Showing papers by "William Whittaker published in 1991"

Orthogonal legged walking robot

Abstract: The present invention pertains to a robot for moving along uneven terrain. The robot comprises a body having an opening through which a leg can pass. There is also a device for moving the body. The moving device includes at least 3 legs, at least one of which can exhibit an overlapping gait with respect to another leg. The robot is also comprised of a device for controlling the moving device such that the body moves along the terrain in a desired path. In an alternative embodiment, the moving device includes legs, each of which can exhibit an overlapping gait with respect to another leg while moving the body. In a preferred embodiment, each leg is comprised of a shoulder that is rotatable in a θ direction. Each leg is also comprised of a pedestal which has an axis that is disposed in essentially a z direction, where the z direction is perpendicular to the θ direction. There is also a device for linking the shoulder and the pedestal such that the pedestal can be moved in an r direction to a desired r position with respect to the shoulder, where the r direction is perpendicular to the z and the θ directions. The robot moves along the terrain which it defines with the defining device by positioning each leg in a desired place determined by the controlling device and then moving the body forward to resituate itself.

Leveling of the AMBLER Walking Machine: A Comparison of Methods.

Abstract: : For orthogonally-decoupled machines, such as the AMBLER, power efficiency is contingent upon keeping the body level. There are several ways of accomplishing this, which trade-off approximations of the complete phenomena versus simplicity of the implementation. In this report the effectiveness of four different strategies are evaluated for body attitude control. One of these uses vertical actuations to level the body ignoring the secondary geometric effects. Two alternate methods actuate only the vertical axes, but additionally utilize part of the horizontal kinematic information to calculate the required vertical displacements. Another method actuates both the horizontal and vertical joints in order to obtain ideally correct kinematic motion, but at the cost of higher energy expenditure. In this document the simulation of these methods and their implementation on the AMBLER are reported. This research shows that leveling methods that use only the vertical axes are most appropriate. The Simple Z-axes leveling method works satisfactorily to level using only six concurrent motions, ignoring the complexity of higher order kinematic calculations. The Z-axes method that is derived from the All-axes method has the consequence that the body drops when these equations are used to tilt the body. The Isoaltitude method performs slightly better than the Simple Z-axes method, by maintaining constant body height during both leveling and tilting maneuvers.

An application of tool insertion using model based vision

Abstract: This paper presents an application of tool insertion using model based vision. The requisite technologies, including model representation, sensor calibration and error quantification are discussed. These techniques are applied to a nuclear servicing task in a physical mock-up of a steam generator. 1. INTRODUCTION Tool insertion is a class of problems that mate two noncompliant parts in the presence of geometric uncertainty. For a subclass of tool insertion, an accurate model of the tool, its mating receptacle, and its surrounding environment contains sufficient information to drive the task. For these tool insertion problems a model does exist, but is not always accurate ,>nough to enable reliable manipulation. Model based vision offers one solution to the problem of reducing model uncertainty and providing precise scene data. Using sensors, an approximate model is corrected until it is SutXciently accurate for manipulation. Achieving model accuracy requires the application of a number of techniques such as sensor calibration, sensor error estimation and the identification of spurious sensor data. In this paper, model based vision is shown to be a viable solution to a tool insertion problem for the nuclear servicing industry. The development of a complete model based tool insertion system including sensor calibration, image processing, error estimation and methods for motion planning in the presence of sensor dropout is discussed. 2. PRIORWORK The development of manipulation for model based tool insertion requires that vision systems for model correction be developed, and that the manipulator be driven based on model information. Much work has been done in robotics toward the development of automated manipulation systems, the references cited here are certainly not all inclusive, but offer an overview of the technologies that influenced our work. Mitchell

Simulation of postural control for a walking robot

Abstract: Postural control is of utmost importance for walking robots, particularly for those that traverse rugged terrain. We have developed a dynamic model for locomotion in rugged terrain. The utilization of this model for postural control studies is presented. A modification of the Vertical Hybrid Control by Allocation method is proposed as a viable posW control scheme. However, our work shows that positional control is sufficient in order to achieve stable response with our mechanism.