Core Actuation Promotes Self-Manipulability on a Direct-Drive Quadrupedal Robot

For direct-drive legged robots operating in unstructured environments, workspace volume and force generation are competing, scarce resources. In this paper we demonstrate that introducing geared core actuation (i.e., proximal to rather than distal from the mass center) increases workspace volume and can provide a disproportionate amount of work-producing force to the mass center without affecting leg linkage transparency. These effects are analytically quantifiable up to modest assumptions, and are demonstrated empirically on a spined quadruped performing a leap both on level ground and from an isolated foothold (an archetypal feature of unstructured terrain)

Design Of Proprioceptive Legged Robots

It has been twenty years since the advent of the first power-autonomous legged robots, yet they have still not yet been deployed at scale. One fundamental challenge in legged machines is that actuators must perform work at relatively high speed in swing but also at high torque in stance. Legged machines must also be able to “feel” the reaction forcesin both normal (to switch from swing to stance control) and tangential (to detect slip or stubbing) directions for appropriate gait-level control. This “feeling” can be accomplished by explicit force/torque sensors in the foot/leg/actuator, or by measuring the deflection of a series mechanical spring. In this thesis we analyze machines that obtain this force information directly through the implementation of highly backdriveable actuators that require no additional sensors (apart from those already required for commutation). We address the holistic design of robots with backdriveable actuators including motor, transmission, compliance, degrees of freedom, and leg design. Moreover, this work takes such actuators to the conceptual limit by removing the gearbox entirely and presenting the design and construction of the first direct-drive legged robot family (a monopod, a biped, and a quadruped). The actuator analysis that made these direct-drive machines possible has gained traction in state of the art modestly geared machines (legged robots as well as robot arms), many of which now use the same motors. A novel leg design (the symmetric five-bar, where the “knee” is allowed to ride above the “hip”) decreases the wasted Joule heating by four per unit of torque produced over the workspace compared to a conventional serial design, making the 40 cm hip-to-hip Minitaur platform possible without violating the thermal limit of its motors. A means of comparing actuator transparency (the curve representing collision energy vs. contact information) is presented and is used to compare the performance of actuators with similar continuous torque but vastly different gear ratios (1:1, 4.4:1, 51:1). This transparency can be used to show the different outcomes in a representative task where the actuators must “feel” a ball on a track through contact and then recirculate to “cage” the ball before the energy required to “feel” has caused the ball to roll out of the workspace. For a 50 g rubber ball, the direct drive actuator is able to successfully accomplish the task, but the 4.4:1 actuator is not able to cage the ball in time, and the 51:1 actuator cannot feel the ball at all before pushing it out of the workspace. Finally, the actuation and force measurement/estimation strategies of the three leading commercial legged robots are compared, alongside other considerations for real-world fielded machines. This thesis seeks to show that legged robots (both academic and commercial) whose actuators are designed with careful consideration for proprioception can have similar performance to more conventional machines, with better robustness and greatly reducedcomplexity

Affordances And Control Of A Spine Morphology For Robotic Quadrupedal Locomotion

How does a robot\u27s body affect what it can do? This thesis explores the question with respect to a body morphology common to biology but rare in contemporary robotics: the presence of a bendable back. In this document, we introduce the Canid and Inu quadrupedal robots designed to test hypotheses related to the presence of a robotic sagittal-plane bending back (which we refer to as a ``spine morphology\u27\u27). The thesis then describes and quantifies several advantages afforded by this morphological design choice that can be evaluated against its added weight and complexity, and proposes control strategies to both deal with the increase in degrees-of-freedom from the spine morphology and to leverage an increase in agility to reactively navigate irregular terrain. Specifically, we show using the metric of ``specific agility\u27\u27 that a spine can provides a reservoir of elastic energy storage that can be rapidly converted to kinetic energy, that a spine can augment the effective workspace of the legs without diminishing their force generation capability, and that -- in cases of direct-drive or nearly direct-drive leg actuation -- the spine motors can contribute more work in stance than the same actuator weight used in the legs, but can do so without diminishing the platform\u27s proprioceptive capabilities. To put to use the agility provided by a suitably designed robotic platform, we introduce a formalism to approximate a set of transitional navigational tasks over irregular terrain such as leaping over a gap that lend itself to doubly reactive control synthesis. We also directly address the increased complexity introduced by the spine joint with a modular compositional control framework with nice stability properties that begins to offer insight into the role of spines for steady-state running. A central theme to both the reactive navigation and the modular control frameworks is that analytical tractability is achieved by approximating the modes driving the environmental interactions with constant-acceleration dynamics

What is Robotics: Why Do We Need It and How Can We Get It?

Robotics is an emerging synthetic science concerned with programming work. Robot technologies are quickly advancing beyond the insights of the existing science. More secure intellectual foundations will be required to achieve better, more reliable and safer capabilities as their penetration into society deepens. Presently missing foundations include the identification of fundamental physical limits, the development of new dynamical systems theory and the invention of physically grounded programming languages. The new discipline needs a departmental home in the universities which it can justify both intellectually and by its capacity to attract new diverse populations inspired by the age old human fascination with robots. For more information: Kod*la

Climbing and Walking Robots

Nowadays robotics is one of the most dynamic fields of scientific researches. The shift of robotics researches from manufacturing to services applications is clear. During the last decades interest in studying climbing and walking robots has been increased. This increasing interest has been in many areas that most important ones of them are: mechanics, electronics, medical engineering, cybernetics, controls, and computers. Today’s climbing and walking robots are a combination of manipulative, perceptive, communicative, and cognitive abilities and they are capable of performing many tasks in industrial and non- industrial environments. Surveillance, planetary exploration, emergence rescue operations, reconnaissance, petrochemical applications, construction, entertainment, personal services, intervention in severe environments, transportation, medical and etc are some applications from a very diverse application fields of climbing and walking robots. By great progress in this area of robotics it is anticipated that next generation climbing and walking robots will enhance lives and will change the way the human works, thinks and makes decisions. This book presents the state of the art achievments, recent developments, applications and future challenges of climbing and walking robots. These are presented in 24 chapters by authors throughtot the world The book serves as a reference especially for the researchers who are interested in mobile robots. It also is useful for industrial engineers and graduate students in advanced study

System Design, Motion Modelling and Planning for a Recon figurable Wheeled Mobile Robot

Over the past ve decades the use of mobile robotic rovers to perform in-situ scienti c investigations on the surfaces of the Moon and Mars has been tremendously in uential in shaping our understanding of these extraterrestrial environments. As robotic missions have evolved there has been a greater desire to explore more unstructured terrain. This has exposed mobility limitations with conventional rover designs such as getting stuck in soft soil or simply not being able to access rugged terrain. Increased mobility and terrain traversability are key requirements when considering designs for next generation planetary rovers. Coupled with these requirements is the need to autonomously navigate unstructured terrain by taking full advantage of increased mobility. To address these issues, a high degree-of-freedom recon gurable platform that is capable of energy intensive legged locomotion in obstacle-rich terrain as well as wheeled locomotion in benign terrain is proposed. The complexities of the planning task that considers the high degree-of-freedom state space of this platform are considerable. A variant of asymptotically optimal sampling-based planners that exploits the presence of dominant sub-spaces within a recon gurable mobile robot's kinematic structure is proposed to increase path quality and ensure platform safety. The contributions of this thesis include: the design and implementation of a highly mobile planetary analogue rover; motion modelling of the platform to enable novel locomotion modes, along with experimental validation of each of these capabilities; the sampling-based HBFMT* planner that hierarchically considers sub-spaces to better guide search of the complete state space; and experimental validation of the planner with the physical platform that demonstrates how the planner exploits the robot's capabilities to uidly transition between various physical geometric con gurations and wheeled/legged locomotion modes