Patent Application
20170106904
This disclosure relates to the field of vehicle controls. More particularly, the disclosure relates to a method of controlling an Electric Power-Assisted Steering (EPAS) system and an Electronic Steering Column Lock (ESCL).
A vehicle steering system is illustrated in
The amount of torque required to steer the vehicle varies depending upon vehicle speed. The torque required can be excessive for many drivers, especially at low vehicle speed. Consequently, some vehicles are equipped with electric power assisted steering (EPAS) systems. Assist motor 26 applies torque to steering column 20 in response to commands from controller 28. When EPAS is active, controller 28 continuously monitors the torque applied to steering column 20, as indicated by torque sensor 30, and commands assist motor 26 to apply a torque in the same direction with a magnitude proportional to the steering column torque. The constant of proportionality may be adjusted based on other sensors, such as vehicle speed sensor 32 or steering angle sensor 34 to adjust the degree of assistance. Typically, more assistance is provided at low speed while less assistance is provided at high speed to preserve tactile feedback to the driver at high speed.
To deter theft, some vehicles include an Electronic Steering Column Lock (ESCL) 36 to limit rotation of the steering wheel except when an authorized driver is present. The presence of an authorized driver is traditionally indicated by insertion of an ignition key.
A vehicle includes a steering column, an Electronic Steering Column Lock (ESCL), an Electronic Power-Assisted Steering system (EPAS), and a controller. The ESCL is engageable to limit rotation of the steering column. The EPAS system includes a sensor configured to detect a torque on the steering column and a motor configured to relieve the torque. The controller is programmed to respond to authentication of an operator by activating the EPAS to relieve a load on the ESCL and then by commanding disengagement of the ESCL. Authentication of the operator may be based on, for example, insertion of a key in an ignition switch, a button press of a wireless key fob, or operation of a driver door. The controller may be further programmed to respond to a request to enter a ready-to-drive state by testing a state of the ESCL and permitting generation of tractive force only if the ESCL is disengaged. The request to enter the ready-to-drive state may be based on rotation of a key in an ignition switch. The controller may also be further programmed to suspend operation of the EPAS and command the ESCL to re-lock if no request to enter the ready-to-drive state is received within a predetermined time after the authentication of the operator.
A method of controlling a vehicle includes responding to authentication of an operator and responding to a request from the operator to enter a ready-to-drive state. The method responds to the authentication of the operator by commanding disengagement of an Electronic Steering Columns Lock (ESCL) and commanding an electric power steering motor to exert torque to relieve load on the ESCL. Authentication of the operator may be based on, for example, insertion of a key in an ignition switch, a button press of a wireless key fob, or operation of a driver door. The method responds to the request to enter the ready-to-drive state by permitting generation of tractive force in response to depression of an accelerator pedal only if the ESCL is disengaged. The request to enter the ready-to-drive state may be based on rotation of a key in an ignition switch. The method may further include suspending operation of the electric power steering motor and commanding the ESCL to re-lock if no request to enter the ready-to-drive state is received within a predetermined time after the authentication of the operator. The method may also firther include responding to the operator request to enter the ready-to-drive state by starting an internal combustion engine.
A controller includes communication channels and control logic. The communications channels receive signals from a steering column torque sensor and a driver authentication system. The communication channels send signals to an an Electronic Steering Column Lock (ESCL) and a power steering motor. The control logic is configured to respond to an authentication signal by commanding the power steering motor to relieve a load on the ESCL as sensed by the steering column torque sensor and by commanding disengagement of the ESCL. The control logic may be further configured to respond to a request to enter a ready-to-drive state by testing a state of the ESCL and permitting generation of tractive force only if the ESCL is disengaged. The control logic may also be further configured to suspend operation of the power steering motor and to command the ESCL to re-lock if no request to enter the ready-to-drive state is received within a predetermined time after receiving the authentication signal.
Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations.
Checking for ESCL unlock at 66 is necessary because there are situations in which the ESCL does not release when commanded to unlock at 62. If steering column 20 is under torsion, then there may be a normal force between pin 50 and one of the teeth 42. The normal force may result in enough friction that the solenoid or motor is unable to translate the carriage 44 from the position of
Some vehicles are equipped with remote starting systems. These systems allow the driver to start the engine from a distance in cold weather such that engine and passenger compartment are warm when the driver enters the vehicle. In response to a remote start event, the vehicle transitions from the unoccupied state, commands the ESCL to unlock, and then starts the engine only if it confirms that the ESCL did unlock. The vehicle does not enter the ready-to-drive state until further events indicate the presence of an authorized driver. If the ESCL stick in the locked condition following a remote start event, the driver typically will not recognize that there is an issue until they enter the car and discover that it is still cold.
It may be undesirable to operate the EPAS system for too long without running the engine. Therefore, a timer is started at 74. If the timer expires while the vehicle is in the authenticated state at 64, the controller stops the EPAS systems at 76, commands the ESCL to lock at 78, and returns to the unoccupied state 60.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and can be desirable for particular applications.
