Antenna-Like Tactile Sensor for Thin-Film Piezoelectric Micro-Robots

Terrestrial and other millimeter-scale autonomous micro-robots face significant challenges in surveying their environment, due to small power budgets and payload capacities. One low-power, low-mass form of obstacle detection is tactile sensing of contact with other surfaces. In this-paper, a tactile sensor inspired by insect antennae is described, based on thin-film lead-zirconate-titanate (PZT) transduction. Thin-film piezoelectric materials permit actuation and sensing mechanisms to be coupled in very small, compact structures, as well as complement previously developed microrobotic leg mechanisms. Key design parameters for the tactile sensor are introduced and analyzed in terms of sweep frequency and range of motion, and signals from sensor impact are predicted. Experimental results with partially-released prototype actuators show respectable agreement with modeled behavior for dynamic motion, though impact detection is hampered by large feedthrough disturbances. Completed sensors range from 2 to 4 mm in length and are approximately 500 μm in width, with a sweep range of nearly 1 mm demonstrated from a 2 mm long prototype.

Computing the Stresses Induced Within Multi-Layered Elastic Media That Result From Sliding Contact With a Rigid Punch

This paper is concerned with the solution of the contact problem that results when a rigid punch is pressed into the surface of an inhomogeneously elastic solid comprising three distinct layers. The upper and lower layers of the solid are assumed to be homogeneous and are joined together by a functionally graded interlayer whose material properties progressively change from those of the coating to those of the substrate. By applying the Fourier transform to the governing boundary value problem (BVP), we may write the stresses and displacements within the solid in terms of indefinite integrals. In particular, the expressions for the horizontal and vertical displacements of the solid surface are used to formulate a coupled pair of integral equations which may be solved numerically to approximate the solution of the stamp problem. A selection of numerical results are then presented which illustrate the effects of friction on the contact problem and it is found that the presence of friction within the contact increases the magnitude of the maximum principal stress and changes its location. These observations indicate that material failure is much more likely to occur when friction is present within the contact as expected.

Lightweight Design of a Brake Caliper

As lightweight design assumes greater importance in road vehicles development, the present paper is mainly devoted to the structural optimization of a brake caliper. In the first part of the study a simplified finite element model based on beam elements of a brake caliper has been developed and validated. By using the developed model, a multi-objective optimization has been completed. The total mass of the caliper and the deformations at some critical locations have been minimised. The considered design variables are related to the shape of the caliper and the cross sections of the beam elements. The obtained optimal solutions are characterized by an asymmetric shape of the caliper. Optimised symmetric shapes currently used have been compared with the asymmetric ones in terms of performance. In the second part of the study, a detailed analysis on the optimal caliper shape has been carried out by performing a structural topology optimization. The minimum compliance problem has been solved using the SIMP (solid isotropic material with penalization) approach and the optimal solution has been compared with the ones obtained by applying the multi-objective optimization on the simplified model (beam elements). The obtained design solutions represent a good starting point for future developments in actual industrial applications.

Experimental Validation of a Volumetric Planetary Rover Wheel/Soil Interaction Model

For the multibody simulation of planetary rover operations, a wheel-soil contact model is necessary to represent the forces and moments between the tire and the soft soil. A novel nonlinear contact modelling approach based on the properties of the hypervolume of interpenetration is validated in this paper. This normal contact force model is based on the Winkler foundation model with nonlinear spring properties. To fully define the proposed normal contact force model for this application, seven parameters are required. Besides the geometry parameters that can be easily measured, three soil parameters representing the hyperelastic and plastic properties of the soil have to be identified. Since it is very difficult to directly measure the latter set of soil parameters, they are identified by comparing computer simulations with experimental results of drawbar pull tests performed under different slip conditions on the Juno rover of the Canadian Space Agency (CSA). A multibody dynamics model of the Juno rover including the new wheel/soil interaction model was developed and simulated in MapleSim. To identify the wheel/soil contact model parameters, the cost function of the model residuals of the kinematic data is minimized. The volumetric contact model is then tested by using the identified contact model parameters in a forward dynamics simulation of the rover on an irregular 3-dimensional terrain and compared against experiments.

An Investigation of the Ward Leonard System for Use in a Hybrid or Electric Passenger Vehicle

Since the early 1900’s demand for fuel efficient vehicles has motivated the development of electric and hybrid electric vehicles. Unfortunately, some components used in these vehicles are expensive and complex. Todays consumer electric vehicles use dangerously high voltage, expensive electronic controllers, complex battery management systems and AC motors. The goal of this research at BYU is to increase safety by lowering the operating voltage and decrease cost by eliminating expensive controllers and decrease the number of battery cells. This paper specifically examines the use of a Ward Leonard Motor Control system for use in a passenger vehicle. The Ward Leonard System provides an alternative control method to expensive and complex systems used today. A Control Factor metric was developed as a result of this research to measure the Ward Leonard System’s ability to reduce the size and cost of the electronic controller for application in an EV or HEV. A bench top model of the Ward Leonard system was tested validating the Control Factor metric. The Ward Leonard system is capable of reducing the controller size by 77% and potentially reducing its cost by this amount or more. This work also provides performance characteristics for automotive designers and offers several design alternatives for EV and HEV architectures allowing a reduction in voltage, the use of AC inverters, AC motors, expensive controllers and high cell count battery packs.

Sensitivity Analysis of Smoothed Particle Hydrodynamics in PAM-CRASH for Modeling of Soft Soils

The rapid progression of computational power and development of non-mesh particle modeling techniques provides solutions to problems which are not accurately modeled using traditional finite element analysis techniques. The field of soft soil modeling has been pressing on in recent years and the smoothed particle hydrodynamics (SPH) modeling method in PAM-CRASH provides opportunity for further advancement in accuracy. This research focuses on the development of soft soil models using SPH with verification using pressure-sinkage and shear strength criterion. Soil model parameters such as geometry and contact model are varied to determine the effect of the parameters on the behaviour of the soft soil and relationships are developed. The developed virtual soil models are compared against existing soils to determine which soils are accurately modeled and further refinements are made to validate the models with existing empirical data.

Training the Participatory Renaissance Man: Past Creative Experiences and Collaborative Design

Students are frequently trained in a variety of methodologies to promote their creativity in the collaborative environment. Some of the training and methods work well, while others present challenges. A collaborative stimulation approach is taken to extend creative cognition to collaborative creativity, providing new insights into design methodologies and training. An experiment using retrospective protocol analysis, originally conducted to identify the various types of collaborative stimulation, revealed how diversity of past creative experiences correlates with collaborative stimulation. This finding aligns with previous research. Unfortunately, many current engineering design education programs do not adequately provide opportunities for diverse creative experiences. As this study and other research has found, there is a need to create courses in engineering design programs which encourage participation in diverse creative activities.

A Pillar of Mechanical Engineering Design Education in Australia: 25 Years of the Warman Design and Build Competition

The “Warman Design and Build Competition”, running across Australasian Universities, is now in its 26th year in 2013. Presented in this paper is a brief history of the competition, documenting the objectives, yearly scenarios, key contributors and champion Universities since its beginning in 1988. Assuming the competition has reached the majority of mechanical and related discipline engineering students in that time, it is fair to say that this competition, as a vehicle of the National Committee on Engineering Design, has served to shape Australasian engineering education in an enduring way. The philosophy of the Warman Design and Build Competition and some of the challenges of running it are described in this perspective by its coordinator since 2003. In particular, the need is for the competition to work effectively across a wide range of student group ability. Not every group engaging with the competition will be competitive nationally, yet all should learn positively from the experience. Reported also in this paper is the collective feedback from the campus organizers in respect to their use of the competition as an educational experience in their classrooms. Each University participating uses the competition differently with respect to student assessment and the support students receive. However, all academic campus organizer responses suggest that the competition supports their own and their institutional learning objectives very well. While the project scenarios have varied widely over the years, the intent to challenge 2nd year university (predominantly mechanical) engineering students with an open-ended statement of requirements in a practical and experiential exercise has been a constant. Students are faced with understanding their opportunity and their client’s value system as expressed in a scoring algorithm. They are required to conceive, construct and demonstrate their device with limited prior knowledge and experience, and the learning outcomes clearly impact their appreciation for teamwork, leadership and product realization.

The Development of a Longitudinal Control System for a Sports-Utility-Vehicle

A common problem with sports-utility-vehicles is the low rollover threshold, due to a high center of gravity. Instead of modifying the vehicle to increase the rollover threshold, the aim of the control system is to prevent the vehicle from exceeding speeds that would cause the vehicle to reach its rollover threshold. The aim of the autonomous longitudinal control system, discussed here, is to improve the vehicle’s safety by controlling the vehicle’s longitudinal behavior. In order to develop a control system that autonomously controls the longitudinal degree of freedom, an experimentally validated mathematical model of the test vehicle (a 1997 Land Rover Defender 110 Wagon) was used — the model was developed in MSC.ADAMS/View. The control system was developed by generating a reference speed that the vehicle must track. This reference speed was formulated by taking into account the vehicle’s limits due to lateral acceleration, combined lateral and longitudinal acceleration and the vehicle’s performance capabilities. The MSC.ADAMS/View model of the test vehicle was used to evaluate the performance of the control system on various racetracks for which the GPS coordinates were available. The simulation results indicate that the control system performed as expected by limiting the vehicle’s acceleration vector to the prescribed limits.

Online Implementation of the Delta Design Game for Analyzing Collaborative Team Practices

Over the past four years the authors have developed an online version of the Delta Design game, a board game which was developed by Bucciarelli (1) to teach students design collaboration skills. In the online version, players move tiles on a shared virtual board and communicate only through text chat. In addition, the objective functions are computed automatically each time a tile is moved, so the focus of the game changes from rapid number-crunching to negotiation. Since every state of the board, along with micro-level team performance and chat data, are captured, the resulting corpus from 38 four-player team games provides a rich resource to explore different aspects of collaborative team practices. This paper gives an overview of the online implementation of Delta Design and discusses the findings from user studies including several undergraduate capstone design classes. Observations of the board-moving tactics show that teams planning a strategy before starting the game or players sharing details about their role’s constraints with other team members do not have much effect on the game’s outcome. Finally, this paper demonstrates that the complex rules of the Delta Design game make it a suitable candidate for analyzing collaboration strategies in team-based design projects.