John C. Fiala

TRICLOPS: a tool for studying active vision

The design, performance, and application of The Real-time, Intelligently ControLled, Optical Positioning System (TRICLOPS) are described in this article. TRICLOPS is a multiresolution trinocular camera-pointing system which provides a center wide-angle view camera and two higher-resolution vergence cameras. It is a direct-drive system that exhibits dynamic performance comparable to the human visual system. The mechanical design and performance of various active vision systems are discussed and compared to those of TRICLOPS. The multiprocessor control system for TRICLOPS is described. The kinematics of the device are also discussed and calibration methods are given. Finally, as an example of real-time visual control, a problem in visual tracking with TRICLOPS is examined. In this example, TRICLOPS is shown to be capable of tracking a ball moving at 3 m/s, which results in rotational velocities of the vergence cameras in excess of 6 rad/s (344 deg/s).

TRICLOPS: a high-performance trinocular active vision system

The design, performance, and application of the real-time, intelligently controlled, optical positioning system (TRICLOPS) are described. TRICLOPS is a multiresolution trinocular camera-pointing system which provides a center wide-angle view camera and two higher-resolution vergence cameras. It is a four-degree-of-freedom direct-drive system which exhibits dynamic performance comparable to the human visual system. The vergence degrees of freedom can achieve peak velocities in excess of 30 rad/s, and peak accelerations of 1100 rad/s/sup 2/. In an example of visual tracking, TRICLOPS is shown to be capable of following a ball moving at 3 m/s, with rotational velocities of the vergence axes in excess of 6 rad/s.<<ETX>>

The NASREM robot control system standard

Abstract The problem of robot control is approached from a systems standpoint where a complete control system must include all of the aspects involved in moving a robot, not just the algorithms in the classic controls literature. The NASA/NBS Standard Reference Model for Telerobot Control System Architecture (NASREM) provides the framework for a complete manipulator control system. It is composed of three hierarchies: task decomposition, world modeling, and sensory processing. The task decomposition hierarchy divides the task into smaller substasks. In order to achieve the desired decomposition, the task decomposition hierarchy must often access information stored in the world modeling hierarchy, which contains a workspace representation, object descriptions, robot models, etc. The sensory processing hierarchu constantly fills the world model with processed sensor information. The NASREM functional architecture was developed for NASAs Flight Telerobotic Servicer, a two-armed robot which will build and maintain the Space Station. However, the control concepts proposed by the NASREM functional architecture immediately transfer to other applications such as in manufacturing, autonomous vehicles, etc.

The effect of time delay and discrete control on the contact stability of simple position controllers

By analysis of the driving-point admittance, it is shown how time delays and discrete control can create instabilities for a simple manipulator position controller in contact with the environment. The lowest frequency of contact instability due to time delay or sampling is determined analytically. It is shown how mechanical compliance between the motor and point of contact can eliminate these instabilities. To achieve the best relative stability when contacting arbitrary environments, the mechanical/control design of manipulators should maintain a critical relationship between the frequency of the compliant mode and a frequency associated with contact instability. >

The real-time control system of the Horizontal Workstation robot

A 200-word or less factual summary of most significant information. If document includes a significant bi bliography or literature survey, mention it here) This manual describes the real-time control system used to control the robot in the Horizontal Workstation of the Automated Manufacturing Research Facility.

Servo Level Algorithms For The NASREM Telerobot Control System Architecture

The NASA/NBS Standard Reference Model (NASREM) Telerobot Control System Architecture defines a logical computing architecture for robotics. The architecture provides a framework for integrating a variety of control techniques, and for combining teleoperation and autonomy in one system. This paper demonstrates these aspects of NASREM for the lowest level of the architecture, the Servo Level. The Servo Level supports algorithms for robot manipulator control found in the literature.

An Architecture To Support Autonomy, Teleoperation, And Shared Control

Described is an approach to the functional architecture of a telerobot so that autonomy, teleoperation, and shared control can all be supported. The system is hierarchically organized where task decomposition, world modeling, and sensory processing are explicitly represented. Goals at each level of the hierarchy are decomposed spatially and temporally into simpler tasks which become goals for lower levels. The spatial decomposition facilitates control and coordination of multi-arm robots. A description of the lowest level, the Servo Level, is presented, along with the operator control interface at that level.

Experimental Evaluation of Cartesian Stiffness Control on a Seven Degree-of-Freedom Robot Arm

The programmability of Cartesian stiffness in Cartesian servo control algorithms that do not use explicit force feedback is examined. A number of Cartesian algorithms are implemented and evaluated on a commercial seven degree-of-freedom robot arm, using the NASREM robot control system testbed. It is found that Cartesian servo algorithms which use the transpose of the Jacobian and model-based gravity compensation, provide easy programmability and accurate reproduction of stiffnesses over a wide range. When dynamic behavior is a consideration, dynamic damping control, augmented to include a parameterization of the manipulator self-motion, provides superior performance and programmability.

Adaptive inertia compensation using a cerebellar model algorithm

A method for adaptively compensating for inertia in the control of robotic manipulators is described. The method uses an adaptive network which can be related to a number of contemporary models of the cerebellum. Simulations of a three-link planar manipulator show that the algorithm compensates for inertia during a movement without a priori knowledge. The fact that motions need not be repetitive gives the algorithm significant practical value.<<ETX>>

The effect of time-delay and discrete control on the contact stability of simple position controllers

By analysis of the driving-point admittance, it is shown how time delays and discrete control can create instabilities for a simple position controller in contact with the environment. The lowest frequency of contact instability due to time delay or sampling is determined analytically. It is shown how mechanical compliance between the motor and point of contact can eliminate these instabilities. To achieve the best relative stability when contacting arbitrary environments, the mechanical/control design of manipulators should maintain a critical relationship between the frequency of the compliant mode and a frequency associated with contact instability.<<ETX>>