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Chapter 50 — Modeling and Control of Robots on Rough Terrain

Keiji Nagatani, Genya Ishigami and Yoshito Okada

In this chapter, we introduce modeling and control for wheeled mobile robots and tracked vehicles. The target environment is rough terrains, which includes both deformable soil and heaps of rubble. Therefore, the topics are roughly divided into two categories, wheeled robots on deformable soil and tracked vehicles on heaps of rubble.

After providing an overview of this area in Sect. 50.1, a modeling method of wheeled robots on a deformable terrain is introduced in Sect. 50.2. It is based on terramechanics, which is the study focusing on the mechanical properties of natural rough terrain and its response to off-road vehicle, specifically the interaction between wheel/track and soil. In Sect. 50.3, the control of wheeled robots is introduced. A wheeled robot often experiences wheel slippage as well as its sideslip while traversing rough terrain. Therefore, the basic approach in this section is to compensate the slip via steering and driving maneuvers. In the case of navigation on heaps of rubble, tracked vehicles have much advantage. To improve traversability in such challenging environments, some tracked vehicles are equipped with subtracks, and one kinematical modeling method of tracked vehicle on rough terrain is introduced in Sect. 50.4. In addition, stability analysis of such vehicles is introduced in Sect. 50.5. Based on such kinematical model and stability analysis, a sensor-based control of tracked vehicle on rough terrain is introduced in Sect. 50.6. Sect. 50.7 summarizes this chapter.

Mobility prediction of rovers on soft terrain

Author  Daniel Holz, Ali Azimi, Marek Teichmann, Jozsef Kavecses

Video ID : 184

This video is an animated dynamic simulation of a vehicle traveling on sandy terrain. The simulator carefully considers mechanical interactions based on relationships between the wheel and the terrain and between the tool and the terrain. In particular, a discrete-element method is employed in order to represent the tool-sand interactions.

Experiments of wheeled rovers in a sandbox covered with loose soil

Author  Field Robotics Group, Tohoku University

Video ID : 185

The lunar and Martian surfaces are covered with loose soil, and the wheels of rovers can get stuck on such surfaces. To avoid the problem, it is necessary to conduct thorough investigations into the contact and traction mechanics between the wheels and the soil. To this end, we conduct various experiments using wheeled rovers in a sandbox covered with loose soil. In the experiments, the slippage and sinkage of wheels with various geometries are measured. Based on these experimental observations, analysis and modelling of the motion behavior of wheels ensued.

Terradynamics of legged locomotion for traversal in granular media

Author  Chen Li, Tingnan Zhang, Daniel Goldman

Video ID : 186

The experiments in this video evaluate the effect of leg shape on the robot's dynamic behavior on soft sand. Several types of leg shapes have been tested, e.g., from linear shapes to arcs, with varying curvatures.

Interactive, human-robot supervision test with the long-range science rover for Mars exploration

Author  Samad Hayati, Richard Volpe, Paul Backes, J. (Bob) Balaram, Richard Welch, Robert Ivlev, Gregory Tharp, Steve Peters, Tim Ohm, Richard Petras

Video ID : 187

This video records a demonstration of the long-range rover mission on the surface of Mars. The Mars rover, the test bed Rocky 7, performs several demonstrations including 3-D terrain mapping using the panoramic camera, telescience over the internet, an autonomous mobility test, and soil sampling. This demonstration was among the preliminary tests for the Mars Pathfinder mission executed in 1997.

A path-following control scheme for a four-wheeled mobile robot

Author  Genya Ishigami, Keiji Nagatani, Kazuya Yoshida

Video ID : 188

This video shows a feedback control for planetary rovers. It calculates both steering and driving maneuvers that can compensate for wheel slips and also enable the rover to successfully traverse a sandy slope. The performance was confirmed in slope traversal experiments using a four-wheeled rover test bed. In this split video clip, no slip control is performed on the left, and slip-compensation-feedback control is conducted on the right. The rover's motion is detected by the visual odometry system using a telecentric camera.

Qualification testing of a tracked vehicle in the NIST Disaster City

Author  SuperDroid Robots, Inc

Video ID : 189

NIST (National Institute of Standards and Technology) developed a standard test field for evaluation of all-terrain mobile robots, called Disaster City in Texas, U.S.A. The field includes steps, stairs, steep slopes, and random step fields (unfixed wooden blocks), which simulates a disaster environment. This video-clip shows an evaluation test of the tracked vehicle, called LT-F, produced by SuperDroidRobots in 2011 in the Disaster City. All tests had to be performed remotely by the vehicle for 10 successful iterations each to qualify.

Autonomous sub-tracks control

Author  Field Robotics Group, Tohoku University

Video ID : 190

Field Robotics Group, Tohoku University, developed an autonomous controller for the tracked vehicle (Kenaf) to generate terrain-reflective motions of the sub-tracks. Terrain information is obtained using laser range sensors that are located on both sides of the Kenaf. The videoclip shows the basic function of the controller in a simple environment.

Autonomous sub-tracks control 2

Author  Field Robotics Group, Tohoku University

Video ID : 191

Field robotics group (Tohoku University) developed an autonomous controller for the tracked vehicle (Quince) to generate terrain-reflective motions by the sub-tracks. Terrain information is obtained using laser range sensors that are located on both sides of the Quince. Using this system, operators only have to specify a direction for the robot, following which the robot traverses rough terrain using autonomous sub-track motions.