A comparative study of multilayered and single layered neural network based predictive controllers

The authors compare the performance of two types of controllers one based on the multilayered network and the other based on the single layered CMAC network (cerebellar model articulator controller). The neurons (information processing units) in the multi-layered network use Gaussian activation functions. The control scheme which is considered is a predictive control algorithm, along the lines used by Willis et al. (1991), Kambhampati and Warwick (1991). The process selected as a test bed is a continuous stirred tank reactor. The reaction taking place is an irreversible exothermic reaction in a constant volume reactor cooled by a single coolant stream. This reactor is a simplified version of the first tank in the two tank system given by Henson and Seborg (1989).

Simplified PID self-tuning controller for robotic manipulators

The paper describes a self-tuning adaptive PID controller suitable for use in the control of robotic manipulators. The scheme employs a simple recursive estimator which reduces the computational effort to an acceptable level for many applications in robotics.

Chaos in high performance digital robot controllers

Active robot force control requires some form of dynamic inner loop control for stability. The author considers the implementation of position-based inner loop control on an industrial robot fitted with encoders only. It is shown that high gain velocity feedback for such a robot, which is effectively stationary when in contact with a stiff environment, involves problems beyond the usual caveats on the effects of unknown environment stiffness. It is shown that it is possible for the controlled joint to become chaotic at very low velocities if encoder edge timing data are used for velocity measurement. The results obtained indicate that there is a lower limit on controlled velocity when encoders are the only means of joint measurement. This lower limit to speed is determined by the desired amount of loop gain, which is itself determined by the severity of the nonlinearities present in the drive system.

Cognitive process modelling of controllers in en route air traffic control

In recent years, various efforts have been made in air traffic control (ATC) to maintain traffic safety and efficiency in the face of increasing air traffic demands. ATC is a complex process that depends to a large degree on human capabilities, and so understanding how controllers carry out their tasks is an important issue in the design and development of ATC systems. In particular, the human factor is considered to be a serious problem in ATC safety and has been identified as a causal factor in both major and minor incidents. There is, therefore, a need to analyse the mechanisms by which errors occur due to complex factors and to develop systems that can deal with these errors. From the cognitive process perspective, it is essential that system developers have an understanding of the more complex working processes that involve the cooperative work of multiple controllers. Distributed cognition is a methodological framework for analysing cognitive processes that span multiple actors mediated by technology. In this research, we attempt to analyse and model interactions that take place in en route ATC systems based on distributed cognition. We examine the functional problems in an ATC system from a human factors perspective, and conclude by identifying certain measures by which to address these problems. This research focuses on the analysis of air traffic controllers' tasks for en route ATC and modelling controllers' cognitive processes.

A model-based PID controller for Hammerstein systems using B-spline neural networks

In this paper, a new model-based proportional–integral–derivative (PID) tuning and controller approach is introduced for Hammerstein systems that are identified on the basis of the observational input/output data. The nonlinear static function in the Hammerstein system is modelled using a B-spline neural network. The control signal is composed of a PID controller, together with a correction term. Both the parameters in the PID controller and the correction term are optimized on the basis of minimizing the multistep ahead prediction errors. In order to update the control signal, the multistep ahead predictions of the Hammerstein system based on B-spline neural networks and the associated Jacobian matrix are calculated using the de Boor algorithms, including both the functional and derivative recursions. Numerical examples are utilized to demonstrate the efficacy of the proposed approaches.

B-spline neural networks based PID controller for Hammerstein systems

A new PID tuning and controller approach is introduced for Hammerstein systems based on input/output data. A B-spline neural network is used to model the nonlinear static function in the Hammerstein system. The control signal is composed of a PID controller together with a correction term. In order to update the control signal, the multistep ahead predictions of the Hammerstein system based on the B-spline neural networks and the associated Jacobians matrix are calculated using the De Boor algorithms including both the functional and derivative recursions. A numerical example is utilized to demonstrate the efficacy of the proposed approaches.

Electrical stimulation for trunk control in paraplegia:A feasibility study

Paraplegic subjects lack trunk stability due to the loss of voluntary muscle control.This leads to a restriction of the volume of bi-manual workspace available,and hence has a detrimental impact on activities of daily living. Electrical Stimulation of paralysed muscles can be used to stabilize the trunk, but has never been applied in closed loop for this purpose. This paper describes the development of two closed loop controllers(PID and LQR),and their experimental evaluation on a human subject. Advantages and disadvantages of the two are discussed,considering a potential use of this technology during daily activities.

People or machines? Assessing the impacts of smart meters and load controllers in Italian office spaces

Government initiatives in several developed and developing countries to roll-out smart meters call for research on the sustainability impacts of these devices. In principle smart meters bring about higher control over energy theft and lower consumption, but require a high level of engagement by end-users. An alternative consists of load controllers, which control the load according to pre-set parameters. To date, research has focused on the impacts of these two alternatives separately. This study compares the sustainability impacts of smart meters and load controllers in an occupied office building in Italy. The assessment is carried out on three different floors of the same building. Findings show that demand reductions associated with a smart meter device are 5.2% higher than demand reductions associated with the load controller.

The 'veil' of control: exploring the attitudes and perceptions of UK design controllers

In the UK, architectural design is regulated through a system of design control for the public interest, which aims to secure and promote ‘quality’ in the built environment. Design control is primarily implemented by locally employed planning professionals with political oversight, and independent design review panels, staffed predominantly by design professionals. Design control has a lengthy and complex history, with the concept of ‘design’ offering a range of challenges for a regulatory system of governance. A simultaneously creative and emotive discipline, architectural design is a difficult issue to regulate objectively or consistently, often leading to policy that is regarded highly discretionary and flexible. This makes regulatory outcomes difficult to predict, as approaches undertaken by the ‘agents of control’ can vary according to the individual. The role of the design controller is therefore central, tasked with the responsibility of interpreting design policy and guidance, appraising design quality and passing professional judgment. However, little is really known about what influences the way design controllers approach their task, providing a ‘veil’ over design control, shrouding the basis of their decisions. This research engaged directly with the attitudes and perceptions of design controllers in the UK, lifting this ‘veil’. Using in-depth interviews and Q-Methodology, the thesis explores this hidden element of control, revealing a number of key differences in how controllers approach and implement policy and guidance, conceptualise design quality, and rationalise their evaluations and judgments. The research develops a conceptual framework for agency in design control – this consists of six variables (Regulation; Discretion; Skills; Design Quality; Aesthetics; and Evaluation) and it is suggested that this could act as a ‘heuristic’ instrument for UK controllers, prompting more reflexivity in relation to evaluating their own position, approaches, and attitudes, leading to better practice and increased transparency of control decisions.