Dr. Tan's DVERG

Our research focuses on understanding fundamental issues in dynamics, vibration and energy with applications to automotive, biomechanical, civil and mechanical systems. Recent research projects are summarized as follows and sample publications are available for download.

  1. Novel Applications of Sensors and Smart Materials with Energy Harvesting to Improve Physical Rehabilitation and Mobility
  2. Energy Flow and Microvibration Mitigation in Ultrasonic Metal Welding
  3. A Novel Video-Assisted Integrated Approach for Enhancing Bridge Health Monitoring
  4. Other major publications

Contact: Dr. Chin-An Tan

Novel applications of sensors and smart materials with energy harvesting to improve physical rehabilitation and mobility

Investigators:   

  • Heather Lai* and Chin An Tan, Department of Mechanical Engineering
  • Sujay Galen and Allon Goldberg, Department of Healthcare Sciences
  • Yong Xu, Department of Electrical and Computer Engineering

* Heather Lai is currently a Lecturer with the Department of Biomedical Engineering

Sponsors:

WSU Office of Research, WSU Graduate School

Studies have shown that continuing physical and occupational rehabilitation beyond the hospital stay is strongly tied with positive outcomes for patients suffering from a wide range of ailments, including stroke, neurological and musculoskeletal disorders, and bone fractures. These patients often require intensive, complex, repetitive motion tasks to promote new connections in the brain. In many cases, patients must be willing and able to perform sometimes complex, repetitive motions as a part of their activities of daily living without having the benefits of a trained professional providing guidance and encouragement to complete the regimen properly, which has been found to be a large impediment for many patients. Telerehabilitation has thus played a vital role in patient recovery and provides an efficient means to support non-invasive and pervasive services demanded by future healthcare environments.

While exercise compliance with high intensity physical therapy throughout the entire recuperation period is an essential contributor to positive recovery, in order for telerehabilitation to be effective, wearable rehabilitation devices must be comfortable, easy to put on and wear for long periods of time without bulky electronics and batteries. One significant challenge for this development is the lack of a sustainable power source that can be integrated into the wearable devices. The objectives of this research are to: i) develop comfortable, inconspicuous, wearable energy harvesting devices using smart materials to reduce dependence on batteries; ii) improve in-home rehabilitation assessment through wireless data collection and monitoring and transform the applications of telerehabilitation; and iii) improve mobility for patients by mimicking biological muscular behavior.  These objectives will be achieved through a multifaceted approach including modeling, laboratory testing, and clinical assessment on human subjects. On-going research includes: i) model the energy harvesting capacity of emerging elastomer polymers and develop innovative approaches to increase their capacity, including use of graphene-based conducting electrodes; ii) develop mutualistic energy harvesting techniques without increased fatigue on the wearer; iii) characterize gait variations due to the energy harvesting using advanced simulation tools such as OpenSim. Future work includes: i) develop a wireless monitoring system of lower limb movement by 3D accelerometersto improve exercise compliance; and ii) validate the wireless monitoring system using a 3D motion analysis system.

Our long-term goal is to incorporate actuation, sensing, and energy harvesting capabilities of smart materials into the development of flexible, wearable telerehabilitative and health monitoring devices. Our research will advance fundamental understanding of energy harvesting capability of emerging polymer materials in medical applications, and development of beneficial energy harvesting techniques by minimizing the metabolic expenditures on the wearer. The research is thus innovative as it establishes a pathway for the integration of energy harvesting into the field of telerehabilitation, providing comfortable, inconspicuous, wearable devices designed to allow in-home rehabilitation assessment and guidance to be performed continually throughout the course of the day, integrating physical therapy into the patient activities of daily living, and increasing the quality of the rehabilitation and long-term positive outcomes.

A short movie on the effects of charging and discharging dielectric polymeric materials.

Selected publications:

Energy flow and microvibration mitigation in ultrasonic metal welding

Investigators:   

  • Chin An Tan, Wayne State University
  • Bongsu Kang, Indiana University Purdue University Fort Wayne
  • Wayne Cai, General Motors R & D

Sponsor:      

General Motors R & D

Ultrasonic metal welding is a process to join dissimilar metals by applying ultrasonic vibrations (at frequencies greater than 20 kHz) at their interfaces. The objectives of this research are to develop fundamental understanding of the dynamic characteristics and novel microvibration mitigation techniques for ultrasonic welding systems. The test platform for validation of our research is the ultrasonic welding of battery tabs for electric vehicles. Ultrasonic metal welding for battery tabs must be performed with 100% reliability in battery pack manufacturing as the failure of a single weld essentially results in a battery that is inoperative or cannot deliver the required power due to the electrical short caused by the failed weld. In ultrasonic metal welding processes, high-frequency ultrasonic energy is used to generate an oscillating shear force (sonotrode force) at the interface between a sonotrode and few metal sheets to produce solid-state bonds between the sheets clamped under a normal force. These forces, which influence the power needed to produce the weld and the weld quality, strongly depend on the mechanical and structural properties of the weld parts and fixtures in addition to various welding process parameters such as weld frequencies and amplitudes.

The following figure shows a schematic of an ultrasonic metal welding setup for welding of battery tabs of an inter-cell unit (ICU) of a battery pack. Typically, hundreds of ICUs are connected through interconnect boards (ICB) for conduction of electricity in the battery pack. The unidirectional vibration of the sonotrode (horn), at 10 to 30 microns, transmits vibration energy to soften the materials at the interfaces, resulting in a solid-state bonding between the metals through progressive shearing and plastic deformation. During a welding process, portions of the vibration energy may travel through the complex system and cause unwanted vibrations which could result in poor welds. With a stringent 100% reliability requirement for battery tab welding and a steady increase in the demand of EVs and PHEVs (projected 9.6 million vehicles by 2018), robust joining methods are desirable to ensure reliable and safe operations of batteries.

  

Figure. Schematic of an ultrasonic metal welding setup (left); an exploded view of ICU (right).

Selected publications:

  • Kang, B., Cai, W., and Tan, C. A., “Dynamic Response of Battery Tabs Under Ultrasonic Welding,” ASME Journal of Manufacturing Science and Engineering, 2013, accepted for publication.
  • Kang, B., Cai, W., and Tan, C. A., “Vibrational Energy Loss Analysis of Battery Bus-Bar in Ultrasonic Welding,” submitted for referred journal publication.

A novel video-assisted integrated approach for enhancing bridge health monitoring

Investigators:   

  • Chin An Tan and George Yin, Wayne State University
  • Maria Q. Feng, Columbia University

Sponsor:          

National Science Foundation (completed project)

The nation’s civil infrastructure systems such as bridges are aging and deteriorating. This deterioration is due to various reasons including fatigue failure caused by repetitive traffic loads, environmental effects, and extreme events. As a result, these infrastructures are becoming increasingly vulnerable to natural and man-made disasters such as earthquakes, hurricanes, and terrorist attacks. Emergency management of and coping with crisis situations that arise from catastrophic failures of infrastructures have emerged as one of the most critical challenges to modern society.

In long-term health monitoring of bridge structures, system identification is often performed based on the measured response or system output, and knowledge of the input (traffic excitation) is either unknown or limited, making it very difficult to obtain an accurate assessment of the state of the bridge structures. The focus of this research was to develop an innovative video-assisted approach to significantly improve the capability of long-term structural health monitoring of bridge structures.  In particular, basic information of vehicle types, arrival times and speeds were extracted from video images to develop physics-based simulation models for parameter identification algorithms. Research tasks included: (1) the development and installation of a video system on an instrumented bridge for real-time imaging of vehicle information; (2) the development of real-time algorithms on a chip for processing and streaming data; (3) the development of physics-based traffic excitation models suitable for improved parameter identification algorithms; and (4) validation on an instrumented bridge. This research soughtto provide a broad foundation for innovative applications of imaging tools in the development of physics-based bridge health monitoring concepts.  

   

Figure. Captured video images of a vehicle travelling on the bridge.

Selected publications: