Locomotion In Unstructured Environments Research Articles

Amphibious Robots Locomotion Strategies in Unstructured Complex Environments: A Review

In the previous literature, amphibious robots focused mainly on locomotion in underwater and flat land surface manoeuvring. Few amphibious robots focused on unstructured land environments. The amphibious robot designs were more emphasised in academics, leading to more work done in building amphibious robots that mimic biological amphibians, imitating the geometry and overall functionality of the amphibious robots. Developing amphibious robots with propulsive mechanisms for manoeuvring in a water environment received more attention than other functionalities like adaptability on rough natural terrain and obstacle repositioning capability. However, practical applications like reconnaissance and surveying posed challenges in the ground environment, which had unstructured and complex terrain profiles, especially in the transition area. Therefore, reviewing the amphibious robots focused on manoeuvring complex uneven surfaces was essential. The literature had comprehensive review papers on navigation strategies encompassing manoeuvring on flat ground surfaces and underwater locomotion. There was a need for a focused study that highlighted the amphibious robot that manoeuvred in an unstructured land environment. The open challenges and recent solutions by designing new mechanisms and deployment issues were highlighted and reviewed. Hence, the paper addressed a more specific review of amphibious robot locomotion in an unstructured environment. The paper also discussed a case study of an amphibious robot capable of locomotion in unstructured environments. It was envisaged that the review would provide directions and insights to researchers and robotic system designers on developing robust propulsive mechanisms for amphibious robots capable of locomotion in unstructured environments.Keywords: manoeuvrability, mobility, terrain, unified locomotion, mechanism, propulsion

Hierarchical Free Gait Motion Planning for Hexapod Robots Using Deep Reinforcement Learning

This paper addresses the problem of legged locomotion in unstructured environments, and a novel Hierarchical multi-contact motion planning method for hexapod robots is proposed by combining Free Gait motion planning and Deep Reinforcement Learning (HFG-DRL). We structurally decompose the complex free gait multi-contact motion planning task into path planning in discrete state space and gait planning in continuous state space. Firstly, the Soft Deep Q-Network (SDQN) is used to obtain the global prior path information in the Path Planner (PP). Secondly, a Free Gait Planner (FGP) is proposed to obtain the gait sequence. Finally, based on the PP and the FGP, the Center-of-Mass (CoM) sequence is generated by the trained optimal policy using the designed Deep Reinforcement Learning (DRL) algorithm. Experimental results in different environments demonstrate the feasibility, effectiveness, and advancement of the proposed method. Videos are shown at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">http://www.hexapod.cn/hfg-drl.html</uri> .

TENG-Bot: Triboelectric nanogenerator powered soft robot made of uni-directional dielectric elastomer

Abstract A soft robot employing dielectric elastomer actuators (DEAs) exhibits a flexible body and dexterity locomotion in unstructured environments. However, conventional power supplies required by DEAs pose an obstacle for small-scale robotic system. Triboelectric nanogenerator (TENG) is capable of harvesting kinetic energy from the environment to generate matching power for DEA. Yet, a TENG-driven, DEA-based robot is hindered due to the nonlinear and insufficient mechanical transmission in robotic motion. In this paper, we developed an uni-directional DEA-driven soft robot. It aligns the direction of DEA in extension with the robot motion to achieve high efficient energy conversion, yielding a maximum crawling velocity of 110 mm (2.2 body-length) /sec and a payload capacity of 40 g. Then a TENG-Bot, that is a TENG-soft robot conjunction system, is built using a freestanding TENG. With the benefit from the simple structure, and the high efficiency of the robot, the electrical energy generated by the TENG can directly drive the robot without additional control panels. Experiments demonstrate a linear relationship between the sliding speed of the TENG and the velocity of the soft robot, a direct control correspondence. The TENG-Bot offers a route for developing self-powered soft robots by harvesting the environment motion.

Vision does not impact walking performance in Argentine ants.

Many walking insects use vision for long-distance navigation, but the influence of vision on rapid walking performance that requires close-range obstacle detection and directing the limbs towards stable footholds remains largely untested. We compared Argentine ant (Linepithema humile) workers in light versus darkness while traversing flat and uneven terrain. In darkness, ants reduced flat-ground walking speeds by only 5%. Similarly, the approach speed and time to cross a step obstacle were not significantly affected by lack of lighting. To determine whether tactile sensing might compensate for vision loss, we tracked antennal motion and observed shifts in spatiotemporal activity as a result of terrain structure but not illumination. Together, these findings suggest that vision does not impact walking performance in Argentine ant workers. Our results help contextualize eye variation across ants, including subterranean, nocturnal and eyeless species that walk in complete darkness. More broadly, our findings highlight the importance of integrating vision, proprioception and tactile sensing for robust locomotion in unstructured environments.

Electrically-latched compliant jumping mechanism based on a dielectric elastomer actuator

Jumping mechanisms are useful in robotics for locomotion in unstructured environments, or for self-righting abilities. However, most rigid robots rely on impact with the ground to jump, thereby requiring a relatively rigid, and flat environment. Moreover, they need to be able to absorb high impact forces during landing in order to maintain structural integrity. In this paper we investigate soft systems, capable of jumping repeatedly in unstructured environments with no need for precise landings. Our impulsive approach is based on a soft electro-mechanical transducer, a dielectric elastomer actuator (DEA). The design is inspired by click-beetles and simple bio-mechanical models, which convert the flexing around a hinge into jumping. Our actuator is power amplified by the addition of a stiffer strip, allowing for rapid shape transitions (22 ms) between flat and curved states. The transition is controlled by an electric latch: the DEA is discharged faster than the actuator can deform. The mechanical energy stored in the composite beam is released rapidly, leading to impulsive motions (jumps of a full body length: i.e. 5 cm). This demonstration of an electrically-latched power amplification mechanism shows that relatively simple electro-mechanical systems can exhibit impulsive behavior which may enable new types of locomotion in compliant machines.

Surface Detection and Classification for Point-Footed Bipedal Robotic Locomotion in Unstructured Environments Using Depth Visual Perception

Surface Detection and Classification for Point-Footed Bipedal Robotic Locomotion in Unstructured Environments Using Depth Visual Perception

Improving the Navigability of a Hexapod Robot Using a Fault-Tolerant Adaptive Gait

This paper encompasses a study on the development of a walking gait for fault tolerant locomotion in unstructured environments. The fault tolerant gait for adaptive locomotion fulfills stability conditions in opposition to a fault (locked joints or sensor failure) event preventing a robot to realize stable locomotion over uneven terrains. To accomplish this feat, a fault tolerant gait based on force-position control is proposed in this paper for a hexapod robot to enable stable walking with a joint failure. Furthermore, we extend our proposed fault detection and diagnosis (FDD) method to deal with the critical failure of the angular rate sensors responsible for the attitude control of the robot over uneven terrains. A performance analysis of straight-line walking is carried out which shows that the proposed FDD-based gait is capable of generating an adaptive walking pattern during joint or sensor failures. The performance of the proposed control is established using dynamic simulations and real-world experiments on a prototype hexapod robot.

Biomimetic flexible/compliant sensors for a soft-body lamprey-like robot

This paper focuses on the development of biomimetic sensory abilities for an undulatory soft-body lamprey-like robot, which has been designed to replicate the locomotion mechanisms of living lamprey in order to address useful applications wherever locomotion in unstructured environments is required. The compliant sensory elements are piezo-resistive and made from compliant material called a quantum tunneling composite by mixing micro/nano carbon black particles into a highly soft silicone rubber matrix. The relationship of the composite strip between piezo-resistivity and mechanical strain is investigated by a universal strain–stress tensiometer through resistivity monitoring. Increasing and decreasing resitivity both appears during elongation and retraction, suggesting that piezo-resistivity in the composite material is governed by both percolation theory and quantum tunneling effects. Dynamic tests on the bench shows that the compliant stretch receptor is able to follow the stimulations under fairly wide frequency ranges, exceeding initial estimations. In addition, the compliant artificial stretch receptor has enough sensitivity to detect the local actuations and the actions generated by neighboring actuators in the segmented robotic structure. Finally, the experiments on biomimetic cilia-based cupula receptor show that a low cost flexible/compliant biomimetic sensor is able to detect medium fluidic speeds ranging from 0.05 m/s to 0.6 m/s.

Two new design concepts for snake robot locomotion in unstructured environments

AbstractThis communication presents and justifies ideas related to motion control of snake robots that are currently the subject of ongoing investigations by the authors. In particular, we highlight requirements for intelligent and effcient snake robot locomotion in unstructured environments, and subsequently we present two new design concepts for snake robots that comply with these requirements. The first design concept is an approach for sensing environment contact forces, which is based on measuring the joint constraint forces at the connection between the links of the snake robot. The second design concept involves allowing the cylindrical surface of each link of a snake robot to rotate by a motor inside the link in order to induce propulsive forces on the robot from its environments. The paper details the advantages of the proposed design concepts over previous snake robot designs.