Abstract: A drive system, for a multi-phase brushless electric motor comprising a plurality of phases, comprises: a drive circuit including switch means arranged to vary the phase voltage applied to each of the phases so as to switch the motor between a plurality of active states; and control means. The control means is arranged to control the switch means so as to provide PWM control of the phase voltages to control the mechanical output of the motor. The control means is arranged to define a sequence for all of the active states and, for each PWM period, to allocate state times for the states required for that period to generate a desired net voltage, and to order the required states in the same order as they occur in the sequence.

Abstract: A control system for an electric motor comprises processing means arranged to perform a control process which includes monitoring electrical voltages applied to the motor and electrical currents in the motor, and determining from them the rotational position of the motor. The system is further arranged to monitor at least one parameter of the control process thereby to detect a stall condition of the motor.

Abstract: A control system is provided for an AC electric motor which comprises a rotor and a stator and a plurality of phase windings connected in a star formation, each winding having one end connected to a common neutral point and another end arranged to have a terminal voltage applied to it. The control system comprises switching means arranged to control the terminal voltages applied to the windings and control means arranged to control the switching means so as to switch it between a plurality of states in each of a sequence of PWM periods. The control means is further arranged to measure the voltage at the neutral point at sample times within the PWM periods and to generate from the measured voltages an estimation of the rotational position of the rotor.

Abstract: A control system for an electric motor comprises a current sensing means arranged to produce a current sensing output indicative of electric current in the motor, current control means arranged to receive the current sensing output and to output a voltage demand indicative of voltages to be applied to the motor, and voltage demand correction means arranged to generate a correction signal and to use the correction signal and the voltage demand to produce a corrected voltage demand.

Abstract: A method of processing signals in a rotary encoder of the kind which comprises at least one annular track of encoding regions arranged as an alternating pattern of first encoding regions and second encoding regions. The encoder including first and second detectors, each of which is arranged to produce a first alternating output signal as the track of encoding regions rotates about its axis past the detector. The detector identifying a usable pair of transitions and a rejectable pair of transitions and utilizing the pairs of transitions to produce a compensated position measurement for the rotary encoder.

Abstract: A drive system, for a multi-phase brushless electric motor comprising a plurality of phases, comprises: a drive circuit including switch means arranged to vary the phase voltage applied to each of the phases so as to switch the motor between a plurality of active states; and control means. The control means is arranged to control the switch means so as to provide PWM control of the phase voltages to control the mechanical output of the motor. The control means is arranged to define a sequence for all of the active states and, for each PWM period, to allocate state times for the states required for that period to generate a desired net voltage, and to order the required states in the same order as they occur in the sequence.

Abstract: A control system for an electric motor comprises a current sensing means arranged to produce a current sensing output indicative of electric current in the motor, current control means arranged to receive the current sensing output and to output a voltage demand indicative of voltages to be applied to the motor, and current sensing correction means arranged to monitor the voltage demand to measure distortion in the current sensing output and to generate a correction signal which is arranged to correct the distortion.

Abstract: A control system for an electric motor is arranged to determine the position of the motor from at least one electrical parameter by means of a position determining algorithm. It is further arranged to monitor at least one algorithm parameter defined by the algorithm and if the monitored parameter meets a predetermined fault condition to generate a fault indication.

Abstract: A control system for an electric motor is arranged to determine the position of the motor from at least one electrical parameter by means of a position determining algorithm which is reliant on movement of the motor to determine the motor position, and to start up the motor from rest by applying voltages to the motor that are independent of the position of the motor.

Abstract: A method of processing signals in a rotary encoder of the kind which comprises at least one annular track of encoding regions arranged as an alternating pattern of first encoding regions and second encoding regions, comprises providing a first detector at a first fixed position which is arranged to produce a first alternating output signal as the track of encoding regions rotates about its axis past the detector, the alternating signal comprising a series of transitions between a first state corresponding to the detector being aligned with a first encoding region and a second state corresponding to the detector being aligned with second encoding region; providing a second detector at a second fixed position which is arranged to produce a first alternating output signal as the track of encoding regions rotates about its axis past the detector, the alternating signal comprising a series of transitions between a first state corresponding to the detector being aligned with a first encoding region and a second st

Abstract: A control system is provided for an AC electric motor which comprises a rotor and a stator and a plurality of phase windings connected in a star formation, each winding having one end connected to a common neutral point and another end arranged to have a terminal voltage applied to it. The control system comprises switching means arranged to control the terminal voltages applied to the windings and control means arranged to control the switching means so as to switch it between a plurality of states in each of a sequence of PWM periods. The control means is further arranged to measure the voltage at the neutral point at sample times within the PWM periods and to generate from the measured voltages an estimation of the rotational position of the rotor.

Abstract: A control system for an electric motor comprises processing means arranged to perform a control process which includes monitoring electrical voltages applied to the motor and electrical currents in the motor, and determining from them the rotational position of the motor. The system is further arranged to monitor at least one parameter of the control process thereby to detect a stall condition of the motor.

Abstract: A drive system for a three phase brushless AC motor is arranged to optimize the transistor switching pattern to improve power output whilst allowing current measurement in all of the phases using a single sensor. This is achieved by defining voltage demand vectors x where more than two states are required to meet a minimum state time requirement determined by the single sensor method, and calculating three or more state vectors which produce the demanded vector x whilst still allowing single current sensing. Various methods of optimising the PWM pattern so as to give maximum output whilst using single current sensing are also disclosed.

Abstract: A control system for an electric motor is arranged to determine the position of the motor from at least one electrical parameter by means of a position determining algorithm. It is further arranged to monitor at least one algorithm parameter defined by the algorithm and if the monitored parameter meets a predetermined fault condition to generate a fault indication.

Abstract: A control system for an electric motor is arranged to determine the position of the motor from at least one electrical parameter by means of a position determining algorithm which is reliant on movement of the motor to determine the motor position, and to start up the motor from rest by applying voltages to the motor that are independent of the position of the motor.

Abstract: A drive system for a three phase brushless AC motor that is operative to optimize a transistor switching pattern to improve power output while allowing current measurement in all of the phases using a single sensor. This is achieved by defining a voltage demand vector where more than two states are required to meet a minimum state time requirement determined by the single sensor and calculating three or more state vectors that produce the demand vector while still allowing single current sensing.

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.

Abstract: A vehicle (10) includes a suspension system controlled by a suspension controller (12). The system further comprises a user interface unit (18) which includes a series of symbols (26, 28, 30) which remain secret until illuminated and each of which is associated with a particular operating mode of the suspension system. The symbols are illuminated only when their associated mode is available to a user for selection. The operating modes are selected by a series of push button switches (20, 22, 24) which are associated with the symbols (26, 28, 30) and are disabled unless their associated symbol is illuminated.

Abstract: An independent vehicle suspension in which the height change which can be made while the vehicle is stationary is limited so as to prevent the system from having to make too great an associated track change. This prevents the system from becoming locked during a height change due to stiction between the wheels and ground which opposes the track change. The height change is completed when the vehicle is detected as starting to move.