Abstract: An apparatus comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: model a response of a motor to a drive signal using one or more filters, the one or more filters configured to define a range of expected motor behaviour associated with the drive signal; compare the modelled response with an actual response of the motor to the drive signal; and identify a motor error if the actual response of the motor is outside the range of expected motor behaviour defined by the modelled response.