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Akhilesh Gulati

Quality Insider

TRIZ for Identifying Wireless Power Transfer Solutions

An example of TRIZ in real life

Published: Wednesday, May 7, 2014 - 11:20

In late 2010 an R&D lab at one of the world’s largest microprocessor manufacturers was tasked with identifying solutions to improve the effectiveness of a wireless power transfer system. This article summarizes the thought process and methods used in generating the associated problem model and how the general solution directions were identified.

Background

A wireless power system transmits electrical power “through the air,” as opposed to through a solid conductor such as wiring. As one can imagine, not being tethered to an electrical power outlet and not using batteries would be a big plus for a wide variety of electrical appliances, including computing platforms.

The R&D lab had been working on a wireless power transmission system for mobile phones where the system was designed to charge a mobile device by way of close proximity to an adapted laptop (see figure 1). More specifically, the initial design had the transmitted power emanating from the side of the laptop and received through the side of the cell phone. The system worked well for very short distances; for example, the cell phone placed right next to the laptop as seen in figure 1a. However, even this distance could be problematic. The goal was to expand the effective range of the wireless power transfer system.


Figure 1: To charge a cell phone it only needed to be placed next to the laptop

Problem modeling

One of the most important steps in problem solving is to understand the problem and state it clearly. An inaccurate model can lead one down the wrong solution path (i.e., garbage in, garbage out). In this case, engineers stated the problem constraints in simple terms, in order to increase the effective range of the system:
• The phone needed to be placed beside and very close to the adapted laptop
• If placed incorrectly, the power transfer would be substantially reduced

Before one can begin applying any of the TRIZ problem solving principles, one must know more about how this wireless power transfer occurs. The illustration in figure 2 can help us understand this relatively easily.


Figure 2: Wireless power transmission via electromagnetism

Figure 2 shows a wireless power transmission working via basic electromagnetism. An electromagnetic field has been created by passing current through a transmitter loop (i.e., primary coil). The field then passes through a receiver loop (i.e., secondary coil) and creates secondary current that is then used to charge the battery. However, as the distance between the primary coil and the secondary coil increases, the power transfer is reduced (see figure 2a).


Figure 2a: As the distance between the primary coil and secondary coil increases, the power transfer decreases.

Because it would take large round coils (approximately 30 centimeters in diameter) with their faces positioned parallel to each other to transmit and receive electromagnetic power up to several meters, coil size was determined as one of the key limiting factors. But the size of one or both of the coils was based on the size and shape of the cell phone. So, a transition was made from the specific problem (i.e., the effective operating range of the wireless power transfer system is limited) to a simplified general problem statement, which was determined by defining contradictions:
• The coils need to be large in order to transmit and receive over long distances. As a result the transmitting device (i.e., laptop) and the receiving device (i.e., cell phone) would also need to be large because of the large size of the coils.
• The coils need to be small in order to fit the small form factor of the transmitting and the receiving devices

Developing solution concepts

This was a physical contradiction: The coils need to be both large and small at the same time. Physical contradictions can be addressed by several methods in TRIZ with some of them being:
• Separation of contradictory properties in time
• Separation of contradictory properties in space
• Separation between the whole system and its parts, but letting the contradictions co-exist
• Separation based on different conditions (i.e., solve in subsystem or super-system)

 

The first solution, and certainly the most simple, was to use flip-up or fold-out coils that could be expanded, like a telescopic antenna, when power transmission was necessary. This used the first principle of separation in time. The coils would be small when not in use and would be large when in use. It would keep the system’s form factor small during battery operation and allow for effective power transfer during charging states.

Other solutions required a different level of thinking. In order to improve interaction between the system components, TRIZ suggests substance-field (su-field) modeling and standard inventive solutions (SIS). In TRIZ, various models are used that reflect the basic elements and patterns of the evolution of technological systems—in particular, building, analyzing, and transforming functional models called su-field models. The area in TRIZ that deals with these models is called SF or su-field analysis.

The functional model identified that the current and the electromagnetic field that were generated were insufficient for achieving the desired wireless power-transfer range. The components affecting this were the amount of current, the transmission coil, and the receiving coil.

To address this a su-field problem model was developed with a focus on the zone of conflict, sometimes called the zone of operation, which defines exactly where the conflict arises and when. This generic solution allowed the team to develop several solutions to improve the su-field efficiency. The solutions included:
• Tool fragmentation—increasing the number of coils along all edges of laptop and its screen (see figure 4a)
• Substance structure transformation—transition from substances having no arranged structure (placing the cell phone wherever is fine) to substances with an arranged structure (placing cell phone where we want it and when we want it, and whether permanent or temporary). Transfer the coils to the laptop case and hang the cell phone on the back of the screen when the laptop lid is open (see figure 4b), or create a phone case/sleeve that serves multiple functions (e.g., receiver antenna, phone stand, repeater) allowing that device to provide more flexibility in laptop/phone positioning (see figure 4c).
• Creating virtual transmission and receiver “loops” where one would use the laptop and phone to create an ionized loop of air around them and utilize these temporary antennas as the large elements needed for increased transmission distance.


Figure 4: Several solutions using a su-field problem model.

This is just one example of how TRIZ tools are being used by larger organizations to come up with innovative solutions.

Discuss

About The Author

Akhilesh Gulati’s picture

Akhilesh Gulati

Akhilesh Gulati has 25 years of experience in operational excellence, process redesign, lean, Six Sigma, strategic planning, and TRIZ (structured innovation) training and consulting in a variety of industries. Gulati is the Principal consultant at PIVOT Management Consultants and the CEO of the analytics firm Pivot Adapt Inc. in S. California. Akhilesh holds an MS from the University of Michigan, Ann Arbor, and MBA from UCLA, is a Six Sigma Master Black Belt and a Balanced Scorecard Professional.