The LHI system simply monitors brake pedal position. The only modification to the brake system is that a very short inactive region of pedal travel is added at the top of the stroke allowing the LHI system to do some or all of the slowing or stopping of the vehicle without using the brakes at all. Aside from the small amount of dead band at the top brakes work normally. Software controlling the LHI system detects wheel slippage as well as a panic stop, and in both conditions the brakes function as normal.
Failure of the LHI system has no effect on the operation of the vehicle. There are three levels of redundancy which prevent the unintended movement (both acceleration or deceleration) of a vehicle because of the LHI system.
As mentioned above, the LHI system can detect wheel slippage and will disable the system when appropriate. Also, the system can detect the potential for slippery conditions and may disable the system if appropriate. Ultimately a driver is responsible for the safe operation of the vehicle by knowing how the vehicle will perform.
When the accumulator is fully charged the controller uses a bypass function to maintain the same braking force on the vehicle without adding more fluid to the accumulator. The maximum setting of this valve will not allow over-pressurization of the high pressure accumulator. Further, the maximum fluid level of the system will not allow the accumulator to be overfilled as the pumps will run out of fluid prior to that event.
The LHI system is a “piggy-back” system – meaning that it is simply added to the existing drivetrain without removing or changing any major components. The system routinely gathers information about the vehicle’s operation (such as speed) from the vehicle, in addition to input received from the driver. The LHI control system simply collects that data and modifies it for use in its own parallel operating control system.
The operator controls the dynamics of the vehicle as they normally would with the brake and accelerator pedals. Although the feel of the vehicle may be slightly different due to increased performance of the brakes and acceleration, the system is designed to be completely transparent to the operator. Most drivers feel the performance changes and adapt their driving style without knowing it, much in the same way as you would drive a Porsche Cayenne differently than a Volkswagen Bug.
The system is based on industrial components used in standard heavy equipment like tractors and industrial machinery. It is designed to be ultra-low maintenance for five years, with one filter change and one bladder change.