Simulation of the 24GHz Short Range, Automotive ...

European Journal of Scientific Research ISSN 1450-216X Vol.67 No.1 (2011), pp. 75-82 © EuroJournals Publishing, Inc. 2011 http://www.europeanjournalofscientificresearch.com

Simulation of the 24GHz Short Range, Automotive Radar Yahya S. H. Khraisat Electrical and Electronics Department Al-Huson University College/ Al-Balqa' AppliedUniversity P.O. Box 50, 21510, Al-Huson E-mail:[email protected] Abstract In this paper we simulated 24GHz short range, wide band automotive radar. The simulation was done using matlab. The main objective of this work is to reduce traffic accidents and potential danger that faces the driver and the vehicle as a result of the sudden collision. The model consist of six sensors distributed in different sides of the car, these devices provide exact measurement of distance and relative speed of objects in front, beside or behind. Each sensor sends signals to predict, if there is any body around the car to alarm the driver about it. These signals cover distance reach to 30m. However, if the distance between car & object was less than 2 m the car produce sound like alarm to alert the driver of danger near and the driver can present to take the appropriate decision to avoid collision.

Keywords: Simulation, 24GHz Short Range, Wide Band and Automotive Radar.

1. Introduction The main aim of this work is to build system used to warn the driver from pitfalls that causing the crashes, and to make it more safety on the roads. Automotive radar systems are currently leaving research labs and becoming consumer products .Today radar equipment is offered only in high-end car models; however it is anticipated that automotive radar will soon become much more widespread. While in the last couple of years radar sensors have been employed mainly for intelligent cruise controls, the focus nowadays is shifting to active safety systems, where a network of short range radar sensors should monitor immediate surrounding of a vehicle for collision avoidance by issuing a warning or by an automatic intervention. The First experiments in the field of automotive radar took place already in the late 50’s. In the 70’s, more or less intensive radar developments started at microwave frequencies. The activities of the last decades were concentrated mainly on developments at 17 GHz, 24 GHz, 35 GHz, 49 GHz, 60 GHz, and 77 GHz. Even from the early beginning in automotive radar the key driver of all these investigations has been the idea of collision avoidance; this idea has spent enormous motivation for many engineers all over the world to develop smart vehicular radar units.

2. System Block Diagram The automotive radar sensor block diagram is shown in figure 1:

Simulation of the 24GHz Short Range, Automotive Radar

76

Figure 1: Block diagram of the automotive radar sensor.

The Block diagram of the system consists of VCO, pulse repetition frequency (PRF), low noise amplifier (LNA), signal processing (DSP) and two antennas. The 24 GHz Short Range Radar (SRR) sensors are based on a pulsed radar concept. According to Figure 1, the sensor consists of the transmitting path, the receiving path, the control and digital signal processing (DSP) circuits. An object at range R is detected by measuring the elapsed time between a transmitter pulse and a correlated received signal. With this time-gated correlation receiver architecture detection range of 2 to 30 m, a range (object) resolution of 15 cm and a range accuracy of 7.5 cm can be achieved. The individual sensors are connected via a local network to the radar decision unit which on its part is connected via the car controller area network (CAN) bus to the different electronic control units of the car. The complete range up to 30 m can be scanned by setting the adjustable delay for the transmit pulses used for the mixer. The reflected and received pulses are mixed down with the delayed transmit pulses. The sensor output is an analog IF-output signal. Reflecting targets in the sensor’s field of view result in amplitude peaks of integrated pulses energy in the sensor IF-output signal. The corresponding amplitude depends on the target’s radar crosssection and on the signal phase. The sensor IF-output signal is processed using conventional envelope detection methods. For signal baseline adaptation a special filtering is used. The signal difference between IF-output and estimated baseline is then applied to a constant false alarm rate (CFAR) threshold calculation algorithm taking the signal noise into consideration. The noise-adaptive threshold is used for the envelope detection. Range information of all detected targets is then sent to the radar decision unit for the following data fusion and azimuth angle estimation. The 24 GHz technology seems to be the best compromise between today’s component cost and sensor size. Typically, SRR sensors do not measure the angle of detected objects and they have a very broad lateral coverage. Therefore, single antenna elements are sufficient. Vehicular radar systems operating in the 24 GHz range can support a variety of applications and functions to increase traffic safety and convenience. These devices provide exact measurement of distance and relative speed of objects in front, beside or behind the car that can significantly improve the driver’s ability to perceive obstacles or dangerous situations. This category includes collision warning radars, improved airbag activation, and field disturbance sensors, etc. Vehicular radar systems can detect the distance between objects and a vehicle, or can be integrated into the navigation system of the vehicle. Some vehicular radar devices started appearing at car exhibits in luxury cars. 24 GHz SRR sensors are used for safety and convenience functions in the automotive industry. The new SRR uses an angle of 80 degrees to monitor the immediate area up to 30 meters in front of the vehicle. Figure 2 shows the range of LRR (Long Range Radar) and SRR for advanced safety.

77

Yahya S. H. Khraisat Figure 2: Range of LRR and SRR for advanced safety features [1]

3. Signal Processing Modern radars utilize digital signal processors (DSP) to perform various functions within the radar. The signal processing techniques employed by short range radars are very similar to conventional microwave radars. The signal processing difference between the two types of radar is in the radar signal processing philosophy adapted for short range radars, which is to maximize target information that can be processed out of the short range radar signal. Signal processing techniques that come to be associated with short range radars in addition to target detection and ranging include: coherent and noncoherent . Further processing is done for the signals received by the automatic cruise control (ACC) sensor. During object recognition, distance and relative speed of all potential objects are calculated from the information contained in the signals. Distance control requires the precise selection and regulation of a single object out of all the objects detected by the ACC radar system. Selection takes place using information on the vehicle's movement, such as acceleration, wheel speed, steering angle, and yaw rate. Using the host vehicle's speed and the desired time interval, the ACC system calculates the minimum separation distance required. If the distance calculated for the selected object is too small for the current speed, the separation distance is adjusted and deceleration commands are given to the appropriate systems (i.e. engine management, braking). If the following distance is sufficient, the speed is adjusted until the desired speed is reached. To do this, acceleration commands are given to the relevant actuators. The specified time interval and warning signals if the minimum distance is not maintained are shown on the HMI display. The diagram below shows the ACC system components and where they are installed in the vehicle. Figure 3: ACC system components and where they are installed in the vehicle [2]

Note:

Front wheel drive car shown ASR = acceleration slip regulator (traction control) ESP = electronic stability program (electronic stability control)


78

4. Matlab Simulation We employed MATLAB software as a tool to analyze the reference within the unity of the signal processing and knowledge of its characteristics. Then taking advantage of it and passing to control units in the car. 4.1. The Graphical Interface Graphical user interface (GUI) is a user interface built with graphical objects, such as buttons, text fields, sliders, and menus. In general, these objects already have meanings to most computer users. For example, when you move a slider, value changes; when you press an OK button, your settings are applied and the dialog box is dismissed. Of course, to leverage this built-in familiarity, you must be consistent in how you use the various GUI-building components. Applications that provide GUIs are generally easier to learn and use since the person using the application does not need to know what commands are available or how they work. The action that results from a particular user action can be made clear by the design of the interface. The sections that follow describe how to create GUIs with MATLAB. This includes laying out the components, programming them to do specific things in response to user actions, and saving and launching the GUI; in other words, the mechanics of creating GUIs. This documentation does not attempt to cover the "art" of good user interface design, which is an entire field into itself. As we see in the figure 4 it consists of three figures. Figure 4: The graphical interface

The first one shows us the path of the car. The distance traveled is 167 m and the constant speed is 20km\hr. Figure 5: Simulation part on a road.

79

Yahya S. H. Khraisat

The second form contains a block diagram of the sensor guide. The Third Figure shows us the relationship between the input frequency and energy coming from the barrier. Figure 6: Input radio frequency

The screen also contains three command buttons to identify the situations experienced by the vehicle during its path, a situation hard target (static) or moving target (dynamic) either the third button is used for clear the road (figure 7). Figure 7: The command buttons

5. Implementation of System 5.1. Static Obstacle There are two of the obstacles that could hinder the path of the vehicle. The first is static. When the approached car reaches a distance less than 30m, a light warning appears. If the approached car reaches a distance 2m or less, the system will activate a voice alarm. Figure 8: Static input box.


80

Figure 9: Static Obstacle in the Road.

5.2. Dynamic Obstacle If we pushed the button dynamic, the dialog box (figure10), asked to enter the speed of the car. After that two boxes will appear (figure 11). The first one asked to enter the start point while the second asked to enter the end point. When the distance between the vehicle and the obstacle is 2m, a voice warning will be activated. Figure 10: Speed box

Figure 11: Dynamic input boxes.

81

Yahya S. H. Khraisat Figure 12: Dynamic Obstacles in the road.

There are in the list Tools a third option which represents the presence of a fixed barrier and another moving barrier at the same time as shown in the figure (13): Figure 13: Dynamic and static Obstacles in the Road.

5.3. Input Radio Frequency (RF) Input radio frequency part which represents the signal entered to the sensor, consists of two axes; the x axis represents the frequencies entered to the sensor and y axes represents the energy coming from the obstacle. When the vehicle started its movement, the sensor receives a reference as shown in figure 14. Figure 14: Distance is less than 30m and greater than two meter.


82

6. Conclusion It was shown that new radar technology in conjunction with modern digital hardware are well suited for interesting automotive applications meeting the key product parameters like performance, size, price and high update rates. Beyond already introduced ACC radar systems, additional applications can be covered with a multifunctional short range radar network in vehicles. This article shows an interesting sensor concept which can be used for such a system. The system architecture was described and an overview of the signal processing steps was presented. Especially the data fusion part comprises very important parts of the complete processing to achieve high accuracy with this system. Convincing results from realistic street traffic situations confirm the feasibility of the complete system and encouraging further research activities.

References [1] [2] [3] [4]

[5]

[6]

Karl M. Strohm, Hans-Ludwing Bloecher, Robert Schneider, Josef Wenger, Development of Future Short Range Radar Technology, Radar Conference, 2005, EURAD 2005. http:// www.embedded.com/columns/technical sights/189602152? Pgno=3 Merrill Skolnik, Introduction to radar systems, Text book, third edition,2001. Michael Klotz and Herman Rohling, 24 GHz radar sensors for automotive applications, Journal of Telecommunications and information Technology,4/2001, pp.11-14. [On line] www.itl.waw.pl/czasopisma/JTIT/2001/4/11.pdf Karl M. Strohm, Robert Schneder & Josef Wenger, KOKON: A Joint Project for the Development of 79 GHz Automotive Radar Sensors. [Online]. www.kokonproject.com/Library/KOKON IRS 2005 pp.67-101.pdf. Hermann Rohling, Marc-Michael Meinecke, “Waveform Design Principles for Automotive Radar Systems”, 2001 CIE International Conference on Radar, IEEE, China, 2001, pp. 1-4.