The present invention relates to a hill-hold control (HHC) system, specifically to a hill-hold control system that dynamically adjusts braking pressure to the wheels of a vehicle (and a trailer if the vehicle is towing the trailer) to limit the amount of pressure to what is needed to hold the vehicle in place.
Current HHC functions hold pressure uniformly for all four wheels equally, including trailer brakes if a trailer is connected. The pressure is applied at the level requested by a driver through a brake pedal. There are two shortcomings of this control strategy. First, the strategy does not consider that a driver often over-brakes a vehicle, so more pressure is applied than required. Holding more pressure requires more current to control a switchover valve (USV) coil, thus increasing the durability required for the valve, and introducing noise-vibration-heat (NVH) issues due to valve activation.
Second, the strategy holds pressure in all hydraulic circuits equally, where a hydraulic unit can have different USV valves in different hydraulic circuits (e.g., front wheels versus rear wheels), and the filet it may be optimal to control different wheels using different pressure levels.
The invention provides a system for adaptive hill-hold control for a vehicle. The system includes a first wheel, a first wheel brake, a second wheel, a second wheel brake, a braking, indicator (e.g., a brake pedal), a drive away indicator (e.g., an accelerator), and a controller. The controller is configured to determine when the vehicle is at standstill and the braking indicator indicates that a driver is no longer braking, the controller reducing a pressure on the first wheel brake and a pressure on the second wheel brake to a level that continues to hold the vehicle in place but is less than the pressure the level maintained by a driver. The level at the first wheel brake being different than the level at the second wheel brake.
A method of hill-hold control includes determining that HHC is to be engaged, determining a plurality of parameters about the vehicle and its environment, adjusting a pressure at a first wheel brake based on the parameters, and adjusting a pressure at a second wheel brake based on the parameters. The adjusted pressure at the first wheel brake being different from the pressure at the second wheel brake.
In one embodiment the invention provides a hill-hold control system for a vehicle. The hill-hold control system includes a first wheel brake, a second wheel brake, a braking indicator, a drive away indicator, and a controller. The controller is configured to determine the vehicle is at standstill, detect from the braking indicator that braking is no longer desired, adjust a braking pressure at the first wheel brake, adjust a braking pressure at the second wheel brake, detect from the drive away indicator an operator's desire to drive away, and when the operator's desire to drive away is detected, removing the braking pressure at the first wheel brake and the braking pressure at the second wheel brake.
In another embodiment the invention provides a method of performing hill-hold control for a vehicle. The method includes determining, by a controller, that the vehicle is at standstill, detecting, by the controller, from a braking indicator that braking is no longer desired, adjusting, by the controller, a braking pressure at a first wheel brake, adjusting, by the controller, a braking pressure at a second wheel brake, detecting, by the controller, from a drive away indicator an operator's desire to drive away, and when the operator's desire to drive away is detected, removing, by the controller, the braking pressure at the first wheel brake and the braking pressure at the second wheel brake.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following, description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
An optional trailer 150 is coupled to the rear end of the vehicle by a hitch 155. The trailer 150 includes four wheels 160A, 160B, 160C, and 160D. The front wheels 160A and 160B are coupled to a front axle 165, and the rear wheels 160C and 160D are coupled to a rear axle 170. The trailer 150 can have different numbers of axles (e.g., one) (and, therefore, a different number of wheels), and can be a semi-trailer, a full-size trailer, a boat trailer, a camper, or the like. The trailer 150 also includes brakes 175A-175D at each of the wheels 160A-160D. The brakes can be electric or hydraulic and are controlled by the ECU 125 via electric signals (e.g., to the brake valves individually or to electric motors or actuators).
The controller 130 includes a processor (e.g., a microprocessor, microcontroller, ASIC, DSP, etc.) and memory (e.g., flash, ROM, RAM, EEPROM, etc), which can be internal to the processor, external to the processor, or a combination thereof. The controller 130 also includes other circuits such as input/output circuits and communication circuits.
The controller 130 uses stored values (e.g., combined gross vehicle weight) and calculated values (e.g., gradient) to determine the brake pressures P2-P4. The controller 130 also uses inputs from various sensors (e.g., wheel speed sensors, lateral acceleration sensors) to perform its calculations.
The present patent application claims the benefit of prior filed co-pending U.S. Provisional Patent Application No. 61/817,097, filed on Apr. 29, 2013, the entire content of which is hereby incorporated by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/035819 | 4/29/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2014/179281 | 11/6/2014 | WO | A |
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61817097 | Apr 2013 | US |