William A. Gruver

Trajectory synthesis and physical admissibility for a biped robot during the single-support phase

The synthesis and verification of biped walking trajectories during the single-support phase is discussed. The biped is modeled as a seven-link twelve degree-of-freedom anthropomorphic robot. By utilizing the zero moment point (ZMP) and the equivalent force-moment, the physical admissibility of the biped walking is characterized. For physically realizable walking during the single-support phase, the trajectory of the ZMP on the ground must be inside the stable region of the supporting sole. A biped walking trajectory specified by eight pattern parameters is derived through inverse kinematics. ZMP trajectories for different walking patterns and the influence of the pattern parameters on the ZMP trajectories are presented.<<ETX>>

Design of a single-lens stereo camera system

Abstract A camera system is designed that can obtain stereo information in a single shot and through a single lens. A single image obtained by this camera is equivalent to two images obtained by two aligned cameras with exactly the same optical properties. In this system, stereo is achieved by viewing the reflections of a scene in two mirrors that have a common axis. The angle between the mirrors may be changed to adjust the field of vision of the camera and to fixate at desired points in a scene.

Performance evaluation of two-degree-of-freedom planar parallel robots

We utilize a geometric model of the solution space to obtain analytical relationships between the link lengths of two-degree-of-freedom parallel planar manipulators and performance criteria based on the global conditioning and global velocity indices. The model is used to develop graphical charts that are useful for analysis and design of the mechanisms.

Control of a biped robot in the double-support phase

The development and implementation of an advanced control system for a seven-link, 12-degree-of-freedom, biped robot in the double-support phase are addressed. A constrained dynamic model of the biped robot is formulated and a reduced order model for the double-support phase is derived. In this model the dependent variables are related to the independent variables through the kinematic Jacobian. Control strategies based on feedforward compensation and linear state feedback are derived for tracking specified joint trajectories. The approach is demonstrated using results of a sway motion obtained from a prototype biped robot that has been constructed. >

A unified approach for robot motion planning with moving polyhedral obstacles

A unified approach suitable for path planning with moving polyhedral obstacles is presented. The planner views the space-time configuration of free space as disjoint polytopes that represent a time-dependent environment consisting of moving and stationary objects. Each point in the space-time domain is mapped into a unique polytope set. The planner then constructs a family of feasible collision-free trajectories by searching connected polytopes between the start polytope and the goal polytope that satisfy the speed and time constraints. Finally, a near-optimal trajectory is determined by constrained optimization. This approach does not require that obstacles be nonoverlapping or noncolliding. In addition, the obstacle is allowed to move faster than the planned robot. However, the speed of the obstacle must be piecewise-constant. The proposed approach can be easily extended to motion planning in higher dimensional spaces. >

Inverse kinematics and inverse dynamics for control of a biped walking machine

Analytical techniques are presented for the motion planning and control of a 12 degree-of-freedom biped walking machine. From the Newton-Euler equations, joint torques are obtained in terms of joint trajectories, and the inverse dynamics are developed for both the single-support and double-support cases. Physical admissibility of the biped trajectory is characterized in terms of the equivalent force-moment and zero-moment point. This methodology has been used to obtain reference inputs and implement the feedforward control of walking robots. A simulation example illustrates the application of the techniques to plan the forward-walking trajectory of the biped robot. The implementation of a prototype mechanism and controller is also described.

Industrial robot programming languages: A comparative evaluation

Eight commercially available high-level robot programming languages developed by industrial robot builders and research laboratories are evaluated. These languages are: AL; AML; Help; Jars; MCL; Rail; RPL; and Val. The historical background of the languages is reviewed. The languages are evaluated on the basis of data types, control structures, motion specification, use of sensors, and interface with external machines and devices. Common and uncommon features are noted. Facilities for program editing, entry, debugging, and teaching are compared. Conclusions are given regarding their present status and future development.

Automated infrared imaging temperature measurement with application to upward flame spread studies. Part I

Abstract This article describes a new experimental technique with wide application that has been proven for wall fires. To measure the spread rate of the pyrolysis front along vertically oriented flat and corner walls, it may be necessary to measure transient temperature profiles on the walls. Conventional thermocouple and visual observation methods, however, have limitations due to complexity of implementation and the inherent ambiguity of visual observations due to interference from flames. To overcome these limitations, an automated infrared imaging system was applied to obtain two-dimensional wall surface temperature data in a relatively large area. In addition, upward flame spread experiments were conducted over vertically oriented PMMA flat and color board corner walls; and surface thermocouple and infrared imaging temperature data were compared in the PMMA wall fires. All the results indicate that the infrared system with a (10.6 ± 0.5 μm) bandpass filter successfully avoids interferences from the flame allowing measurements of temperature distribution on the fire-heated wall, from which the spread rate in any direction can be deduced. However, this technique will fail for flames whose emissivity is greater than 0.1.

Kinematic control of redundant robots and the motion optimizability measure

This paper treats the kinematic control of manipulators with redundant degrees of freedom. We derive an analytical solution for the inverse kinematics that provides a means for accommodating joint velocity constraints in real time. We define the motion optimizability measure and use it to develop an efficient method for the optimization of joint trajectories subject to multiple criteria. An implementation of the method for a 7-dof experimental redundant robot is present.

Definition and force distribution of power grasps

This research treats grasping of an object by a multifingered robot hand. By decomposing the space of contact forces exerted between the fingers and the grasped object into subspaces we develop a method to determine the dimensions of the subspaces with respect to the connectivity of the grasped object. This approach provides insight into different grasps based on a classification into three types. A power grasp is defined when the connectivity of the grasped object is equal to or less than zero. The analysis of contact force distribution is simplified for a power grasp with zero connectivity. Examples for dimensional determination are illustrated.