Browse Prior Art Database

State Space Intercept Algorithm for Maximum Seek Performance

IP.com Disclosure Number: IPCOM000114384D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Bui, NX: AUTHOR [+3]

Abstract

A method for directly calculating the exact force to return to an optimum deceleration profile is disclosed. The non-linear calculation, based on a digitally sampled position and velocity states, allows for maximum seek performance within the hardware constraints.

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State Space Intercept Algorithm for Maximum Seek Performance

      A method for directly calculating the exact force to return to
an optimum deceleration profile is disclosed.  The non-linear
calculation, based on a digitally sampled position and velocity
states, allows for maximum seek performance within the hardware
constraints.

      The motion of an actuator during a seek can be described by a
graph showing the actuator position and velocity at every moment in
time (Fig. 1).  The fastest seek possible between two tracks, given
acceleration and speed constraints, is described by a unique path on
the velocity/position graph.  Non-linearities and disturbances due to
shock and vibration will disrupt the seek motion and cause the
velocity and position of the actuator to deviate from the optimum
path.  The function of the seek control system is to return the
actuator to the desired path in order to minimize the seek time.

      Many excellent techniques and algorithms exist for exercising
this control of the actuator, i.e., determining an appropriate
acceleration to apply to the actuator in order to reintercept the
optimum path.  Most of these techniques are based on linear control
methods.  However, the exact solution is a nonlinear equation, due to
the square root term.  The equation in Fig. 2 shows the exact
solution for the case of negligible friction in a sampled system.
The calculation is easily implemented by a digital controller; it can
usually be...