William Robert Norris

A DESIGN TOOL FOR OPERATOR- ADAPTIVE STEERING CONTROLLERS

One of the major deterrents of designing a control system for interactive use with an operator is the lack of a systematic procedure for modeling and incorporating human behavior directly into the design process. In many cases, direct operator feedback is difficult for qualitative design without a costly, full–scale physical prototype. The objective of this article is to present a modular framework, known as virtual design tools, to design the electrohydraulic steering system of off–road vehicles. The aim was to adapt the electromechanical interface between the operator’s command signal and the fixed control and dynamic systems. The adaptation was performed with the intent of modifying the system performance to be more acceptable to the operator without altering the control system or vehicular components. This conceptual design tool was studied via a computer simulation for designing an operator–adaptive steering controller for an articulated off–road vehicle. The simulation results indicated that this “operator–in–the–loop” design method could successfully incorporate human behavior in the controller design process using the virtual design tool.

RULE-BASE REDUCTION FOR A FUZZY HUMAN OPERATOR PERFORMANCE MODEL

This article presents a general procedure of reducing the number of fuzzy rules needed to perform a human-in-the-loop (HIL) design process using a virtual environment design tool. This HIL design process is created for designing an adaptive steering controller to achieve optimal vehicle maneuverability regardless of operator’s driving behaviors. In this design process, a dynamic model of an articulated off-road vehicle is implemented to determine the vehicle steering maneuverability via real-time simulation, and a virtual operator model is used to generate steer actions to guide the vehicle traveling on a predetermined path. Due to the complicated nature of steering an articulated vehicle, a high degree of granularity was required to cover all possible combinations of operating conditions. In order to meet real-time simulation requirements, a hierarchical fuzzy relations control strategy (FRCS) has been developed to reduce the size of the virtual operator’s rule-base. Using the developed hierarchy, the fuzzy steering controller could effectively incorporate the reduced size rule-base. Validation simulation showed that this hierarchical approach could reduce the size of the rule base by over 98% without affecting the performance of the virtual operator.

On a control policy that maintains indoor air quality in a variable-air-volume air-handling unit

The air handling unit (AHU) in a variable air volume (VAV) heating, ventilation and air conditioning (HVAC) system consists of outside air, return air and exhaust air dampers. The volume flow of air through a damper can be modified by changing the damper angles. In a typical AHU, outside air is mixed with recycled air and this mixture is then circulated to the various rooms in a building. A portion of the net volume flow out of these rooms is exhausted while the remainder is recycled. The net volume flow is usually determined by a supply fan in the duct, whose speed is dependent on the quiescent thermal load. In the absence of any regulation, the volume flow of outside air depends on the speed of the supply fan. The indoor air quality (IAQ) standards require a constant intake of outside air, independent of the speed of the supply fan. Additionally, motivated by the fact that air entering the system through the exhaust air damper is not as appropriately preconditioned as that entering the system through the outside air damper, it is required that air does not enter the AHU through the exhaust air damper. Using flow conservation equations, we derive a model for the AHU. This model was validated by experimental data collected on a full-scale HVAC test facility. Using this model, we provide a control policy that achieves the objective of maintaining IAQ in a VAV HVAC system where the flow across the exhaust air damper is never reversed. This control policy is validated manually using experimental data.

A Novel Real-Time Human Operator Performance Model for Performing Adaptive System Design

The objective of this paper is to demonstrate the development of a tool used in a design framework for performing real time human-in-the-loop system design using virtual environments. The design framework, known as virtual design tools, requires a human operator performance model (HOPM) component. The model aids in the development of adaptive optimal solutions for qualitative design by providing consistent control decisions. This paper presents the design process for a controller that emulates real-time human operator perception and experience for automatic control applications using fuzzy logic. The design technique was successfully applied to a four degree of freedom articulated wheel loader with the task of following a desired trajectory. Variable driving styles were obtainable by altering the HOPMs perception while maintaining a fixed common sense rule-base. The success of this technique demonstrates that it is applicable to a wide range of human-in-the-loop problems and in intelligent vehicle algorithm development.

Virtual Design Tools: A Technique for Performing Qualitative Human-in-the-Loop System Design

One of the major deterrents in designing control systems for interactive use with a human operator is the lack of a systematic procedure for modeling and incorporating human behavior directly in the design process. In many cases, direct human operator feedback was difficult for qualitative design without a costly, high–fidelity physical prototype. The objective of this paper is to present an overview of a modular framework, known as virtual design tools, developed to design the electrohydraulic steering system of an articulated wheel loader. The aim was to adapt the electromechanical interface between the operator’s command signal and the fixed control and dynamic systems. The adaptation was performed with the intent of modifying the system performance so that it would be more acceptable to a human operator without altering the control system or vehicular components. In order to achieve this objective, there were several significant accomplishments. The first was the development of a nontrivial model that provided adequate real time simulations for human-in-the-loop systems using a standard control system design package. A virtual operator has been realized that will navigate the vehicle along a predetermined trajectory mimicking consistent human performance characteristics while using a human-like interpretation of position and orientation errors. Several different structures have been studied for use as an adaptive interface between the operator and the vehicle and a proof of concept for virtual design tools has been attained. The successful employm ent of virtual design tools to the wheel loader steering design application and an overview of the results are discussed.