A hexapod walking machine with decoupled freedoms
01 Dec 1985-Vol. 1, Iss: 4, pp 183-190
TL;DR: A hexapod walking machine using an approximate straight line mechanism was developed and several basic experiments were performed to demonstrate the properties of this type of walking machine.
Abstract: Legged locomotion over irregular terrain is composed of body-propelling motion and terrain-adapting motion. Although conventional walking machines with three degrees-of-freedom for each leg can adapt their feet on irregular ground using flexible leg freedom, such machines generally require a tremendously complex control scheme for the body-propelling motion. A walking machine with decoupled freedoms is based on the idea that body-propelling motion is realized by only one degree-of-freedom, and this freedom can be perfectly decoupled from the freedoms for terrain adaptability. As an application of such a walking machine, a hexapod walking machine using an approximate straight line mechanism was developed and several basic experiments were performed to demonstrate the properties of this type of walking machine.
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TL;DR: The mass-specific mechanical energy used to move the center of mass a given distance was similar to that measured for animals five orders of magnitude larger in mass, but was only one-hundredth of the metabolic cost.
Abstract: To examine the effects of variation in body form on the mechanics of terrestrial locomotion, we used a miniature force platform to measure the ground reaction forces of the smallest and, relative to its mass, one of the fastest invertebrates ever studied, the American cockroach Periplaneta americana (mass = 0.83 g). From 0.44-1.0 ms-1, P. americana used an alternating tripod stepping pattern. Fluctuations in gravitational potential energy and horizontal kinetic energy of the center of mass were nearly in phase, characteristic of a running or bouncing gait. Aerial phases were observed as vertical ground reaction force approached zero at speeds above 1 ms-1. At the highest speeds (1.0-1.5 ms-1 or 50 body lengths per second), P. americana switched to quadrupedal and bipedal running. Stride frequency approached the wing beat frequencies used during flight (27 Hz). High speeds were attained by increasing stride length, whereas stride frequency showed little increase with speed. The mechanical power used to accelerate the center of mass increased curvilinearly with speed. The mass-specific mechanical energy used to move the center of mass a given distance was similar to that measured for animals five orders of magnitude larger in mass, but was only one-hundredth of the metabolic cost.
389 citations
Additional excerpts
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01 Jan 1979
TL;DR: In this article, 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.
Abstract: 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.
378 citations
TL;DR: Different vehicle configurations as well as leg mechanisms which are already explored by researchers are reviewed and the author hopes that this will serve as a brief account of previous research efforts and help future walking robot designers to develop more sophisticated machines.
Abstract: The superior mobility characteristics of legged animals compared to those of wheeled or tracked vehicles for off-road locomotion motivated the development of artificial walking machines. The sustained worldwide efforts for the last few decades resulted in a large number of legged robots with different levels of sophistication. Here, various design approaches made so far to realize artificial legged locomotion are discussed. Mainly, different vehicle configurations as well as leg mechanisms which are already explored by researchers are reviewed in brief. The author hopes that this will serve as a brief account of previous research efforts and help future walking robot designers to develop more sophisticated machines. © 2003 Wiley Periodicals, Inc.
76 citations
01 Mar 2010
TL;DR: The most studied problem for multi-legged robots concerns how to determine the best sequence for lifting off and placing the feet (gait/locomotion planning).
Abstract: Multi-legged robots display significant advantages with respect to wheeled ones for walking over rough terrain because they do not need continuous contact with the ground. In Multi-legged robots, hexapod robots, mechanical vehicles that walk on six legs, have attracted considerable attention in recent decades. There are several benefits for hexapods rover. (a) Hexapod robot is easy to maintain static stability on three or more legs, (b) It has a great deal of flexibility in how it can move. (c) Hexapod robot is the most efficient one for statically stable walking. Preumount et al. 1991, observed that a larger number of legs more than six do not increase walking speed. (d) Hexapod robots show robustness in case of leg faults (e) Hexapods makes it possible for the robot to use one, two or three legs to work as hand and perform complex operations. The most studied problem for multi-legged robots concerns how to determine the best sequence for lifting off and placing the feet (gait/locomotion planning). From the stability point of view, robot locomotion can be classified into dynamic locomotion, such as running and hopping, and statically stable locomotion as walking. Statically stable locomotion has the constraint that the moving body is stable at all times. The vertical projection of the centre of gravity of the robot must be within the convex of the supporting polygon linked positions of all supporting feet. Statically stable gait is solely dependent on the design of bodies and legs. Hexapod gaits have been widely investigated as a function of shape and characteristics of the robot structure. In 1985, Kaneko et al. addressed the gait of a rectangular hexapod with decoupled freedoms where the propelling motion was generated by one degree of freedom (DOF). In 1988, Lee et al. realized an omnidirectional walking control system for a rectangular hexapod robot with adaptive suspension. A circular gait was studied for a layered hexapod robot (called Ambler) at the Carnegie Mellon University [Bares et al., 1989; Krotkov & Bares, 1991; Wettergreen, 1990] with rotating legs connected to the same vertical axis at six different heights. Hirose et al. in 1992 and 1998 and Gurocak in 1998 developed other two hexapods whose bodies were consisting of two different layers, each connected to three legs. The relative motion of the layers realized the omnidirectional robot gait in a simple way, but limiting the walking capability under leg faults. Two Lees in 2001 studied the gait of a special robot whose body was composed of three parts connected by revolute joints. Its 18
67 citations
TL;DR: A robot kinematics that considers at the same time supporting and transferring legs to optimize walking ability and energy management is introduced and the advantages of hexagonal hexapod robots over rectangular ones are shown.
Abstract: In recent years hexagonal hexapod robots gained the interest of international research community. The aim of this paper is twofold. First, after summarizing all known gaits of such robots, we introduce some improvements both for normal conditions and for fault tolerance. Then we show the advantages of hexagonal hexapod robots over rectangular ones by comparing different gaits from theoretical and experimental points of view. Stability, fault tolerance, turning ability, and terrain adaptability are analyzed. For reaching these aims we also introduce a robot kinematics that considers at the same time supporting and transferring legs. The trajectories of feet are described as well. Finally, single leg stride selection is studied for side wave and for kick-off gaits to optimize walking ability and energy management.
The theoretical results presented herein have been validated with experiments conducted on a prototype of the Novel Robotics System for Planetary Exploration (Rovetta et al., “New Robot Concepts for Mars Soil Exploration: Mechanics and Functionality,” ASTRA 2004, Eighth ESA Workshop on Advanced Space Technologies for Robotics and Automatian, Nordwijk, The Netherlands Nov. 2–4, 2004) (NOROS), developed by Politecnico di Milano and Beijing University of Astronautics and Aeronautics, and the results are summarized in this paper.
53 citations
References
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TL;DR: It is thus shown that a practical walking vehicle can be designed using the proposed method, and an algorithm for terrain-adaptive gait control is shown to be applicable for the control of future quadruped walking vehicles with visual sensors.
Abstract: The paper addresses some of the fundamental problems of energy efficiency, design, and adaptive gait control of quadru ped walking vehicles. The design principle of a leg called a gravitationally decoupled actuator (GDA) is shown to be indispensable for realizing energetically efficient walking mo tion. A novel mechanism, the three-dimensional Cartesian- coordinate pantograph (PANTOMEC), which follows the GDA principle and has a lightweight structure, is introduced. A constructed quadruped walking vehicle model is then de scribed : the walking vehicle has the PANTOMEC leg mecha nisms, eight tactile sensors and a posture detector, and is hierarchically controlled by a microcomputer. Comparatively high energy efficiency and a certain degree of terrain adapt ability is demonstrated. It is thus shown that a practical walking vehicle can be designed using the proposed method.The adaptive gait control problem is formalized, and an algorithm for terrain-adaptive gait control is presented. By computer simulation,...
387 citations
01 Jan 1979
TL;DR: In this article, 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.
Abstract: 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.
378 citations
01 Apr 1979
TL;DR: This paper is concerned with an extension of the present theory of limb coordination for adaptive walking 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.
Abstract: 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.
365 citations
TL;DR: In this article, the adaptive suspension vehicle (ASV) is presented as a proof-of-concept prototype of a proposed class of transportation vehicles for use in terrain that is not passable for conventional vehicles.
Abstract: The selection of vehicle and leg configuration and of power transmission and actuation system configuration for the adaptive suspension vehicle (ASV) are discussed. The ASV will be a proof-of-concept prototype of a proposed class of transportation vehicles for use in terrain that is not passable for conventional vehicles. It uses a legged locomotion princi ple. The machine will not be an autonomous "robot, " in the sense that it will carry an operator. It will, however, have a very high level of machine intelligence and environmental sensing capability. Much of the technology involved is unique and has potential for application to future robot systems. In this paper, major aspects of the vehicle and leg geometry, the on-board processing configuration, and the hydrostatic power transmission system are discussed.
192 citations
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TL;DR: In this paper, the authors explore the notion that the control of dynamically stable legged systems that locomote in 3-space can be decomposed into a planar part and an extra-planar part.
Abstract: This paper explores the notion that the control of dynamically stable legged systems that locomote in 3-space can be decomposed into a planar part and an extra-planar part. The planar part generates the large leg and body motions that raise and lower the legs to achieve stepping, that propel the system forward, and that maintain balance. The planar part of the control system deals only with 2D dynamics. The extra-planar part of the locomotion control system suppresses motion in those degrees of freedom that would cause deviation from the plane of motion. These degrees of freedom include roll of the body, yaw of the body, and translation perpendicular to the intended direction of travel.
149 citations