Master of Science

thesisThis thesis focuses on the design, modeling, fabrication, and testing of a ?ying and walking robot, called the Dynamic Underactuated Flying-Walking (DUCK) robot. The DUCK robot combines a high-mobility ?ying platform, such as a quadcopter (quadrotor helicopter), with passive-dynamic legs to create a versatile system that can ?y and walk. One of the advantages of using passive-dynamic legs for walking is that additional actuators are not needed for terrestrial locomotion, therefore simplifying the design, reducing overall weight, and decreasing power consumption. First, a mathematical model is developed for the DUCK robot, where the modeling combines the passive-dynamic walking mechanism with the swinging mass of the aerial platform. Second, simulations based on the model are used to help guide the design of two prototype robots, speci?cally to tailor the shape of the feet and the dimensions of the passive-dynamic walking mechanism. Third, an energy analysis is performed to compare the performances between ?ying and walking. More specifically, simulation results show that continuous active walking has a comparable energy efficiency to that of flying for the two prototype designs. For design Version 1, it is estimated that the robot is able to walk up to 1600 meters on a 30kJ battery (standard Li-Po battery) with a cost of transport of 1.0, while the robot can potentially fly up to 1800 meters horizontally with the weight of its legs and up to 2300 meters without the weight of its legs. Design Version 2 is estimated to be able to walk up to 4600 meters on a 30kJ battery with a cost of transport of .50, while it could fly up to 2600 meters with the weight of its legs or 4300 meters without its legs. The cost of transport of flying is estimated to be .89 in all scenarios. Finally, experimental results demonstrate the feasibility of combining an aerial platform with passive-dynamic legs to create an effective flying and walking robot. Two modes of walking are experimentally demonstrated: (1) passive walking down inclined surfaces for low-energy terrestrial locomotion and (2) active (powered) walking leveraging the capabilities of the flying platform, where thrust from the quadcopter's rotors enables the DUCK robot to walk on flat surfaces or up inclined surfaces

Selective Laser Sintering of Passive Dynamic Ankle-Foot Orthoses

Passive dynamic ankle-foot orthoses (AFO’s) are used to improve gait performance in those with various neuromuscular disorders. An important design characteristic of passive dynamic AFOs is the storage and release of elastic energy within its structure to help satisfy the energetic demands of walking. Thus, minimizing energy dissipation through internal friction is a fundamental criterion for selecting the appropriate AFO material. This study compared the mechanical damping of a carbon-fiber AFO to three geometrically identical AFO’s fabricated using selective laser sintering with different materials. Mechanical damping characteristics ranked the materials as Nylon 11 (best), followed by DuraformTM PA and DuraformTM GF (worst).Mechanical Engineerin

Modeling Framework and Software Tools for Walking Robots

In research on passive dynamic walking, the aim is to study and design robots that walk naturally, i.e., with little or no control effort. McGeer [1] and others (e.g. [2, 3]) have shown that, indeed, robots can walk down a shallow slope with no actuation, only powered by gravity.\ud In this work, we derive mathematical models of walking ro- bots to better understand the dynamics that determine the walking behavior, and to design controllers that e.g. in- crease robustness against changing environments. We use the port-Hamiltonian framework, as it has the advantage of explicitly showing energy-flows inside and into the system. Thus, it allows a direct efficiency study as well as the possi- bility to connect external elements in a ‘physical’ way using ports, instead of using just torque/force signals

Passive Sole Constraining Method to Stabilize 3D Passive Dynamic Walking

Inspired by the function of a toe and a lateral arch of a human foot, we propose a method to stabilize the biped walk by attaching unactuated toes and lateral arches. The toes and lateral arches work as adaptive braking of sagittal and lateral directions. They touch on the ground at the angle where the biped exceedingly inclines. After touching on the floor, the center of rotation changes at the landing positions. This change causes the reduction of the exceeding angular velocities toward sagittal and lateral directions. By setting appropriate heights of the toe and lateral arch during the swing phase, the walking robot is expected to be stabilized. To analyze the effects of the toe, we derived equations of motions and the state transition functions for a simplified 3D passive dynamic walker with toes. We clarified the potential stabilizing effect of the method from numerical simulations and preliminary experiments by a real-world biped with toes. Note that the proper setting of heights and the verification of the effect of lateral arches are on the way

Reinforcement Learning of Stable Trajectory for Quasi-Passive Dynamic Walking of an Unstable Biped Robot

Biped walking is one of the major research targets in recent humanoid robotics, and many researchers are now interested in Passive Dynamic Walking (PDW) [McGeer (1990)] rather than that by the conventional Zero Moment Point (ZMP) criterion [Vukobratovic (1972)]. The ZMP criterion is usually used for planning a desired trajectory to be tracked by

Realisation of an energy efficient walking robot

In this video the walking robot ‘Dribbel’ is presented, which has been built at the Control Engineering group of the University of Twente, the Netherlands. This robot has been designed with a focus on minimal energy consumption, using a passive dynamic approach. It is a so-called four-legged 2D walker; the use of four legs prevents it from falling sideways. During the design phase extensive use has been made of 20-sim. This power port based modeling package was used to simulate the dynamic behaviour of the robot in order to estimate the design parameters for the prototype. The parameters obtained by the simulation were then used as a basis for the real robot. The real robot is made of aluminum and weighs 9.5 kg. Each of the nine joints (one hip, four knees, four feet) has a dedicated electronic driver board for interfacing the joint sensors. For walking a simple control loop is used: when the front feet touch the ground, the rear legs are swung forward. The control parameters can be adjusted online using a serial link. Using this simple control loop, the robot walks at a speed of 1.2 km/h and a step frequency of 1.1 Hz. The hip actuator consumes 6.7 W. The walking behaviour of the robot is very similar to the simulation, regarding both walking motion and power consumption. With the serial link real time data acquisition in the simulation package (running on the PC) is possible. This allows for advanced verification and fine tuning of the control algorithm. The simulation package can also be used directly within the control loop. Future research is planned on energy based control of the walking motion, using impedance control for the hip actuator and design of more advanced (and actuated) foot shapes

Design and experimental analysis of legged locomotive robots

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 20-21).In this thesis, I present the design and motion-capture analysis of two previously well-studied dynamic-walking machines, the rimless wheel and the compass gait robot. These robots were the basis for my undergraduate research at the Computer Science/Artificial Intelligence Laboratory (CSAIL) at the Massachusetts Institute of Technology. The rimless wheel is a real-world physical realization built to compare to a long-analyzed model, the simplest example of passive dynamic walking. Despite the seemingly deterministic model, undeniable experimental evidence for unpredictable stochasitic behavior is observed. The compass gait is the second iteration of a previous design by Dr. Fumiya Iida in my laboratory. Both machines are among the most fundamental walking models, and are important for developing energy-efficient dynamic walkers.by Timothy J. Villabona.S.B