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Selection, Sizing and Control of Adjustable Speed Motor Drives for

Stressful and Fault Tolerant Applications

Babak Fahimi, Electro Standards Laboratories Inc.

Hamid A. Toliyat, Texas A&M University


Time:     8:00 AM - Noon and 1:00 PM - 5:00 PM

Date:    October 13th, 2002

Location:    Conference Room 'D' on Conference Level


Design and development of modern electromechanical energy conversion devices for high impact ancillary automotive and military products is of paramount importance. The performance of an electromechanical energy conversion device, as a direct link between electrical and mechanical terminals, is highly affected by input/output characteristics of thereto-connected components. Indeed, a successful operation of the auxiliary electromechanical devices requires full compatibility under the loading effects as dictated by its electrical/mechanical ends. This can be referred to as “design in the context of the application.” The loading effects on each terminal can be broadly classified into dynamic and steady state. These conditions should be taken into considerations throughout the design process viz. Selection, sizing and control of the device. We will address this important problem in the proposed tutorial.

 Furthermore, employment of adjustable speed motor drives in high impact automotive, aerospace and military applications demands for a new generation of design and control strategies well known as ˇ§fault tolerant designˇ¨. In fact, fault tolerance and enhanced survivability plays a central role in design and development of advanced auxiliary motor drives in such applications. This in turn calls for a modular configuration in respective magnetic and electronics architecture of modern motor drives. In this reference, there are several probable failures which can potentially undermine the capability of automotive motor/generator drives in providing a reliable and continuos service. This includes failures in the following parts of the system:

  1. Electric and/or magnetic components of the machine.
  2. Control electronics, Semiconductor switches, and processor.
  3. Sensors(position, current, voltage), and their respective conditioning/filtering electronics.

 In order to illustrate an entirely fault tolerant performance, a hierarchical reconfiguration of the control strategy along with corresponding hardware modification needs to be established. The main objective of such control strategy would be to:

  1. Monitor the condition of the system components. It should be capable of fast detection of any anomaly in the performance of components.
  2. Upon detection of such irregularities, the control system should disengage the faulty constituent from the system in a safe fashion.
  3. It should adopt the next best control strategy which employs the remaining resources of the system and provides the best possible performance under the given circumstances.

 The short course will focus on design and control strategies which serves the purpose of Fault tolerance as it is a vital requirement in military applications. Examples of re-organizing controllers will be demonstrated to illustrate the significance and practicality of this concept.

 Design of automotive integrated starter/generator for automotive applications, and fault tolerant assist motor drive for electrically assisted power steering are chosen to explain the details of the proposed design philosophy. These examples depict a collection of important characteristics ranging from ultra high-speed motion to near zero speed requirements for control of the drive. In order to give an insightful physical understanding of each step, we will provide theoretical proof as evidenced by measurement data. This seminar is prepared such that practicing engineers and graduate students can absorb it entirely.