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Legged robots are an efficient alternative for navigation in challenging terrain. In this paper we describe Weaver, a six‐legged robot that is designed to perform autonomous navigation in unstructured terrain. It uses stereo vision and proprioceptive sensing based terrain perception for adaptive control while using visual‐inertial odometry for autonomous waypoint‐based navigation. Terrain perception generates a minimal representation of the traversed environment in terms of roughness and step height. This reduces the complexity of the terrain model significantly, enabling the robot to feed back information about the environment into its controller. Furthermore, we combine exteroceptive and proprioceptive sensing to enhance the terrain perception capabilities, especially in situations in which the stereo camera is not able to generate an accurate representation of the environment. The adaptation approach described also exploits the unique properties of legged robots by adapting the virtual stiffness, stride frequency, and stride height. Weaver's unique leg design with five joints per leg improves locomotion on high gradient slopes, and this novel configuration is further analyzed. Using these approaches, we present an experimental evaluation of this fully self‐contained hexapod performing autonomous navigation on a multiterrain testbed and in outdoor terrain.

Legged robots have the ability to adapt their walking posture to navigate confined spaces due to their high degrees of freedom. However, this has not been exploited in most common multilegged platforms. This paper presents a deformable bounding box abstraction of the robot model, with accompanying mapping and planning strategies, that enable a legged robot to autonomously change its body shape to navigate confined spaces. The mapping is achieved using robot-centric multielevation maps generated with distance sensors carried by the robot. The path planning is based on the trajectory optimisation algorithm CHOMP which creates smooth trajectories while avoiding obstacles. The proposed method has been tested in simulation and implemented on the hexapod robot Weaver, which is 33 cm tall and 82 cm wide when walking normally. We demonstrate navigating under 25 cm overhanging obstacles, through 70 cm wide gaps and over 22 cm high obstacles in both artificial testing spaces and realistic environments, including a subterranean mining tunnel.

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Legged robots offer a more versatile solution to traversing outdoor uneven terrain compared to their wheeled and tracked counterparts. They also provide a unique opportunity to perceive the terrain-robot interactions by listening to the sounds generated during locomotion. Legged robots such as hexapod robots produce rich acoustic information for each gait cycle which includes the foot fall sounds and feet pushing on the terrain (support phase), as well as the sounds produced when the feet travel through the air (stride phase). Interpreting this information to perceive the terrain it is traversing makes available another valuable sensing modality which can feed in to higher level systems to facilitate robust and efficient navigation through unknown terrain. We present an online realtime terrain classification system for legged robots that utilise features from the acoustic signals produced during locomotion. A 32-dimensional feature vector extracted from acoustic data recorded using an on-board microphone was fed in to a multiclass Support Vector Machine (SVM). The SVM was trained on 7 different terrain types and the results of the experimental evaluations are presented. The system was implemented using the Robotic Operating System (ROS) for real-time terrain classification. A classification time-resolution of 1 s was achieved by capturing acoustic signals of two steps, and the results show a true positive rate (sensitivity) of up to 92.9%. We also present a noise subtraction technique which removes servo noise and improves the sensitivity up to 95.1%.