Nonlinear control of the Reaction Wheel Pendulum

In this paper we introduce the Reaction Wheel Pendulum, a novel mechanical system consisting of a physical pendulum with a rotating bob. This system has several attractive features both from a pedagogical standpoint and from a research standpoint. From a pedagogical standpoint, the dynamics are the simplest among the various pendulum experiments available so that the system can be introduced to students earlier in their education. At the same time, the system is nonlinear and underactuated so that it can be used as a benchmark experiment to study recent advanced methodologies in nonlinear control, such as feedback linearization, passivity methods, backstepping and hybrid control. In this paper we discuss two control approaches for the problems of swingup and balance, namely, feedback linearization and passivity based control. We first show that the system is locally feedback linearizable by a local diffeomorphism in state space and nonlinear feedback. We compare the feedback linearization control with a linear pole-placement control for the problem of balancing the pendulum about the inverted position. For the swingup problem we discuss an energy approach based on collocated partial feedback linearization, and passivity of the resulting zero dynamics. A hybrid/switching control strategy is used to switch between the swingup and the balance control. Experimental results are presented.

A finite volume method with linearisation in time for the solution of advection-reaction-diffusion systems

The numerical solution in one space dimension of advection--reaction--diffusion systems with nonlinear source terms may invoke a high computational cost when the presently available methods are used. Numerous examples of finite volume schemes with high order spatial discretisations together with various techniques for the approximation of the advection term can be found in the literature. Almost all such techniques result in a nonlinear system of equations as a consequence of the finite volume discretisation especially when there are nonlinear source terms in the associated partial differential equation models. This work introduces a new technique that avoids having such nonlinear systems of equations generated by the spatial discretisation process when nonlinear source terms in the model equations can be expanded in positive powers of the dependent function of interest. The basis of this method is a new linearisation technique for the temporal integration of the nonlinear source terms as a supplementation of a more typical finite volume method. The resulting linear system of equations is shown to be both accurate and significantly faster than methods that necessitate the use of solvers for nonlinear system of equations.

Automated Feedback for 'Fill in the Gap' Programming Exercises

Timely feedback is a vital component in the learning process. It is especially important for beginner students in Information Technology since many have not yet formed an effective internal model of a computer that they can use to construct viable knowledge. Research has shown that learning efficiency is increased if immediate feedback is provided for students. Automatic analysis of student programs has the potential to provide immediate feedback for students and to assist teaching staff in the marking process. This paper describes a “fill in the gap” programming analysis framework which tests students’ solutions and gives feedback on their correctness, detects logic errors and provides hints on how to fix these errors. Currently, the framework is being used with the Environment for Learning to Programming (ELP) system at Queensland University of Technology (QUT); however, the framework can be integrated into any existing online learning environment or programming Integrated Development Environment (IDE)

Program Annotations: Feedback for Students Learning to Program

This paper presents a novel program annotation mechanism which enables students to obtain feedback from tutors on their programs in a far simpler and more efficient way than is possible with, for example, email. A common scenario with beginning students is to email tutors with copies of their malfunctioning programs. Unfortunately the emailed program often bears little resemblance to the program the student has been trying to make work; often it is incomplete, a different version and corrupted. We propose an annotation mechanism enabling students to simply and easily annotate their programs with comments asking for help. Similarly our mechanism enables tutors to view students’ programs and to reply to their comments in a simple and structured fashion. This means students can get frequent and timely feedback on their programs; tutors can provide such feedback efficiently, and hence students’ learning is greatly improved.

Teacher praise and feedback and students’ perceptions of the classroom environment

The relationships between teacher praise and feedback, and students’ perceptions of the classroom environment were investigated in six rural elementary schools (n 5 747). The Teacher Feedback Scale and My Classroom Scale were developed as part of this study and used to collect the data. Structural equation modelling was used to test a hypothesised model. The results indicated that negative teacher feedback and effort feedback were both related to students’ relationships with their teachers, while ability feedback was associated with perceptions of the classroom environment. Praise was not related to classroom environment or teacher–student relationships. Significant age and gender differences were found. Additionally, differences were found between students who were satisfied with their classroom and those who were dissatisfied. Satisfied students received more general praise, general ability feedback, effort feedback and less negative teacher feedback when compared to dissatisfied students. Research studies have emphasised the influence of signicicant adults (teachers and parents) on students’ personal development (Porlier et al., 1999) and the importance of significant others’ verbal statements when directed at children (Burnett, 1996a). The relationships between negative and positive statements made by teachers, parents, peers and siblings and children’s self-talk have been investigated (Burnett, 1996a) and positive statements (praise) have been found to be more beneficial than verbal criticism (Burnett, 1999). The quality of life in the classroom in recent times has been considered of great importance to students (Thorp et al., 1994) and this is recognised by Baker (1999) who reported a relationship between students’ satisfaction with the learning environment, and differential teacher feedback and praise. This study investigated the relationships between teacher praise and feedback, and how students perceived their classroom and their relationship with their teacher.