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A. Bradshaw

Bio: A. Bradshaw is an academic researcher from Lancaster University. The author has contributed to research in topics: Mechatronics & Control theory. The author has an hindex of 5, co-authored 13 publications receiving 138 citations.

Papers
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Proceedings ArticleDOI
01 Jan 1996
TL;DR: A new control system structure is presented, which makes the realisation of adaptive, flexible real-time systems possible and its implementation in case of robot control system using the latest T9000 transputer technology.
Abstract: This paper presents a new control system structure, which makes the realisation of adaptive, flexible real-time systems possible and outlines its implementation in case of robot control system using the latest T9000 transputer technology. The modules of the example system developed for robot control communicate to each other by message passing, which made the system development and its further modification much easier and faster.

58 citations

Journal ArticleDOI
01 Jul 1996-Robotica
TL;DR: A novel selective partial-state feedback control law is made for swing-up control of double inverted pendulum systems that is not at all sensitive to uncertainties such as modelling error and sensor noise, and is both reliable and robust.
Abstract: In Part I a technique for the swing-up control of single inverted pendulum system is presented. The requirement is to swing-up a carriage mounted pendulum system from its natural pendent position to its inverted position. It works for all carriage balancing single inverted pendulum systems as the swing-up control algorithm does not require knowledge of the system parameters. Comparison with previous swing-up controls shows that the proposed swing-up control is simpler, eaiser. more efficient, and more robust. In Part II the technique is extended to the case of the swing-up control of double inverted pendulum systems. Use is made of a novel selective partial-state feedback control law. The nonlinear, open-loop unstable, nonminimum-phase. and interactive MIMO pendulum system is actively linearised and decoupled about a neutrally stable equilibrium by the partial-state feedback control. This technique for swing-up control is not at all sensitive to uncertainties such as modelling error and sensor noise, and is both reliable and robust.

41 citations

Journal ArticleDOI
01 Jul 1996-Robotica
TL;DR: The feasibility of matching human performance is considered, and it is concluded that the necessary power and energy requirements can be fitted within the mass and volume of the human body.
Abstract: This paper investigates the feasibility of constructing a humanoid robot using existing technology. Firstly, the adoption of the humanoid form is justified. The structure, strength and power capabilities of a human are analysed in engineering terms, and taken to represent the requirements specification for a humanoid robot. Technological alternatives to the biological components are reviewed and compared to this specification. The feasibility of matching human performance is considered, and it is concluded that the necessary power and energy requirements can be fitted within the mass and volume of the human body.

22 citations

Proceedings ArticleDOI
05 Sep 1994
TL;DR: The paper outlines one architecture which has been developed for the control of a robotic excavator and compares it with the architecture adopted for an intelligent paper roll manipulator and certain of the problems of achieving the required level of autonomy within the specified environments are identified.
Abstract: The development of intelligent autonomous and semi-autonomous systems capable of operating safely in unstructured environments such as those outlined above will to a significant degree be dependent on the achievement on the levels of system integration and the transfer of functionality between the mechanical, electronic and software domains suggested by mechauonics. In particular, the system must be structured around an architecture which is capable of accommodating a range and variety of machine geometries and operational modes and which is also capable of supporting the associated sensing and safety requirements. The paper outlines one such architecture which has been developed for the control of a robotic excavator and compares it with the architecture adopted for an intelligent paper roll manipulator. Both these architectures are based around a goal oriented approach with the selection and organisation of the individual tasks necessary to achieve the desired goal left to the system. The extension of these architectures to incorporate the safety requirements for operation in an unstructured environment in association with other items of plant and machinery and with humans is also considered along with associated sensing requirements. From these considerations, certain of the problems of achieving the required level of autonomy within the specified environments are identified.

9 citations

Proceedings ArticleDOI
01 Sep 1998
TL;DR: In this article, a real-time flexible, transputer based robot control system has been developed at Lancaster University, which has been used to compare the effectiveness of two control algorithms: 1) the multivariable version of the most frequently used proportional-integral (PI) control, and 2) the newer pseudo-derivativefeedback (PDF) control.
Abstract: At Lancaster University a real-time flexible, transputer based robot control system has been developed. This paper describes how this founding has been used to compare the effectiveness of two control algorithms: 1) the multivariable version of the most frequently used proportional-integral (PI) control, and 2) the multivariable version of the newer pseudo-derivative-feedback (PDF) control. Both controllers were analysed and their gain values were tuned using an approximate block diagonalisation technique. The paper develops, analyses and compares these two robot control methods for the selected Dainichikiko PT600 robot arm. The step responses of both controllers were simulated by parallel control software running on two T9000 transputers. The results obtained show that the PDF controller is faster, less sensitive to plant parameter variations and its disturbance rejection characteristics are much better, than that of the PI controller.

5 citations


Cited by
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Journal ArticleDOI
01 Jun 2001
TL;DR: This work proposes a method for formulating the problem of the smooth hip motion with the largest stability margin using only two parameters, and derive the hip trajectory by iterative computation.
Abstract: Biped robots have better mobility than conventional wheeled robots, but they tend to tip over easily. To be able to walk stably in various environments, such as on rough terrain, up and down slopes, or in regions containing obstacles, it is necessary for the robot to adapt to the ground conditions with a foot motion, and maintain its stability with a torso motion. When the ground conditions and stability constraint are satisfied, it is desirable to select a walking pattern that requires small torque and velocity of the joint actuators. We first formulate the constraints of the foot motion parameters. By varying the values of the constraint parameters, we can produce different types of foot motion to adapt to ground conditions. We then propose a method for formulating the problem of the smooth hip motion with the largest stability margin using only two parameters, and derive the hip trajectory by iterative computation. Finally, the correlation between the actuator specifications and the walking patterns is described through simulation studies, and the effectiveness of the proposed methods is confirmed by simulation examples and experimental results.

859 citations

Journal ArticleDOI
TL;DR: This study conducts systematic phylogenetic analyses of 26 families of transport systems that either had not been characterized previously or were in need of updating, and presents partial multiple alignments, signature sequences and phylogenetic trees for them all.

239 citations

Proceedings ArticleDOI
Wei Zhong1, H. Rock
05 Sep 2001
TL;DR: In this paper, the design of a nonlinear controller for the double inverted pendulum (DIP) system consisting of two inverted pendulums mounted on a cart is considered.
Abstract: The paper considers the design of a nonlinear controller for the double inverted pendulum (DIP), a system consisting of two inverted pendulums mounted on a cart. The swingup controller bringing the pendulums from any initial position to the unstable up-up position is designed based on passivity properties and energy shaping. While the swingup controller drives the DIP into a region of attraction around the unstable up-up position, the balance controller designed on the basis of the linearized model stabilizes the DIP at the unstable equilibrium. The simulation results show the effectiveness of the proposed nonlinear design method for the DIP system.

158 citations

Proceedings ArticleDOI
02 Jun 1999
TL;DR: In this paper, a servo design technique is proposed which can control the pivot acceleration considering a limited travel of the pivot, and this control law is applied to the swing-up control problem for an inverted pendulum.
Abstract: The mechanical energy of a pendulum whose pivot can move horizontally can be controlled according to signs of the pivot acceleration values. A servo design technique is proposed which can control the pivot acceleration considering a limited travel of the pivot. This control law is applied to the swing-up control problem for an inverted pendulum.

106 citations

Patent
26 Oct 2006
TL;DR: In this article, a computing arrangement for identification of a current temporal input against one or more learned signals is presented, where each core comprises properties having at least some statistical independency from other of the computational, the properties being set independently of each other core, each core being able to independently produce an output indicating recognition of a previously learned signal.
Abstract: A computing arrangement for identification of a current temporal input against one or more learned signals. The arrangement comprising a number of computational cores, each core comprises properties having at least some statistical independency from other of the computational, the properties being set independently of each other core, each core being able to independently produce an output indicating recognition of a previously learned signal, and at least one decision unit for receiving the produced outputs from the number of computational cores and making an identification of the current temporal input based the produced outputs.

81 citations