Combining information from parallel servo channels

• US 8,000,057 B2
• Filed: 09/09/2010
• Issued: 08/16/2011
• Est. Priority Date: 03/09/2009
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Cherubini, Giovanni, Jelitto, Jens, Tsuruta, Kazuhiro, Cideciyan, Roy D., Hutchins, Robert A., Bui, Nhan X.
• Primary Examiner(s): Sniezek; Andrew L
• Application Number:
  US12/878,704
• Publication Number:
  US 20100328803A1
• Time in Patent Office: 341 Days
• Field of Search: None
• US Class Current: 360/77.12
• CPC Class Codes: G11B 5/584 for track following on tapes

Abstract

A weighted combining scheme exploits information from two servo channels operating in parallel. A timing-based servo module comprises two synchronous servo channels coupled respectively to receive two digital servo signals read from a data tape. Both channels have outputs for an unweighted parameter estimate and for a measure of the channel reliability. A weight computation module provides first and second weight signals using the measures of channel reliability from the servo channels. An offset computation module provides first and second offset terms which are summed with the unweighted parameter estimates. Multiplying nodes receive the unweighted parameter estimates and the weight signals and outputs offset weighted parameter estimates. A summing node receives the offset weighted parameter estimates and outputs a combined offset weighted parameter estimate to a servomechanism.

Claims

1. A timing-based servo module in a linear tape drive, comprising:

a first synchronous servo channel coupled to receive a first digital servo signal read from a data tape by a servo element, the first synchronous servo channel comprising;

a first output for a first unweighted parameter estimate; and

a second output for a first measure of the channel reliability;

a second synchronous servo channel coupled to receive a second digital servo signal read from the data tape by the servo element, the second synchronous servo channel comprising;

a first output for a second unweighted parameter estimate; and

a second output for a second measure of the channel reliability;

a weight computation module operable to provide a first weight signal and a second weight signal using the measures of channel reliability from the first and second synchronous servo channel;

an offset computation module operable to provide a first offset term and a second offset term using the first and second measures of reliability and the first and second unweighted parameter estimates from the first and second synchronous servo channels;

a first summing node coupled to receive the first unweighted parameter estimate and the first offset term;

a second summing node coupled to receive the second unweighted parameter estimate and the second offset term;

a first multiplying node coupled to receive an output from the first summing node and the first weight signal and operable to output a first offset weighted parameter estimate;

a second multiplying node coupled to receive an output from the second summing node and the second weight signal and operable to output a second offset weighted parameter estimate; and

a third summing node coupled to receive the first and second offset weighted parameter estimates and operable to output a combined offset weighted parameter estimate to a servomechanism.

2. The timing-based servo module of claim 1, wherein the parameter estimate comprises a lateral position estimate.

3. The timing-based servo module of claim 1, wherein the parameter estimate comprises a tape velocity estimate.

4. The timing-based servo module of claim 1, wherein the servomechanism comprises a track-following servomechanism.

5. A data storage tape drive, comprising:

a host interface coupled to a host device and operable for transmitting and receiving commands and data to and from the host device;

a write processing module coupled to receive data to be written from the host interface;

a write channel coupled to receive processed write data from the write processing module;

a write head coupled to receive the write data from the write channel and operable to record the data onto a data tape moving past the write head, the data tape including at least one data track between a pair of servo bands;

a read head operable to read data from the data tape moving past the read head, the read head including first and second servo elements for reading servo data from the servo bands;

a read channel coupled to receive the data read by the read head;

a read processing module coupled to receive unprocessed read data from the read channel and transmit processed read data to the host interface;

a first synchronous servo channel coupled to receive a first digital servo signal read from the data tape by the first servo element, the first synchronous servo channel comprising;

a first output for a first unweighted lateral position estimate; and

a second output for a first measure of the channel reliability;

a second synchronous servo channel coupled to receive a second digital servo signal read from the data tape by the second servo element, the second synchronous servo channel comprising;

a first output for a second unweighted lateral position estimate; and

a second output for a second measure of the channel reliability;

a weight computation module operable to provide a first weight signal and a second weight signal using the measures of channel reliability from the first and second synchronous servo channel;

an offset computation module operable to provide a first offset term and a second offset term using the first and second measures of reliability and the first and second unweighted lateral position estimates from the first and second synchronous servo channels;

a first summing node coupled to receive the first unweighted lateral position estimate and the first offset term;

a second summing node coupled to receive the second unweighted lateral position estimate and the second offset term;

a first multiplying node coupled to receive an output from the first summing node and the first weight signal and operable to output a first offset weighted lateral position estimate;

a second multiplying node coupled to receive the second summing node and the second weight signal and operable to output a second offset weighted lateral position estimate; and

a third summing node coupled to receive the first and second offset weighted lateral position estimates and operable to output a combined offset weighted lateral position estimates to a track-following servomechanism.

6. A method for providing information to a track-following servomechanism from parallel channels of a timing-based servo module in a linear tape drive, comprising:

receiving a first digital servo signal read from a data tape by a first servo element associated with a first synchronous servo channel;

generating a first unweighted lateral position estimate from the first digital servo signal;

generating a first signal measure of the channel reliability from the first digital servo signal;

receiving a second digital servo signal read from the data tape by a second servo element associated with a second synchronous servo channel;

generating a second unweighted lateral position estimate from the second digital servo signal;

generating a second measure of the channel reliability from the second digital servo signal;

providing a first weight signal and a second weight signal using the measures of channel reliability from the first and second synchronous servo channel;

providing a first offset term and a second offset term using the first and second measures of reliability and the first and second unweighted lateral position estimates from the first and second synchronous servo channels;

adding the first unweighted lateral position estimate and the first offset term to generate a first sum;

adding the second unweighted lateral position estimate and the second offset term to generate a second sum;

multiplying the first sum and the first weight signal to generate a first offset weighted lateral position estimate;

multiplying the second sum and the second weight signal to generate a second offset weighted lateral position estimate;

adding the first and second offset weighted lateral position estimates to generate a combined weighted servo signal; and

transmitting the combined offset weighted lateral position estimate to a track-following servomechanism.