Communicating Materials Systems Knowledge through Processing-Structure-Properties-Performance (PSPP) Maps

( 2018-01) Goulding, Ashley N. ; Leung, Jonathan F.W. ; Neu, Richard W.

Knowledge about the behavior of a specific materials system is concisely summarized in a Processing-Structure-Properties-Performance (PSPP) map. This is a useful tool that can effectively serve as a standard method of communication regarding the physical and chemical mechanisms that control the performance of a materials system, and gives guidance on the type of data required to accurately characterize that materials system in its entirety. This article describes a workflow to generate a map for any materials system, and then applies these steps to develop a map for Ni-base superalloy synthesized by additive manufacturing.
Recursive Algorithm for Motion Primitive Estimation

(Georgia Institute of Technology, 2011-05) Enes, Aaron R. ; Book, Wayne J.

The need for knowing future manipulator motion arises in several robotics applications, including notification or avoidance of imminent collisions and real-time optimization of velocity commands. This paper presents a real-time, low overhead algorithm for identification of future manipulator motions, based on measurements of prior motions and the instantaneous sensed actuator velocity commanded by an operator. Experimental results with a human-controlled, two degree of-freedom manipulator demonstrate the ability to quickly learn and accurately estimate future manipulator motions.
Auto-Calibration Based Control for Independent Metering of Hydraulic Actuators

(Georgia Institute of Technology, 2011-05) Opdenbosch, Patrick ; Sadegh, Nader ; Enes, Aaron R. ; Book, Wayne J.

This paper describes a novel auto-calibration state-trajectory-based control method and its application to electronic flow control for independent metering systems. In this paper, the independent metering architecture that is considered uses five Electro-Hydraulic Poppet Valves (EHPV’s). The proposed control method is applied to four of these valves, arranged in a Wheatstone bridge configuration, to regulate the flow of hydraulic oil coming into and out of an actuator. For simplicity, the fifth valve is operated via open-loop to control the supply pressure. Experimental data presented herein demonstrate that the control method learns the valve’s conductance characteristics (i.e. the inverse input-state dynamic map of the valve) while simultaneously controlling the motion of the hydraulic actuator.
Compensation for Biodynamic Feedthrough in Backhoe Operation by Cab Vibration Control

(Georgia Institute of Technology, 2011-05) Humphreys, Heather C. ; Huggins, James D. ; Book, Wayne J.

This research investigates and seeks to mitigate the undesirable effects of biodynamic feedthrough in backhoe operation. Biodynamic feedthrough occurs when motion of the controlled machine excites motion of the human operator, which is fed back into the control input device. This unwanted input can cause significant performance degradation, which can include limit cycles or even instability. Backhoe user interface designers indicate that this is a problem in many conventional machines, and it has also proved to degrade performance in this testbed. A particular backhoe control system, including the biodynamic feedthrough, is modeled and simulated. Cab vibration control is selected as a means to mitigate the biodynamic feedthrough effect. Two controller based methods are developed based on these models and presented, both of which use the working implement itself to reduce the cab motion. In this case, the backhoe arm has dual functionality, to perform excavation operations and to cancel cab vibration. Results show that significant reductions in cab motion can be obtained with minimal tracking performance degradation, without additional actuators.
A Robust Nonlinear Observation Strategy for the Control of Flexible Manipulators

(Georgia Institute of Technology, 2011-05) Post, Brian K. ; Book, Wayne J.

Flexibility is often an unavoidable consequence of the desire for high speed and performance manipulators. This paper proposes a method that improves the performance of flexible manipulators through the employment of robust state estimation techniques. These techniques are based on discrete time Kalman filtering and sliding mode principles. A simple model for a single degree of freedom flexible manipulator is derived and a control scheme is chosen and implemented. The latter includes a robust non-linear estimator. Simulation and preliminary experimental results are presented that demonstrate the validity of the proposed control scheme.
An Excavator Simulator for Determining the Principles of Operator Efficiency for Hydraulic Multi-DOF Systems

(Georgia Institute of Technology, 2011-03) Elton, Mark D. ; Book, Wayne J.

This paper discusses an excavator simulator constructed to evaluate the effects of human-machine interfaces (HMIs) on operator productivity. Simulation allows for standardization of the machine and environment and is less time consuming and cheaper than implementing the controller on the machine. The simulator discussed in this paper includes a realistic graphical display that exceeds the current academic simulators, audio, and a new soil model that accounts for all possible trajectories of the bucket through the soil. Two coordinated control schemes were implemented on the simulator and preliminary tests were performed to demonstrate that the simulator can be used to evaluate HMIs.
Optimizing Point to Point Motion of Net Velocity Constrained Manipulators

(Georgia Institute of Technology, 2010-12) Enes, Aaron R. ; Book, Wayne J.

The architecture of many hydraulic manipulators, such as excavators common in the earthmoving industry, have constraints on the net sum of actuator speeds. This paper gives the necessary conditions for minimum-time velocity commands for point to point motion. A kinematic model of the manipulator is used. The optimal solution is not always unique. We propose a particular optimal solution, u*, that is stationary. The optimality of inputs unequal to u* is evaluated by the position of u* in the input domain. Several examples are given to demonstrate the analysis.
Usability Evaluation of a Coordinated Excavator Controller with Haptic Feedback

(Georgia Institute of Technology, 2010-06) Osafo-Yeboah, Benjamin ; Elton, Mark D. ; Jiang, Xiaochun ; Book, Wayne J.

The purpose of this study is to conduct a usability evaluation in order to investigate the actions and behaviors of human operators as they interact with a coordinated excavator controller with haptic feedback, and to identify potential usability problems that may confront operators as they interact with this new excavator interface. Traditional excavators usually use levers and pedals as the interface for operator control. However, with advances in computing power, it is possible to incorporate force feedback, or haptics, into the operator interface. The haptic interface is expected to provide force feedback to operators to give a sense of 'feel' to operators as they interact with the excavator through the use of the haptic Phantom device and, therefore, assist operators in performing their tasks more efficiently and effectively. This research aims to identify potential usability problems that may confront users, and to provide appropriate design suggestions to the design team. Results from the study showed that, users find the coordinated excavator controller to be intuitive, easy to learn and easy to use. Several usability issues were also identified, and appropriate design modifications were recommended.
Blended Shared Control of Zermelo's Navigation Problem

(Georgia Institute of Technology, 2010) Enes, Aaron R. ; Book, Wayne J.

Many machines–from hydraulic excavators to mobile wheelchairs–are manually controlled by a human operator. In practice, the operator assumes responsibility for completing a given task at maximum utility, even though the optimal inputs may be unknown to the operator. Here we introduce a simple technique termed Blended Shared Control, whereby the human operator commands are continually merged with the commands of a robotic agent. This approach is shown to result in a lower task completion time than manual control alone when applied to a problem motivated by Zermelo’s navigation problem. Experimental results are presented to compare blended shared control to other types of controllers including manual control, heads up display, and haptic feedback. Trials indicate that the shared control does in fact decrease task completion time when compared to fully manual operation.
Modeling of biodynamic feedthrough in backhoe operation

(Georgia Institute of Technology, 2009-10) Humphreys, Heather C. ; Book, Wayne J. ; Huggins, James D.

An advanced backhoe user interface has been developed which uses coordinated control with haptic feedback. Results indicate that the coordinated control provides more intuitive operation that is easy to learn, and the haptic feedback also relays meaningful information back to the user in the form of force signals from digging forces and system limitations. However, results show that the current system has significant problems with biodynamic feedthrough, where the motion of the controlled device excites motion of the operator, resulting in undesirable forces applied to the input device and control performance degradation. This unwanted input is difficult to decouple from the intentional operator input in experiments. This research presents an investigation on the effects of biodynamic feedthrough on this particular backhoe control system, using system identification to empirically define models to represent each component. These models are used for a preliminary simulation study on potential methods for biodynamic feedthrough compensation.