Slip Control Boost Overview: Notes

The slip control boost system is a hydraulic braking system which is capable of supplying boosted braking, slip control functions, and regenerative brake blending.

The system is made up of two major assemblies, the master cylinder assemble (no vacuum booster is used), and the electro-hydraulic control unit. Also included are various internal and external sensors used for system control and fault isolation.

The master cylinder assembly is made up of a reservoir and an master cylinder with primary, and secondary pistons. A pedal travel transducer is attached to the master cylinder assembly.

The electro-hydraulic control unit is used to electronically control pressure at the wheels. A pump and accumulator supply hydraulic brake fluid pressure to perform braking applications. A proportional supply valve controls the flow and pressure of fluid from the accumulator to the brakes. Standard digital slip control valves and, in some cases, proportional versions of them, are used to control pressures at the brakes independently for slip control. The regenerative axle isolation valves along with the proportional relief valve are used in regenerative brake blending situations. A simulator, consisting of a plunger, spring, orifice, and check valve provide the force and travel feedback to the driver through the master cylinder. There are four internal pressure transducers, master cylinder pressure, high pressure accumulator, boost pressure, and regenerative axle circuit pressure sensors.