Method and apparatus for track accessing using a predicted state vector

Claim 1

A method for displacing a system (SYSMOB) that is movable with respect to a carrier (DISC) of data recorded on a plurality of tracks, the system being moved by an electric motor (ML) supplied with voltage/current by a supply generator (ALIM) controlled in turn by a control voltage u(k) and including at least one data reading/writing head TEL 1 displaced on a given path from a departure track A to an arrival track B, the position x m (k) of the head (TEL 1 ) on the path being measured at predetermined sampling instants kT by a position pickup (CAPPOS), comprising (1) at each predetermined sampling instant kT, the value of the state vector XHD k/k-1 indicating the position and speed of the head (x, x) at that instant is predicted, as a function of the measured position x m (k-1) of the head and of the control voltage u(k-1), which are considered at the preceding sampling instant (k-1)T; (2) the predicted state vector XHD k/k-1 is compared with a reference state vector Wk) indicating the reference position and speed which the head (TEL 1 ) must have at the predetermined sampling instant kT; and (3) the control voltage u(k) is calculated as a function of a reference control voltage e(k) of the motor at the predetermined sampling instant kT and of the difference ε(k) between the predicted state vector XHD k/k-1 and the reference state vector Wk).

Claim 2

A method for displacing a system (SYSMOB) that is movable with respect to a carrier (DISC) of data recorded on a plurality of tracks, the system being moved by an electric motor (ML) supplied with voltage/current by a supply generator (ALIM) controlled in turn by a control voltage u(k) and including at least one data reading/writing head TEL 1 displaced on a given path from a departure track A to an arrival track B, the position x m (k) of the head (TEL 1 ) on the path being measured at predetermined sampling instants kT by a position pickup (CAPPOS), comprising (1) at each predetermined sampling instant kT, the value of the state vector XHD k/k-1 indicating the position and speed of the head (x, x) at that instant is predicted, as a function of the measured position x m (k-1) of the head and of the control voltage u(k-1), which are considered at the preceding sampling instant (k-1)T; (2) the predicted state vector XHD k/k-1 is compared with a reference state vector Wk) indicating the reference position and speed which the head (TEL 1 ) must have at the predetermined sampling instant kT; and (3) the control voltage u(k) is calculated as a function of a reference control voltage e(k) of the motor at the predetermined sampling instant kT and of the difference ε(k) between the predicted state vector XHD k/k-1 and the reference state vector Wk).

Claim 4

A method according to one of the claims 1 or 2, characterized in that the control voltage u(k) is equal to the difference between the reference control voltage e(k) and a quantity equal to the product of ε(k) and a correction matrix H T .

Claim 5

An apparatus for displacing a system that is movable with respect to a carrier of data recorded on a plurality of tracks, the system being moved by an electric motor (ML) supplied with voltage/current by a supply generator (ALIM) controlled in turn by a control voltage u(k) and including at least one data reading/writing head TEL 1 displaced on a given path from a departure track A to an arrival track B, the position x m (k) of the head (TEL 1 ) on the path being measured at predetermined sampling instants (kT) by a position pickup (CAPPOS) comprising: (a) state observation means (OBSET) for predicting the value of the state vector XHD k/k-1 at each predetermined sampling instant kT, which receives both the value of the head position x m (k-1) measured by the position pickup (CAPPOS) at the preceding sampling instant (k-1)T and the value of the control voltage u(k-1) at this same preceding sampling instant; (b) means for memorizing a reference control voltage e(k) and a reference state vector Wk) for each sampling instant kT; (c) means (COMP) for comparing the predicted state vector XHD k/k-1 with the reference state vector W(k) and for calculating the difference ε(k) between them; and (d) regulating means (MREG) calculating the control voltage u(k) as a function of the reference control voltage e(k) and of the difference ε(k) between the predicted state vector and the reference state vector.

Claim 6

An apparatus for displacing a system that is movable with respect to a carrier of data recorded on a plurality of tracks, the system being moved by an electric motor (ML) supplied with voltage/current by a supply generator (ALIM) controlled in turn by a control voltage u(k) and including at least one data reading/writing head TEL 1 displaced on a given path from a departure track A to an arrival track B, the position x m (k) of the head (TEL 1 ) on the path being measured at predetermined sampling instants (kT) by a position pickup (CAPPOS) comprising: (a) state observation means (OBSET) for predicting the value of the state vector XHD k/k-1 at each predetermined sampling instant kT, which receives both the value of the head position x m (k-1) measured by the position pickup (CAPPOS) at the preceding sampling instant (k-1)T and the value of the control voltage u(k-1) at this same preceding sampling instant; (b) means for memorizing a reference control voltage e(k) and a reference state vector Wk) for each sampling instant kT; (c) means (COMP) for comparing the predicted state vector XHD k/k-1 with the reference state vector W(k) and for calculating the difference ε(k) between them; and (d) regulating means (MREG) calculating the control voltage u(k) as a function of the reference control voltage e(k) and of the difference ε(k) between the predicted state vector and the reference state vector.