Patent Application
20230121593
The field to which the disclosure generally relates to includes steering, braking, and propulsion systems.
Vehicles typically include steering systems including electric power steering systems.
A number of variations may include a system and method including using differential braking to reduce steering effort during loss of assist.
A number of variations may include a method including monitoring the heath of a steering system comprising an electric steering assist, determining if the electric steering assist has failed, monitoring a driver steering interface to determine the steering angle and torque applied to the steering interface by the driver, and if electric steering system assist has failed then applying brake force or brake torque to one or more roadwheel brakes to counter an aligning force of steering roadwheels due to the failed electric steering assist and so that the torque applied by the driver to steer is less than the torque required to be applied by the driver in the absence of applying brake force or brake torque.
Other illustrative variations within the scope of the invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while disclosing variations of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
Select examples of variations within the scope of the invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the variations is merely illustrative in nature and is in no way intended to limit the scope of the invention, its application, or uses.
A number of variations may include systems and methods using steering wheel and vehicle state information as inputs to a brake-to-steer system at the onset of an electric power steering failure. The brake steer system could be used to reduce the vehicles steering rack loads, thus reducing driver effort, during situations where the electric power steering motor or electric power steering control module is not operational.
A number of variations may be constructed and arranged to address the loss of steering assist in an electric power steering system when the electric power system power pack or electric motor fails. The failure of the electric power system steering assist can result in a large increase in steering effort, especially in situations where the road wheels are at a high angle and steering rack loads are high, resulting in a release of energy when all electric power steering assist force suddenly vanishes. When the power assist fails differential braking may provide lateral capabilities as a unique, diverse support method using a different actuator, such as the brakes, that may be used to manage the force of steering road wheels that naturally tend to move to a zero angle with respect to the longitudinal direction of the vehicle.
In a number of variations when the electric power steering or the electric motor is rendered inoperative, the brake-to-steer system may implement an algorithm that provides brake force or brake torque request to individual roadwheels as a function of vehicle state information which may include at least one of lateral acceleration, yaw rate, wheel speed, or other vehicle state information, and if available, steering sensor measurements such as at least one of torque or angle. Furthermore, estimations of lateral acceleration, yaw rate, steering angle may be derived from inputs from gps, cameras, lidars, and radars may be used in the algorithm, executable by at least one electronic processor, to provide the brake force or brake torque request. The brake force or brake torque requests may be calculated in such a way as to provide enough braking force on the road wheel to counter the aligning torque the driver is resisting while steering the vehicle with a steering assist failure. The application of differential braking will ultimately reduce steering rack loads and reduce necessary driver effort during a loss of assist event. In number of variations, one the steering system is incapable of providing steering input from the driver, an external steering column angle sensor may be used to indicate driver intent. For example, a video system including object recognition capabilities, or an infrared transmitter/receiver system may be utilized to identify features of the driver interface such as a steering wheel and determine movement of the driver interface as the driver's intent to achieve a certain steering angle. An external steering column angle sensor may be provided in a variety of locations in the vehicle including, but not limited to, the instrument panel or the dashboard of the vehicle.
A number of variations may be constructed and arranged to be utilized in the following sequence of events. First, the driver maybe driving a vehicle with a normally functioning electric power steering system and during a turn the electric power system controller or electric power system motor fails or shuts down so that it provides no motor output that can assist the driver in steering the vehicle. The driver may hold or rotate the steering interface to maintain the vehicle curvature or direct the vehicle in a new direction. Lateral acceleration, yaw rate, and vehicle speed data may be sent to the brake-to-steer loss of assist support controller, and if available, signals regarding the steering angle, steering wheel rate, and steering torque are sent to the brake-to-steer loss of assist support controller. At the same time, the loss of assist controller running the brake-to-steer loss of assist support algorithm, or a brakes electric control unit, instantly sends pressure requests as a function of the aforementioned signals to the brakes electric control unit, which distributes the pressure request to all four wheels. The steering effort due to loss of assist is now reduced due to the differential braking forces' reduction of steering rack loads. The driver's intended vehicle speed may be maintained as much as possible, but in general the vehicle gradually slows down due to the differential braking. The differential braking and the vehicle speed may be maintained for long enough for the driver to bring the vehicle to a safe state, but can also remain active to support the driver steering for extended periods of time.
In a number of illustrative variations, a steering interface may comprise a handwheel, a joystick, a trackball, a slider, a throttle, a pushbutton, a toggle switch, a lever, a touchscreen, a mouse, or any other known means of user input.
In a number of illustrative variations, a vehicle may comprise a steering system comprising a steering interface and a steerable propulsion system such as, but not limited to, a steering wheel and road wheels, respectively.
In a number of illustrative variations, a vehicle may include electric braking system constructed and arranged to apply brake force or brake torque to any number of road wheels to assist in steering a vehicle based upon driver steering interface input. The electric braking system may be in operable communication with the steering system and road wheel actuator assembly via at least one controller. The controller may implement any number of systems, including algorithms, for monitoring and controlling propulsion, steering, and braking. According to some variations, the electric braking system may be utilized to apply differential brake force or brake torque to a number of wheels to effectuate lateral motion of the vehicle where a portion of a electric power steering system assist has failed.
In a number of illustrative variations, a brake-to-steer system may utilize a brake-to-steer algorithm that may communicate brake force or brake torque requests to individual wheels as a function of driver steering inputs including steering angle, steering angle rate, and steering torque. The brake-to-steer algorithm may communicate brake force or brake torque requests when the system has detected a power steering assist failure or shut down.
Upon detection of steering assist failure, the system may generate a visual or audio cue to a driver via a human to machine interface integrated into the vehicle. As a non-limiting example, the system may indicate via lamps or alarms that the steering assist has failed. Driver input into the handwheel in the form of steering signals may include steering wheel angle, steering wheel rate, and steering torque may be communicated to a brake-to-steer driver directional controller. The brake-to-steer algorithm may receive said steering signals and calculate brake force or brake torque requests as a function steering signals to an electric braking system electric control unit. An electric braking system may provide a response to driver input of steering signals to reduce the amount of torque the driver must use to steer the vehicle when there is a loss of steering assist. In some cases, the system may provide for control of a vehicles propulsion system and may adjust throttle, speed, acceleration, and the like as needed to maintain driving speed while the brake-to-steer system is operating. In some cases, the system may control a vehicles propulsion system to facilitate gradual slowing of a vehicle while the brake-to-steer system is operating.
According to some variations, a brake-to-steer system may be controlled by an external domain controller constructed and arranged to employ brake-to-steer functionality where a steering system fails entirely.
According to some variations, the brake-to-steer system may function by converting steering requests into a desired yaw rate which may then be converted into a corresponding brake force or brake torque applied to the vehicle brakes in order to create the desired yaw rate with the driver controlling the steering wheel. Brake force or brake torque may be applied to vehicle brakes via an electric braking system. Brake force or brake torque may be applied to individual brake calipers as required.
Converting steering requests to actual yaw rate, and the conversion from your rate to brake force or brake torque may be accomplished via calculation or look up tables. Similarly, converting steering angle to the appropriate brake force or brake torques may also be accomplished via calculation or look up table.
According to some variations, the brake-to-steer system may continuously monitor vehicle speed, yaw rate, and lateral acceleration and may broadcast the availability of the brake-to-steer functionality to various other systems within the vehicle such that, if needed, brake-to-steer functionality may be implemented readily. According to some variations, the availability of the brake-to-steer system may include factoring in vehicle velocity data to determine the availability of the brake-to-steer system.
The following description of variants is only illustrative of components, elements, acts, product, and methods considered to be within the scope of the invention and are not in any way intended to limit such scope by what is specifically disclosed or not expressly set forth. The components, elements, acts, product, and methods as described herein may be combined and rearranged other than as expressly described herein and still are considered to be within the scope of the invention.
Variation 1 may include a method including using differential braking to reduce steering effort during loss or electric power assist of a steering system of a vehicle.
Variation 2 may include a method including monitoring the heath of a steering system comprising an electric steering assist, determining if the electric steering assist has failed, monitoring a driver steering interface to determine the steering angle and torque applied to the steering interface by the driver, and if electric steering system assist has failed then applying brake force or brake torque to one or more roadwheel brakes to counter an aligning force of steering roadwheels due to the failed electric steering assist and so that the torque applied by the driver to steer is less than the torque required to be applied by the driver in the absence of applying brake force or brake torque.
Variation 3 may include a method for use in a vehicle having a controller, a steering system including an electric power assist and a steering sensor, an electric brake system, roadwheels, and a propulsions system, the method comprising: using the brake system to apply differential braking to the roadwheels when the electric power assist has failed.
Variation 4 may include a method as set forth in variation 3 wherein using the brake system to apply differential braking to the roadwheel comprises applying an amount of brake force or brake torque to at least one of the roadwheels to reduce the effort a driver uses to steer the vehicle when the electric power assist has failed.
Variation 5 may include a method as set forth in variation 3 further comprising the causing the propulsion system to provide a forward driving force to at least partial compensate for the differential braking.
Variation 6 may include a method as set forth in variation 3 further comprising determining if the steering sensor has failed and if the steering sensor has failed using a steering angle sensor external to the steering system to determine estimate a steering angle and applying differential braking to the roadwheel based at least in part on the estimated steering angle.
Variation 7 may include a method as set forth in variation 4 wherein the amount of braking pressure applied to one or more of the roadwheels is based at least in part on at least one of one of lateral acceleration or yaw rate of the vehicle.
Variation 8 may include a method as set forth in variation 4 wherein the amount of braking pressure applied to one or more of the roadwheels is based at least in part on at least one of steering interface torque or angle.
Variation 9 may include a method as set forth in variation 4 wherein the amount of braking pressure applied to one or more of the roadwheels is based at least in part on the steerable roadwheel aligning torque when the power steering assist has failed.
Variation 10 may include a method including monitoring the heath of a steering system comprising an electric steering assist, determining if the electric steering assist has failed, monitoring a driver steering interface to determine the steering angle and torque applied to the steering interface by the driver, and if electric steering system assist has failed then applying brake force or brake torque to one or more roadwheel brakes to counter an aligning force of steering roadwheels due to the failed electric steering assist and so that the torque applied by the driver to steer is less than the torque required to be applied by the driver in the absence of applying brake force or brake torque.
Variation 11 may include a controller configured to cause differential braking to the roadwheels of a vehicle when an electric power steering assist of the vehicle has failed.
Variation 12 may include a controller as set forth in variation 11 wherein differential braking comprises applying an amount of brake force or brake torque to at least one of the roadwheels to reduce the effort a driver uses to steer the vehicle when the electric power assist has failed.
Variation 13 may include computer readable media including instructions executable by an electronic processor to carry out the actions comprising: determining if an electric power assist of a steering system of a vehicle has failed or receiving input indicating that the electric power assist of a steering system of a vehicle has failed; if the electric power assist of a steering system of a vehicle has failed, outputting brake force or brake torque request to a brake system to apply an amount of brake force or brake torque to at least one of the roadwheels to reduce the effort a driver uses to steer the vehicle when the electric power assist has failed.
The above description of select variations within the scope of the invention is merely illustrative in nature and, thus, variations or variants thereof are not to be regarded as a departure from the spirit and scope of the invention.
