Hybrid electric vehicle and method of control thereof

A controller for a hybrid electric vehicle having a powertrain comprising an engine and at least one electric machine, at least one of said at least one electric machine being operable as a propulsion motor to provide drive torque to drive the vehicle, and an energy storage device that powers the at least one electric machine as a propulsion motor,

• the controller being configured to control the engine and the at least one electric machine to provide torque to drive the vehicle in a hybrid vehicle (HV) mode in which the engine is switched on or an electric vehicle (EV) mode in which the engine is switched off, the controller being further configured to:
• monitor a value of one or more parameters associated with the vehicle;
• identify a current driving style of a driver in dependence on the value of the one or more parameters;
• calculate a value of a driver behaviour index in dependence on the driving style of the driver;
• control the powertrain to operate in the HV or EV modes in dependence on the driving style of the driver;
• control at least one of said at least one electric machines to operate as a generator to generate electrical energy for storage in the energy storage device;
• control the powertrain to operate in a torque boost mode of operation in which at least one of said at least one electric machine operates as a propulsion motor to provide drive torque to drive the vehicle in parallel with the engine;
• control the engine and the at least one electric machine in dependence on the value of the driver behaviour index thereby to prevent the amount of energy stored in the energy storage device from falling to a value preventing assumption of the torque boost mode;
• and
• prevent the value of the driver behaviour index changing in response to a value of longitudinal acceleration, when a value of lateral acceleration exceeds a prescribed value.