Stephen L. Dickerson

Control of an omni-directional robotic vehicle with Mecanum wheels

The authors explore three aspects of the Mecanum wheeled vehicles, the ability to maneuver in congested spaces, the kinematics of wheel design, and considerations for wheel loading and traction. It is shown how omni-directional capability greatly reduces the amount of area and time required for maneuvers, and how the Mecanum wheel in particular reduces time because of the absence of singularities. The algorithms to convert desired motions to required wheel motions do not require excessive computation even in the case where they include compensation for wheel slip detection and correction. The authors also present some novel concepts, the multiple row driven wheel and the screw type variation of the Mecanum wheel.<<ETX>>

A CONTROLLER ENABLING PRECISE POSITIONING AND SWAY REDUCTION IN CRANES WITH ON-OFF ACTUATION

Abstract Precise manipulation of payloads is difficult with large cranes. Oscillation can be induced into the lightly damped system by motion of the overhead support point, or from environmental disturbances. A combined feedback and input shaping controller is presented here. The controller uses feedback to detect and compensate for positioning error in the overhead support unit (e.g. the bridge or trolley), and input shaping is used to negate motion-induced oscillation in the payload. The controller is implemented on a 10-ton bridge crane at the Georgia Institute of Technology. The controller generates simple on-off commands, suitable for typical cranes that employ on-off, relay-driven motors. The controller achieves good positioning accuracy, and significant payload sway reduction.

A Multi-Operational-Mode Anti-Sway and Positioning Control for an Industrial Bridge Crane

Abstract A 30-ton industrial bridge crane located at an aluminum sheet manufacturer has been equipped with a crane manipulation system enabling swing-free motion, disturbance rejection, and precise positioning. Previous investigations of anti-sway, positioning, and crane control have yielded important contributions in these areas. These advancements are combined into the unified crane manipulation system described here. An overview of this system is presented, along with experimental results, and a description of how human operators use the crane.

Intelligent material handling: use of vision

Vision systems will play an increasing role in inteffigent material handling systems. This paper discusses two hardware principles which make possible a host of cost-effective applications--integrated vision systems and the use of retroreflective materials. Described are (1) the design cost and performance characteristics of integrated systems those with the microcomputer array detector and illumination as part of a single circuit (2) the impact of using retroreflective materials those with apparent brightness of more than 1000 times that of diffuse white surfaces and (3) some specific applications: AGV guidance part handling and AS/RS control.

Outdoor tracking using machine vision, xenon strobe illumination, and retroreflective landmarks

This paper investigates developing a robust method for outdoor tracking using low cost machine vision. The conditioning method combines an electronically-shuttered vision system with a xenon strobe to produce a high contrast image of the structured target at up to a quarter mile away. The high contrast image eases landmark recognition which ultimately increases robustness and improves system response time. Tracking landmarks outdoors is important for farming, construction, and highway automation. Numerical analysis shows a retro-reflector can be detected to 530 meters with a S/N ratio of 2 for the nominally case of a 1 Joule xenon flash focused to 5 degrees with a flash duration of 100 microsecond(s) . The target position can be determined to within 17 millimeters at 400 meters using subpixel edge detection and a vision system with a 24 mm lens and 10 micrometers square pixels. Experimentally, the retro-reflective target achieved a 1.5 S/N at 91 meters which was 66.5 percent of the expected value. Experimentally, an IR blocking filter increased the S/N ratio by 42 percent by taking advantage of the differences in the spectrum of the xenon strobe and the sun. This result closely matches the expected S/N ratio increase associated with using an IR filter.

Scatterometry for machine vision

Specifications and design are provided for a low-cost scatterometer build to study the relationship between optical scatter and image formation. Design principles and considerations are discussed as they relate to digital imaging. Specifications and instrument limitations both mechanical and optical are examined and certain design choices are explained. The process of calibrating the instrument is considered and methods of noise suppression both electronic and optical are discussed. Finally, some measured data is presented.

Optimum illumination for machine vision using optical scatter data

Knowledge of the bidirectional optical scatter function of surfaces comprising a 2D scene is used to predict and optimize characteristics of a digitally captured image of the scene. Mathematical expressions that describe certain image properties including contrast, brightness, glare, etc., are developed from the scatter functions. It is these mathematical expressions that are maximized or minimized with respect to a set of coordinates used to describe the orientation of a collimated light source and imaging system relative to the scene. In this way, it is shown how illumination can be analytically prescribed to attenuated or accentuated certain properties of digital images without the trial-and-error procedure currently in practice.

Comments on the Automation of Material Handling

This chapter is a collection of fundamental ideas from several years involvement with the Material Handling Research Center. It results from the interactions of a controls oriented mechanical engineer with many materials handling professionals both in academia and industry. Most, but not all, of these professionals have industrial engineering backgrounds. As a consequence, the material handling community has a strong orientation toward operations issues and rather less concern with the technology of machinery used in material handling. This chapter discusses some very basic issues relative to automation of material handling with emphasis on some perceived misconceptions.

Control of High Speed Material Handling Manipulators

Significant advantages can be realized by achieving high-speed material handling manipulators, e.g. robots and AS/RS, without the weight and mechanical precision associated with traditional devices.