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Automatic parallel parking: park assist systems for passenger vehicles
Linköping University, Department of Mechanical Engineering, Fluid and Mechanical Engineering Systems. Linköping University, The Institute of Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis discusses how the problem of parking a passenger car can be solved. There ane numerous obstacles when creating a fully or semi automated system for assisting the parking maneuver. The obstacles range from unobtrusive Man Machine Interface issues to robust algorithms for finding features in sensor data.

Such a system will also have to cope with ever changing environments, most of which will not be discovered during the design phase. Misuse will also be common, since the function is aimed at a mass market - the car buyers. These interesting problem areas is also coupled with the customer value. A car buying customer today aims at feature content and comfort. So for a parking system to survive it needs to be extremely intuitive; the customer value must be discovered during a short test drive with the vehicle. A learning period before the user can operate the system is not feasible.

The work presented here proposes an interesting algorithm for finding parking space features in sensor data collected using ultrasonics. The algorithm, which is based on the well known Hough transform have been proved to be robust in real world experiments.

Furthermore it is also investigated how critical the mount ing of the environment sensing subsystem is. Where should the sensors be placed and where should they be facing to maximize the performance.

Emphasis have also been put on designing a functional architecture that fits in the car development process of today. The implementation of a system in a car must fit in the platform and component reuse is critical to keep cost down.

To test theories developed during the work a prototype car has been used. The prototype is essential to analyze the robustness of algorithms in different parking scenarios. It has also been an invaluable tool when conducting customer surveys to find where the customer value of these kind of systems is.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2007. , 42 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1287
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-41269Local ID: 55422ISBN: 91-85643-14-9 (print)OAI: oai:DiVA.org:liu-41269DiVA: diva2:262120
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-12-12
List of papers
1. A semi-automated parallel parking system for passenger cars
Open this publication in new window or tab >>A semi-automated parallel parking system for passenger cars
2006 (English)In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 220, no 1, 53-65 p.Article in journal (Refereed) Published
Abstract [en]

Car parking has been, and still is, a growing problem, with increasing vehicle sizes in the luxury segment as well as sport-utility vehicles. This is especially true when bearing in mind the confined parking spaces in parking lots and cities. While damage during parking generally does not cause any injury to the passengers, it is costly and annoying. Park assist systems are by no means new on the market, since passive systems which provide longitudinal guidance using ultrasonic distance sensors have been available on the market for a number of years.

The system presented is a semi-automated approach to parallel parking problems, as they frequently occur in European and Asian cities. The challenge during the development of this system was to have as few components as possible added to a standard vehicle, seeking reuse of many of the already built-in functionalities. The result is a system that leaves the longitudinal control of the vehicle to the driver but automates the steering process, and even stops the vehicle when the final parking position is reached.

Keyword
electric steering gear, ultrasonic distance sensors, functional architecture
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-36019 (URN)10.1243/095440705X69650 (DOI)000234903900005 ()29425 (Local ID)29425 (Archive number)29425 (OAI)
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2017-12-13
2. Hough Transform for Parking Space Estimation Using Long Range Ultrasonic Sensors
Open this publication in new window or tab >>Hough Transform for Parking Space Estimation Using Long Range Ultrasonic Sensors
2006 (English)In: SAE Technical Paper, Detroit: SAE , 2006, 2006-01-0810- p.Conference paper, Published paper (Refereed)
Abstract [en]

This paper describes a system for supporting the driver of a passenger car in different parking situations. Todays cars are getting larger in size and the drivers view in both forward and rearward direction is becoming more limited. This fact calls for a system of sensors and algorithms capable of supporting the driver through the parking maneuvre in a safe and smooth way.

The paper presents the development of some of the subsystems in a fully automatic parallel parking system, utilizing ultrasonic ranging sensors for environment mapping. In contrast to existing passive parking aid systems, the ultrasonic range sensors need to have a narrower aperture to be able to map the surroundings properly. This can be accomplished by either increased sensor size or by a higher number of sensors.

The emphasis of the paper is the signal conditioning in the parking system. The Hough-transform along with a statistical CUSUM test are used to find the properties of the target parking space.

The system makes use of hardware components already available in modern cars and a small number of added components. The resulting system is automated, from finding a suitable parking space to maneuvering the car into the parking space, while keeping the driver in authority since the longitudinal control, i.e. throttle and brakes, are still the drivers responsibilities.

The prototype system is implemented in a Volvo S60 which has been modified with an electric power steering unit and an ultrasonic sensor array consisting of a total of six sensors spread out around the vehicle. The electric power steering unit is used for steering wheel angle control when the system is active by adding an external torque to the assist torque normally applied.

Place, publisher, year, edition, pages
Detroit: SAE, 2006
Keyword
automatic parking systems, ultrasonic sensing
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-36020 (URN)10.4271/2006-01-0810 (DOI)29427 (Local ID)29427 (Archive number)29427 (OAI)
Conference
SAE 2006 World Congress & Exhibition. Detroit, USA. April 3-6, 2006
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-12-12
3. A Full Four-Quadrant Hydraulic Steering Actuator Applied to a Fully Automatic Passenger Vehicle Parking System
Open this publication in new window or tab >>A Full Four-Quadrant Hydraulic Steering Actuator Applied to a Fully Automatic Passenger Vehicle Parking System
2006 (English)In: Proceedings of the 4th FPNI-PhD Symposium, Lafayettem, IN, USA: FPNI Fluid Power Net Publications , 2006, 387-396 p.Conference paper, Published paper (Refereed)
Abstract [en]

This project describes how the Active Pinion hydraulic steering system can be used to replace a electric power steering actuator in the Parking Pilot automatic parking system.

Customer demand for fully or semi automatic parking systems in passenger cars, are getting higher with increased cost of parking related body damage repair coupled with restricted rearward sight and the larger dimensions of modern cars. This, however, puts new demands on the steering actuator. An automatic parking system requires full control of the steering servo, which is not possible with current hydraulic actuators. Instead these systems have to rely on electric servos which allow for the needed controllability.

All current electric steering servos have the drawback that it is impossible to use them on anything but small or medium sized cars. Since a parking system can be seen as a premium accessory, which is more likely to attract customers who buy larger cars, this is a major hindrance for the success of automatic parking systems.

A solution to the problem is to construct a controllable variant of the hydraulic steering servo, the Active Pinion. In this concept a small electric pilot motor is added to the traditional hydraulic valve, which adds one additional degree of freedom to the servo, accomplishing full four-quadrant operations.

The project discusses how the Active Pinion concept is introduced in the Parking Pilot parking system and how different demands on the parking system relates to the performance of the actuator. The parking system is installed in a prototype car and simulation of the Active Pinion concept is accomplished with HWIL simulation in a load simulator.

Place, publisher, year, edition, pages
Lafayettem, IN, USA: FPNI Fluid Power Net Publications, 2006
Keyword
hpas, epas, automotive, power steering, automatic parkin, active pinion, parking plot
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-35816 (URN)28628 (Local ID)1-4243-0499-7 (ISBN)28628 (Archive number)28628 (OAI)
Conference
4th FPNI-PhD Symposium. Sarasota, FL, USA, 2006.
Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2013-12-12
4. Ultrasonic Sensor Modeling for Automatic Parallel Parking Systems in Passenger Cars
Open this publication in new window or tab >>Ultrasonic Sensor Modeling for Automatic Parallel Parking Systems in Passenger Cars
2007 (English)In: SAE Technical Paper, 2007, 2007-01-1103- p.Conference paper, Published paper (Refereed)
Abstract [en]

The performance of a parking system is dependent on many factors. One is the placement of the sensors. In this paper a system which uses ultrasonic ranging sensors is considered. The mounting of a ultrasonic sensor on a passenger vehicle is restricted by, among other factors, design, assembly process, enclosure cost and reliability. All of which must be considered when choosing optimal mounting locations.

The basis of this work includes a ray-trace based simulation environment which is used to capture the physical properties of sound traveling through air. The simulation environment together with sensor models, is used to evaluate the effect of different mounting positions on the accuracy of the detection of the parking space. The Hough transform is used here, as well as in the real system, in order to extract the confining lines of the parking space from the sensor measurements. The strength of these lines are then used to compare different sensor mounting locations.

The created simulation environment differs from other work in this area since it tries to capture the physical properties of the sound waves as opposed to the geometric-only approach. The emitted sound pulse is divided into a large number of rays, each with sound properties tied to them. These rays are then traced through a model of the parking space environment, reflections are calculated and finally the summarized echo into the listening sensor is calculated.

The simulation is implemented in 3D Studio MAX which make it relatively easy to create various realistic parking scenarios. An important factor for choosing 3D Studio MAX as the basis of the simulation environment was that it allowed for a new way of modeling ultrasonics using ray-tracing, and at the same time - using the same ray-tracing technology - excellent visualization capabilities.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102488 (URN)10.4271/2007-01-1103 (DOI)
Conference
SAE 2007 World Congress & Exhibition, Detroit, MI, U.S.A., 16th–19th April, 2007
Available from: 2013-12-12 Created: 2013-12-12 Last updated: 2013-12-12

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