Abstract: A vehicle braking system including a controller, in an initial anti-skid cycle, performs a first determination to select a high or a low control mode in accordance with wheel speed parameters. The controller in a second, or subsequent anti-skid cycle, performs a second determination to determine whether a near &mgr; test is to be performed in accordance with wheel speed parameters. The controller consequent upon selection of low control mode performs a near &mgr; test. The near &mgr; test includes performing a rise in the brake pressure and then selecting a high or low mode in accordance with the speed of the wheels resulting from the rise in brake pressure in the near &mgr; test.

Abstract: An active vibration control system having at least two input sensors generating first signals representative of a primary vibration field, a plurality of actuators driven by second signals and producing a secondary vibration field, monitoring sensors responsive to both the primary and secondary vibration fields and producing third signals, and a controller having one output waveform generator for each second signal and responsive to the first signals to generate respective second signals so that vibration is reduced in a chosen region excited by both the primary and secondary fields, the controller being adaptive to adjust the waveform generator outputs to maintain the reduced vibration in this region.

Abstract: An active noise and vibration reduction system for canceling noise in aircraft or other passenger carrying transportation systems which utilizes a series of seat mounted microphones and trim mounted speakers in conjunction with a digital controller with a class-D stage power amplifier and which is synched to the aircraft alternator.

Abstract: A method and mounting for active vibration control of a vibrating body mounted to a supporting body, or vice versa, via a mounting which includes an intermediate body, wherein the intermediate body is substantially passively decoupled from the vibrating body and the supporting body, at least over part of the frequency range over which vibrations are to be controlled, and over said at least part of the vibration frequency range compensating forces are applied to the intermediate body in response to vibrations detected within it.

Abstract: A control system is described for improving continuous dynamical control on the pressure in the outlet or inlet system (3) or both of a machine (1) in order to control the performance of the machine. The system comprises an actuator (4) for varying the pressure in the selected system, a sensor (8) for monitoring the operation of the machine and producing a signal indicative thereof, and control means (5) responsive to the sensor signals for driving the actuator, wherein the control means operates to adjust the machine performance according to predetermined data, to optimise the machine performance. The data may be in a memory (look-up table) or the control means may operate in accordance with an algorithm.

Abstract: A vehicle braking system comprising a controller responsive to wheel speed signals from at least two wheel speed sensors for sensing skid conditions of at least two wheels and for generating skid control instructions; a plurality of wheel brakes responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto; a supply device, comprising a common supply valve, for supplying brake pressure to the brakes from a fluid pressure supply in accordance with a brake operating signal; and a skid controller controlled by the skid control instructions for controlling the brake pressure in a plurality of cycles each of which comprises a pressure reduction phase and a pressure increase phase, and a first comparitor to compare the co-efficient of friction of the lower friction surface with a predetermined threshold, and/or a second comparitor to compare the relative values of the co-efficients of friction of the surfaces with which at least two of the wheels are engaged and a device to operate the s

Abstract: A vehicle braking system has a controller responsive to wheel speed signals for sensing skid conditions of the wheels and for generating skid control instructions. A primary fluid pressure supply includes a fluid pressure source and a fluid pressure reservoir and wheel brakes are responsive to brake pressure supplied to the brakes by supply valves, each of which is adapted to supply fluid brake pressure to a different wheel brake or brakes from the primary supply in accordance with a brake operating signal which can be modulated by skid control units. Each pair of supply valve and skid control unit is adapted to control the fluid pressure of a different wheel brake or brakes. A plurality of brake operating signals are generated, independently of the skid control units, as a function of a brake command signal and a brake operating signal is supplied for each of the supply valves. All the components are connected together so as to be mountable on the vehicle as a discrete unit.

Abstract: A signal processing system, especially for use in vibration control, wherein noise-free signals inductive of the timing of a primary source and of the timing of at least one interfering secondary source of periodic vibrations are provided as inputs, together with a vibration input signal derived from a sensor sampling the vibrations, and wherein the signals are processed to produce an output representative of interference free vibration of the primary source.

Abstract: A signal processing system, especially for use in vibration control, wherein noise-free signals inductive of the timing of a primary source and of the timing of at least one interfering secondary source of periodic vibrations are provided as inputs, together with a vibration input signal derived from a sensor sampling the vibrations, and wherein the signals are processed to produce an output representative of interference free vibration of the primary source.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unsteady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode. Actuators in an actuator array continuously driven by the control signals and produce physical effects in the turbomachine which act counter to the troublesome mode without exciting others.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unstady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coextensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unsteady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode.

Abstract: A control system actively controls at least one troublesome mode of an unsteady motion phenomenon in turbomachinery in order to enable an increase in the operating range of the turbomachinery. For example, rotor blade flutter or rotating stall may be controlled in a turbocompressor. The control system has a control bandwidth which is at least partly coexstensive with the bandwidth of the unsteady motion phenomenon and operates by passing sensor signals related to the unsteady motion phenomenon from a sensor array in the turbomachine to a mode filter which produces a signal or signals which are related to the troublesome mode or modes. The selected mode signals are amplified and phase-shifted by time-variable amounts so as to produce control signals having controlled amplitude and phase relationship to the troublesome mode.

Abstract: An anti-skid braking system for a vehicle comprising a supply of fluid for actuating a plurality of wheel brakes, a skid control unit interposed between the fluid supply and the brakes, sensors to detect the skidding of a plurality of wheels and actuating means responsive to skid signals from the sensors and adapted to actuate the skid control unit to relive the fluid pressure at the brake of the wheel at impending lock by means of a plurality of successive first brake release periods. In order to reduce yawing, when an impending skid condition is detected at one wheel, the skid control unit is arranged to induce second, shorter brake release periods in one or more of the brakes of the wheels not at impending lock.

Abstract: A trailer air braking system has combined spring brake and service brake actuators, and the service brake chambers of the actuators are controlled by a combined emergency relay and modulator valve assembly of known construction. In order to ensure that the spring brake function does not become operative due to a moderate loss in the pressure of the trailer reservoir, such as would occur in the event of an anti-skid test in which the reservoir is isolated from the emergency line and the modulator valve is cycled, a spring brake one-way control valve is inserted into the spring brake circuit leading from the reservoir.

Abstract: Sound control systems which employ sound cancellation may deteriorate due to ageing or change of conditions. The system described is contructed to change according to the sound level at a point where cancellation is to be achieved by sound from a loudspeaker driven by modified signals from a microphone which picks up sounds from a noise source. The signals from the microphone pass through a filter circuit having a transfer function which is controlled by a controller. Signals from the point where cancellation is required, and after modification, from the microphone and the filter circuit are employed by the controller to derive a control signal for the filter circuit.