Although the off-road mobility characteristics of wheeled or tracked vehicles are generally recognized as being inferior to those of man and cursorial animals, the complexity of the joint-coordination control problem has thus far frustrated attempts to achieve improved vehicular terrain adaptability through the application of legged locomotion concepts. Nevertheless, the evident superiority of biological systems in this regard has motivated a number of theoretical studies over the past decade which have now reached a state of maturity sufficient to permit the construction of experimental computer-controlled adaptive walking machines. At least two such vehicles are known to have recently demonstrated legged locomotion over smooth hard-surfaced terrain. This paper is concerned with an extension of the present theory of limb coordination for such machines to the case in which the terrain includes regions not suitable for weight-bearing and which must consequently be avoided by the control computer in deciding when and where to successively place the feet of the vehicle. The paper includes a complete problem formalization, a heuristic algorithm for solution of the problem thus posed, and a preliminary evaluation of the proposed algorithm in terms of a computer simulation study.

Adaptive Locomition of a Multilegged Robot over Rough Terrain

We present a controller for a quadrupedal robot statically walking on known rough terrain. The controller has both deliberative and reactive components for task specific control issues, such as impassable terrain and unmodeled foot slippage. The controller architecture supports multiple gaits, and we present both a stable omnidirectional gait and a faster directional gait. The robot successfully negotiates obstacles up to 7.5 cm (ap40% leg length) tall and navigates over rocky terrain.

/pdf/a-controller-for-the-littledog-quadruped-walking-on-rough-523a3f51r3.pdf

A Controller for the LittleDog Quadruped Walking on Rough Terrain

Other than from its sensing and processing capabilities, a mobile robotic platform can be limited in its use by its ability to move in the environment. Legs, tracks and wheels are all efficient means of ground locomotion that are most suitable in different situations. Legs allow to climb over obstacles and change the height of the robot, modifying its viewpoint of the world. Tracks are efficient on uneven terrains or on soft surfaces (snow, mud, etc.), while wheels are optimal on flat surfaces. Our objective is to work on a new concept capable of combining different locomotion mechanisms to increase the locomotion capabilities of the robotic platform. The design we came up with, called AZIMUT, is symmetrical and is made of four independent leg-track-wheel articulations. It can move with its articulations up, down or straight, allowing the robot to deal with three-dimensional environments. AZIMUT is also capable of moving sideways without changing its orientation, making it omnidirectional. By putting sensors on these articulations, the robot can also actively perceive its environment by changing the orientation of its articulations. Designing a robot with such capabilities requires addressing difficult design compromises, with measurable impacts seen only after integrating all of the components together. Modularity at the structural, hardware and embedded software levels, all considered concurrently in an iterative design process, reveals to be key in the design of sophisticated mobile robotic platforms.

Multi-Modal Locomotion Robotic Platform Using Leg-Track-Wheel Articulations

Robots that solve complex tasks in environments too dangerous for humans to enter are desperately needed, e.g., for search and rescue applications. We describe our mobile manipulation robot Momaro, with which we participated successfully in the DARPA Robotics Challenge. It features a unique locomotion design with four legs ending in steerable wheels, which allows it both to drive omnidirectionally and to step over obstacles or climb. Furthermore, we present advanced communication and teleoperation approaches, which include immersive three-dimensional 3D visualization, and 6D tracking of operator head and arm motions. The proposed system is evaluated in the DARPA Robotics Challenge, the DLR SpaceBot Cup Qualification, and lab experiments. We also discuss the lessons learned from the competitions.

NimbRo Rescue: Solving Disaster-response Tasks with the Mobile Manipulation Robot Momaro

For a mobile manipulator to be used in areas such as offices and houses, it is desirable that the mobile platform be small sized. In the case of a small-sized platform, the mobile manipulator may t...

Coordinated Motion Planning for a Mobile Manipulator considering Stability and Manipulation

Describes the mechanism and control of a leg-wheel hybrid mobile robot. Legged locomotion has high adaptability for rough terrain, and wheeled locomotion possesses speed and efficiency. A locomotion mechanism that combines legs and wheels is proposed, and a prototype mobile robot that adopts the mechanism is introduced. The robot has four legs, and a wheel is attached at the end of each leg. The front leg has three joints and a passive wheel. The rear leg has one joint and an active wheel. In order to make the best of the mechanism, three locomotion modes, wheel mode, hybrid mode, and step mode, are developed. In the wheel mode, four wheels are used on flat terrain. On rough terrain, the hybrid mode is selected, and two legs and two active wheels are used for locomotion. To climb or descend a large step, the step mode is used.

Mechanism and control of a leg-wheel hybrid mobile robot

This paper provides a new concept for the integration of locomotion and manipulation, "the integrated limb mechanism". The concept covers the technical fields both of the control integration and of the mechanism integration necessary for the practical working robot. Here, a six-bar linkage mechanism with four degrees-of-freedom is introduced as an example of the integrated limb mechanism with both advantages for leg sand for arms. Computer simulation with a dynamic model is performed to verify the transformability from leg posture into arm posture of this mechanism. The kinematic analysis is done for this mechanism, and it is suggested that the kinematic analysis is useful for the geometric and mechanical design. The possibility of dual arms or triple arm work is analyzed.

Hexapod with integrated limb mechanism of leg and arm

The concept of "limb mechanism" is proposed, consisting of several common link mechanisms which can be used for either arm or leg, selectively. Integrated kinematics is introduced for r legs and one arm mechanism. Based on the derived kinematics evaluation criteria are introduced in order to design the mechanism itself as well as a motion controller. Simulation results show how the proposed methods work effectively to analyze motion of the integrated mechanism.

Integrated arm and leg mechanism and its kinematic analysis

Describes dual mode control of walk and manipulation of a prototype hexapod with integrated limb mechanism, named MELMANTIS-1. MELMANTIS-1 uses six-bar linkages with four degrees-of-freedom as an integrated limb mechanism with dual use for a leg and for an arm. Omni-directional drive control is introduced to the hexapod walk with alternative tripod gait. The transformation from hexapod walking style into the combination of dual arms and quadruped platform is introduced. A remote control to handle an object by dual arms is experimented with in a simple application of a trash pitcher.

Hironori Adachi

Papers

Mechanism and control of a leg-wheel hybrid mobile robot

Hexapod with integrated limb mechanism of leg and arm

Integrated arm and leg mechanism and its kinematic analysis

Control of walk and manipulation by a hexapod with integrated limb mechanism: MELMANTIS-1

Integrated limb mechanism of manipulation and locomotion for dismantling robot-basic concept for control and mechanism