A review of shape memory alloy research, applications and opportunities

This book, written by two major figures in adaptive control, provides a wealth of material for researchers, practitioners, and students. While some researchers in adaptive control may note the absence of a particular topic, the book‘s scope represents a high-gain instrument. It can be used by designers of control systems to enhance their work through the information on many new theoretical developments, and can be used by mathematical control theory specialists to adapt their research to practical needs. The book is strongly recommended to anyone interested in adaptive control.

Adaptive Control

Traditional engineering instruction is deductive, beginning with theories and progressing to the applications of those theories Alternative teaching approaches are more inductive Topics are introduced by presenting specific observations, case studies or problems, and theories are taught or the students are helped to discover them only after the need to know them has been established This study reviews several of the most commonly used inductive teaching methods, including inquiry learning, problem-based learning, project-based learning, case-based teaching, discovery learning, and just-in-time teaching The paper defines each method, highlights commonalities and specific differences, and reviews research on the effectiveness of the methods While the strength of the evidence varies from one method to another, inductive methods are consistently found to be at least equal to, and in general more effective than, traditional deductive methods for achieving a broad range of learning outcomes

Inductive Teaching and Learning Methods: Definitions, Comparisons, and Research Bases

Introduction to heat transfer

Dynamic analysis of flexible manipulators, a literature review

A method for developing optimized point-to-point motion profiles to achieve fast motions with minimum vibration is presented. The proposed approach uses the well-known s-curve motion profiles, but optimizes the selection of the ramp-up (and ramp-down) time. The selection of ramp-up time is based on a frequency analysis that minimizes the excitation energy of the input forcing function at the system natural frequency. Simulation results on a lightly-damped system undergoing point-to-point motions demonstrate that the proposed approach decreases residual vibration by almost an order of magnitude over other approaches, even when the actual natural frequency is in error by 10%.

Optimized s-curve motion profiles for minimum residual vibration

Background

Case studies have been found to increase students' critical thinking and problem-solving skills, higher-order thinking skills, conceptual change, and their motivation to learn. Despite the popularity of the case study approach within engineering, the empirical research on the effectiveness of case studies is limited and the research that does exist has primarily focused on student perceptions of their learning rather than actual learning outcomes.

Purpose (Hypothesis)

This paper describes an investigation of the impact of case-based instruction on undergraduate mechanical engineering students' conceptual understanding and their attitudes towards the use of case studies.

Design/Method

Seventy-three students from two sections of the same mechanical engineering course participated in this study. The two sections were both taught using traditional lecture and case teaching methods. Participants completed pre-tests, post-tests, and a survey to assess their conceptual understanding and engagement.

Results

Results suggested that the majority of participants felt the use of case studies was engaging and added a lot of realism to the class. There were no significant differences between traditional lecture and case teaching method on students' conceptual understanding. However, the use of case studies did no harm to students' understanding while making the content more relevant to students.

Conclusions

Case-based instruction can be beneficial for students in terms of actively engaging them and allowing them to see the application and/or relevance of engineering to the real world.

Lessons Learned: Implementing the Case Teaching Method in a Mechanical Engineering Course

This paper describes an appropriately shaped forcing function for moving a dynamic system over an incremental distance with minimum residual vibration. The function is constructed by combining harmonics of a “ramped sinusoid” function so that minimum energy is introduced to the system at its resonant frequencies. A test fixture to evaluate this approach is described and experimental results are given. Residual vibration amplitudes for the ramped sinusoid function are compared with those for a square wave input and a bang-bang function. In practice, the ramped sinusoid achieves nearly an order-of-magnitude reduction in residual vibration amplitude as compared to the square wave forcing function.

Minimizing Residual Vibration for Point-to-Point Motion

Forcing functions are developed to produce vibration-free motions in flexible systems. These forcing functions are constructed from ramped sinusoid basis functions so as to minimize excitation in a range of frequencies surrounding the system natural frequency. Frequency domain attributes of a particular ramped sinusoid forcing function are compared with corresponding attributes of a minimum-energy optimal input and an impulse-filtered ramp signal. A closed-loop control system is developed that utilizes each of these forcing functions to generate a reference profile, and also feeds the particular forcing function forward directly to the system to enhance closed-loop bandwidth. The use of a direct feedforward signal in the closed-loop implementation results in significantly faster response times when the closed-loop bandwidth is otherwise constrained to be very low. Simulation results indicate that residual vibration has been nearly eliminated for all three forcing functions, even when some error in natural frequency exists. However, the ramped sinusoid input provides the most control over spectral energy near resonance and uses the least amount of energy to achieve vibration-free motions. >

Robust motion control of flexible systems using feedforward forcing functions

Since all robots have some inherent flexibility, fast motions tend to excite system vibrations. This paper develops shaped inputs that generate fast motions with minimum residual vibration. Shaped force inputs are constructed from a versine series, with coefficients of the harmonic terms chosen to maximize kinetic energy and minimize excitation energy at the system natural frequencies. These force inputs are doubly integrated to obtain position waveforms that serve as reference profiles for a closed-loop controller. A Cartesian robot is used as an experimental system to test these shaped reference inputs and to compare their responses to simple step responses. Results indicate considerable reduction in residual vibration with the shaped inputs. This is especially useful when modal coupling exists, since vibration in other axes can be prevented by driving the moving axis with shaped inputs having no excitation energy at the coupled mode frequencies.

Peter H. Meckl

Papers

Optimized s-curve motion profiles for minimum residual vibration

Lessons Learned: Implementing the Case Teaching Method in a Mechanical Engineering Course

Minimizing Residual Vibration for Point-to-Point Motion

Robust motion control of flexible systems using feedforward forcing functions

Experimental Evaluation of Shaped Inputs to Reduce Vibration for a Cartesian Robot