Low cost design of parallel parking assist system based on an ultrasonic sensor

International Journal of Automotive Technology, Vol. 11,  No. 3, pp. 409−416 (2010) DOI 10.1007/s12239−010−0050−0

Copyright © 2010 KSAE 1229−9138/2010/052−14

LOW COST DESIGN OF PARALLEL PARKING ASSIST SYSTEM BASED ON AN ULTRASONIC SENSOR

  S. H. JEONG1)*, C. G. CHOI1), J. N. OH1), P. J. YOON1), B. S. KIM2), M. KIM2) and K. H. LEE2)

1)MANDO Central R&D Center, 413-5 Gomae-dong, Giheung-gu, Gyeonggi 449-901, Korea 2)School of Electronic Engineering, Sogang University, Seoul 121-742, Korea

(Received 5 August 2008; Revised 7 December 2009)

ABSTRACT−This paper presents a low cost design and implementation of a parallel parking assist system (PPAS) based on ultrasonic sensors. Generally, a PPAS requires several types of sensors, such as an ultrasonic sensor, camera sensor, radar sensor and laser sensor for parking space detection. However, our proposed PPAS only requires two ultrasonic sensors on the front and lateral sides for parking space detection. Moreover, a steering angle sensor and wheel speed sensor installed in the vehicle are used to obtain vehicle position information for localization in ultrasonic range data. The hardware architecture of the PPAS based on an electronic control unit (ECU) module, sensor modules and a human machine interface (HMI) module was proposed. Moreover, the software architecture of the PPAS is based on system initialization, scheduling, recognition and a control algorithm. In particular, a novel sensor algorithm was proposed to minimize the vehicle corner error of the ultrasonic sensor. A prototype of the PPAS based on the proposed architecture was constructed. The experimental results demonstrate that the implemented prototype is robust and successfully performs parking space detection and automatic steering control. Finally, the low cost design and implementation of the PPAS was possible due to the cheap ultrasonic sensors, simple hardware design and low computational complexity of the proposed algorithm.

KEY WORDS : Parallel parking assist, Ultrasonic sensor, Parking space detection, Parking control

1. INTRODUCTION

Recently, the production and sales of vehicles have rapidly increased compared to the expansion of roads and parking spaces. Narrow parking spaces along with these latest trends can cause inconvenience to many drivers. Therefore, intelligent parking assist systems (IPASs) can be helpful to drivers because the IPAS provides information about the parking space, the ideal parking path and automatic steer- ing control. According to J. D. Power’s “2001 Emerging Technology Study”, 66% of consumers indicated that they were likely to purchase intelligent parking assist products (Frank, 2004).

Until now, the development of IPAS has used several types of range and vision sensors. For example, there are IPASs based on camera sensors (Vestri et al., 2005; Jung et al., 2006), ultrasonic sensors (Santonaka et al., 2006), radar sensors (Stefan and Hermann, 2006) and laser sensors (Hirahara and Ikeuchi, 2003). Among these sensors, IPAS development based on ultrasonic sensors is an important issue to reduce the cost of the system. Moreover, it is also important that an IPAS be constructed using ultrasonic sensors as few as possible in a vehicle.

Generally, the IPASs can be classified into parallel park- ing assist systems (PPASs) and cross parking assist systems

(CPASs), which are called garage parking assist systems or perpendicular parking assist systems. In Europe, VALEO’s PPAS, which is called Park4U, uses 10 ultrasonic sensors: 2 side sensors for parking space detection and 4 rear and 4 front sensors for parking assistance (John, 2006).

In this paper, we propose a low cost PPAS using 2 side ultrasonic sensors. After the proposed PPAS finishes detecting the parking space, it can guide the vehicle to the parking destination without the assistance of additional rear or front sensors.

Our proposed PPAS is shown in Figure 1. First, the scanning process for measuring a parking space is perform- ed when the driver gives the start command. In this pro- cess, the PPAS provides information about the surround- ings to drivers in both a graphical and audible format through the human machine interface (HMI) module. In the

[pic 1]

*Corresponding author. e-mail: erjsh@mando.com        Figure 1. Operation procedure of PPAS.[pic 2]

409

second step, the driver can stop the vehicle and change the gear position into reverse. In the last step, if the scanned space is large enough for parking, the PPAS guides drivers to the parking destination with the EPS control command. Moreover, the PPAS can provide feedback instructions and emergency stop warnings to drivers through the HMI module until the parking procedure is over.

In this paper, the design process and implementation of this PPAS based on ultrasonic sensors are meant for a low cost design. The proposed PPAS prototype was constructed using only two ultrasonic sensors to reduce the cost. We improved the error rate of vehicle corner detection with the proposed novel sensor design and algorithm. Moreover, the simple hardware and software architecture of the PPAS were implemented. The experimental results demonstrate that the proposed prototype is robust and successfully performs parking space detection and automatic steering control. In the conclusion section, we discuss potential improvements and the direction of our future research.

1. SYSTEM DESCRIPTION

In this section, the configuration and state diagram of the proposed PPAS is described. Figure 2 shows the configu- ration of the PPAS. The PPAS consists of 2 ultrasonic sensors, electric power steering (EPS), electronic stability control (ESC), an electronic control unit (ECU), a HMI, a steering angle sensor (SAS), and a wheel speed sensor (WSS).

The ultrasonic sensor, which is connected to ECU by LIN, performs the search operation for parking space detection. The EPS transfers the steering angle information from the SAS to the ECU and receives the control com- mand from ECU by CAN, and then, it performs steering control operation as an actuator. The ESC, which is con- nected to the WSS, provides wheel pulse data to the ECU to estimate the position of the vehicle. The HMI allows communication between the driver and the PPAS. The ECU, which is connected to the EPS, ESC and HMI, can initialize and communicate with these connected devices and operate the algorithm for parking space detection and parking control.  

...