A pneumatic system comprises a first compressor and associated first air dryer for supplying dried air to a first set of consumers in a main circuit and a second compressor and associated second air dryer for supplying dried air to at least one further consumer through a subsidiary circuit. A protection valve system is provided in the main circuit between the first air dryer and the first set of consumers. A fluid flow path is provided between the main and subsidiary circuits which is selectively openable or closable by a coupling valve to enable the subsidiary circuit to be supplied with pressurized air from the main circuit or to isolate the main and subsidiary circuits.

A vehicle includes wheels, brakes to control speeds of the wheels, and a hydraulic fluid source in fluid communication with the brakes. The vehicle includes a computer storing instructions to determine that speeds of the wheels are zero and actuate the hydraulic fluid source to provide hydraulic fluid to a first set of one or more of the brakes at a first pressure sufficient to maintain the vehicle body at a present position and to provide hydraulic fluid at a volumetric rate to one or more of the brakes not in the first set, and, while providing hydraulic fluid at the volumetric rate to a brake not in the first set, detect second pressures of the brake not in the first set. The instructions include instructions to determine a volume-pressure curve for the brake not in the first set based on the volumetric rate and the second pressures.

A vehicle includes wheels, brakes to control speeds of the wheels, and a hydraulic fluid source in fluid communication with the brakes. The vehicle includes a computer storing instructions to determine that speeds of the wheels are zero and actuate the hydraulic fluid source to provide hydraulic fluid to a first set of one or more of the brakes at a first pressure sufficient to maintain the vehicle body at a present position and to provide hydraulic fluid at a volumetric rate to one or more of the brakes not in the first set, and, while providing hydraulic fluid at the volumetric rate to a brake not in the first set, detect second pressures of the brake not in the first set. The instructions include instructions to determine a volume-pressure curve for the brake not in the first set based on the volumetric rate and the second pressures.

A method for operating a hydraulic braking system including a main brake cylinder and at least one brake circuit, which includes at least one hydraulically actuatable wheel brake, an activatable pressure generating unit configured to generate a hydraulic pressure in the brake circuit when a pressure demand occurs, and an activatable auxiliary pressure generating unit configured to alternatively generate the hydraulic pressure in the brake circuit, the auxiliary pressure generating unit being activated upon recognition of a malfunction in the pressure generating unit to generate the hydraulic pressure. The auxiliary pressure generating unit is assigned an activatable control valve in order to interrupt or establish a connection to the main brake cylinder. The braking system is monitored for the occurrence of a brake demand, and that upon detection of a brake demand, the control valve is activated to interrupt the connection to the main brake cylinder.

A method for operating a hydraulic braking system including a main brake cylinder and at least one brake circuit, which includes at least one hydraulically actuatable wheel brake, an activatable pressure generating unit configured to generate a hydraulic pressure in the brake circuit when a pressure demand occurs, and an activatable auxiliary pressure generating unit configured to alternatively generate the hydraulic pressure in the brake circuit, the auxiliary pressure generating unit being activated upon recognition of a malfunction in the pressure generating unit to generate the hydraulic pressure. The auxiliary pressure generating unit is assigned an activatable control valve in order to interrupt or establish a connection to the main brake cylinder. The braking system is monitored for the occurrence of a brake demand, and that upon detection of a brake demand, the control valve is activated to interrupt the connection to the main brake cylinder.

A hydraulic block for a hydraulic unit for generating brake pressure and regulating brake pressure in a hydraulic vehicle power brake system. The hydraulic block includes a projection that extends the power cylinder bore which passes transversely through the hydraulic block on a large side of the hydraulic block and a projection that extends an anti-rotation guide of a power piston of a power brake pressure generator on an opposite large side of the hydraulic block.

A hydraulic block for a hydraulic unit for generating brake pressure and regulating brake pressure in a hydraulic vehicle power brake system. The hydraulic block includes a projection that extends the power cylinder bore which passes transversely through the hydraulic block on a large side of the hydraulic block and a projection that extends an anti-rotation guide of a power piston of a power brake pressure generator on an opposite large side of the hydraulic block.