Abstract: A vehicle speed control system is disclosed in which a signal Vs representing actual vehicle speed is, when the vehicle is running at a desired speed, momentarily fed into, and then stored in, a memory. The memory therefore produces a signal representing desired speed. An error amplifier compares the signal Vm with a signal Vf which represents actual vehicle speed and which is derived from Vs via a filter. Any speed error causes a drive circuit to adjust the throttle of the vehicle engine so as to tend to correct the vehicle speed error. The vehicle-speed-dependent signal Vf is derived from the actual speed of the engine of the vehicle, and this signal is also fed to a comparator which compares it with a reference signal Vr representing an upper or lower limit for engine speed. When the comparison indicates that the engine speed has exceeded the level represented by the reference Vr (e.g.

Abstract: A vehicle speed system is described in which an electrical signal representing actual vehicle speed is compared with a stored signal representing desired vehicle speed. Any speed error is used in a servo loop to generate a control signal which tends to reduce the error to zero. In addition, signals representing the actual and desired vehicle speeds are compared in a comparator unit so as to produce a disabling signal when the actual vehicle speed either exceeds the desired speed by more than a predetermined amount, or falls below the desired speed by more than a predetermined amount, (e.g. because road conditions prevent the vehicle engine from driving the vehicle at or close to the desired speed). This enabling signal is used to switch the control system out of operation.

Abstract: A system for controlling the speed of a motor vehicle comprises means deriving a first electrical signal having a mean level related to the actual speed of the vehicle and an alternating component whose amplitude is related to the actual speed of the vehicle, means storing a second electrical signal having a mean level related to a desired value for the vehicle speed and substantially free of any alternating component, means arranged to compare the first and second electrical signals whereby to produce an error signal having a mean level related to the difference, if any, between the actual and desired vehicle speeds and an alternating component related to the actual vehicle speed, and speed correcting means responsive to the amplitude of the error signal for correcting the actual speed of the vehicle.

Abstract: A vehicle speed control system is disclosed where the vehicle speed is automatically controlled by an electro-pneumatic actuator subjected to the controlled application of sub-atmospheric pressure. A dump valve is normally held closed by an energized electrical coil but opens when the coil is de-energized and connects the actuator to atmosphere and shuts off the control system. The coil is connected to an electrical power source through a disabling switch which is intended to be opened automatically when the driver operates the vehicle brakes and thus overrides the control system. To ensure that the override is effective even if the disabling switch fails to open, a brake-pedal operated switch connects one end of the coil to the same terminal of the power supply as is connected to the other end of the coil by the disabling switch. Therefore, when the brakes are operated both sides of the coil receive the same potential and the coil is de-energized even if the disabling switch fails to open.

Abstract: A system for controlling the speed of a motor vehicle has a speed detector which produces a first electrical signal having a mean level relating to the actual speed of the vehicle and an alternating component whose amplitude is also related to the actual speed of the vehicle. A memory is provided for storing a second electrical signal which has a mean level related to the required vehicle speed and which is substantially free of any alternating component. A comparator compares the first and second electrical signals and therefore produces an error signal which has a mean level corresponding to the difference (if any) between the actual and required vehicle speed and an alternating component related to the actual vehicle speed. A servo responds to the amplitude of the error signal to adjust the actual speed of the vehicle towards the required value.

Abstract: A circuit arrangement is disclosed for protecting against overload electrical equipment such as an electric motor, and any mechanical equipment driven thereby, such as a power actuator. Two light emitting diodes are connected in parallel with each other (with opposite polarity) and in parallel with a series impedance in the power supply circuit of the motor so that each produces a light output in response to an overload current of appropriate polarity in the motor. Associated with each diode is a respective phototransistor which responds to the light output from the associated diode and, via a respective control circuit, operates a switch to interrupt the load current.

Abstract: In an electronic speed responsive system for a motor vehicle, a first voltage proportional to an actual speed of the vehicle is compared with a reference voltage representing a desired cruise speed in order to produce an output error signal related to the difference between said first voltage and said reference voltage, the desired cruise speed is stored in a memory, and a control logic and safety circuit for rendering the system operative and inoperative has a memory cancel facility which cancels the previously memorized cruise speed stored in the memory when a driver of the vehicle makes an action associated with bringing the vehicle into, or preparatory to driving the vehicle from, a parked condition.

Abstract: An actuator device includes a chamber partly bounded by a movable wall and connected to atmosphere through a permanently open orifice and an electromagnetic valve which is maintained in a closed position when de-energized and which controls the connection to said chamber of a volume of gas at other than atmospheric pressure when said valve is open.

Abstract: A speed responsive system, particularly for motor vehicles, whereby the vehicle may be maintained at a predetermined speed. Voltages dependent on vehicle speed and rate of change of speed are compared with a reference voltage representing a desired speed and the resultant output is compared with a periodic signal to produce output pulses of constant frequency and of a width varying with the relative magnitudes of the input voltages. These pulses are applied to an electromagnetic valve which controls the admission of pulses of reduced gas pressure from the vehicle engine inlet manifold to a chamber of variable volume and the resultant movement of a wall of said chamber is employed to control the engine throttle.

Abstract: This invention relates to a speed control system which is operable to maintain a vehicle at a selected speed, or to prevent the vehicle speed dropping below the selected speed. The system includes an electrically-operable pressure control valve which is arranged to be fed with fluid from a source of fluid pressure, for example from the transmission oil pump of an automatic transmission system, an electronic control circuit having a memory in which a selected vehicle speed can be set by the driver, and which supplies a control signal in the form of a variable mark/space ratio pulse train representative of the difference between the actual and selected speeds, to the electrically operable control valve. Fluid pressure from the pump is applied to the smaller working area side of a displaceable differential piston of a differential area piston arrangement, and the larger working area side of the differential piston is connected to the output side of the control valve.