Non-Periodic Gait Planning Based on Salient Region Detection for a Planetary Cave Exploration Robot

A limbed climbing robot can traverse uneven and steep terrain, such as Lunar/Martian caves. Towards the autonomous operation of the robot, we first present a method to detect topographically salient regions in 3D point cloud as the robot ’s graspable targets, and next, we introduce a strategy to plan a non-periodic gait for the robot from the detected discrete graspable options. The proposed gait planner is implemented and validated in our open dynamic climbing robot simulation platform assuming the 3 kg class four-limbed climbing robot testbed moving over steep and uneven Lunar terrain.International Symposium on Artificial Intelligence, Robotics and Automation in Space (i-SAIRAS 2020), October 19-23, 2020, Los Angles, CA, USA（新型コロナ感染拡大に伴い、オンライン開催に変更

Trends in the control of hexapod robots: a survey

The static stability of hexapods motivates their design for tasks in which stable locomotion is required, such as navigation across complex environments. This task is of high interest due to the possibility of replacing human beings in exploration, surveillance and rescue missions. For this application, the control system must adapt the actuation of the limbs according to their surroundings to ensure that the hexapod does not tumble during locomotion. The most traditional approach considers their limbs as robotic manipulators and relies on mechanical models to actuate them. However, the increasing interest in model-free models for the control of these systems has led to the design of novel solutions. Through a systematic literature review, this paper intends to overview the trends in this field of research and determine in which stage the design of autonomous and adaptable controllers for hexapods is.The first author received funding through a doctoral scholarship from the Portuguese Foundation for Science and Technology (FCT) (Grant No. SFRH/BD/145818/2019), with funds from the Portuguese Ministry of Science, Technology and Higher Education and the European Social Fund through the Programa Operacional Regional Norte. This work has been supported by the FCT national funds, under the national support to R&D units grant, through the reference project UIDB/04436/2020 and UIDP/04436/2020

Analytical Workspace, Kinematics, and Foot Force Based Stability of Hexapod Walking Robots

Many environments are inaccessible or hazardous for humans. Remaining debris after earthquake and fire, ship hulls, bridge installations, and oil rigs are some examples. For these environments, major effort is being placed into replacing humans with robots for manipulation purposes such as search and rescue, inspection, repair, and maintenance. Mobility, manipulability, and stability are the basic needs for a robot to traverse, maneuver, and manipulate in such irregular and highly obstructed terrain. Hexapod walking robots are as a salient solution because of their extra degrees of mobility, compared to mobile wheeled robots. However, it is essential for any multi-legged walking robot to maintain its stability over the terrain or under external stimuli. For manipulation purposes, the robot must also have a sufficient workspace to satisfy the required manipulability. Therefore, analysis of both workspace and stability becomes very important. An accurate and concise inverse kinematic solution for multi-legged robots is developed and validated. The closed-form solution of lateral and spatial reachable workspace of axially symmetric hexapod walking robots are derived and validated through simulation which aid in the design and optimization of the robot parameters and workspace. To control the stability of the robot, a novel stability margin based on the normal contact forces of the robot is developed and then modified to account for the geometrical and physical attributes of the robot. The margin and its modified version are validated by comparison with a widely known stability criterion through simulated and physical experiments. A control scheme is developed to integrate the workspace and stability of multi-legged walking robots resulting in a bio-inspired reactive control strategy which is validated experimentally

Design Issues for Hexapod Walking Robots

Hexapod walking robots have attracted considerable attention for several decades. Many studies have been carried out in research centers, universities and industries. However, only in the recent past have efficient walking machines been conceived, designed and built with performances that can be suitable for practical applications. This paper gives an overview of the state of the art on hexapod walking robots by referring both to the early design solutions and the most recent achievements. Careful attention is given to the main design issues and constraints that influence the technical feasibility and operation performance. A design procedure is outlined in order to systematically design a hexapod walking robot. In particular, the proposed design procedure takes into account the main features, such as mechanical structure and leg configuration, actuating and driving systems, payload, motion conditions, and walking gait. A case study is described in order to show the effectiveness and feasibility of the proposed design procedure

Hexapod robot stability research

El trabajo consiste en una primera parte en la que se estudia analíticamente la composición del robot hexápodo, descomponiéndolo en sus diferentes componentes físicos así como una introducción a la estabilidad del robot, tipos de estabilidad y métodos para su análisis.Grado en Ingeniería en Electrónica Industrial y Automátic

Dynamical Modelling and a Decentralized Adaptive Controller for a 12-Tetrahedral Rolling Robot

The 12-tetrahedral robot is an addressable reconfigurable technology (ART)-based variable geometry truss mechanism with twenty-six extensible struts and nine nodes arranged in a tetrahedral mesh. The robot has the capability of reconfiguring shape and dimension for environment sensing requirements, which makes it suitable for space exploration and environmental perception. In this paper, we have derived a dynamics model and presented a decentralized adaptive controller for a 12-tetrahedral robot. First, the robot is divided into the node and the strut subsystems, and the kinetic and the potential energy are calculated for the two subsystems. Then, the dynamics model is achieved by applying the Lagrangian formalism on the total energy of the robot. Since the dynamics is too complicated for implementing model-based controllers, a two-layer controller is presented to control the robot, in which the planning layer determines gait and trajectory of the robot, and the executive layer adopts the decentralized adaptive control strategy and consists of twenty-six strut controllers. Each strut controller regulates the movement of the corresponding strut without information exchange with other struts. Co-simulations based on ADAMS and Matlab have been conducted to verify the feasibility and effectiveness of the proposed controller

Reimagining Robotic Walkers For Real-World Outdoor Play Environments With Insights From Legged Robots: A Scoping Review

PURPOSE For children with mobility impairments, without cognitive delays, who want to participate in outdoor activities, existing assistive technology (AT) to support their needs is limited. In this review, we investigate the control and design of a selection of robotic walkers while exploring a selection of legged robots to develop solutions that address this gap in robotic AT. METHOD We performed a comprehensive literature search from four main databases: PubMed, Google Scholar, Scopus, and IEEE Xplore. The keywords used in the search were the following: “walker”, “rollator”, “smart walker”, “robotic walker”, “robotic rollator”. Studies were required to discuss the control or design of robotic walkers to be considered. A total of 159 papers were analyzed. RESULTS From the 159 papers, 127 were excluded since they failed to meet our inclusion criteria. The total number of papers analyzed included publications that utilized the same device, therefore we classified the remaining 32 studies into groups based on the type of robotic walker used. This paper reviewed 15 different types of robotic walkers. CONCLUSIONS The ability of many-legged robots to negotiate and transition between a range of unstructured substrates suggests several avenues of future consideration whose pursuit could benefit robotic AT, particularly regarding the present limitations of wheeled paediatric robotic walkers for children’s daily outside use. For more information: Kod*lab (link to kodlab.seas.upenn.edu

Design and development of a hominid robot with local control in its adaptable feet to enhance locomotion capabilities

With increasing mechanization of our daily lives, the expectations and demands in robotic systems increase in the general public and in scientists alike. In recent events such as the Deepwater Horizon''-accident or the nuclear disaster at Fukushima, mobile robotic systems were used, e.g., to support local task forces by gaining visual material to allow an analysis of the situation. Especially the Fukushima example shows that the robotic systems not only have to face a variety of different tasks during operation but also have to deal with different demands regarding the robot's mobility characteristics. To be able to cope with future requirements, it seems necessary to develop kinematically complex systems that feature several different operating modes. That is where this thesis comes in: A robotic system is developed, whose morphology is oriented on chimpanzees and which has the possibility due to its electro-mechanical structure and the degrees of freedom in its arms and legs to walk with different gaits in different postures. For the proposed robot, the chimpanzee was chosen as a model, since these animals show a multitude of different gaits in nature. A quadrupedal gait like crawl allows the robot to traverse safely and stable over rough terrain. A change into the humanoid, bipedal posture enables the robot to move in man-made environments. The structures, which are necessary to ensure an effective and stable locomotion in these two poses, e.g., the feet, are presented in more detail within the thesis. This includes the biological model and an abstraction to allow a technical implementation. In addition, biological spines are analyzed and the development of an active, artificial spine for the robotic system is described. These additional degrees of freedom can increase the robot's locomotion and manipulation capabilities and even allow to show movements, which are not possible without a spine. Unfortunately, the benefits of using an artificial spine in robotic systems are nowadays still neglected, due to the increased complexity of system design and control. To be able to control such a kinematically complex system, a multitude of sensors is installed within the robot's structures. By placing evaluation electronics close by, a local and decentralized preprocessing is realized. Due to this preprocessing is it possible to realize behaviors on the lowest level of robot control: in this thesis it is exemplarily demonstrated by a local controller in the robot's lower leg. In addition to the development and evaluation of robot's structures, the functionality of the overall system is analyzed in different environments. This includes the presentation of detailed data to show the advantages and disadvantages of the local controller. The robot can change its posture independently from a quadrupedal into a bipedal stance and the other way around without external assistance. Once the robot stands upright, it is to investigate to what extent the quadrupedal walking pattern and control structures (like the local controller) have to be modified to contribute to the bipedal walking as well

Consider the robot - Abstraction of bioinspired leg coordination and its application to a hexapod robot under consideration of technical constraints

Paskarbeit J. Consider the robot - Abstraction of bioinspired leg coordination and its application to a hexapod robot under consideration of technical constraints. Bielefeld: Universität Bielefeld; 2017.To emulate the movement agility and adaptiveness of stick insects in technical systems such as piezo actuators (Szufnarowski et al. 2014) or hexapod robots (Schneider, Cruse et al. 2006), a direct adaptation of bioinspired walking controllers like WALKNET has often been suggested. However, stick insects have very specific features such as adhesive foot pads that allow them to cling to the ground. Typically, robots do not possess such features. Besides, robots tend to be bigger and heavier than their biological models, usually possessing a different mass distribution as well. This leads to different mechanical and functional properties that need to be addressed in control. Based on the model of the stick insect *Carausius morosus*, the six-legged robot HECTOR was developed in this work to test and evaluate bioinspired controllers. The robot's geometrical layout corresponds to that of the stick insect, scaled up by a factor of 20. Moreover, like the stick insect, the robot features an inherent compliance in its joints. This compliance facilitates walking in uneven terrain since small irregularities can be compensated passively without controller intervention. However, the robot differs from the biological model, e.g., in terms of its size, mass, and mass distribution. Also, it does not possess any means to cling to the ground and therefore must maintain static stability to avoid tilting. To evaluate the ability of stick insects to maintain static stability, experimental data (published by Theunissen et al. (2014)) was examined. It can be shown that stick insects do not maintain static stability at all times. Still, due to their adhesive foot pads, they do not tumble. Therefore, a direct replication of the biological walking controller would not be suitable for the control of HECTOR. In a next step, the bioinspired walking controller WALKNET (Cruse, Kindermann, et al. 1998) was evaluated regarding its applicability for the control of HECTOR. For this purpose, different parametrizations of WALKNET were tested in a simulation environment. For forward walking, parameter sets were found that achieve a high, although not permanent stability. Thus, for the control of HECTOR, which requires continuous stability, a more abstract adaption of the bioinspired coordination had to be found. Based on the original coordination concepts of WALKNET, new coordination mechanisms were developed that incorporate the technical requirements (static stability, angular joint limits, torque constraints, etc.). The ability of the resulting controller to generate insect-like gaits is demonstrated for different walking scenarios in simulation. Moreover, locomotion that is unlikely for insects such as backwards and sidewards walking is shown to be feasible using the novel control approach. At the end of this work the applicability of the approach for the control of the real robot is proved in experiments on visual collision avoidance and basic climbing ability