Parking aid
As a parking assistance devices or systems are referred to that the parking of a motor vehicle to facilitate, especially in a confined space.
Passive systems
The passive systems include orientation points on the vehicle or in the parking lot, which facilitate orientation, especially recognizing the vehicle's position. In earlier trucks, for example, flexible dipstick rods were often attached to the ends of the front bumper or the front fenders, the tips of which the driver could use for orientation. He couldn't see the ends of the vehicle itself from the cab. In the Mercedes-Benz S-Class of 1991 were due to the unusually large for cars vehicle dimensions dipsticks installed that were sunk in the rear fenders, and engaging the reverse gear exports about eight centimeters.
In the 1960s, the famous tail fins were integrated into the design of large-format luxury vehicles (especially Cadillac and Mercedes-Benz ), which also served as landmarks on the rear of the vehicle.
Starting in the 1950s, so-called were Curb feeler (English. Curb sensor ) installed. These feeler rods either protruded 15 to 30 centimeters horizontally from the sills in front of the front wheel arch, or protruded about 35 centimeters downwards from the front end of the front wheel arch. When they touched the curb, they made a scratching noise that warned the driver against getting closer.
Active systems
There are currently two measurement methods that are used in vehicles. Regardless of the measurement method, the driver is shown the distance either purely acoustically or optically and acoustically, depending on the manufacturer and scope. The purely acoustic version signals the distance via warning tones that turn into a continuous tone. Optical-acoustic systems first optically indicate the approach to an obstacle via LED displays or a graphic on the screen and, if the distance is very short (approx. 30 cm or less), also warn acoustically with quick warning tones up to a continuous warning tone of the "danger". In addition, there are systems that independently carry out all necessary steering maneuvers.
It should be noted here that the concept of parking is referred to as an active "closed system", see also the EVA principle . The sensors used in control technology and measurement technology , in this case ultrasonic sensors , are " passive sensors " due to their characterization . Passive because their parameters are changed by the measured variable. These parameters are converted into electrical signals by primary electronics. An externally supplied auxiliary energy is required. With these it is possible to determine static and quasi-static measured variables, with which these measured variables can be converted into distance values by means of programming.
Passive sensors are therefore not themselves voltage generators and require auxiliary electrical energy . With these sensors, a constant change in the measured variable can be detected, since in the static and quasi-static state, energy can be delivered and recorded at the same time at any time.
See also: Assignment of sensors in active and passive
Ultrasound-based systems
These systems work with ultrasonic sensors that are integrated into the bumpers of a vehicle. A distinction is made between two, four and six-channel systems, which means that two, four or six round sensors, usually painted in the vehicle color, are installed per bumper. The following applies: The higher the number of sensors, the more accurate or more reliable the measurement result, with the width of the vehicle being decisive for the number of sensors required. These sensors send and receive ultrasonic signals and transmit the data obtained to the control unit, which then calculates the distance from the sensor to the obstacle from the ultrasonic signal transit time.
The first functioning ultrasonic parking aid was brought to market in 1982 in the mid-range Toyota Corona sedan on the home market of Japan under the name Back Sonar . Many automobile manufacturers use their own names for their parking systems, such as APS (acoustic parking system) at Audi, PDC (Park Distance Control) at BMW, PARKTRONIC at Mercedes-Benz or ParkPilot at Volkswagen. The system is now used up to a speed of 20 km / h to measure the distance to the vehicle in front and thus serves to avoid rear-end collisions. Ultrasonic parking aids can be disturbed by other ultrasonic sources such as compressed air brakes on trucks and buses or pneumatic hammers. Ultrasonic parking aids are also available for retrofitting.
Radar based systems
A parking aid based on radar was first made possible by a short-range millimeter wave radar. The measuring method is identical to the ultrasonic version; however, radar signals are evaluated here. The advantage is that there is no need for additional ultrasonic sensors in the bumpers, which in turn has the following advantages:
- Costs, technical effort and weight are saved because all the necessary components are "made available" by the distance control system (ACC)
- There are no more visible sensors as the millimeter wave radar measures through the bumper
- When reversing faster, a warning is given in good time of obstacles further away
- The radar measuring system is insensitive to ultrasonic sources
A disadvantage is evident in very heavy rain, when the radar sensors occasionally warn of water running off the bumper.
Self-steering systems
In addition to displaying the distance, there are so-called park steering assistants, which completely take over the steering maneuvers required when parking. The basis for this is an active parking aid as described above and, in addition, an electro-mechanical power steering driven by an electric motor and a measuring sensor system aligned transversely to the direction of travel. Some systems also require a reversing camera so that the driver can select the parking space before the parking maneuver on the camera image displayed on the screen.
After activating the system by pressing a button or falling below a certain speed, sensors measure the parking space at right angles to the direction of travel while driving by. If this is large enough, this is indicated to the driver. The driver now has to stop at a certain distance from the parking space, engage reverse gear and just carefully accelerate, taking the traffic situation into account. The steering assistant now completely takes over steering into and out of the parking space. Once the minimum distance to the rear has been reached, the driver has to bring the vehicle to a standstill, engage forward gear and, depending on the system installed, either move the car forward or simply continue to operate the accelerator and brake. Modern systems are capable of correcting the position in the parking space several times. The necessary steering maneuvers are calculated with the help of clothoid tracks with a constant angular course. Since the driver continues to press the brake and accelerator pedals, he remains responsible.
Camera-based systems
Another way to make parking easier is to use reversing cameras. These are located at the rear of the vehicle and film the area behind the car. They switch themselves on when reverse gear is engaged and show their image on a display in the cockpit. They do not necessarily have to work together with a distance measuring system. Different colored auxiliary lines in the display show the path given by the steering wheel or the area directly behind the car. Other additional functions can be a zoom mode on the trailer coupling area or a mode for parallel parking. An advantage of these cameras is that even particularly low obstacles can be perceived that the parking sensors would not detect.
As an extension to this, there are so-called surround view systems that generate a bird's-eye view of the vehicle, i.e. from above. In addition to a reversing camera, there are further wide-angle cameras on the front and under the two exterior mirrors. All images are digitally rectified and displayed on a monitor in the cockpit. This system, called Around View Monitor , came onto the market for the first time at the end of October 2007 in Nissan Elgrand, Japan . Such systems are also offered by BMW ( Surround View ) and Volkswagen ( Area View ) , among others . Lexus has also developed a simpler system with a camera in the right wing mirror that films the right side of the vehicle, which is difficult to see for the driver. It also works when the mirror is folded down and above all helps to avoid contact with the curb. As a sub-function of the Surround View from BMW, two Side View cameras are used in the front fenders, which are primarily used to monitor cross-traffic in areas with poor visibility.
history
Rainer Buchmann is considered to be the developer of the electronic parking aid . To measure the distance, he used autofocus sensors from Polaroid cameras.
literature
- Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 2001, ISBN 3-528-13114-4 .
- Karl-Heinz Dietsche, Thomas Jäger, Robert Bosch GmbH: Automotive pocket book. 25th edition, Friedr. Vieweg & Sohn Verlag, Wiesbaden, 2003, ISBN 978-3-528-13876-9 .
Web links
- Camera technology in the car: New perspectives on the steering wheel. In: auto, motor und sport online edition. March 30, 2010, accessed April 1, 2010 .
- Handelsblatt: The autopilot takes over when parking
Individual evidence
- ↑ Auto, Motor & Sport, Issue 11/1982, page 62 ( News - The latest in technology )
- ↑ Claudius Maintz: Toyota's parking aid in the test. In: Auto-Bild online edition. May 5, 2006, accessed February 27, 2010 .
- ↑ World premiere: Nissan installs an all-round view monitor for the first time. In: Auto-News online edition. October 16, 2007, accessed January 30, 2011 .
- ↑ Nissan relies on video technology. In: auto, motor und sport online edition. July 10, 2006, accessed February 6, 2010 .
- ↑ Easier parking: Side view camera for the new Lexus RX. In: Auto-News online edition. July 15, 2009, accessed February 27, 2010 .
- ↑ Caterina Schröder: New assistance systems for the 5 Series. (No longer available online.) In: ATZ Online. November 26, 2009, archived from the original on March 9, 2011 ; Retrieved February 27, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Welt.de: Now comes the successor to the rainbow Porsche
