Piezoelectric force sensors for hexapod transportation platform

Rough terrain is one of the major issues for transporting various objects to different remote locations. Wheeled platforms or robots are not suitable for such tasks due to a lack of ground clearance. Walking robots, despite their slower speed, can be successfully used as transportation platforms that can overcome the environment. However, leg placing requires accurate supervision and the force sensing system must be developed on each foot to acquire equal force distribution between legs and to obtain stable motion over the irregular surface. In this paper, we investigate the improvement of the hexapod robot’s feet by upgrading them with piezoelectric force sensors. By monitoring force dependence on transferred legs, we establish the most suitable hexapod gait for moving over the even surface

Legged locomotion over irregular terrains: State of the art of human and robot performance

Legged robotic technologies have moved out of the lab to operate in real environments, characterized by a wide variety of unpredictable irregularities and disturbances, all this in close proximity with humans. Demonstrating the ability of current robots to move robustly and reliably in these conditions is becoming essential to prove their safe operation. Here, we report an in-depth literature review aimed at verifying the existence of common or agreed protocols and metrics to test the performance of legged system in realistic environments. We primarily focused on three types of robotic technologies, i.e., hexapods, quadrupeds and bipeds. We also included a comprehensive overview on human locomotion studies, being it often considered the gold standard for performance, and one of the most important sources of bioinspiration for legged machines. We discovered that very few papers have rigorously studied robotic locomotion under irregular terrain conditions. On the contrary, numerous studies have addressed this problem on human gait, being nonetheless of highly heterogeneous nature in terms of experimental design. This lack of agreed methodology makes it challenging for the community to properly assess, compare and predict the performance of existing legged systems in real environments. On the one hand, this work provides a library of methods, metrics and experimental protocols, with a critical analysis on the limitations of the current approaches and future promising directions. On the other hand, it demonstrates the existence of an important lack of benchmarks in the literature, and the possibility of bridging different disciplines, e.g., the human and robotic, towards the definition of standardized procedure that will boost not only the scientific development of better bioinspired solutions, but also their market uptake

Quadruped Robot with Inside Diagnostics

Cílem této práce je navrhnout čtyřnohý robot inspirovaný bioorganismy a vybavit jej senzory a výpočty pro vnitřní diagnostiku systému. Práce se zabývá konstrukčním návrhem mechanismu, kde většina konstruovaných dílů je určena pro výrobu na 3D tiskárně. Dále se zabývá specifikací hardwarových komponentů. Pro použitý mikrokontroler byla vyrobena rozšiřující deska plošných spojů pro připojení servomotorů. Senzorický subsystém robotu obsahuje detekci doteků noh, měření proudu, napětí akumulátoru a úhlů natočení těla robotu pomocí IMU. Práce popisuje tvorbu programů na PC a v robotu, použitou strukturu kódu a použité algoritmy. Robot komunikuje pomocí vlastního sériového protokolu. V robotu probíhají výpočty generování pohybu, inverzní kinematiky, polohy těžiště a detekce kolizí. Pro robot byl vytvořen simulační model v programu V-Rep, na kterém byly testovány použité algoritmy.The goal of this thesis is to design a quadruped robot inspired by bioorganisms and equip it with internal sensors. The thesis deals with mechanical design of the robot, where the majority of parts is designed for 3D printing. The thesis also deals with hardware specifications. An additional PCB has been manufactured to expand the capabilities of the used microcontroller. The sensory subsystem consists of foothold detection, current and voltage measurements and orientation detection using an IMU. The thesis describes development of the software for PC and the robot, used code structure and algorithms. The robot communicates using a custom serial protocol. Movement generation, inverse kinematics, center of gravity position and collision detection are all being calculated onboard the robot. A simulation model has been built in V-Rep, on which the used algorithms were tested.354 - Katedra robotikyvýborn

Development of a Quadruped Robot and Parameterized Stair-Climbing Behavior

Stair-climbing is a difficult task for mobile robots to accomplish, particularly for legged robots. While quadruped robots have previously demonstrated the ability to climb stairs, none have so far been capable of climbing stairs of variable height while carrying all required sensors, controllers, and power sources on-board. The goal of this thesis was the development of a self-contained quadruped robot capable of detecting, classifying, and climbing stairs of any height within a specified range. The design process for this robot is described, including the development of the joint, leg, and body configuration, the design and selection of components, and both dynamic and finite element analyses performed to verify the design. A parameterized stair-climbing gait is then developed, which is adaptable to any stair height of known width and height. This behavior is then implemented on the previously discussed quadruped robot, which then demonstrates the capability to climb three different stair variations with no configuration change

Modeling, system identication, and control for dynamic locomotion of the LittleDog robot on rough terrain

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 76-80).In this thesis, I present a framework for achieving a stable bounding gait on the LittleDog robot over rough terrain. The framework relies on an accurate planar model of the dynamics, which I assembled from a model of the motors, a rigid body model, and a novel physically-inspired ground interaction model, and then identied using a series of physical measurements and experiments. I then used the RG-RRT algorithm on the model to generate bounding trajectories of LittleDog over a number of sets of rough terrain in simulation. Despite signicant research in the field, there has been little success in combining motion planning and feedback control for a problem that is as kinematically and dynamically challenging as LittleDog. I have constructed a controller based on transverse linearization and used it to stabilize the planned LittleDog trajectories in simulation. The resulting controller reliably stabilized the planned bounding motions and was relatively robust to signicant amounts of time delays in estimation, process and estimation noise, as well as small model errors. In order to estimate the state of the system in real time, I modified the EKF algorithm to compensate for varying delays between the sensors. The EKF-based filter works reasonably well, but when combined with feedback control, simulated delays, and the model it produces unstable behavior, which I was not able to correct. However, the close loop simulation closely resembles the behavior of the control and estimation on the real robot, including the failure modes, which suggests that improving the feedback loop might result in bounding on the real LittleDog. The control framework and many of the methods developed in this thesis are applicable to other walking systems, particularly when operating in the underactuated regime.by Michael Yurievich Levashov.S.M

QUADRUPEDAL WALKING GAIT GENERATION USING GENETIC ALGORITHM.

Ph.DDOCTOR OF PHILOSOPH

A Stability-Estimator to Unify Humanoid Locomotion: Walking, Stair-Climbing and Ladder-Climbing

The field of Humanoid robotics research has often struggled to find a unique niche that is not better served by other forms of robot. Unlike more traditional industrials robots with a specific purpose, a humanoid robot is not necessarily optimized for any particular task, due to the complexity and balance issues of being bipedal. However, the versatility of a humanoid robot may be ideal for applications such as search and rescue. Disaster sites with chemical, biological, or radiation contamination mean that human rescue workers may face untenable risk. Using a humanoid robot in these dangerous circumstances could make emergency response faster and save human lives. Despite the many successes of existing mobile robots in search and rescue, stair and ladder climbing remains a challenging task due to their form. To execute ladder climbing motions effectively, a humanoid robot requires a reliable estimate of stability. Traditional methods such as Zero Moment Point are not applicable to vertical climbing, and do not account for force limits imposed on end-effectors. This dissertation implements a simple contact wrench space method using a linear combination of contact wrenches. Experiments in simulation showed ZMP equivalence on flat ground. Furthermore, the estimator was able to predict stability with four point contact on a vertical ladder. Finally, an extension of the presented method is proposed based on these findings to address the limitations of the linear combination.Ph.D., Mechanical Engineering and Mechanics -- Drexel University, 201

Design, analysis and passive balance control of a 7-DOF biped robot

Biped robots have many advantages than traditional wheeled or tracked robots. They have better mobility in rough terrain and can travel on discontinuous path. The legs can also provide an active suspension that decouples the path of the trunk from the paths of the feet. Furthermore, the legs are able to step over considerably bigger obstacles compared to wheeled robots. However, it is difficult to maintain the balance of biped robots because they can easily tip over or slide down. To be able to walk stably, it is necessary for the robot to walk through a proper trajectory, which is the goal of this research. In this research, a complete 7-DOF biped walking trajectory is planned based on human walking trajectory by cubic Hermite interpolation method. The kinematics and dynamic model of the biped are derived by Denavit-Hartenberg (D-H) representation and Euler-Lagrange motion equations, respectively. The zero moment point of the robot is simulated to check the stability of the walking trajectory. The setpoint sampling method and sampling rate for trajectory tracking control are investigated by studying sinusoidal curve tracking on a single link robot arm. Two control sampling time selection methods are introduced for digital controllers. A 7-DOF biped is designed and built for experiments. Each joint has its own independent microcontroller-based control system. PD controllers are used to control the biped joints. Simulations are performed for the walking trajectory and zero moment point. Simulation results show that the walking trajectory is stable for the 7-DOF biped. Experiment results indicate that the sampling time is proper and the PID controller works well in both setpoint control and trajectory tracking. The experiment for the marching in place shows the trajectory is stable and the biped can balance during the marching process