Abstract: A method of determining an electrical angle offset of a motor position sensor mounted to a multi-phase electric motor, the method comprising rotating a rotor of the multi-phase electric motor at a motor velocity using an external drive system, measuring a motor phase voltage of each phase of the multi-phase electric motor, the motor phase voltage comprising a back-EMF generated by the rotation of the motor, converting the motor phase voltage to a DQ reference frame to form a DQ motor phase voltage and calculating the electrical angle offset from the DQ motor phase voltages.

Abstract: A method of determining an electrical angle offset of a motor position sensor mounted to a multi-phase electric motor, the method comprising rotating a rotor of the multi-phase electric motor at a motor velocity using an external drive system, measuring a motor phase voltage of each phase of the multi-phase electric motor, the motor phase voltage comprising a back-EMF generated by the rotation of the motor, converting the motor phase voltage to a DQ reference frame to form a DQ motor phase voltage and calculating the electrical angle offset from the DQ motor phase voltages.

Abstract: A motor control circuit for an electric motor of an electric power assisted steering system comprises a switching circuit comprising a plurality of electrical switches, a current demand signal generator which converts the torque demand signal into a current demands signal; and a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases.

Abstract: A control system for an electric motor comprises a current controller which produces a set of voltage demands for the motor, a current sensing means arranged to produce a current sensing output indicative of electric current in the motor, and a current signal processing means arranged to process the current sensing output signal to produce a modified current signal in which at least one harmonic component present in the current sensing output signal due to inaccuracies in the current measurement is removed or substantially reduced. The modified current signal is combined with a demanded motor current to provide the input to the current controller.

Abstract: A control strategy for an electric motor of an electric power assisted steering system of the kind in which a control means produces motor current demand signals that are fed to a motor drive means, the demand signals being dependent on the amount of assistance torque demanded from the motor, the motor drive means being arranged to cause currents to flow in each phase of the motor as required to meet the demanded assistance torque, the control strategy comprising limiting the rate of change of current that is drawn from the electrical supply of the vehicle by the motor in the event that it would otherwise exceed a threshold rate of change.

Abstract: A control system for an electric motor comprises a current controller which produces a set of voltage demands for the motor, a current sensing means arranged to produce a current sensing output indicative of electric current in the motor, and a current signal processing means arranged to process the current sensing output signal to produce a modified current signal in which at least one harmonic component present in the current sensing output signal due to inaccuracies in the current measurement is removed or substantially reduced. The modified current signal is combined with a demanded motor current to provide the input to the current controller.

Abstract: A motor control circuit for an electric motor of an electric power assisted steering system comprises a switching circuit comprising a plurality of electrical switches, a current demand signal generator which converts the torque demand signal into a current demands signal; and a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases.

Abstract: A measurement circuit includes first and second inputs for receiving first and second input signals which vary cyclically with the rotational position of a rotor of an electric motor; a phase detector circuit; and an observer circuit that estimates the frequency and phase of the first and second input signals. The phase detector circuit determines a phase difference between first and second estimated signals with a phase difference dependent on the phase difference indicated by the estimates, the first and second estimated signals varying in quadrature with each other and the first and second input signals by adding a multiplicative combination of the first input signal with the first estimated signal to a multiplicative combination of the second input signal with the second estimated signal to result in a sum signal dependent upon the phase difference, The observer circuit varies the estimates dependent upon the sum signal.

Abstract: A motor control circuit for an electric motor of an electric power assisted steering system comprises a switching circuit comprising a plurality of electrical switches, a current demand signal generator which converts the torque demand signal into a current demands signal; and a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases.

Abstract: A method of operating an electric motor of an electric power assisted steering system comprising performing the following steps when the motor is in a defined fault mode: A) monitoring the position of the motor rotor, B) identifying the presence of a condition in which the rotor is within a predefined angular range of a known angular position, the rotor moving towards that position by turning of the steering wheel, and a torque is demanded from the motor which tends to move the rotor closer to that angular position as the wheel continues to move in the identified direction of movement; C) if the condition is identified varying currents applied to the motor to cause the rotor to move away from the known angular position; and D) subsequently varying the torque demanded from the motor to cause the rotor to move back in a direction towards the known angular position.

Abstract: A method of monitoring an electric motor circuit of the kind comprising an electric motor having a plurality of phases delta configuration, a plurality of electrical switches arranged in a bridge, operable in response to signals from a controller to selectively connect the phases to a power supply, the motor controller being responsive to a current error signal dependent on the difference between a demanded motor current value and an actual motor current value indicative of the actual current flowing in the motor where the method comprising the steps of processing at least one signal that is present in use of the electric motor circuit to identify a frequency component of the at least one signal that meets certain predefined criteria and in the event that the component is identified and that it does meet the criteria providing an indication that there is a fault.

Abstract: A method of operating an electric motor of an electric power assisted steering system of the kind having a defined fault mode in which the motor is incapable of generating an output torque when the rotor is located in at least one angular position regardless of the motor torque demand output by the motor controller, the method comprising performing the following steps when the motor is known to be in the defined fault mode: A) monitoring the position of the motor rotor, B) identifying the presence of a condition in which the rotor is within a predefined angular range of the at least one known angular position, the rotor is moving towards that position due to the driver turning the steering wheel, and a torque is demanded from the motor which would tend to move the rotor closer to that angular position as the wheel continues to move in the identified direction of movement; C) in the event that the condition is identified varying the currents applied to the motor to cause the motor rotor to move away from th

Abstract: A motor control circuit for an electric motor of an electric power assisted steering system comprises a switching circuit comprising a plurality of electrical switches, a current demand signal generator which converts the torque demand signal into a current demands signal; and a fault mode motor current controller that is responsive to an error signal that represents the difference between the current demand signal and the actual current flowing in the motor and is operable in the event of a fault where one phase is open-circuit to drive the remaining two phases as a single combined phase by generating a single voltage demand signal that is representative of the voltage to be applied across the combined phases, the voltage signal being in turn fed into a drive circuit for the switches that generates pulse width modulated switching signals for the switching circuit required to apply the voltage across the combined phases.

Abstract: A method of monitoring an electric motor circuit of the kind comprising an electric motor having a plurality of phases delta configuration, a plurality of electrical switches arranged in a bridge, operable in response to signals from a controller to selectively connect the phases to a power supply, the motor controller being responsive to a current error signal dependent on the difference between a demanded motor current value and an actual motor current value indicative of the actual current flowing in the motor where the method comprising the steps of processing at least one signal that is present in use of the electric motor circuit to identify a frequency component of the at least one signal that meets certain predefined criteria and in the event that the component is identified and that it does meet the criteria providing an indication that there is a fault.

Abstract: A control strategy for an electric motor of an electric power assisted steering system of the kind in which a control means produces motor current demand signals that are fed to a motor drive means, the demand signals being dependent on the amount of assistance torque demanded from the motor, the motor drive means being arranged to cause currents to flow in each phase of the motor as required to meet the demanded assistance torque, the control strategy comprising limiting the rate of change of current that is drawn from the electrical supply of the vehicle by the motor in the event that it would otherwise exceed a threshold rate of change.

Abstract: A measurement circuit for measuring at least one of the rotational position and rotational speed of the rotor of an electric motor, typically such as may be used in an electric power assisted steering apparatus, the circuit comprising: first and second inputs for receiving first and second input signals which vary cyclically with the rotational position of the rotor, the first and second input signals at the first and second inputs varying in quadrature with each other; a phase detector circuit; and an observer circuit; in which the observer circuit is arranged to generate estimates indicative of the frequency and phase of the first and second input signals; in which the phase detector circuit is arranged to determine the phase difference between first and second estimated signals varying cyclically and at the frequency indicated by the estimates with a phase difference dependent on the phase difference indicated by the estimates, the first and second estimated signals varying in quadrature with each other on

Abstract: A drive system for a motor includes a drive stage, a control structure arranged to control operation of the drive stage to control drive current to the motor, and a sensor arranged to generate a temperature output indicative of the temperature of a stationary component of the system. The control structure is further arranged to derive from a current indicator, indicative of at least a component of the drive current, and the temperature output, a rotor temperature indicator indicative of the temperature of the motor rotor.

Abstract: An angular velocity sensor for a rotor (2) and method of determining angular velocity in which the position at which event generation means (4) pass sensing means (5) is determined using information from the times at which the event generation means (4) passed the sensing means (5) during at least one previous complete revolution to of the rotor (2). Especially applicable to use of Hall Effect Sensors to detect commutation points of a brushless permanent magnet rotor in an Electric Power Assisted Steering apparatus.

Abstract: An angular velocity sensor for a rotor (2) and method of determining angular velocity in which the position at which event generation means (4) pass sensing means (5) is determined using information from the times at which the event generation means (4) passed the sensing means (5) during at least one previous complete revolution to of the rotor (2). Especially applicable to use of Hall Effect Sensors to detect commutation points of a brushless permanent magnet rotor in an Electric Power Assisted Steering apparatus.