Bickford, David
Overview
Works:  11 works in 11 publications in 1 language and 23 library holdings 

Genres:  History Filmed panel discussions 
Roles:  Author 
Classifications:  F1543, 738.309945 
Publication Timeline
.
Most widely held works by
David Bickford
Victorian demijohns by
Ken Arnold(
Book
)
1 edition published in 2009 in English and held by 8 WorldCat member libraries worldwide
1 edition published in 2009 in English and held by 8 WorldCat member libraries worldwide
Face Of Tomorrow by
David Bickford(
Book
)
1 edition published in 2004 in English and held by 3 WorldCat member libraries worldwide
1 edition published in 2004 in English and held by 3 WorldCat member libraries worldwide
Path following and stabilization of an autonomous bicycle by
David Bickford(
Book
)
1 edition published in 2013 in English and held by 3 WorldCat member libraries worldwide
In this thesis we investigate the problem of designing a control system for a modern bicycle so that the bicycle is stable and follows a path. We propose a multiloop control architecture, where each loop is systematically designed using linear control techniques. The proposed strategy guarantees that the bicycle asymptotically converges to paths of constant curvature. A key advantage of our approach is that by using linear techniques analysis and controller design are relatively simple. We base our control design on the nonlinear (corrected) Whipple model, which has been previously verified for correctness and experimentally validated. The equations of motion for the nonlinear model are very complicated, and would take many pages to explicitly state. They also have no known closed form solution. To enable analysis of the model we linearize it about a trajectory such that the bicycle is upright and travelling straight ahead. This linearization allows us to arrive at a parameterized linear timeinvariant statespace representation of the bicycle dynamics, suitable for analysis and control design. The innerloop control consists of a forwardspeed controller as well as a lean and steer controller. To keep the bicycle at a constant forward speed, we develop a highbandwidth proportional controller that uses a torque along the axis of the rear wheel of the bicycle to keep the angular velocity of the rear wheel at a constant setpoint. To stabilize the bicycle at this forward speed, lean torque and steer torque are treated as the control signals. We design a statefeedback controller and augment integrators to the output feedback of the lean angle and steer angle to provide perfect steadystate tracking. To arrive at the gains for state feedback, linearquadratic regulator methods are used. When following a constantcurvature path, a vehicle has a constant yaw rate. Using this knowledge, we begin designing the outerloop pathfollowing control by finding a map that converts a yaw rate into appropriate lean angle and steer angle references for the inner loop. After the map is completed, system identification is performed by applying a yawrate reference to the map and analyzing the response of the bicycle. Using the linear approximation obtained, a classical feedback controller for yawrate tracking is designed. In addition to yawrate control, to track a path the yaw angle of the bicycle must match that of the path and the bicycle must physically be on the path. To analyze these conditions a linear approximation for the distance between the bicycle to the path is found, enabling construction of a linear approximation of the entire system. We then find that by passing the signal for the difference in yaw rate and the distance through separate controllers, summing their output, and subtracting from the reference yaw rate of the path, the bicycle converges to the path. After developing the general design procedure, the final part of the thesis shows a step by step design example and demonstrates the results of applying the proposed control architecture to the nonlinear bicycle model. We highlight some problems that can arise when the bicycle is started far from the path. To overcome these problems we develop the concept of a virtual path, which is a path that when followed returns the bicycle to the actual path. We also recognize that, in practice, typical paths do not have constant curvature, so we construct more practical paths by joining straight line segments and circular arc segments, representing a practical path similar to a path that would be encountered when biking through a series of rural roads. Finally, we finish the design example by demonstrating the performance of the control architecture on such a path. From these simulations we show that using the suggested controller design that the bicycle will converge to a constant curvature path. Additionally with using the controllers we develop that in the absence of disturbance the bicycle will stay within the intended traffic lane when travelling on a typical rural road
1 edition published in 2013 in English and held by 3 WorldCat member libraries worldwide
In this thesis we investigate the problem of designing a control system for a modern bicycle so that the bicycle is stable and follows a path. We propose a multiloop control architecture, where each loop is systematically designed using linear control techniques. The proposed strategy guarantees that the bicycle asymptotically converges to paths of constant curvature. A key advantage of our approach is that by using linear techniques analysis and controller design are relatively simple. We base our control design on the nonlinear (corrected) Whipple model, which has been previously verified for correctness and experimentally validated. The equations of motion for the nonlinear model are very complicated, and would take many pages to explicitly state. They also have no known closed form solution. To enable analysis of the model we linearize it about a trajectory such that the bicycle is upright and travelling straight ahead. This linearization allows us to arrive at a parameterized linear timeinvariant statespace representation of the bicycle dynamics, suitable for analysis and control design. The innerloop control consists of a forwardspeed controller as well as a lean and steer controller. To keep the bicycle at a constant forward speed, we develop a highbandwidth proportional controller that uses a torque along the axis of the rear wheel of the bicycle to keep the angular velocity of the rear wheel at a constant setpoint. To stabilize the bicycle at this forward speed, lean torque and steer torque are treated as the control signals. We design a statefeedback controller and augment integrators to the output feedback of the lean angle and steer angle to provide perfect steadystate tracking. To arrive at the gains for state feedback, linearquadratic regulator methods are used. When following a constantcurvature path, a vehicle has a constant yaw rate. Using this knowledge, we begin designing the outerloop pathfollowing control by finding a map that converts a yaw rate into appropriate lean angle and steer angle references for the inner loop. After the map is completed, system identification is performed by applying a yawrate reference to the map and analyzing the response of the bicycle. Using the linear approximation obtained, a classical feedback controller for yawrate tracking is designed. In addition to yawrate control, to track a path the yaw angle of the bicycle must match that of the path and the bicycle must physically be on the path. To analyze these conditions a linear approximation for the distance between the bicycle to the path is found, enabling construction of a linear approximation of the entire system. We then find that by passing the signal for the difference in yaw rate and the distance through separate controllers, summing their output, and subtracting from the reference yaw rate of the path, the bicycle converges to the path. After developing the general design procedure, the final part of the thesis shows a step by step design example and demonstrates the results of applying the proposed control architecture to the nonlinear bicycle model. We highlight some problems that can arise when the bicycle is started far from the path. To overcome these problems we develop the concept of a virtual path, which is a path that when followed returns the bicycle to the actual path. We also recognize that, in practice, typical paths do not have constant curvature, so we construct more practical paths by joining straight line segments and circular arc segments, representing a practical path similar to a path that would be encountered when biking through a series of rural roads. Finally, we finish the design example by demonstrating the performance of the control architecture on such a path. From these simulations we show that using the suggested controller design that the bicycle will converge to a constant curvature path. Additionally with using the controllers we develop that in the absence of disturbance the bicycle will stay within the intended traffic lane when travelling on a typical rural road
The canadian decision to enter world war II : a case study of the foreign policy decision making process by
David Bickford(
Book
)
1 edition published in 1971 in English and held by 2 WorldCat member libraries worldwide
1 edition published in 1971 in English and held by 2 WorldCat member libraries worldwide
Shrinking body size as an ecological response to climate change by
Jennifer A Sheridan(
)
1 edition published in 2011 in English and held by 1 WorldCat member library worldwide
1 edition published in 2011 in English and held by 1 WorldCat member library worldwide
A survey of the herpetofaunal and mammalian species and the collection of avian nests and eggs in the Rio Macho Reserve of
Costa Rica by
David Bickford(
)
1 edition published in 1990 in English and held by 1 WorldCat member library worldwide
Data on the presence and estimated population sizes of the Chordata species in a Montane Wet Forest life zone of the Rio Macho Reserve is presented within this study. The study area was between Trinidad de Dota and Ojo de Aqua in the Talamancan mountains of southern Costa Rica at 2400  3200 meters above sea level
1 edition published in 1990 in English and held by 1 WorldCat member library worldwide
Data on the presence and estimated population sizes of the Chordata species in a Montane Wet Forest life zone of the Rio Macho Reserve is presented within this study. The study area was between Trinidad de Dota and Ojo de Aqua in the Talamancan mountains of southern Costa Rica at 2400  3200 meters above sea level
The state and conservation of Southeast Asian biodiversity by
Navjot S Sodhi(
)
1 edition published in 2010 in English and held by 1 WorldCat member library worldwide
1 edition published in 2010 in English and held by 1 WorldCat member library worldwide
Animal behaviour : Male parenting of New Guinea froglets by
David Bickford(
)
1 edition published in 2002 in English and held by 1 WorldCat member library worldwide
1 edition published in 2002 in English and held by 1 WorldCat member library worldwide
The War on Terrorism : role of the international community by Ethics and National Security Conference Law(
Visual
)
1 edition published in 2008 in English and held by 1 WorldCat member library worldwide
Panel III of the conference Combating Terrorism: Charting the Course for a New Administration, held April 1011, 2008, Duke University, Durham N.C
1 edition published in 2008 in English and held by 1 WorldCat member library worldwide
Panel III of the conference Combating Terrorism: Charting the Course for a New Administration, held April 1011, 2008, Duke University, Durham N.C
Conservation biology and vertebrate species diversity in a Montane West Forest ecosystem of Costa Rica by
David Bickford(
Book
)
1 edition published in 1991 in English and held by 1 WorldCat member library worldwide
1 edition published in 1991 in English and held by 1 WorldCat member library worldwide
Southeast Asian biodiversity crisis by
David Bickford(
)
1 edition published in 2012 in English and held by 1 WorldCat member library worldwide
1 edition published in 2012 in English and held by 1 WorldCat member library worldwide
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Audience Level
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