For many drivers, parking a vehicle correctly poses a difficult challenge. Parallel parking in particular can be especially difficult for some drivers. Given the kinematics of the problem and given small tolerance in parking spaces, cars with conventional front wheel steering only are forced to back into a parallel parking space. This “backing up” parking maneuver is more difficult and frustrating than entering headfirst and is also more dangerous due to fact that following traffic must stop well behind the parallel parking space and physically allow the parking vehicle to have room and opportunity to back up which often does not occur. Thus, a system which allows a vehicle to be parallel parked from the headfirst direction is desirable.
An automated parking assist system has been introduced by Toyota® in their 2004 Prius® vehicle. This system utilizes a vision system that displays the available parking spots to the driver. The driver then selects a particular spot and, after positioning the vehicle in the correct staging state, the driver takes his/her hands off the wheel and an electronically controlled steering system turns the front wheels automatically to self-park the vehicle. This pioneering system works well but has several unresolved issues and concerns namely; first, since only the front wheels are steerable, the car must be backed into a spot. Second, the system is totally automatic. While this has its benefits, it typically causes the parking experience to be slow and prone to various diagnostics interrupts. It is also a complex system that may not be appropriate for many vehicles.
An embodiment may comprise a controller assisted method for headfirst parallel parking of a vehicle equipped with a steering wheel and four-wheel steering comprising: gathering coordinate data from sensors which indicate the location of the vehicle, the location of an available parallel parking space, and the locations of obstacles; determining via a controller a course that the vehicle should follow in order to parallel park the vehicle in a headfirst forward direction; and controlling via the controller a front steering system of the vehicle and/or a rear steering system of the vehicle so that the steering systems direct front and/or rear wheels to have the vehicle follow the course in a headfirst direction.
An embodiment may also comprise an apparatus for headfirst parallel parking for use with a vehicle equipped with front and rear wheel steering systems comprising sensors for gathering coordinate data which indicate the location of the vehicle, the location of an available parallel parking space, and the locations of obstacles; a controller for determining a course that the vehicle should follow in order to parallel park the vehicle in a headfirst forward direction wherein the controller controls the front and/or rear wheel steering systems of the vehicle so that the steering systems direct the front and/or rear wheels to have the vehicle follow the course determined in a headfirst direction.
An embodiment may also comprise a computer readable medium with instructions thereon which cause a processor in a vehicle having front and rear steering systems to perform: gathering coordinate data from sensors which indicate the location of the vehicle, a location of an available parallel parking space, and locations of obstacles to parking; determining via a controller a course that the vehicle should follow in order to parallel park the vehicle in a headfirst forward direction; and controlling via the controller the front steering system of the vehicle and/or the rear steering system of the vehicle so that the steering systems direct front and/or rear wheels to have the vehicle follow the course in a headfirst direction.
Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:
To at least avoid the above-mentioned issues, the present disclosure related to assistance for headfirst parallel parking maneuvers (see
As shown in
As is the case with all of the present embodiments, the first embodiment parks the vehicle headfirst. Thus, driver's car 1 needs to be staged at the back of the parking spot alongside a parked car 10 (see
As shown in
Coordinate data may be gathered as follows. A vision system 2 is used to transform the locations of objects such as the parked car 10 and the location of the curb into a suitable coordinate system such as (x, y) coordinates for example (see
Thus in summary, during the staging sequence, the location of the driver's car 1 in relation to the parked car 10 is determined by the controller 4 in a coordinate system using positioning systems such as a GPS and a vision system 2 that can transform and scale visually gathered data to a useful coordinate system such as (x, y) coordinates in order to plot a desired course as shown by the dashed line in
Specifically, from the vision system 2, as shown in
Also, for example, the heading of the car when set in the staging area is recorded as heading angle θ0. Thus, if the car when staged is not perfectly aligned to be parallel with the x-axis which is set to be parallel to the curb line for example, the initial heading deviation can be compensated for by the controller 4 before the target course is determined and before the automatic parking begins. In addition to this open loop control, a closed loop control is added to account for minor (but necessary) adjustments to the steerable wheels.
From the data gathered, the controller 4 may generate a target path y during the staging process. For example (see
where C=tan(θ0). This form will satisfy y=0@x=0 & y=−A@x=D, dy/dx=C@x=0 & dy/dx=0@x=D.
In a traditional car with front steering only, the above target path uniquely corresponds to a (time) profile of the front wheels assuming a given vehicle speed and road conditions. With the advent of steerable rear wheels, however, there could be numerous combinations of front and rear wheel profiles that could achieve the same target path for the vehicle. We will choose to steer the rear wheels in a certain way in relationship to the front wheels. We call this the “bang-bang-stop” approach and we will detail that in our last embodiment. Given this interdependency and the chosen vehicle target path, it would be easy for people skilled in the art to come up with a priori target (or open loop) front angle, δft (see
Closed loop adjustments to δft can be added based on a real time difference between actual and target positions (r and rt, respectively), and between actual and target heading angles (θ and θt, respectively). The algorithms “r logic” and “θ logic” would react to these differences. In their simplest forms, these algorithms could be just some fixed gains. More sophisticated algorithms may be employed if a better response time or other features are demanded. Furthermore, weighting gains gr and gθ, are used to put more or less emphasis on position vs. heading. For example, gr=1 and gθ=0 would mean that our closed loop adjustment will come only due to position errors and any heading errors will be ignored. Other calibrations such as gr=0.25 and gθ=0.75 would also be possible. The sum of these closed loop corrections are added to the a priori (open loop) target for the front wheels, δft. The final command to the front wheels is a combination of open and closed loop commands while the rear wheel commands are determined in an open loop fashion.
Alternatively, closed loop action can be assigned to the rear wheels as well. For example, while the r logic adjustments are done for the front wheels the θ logic adjustments can be done by the rear wheels.
Safety procedures can also be implemented. For example, if the vehicle has stopped with too large of an initial heading angle, the system will not attempt to perform the staging or an automatic parking maneuver. Or if the real time errors between actual (or sensed) position and the target position exceeds a certain threshold, the system may abort automatic parking and revert to a manual operation.
The controller 4 determines how many degrees the front steering system 5 and the rear steering system 6 should be turned to in order for the reference point 3 to follow the desired course as shown in the dashed lines of
Next, the driver confirms visually that the desired parking spot is sufficient, and starts the automatic parking maneuver by releasing his foot from the brake pedal with the “drive” mode selected on an automatic transmission for example. Now with the driver's hands taken off the steering wheel, the controller 4 actively commands to the front steering system 5 and the rear steering system 6 in order for the driver's car 1 to follow the desired course. The automatic parking maneuver ends when the vehicle is parked in the desired position and the driver puts his foot on the brake pedal. The driver can interrupt the motion at any time by placing his foot on the brake. When the brake is released, the system will continue to attempt to park the driver's car 1 until the reference point 3 reaches the desired position. Thus, the driver can regulate the speed of the maneuver with brake pedal as a safety precaution. The system can also be turned off by pushing the system “on/off” button at any time, or exceeding a preset threshold on the gas or brake pedals.
The second embodiment system is termed herein “Semi Automatic” see
The third embodiment system is termed herein “Non-Automatic” (see
Advantagously, a “bang-bang-stop” control can be provided. In this case, the rear wheels are steered to their maximum or “banged” (opposing the front wheels) and are held at that position while the driver is going to one side of the center steering wheel position. The rear wheels are steered to their maximum or banged in the other direction when the driver turns the steering wheel or handwheel HW passes the centered or neutral position “straight ahead.” If there is a third crossing of the center position by the driver, the rear wheels are best commanded to their zero position. This is shown in logic of
It is also noted that based on a target path such as the thick dashed line in
For safety reasons an embodiment would also incorporate means to limit the maximum vehicle rate or speed in MPH to below 5 MPH such as brake control or throttle control.
The gathering of coordinate data from sensors may be gathered from, but is not limited to: GPS units, vision sensors, yaw rate sensors, inertial sensors, velocity sensors, speed sensors, wheel position sensors, steering angle position sensors, handwheel sensors, geared sensors, steering wheel sensors, radar sensors, lidar sensors, CCD sensors, electrical sensors, mechanical sensors, magnetic sensors, photo sensors, impact sensors, torque sensors or infrared sensors or other suitable sensors.
The course determined by the controller (see “r” in
The capabilities of the present invention may be implemented in software, firmware, hardware or some combination thereof. As one example, one or more aspects of the present invention can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately.
Additionally, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform the capabilities of the present invention can be provided.
The flow diagrams depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the invention.
While the preferred embodiment to the invention has been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the invention.
This application claims priority to U.S. provisional application No. 60/652,047 filed Feb. 11, 2005, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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60652047 | Feb 2005 | US |