James A. Mynderse

A Psychophysical Model of Motorcycle Handlebar Vibrations

In this study, we developed a perception-based quantitative model to relate broadband vibrations transmitted through a motorcycle handlebar to a rider’s hands. The test apparatus consisted of the handlebar of a motorcycle rig assembly driven by a computer-controlled actuator. Participants were instructed to hold the handlebar and maintain a sitting posture as they would while riding a motorcycle. In Exp. 1, psychophysical detection thresholds for 10 participants were estimated at ten test frequencies between 20-300 Hz using a two-interval one-up twodown adaptive procedure. The interpolated threshold vs. frequency function specified the minimum acceleration required before a user could perceive the vibration at a particular frequency. In Exp. 2, participants were asked to rate 15 representative handlebar vibrations using a magnitude estimation procedure. The vibration patterns were measured on an actual motorcycle handlebar while the motorcycle traveled at speeds ranging from 25 to 75 mph. Several weighting functions, including the ISO-5349 standards, were applied to the broadband vibration signal in the frequency domain to estimate the total vibration energy by summing up all weighted components. The best weighting function, in the sense that the estimated total energy correlated linearly with the subjective magnitude ratings obtained in Exp. 2, were based on the detection threshold data obtained in Exp. 1. Specifically, the strength of each vibration component was calculated relative to the human detection threshold at the same frequency, thereby taking into account human sensitivity to vibration signals at different frequencies. The resulting weighting function can be applied to other recorded vibration signals to predict user rating of perceived vibration intensities.

Fostering the entrepreneurial mindset in the junior and senior mechanical engineering curriculum with a multi-course problem-based learning experience

This paper presents a multi-course problem-based learning (PBL) experience to foster the entrepreneurial mindset in the junior and senior mechanical engineering curriculum. Previous senior project students designed, fabricated, and validated a fluid-powered gantry crane that exhibited areas for improvement. To improve upon the project gantry crane, junior-and senior-level students implemented concurrent problem-based learning activities in three courses: Fluid Mechanics, Heat Transfer, and Mechatronics. Even though the PBLs targeted both technical and entrepreneurial objectives, only the results of entrepreneurial mindset attributes are discussed in this paper. Assessment results including student commentary are detailed and discussed in the paper. Preliminary results indicate extensive student practice of entrepreneurial skills.

Two-Degree-of-Freedom Hysteresis Compensation for a Dynamic Mirror Actuator

A low-computation, high-bandwidth, inverse-based hysteresis compensation and control strategy, not needing a priori knowledge of the desired trajectory, is presented. The resulting two degree-of-freedom controller is applied to a dynamic mirror with antagonistic piezoelectric stack actuation. Hysteresis compensation is performed by a finite-state machine activating polynomials for hysteresis inversion based on input signal slope. Residual error after hysteresis compensation is corrected by an LQR feedback controller. Experimental results demonstrate effectiveness of the hysteresis compensator and closed-loop system. For the input signal tested, a 91.5% reduction in hysteresis uncertainty is achieved at a 60 kHz sample rate.

Using a Funded Capstone Project to Teach Fluid Power and Advanced Mechanical Design

The A. Leon Linton Department of Mechanical Engineering at Lawrence Technological University offered a new senior capstone project to a small group of students, funded by a teaching grant from the National Fluid Power Association. All mechanical engineering students at Lawrence Tech must complete a capstone project: either an SAE competition team or a project addressing a particular industry need. The team that worked on the current project consisted of students with various concentrations in mechanical engineering and included an international visiting student from Brazil. Three faculty in Mechanical Engineering, each with different areas of expertise: thermodynamics, heat transfer, fluid mechanics and mechatronics, mentored and worked closely with the students at every step of this project. The objective of this project was to design and fabricate a classroom-scale gantry crane for material handling. The undergraduate students were not only involved in the design of a fluid powered system, but also worked on the modeling of mechanical components and the mechanical system as well as circuit design for an operator interface. The self-guided and real-world design aspect of the project increases the effectiveness of teaching by the faculty and retention of the subject by the students involved in the project.Copyright

Modeling of a Dynamic Mirror Actuator

A novel dual-actuated dynamic mirror actuator (DMA) is presented for laser beam steering. The DMA is driven by a pair of piezoelectric stack actuaors (PESAs). The piezoelectric stacks are modeled using a linear model and five variations of constitutive models from literature. The resulting DMA models are simulated. While the constitutive models capture some higher order dynamics, the linear model provides the best combination of accuracy to experimental data and simplicty of model between DC and the first natural frequency of the DMA. For control of the DMA up to the first natural frequency of the DMA, a linear model should be adequate.Copyright

DESIGN AND CONTROL OF A STEERING WHEEL VIBRATION SIMULATOR

Abstract The design and control of a steering wheel vibration simulator capable of reproducing a set of desired vibration/acceleration signals is presented. The simulator is to be used in characterizing human perception of vibration as transmitted to the hand through the steering wheel. Accelerometers were used to record the acceleration at the top of the steering wheel in both the up-down (z) and side-to-side (y) directions. A two degree-of-freedom controller was synthesized with a stabilizing feedback controller designed using linear matrix inequality techniques and a zero phase error tracking feedforward controller. Simulation and experimental results to verify key steps of the design process and the effectiveness of the simulator are presented.

Two Degree-of-Freedom Hysteresis Compensation for a Dynamic Mirror With Antagonistic Piezoelectric Stack Actuation

A methodology for designing a low-computation, high-bandwidth strategy for closed-loop control of a hysteretic system without a priori knowledge of the desired trajectory is presented. The resulting two degree-of-freedom hysteresis control strategy is applied to a dynamic mirror with antagonistic piezoelectric stack actuation. Hysteresis compensator is performed by a finite state machine switching polynomials for hysteresis inversion based on the input signal slope. Residual error after hysteresis compensation is corrected by an LQR feedback controller. Experimental results demonstrate effectiveness of the hysteresis compensator and closed-loop system under the proposed hysteresis control strategy. For the triangular input signal tested, the closed-loop system achieves a 91.5% reduction in hysteresis uncertainty with 60 kHz sample rate.Copyright

IMPROVED MODELING OF A DYNAMIC MIRROR WITH ANTAGONISTIC PIEZOELECTRIC STACK ACTUATION

An enhanced model of a dynamic mirror actuator (DMA) for laser beam steering is presented. The DMA is driven by an antagonistic pair of piezoelectric stack actuators (PESA). The proposed model of the DMA employs explicit PESA charging dynamics and an adjustable PESA shunt circuit to address the frequency-dependent effective mechanical compliance term in several previous models from literature. The proposed DMA model with shunt circuit accurately predicts the first damped natural frequency of the DMA with a shunt circuit across each PESA. Simulation and experimental data are presented. Good agreement is shown betweenthepredicted andmeasured damped first natural frequencies.

Improved Control of a Steering Wheel Vibration Simulator

The improved control of a steering wheel vibration simulator capable of reproducing a set of desired vibration/acceleration signals is presented. The simulator is to be used in characterizing human perception of vibration as transmitted to the hand through the steering wheel. Accelerometers are used to record the acceleration at the top of the steering wheel in both the up-down (z) and side-to-side (y) directions. The plant is modeled by frequency response measurements including an uncertainty model generated from measured changes in system frequency response due to variations in subject grip force. The simulator control problem is formulated as a 2-input, 1-output tracking control of the z-axis while minimizing the y-axis response. A two degree-of-freedom controller is synthesized with a stabilizing feedback controller and a zero phase error tracking feedforward controller. The feedback controller is designed using linear matrix inequality techniques and ensures robust stability of the coupled closed-loop system with uncertainty due to subject grip force. Simulation and experimental results to verify the effectiveness of the simulator are presented.Copyright

Smoothly Transitioning Between Ballistic and Corrective Control to Produce Human-Like Movement

Human reaching movement appears to consist of an initial ballistic segment that drives the hand toward the target, then a corrective segment that brings the hand into the target region. This article discusses how the motions produced by two different controllers, one guiding the ballistic portion and one directing the corrective potion, can be merged into a single smooth movement that is reminiscent of human reaching. Simulated movements based on the proposed methodology are shown to be consistent with human kinematic trajectories.Copyright