News Column

"Methods, Devices and Systems for Determining the Zero Rate Output of a Sensor" in Patent Application Approval Process

August 28, 2014

By a News Reporter-Staff News Editor at Politics & Government Week -- A patent application by the inventors SHENG, Hua (Gaithersburg, MD); COOK, Bryan C. (Silver Spring, MD); LIBERTY, Matthew G. (Gaithersburg, MD), filed on February 10, 2014, was made available online on August 14, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Hillcrest Laboratories, Inc.

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention describes bias tracking techniques, systems, software and devices, which can be used in 3D pointing devices, as well as in other types of devices.

"Technologies associated with the communication of information have evolved rapidly over the last several decades. Television, cellular telephony, the Internet and optical communication techniques (to name just a few things) combine to inundate consumers with available information and entertainment options. Taking television as an example, the last three decades have seen the introduction of cable television service, satellite television service, pay-per-view movies and video-on-demand. Whereas television viewers of the 1960s could typically receive perhaps four or five over-the-air TV channels on their television sets, today's TV watchers have the opportunity to select from hundreds, thousands, and potentially millions of channels of shows and information. Video-on-demand technology, currently used primarily by cable TV operators and in hotels, provides the potential for in-home entertainment selection from among thousands of movie titles.

"The technological ability to provide so much information and content to end users provides both opportunities and challenges to system designers and service providers. One challenge is that while end users typically prefer having more choices rather than fewer, this preference is counterweighted by their desire that the selection process be both fast and simple. Unfortunately, the development of the systems and interfaces by which end users access media items has resulted in selection processes which are neither fast nor simple. Consider again the example of television programs. When television was in its infancy, determining which program to watch was a relatively simple process primarily due to the small number of choices. One would consult a printed guide which was formatted, for example, as series of columns and rows which showed the correspondence between (1) nearby television channels, (2) programs being transmitted on those channels and (3) date and time. The television was tuned to the desired channel by adjusting a tuner knob and the viewer watched the selected program. Later, remote control devices were introduced that permitted viewers to tune the television from a distance. This addition to the user-television interface created the phenomenon known as 'channel surfing' whereby a viewer could rapidly view short segments being broadcast on a number of channels to quickly learn what programs were available at any given time.

"Despite the fact that the number of channels and amount of viewable content has dramatically increased, the generally available user interface, control device options and frameworks for televisions has not changed much over the last 30 years. Printed guides and their on-screen equivalent are still the most prevalent mechanism for conveying programming information. The multiple button remote control with up and down arrows is still the most prevalent channel/content selection mechanism. The reaction of those who design and implement the TV user interface to the increase in available media content has been a straightforward extension of the existing selection procedures and interface objects. Thus, the number of rows in the printed guides has been increased to accommodate more channels. The number of buttons on the remote control devices has been increased to support additional functionality and content handling, e.g., as shown in FIG. 1. However, this approach has significantly increased both the time required for a viewer to review the available information and the complexity of actions required to implement a selection. Arguably, the cumbersome nature of the existing interface has hampered commercial implementation of some services, e.g., video-on-demand, since consumers are resistant to new services that will add complexity to an interface that they view as already too slow and complex.

"Some attempts have also been made to modernize the screen interface between end users and media systems. However, these attempts typically suffer from, among other drawbacks, an inability to easily scale between large collections of media items and small collections of media items. For example, interfaces which rely on lists of items may work well for small collections of media items, but are tedious to browse for large collections of media items. Interfaces which rely on hierarchical navigation (e.g., tree structures) may be speedier to traverse than list interfaces for large collections of media items, but are not readily adaptable to small collections of media items. Additionally, users tend to lose interest in selection processes wherein the user has to move through three or more layers in a tree structure. For all of these cases, current remote units make this selection processor even more tedious by forcing the user to repeatedly depress the up and down buttons to navigate the list or hierarchies. When selection skipping controls are available such as page up and page down, the user usually has to look at the remote to find these special buttons or be trained to know that they even exist. Accordingly, organizing frameworks, techniques and systems which simplify the control and screen interface between users and media systems as well as accelerate the selection process, while at the same time permitting service providers to take advantage of the increases in available bandwidth to end user equipment by facilitating the supply of a large number of media items and new services to the user have been proposed in U.S. patent application Ser. No. 10/768,432, filed on Jan. 30, 2004, entitled 'A Control Framework with a Zoomable Graphical User Interface for Organizing, Selecting and Launching Media Items', the disclosure of which is incorporated here by reference.

"Of particular interest for this specification are the remote devices usable to interact with such frameworks, as well as other applications and systems. As mentioned in the above-incorporated application, various different types of remote devices can be used with such frameworks including, for example, trackballs, 'mouse'-type pointing devices, light pens, etc. However, another category of remote devices which can be used with such frameworks (and other applications) is 3D pointing devices. The phrase '3D pointing' is used in this specification to refer to the ability of an input device to move in three (or more) dimensions in the air in front of, e.g., a display screen, and the corresponding ability of the user interface to translate those motions directly into user interface commands, e.g., movement of a cursor on the display screen. The transfer of data between the 3D pointing device and another device, e.g., which generates a user interface, may be performed wirelessly or via a wire connecting the 3D pointing device that device. Thus '3D pointing' differs from, e.g., conventional computer mouse pointing techniques which use a surface, e.g., a desk surface or mousepad, as a proxy surface from which relative movement of the mouse is translated into cursor movement on the computer display screen. An example of a 3D pointing device can be found in U.S. Pat. No. 7,118,518 to Matthew G. Liberty (hereafter referred to as the '518 patent), the disclosure of which is incorporated here by reference.

"The '518 patent describes 3D pointing devices which include, for example, one or two rotational sensors and an accelerometer. The rotational sensor(s) are used, as described in more detail below, to detect an angular rate at which the 3D pointing device is being rotated by a user. However, the output of the rotational sensor(s) does not perfectly represent the angular rate at which the 3D pointing device is being rotated due to, for example, bias (also sometimes referred to as 'offset') in the sensor(s)' outputs. For example, when the 3D pointing device is motionless, the rotational sensor(s) will typically have a non-zero output due to their bias. If, for example, the 3D pointing device is used as an input to a user interface, e.g., to move a cursor, this will have the undesirable effect of cursor drifting across the screen when the user intends for the cursor to remain stationary. Thus, in order to provide a 3D pointing device which accurately reflects the user's intended movement, estimating and removing bias from sensor output is highly desirable. Moreover other devices, in addition to 3D pointing devices, may benefit from being able to estimate and compensate for the bias of inertial sensors. Making this process more challenging is the fact that the bias is different from sensor to sensor and, even for individual sensors, is time-varying, e.g., due to changes in temperature.

"Accordingly, there is still room for improvement in the area of bias estimation and handheld device design, generally, and 3D pointer design, more specifically."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventors' summary information for this patent application: "According to exemplary embodiments, an adaptive ZRO (Zero-Rate Output)-tracking filter for an angular rate sensor uses the shared recursive computation architecture of the standard Kalman filter, a cumulative moving-average filter, and an exponential moving-average filter, but the gain is adaptively modified as the mixed function of Kalman gain, cumulative moving-average coefficient, and exponential moving-average coefficient. Constraints are enforced on the predicted estimate covariance used in the Kalman gain computation to revise the gain accordingly. Such mixed functions and constraints can vary over time, particularly as a function of the ZRO estimate convergence. Such exemplary embodiments combine both advantages taken from an averaging filter and an unconstraint Kalman filter, provide quicker convergence to the true ZRO value even during motion of the device, and produce almost no backlash after convergence. Exemplary embodiments are also capable of distinguishing between constant-speed human motion of the device and a device which is stationary, i.e., without intended motion but with a non-zero output due to sensor bias.

"According to one exemplary embodiment, a device includes: at least one sensor configured to sense rotation of the device about a first axis and to generate at least one first output associated therewith, and a ZRO filter configured to receive the at least one first output and to compensate the at least one first output for a bias associated with the at least one sensor, wherein the ZRO filter is implemented in a Kalman filter form having at least one dynamic constraint enforced on at least one parameter associated therewith.

"According to another exemplary embodiment, a device includes at least one sensor configured to sense rotation of the device about a first axis and to generate at least one first output associated therewith, and a ZRO filter configured to receive the at least one first output and to compensate the at least one first output for a bias associated with the at least one sensor, wherein the ZRO filter is implemented as an adaptive combination of a Kalman filter and a moving average filter.


"The accompanying drawings illustrate exemplary embodiments, wherein:

"FIG. 1 depicts a conventional remote control unit for an entertainment system;

"FIG. 2 depicts an exemplary media system in which exemplary embodiments can be implemented;

"FIG. 3 shows a 3D pointing device in which exemplary embodiments can be implemented;

"FIG. 4 illustrates a cutaway view of the 3D pointing device in FIG. 4 including two rotational sensors and one accelerometer;

"FIG. 5 shows another 3D pointing device in which exemplary embodiments can be implemented;

"FIG. 6 depicts the 3D pointing device of FIG. 5 being used as part of a '10 foot' interface;

"FIG. 7 illustrates a system block diagram which takes angular velocity sensor data and uses a ZRO filter to compensate that data according to an exemplary embodiment;

"FIG. 8 is a flow diagram illustrating operation of a ZRO filter according to an exemplary embodiment;

"FIG. 9 is a flow diagram illustrating one of the steps of the flow diagram in FIG. 8 in more detail;

"FIG. 10 is a flow diagram illustrating another one of the steps of the flow diagram in FIG. 8 in more detail;

"FIG. 11 is a state machine illustrating convergence confidence factors and running phases associated with a ZRO filter according to an exemplary embodiment;

"FIG. 12 is a state machine illustrating how two instances of a same ZRO filter with different initializations interact with each other and a corresponding state machine according to an exemplary embodiment;

"FIG. 13 is an extension of the exemplary embodiment of FIG. 12; and

"FIG. 14 illustrates a hardware architecture associated with an exemplary device in which the present invention can be implemented."

URL and more information on this patent application, see: SHENG, Hua; COOK, Bryan C.; LIBERTY, Matthew G. Methods, Devices and Systems for Determining the Zero Rate Output of a Sensor. Filed February 10, 2014 and posted August 14, 2014. Patent URL:

Keywords for this news article include: Hillcrest Laboratories Inc.

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Source: Politics & Government Week

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