Method and apparatus for adaptive control

In a control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system comprising an estimator;

• a method for maintaining said transducer in a centered position relative to said track, said method comprising the steps of:
• reading servo data from said disc;
• calculating a position of said transducer from said servo position data;
• calculating a predicted position, velocity, and bias, from previous predicted position, velocity, bias, and control values, and current control value;
• generating a control value based on said predicted position, velocity, and bias values;
• limiting said control value to a Predetermined maximum value;
• multiplying said control value by a plant gain adjustment factor k.sub.g to generate a compensated control value;
• shifting the level of said compensated control value to a Predetermined range;
• generating a compensated control signal in response to said compensated control value;
• applying said control signal to an amplifier to drive said actuator;
• calculating an estimator error e between said measured transducer position y.sub.m and said Predicted transducer position;
• pre-calculating new predicted states for position, velocity, and bias, based on said previous predicted position, velocity, and bias, said estimator error, and said current and previous control values;
• updating said control value by replacing the previous control value with the present control value;
• repeating said method for each actuator servo interrupt.

In a control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system comprising an estimator;

• a method for maintaining said transducer in a centered position relative to said track, said method comprising the steps of:
• reading servo data from said disc;
• calculating a position of said transducer from said servo position data;
• calculating the estimator error e, according to the relations e=y.sub.m -C.sub.e .times.x=y.sub.m -x.sub.1, where x.sub.1 =predicted position, x.sub.2 =predicted velocity, and x.sub.3 =predicted bias.
• calculating a predicted position, velocity, and bias, from previous predicted position, velocity, bias, and control values, and current control value;
• generating a control value based on said predicted position, velocity, and bias values;
• limiting said control value to a predetermined maximum value;
• multiplying said control value by a plant gain adjustment factor k.sub.g to generate a compensated control value;
• shifting the level of said compensated control value to a predetermined range;
• generating a compensated control signal in response to said compensated control value;
• applying said control signal to an amplifier to drive said actuator;
• pre-calculating new predicted states for position, velocity, and bias, based on said previous predicted position, velocity, and bias, said estimator error, and said current and previous control values;
• updating said control value by replacing the previous control value with the present control value;
• repeating said method for each actuator servo interrupt.

In a control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system;

• a method for maintaining said transducer in a centered position relative to said track, said method comprising the steps of:
• reading servo data from said disc;
• calculating a position of said transducer from said servo position data;
• generating a control value based on a transfer function depending on at least one prior transducer position ym and control value u;
• limiting said control value to a predetermined maximum value;
• multiplying said limited control value by a plant gain adjustment factor k.sub.g to generate a compensated control value;
• shifting the level of said compensated control value to a predetermined range;
• generating a compensated control signal in response to said compensated control value;
• applying said control signal to an amplifier to drive said actuator;
• updating said control value by replacing the previous control value with the present control value;
• repeating said method for each actuator servo interrupt.

In a control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system;

• a method for switching among a plurality of amplifier gain modes, said method for switching comprising the steps of:
• determining a control value that will drive said actuator to a commanded position;
• switching said gain mode in response to the magnitude of the control value applied;
• adjusting said control system in response to said selected gain mode.

In a control system for a system having an electromechanical actuator responsive to a command signal, at least one position sensor for sensing actuator positional data, said position sensor being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed positional data, and a control system comprising an estimator;

• a method of adaptively calibrating a plant gain for regions of said actuator movement and for each of said position sensors, by determining a plant gain adjustment factor, said method comprising the steps of:
• commanding said actuator to a position r with a control signal u;
• generating a single-frequency sinusoid signal u.sub.s ;
• injecting said single-frequency sinusoid signal u.sub.s to said control system so that said single-frequency sinusoid is added to said control signal;
• multiplying said control signal and said added sinusoid signal by said sinusoid signal to generate a first product signal;
• measuring a position of said actuator y.sub.m based on said position sensor;
• multiplying said measured transducer position by said sinusoid value to generate a second product signal;
• low-pass filtering said first product signal to generate a first filtered signal;
• low-pass filtering said second product signal to generate a second filtered signal;
• dividing said second filtered signal by said first filtered signal to generate an identification ratio Q proportional to the measured plant gain;
• dividing said identification ratio Q by a nominal identification ratio Q.sub.nominal to determine a new calibrated plant gain adjustment factor k.sub.g ;
• replacing a previous plant gain adjustment factor by said new calibrated plant gain adjustment factor;
• multiplying said control signal u by said new calibrated plant gain adjustment factor k.sub.g to obtain a compensated control signal u.sub.a ;
• whereby said control system is able to automatically compensate for plant bias forces as well as adapt to changes in effective plant gain.

A rotating disc storage apparatus having data stored in tracks thereon, said device comprising:

• means for transducing said stored data into a data signal;
• an electro-mechanical actuator movable in response to a control signal, said actuator being mechanically linked to said means for transducing so that said means for transducing is moved from one of said plurality of tracks to another of said plurality of tracks in response to said control signal;
• means for controlling said actuator, said means for controlling generating said control signal which characteristics depend on an adjustable plant gain;
• means for estimating an actuator position, a actuator velocity, and an actuator bias from a measured transducer position and a control signal;
• means for generating a sum signal from an addition of a single-frequency sinusoid to said control signal;
• means for modulating said sum signal with said single-frequency sinusoid to generate a modulated control signal;
• means for modulating said measured transducer position with said single-frequency sinusoid to generate a modulated position signal;
• a low-pass filter for extracting low-frequency components of said modulated control and said modulated position signals;
• means for comparing a ratio of said low-pass filtered modulated control signal to said low-pass filtered modulated position signal to generate a plant gain adjustment factor;
• means for adjusting a gain characteristic of said means for estimating and said means for controlling in response to said plant gain adjustment factor.

A system having an electro-mechanical assembly movable between a plurality of positions in response to a control signal, said system comprising:

• means for measuring said assembly position;
• means for controlling said assembly, said means for controlling generating said control signal having characteristics depend on an on-line adjustable plant gain;
• means for estimating an assembly position, an assembly velocity, and an assembly bias from said measured assembly position and said control signal;
• means for generating a sum signal from an addition of a single-frequency sinusoid to said control signal;
• means for modulating said sum signal with said single-frequency sinusoid to generate a modulated control signal;
• means for modulating said measured actuator position with said single-frequency sinusoid to generate a modulated position signal;
• a low-pass filter for extracting low-frequency components of said modulated control and said modulated position signals;
• means for comparing a ratio of said low-pass filtered modulated control signal to said low-pass filtered modulated position signal to generate a plant gain adjustment factor;
• means for adjusting a gain characteristic of said means for controlling in response to said plant gain adjustment factor.

In a sampled-data control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system comprising an estimator;

• a method of adaptively calibrating a plant gain for regions of said disc and for each of said transducers, by determining a plant gain adjustment factor, said method comprising the steps of:
• commanding said actuator to a position r with a control signal u;
• generating a single-frequency sinusoid signal u.sub.s ;
• injecting said single-frequency sinusoid signal u.sub.s to said control system so that said single-frequency sinusoid is added to said control signal;
• combining said control signal u and said single-frequency sinusoidal signal u.sub.s to generate a corrected control signal u.sub.c ;
• multiplying said control signal and said added sinusoid signal by said sinusoid signal to generate a first product signal;
• measuring a position of said transducer y.sub.m ;
• multiplying said measured transducer position by said sinusoid value to generate a second product signal;
• low-pass filtering said first product signal to generate a first filtered signal;
• low-pass filtering said second product signal to generate a second filtered signal;
• dividing said second filtered signal by said first filtered signal to generate an identification ratio Q proportional to the measured plant gain;
• determining a new calibrated plant gain adjustment factor k.sub.g, said factor being an inverse function of said identification ratio Q;
• replacing a previous plant gain adjustment factor by said new calibrated plant gain adjustment factor;
• multiplying said control signal u by said new calibrated plant gain adjustment factor k.sub.g to obtain an adjusted control signal u.sub.s ;
• wherein each of said signals is a sampled data signal;
• wherein said control system automatically compensates for plant bias forces and for changes in effective plant gain.

In a hybrid analog and digital control system for a magnetic disc storage device comprising an electromechanical actuator responsive to a command signal, at least one magnetizable rotating disc having disc track position data encoded magnetically thereupon, at least one transducer proximate said rotating disc surface for sensing said magnetic positional data, said transducer being mechanically linked to said actuator and generating a signal related to a measured position y.sub.m in response to said sensed magnetic positional data, and a control system comprising an estimator;

• a method of adaptively calibrating a plant gain for regions of said disc and for each of said transducers, by determining a plant gain adjustment factor, said method comprising the steps of:
• commanding said actuator to a position r with a control signal u;
• generating a single-frequency sinusoid signal u.sub.s ;
• injecting said single-frequency sinusoid signal u.sub.s to said control system so that said single-frequency sinusoid is added to said control signal;
• combining said control signal u and said single-frequency sinusoidal signal u.sub.s to generate a corrected control signal u.sub.c ;
• multiplying said control signal and said added sinusoid signal by said sinusoid signal to generate a first product signal;
• measuring a position of said transducer y.sub.m ;
• multiplying said measured transducer position by said sinusoid value to generate a second product signal;
• low-pass filtering said first product signal to generate a first filtered signal;
• low-pass filtering said second product signal to generate a second filtered signal;
• dividing said second filtered signal by said first filtered signal to generate an identification ratio Q proportional to the measured plant gain;
• determining a new calibrated plant gain adjustment factor k.sub.g, said factor being an inverse function of said identification ratio Q;
• replacing a previous plant gain adjustment factor by said new calibrated plant gain adjustment factor;
• multiplying said control signal u by said new calibrated plant gain adjustment factor k.sub.g to obtain an adjusted control signal u.sub.s ;
• wherein said control system automatically compensates for plant bias forces and for changes in effective plant gain.