Implementation of CAN –Network in Car Automation

Abstract

This paper presents a methodology to provide an advanced automation in a car. The automation such as carbon monoxide emission detection and real time control, seat belt control, cruise control has been implemented using ARM7.The ARM7 kit and automobile hardware are interface and communicate directly using CAN bus. Rather than tradition scheme of CAN in automation will offer increase portability and efficiency compare with other possible protocols for car automation. The benefits of CAN in achieving automation, over other tradition schemes will offer increase flexibility and expandability for future technology.

Index Terms-Controller Area Network (CAN), Advanced Risc Machine (ARM), Communication Protocols, Network Technology.

1. Introduction

The developed car is a Controller Area Network (CAN) based distributed control system including multiple processors. The Controller Area Network (CAN) architecture was developed for use in automobiles in the 1980’s. It corresponds to the physical and data link layers of the OSI network protocol stack. Manufacturers currently leverage and build upon this architecture to enable on-vehicle sensors, actuators and other commercial electronics to interoperate: communicate between different components, exchange data, and resolve operational dependencies. This paper examines the inner details of CAN.

In today’s automobile industry safety of cars has become a key research issue. In this paper we have given an effective way by which we can increase the car safety by several folds. The practical development of the system proposed by us is being carried out at Loyola Institute Of Technology, India. The single bus based on multiplexing network allows sharing information among various intelligent processors in the framework of multi-master systems. Among single bus network technologies, Controller Area Network (CAN) was developed as in-vehicle network by Bosch in 1980s and has been applied to not only vehicles but also other many distributed systems.

With the increase of number and complex of automotive electronic control system, it is impossible to use traditional point-to-point links method for implementing information exchange between different ECU. This method will bring drawbacks such as the increase of wiring length and weight, redundancy of signal cable, difficulty of examine and repair, lack of electric device protect, impossibility of information sharing and integration, and finally increase the hardness and complexity of system integration.

As a serial communication protocol and defect in-vehicle network standard efficiently supporting distributed real-time control, the ranges of can (controller area network) [1]-[2] application domain is from high speed network to low cost multiplex wiring because of its special capabilities. In passenger car, ECU’s are connected using can with transmission rate up to 1 mbps.

Passenger car control system is real-time networked control system which aims at passenger car as control object, applies in-vehicle network as information transmission channel, uses electronics integration and network integration as basis, information integration and control integration as core, function integration as target, design integration as development method. Supported by automotive electronic control technology, in-vehicle network technology, embedded control technology, sensor technology and intelligent control technology etc, it shares information and achieves correlative real-time control between ECU’s and electric devices according to special control functions.

Information sharing is the basic function of in-vehicle network. Moreover, it is essential to produce uniform control information and achieve information integrated control based on sharing information of different ECU’s so as to enhance the safety, comfort, and added-value of passenger car and improve its service quality and performance. 

2. Background 

Vehicle networking includes in-vehicle networking and inter-vehicle networking. In this paper, we focus on in-vehicle networking, which is usually implemented with a gateway to internetwork the vehicle bus networks. The arm7dtdmislpc2129was used as a gateway [3]. The signals of co level, seat belt control and rotation speed were collected directly from can (controller area network) bus, and velocity and other on-off signals were collected from corresponding sensors. Similarly, the can network was internetworked with a wireless sensor network in [4].

However, the in-vehicle information can be sent outside. An embedded vehicle gateway based on arm (advanced risc machine) was implemented [5], with which lin, can and the internet can be internet worked. The vehicle gateways mentioned above internetwork can bus network by can bus communication module, which is composed of CAN bus controller and transceiver. However, such schemes need to modify vehicles and increase wiring harness, especially for vehicles in use.

Fig. 1.   Physical Can Connection

2.1 Control Area Network 

This section describes elements of the CAN protocol and characteristics of a system model that are needed to formulate a schedulability test. For a complete description of the CAN protocol, see the CAN specification version 2.0 (Bosch, 1991)

2.1.1 CAN protocol and terminology 

CAN is an asynchronous multi-master serial data bus that uses Carrier Sense Multiple Access/Collision Resolution (CSMA/CR) to determine access. CAN was designed as a simple and robust broadcast bus capable of operating at speeds of up to 1 Mbit/s. Message transfer over CAN is controlled by 4 different types of frame: Data frames, Remote Transmit Request (RTR) frames, Overload frames and Error frames. The layout of a standard format data frame is shown below,

 

Fig. 2. Format of Data Frame

Each CAN data frame is required to have a unique identifier. Identifiers may be 11-bit (standard format) or 29-bit (extended format).The identifier serves two purposes beyond simply identifying the message. First, the identifier uses as a priority to determine which message, among those contending for the bus, will be transmitted    next. Second, the identifier may be used by receivers to filters out the messages they are not interested in, and so reduce

The load on the receiver’s host processor. In a can system, normally there is no clock synchronization among the ECU’s (electronic control unit) nodes connected by the can bus. Without synchronization, the clocks of those ECU’s nodes could drift away from each other. A typical clock drift rate of 30 ppm (parts per million) could cause a clock to drift by 108 milliseconds in one hour. The clock drift this large could cause problems in those advanced vehicle control systems. This could be avoided usinghigh overhead clock synchronization in the can system [6].

3. Automation in Car 

3.1. The Carbon monoxide Risks 

The carbon monoxide is a very important toxic gas Because is often present (wherever is fire there is the possibility of forming carbon monoxide). It is formed through the incomplete burning of combustibles. Getting poisoned with CO is the most frequently intoxication with toxic gases. Is enough a concentration by 0,01% (100mg/m3) carbon monoxide in the air to produce a serious in toxication.

3.1.1. Constructive properties of MQ-5 sensor 

This is a simple-to-use  

Carbon Monoxide (CO) 

sensor, suitable for sensing CO concentrations in the air. The MQ-7 can detect CO concentrations anywhere from 20 to 2000ppm.This sensor has a high sensitivity and fast response time. The sensor's output is an analog resistance. The drive circuit is very simple; all you need to do is power the heater coil with 5V, add a load resistance, and connect the output to an ADC. They are used in gas detecting equipment for carbon monoxide (CO) in family and industry or car.

Structure and configuration of MQ-7 gas sensor is shown as Fig. 1 (Configuration A or B), sensor composed by micro AL2O3 ceramic tube, Tin Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-7 have 6 pin ,4 of them are used to fetch signals, and other 2 are used for providing heating current.                 Fig .3. Configuration of MQ-7 sensor 

Fig.4. The typical sensitivity characteristics of the MQ-7 for several gases

 Fig 5.. The typical dependence of the MQ-7 on temperature and humidity

3.1.3. Sensitivity Adjustment        

Resistance value of MQ-7 is difference to various kinds and various concentration gases. So, When using this components, sensitivity adjustment is very necessary. We recommend that you calibrate the Detector for 200ppm CO in air and use value of Load resistance that( RL) about 10 K?(5K? to 47 K?). When accurately measuring, the proper alarm point for the gas detector should be determined after considering the temperature and humidity influence. The sensitivity adjusting program:

A. Connect the sensor to the application circuit.

B. Turn on the power, keep preheating through electricity over 48 hours.

C. Adjust the load resistance RL until you get a signal value which is respond to a certain

Carbon monoxide concentration at the end point of 90 seconds.

D. Adjust the another load resistance RL until you get a signal value which is respond to a CO

Concentration at the end point of 60 seconds .

3.2. Adaptive Cruise Controller 

Basically, the ACC has two operating modes. The first mode is the velocity control mode which is operated when there is no obstacle ahead of the host vehicle. The other is the distance control mode which is operated when the host vehicle finds the obstacle vehicle in front. In the velocity control operation, the vehicle controls its velocity by the ARM7 microcontroller, using proportional and derivative control algorithm with command compensator.

The block diagram is shown in Fig.

              

             Fig.6. Throttle position control block diagram

The proportional controller is used to remove the speed error. The derivative controller is used to reduce the overshoot and oscillation of the velocity response. The control signal of the proportional and derivative control can be described by equation

              Output_{pd =} K_{P +} K_d

For distance control, the authors propose a fuzzy logic

algorithm to control the host vehicle.[6] The distance and the relative velocity between the host vehicle and the obstacle are the inputs of the fuzzy controller which is implemented in a PC. Fuzzy controller is suitable for multi-parameters and nonlinear control problems, and the system transfer function is not required. Human experience and experimental results are used to design the controller. Block diagram of the System is shown in Fig.

 

                     Fig. 7.    Cruise control block diagram

 

                       Fig .8. ACC block diagram

Two input variables are ”relative velocity” and ”Distance error.” The block at the middle represents all the fuzzy inference rules which are the control strategy of the System. The output variables are commands to control brake and velocity set point ratio. The inputs are defined as shown in Fig.

         Fig.9. Fuzzy input definition

               Fig. 10 Fuzzy control block diagram

4. Conclusion and Future work 

A new concept has been proposed for enhancing safety, comfort and added value on a car. CAN bus concept has been implemented with ARM processor for fully automation of car. The advantage over other serial protocol is robust for the automobile industry. CAN also implemented a lot high level features in its physical layer, which makes it easy and cheap to develop this module that can be dropped onto the CAN bus for an automobile.

In further work we can implement additional safety methods depends on public needs. Because of CAN implementation it’s very easy to include new modules on the proposed module