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Institute for Robotics and Intelligent Machines (IRIM)

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End date: 2009 × Start date: 2000 × search.filters.applied.f.isOrgUnitOfPublicationTitle: George W. Woodruff School of Mechanical Engineering ×

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Now showing 1 - 10 of 33
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    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.
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    A virtual reality operator Interface station with hydraulic hardware-in-the-loop simulation for prototyping excavator control systems
    (Georgia Institute of Technology, 2009-07) Elton, Mark D. ; Enes, Aaron R. ; Book, Wayne J.
    A multimodal operator interface station is developed to display a realistic virtual reality depiction of a compact excavator performing general digging tasks. The interface station includes engine audio feedback and a near life-size operator display attached to a full-size cab. The excavator dynamics are determined by models of the hydraulic system, the linkage system, and the soil digging forces. To maximize the fidelity of the hydraulic model, certain ldquovirtualrdquo components of the model are replaced with real-time hardware-in-the-loop (HIL) simulations of the actual hardware. HIL simulation is done in a geographically isolated facility, with Internet based communication between HIL and the remote operator interface. This is the first reported high-fidelity operator interface to be combined with remote hydraulic HIL simulations.
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    A novel approach to fabric control for automated sewing
    (Georgia Institute of Technology, 2009-07) Winck, Ryder C. ; Dickerson, Stephen L. ; Huggins, James D. ; Book, Wayne J.
    This paper describes a novel fabric manipulation method for fabric control during the sewing process. It addresses issues with past attempts concerning fabric position and tension control. The method described involves replacing the current sewing feed mechanism with a servo controlled manipulator to both feed and control the fabric. The manipulator is coupled with a machine vision system that tracks the threads of the fabric to provide real-time position control that is robust with respect to fabric deformations. A prototype of the manipulator is used to demonstrate the feasibility of the concept, reaching accelerations up to 27 g’s and following a closed loop trajectory with open loop control while operating in coordination with an industrial sewing machine. The system described also offers a general solution to high accuracy and high acceleration position control systems.
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    Steerability in Planar Dissipative Passive Robots
    (Georgia Institute of Technology, 2009) Gao, Dalong ; Book, Wayne J.
    Steerability is intuitively the ability to change directions. In this paper, a formal definition is given for the steerability of a robot achieved either passively or actively. A dissipative passive robot uses only passive actuators such as brakes and clutches (a clutch is essentially a brake plus a gearbox) to redirect or steer operator-imposed motion by dissipating energy. While it has safety and ergonomic advantages, which are essential for human interactions, it also has difficulties in redirecting certain motions since passive actuators cannot add energy. The force generated from a passive actuator is used to measure the steerability. A steerability theorem was then developed for a manipulator with generalized passive actuators. The steerability analysis for an example diamond-shaped manipulator shows the difference in steerability when using only brakes or a combination of brakes and clutches. Further analyses show the difference comes from the ability of a clutch to change the direction of the generated force in the subject robot by altering the effective gear ratios
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    A hardware-in-the-loop simulation testbed for emulating hydraulic loads representing the complete dig cycle of a construction machine
    (Georgia Institute of Technology, 2008) Enes, Aaron R. ; Book, Wayne J.
    A hardware-in-the-loop (HIL) simulation testbed is designed to be capable of emulating the entire domain of hydraulic workport loads incident on a test valve during normal work cycle operations of a certain hydraulic construction machine, such as a backhoe or excavator. The HIL testbed is a useful tool during rapid prototyping of control algorithms for the test valve, and for performing controlled experiments with the valve in the context of developing valve control algorithms to improve the overall energy efficiency of hydraulic systems. This paper discusses four key topics: the architecture of the real-time simulation and testbed control process, the modeling and validation of the emulated machine dynamics, the controller development for the HIL testbed, and some initial performance testing of the HIL testbed.
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    Dynamics of embodied dissociated cortical cultures for the control of hybrid biological robots.
    (Georgia Institute of Technology, 2007-11-14) Bakkum, Douglas James
    The thesis presents a new paradigm for studying the importance of interactions between an organism and its environment using a combination of biology and technology: embodying cultured cortical neurons via robotics. From this platform, explanations of the emergent neural network properties leading to cognition are sought through detailed electrical observation of neural activity. By growing the networks of neurons and glia over multi-electrode arrays (MEA), which can be used to both stimulate and record the activity of multiple neurons in parallel over months, a long-term real-time 2-way communication with the neural network becomes possible. A better understanding of the processes leading to biological cognition can, in turn, facilitate progress in understanding neural pathologies, designing neural prosthetics, and creating fundamentally different types of artificial cognition. Here, methods were first developed to reliably induce and detect neural plasticity using MEAs. This knowledge was then applied to construct sensory-motor mappings and training algorithms that produced adaptive goal-directed behavior. To paraphrase the results, most any stimulation could induce neural plasticity, while the inclusion of temporal and/or spatial information about neural activity was needed to identify plasticity. Interestingly, the plasticity of action potential propagation in axons was observed. This is a notion counter to the dominant theories of neural plasticity that focus on synaptic efficacies and is suggestive of a vast and novel computational mechanism for learning and memory in the brain. Adaptive goal-directed behavior was achieved by using patterned training stimuli, contingent on behavioral performance, to sculpt the network into behaviorally appropriate functional states: network plasticity was not only induced, but could be customized. Clinically, understanding the relationships between electrical stimulation, neural activity, and the functional expression of neural plasticity could assist neuro-rehabilitation and the design of neuroprosthetics. In a broader context, the networks were also embodied with a robotic drawing machine exhibited in galleries throughout the world. This provided a forum to educate the public and critically discuss neuroscience, robotics, neural interfaces, cybernetics, bio-art, and the ethics of biotechnology.
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    New command shaping methods for reduced vibration of a suspended payload with constrained trolley motion
    (Georgia Institute of Technology, 2007-11) Enes, Aaron R. ; Hsu, Timothy Y. ; Sodemann, Angela A.
    In manufacturing environments, a common task is to quickly move a suspended payload point-to-point along a fixed overhead conveyor track without inducing significant payload vibration. Recent research in command shaping has shown remarkably effective ways to reduce the swing of a suspended payload providing the motion of the trolley is not constrained. However, the development of a command shaper where the trajectory of the trolley is constrained to follow a fixed curvilinear path has not been explored. This paper will present the development of a simple feedforward command shaper for fast, low vibration, point-to-point movement of a payload suspended from a trolley constrained to follow a fixed generalized path. The command shaping method involves modifying the command signal by convolving it with a series of impulses. Prior work has suggested command shaping to be very effective for fast, low-vibration movement of flexible systems. In this paper, command shaping methods are applied to an overhead conveyor system constrained to move along a fixed curvilinear path. Two new command shapers are presented for canceling payload vibration induced by motion of the trolley along the path. The designed Tangential Vibration (TV) shaper reduces payload vibrations induced by tangential accelerations of the trolley along the path, while the Centripetal-Tangential Vibration (CTV) shaper reduces vibrations induced by both tangential and centripetal accelerations. A key result of this study is that a command shaper having at least three impulses is required to yield zero residual vibration for motion along a curvilinear path. A simple pendulum payload attached to an actual small-scale overhead trolley following a constrained path is used to evaluate the performance of the designed command shapers. It is shown that the designed shapers significantly reduce payload swing compared to unshaped performance. An experimental sensitivity analysis shows the designed shapers are robust to system modeling errors and variations in path parameters.
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    Control limitation analysis for dissipative passive haptic interfaces
    (Georgia Institute of Technology, 2005-11-18) Gao, Dalong
    This research addresses the ability of dissipative passive actuators to generate control effects on a passive haptic interface. A haptic display is a human-machine interface that constructs a sensation of touch for the human operator. Applications can be found in various industries, space, medicine and construction etc. A dissipative passive haptic display contains passive actuators that can remove energy from the system by resisting motions in the system. The advantage of a dissipative passive haptic display is better safety compared to an active display. Its disadvantage is the limited control ability from the passive actuators. This research starts with the identification of the control ability and limitations of dissipative passive haptic interfaces. The ability is identified as the steerability, the ability to redirect motions of a manipulator. The force generation analysis of each individual actuator is then selected as an approach to evaluate the steerability. Steerability metrics are defined to evaluate the steerability. Even though non-redundant manipulators dont have desired steerability, optimal steering configurations are found for the best operation. Steerability is improved by redundancy in serial or parallel structures. A theorem is developed to evaluate steerability for redundant manipulators. The influence of system dynamics on their steerabilities is discussed. Previously developed haptic interfaces are evaluated based on their steerabilities. Steerability analysis of three-dimensional haptic interfaces is also given to a limited extent as an extension of the two-dimensional cases. Brakes and clutches are the two types of dissipative passive actuators in this research.
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    Speed Control and Position Estimation of Small Hydraulic Cylinders for Digital Clay Using PWM Method
    (Georgia Institute of Technology, 2004-07) Zhu, Haihong ; Book, Wayne J.
    Digital Clay is a new generation 3D computer input and output device for surface shape and haptic effects. The device consists of arrays of fluidically actuated cells under the control of valves connected to two pressure reservoirs in a manner ultimately suitable to an implementation in MEMS technology. At the current stage, it is very difficult to implement a tiny position sensor into the tiny cell. This paper presents a control method for the speed and position estimation and control for the cells of digital clay only using low cost pressure sensors and without using any position-sensing device.
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    Stability in active mass damping control of a flexible robot
    (Georgia Institute of Technology, 2004-03) Krauss, Ryan W. ; Book, Wayne J.
    Active mass damping has been shown to be an effective method for reducing vibrations in flexible robots by previous researchers working on an experimental test bed at Georgia Tech. Acceleration feedback can cause instability in this test bed. System identification and root locus analysis were used to determine the causes of this instability. Several potential modifications to the system were simulated including: 1) replacing accelerometers with position sensors; 2) removing second order dynamics from the actuator; and 3) adding an additional accelerometer to use modal feedback.