Charles Burton Theurer

A Self-Energized Sensor for Wireless Injection Mold Cavity Pressure Measurement: Design and Evaluation

This paper presents the modeling, design, and experimental validation of a self-energizedsensor system for pressure measurement in the injection mold cavity using ultrasound asthe information carrier. The sensor extracts energy from the polymer melt pressure anddiscretizes the pressure information into ultrasonic pulses for wireless transmissionthrough the mold to a remote receiver. Analytical and numerical models are presented forthree constituent components of the sensor: the energy converter, the threshold modulator,and the signal transmitter. Quantitative results were obtained to guide the parametricdesign of each constituent component. Simulations and experimental studies have vali-dated the functionality of each individual component, as well as the sensor as an inte-grated unit. In addition to the injection mold pressure measurement, the sensing techniquedeveloped is applicable in a broad range of process monitoring applications where highpressure fluctuations occur. @DOI: 10.1115/1.1767850#

Design of ultrasonic transmitters with defined frequency characteristics for wireless pressure sensing in injection molding

This paper describes a new mechanical wireless data transmission technique using ultrasonic waves as the information carrier for on-line injection mold cavity pressure measurement. Ultrasonic transmitters with specific frequency characteristics were designed, modeled, simulated, and prototyped for pressure data retrieval from an enclosed machine environment, as well as for sensor identification in a sensor matrix configuration. The effects of the front layer and bonding layer of the transmitter on the overall sensor frequency characteristics were investigated, using an equivalent circuit model. The optimal layer thickness was determined for the design of transmitters with specific dominant resonant frequency and narrow bandwidth. Experimental results were in good agreement with the analysis, thus confirming the design approach.

Analytic Wavelet-Based Ultrasonic Pulse Differentiation for Injection Mold Cavity Pressure Measurement

A new signal processing technique has been developed for detecting and differentiating timely overlapped ultrasonic pulse trains that carry spatially distributed pressure information across an injection mold cavity. The new technique is based on wavelet transform using analytic wavelets. Compared to conventional wavelets that have a constant relative bandwidth at all the scales, the analytic wavelets investigated in this paper feature variable relative bandwidth, making it possible to simultaneously match the frequency characteristics of the ultrasonic pulse trains transmitted from the mold-embedded pressure sensors. As a result, more accurate detection and differentiation of the temporal and spectral information embedded within the ultrasonic pulse trains could be achieved. A theoretical framework for the analytic wavelet transform was established, and the performance of three analytic wavelets was comparatively studied. Subsequently, a multi-channel ultrasonic pulse detector based on the complex Morlet wavelet was designed and experimentally investigated. The results have confirmed the effectiveness of the new signal processing technique for on-line pressure sensing in injection molding process monitoring.

Passive charge modulation for a wireless pressure sensor

A wireless pressure sensor is described for use in a high-pressure manufacturing process with three major subsystems: energy conversion by a stack of piezoelectric disks, energy measurement and control by a threshold modulator, and ultrasonic signal transmission by a piezoelectric transmitter. The second system, the threshold modulator, is the focus of this paper. The charge, proportional to pressure, on a capacitive element is measured and controlled through the use of a two-transistor modulator. Standard NPN and PNP transistors are used to passively control the flow of charge between a piezoelectric stack and an ultrasonic transmitter. The basis for the design is discussed, from which a simulation is developed and compared to a bench top prototype. The results of this comparison indicate the appropriateness of the assumptions used to produce an analytical model of the design and the limiting conditions under which the modulator will effectively measure charge. Finally, the prototype device is optimized with respect to sensitivity, gain, and operating range for use in real-time process monitoring and control.

Self-energized wireless pressure sensor using energy extraction from injection mold pressure differential

With the prolific use of sensors for manufacturing process monitoring and the growing demand for system integration, the issue of packaging and installation has assumed an increasingly central role. This paper presents the design of a self-energized pressure sensor that extracts energy from the pressure differential of the polymer melt during the injection molding process. A piezoelectric element is used as the energy converter to convert the high melt pressure into proportional electrical charges, which in turn, actuate an ultrasound signal through a miniature energy switch. Based on predetermined energy threshold values, the actuator generates a train of ultrasound pulses, which represent the continuous melt pressure in a digitized form. The ultrasound pulses propagate wirelessly through the mold steel and are detected by a remotely located signal receiver. Through multiplication of the number of pulses with the energy threshold values, the polymer melt pressure profile is reconstructed. To enable a self-energized sensor design, an analytical study has been conducted to establish a quantitative relationship between the polymer melt pressure and the energy that can be extracted through the use of a piezoelectric converter.

Self-powered sensing for mechanical system condition monitoring

A self-powered wireless sensing module for the condition monitoring of mechanical systems and high energy manufacturing processes is described, with injection molding as a special application. The design and analysis of three constituent components in such a sensing module: an energy converter consisting of a piezoceramic stack, an energy regulator based on a pair of bipolar transistors, and a piezoelectric transmitter that transmits ultrasound signals proportional to the pressure within the injection mold, are presented in this paper. The energy extraction mechanism is investigated based on the interactions between the mechanical strain and the electric field developed within the piezoceramic stack. Analytical models for the energy modulator and signal transmitter are also established. Quantitative results are obtained that describe the energy flow among the three components and guide the parametric design of the three constituent components. Simulations and experimental studies have validated the functionality of each component. The models established can be used to subsequently optimize the design of the entire sensor module in terms of minimizing the energy requirement for the sensor and identifying the minimum level of signal intensity required to ensure successful detection of the signal by the signal receiver on the outside of the injection mold. The proposed self-powered sensing technique enables a new generation of sensors that can be employed for the condition monitoring and health diagnosis of a wide range of mechanical and civil systems that are characterized by high energy contents.

An Integrated Robotic System for Autonomous Brake Bleeding in Rail Yards

Current operations in rail yards are dangerous and limited by the operational capabilities of humans being able to perform safely in harsh conditions while maintain high productivity. Such issues call out the need for robust and capable autonomous systems. In this paper, we outline one such autonomous solution for the railroad domain, capable of performing the brake bleeding inspection task in a hump yard. Towards that, we integrated a large form factor mobile robot (the Clearpath Grizzly) with an industrial manipulator arm (Yasakawa Motoman SIA20F) to effectively detect, identify and subsequently manipulate the brake lever under harsh outdoor environments. In this paper, we focus on the system design and the core algorithms necessary for reliable and repeatable system execution. To test our developed solution, we performed extensive field tests in a fully operational rail yard with randomly picked rail cars under day and night-time conditions. The results from the testing are promising and validate the feasibility of deploying an autonomous brake bleeding solution for railyards.