Dose control system for injectable-drug delivery devices and associated methods of use

A dose control system configured for an injectable drug delivery device, the drug delivery device comprising a substantially elongate drug delivery body, at least one injectable drug held by the body, the body having a distal and proximal extremity, and a rotatable dose setting wheel located at a proximal extremity of said drug delivery body, rotatable about a longitudinal axis of said drug delivery body, wherein the dose control system comprises:

• a substantially disk-shaped diametral single-dipole magnet removably attachable, or permanently fixed, to the rotatable dose setting wheel at the proximal extremity of said drug delivery body;
• a housing removably attachable to the proximal extremity of the drug delivery body, the removably attachable housing comprising:
• at least a first and a second magnetic field measurement means configured to measure the magnetic field produced by the substantially disk-shaped diametral single-dipole magnet, wherein the at least first and second magnetic field measurement means are magnetometers, wherein the magnetometers are disposed in displaced axial alignment to an axis of rotation of the magnet;
• an integrated control unit connected to the at least first and second magnetic field measurement means configured to process information received from the at least first and second magnetic field measurement means;
• an integrated processing unit configured to correct magnetic field values measured by the at least first and second magnetic field measurement means and resulting from a lack of axial alignment of the at least first and second magnetic field measurement means with the substantially disk-shaped diametral single-dipole magnet by applying a rotation about the axis of rotation to a pseudo-vector representing a resultant pseudo-magnetic field calculated from the measured magnetic fields of said first and second magnetic field measurement means to bring said pseudo-vector into an iso-normal projection plane, wherein the at least first and second magnetic field measurement means are configured to measure the magnetic field produced by the substantially disk-shaped diametral single-dipole magnet via determination of a rotational movement of the substantially disk-shaped diametral single-dipole magnet and without determination of an axial position of the substantially disk-shaped diametral single-dipole magnet;
• wherein:
• the at least first and second magnetic field measurement means are located in the removably attachable housing in a displaced axial relationship relative to the longitudinal axis of the drug delivery body and the substantially disk-shaped diametral single-dipole magnet;
• the substantially disk-shaped diametral single-dipole magnet is configured to co-rotate with said dose setting wheel around the longitudinal axis of the drug delivery body;
• and
• the integrated control unit is further configured to:
• calculate offset values for said at least first and second magnetic field measurement means from a series of points generated by corresponding vectors of the measured magnetic fields resembling a sphericized cloud of points in three dimensions,
• provide a normalized vector with regard to the displaced axial relationship of the at least first and second magnetic field measurement means, said normalized vector being derived from the measured magnetic field generated by the rotation of the substantially disk-shaped diametral single-dipole magnet and measured by the at least first and second magnetic field measurement means, and
• calculate a dose setting from said normalized vector.