Absolute position readout apparatus

An absolute position readout apparatus comprising an encoder device and a readout device that are spaced apart from each other, said encoder device being rotatable relative to said readout device in a rotary direction about an axis;

• wherein said encoder device includes an absolute magnetic track and an incremental magnetic track which are disposed concentrically and side-by-side and each of which extends in the rotary direction;
• wherein said absolute magnetic track has a plurality of absolute-track magnetized regions which form a plurality of absolute-track boundaries thereamong, said absolute-track boundaries being formed equidistantly along the rotary direction with an angular distance between each adjacent two thereof being 2A which defines an angular width of each of said absolute-track magnetized regions;
• wherein said incremental magnetic track has a plurality of first incremental-track magnetized regions with first magnetic polarity and a plurality of second incremental-track magnetized regions with second magnetic polarity which differs from the first magnetic polarity, said first incremental-track magnetized regions and said second incremental-track magnetized regions being arranged alternately and forming a plurality of incremental-track boundaries thereamong, said incremental-track boundaries being formed equidistantly along the rotary direction with an angular distance between each adjacent two thereof being A which defines an angular width of each of said first and second incremental-track magnetized regions, said absolute-track magnetized regions thereby being wider than said first and second incremental-track magnetized regions;
• wherein, for each of said absolute-track boundaries, a closest one of said incremental-track boundaries is spaced apart therefrom by an angular distance of a in a displacement direction same as or opposite to the rotary direction, where a 0≤α≤2A;
• when α=0, said absolute-track boundary is aligned with said closest one of said incremental-track boundaries in a radial direction with respect to the axis;
• wherein said readout device includes:
• a group of first magnetic sensing components that correspond to said absolute magnetic track, and that are arranged equidistantly along the rotary direction with an angular distance between each adjacent two thereof being 2A;
• a group of second magnetic sensing components that correspond to said absolute magnetic track, wherein said first magnetic sensing components and said second magnetic sensing components are arranged alternately along the rotary direction and adjacent ones thereof are spaced apart from each other by an angular distance of A;
• a third magnetic sensing component that corresponds to said incremental magnetic track, and that is spaced apart from a closest one of said first and second magnetic sensing components by an angular distance of a in the displacement direction;
• and
• a fourth magnetic sensing component that corresponds to said incremental magnetic track, and that is spaced apart from said third magnetic sensing component along the rotary direction by an angular center-to-center distance of (N−0.5)×A, where N is a positive integer;
• and
• wherein, when α=0, said third magnetic sensing component is aligned with one of said first magnetic sensing components and said second magnetic sensing components in the radial direction.