Abstract: Friction existing between any two surfaces having relative motion is nonlinear, multiform, and is difficult to model. Nonlinear friction in the actuator pivot of a hard disk drive (HDD) limits the low frequency gain, which prevents the system positioning accuracy from further improvement. This problem is much more pronounced for the severe nonlinearity at the micrometer level. The conventional two-mode proximate time optimal servomechanism (PTOS) is inadequate for immediate future hard disk drives because of the existence of restrictions in the particular design approach. A triple-mode control scheme, and its variations, as presented herein, include (a) a proximate time-optimal controller (PTOC) having a relatively large output is used for track seeking, (b) a robust compensator having a relatively small output is used for track following to compensate for friction and other nonlinearities, and (c) a bridging (connection) control to guarantee the continuity of the control signals.

Abstract: In servomechanisms, like for example used in disk drives, disturbances, for example, friction, shock and vibration, prevent the system positioning accuracy from further improvement. These disturbances occur in a relatively low-frequency range compared to the electrical dynamics. In the present invention, an acceleration feedback control loop using a frequency-separated acceleration soft sensor (350) replaces the conventionally used current control loop in the low frequency range, where the disturbances occur, so as to attenuate the influence of the disturbances enclosed in the loop. The current feedback continues to manage the electrical dynamics in the high-frequency range. Estimating the required acceleration signal by a soft sensor (350) eliminates the need for physical accelerometers, which reduce system reliability and increase system cost.

Abstract: A ripple suppressor/compensator useful in the general area of motion control and applicable to a wide range of servomechanisms exhibiting a force ripple characteristics, including the permanent magnet linear motors. An adaptive feed-forward control signal is generated which compensates for the ripple force, thus allowing for more precise tracking performance to be achieved.

Abstract: A predictive and self-tuning PI controller includes an apparatus for variably assigning gains thereto in accordance with specified time functions following a change in set-point. The control gains are computed in accordance with a plurality of input parameters and subsequently continuously adjusted to set-point errors based on a GPC approach thereby to optimize performance indices derived from simple and classical user specifications. Variation and tuning of control gains in accordance with set-point errors permits the PI controller to be useful in the general area of process control and applicable to a wider range of processes compared to traditional PI control, including time-delay processes, unstable processes and processes with time-varying dynamics.

Abstract: This invention provides a novel process identification and control package for high performance. For process identification, a simple yet effective and robust identification method is presented using process step responses to give a continuous transfer function with time-delay without iteration. A new relay, called cascade relay, is devised to get more accurate and reliable points on the process frequency response. For controller tuning, the internal model principle is employed to design single-loop controller PID or high-order types with best achievable control performance. The process identification and control design parts can be easily integrated into control system auto-tuning package. Further, a general control scheme for disturbance rejection is given which can significantly improve disturbance rejection performance over conventional feedback systems with time delays. Practical issues such as noises, real-time implementation and tuning guidelines are also provided.

Abstract: Friction existing between any two surfaces having relative motion is nonlinear, multiform, and is difficult to model. Nonlinear friction in the actuator pivot of a hard disk drive (HDD) limits the low frequency gain, which prevents the system positioning accuracy from further improvement. This problem is much more pronounced for the severe nonlinearity at the micrometer level. The conventional two-mode proximate time optimal servomechanism (PTOS) is inadequate for immediate future hard disk drives because of the existence of restrictions in the particular design approach. A triple-mode control scheme, and its variations, as presented herein, include (a) a proximate time-optimal controller (PTOC) having a relatively large output is used for track seeking, (b) a robust compensator having a relatively small output is used for track following to compensate for friction and other nonlinearities, and (c) a bridging (connection) control to guarantee the continuity of the control signals.

Abstract: A simple yet effective and robust identification method is presented using process step responses for process identification that can provide a continuous transfer function with time-delay without iteration. A cascade relay provides accurate and reliable more points on the process frequency response. The internal model principle is employed to design single-loop controller of PID or high-order types with best achievable control performance for controller tuning, e.g. both single and multivariable cases are covered. The process identification and control design portions can be easily integrated into a control system auto-tuning package. Further, a general control scheme for disturbance rejection is given which can significantly improve disturbance rejection performance over conventional feedback systems with time delays. Practical issues such as noises, real-time implementation and tuning guidelines are also provided.

Abstract: A ripple suppressor/compensator useful in the general area of motion control and applicable to a wide range of servomechanisms exhibiting a force ripple characteristics, including the permanent magnet linear motors. An adaptive feed-forward control signal is generated which compensates for the ripple force, thus allowing for more precise tracking performance to be achieved.