Mobile Hexapod for Remote Inspection and Object Manipulation

An important envisaged application of legged robots is the exploration and mapping of extreme environments with an unknown terrain. These include areas where a wheeled robot may not be able to access due to the presence of obstacles, steps, etc. Moreover, within these environments, a legged robot may come across challenging spaces to access, such as narrow pathways and areas with large holes or obstacles. Corin is a hexapod designed at the University of Manchester to be able to perform advanced motions that would allow it to navigate through such terrains. In this context, advanced motions refer to the use of surfaces perpendicular to the ground plane for robot foot placement. Currently, two types of advanced motions have been considered: wall walking and chimney walking.

Wall walking

Chimney walking

The proposed aim of the research is the development of a hexapod that can autonomously navigate a complex unknown terrain, making use of advanced motions and building a 3D map of the environment before returning to its base position. Currently, the built platform has been tested during wall walking and while holding a static chimney pose between two walls. It can be easily imagined that while performing these advanced motions, the hexapod could encounter corners in the adjacent walls. Hence, a body of work was dedicated to studying the motion planning of such scenarios in simulation. Snapshots of two of these cornering scenarios are shown in the image to the left.

Implementing these advanced motions requires accurate knowledge of the position and orientation of the robot's body. A state estimator for the robot’s pose has been implemented based on an extended Kalman filter (EKF) while wall walking. The results were validated against measurements performed using a VICON motion capture system. The algorithm fuses measurements from the inertial measurement unit (IMU) on board the hexapod with leg kinematic measurements obtained using the joint encoders.

The successful implementation of the state estimator on Corin is the first step towards performing advanced motions autonomously. The next step involves using an on-board RGBD camera for localisation and for 3D mapping of the environment. This data can then be input into a motion planning algorithm which would allow the robot to transition between various walking routines, bringing it closer to being able to navigate a complex unknown terrain.

This video shows a simulation of the Corin hexapod traversing through challenging scenarios, supplementary of the paper accepted at TAROS 2019. The use of advanced motions, namely wall and chimney walking, allows the robot to navigate through areas previously deemed inaccessible. Utilizing such motions increase the use case of hexapods in remote inspection applications.

The video presents CORIN, a hexapod designed for research on advanced motions that utilises walls to support the motion of the robot. The robot has high motion freedom on the ground, as seen in the early parts of the video. In our research, these motions are being extended to scenarios where the robot utilises walls to support its motion as seen in the latter parts of the video. The capability to execute such motions extend the use cases of hexapods to challenging spaces such as narrow pathways and areas with large holes and obstacles.

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