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A Dual-SLIP Model For Dynamic Walking In A Humanoid Over Uneven TerrainLiu, Yiping January 2015 (has links)
No description available.
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Passive control of bipedal robots via tail morphologyRaphael, Jonathan S.T. January 2012 (has links)
Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Legged robots offer significant advantages over their wheeled and treaded counterparts, enabling access to huge sectors of otherwise non-navigable terrain. To develop these walkers many engineers have looked to nature for inspiration, but the field of bipedal research has been focused almost exclusively on human locomotion. Other than Homo sapiens, the only regularly bipedal walkers are members of Theropoda, a clade that includes modern day birds as well as all the carnivorous dinosaurs. Whereas birds evolved extensively for flying, their ancestors, e.g. Velociraptor and Tyrannosaurus Rex, were much more specialized for dynamic terrestrial motion. We submit that there is good reason to look to theropod body geometry for an efficient alternative walking model.
In this thesis, a novel model was developed in order to examine the mechanics of such specialized bipedal motion. Instead of a traditional anthropomorphic model maintaining a vertically balanced torso, this research synthesized a dinomorphic model that consists of a horizontal spine with counterbalanced torso and tail masses pivoting around the hip joint. The system model developed herein was an extension of the simple rimless wheel representation and aimed to capture critical events in the cycle of bipedal motion while avoiding chaotic regimes.
Mathematical models and computer simulations were designed iteratively and in parallel. Once the system dynamics and the energy losses from inelastic impact were derived, then all the equations were nondimensionalized. Theoretical bounds on efficiency were found, and an attempt was made to experimentally quantify the effects of each geometric system parameter. A region of improved performance was identified, indicating non-negligible benefits to tailed morphologies over tail-less ones. It is suggested that further research might adapt and apply this model to the more complex bipedal compass gait. Ideally these findings will enable and encourage the design of legged robots with a horizontal load-bearing frame, demonstrating advantage over anthropomorphic walkers. / 2031-01-01
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On Exploration of Mechanical Insights into Bipedal Walking: Gait Characteristics, Energy Efficiency, and ExperimentationAlghooneh, Mansoor January 2014 (has links)
Human walking is dynamic, stable, and energy efficient. To achieve such remarkable legged locomotion in robots, engineers have explored bipedal robots developed based on two paradigms: trajectory-controlled and passive-based walking. Trajectory-controlled bipeds often deliver energy-inefficient gaits. The reason is that these bipeds are controlled via high-impedance geared electrical motors to accurately follow predesigned trajectories. Such trajectories are designed to keep a biped locally balanced continually while walking.
On the other hand, passive-based bipeds provide energy-efficient gaits. The reason is that these bipeds adapt to their natural dynamics. Such gaits are stable limit-cycles through entire walking motion, and do not require being locally balanced at every instant during walking. However, passive-based bipeds are often of round/point foot bipeds that are not capable of achieving and experiencing standing, stopping, and some important bipedal gait phases and events, such as the double support phase. Therefore, the goals of this thesis are established such that the aforementioned limitations on trajectory-controlled and passive-based bipeds are resolved.
Toward the above goal, comprehensive simulation and experimental explorations into bipedal walking have been carried out. Firstly, a novel systematic trajectory-controlled gait-planning framework has been developed to provide mechanical insights into bipedal walking in terms of gait characteristics and energy efficiency. For the same purpose, a novel mathematical model of passive-based bipedal walking with compliant hip-actuation and compliant-ankle flat-foot has been developed. Finally, based on mechanical insights that have been achieved by the aforementioned passive-based model, a physical prototype of a passive-based bipedal robot has been designed and fabricated. The prototype experimentally validates the importance of compliant hip-actuation in achieving a highly dynamic and energy efficient gait.
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Bipedal Robotic Walking on Flat-Ground, Up-Slope and Rough Terrain with Human-Inspired Hybrid Zero DynamicsNadubettu Yadukumar, Shishir 1986- 14 March 2013 (has links)
The thesis shows how to achieve bipedal robotic walking on flat-ground, up-slope and rough terrain by using Human-Inspired control. We begin by considering human walking data and find outputs (or virtual constraints) that, when calculated from the human data, are described by simple functions of time (termed canonical walking functions). Formally, we construct a torque controller, through model inversion, that drives the outputs of the robot to the outputs of the human as represented by the canonical walking function; while these functions fit the human data well, they do not apriori guarantee robotic walking (due to do the physical differences between humans and robots). An optimization problem is presented that determines the best fit of the canonical walking function to the human data, while guaranteeing walking for a specific bipedal robot; in addition, constraints can be added that guarantee physically realizable walking. We consider a physical bipedal robot, AMBER, and considering the special property of the motors used in the robot, i.e., low leakage inductance, we approximate the motor model and use the formal controllers that satisfy the constraints and translate into an efficient voltage-based controller that can be directly implemented on AMBER. The end result is walking on flat-ground and up-slope which is not just human-like, but also amazingly robust. Having obtained walking on specific well defined terrains separately, rough terrain walking is achieved by dynamically changing the extended canonical walking functions (ECWF) that the robot outputs should track at every step. The state of the robot, after every non-stance foot strike, is actively sensed and the new CWF is constructed to ensure Hybrid Zero Dynamics is respected in the next step. Finally, the technique developed is tried on different terrains in simulation and in AMBER showing how the walking gait morphs depending on the terrain.
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The Design and Realization of a Sensitive Walking PlatformChernyak, Vadim 24 April 2012 (has links)
Legged locomotion provides robots with the capability of adapting to different terrain conditions. General complex terrain traversal methodologies solely rely on proprioception which readily leads to instability under dynamical situations. Biological legged locomotion utilizes somatosensory feedback to sense the real-time interaction of the feet with ground to enhance stability. Nevertheless, limited attention has been given to sensing the feet-terrain interaction in robotics. This project introduces a paradigm shift in robotic walking called sensitive walking realized through the development of a compliant bipedal platform. Sensitive walking extends upon the success of sensitive manipulation which utilizes tactile feedback to localize an object to grasp, determine an appropriate manipulation configuration, and constantly adapts to maintain grasp stability. Based on the same concepts of sensitive manipulation, sensitive walking utilizes podotactile feedback to enhance real-time walking stability by effectively adapting to variations in the terrain. Adapting legged robotic platforms to sensitive walking is not as simple as attaching any tactile sensor to the feet of a robot. The sensors and the limbs need to have specific characteristics that support the implementation of the algorithms and allow the biped to safely come in contact with the terrain and detect the interaction forces. The challenges in handling the synergy of hardware and sensor design, and fabrication in a podotactile-based sensitive walking robot are addressed. The bipedal platform provides contact compliance through 12 series elastic actuators and contains 190 highly flexible tactile sensors capable of sensing forces at any incident angle. Sensitive walking algorithms are provided to handle multi-legged locomotion challenges including stairs and irregular terrain.
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On controllable stiffness bipedal walkingGhorbani, Reza 28 May 2008 (has links)
Impact at each leg transition is one of the main causes of energy dissipation in most
of the current bipedal walking robots. Minimizing impact can reduce the energy loss.
Instead of controlling the joint angle profiles to reduce the impact which requires significant
amount of energy, installing elastic mechanisms on the robots structure is
proposed in this research, enabling the robot to reduce the impact, and to store part
of the energy in the elastic form which returns the energy to the robot. Practically,
this motivates the development of the bipedal walking robots with adjustable stiffness
elasticity which itself creates new challenging problems. This thesis addresses some of
the challenges through five consecutive stages. Firstly, an adjustable compliant series
elastic actuator (named ACSEA in this thesis) is developed. The velocity control mode
of the electric motor is used to accurately control the output force of the ACSEA. Secondly,
three different conceptual designs of the adjustable stiffness artificial tendons
(ASAT) are proposed each of which is added at the ankle joint of a bipedal walking
robot model. Simulation results of the collision phase (part of the gait between
the heel-strike and the foot-touch-down in bipedal walking) demonstrate significant
improvements in the energetics of the bipedal walking robot by proper stiffness adjustment
of ASAT. In the third stage, in order to study the effects of ASATs on reducing
the energy loss during the stance phase, a simplified model of bipedal walking is introduced
consisting of a foot, a leg and an ASAT which is installed parallel to the ankle
joint. A linear spring, with adjustable stiffness, is included in the model to simulate the generated force by the trailing leg during the double support phase. The concept
of impulsive constraints is used to establish the mathematical model of impacts in
the collision phase which includes the heel-strike and the foot-touch-down. For the
fourth stage, an energy-feedback-based controller is designed to automatically adjust
the stiffness of the ASAT which reduces the energy loss during the foot-touch-down.
In the final stage, a speed tracking (ST) controller is developed to regulate the velocity
of the biped at the midstance. The ST controller is an event-based time-independent
controller, based on geometric progression with exponential decay in the kinetic energy
error, which adjusts the stiffness of the trailing-leg spring to control the injected energy
to the biped in tracking a desired speed at the midstance. Another controller is also
integrated with the ST controller to tune the stiffness of the ASAT when reduction in
the speed is desired. Then, the local stability of the system (biped and the combination
of the above three controllers) is analyzed by calculating the eigenvalues of the linear
approximation of the return map. Simulation results show that the combination of the
three controllers is successful in tracking a desired speed of the bipedal walking even
in the presence of the uncertainties in the leg’s initial angles.
The outcomes of this research show the significant effects of adjustable stiffness artificial
tendons on reducing the energy loss during bipedal walking. It also demonstrates
the advantages of adding elastic elements in the bipedal walking model which benefits
the efficiency and simplicity in regulating the speed. This research paves the way
toward developing the dynamic walking robots with adjustable stiffness ability which
minimize the shortcomings of the two major types of bipedal walking robots, i.e., passive
dynamic walking robots (which are energy efficient but need extensive parameters
tuning for gait stability) and actively controlled walking robots (which are significantly
energy inefficient). / May 2008
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On controllable stiffness bipedal walkingGhorbani, Reza 28 May 2008 (has links)
Impact at each leg transition is one of the main causes of energy dissipation in most
of the current bipedal walking robots. Minimizing impact can reduce the energy loss.
Instead of controlling the joint angle profiles to reduce the impact which requires significant
amount of energy, installing elastic mechanisms on the robots structure is
proposed in this research, enabling the robot to reduce the impact, and to store part
of the energy in the elastic form which returns the energy to the robot. Practically,
this motivates the development of the bipedal walking robots with adjustable stiffness
elasticity which itself creates new challenging problems. This thesis addresses some of
the challenges through five consecutive stages. Firstly, an adjustable compliant series
elastic actuator (named ACSEA in this thesis) is developed. The velocity control mode
of the electric motor is used to accurately control the output force of the ACSEA. Secondly,
three different conceptual designs of the adjustable stiffness artificial tendons
(ASAT) are proposed each of which is added at the ankle joint of a bipedal walking
robot model. Simulation results of the collision phase (part of the gait between
the heel-strike and the foot-touch-down in bipedal walking) demonstrate significant
improvements in the energetics of the bipedal walking robot by proper stiffness adjustment
of ASAT. In the third stage, in order to study the effects of ASATs on reducing
the energy loss during the stance phase, a simplified model of bipedal walking is introduced
consisting of a foot, a leg and an ASAT which is installed parallel to the ankle
joint. A linear spring, with adjustable stiffness, is included in the model to simulate the generated force by the trailing leg during the double support phase. The concept
of impulsive constraints is used to establish the mathematical model of impacts in
the collision phase which includes the heel-strike and the foot-touch-down. For the
fourth stage, an energy-feedback-based controller is designed to automatically adjust
the stiffness of the ASAT which reduces the energy loss during the foot-touch-down.
In the final stage, a speed tracking (ST) controller is developed to regulate the velocity
of the biped at the midstance. The ST controller is an event-based time-independent
controller, based on geometric progression with exponential decay in the kinetic energy
error, which adjusts the stiffness of the trailing-leg spring to control the injected energy
to the biped in tracking a desired speed at the midstance. Another controller is also
integrated with the ST controller to tune the stiffness of the ASAT when reduction in
the speed is desired. Then, the local stability of the system (biped and the combination
of the above three controllers) is analyzed by calculating the eigenvalues of the linear
approximation of the return map. Simulation results show that the combination of the
three controllers is successful in tracking a desired speed of the bipedal walking even
in the presence of the uncertainties in the leg’s initial angles.
The outcomes of this research show the significant effects of adjustable stiffness artificial
tendons on reducing the energy loss during bipedal walking. It also demonstrates
the advantages of adding elastic elements in the bipedal walking model which benefits
the efficiency and simplicity in regulating the speed. This research paves the way
toward developing the dynamic walking robots with adjustable stiffness ability which
minimize the shortcomings of the two major types of bipedal walking robots, i.e., passive
dynamic walking robots (which are energy efficient but need extensive parameters
tuning for gait stability) and actively controlled walking robots (which are significantly
energy inefficient).
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On controllable stiffness bipedal walkingGhorbani, Reza 28 May 2008 (has links)
Impact at each leg transition is one of the main causes of energy dissipation in most
of the current bipedal walking robots. Minimizing impact can reduce the energy loss.
Instead of controlling the joint angle profiles to reduce the impact which requires significant
amount of energy, installing elastic mechanisms on the robots structure is
proposed in this research, enabling the robot to reduce the impact, and to store part
of the energy in the elastic form which returns the energy to the robot. Practically,
this motivates the development of the bipedal walking robots with adjustable stiffness
elasticity which itself creates new challenging problems. This thesis addresses some of
the challenges through five consecutive stages. Firstly, an adjustable compliant series
elastic actuator (named ACSEA in this thesis) is developed. The velocity control mode
of the electric motor is used to accurately control the output force of the ACSEA. Secondly,
three different conceptual designs of the adjustable stiffness artificial tendons
(ASAT) are proposed each of which is added at the ankle joint of a bipedal walking
robot model. Simulation results of the collision phase (part of the gait between
the heel-strike and the foot-touch-down in bipedal walking) demonstrate significant
improvements in the energetics of the bipedal walking robot by proper stiffness adjustment
of ASAT. In the third stage, in order to study the effects of ASATs on reducing
the energy loss during the stance phase, a simplified model of bipedal walking is introduced
consisting of a foot, a leg and an ASAT which is installed parallel to the ankle
joint. A linear spring, with adjustable stiffness, is included in the model to simulate the generated force by the trailing leg during the double support phase. The concept
of impulsive constraints is used to establish the mathematical model of impacts in
the collision phase which includes the heel-strike and the foot-touch-down. For the
fourth stage, an energy-feedback-based controller is designed to automatically adjust
the stiffness of the ASAT which reduces the energy loss during the foot-touch-down.
In the final stage, a speed tracking (ST) controller is developed to regulate the velocity
of the biped at the midstance. The ST controller is an event-based time-independent
controller, based on geometric progression with exponential decay in the kinetic energy
error, which adjusts the stiffness of the trailing-leg spring to control the injected energy
to the biped in tracking a desired speed at the midstance. Another controller is also
integrated with the ST controller to tune the stiffness of the ASAT when reduction in
the speed is desired. Then, the local stability of the system (biped and the combination
of the above three controllers) is analyzed by calculating the eigenvalues of the linear
approximation of the return map. Simulation results show that the combination of the
three controllers is successful in tracking a desired speed of the bipedal walking even
in the presence of the uncertainties in the leg’s initial angles.
The outcomes of this research show the significant effects of adjustable stiffness artificial
tendons on reducing the energy loss during bipedal walking. It also demonstrates
the advantages of adding elastic elements in the bipedal walking model which benefits
the efficiency and simplicity in regulating the speed. This research paves the way
toward developing the dynamic walking robots with adjustable stiffness ability which
minimize the shortcomings of the two major types of bipedal walking robots, i.e., passive
dynamic walking robots (which are energy efficient but need extensive parameters
tuning for gait stability) and actively controlled walking robots (which are significantly
energy inefficient).
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Algoritmy pro řízení pohybu dvounohého robota / Algorithms for Movement Control of Bipedal RobotPokorný, Jan January 2010 (has links)
This thesis is focused on using softcomputing method for learning bipedal robot to walk. Robot is represented by virtual model. At the beginning are the motivation and reasons for processing this theme. Next is devised shape of the robot which will be used. Then are selected libraries used by simulation. Further is devised system of robot learning algorithms. The most important of them is SOMA which is therefore described more. Due to assumed computational complexity is part of thesis focused on optimalization and simplification. One chapter focuses on measurement of quality of solution approximation. At the end there is an evaluation of thesis results.
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Natural, Efficient Walking for Compliant Humanoid RobotsGriffin, Robert James 02 November 2017 (has links)
Bipedal robots offer a uniquely flexible platform capable of navigating complex, human-centric environments. This makes them ideally suited for a variety of missions, including disaster response and relief, emergency scenarios, or exoskeleton systems for individuals with disabilities. This, however, requires significant advances in humanoid locomotion and control, as they are still slow, unnatural, inefficient, and relatively unstable. The work of this dissertation the state of the art with the aim was of increasing the robustness and efficiency of these bipedal walking platforms. We present a series of control improvements to enable reliable, robust, natural bipedal locomotion that was validated on a variety of bipedal robots using both hardware and simulation experiments.
A huge part of reliable walking involves maximizing the robot's control authority. We first present the development of a model predictive controller to both control the ground reaction forces and perform step adjustment for walking stabilization using a mixed-integer quadratic program. This represents the first model predictive controller to include step rotation in the optimization and leverage the capabilities of the time-varying divergent component of motion for navigating rough terrain. We also analyze the potential capabilities of model predictive controllers for the control of bipedal walking.
As an alternative to standard trajectory optimization-based model predictive controls, we present several optimization-based control schemes that leverage more traditional bipedal walking control approaches by embedding a proportional feedback controller into a quadratic program. This controller is capable of combining multiple feedback mechanisms: ground reaction feedback (the "ankle strategy"), angular momentum (the "hip strategy"), swing foot speed up, and step adjustment. This allows the robot to effectively shift its weight, pitch its torso, and adjust its feet to retain balance, while considering environmental constraints, when available.
To enable the robot to walk with straightened legs, we present a strategy that insures that the dynamic plans are kinematically and dynamically feasible to execute using straight legs. The effects of timing on dynamic plans are typically ignored, resulting in them potentially requiring significantly bending the legs during execution. This algorithm modifies the step timings to insure the plan can be executed without bending the legs beyond certain angle, while leaving the desired footsteps unmodified. To then achieve walking with straight legs we then presented a novel approach for indirectly controlling the center of mass height through the leg angles. This avoids complicated height planning techniques that are both computationally expensive and often not general enough to consider variable terrain by effectively biasing the solution of the whole-body controller towards using straighter legs. To incorporate the toe-off motion that is essential to both natural and straight leg walking, we also present a strategy for toe-off control that allows it to be an emergent behavior of the whole-body controller.
The proposed approach was demonstrated through a series of simulation and experimental results on a variety of platforms. Model predictive control for step adjustment and rough terrain is illustrated in simulation, while the other step adjustment strategies and straight leg walking approaches are presented recovering from external disturbances and walking over a variety of terrains in hardware experiments. We discuss many of the practical considerations and limitations required when porting simulation-based controller development to hardware platforms. Using the presented approaches, we also demonstrated a important concept: using whole-body control frameworks, not every desired motion need be directly commanded. Many of these motions, such as toe-off, may simply be emergent behaviors that result by attempting to satisfy other objectives, such as desired reaction forces. We also showed that optimization is a very powerful tool for walking control, able to determine both stabilizing inputs and joint torques. / Ph. D.
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