Exhaust system, controller and method for an internal combustion engine

An exhaust system for exhausting combustion gases from an internal combustion engine, the exhaust system comprising:

• an exhaust conduit for conveying exhaust gases from the internal combustion engine;
• a particulate filter for filtering particulates from the exhaust gases conveyed by the exhaust conduit;
• a supply inlet arranged to introduce gas into the particulate filter to promote regeneration, the supply inlet being disposed upstream of the particulate filter and downstream of a catalytic convertor;
• a control valve for controlling the supply of gas to the particulate filter to control regeneration;
• and
• a controller configured to control the control valve to control regeneration of the particulate filter, the controller being configured to:
• determine a particulate loading of the particulate filter;
• and
• output a control signal to control the control valve to control regeneration of the particulate filter in dependence on the determined particulate loading;
• wherein the controller is configured to compare the determined particulate loading to a predetermined first loading threshold;
• wherein the control signal comprises an open valve request to open the control valve and a fuel cut request to inhibit the supply of fuel to the engine, both in dependence on a determination that the particulate loading is greater than the first loading threshold;
• wherein the controller is configured to compare the determined particulate loading to a predetermined second loading threshold, the second loading threshold being greater than zero and less than the first loading threshold;
• wherein the control signal comprises a close valve request to close the control valve in dependence on a determination that the particulate loading is less than the second loading threshold;
• and
• wherein the controller is configured to compare the determined particulate loading to a predetermined third loading threshold, and when the determined particulate loading decreases to the third loading threshold or below, to reinstate the supply of fuel to the engine.