Thesis (M.S.)--Ohio University, November, 2008. / Title from PDF t.p. Release of full electronic text on OhioLINK has been delayed until May 30, 2009. Includes bibliographical references (p. 77-80)

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Dieser Vortrag befasst sich mit der Prozesskette bei der Entwicklung spinnenartiger Laufroboter. Es wird eine Möglichkeit der Abstraktion von der Natur aufgezeigt, sowie dessen Überführung in ein technisches System. Das kinematische Modell wird anschließend in MSC Adams simuliert.

<p>Generating and stabilizing periodic motions in nonlinear systems is a challenging task. In the control system community this topic is also known as limit cycle control. In recent years a framework known as Virtual Holonomic Constraints (VHC) has been developed as one of the solutions to this problem. The aim of this thesis is to give an insight into this approach and its practical application.</p><p>The contribution of this work is primarily the experimental validation of the theory. A step by step procedure of this methodology is given for motion planning, as well as for controller design. Three particular setups were chosen for experiments: the inertia wheel pendulum, the Furuta pendulum and the two-link planar pendulum. These under-actuated mechanical systems are well known benchmarking setups for testing advanced control design methods.</p><p>Further application is intended for cases such as biped robot walking/running, human and animal locomotion analysis, etc.</p>

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This thesis is about control and balance stability of leggedlocomotion. It also presents a combination of tools that makesit easier to design controllers for large and complicated robotsystems. The thesis is divided into four parts. The first part studies and analyzes how walking machines arecontrolled, examining the literature of over twenty machinesbriefly, and six machines in detail. The goal is to understandhow the controllers work on a level below task and pathplanning, but above actuator control. Analysis and comparisonis done in terms of: i) generation of trunk motion; ii)maintaining balance; iii) generation of leg sequence andsupport patterns; and iv) reflexes. The next part describes WARP1, a four-legged walking robotplatform that has been builtwith the long term goal of walkingin rough terrain. First its modular structure (mechanics,electronics and control) is described, followed by someexperiments demonstrating basic performance. Finally themathematical modeling of the robot’s rigid body model isdescribed. This model is derived symbolically and is general,i.e. not restricted to WARP1. It is easily modified in case ofa different number of legs or joints. During the work with WARP1, tools for model derivation,control design and control implementation have been combined,interfaced and augmented in order to better support design andanalysis. These tools and methods are described in the thirdpart. The tools used to be difficult to combine, especially fora large and complicated system with many signals and parameterssuch as WARP1. Now, models derived symbolically in one tool areeasy to use in another tool for control design, simulation andfinally implementation, as well as for visualization andevaluation—thus going from equation to action. In the last part we go back to“equation”wherethese tools aid the study of balance stability when complianceis considered. It is shown that a legged robot in a“statically balanced”stance may actually beunstable. Furthermore, a criterion is derived that shows when aradially symmetric“statically balanced”stance on acompliant surface is stable. Similar analyses are performed fortwo controllers of legged robots, where it is the controllerthat cause the compliance. <b>Keywords</b>legged locomotion, control, balance, leggedmachines, legged robots, walking robots, walking machines,compliance, platform stability, symbolic modeling

No description available.

<p>This thesis is about control and balance stability of leggedlocomotion. It also presents a combination of tools that makesit easier to design controllers for large and complicated robotsystems. The thesis is divided into four parts.</p><p>The first part studies and analyzes how walking machines arecontrolled, examining the literature of over twenty machinesbriefly, and six machines in detail. The goal is to understandhow the controllers work on a level below task and pathplanning, but above actuator control. Analysis and comparisonis done in terms of: i) generation of trunk motion; ii)maintaining balance; iii) generation of leg sequence andsupport patterns; and iv) reflexes.</p><p>The next part describes WARP1, a four-legged walking robotplatform that has been builtwith the long term goal of walkingin rough terrain. First its modular structure (mechanics,electronics and control) is described, followed by someexperiments demonstrating basic performance. Finally themathematical modeling of the robot’s rigid body model isdescribed. This model is derived symbolically and is general,i.e. not restricted to WARP1. It is easily modified in case ofa different number of legs or joints.</p><p>During the work with WARP1, tools for model derivation,control design and control implementation have been combined,interfaced and augmented in order to better support design andanalysis. These tools and methods are described in the thirdpart. The tools used to be difficult to combine, especially fora large and complicated system with many signals and parameterssuch as WARP1. Now, models derived symbolically in one tool areeasy to use in another tool for control design, simulation andfinally implementation, as well as for visualization andevaluation—thus going from equation to action.</p><p>In the last part we go back to“equation”wherethese tools aid the study of balance stability when complianceis considered. It is shown that a legged robot in a“statically balanced”stance may actually beunstable. Furthermore, a criterion is derived that shows when aradially symmetric“statically balanced”stance on acompliant surface is stable. Similar analyses are performed fortwo controllers of legged robots, where it is the controllerthat cause the compliance.</p><p><b>Keywords</b>legged locomotion, control, balance, leggedmachines, legged robots, walking robots, walking machines,compliance, platform stability, symbolic modeling</p>

The field of autonomous walking robots has been dominated by the trajectory-control approach, which rigidly dictates joint angle trajectories at the expense of both energy efficiency and stability, and the passive dynamics approach, which uses no actuators, relying instead on natural mechanical dynamics as the sole source of control. Although the passive dynamics approach is energy efficient, it lacks the ability to modify gait or adapt to disturbances. Recently, minimally actuated walkers, or dynamic walkers, have been developed that use hip or ankle actuators---knees are always passive---to regulate mechanical energy variations through the timely application of joint torque pulses. Despite the improvement minimal actuation has provided, energy efficiency remains below target values and perturbation rejection capability (i.e., stability) remains poor. In this dissertation, we develop and analyze a simplified robotic system to assess biologically inspired methods of improving energy efficiency and stability in dynamic walkers. Our system consists of a planar, dynamically swinging leg with hip and knee actuation. Neurally inspired, nonlinear oscillators provide closed-loop control without overriding the leg's natural dynamics. We first model the passive stiffness of muscles by applying stiffness components to the joints of a hip-actuated swinging leg. We then assess the effect active knee control has on unperturbed and perturbed leg swinging. Our results indicate that passive joint stiffness improves energy efficiency by reducing the actuator work required to counter gravitational torque and by promoting kinetic energy transfer between the shank and thigh. We also found that active knee control 1) is detrimental to unperturbed leg swinging because it negatively affects energy efficiency while producing minimal performance improvement and 2) is beneficial during perturbed swinging because the perturbation rejection improvement outweighs the reduction in energy efficiency. By analyzing the effects of applying passive joint stiffness and active knee control to dynamic walkers, this work helps to bridge the gap between the performance capability of trajectory-control robots and the energy-efficiency of passive dynamic robots.

Generating and stabilizing periodic motions in nonlinear systems is a challenging task. In the control system community this topic is also known as limit cycle control. In recent years a framework known as Virtual Holonomic Constraints (VHC) has been developed as one of the solutions to this problem. The aim of this thesis is to give an insight into this approach and its practical application. The contribution of this work is primarily the experimental validation of the theory. A step by step procedure of this methodology is given for motion planning, as well as for controller design. Three particular setups were chosen for experiments: the inertia wheel pendulum, the Furuta pendulum and the two-link planar pendulum. These under-actuated mechanical systems are well known benchmarking setups for testing advanced control design methods. Further application is intended for cases such as biped robot walking/running, human and animal locomotion analysis, etc.