Sensing apparatus

A sensing apparatus for determining relative amounts of force applied to a sensing surface at a plurality of locations, the sensing apparatus comprising:

• a capacitive sensor element comprising the sensing surface, wherein the capacitive sensor element is moveably mounted relative to a frame of the sensing apparatus;
• a displacement sensor element for detecting changes in the displacement of the capacitive sensor element relative to the frame;
• capacitive sensing circuitry coupled to the capacitive sensor element and configured to determine locations for a plurality of objects capacitively coupled to the sensing surface;
• displacement sensing circuitry coupled to the displacement sensor element and configured to determine changes in the displacement of the capacitive sensor element relative to the frame at a plurality of different locations due to displacement loads applied by the plurality of objects on the sensing surface;
• and
• processing circuitry configured to determine a location at which a net displacement load acts on the sensing surface from the determined changes in displacement of the capacitive sensor element relative to the frame for the plurality of different locations, and to establish relative amounts of the net displacement load applied by respective ones of the plurality of objects based on the determined locations of the objects relative to the determined location at which the net displacement load acts on the sensing surface;
• wherein the processing circuitry is configured to establish relative amounts of the net displacement load applied by the respective ones of the objects by solving at least three simultaneous equations representing a balancing of components of projections of the apportioned loads on the sensing surface about the location at which the net displacement load acts in a first direction and a second orthogonal direction respectively, and by imposing the relationship that the net displacement load is equal to the summation of all relative amounts of the net displacement load;
• and
• wherein, when the plurality of objects is N, N being an integer greater than three, the processing circuitry is configured to introduce N−3 additional relationships, wherein each additional relationship is a relationship between a given object and an adjacent object.

A method for determining relative amounts of force applied to a sensing surface of a capacitive sensor element at a plurality of locations, the capacitive sensor element moveably mounted relative to a frame, the method comprising:

• determining locations for a plurality of objects capacitively coupled to the sensing surface of the capacitive sensor element;
• calculating a net displacement load based on the changes in displacement of the capacitive sensor element at a plurality of different locations due to displacement loads applied by the plurality of objects on the sensing surface;
• determining a location at which a net displacement acts on the sensing surface from the determined changes in displacement of the capacitive sensor element relative to the frame for the plurality of different locations;
• establishing relative amounts of the net displacement load applied by respective ones of the plurality of objects based upon the determined locations of the objects relative to the determined location at which the net displacement load acts on the sensing surface;
• determining distances on the sensing surface between the locations of each of the plurality of objects and the location at which the net displacement load acts;
• and
• establishing relative amounts of the net displacement load applied by the respective ones of the objects based upon the determined distances.