quadruped robot. This model is parametrically analyzed and local stability analysis shows that the dynamics of the open loop passive system alone can confer stability of the motion! These results might explain the success of simple, open loop running controllers on existing experimental robots and can be further used in developing control methodologies for legged robots that take advantage of the mechanical system.
Applied Bionics and Biomechanics, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.
2008 IEEE International Conference on Robotics and Automation, 2008
In legged systems design an important question applies to: "What can be inferred from the perform... more In legged systems design an important question applies to: "What can be inferred from the performance of a legged robot of a similarly configured system, but scaled to a smaller or larger size?" Our work attempts to answer this question and set the basis for a systematic approach in sizing legged robots. This paper focuses on the influence of permanent magnet DC electric drives on the size of quadruped running robots. The reason is twofold. First, many of the existing legged machines have used such actuators for propulsion. The second, the performance of electric motors scales differently from torquespeed requirements of legged robots. Specifically, we show that there exists a particularly sized quadruped running robot that is superior according to desired performance criteria, and under the existing technologic limitations and economic restraints. Therefore, valuable information on legged systems design and insight for optimizing the size of a quadruped robot emerges.
2007 Mediterranean Conference on Control & Automation, 2007
This paper attempts to set the basis for a systematic approach in designing legged robots. A dyna... more This paper attempts to set the basis for a systematic approach in designing legged robots. A dynamically stable quadruped robot running in the sagittal plane with a bounding gait is used, and a non-dimensional criterion that is based on the robot's forward speed and the required power to sustain a passive motion, is introduced. Dimensionless robot parameters ratios and desired motion variables are inputs to an optimization scheme that takes into consideration findings from experimental biology and environment specifications. Basic design guidelines, which derive from simulation results, are provided.
ASME 2010 Dynamic Systems and Control Conference, Volume 2, 2010
This paper presents a multipart pronking/ bounding controller for a quadruped robot, as well as t... more This paper presents a multipart pronking/ bounding controller for a quadruped robot, as well as the corresponding experimental results. The controller achieves given apex height and forward velocity in a quadruped robot with only one actuator per leg. A quadruped is designed and built and described in some detail. Experimental results obtained using internal sensors and highspeed camera captions show that the implemented quadruped robot performs pronking gaits and achieves bounding gaits with the desired characteristics.
Mechanism and Machine Theory, 2009
This paper attempts to set the basis for a systematic approach in designing quadruped robots empl... more This paper attempts to set the basis for a systematic approach in designing quadruped robots employing a dynamically stable quadruped running in the sagittal plane with a bounding gait, which is a simple model commonly used to analyze the basic qualitative properties of quadruped gaits that use the legs in pair. The outcome of the proposed methodology is the optimal shape of the bounding quadruped robot, i.e., the relation between its physical parameters, and the optimal size of the bounding quadruped robot, i.e., the physical magnitude of it, according to desired performance criteria. The performance criterion introduced is based on: (a) the actuator effort to sustain an active gait, very close to a passive one, and (b) the maximum payload capability of the robot for a target overall mass. The parametric study examines the behavior of the performance criterion over a range of non-dimensional variables connected to robot physical parameters and gait characteristics. The study takes into consideration data from experimental biology and ground surface properties, while it is subject to the existing technological limitations and economic restraints, i.e., the fact that there is a limited number of motor/gearbox combinations available from a practical point of view. The findings from simulation results indicate that the proposed methodology can assist in the design of new, and modifications of existing quadruped robots.
Applied Bionics and Biomechanics, 2009
Dynamic stability allows running animals to maintain preferred speed during locomotion over rough... more Dynamic stability allows running animals to maintain preferred speed during locomotion over rough terrain. It appears that rapid disturbance rejection is an emergent property of the mechanical system. In running robots, simple motor control seems to be effective in the negotiation of rough terrain when used in concert with a mechanical system that stabilises passively. Spring-like legs are a means for providing self-stabilising characteristics against external perturbations. In this paper, we show that a quadruped robot could be able to perform self-stable running behaviour in significantly broader ranges of forward speed and pitch rate with a suitable mechanical design, which is not limited to choosing legs spring stiffness only. The results presented here are derived by studying the stability of the passive dynamics of a quadruped robot running in the sagittal plane in a dimensionless context and might explain the success of simple, open loop running controllers on existing experimental quadruped robots. These can be summarised in (a) the self-stabilised behaviour of a quadruped robot for a particular gait is greatly related to the magnitude of its dimensionless body inertia, (b) the values of hip separation, normalised to rest leg length, and leg relative stiffness of a quadruped robot affect the stability of its motion and should be in inverse proportion to its dimensionless body inertia, and (c) the self-stable regime of quadruped running robots is enlarged at relatively high forward speeds. We anticipate the proposed guidelines to assist in the design of new, and modifications of existing, quadruped robots. As an example, specific design changes for the Scout II quadruped robot that might improve its performance are proposed.
This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and e... more This paper examines the passive dynamics of straight-ahead level ground quadrupedal running and explores its use in formulating design guidelines that would: a) reduce steady-state roll and b) self-stabilize the rolling motion, thus making the control of the robot more straightforward. To study the effect of mechanical design in the rolling motion, a simple bounding-in-place (BIP) template is introduced as a candidate frontal plane model that captures the targeted steady-state behavior of a straight-ahead level ground running ...
Proc. Int. Conf. on Robotics and Applications, Dec 31, 2005
In this paper, a model-based impedance controller for electrohydraulic servosystems is developed.... more In this paper, a model-based impedance controller for electrohydraulic servosystems is developed. Rigid body and electrohydraulic models, including servovalve models are employed and described by a set of integrated system equations. Friction and leakage of hydraulic elements are also included. The control law consists of two signals, a feedback and a feedforward signal. An impedance filter modifies a desired trajectory according to a specified behaviour. The modified trajectory is fed to a simplified system ...
Proceedings of RAAD, 2003
ABSTRACT-Electrohydraulic servosystems exhibit highly nonlinear behavior to the effect that class... more ABSTRACT-Electrohydraulic servosystems exhibit highly nonlinear behavior to the effect that classical linear controllers, eg, PD, usually achieve a limited performance. Load static and dynamic parameters variations are also contributing to the limitation of their position and force tracking performance. This paper presents a modelbased controller applied to a fully detailed model of an electrohydraulic servosystem aiming at improving its position and force tracking performance. Fluid, servovalve, cylinder and load dynamics are taken into ...