Bradley E. Bishop

Platoons of underwater vehicles

We have presented a decentralized control design methodology for regulating global functions of cooperating mobile systems. The application of relatively standard system-theoretic tools, leads to a novel broadcast-only communication structure. The feedback mechanism between vehicles is the measurement of the global variables and broadcast of their integrated values. More generally, the methods presented allow the designer to determine what explicit communication strategies are sufficient for a stabilizing decentralized control to exist. Using a simplified model, we showed that it is indeed possible to regulate global variables of a platoon of autonomous underwater vehicles, in particular, the center of the platoon and the distribution of the vehicles about the center. A relatively small amount of explicit communication is required between vehicles and that no vehicle must regulate its actual position. Further, the approach presented is scalable to any number of cooperating vehicles without the need for additional communication, although there is a practical limit on the size of the platoon.

Adaptive calibration and control of 2D monocular visual servo systems

Abstract For most visual servo systems, accurate camera/robot calibration is essential for precision tasks, such as tracking time-varying end-effector trajectories in the image plane of a remote (or fixed) camera. This paper presents details of control-theoretic approaches to the calibration and control of monocular visual servo systems in the case of a planar robot with a workspace perpendicular to the optical axis of the imaging system. An on-line adaptive calibration and control scheme is developed, along with an associated stability and convergence theorem. A redundancy-based refinement of this scheme is proposed and demonstrated via simulation.

Control of redundant manipulators using logic-based switching

We study the control of redundant planar robotic manipulators using a switched (or hybrid) control scheme, focusing on manipulators with a degree of redundancy of one. We emphasize the effectiveness of switched control systems with respect to stabilization and performance enhancement for this class of manipulators. We present a simulation study of logic-based switching control of a 3-DOF planar manipulator under end-effector trajectory tracking and demonstrate the capabilities of this scheme.

On the use of redundant manipulator techniques for control of platoons of cooperating robotic vehicles

In this correspondence, we discuss the parallelism between redundant manipulator control and the control of platoons (or swarms) of autonomous vehicles. We cast the platoon formation synthesis problem in an analogous manner to traditional redundancy resolution, and discuss techniques for real-time reactive path generation and control of the platoon. The efficacy of the proposed approach is demonstrated through simulation experiments.

Redundant manipulator techniques for partially decentralized path planning and control of a platoon of autonomous vehicles

An approach to real-time trajectory generation for platoons of autonomous vehicles is developed from well-known control techniques for redundant robotic manipulators. The partially decentralized structure of this approach permits each vehicle to independently compute its trajectory in real-time using only locally generated information and low-bandwidth feedback generated by a system exogenous to the platoon. Our work is motivated by applications for which communications bandwidth is severely limited, such for platoons of autonomous underwater vehicles. The communication requirements for our trajectory generation approach are independent of the number of vehicles in the platoon, enabling platoons composed of a large number of vehicles to be coordinated despite limited communication bandwidth.

Modern robotics engineering instruction

We discuss three basic principles of modern robotics education and contrast the traditional teaching style used in a majority of engineering classes with that necessary for a rapidly developing field such as robotics. Our basic tenet is that a modern robotic engineer must have knowledge, experience, and insight. While traditional education methods focus on knowledge and experience through the standard lecture-laboratory cycle, we submit that insight is the key to a complete robotics education. We conjecture that insight cannot be gained from textbooks, lectures, and laboratory exercises alone, as these tend to focus on merely academic rather than global and social issues. We present a discussion of the techniques used at the United States Naval Academy to inform, educate, and motivate students in the field of robotics.

On the application of redundant manipulator techniques to the control of platoons of autonomous vehicles

In this paper, we discuss the parallelism between redundant manipulator control and the control of platoon-level functions for systems of autonomous vehicles. We cast the platoon formation problem in an analogous manner to traditional redundancy resolution, and discuss techniques for control of the platoon.

Vision-based control of an air hockey playing robot

We demonstrate an integrated sensing and control design for high-speed ballistic manipulation in two dimensions. We show the effectiveness of a vision-based switched control scheme for precision impulsive manipulation. Vision-based hybrid control is a promising avenue of research for fully autonomous interaction between robots and complicated environments. Much work remains to be done in both computer vision and hybrid systems. In the context of robot air hockey, important future areas to investigate include the problems of modeling and identification of the environment dynamics, in particular, the table friction and puck spin. We show how the puck spin significantly influences its trajectory and subsequently our ability to perform accurate trajectory estimation and prediction.

Camera modelling for visual servo control applications

When designing a visual servo system, it is important to have a complete and accurate model of the imaging process. Unmodelled imaging dynamics may play an important role in the stability and performance of such systems. In this paper, we present a detailed camera model which can be used in the design and analysis of visual servo systems. Using the free-standing acrobot as a testbed, we analyze the effects of unmodelled imaging dynamics on visual servo control systems. We show that certain camera parameters strongly influence the performance of this system, and that accurate modeling is necessary for proper selection of imaging hardware.

Adaptive Calibration and Control of 2D Monocular Visual Servo Systems

Abstract For a majority of visual servo systems, accurate camera-robot calibration is essential for precision tasks, such as tracking time-varying end-effector trajectories in the image plane. This paper presents details of control-theoretic approaches to calibration of monocular visual servo systems in the case of a planar robot with workspace perpendicular to the optical axis of the imaging system. An on-line adaptive calibration and control scheme is developed along with an associated stability and convergence theorem. A redundancy-based refinement of this scheme is proposed and important issues are isolated for future study.