Cruise Control Devices

4.1.    CONTROLLER

 

           The controller translates the situation into appropriate actions through brake and pedal and throttle control actions.

 

Depending on the present traffic situation, two types of controls are possible.

 

1.      Speed control

2.      Headway control

 

                    If there is no vehicle presently in front, then the speed is controlled about a set point just as in conventional cruise control. But in order to keep a safe distance between the vehicle s, the headway control is required.

 

5.1ARTIFICIAL COGNITION

 

           The conversion of raw information from sensors to control actions by the two steps:-

 

1.      Analyzing the traffic conditions

2.      Deciding on a particular situation

             The controller translates the desired situation into appropriate control action through brake and throttle actuation.[2]. The controller concept is simplified in the flow-diagram:

Fig 8.Flow diagram of controlling process

 

5.2. EXAMPLE OF ADAPTIVE CRUISE CONTROLLER (MOTOROLA ACC)

       

            The Motorola ACC constitutes a DSP module having MGT5200 which provides a multiply-accumulator. The sensor data such as Radar information, that from camera and an IR sensor are processed in it, to generate the input data for the controller modules like HC12 and MPC565.[6].

                                                             Fig9. Motorola ACC 

 

5.2.1 MPC565

 

                    It is a throttle controller or an engine speed controller. It consists of the following features

 

1. SRAM (1MB to10 MB)

2. FLASH 1MB

3. EEPROM (4KB to 32 KB)

4. Real time clock

5. 4 x UART interfaces

6. 3 X CAN interfaces       

7. 64-bit floating point unit.

 

           The MPC 565 can be programmed to generate the control signals according to the sensor data. ‘The Phycore-MPC 565 developers’ are available to program and develop the desired controller.

           The throttle valve is actuated and the air intake is controlled so the requirement of fuel for the right proportion with the air also increases.  So more fuel is injected and engine speed is changed.

 

5.2.2 HC12

            The HC12 is a breaking controller which receives data from the wheel speed sensors and from the DSP module. It generates the braking control signal.

 

5.2.3 CAN (Control Area Network) BUS

            CAN BUS is the network established between microcontrollers. It is a2-wire, half-duplex, high speed network for high speed high speed applications with short messages. It can theoretically link up to 2032 devices on a network. But today the practical limit is 110 devices. It offers high speed communication rate up to 1Mbits per second and allows real time control. [7].

             Each module in the ACC connected to the CAN is called ‘a node’. All are acting as transceivers. The CAN bus carries data to and from all nodes and provides quicker control transfer to each module.

             The actuator used for throttle control is a solenoid actuator. The signal through the coil can push or pull the plunger.

 

6. CO OPERATIVE ADAPTIVE CRUISE CONTROL [CACC]

 

           Though conventional ACC and SACC are still expensive novelties, the next generation called Cooperative ACC is already being tested. While ACC can respond to the difference between its own behavior and that of the preceding vehicle, the CACC system allows the vehicles to communicate and to work together to avoid collision.[2,4].

           Partners of Advanced  Transit Highways (PATH) –a program of California Department of Transportation and University of California with  companies like Honda conducted an experiment in which three test vehicles used  a communication protocol in which the lead car can broadcast information about its speed, acceleration ,breaking capacity to the rest of the groups in every 20ms.

 

           PATH is dedicated to develop systems that allow cars to set up platoons of vehicles in which the cars communicate with each other by exchanging signals using protocols like Bluetooth.

 

6.1. MAIN POSTULATIONS ABOUT CACC:

          

1.     In CACC mode, the preceding vehicles can communicate actively with the following vehicles so that their speed can be coordinated with each other.

2.     Because communication is quicker, more reliable and responsive compared to autonomous sensing as in ACC.

3.         Because braking rates, breaking capacity and other important information about the vehicles can be exchanged, safer and closer vehicle traffic is possible.

Fig 10.Under CACC, both the leading and following vehicles are electronically “tied” to a virtual reference vehicle, as well as to each other.

 

7. ADVANTAGES

1.      The driver is relieved from the task of careful acceleration, deceleration and braking in congested traffics.

2.      A highly responsive traffic system that adjusts itself to avoid accidents can be developed.

3.      Since the breaking and acceleration are done in a systematic way, the fuel efficiency of the vehicle is increased.

 

DISADVANTAGES

1.      A cheap version is not yet realized.

 

2.      A high market penetration is required if a society of intelligent vehicles is to be formed.

 

3.      Encourages the driver to become careless. It can lead to severe accidents if the system is malfunctioning.

 

4.      The ACC systems yet evolved enable vehicles to cooperate with the other vehicles and hence do not respond directly to the traffic signals.

 

 8. CONCLUSION

 

           The accidents caused by automobiles are injuring lakhs of people every year. The safety measures starting from air bags and seat belts have now reached to ACC, SACC and CACC systems. The researchers of Intelligent Vehicles Initiative in USA and the Ertico program of Europe are working on technologies that may ultimately lead to vehicles that are wrapped in a cocoon of sensors with a 360 –degree view of their surroundings. It will probably take decades, but car accidents may eventually become as rare as plane accidents are now, even though the road laws will have to be changed, upto an extent since the non-human part of the vehicle controlling will become predominant.

 

9. REFERENCES 

1.   Willie D. Jones, “Keeping cars from crashing.”  , IEEE Spectrum September 2001.

 

2.   P.Venhovens, K. Naab and B. Adiprasto, “Stop And Go Cruise Control”, International    Journal of Automotive Technology, Vol.1, No.2, 2000.

 

3.   Martin D. Adams, “Co axial range Measurement-Current trends for Mobile robotic Applications”, IEEE Sensors journal, Vol.2, no.1 Feb.2002.

 

4.   http:// path.Berkeley.edu

 

5. Merril I.Skolnik, “Introduction To RADAR Systems.”Tata Mc Grawhill edition 2001.

 

6. http://motorola /semiconductor.com

 

7. http://www.computer-solutions.co.uk

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