Controller and control method for injection using function map

A method of controlling an injector or the like suitable for use in an internal combustion engine, the method including:

• providing a first data map having a plurality of first data map points, each of the first data map points representing a first data map output value;
• providing a function map comprising a second data map having a plurality of second data map points, each corresponding to a respective one of the first data map points, and wherein the second data map is divided into at least a first-type data map region containing second data map points representing second data map output values only of a first type and a second-type data map region containing second data map points representing second data map output values only of a second type, wherein a portion of the second data map defines a hysteresis region;
• and,
• determining an operating point on an operating path within the second data map in dependence upon first and second engine operating parameters and determining a control function for the injector based on a first data map output value determined from the first data map and the second data map output value determined from the second data map, in accordance with the following criteria:
• a) if the operating point in the second data map lies in a part of the first-type data map region which is outside the hysteresis region, the second data map output value is output from the first-type data map region and the first data map output value is interpolated from first data map output values of the first data map points adjacent to or neighbouring the first data map point corresponding to the operating point in the second data map;
• or
• b) if the operating point in the second data map lies in a part of the first-type data map region which is within the hysteresis region, then:
• i) if the operating point in the second data map entered the hysteresis region from a previous operating point on the operating path within the first-type data map region then the second data map output value is output from the first-type data map region and a first data map output value is interpolated from the first data map output values of the first data map points adjacent to or neighbouring the first data map point corresponding to the operating point in the second data map;
• but
• ii) if the operating point in the second data map entered the hysteresis region from a previous operating point on the operating path within the second-type data map region, then the second data map output value is output from the second-type data map region and the first data map output value is extrapolated from the first data map output values of the first data map points adjacent to the first data map point corresponding to the previous operating point in the second data map.