Automated servo control system

Details Automated servo control system Automated servo control system

2000-06-19

2004-02-03

Korzuch, William (Department: 2653)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S059210

Reexamination Certificate

active

06687199

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to optical drives, and more particularly to servo control in optical drives.
BACKGROUND OF THE INVENTION
The use of control systems in optical drive controllers for servo control, such as for Compact Disc (CD) and Digital Video Disc (DVD) drives, is well known in the art.
FIG. 1
illustrates the general concept of a control system. The control system
100
includes a system
102
which has a particular input. The system's output is read, and a transfer function is computed. The transfer function indicates the amount of error in the system
102
. Based upon the transfer function, a force is added to the input to modify the system's behavior. The output is read again. This process repeats until the transfer function indicates zero error in the system
102
. One skill in the art understands that the transfer function for the control system
100
is a “multiply and accumulate” function. A general format of the transfer function is as follows:
H
=&Sgr;(
a
1
b
1
)+&Sgr;(
a
2
b
2
),
Where b
1
is the input, b
2
is the accumulated output, and a
1
and a
2
are coefficients.
FIG. 2
illustrates a conventional servo control system in an optical drive controller. A digital servo control
202
typically controls the operation of the servo, via servo control processors
216
, in reading and writing data from and to an optical disc (not shown). To monitor the servo, an analog sample servo data is periodically obtained and converted to a digital format by an Analog-to-Digital Converter
204
(ADC). Conventionally, the result is a 10-bit value for any channel that the ADC
204
samples and converts. Each result of the channels are then placed into one of eight registers
206
. The processor
208
executes software instructions which reads the current contents of the registers
206
; obtains the accumulated sample data from the memory
210
, which were computed based upon past contents of the registers
206
; and computes the transfer function. The resulting accumulated sample data is then stored back in the memory
210
. Based upon the computed transfer function, a new force is applied to the servo via the servo control processors
216
. This continues until the error in the servo system equals zero. However, the execution of the software instructions require significant processor resources and time.
Some conventional methods decrease the requirements on the processor
208
by utilizing a dedicated Multiplier and Accumulator Controller (MAC)
214
for the computation of the transfer function. However, the processor
208
still must execute software instructions for reading the contents of the registers
206
; obtain the accumulated sample data from the memory
210
; write the accumulated sample data into the MAC
214
; instruct the MAC
214
to compute the transfer function; and store the results from the MAC
214
into the memory
210
. Thus, significant processor resources and time is still required.
Accordingly, there exists a need for an improved servo control system for an optical drive controller. The improved system should decrease the required processor resources and time. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention provides a method and system for servo control in an optical drive. The method includes initiating an execution of a Multiplier and Accumulator Controller (MAC) by a processor; and automatically calculating a transfer function by the MAC based upon a sample servo data. The present invention provides a servo control system which utilizes a MAC which is directly linked to the sample servo data. When a processor commands the MAC to execute, the MAC receives the sample servo directly from an Analog-to-Digital Converter (ADC); retrieves the corresponding accumulated sample servo data from a memory; calculates the transfer function; and stores the results back into the memory. The processor then accesses the memory to retrieve the result. Because the MAC is able to calculate the transfer function with minimal intervention from the processor, significant processing resources and time are saved.


REFERENCES:
patent: 4937440 (1990-06-01), Hofer et al.
patent: 5089757 (1992-02-01), Wilson
patent: 5170296 (1992-12-01), Eiberger
patent: 6388968 (2002-05-01), Ohta et al.
patent: 6490121 (2002-12-01), Pruett et al.

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