Autonomous Vehicles - KPIT

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Figure 3: Remote control electronics subsystems In order to prevent any false command attributable to data corruption, this frame has built in checksum error detection feature. This electronics has two separate controllers to share the task of controlling actuators i.e. the data packet containing wireless commands is fed simultaneously to both controllers. These controllers react to specific byte sequences. Figure 3 depicts all subsystems. A. Remote Ignition/Vehicle control: This subsystem automates the ignition controls in the vehicle. To crank the engine, the crank signal needs to be held logical high (~5V) and then should be brought to logical low (~0V). This was achieved by using suitable electromechanical relay with timing control provided by the embedded controller i.e. this served as a parallel ignition option in addition to normal cranking operation through turning of the key. B. Remote Throttle: This subsystem automates throttle operation using an electronic drive circuit. The vehicle implements an electric throttle whereas the operation of throttle lever generates two proportional analog electric signals. These signals are input to engine ECU within the vehicle. The remote throttle circuit proportionally generates two similar proportional analog signals using ADC in response to remote throttle command of 0 to 255 steps. C. Remote Steering System: This system automates steering operation using a DC motor mounted within the steering column by cutting a section of the shaft to accommodate this axially aligned motor. This DC motor is controlled through an H bridge (implemented through suitable capacity Solid State Relays). This H Bridge thus enables direction control. The desired steering position is achieved through following sequence:- (a) Based on correct steering position and command, the corresponding H bridge arm is enabled to turn motor right / left for 10 msec. (b) After 10 msec run, positional feedback is sampled using the 4-20 mA loop shaft position sensor. Since the sensor is noisy, a number of samples are taken to eliminate noise. Repeat with motor running till steering shaft is within acceptable defined positional accuracy (embedded in the code). Compact RIO +12V DC Supply -5V to +5V Remote/Local Selection Power drive Control Circuit Absolute Angle Encoder Motor Figure 4: Remote steering system Mechanical connection to existing steering column D. Remote Parking Brake: This subsystem automates parking brake operation using a motorized screw linear actuator. The extension/retraction of this actuator pulls or releases parking brake cables. The actuator electric motor is electronically controlled to achieve park/release operations. A closed loop control system has been implemented using limit switches to achieve remotely commanded parking brake operation. E. Remote Service Brake: This subsystem automates brake operation using a motorized screw linear actuator, a linear displacement sensor, an additional master cylinder and vacuum booster. The extension/retraction of this actuator activates additional master cylinder connected to existing brake hydraulic lines from vehicle's master cylinder. The actuator electric motor is electronically controlled to achieve brake operations. A closed loop control system has been implemented using linear displacement sensor to achieve remotely commanded brake operation. The system operates the brake in proportion to commands in form of digital inputs 0 to 255 (no brake to full brake). The additional vacuum booster receives engine vacuum. Four valves are used to switch the hydraulic circuits for remote or local operation. 36 TechTalk@KPIT, Volume 6, Issue 4, 2013
DRIVERS BRAKE HYDRAULIC MOTOR Manual Brake fluid valve Manual Brake fluid valve To car brake System Manual Brake fluid valve Manual Brake fluid valve Figure 5: Remote service brake system REMOTE BRAKE HYDRAULIC MOTOR F. Remote Gear Shift: This subsystem automates gear shift operation using a rotary servo actuator tightly coupled with the gear shift lever so that gear would be operated both by driver and remotely. The servo actuator activates vehicle gear shift knob directly. The servo has been housed inside the shift lever. The servo actuator is electronically controlled to achieve gear shifts. Depending upon the desired gear, a suitable PWM is generated to control the position of this DC servo motor. VIII. Conclusion This work aims to replace mechanical and hydraulic actuators of current cars with corresponding electronic control systems thereby reducing human intervention. For that, features such as ignition, throttle, wheel direction, wheel magnitude, remote horn, parking brakes are added. Checksum error detection feature is also included to avoid false commands which result from data corruption. All these features are implemented through different subsystems as mentioned earlier. The complete system is mounted in a single 3U-rack which consists of seven PCBs. In autonomous vehicles perspective, each type of DBW system has its own advantages. Throttle-by-wire can be used for vehicle propulsion. Brake-by-wire provides much better stopping distances than current systems. Steer-by-wire provides lot of space by eliminating the need for steering column. Overall, it has been a very challenging and thus rewarding project. References Figure 6: Remote Gear Shifter VII. Testing of DBW electronics in lab Physical interface of DBW electronics with wireless and vehicle actuators would have meant time taking interface exercise at client site. To shorten the interface exercise, a data packet emulator was designed in-house to simulate inputs to DBW electronics and monitor the corresponding output signals. This emulator not only helped to prove electronics in lab conditions but also allowed fine tuning of embedded algorithms prior actual interface with vehicle. This emulator was also used extensively during integration of the DBW electronics with vehicle at client site. Figure 7: Emulator connected to DBW electronics [1] Steve Rousseau, “Nissan Will Put Drive-By-Wire in 2013 Cars”, October 17, 2012. Available: http://www.popularmechanics.com/cars/news/autoblog/nissan-will-put-drive-by-wire-in-2013-cars 13818193 [2] “Drive by Wire”, 2013. Available: http://en.wikipedia.org/wiki/Drive_by_wire [3] John Fuller, “How Drive-by-wire Technology Works”. Available: http://auto.howstuffworks.com/car-drivingsafety/ safety-regulatory-devices/drive-by-wire.htm [4] Sohel Anwar, Bing Zheng, “Fault Tolerant Control of Drive-By-Wire Systems in Automotive / Combat Ground Vehicles for Improved Performance and Efficiency”. Available: http://groups.engin.umd.umich.edu/vi/w5_ workshops/sohel.pdf [5] “Drive by Wire Technology”. Available: http://www.team-bhp.com/forum/technicalstuff/63437-drive-wire-technology.html [6] “What does drive by wire mean with regards to cars?” Available: http://uk.answers.yahoo.com/question/index? qid=20070703090813AAKcICZ [7] Ian Austen, “Drive by Wire, an Aerospace Solution”, March 29, 2013. Available: http://www.nytimes.com/2013/03/31/automobiles /drive-by-wire-an-aerospace-solution.html?_r=0 [8] Jeremy Laukkonen, “What is Drive-By-Wire Technology?” Available: http://cartech.about.com/od/Safety/a/What-Is- Drive-By-Wire-Technology.htm [9] IBM 3000 VA LCD 3U Rack UPS. Available: http://www-03.ibm.com/systems/x/options/ rackandpower/ups3000va/index.html [10] The RS-232 Standard. Available: http://www.omega.com/techref/pdf/RS-232.pdf TechTalk@KPIT, Volume 6, Issue 4, 2013 537
Page 1 and 2: TechTalk@KPIT a quarterly journal o
Page 3 and 4: Contents Editorial Guest Editorial
Page 5 and 6: Dr. Vinay G. Vaidya CTO KPIT Techno
Page 7 and 8: Journey Without Driver About the Au
Page 9 and 10: A. Stanford Cart - The First Smart
Page 11 and 12: autonomous vehicles in 2004. The Gr
Page 13 and 14: obtained by laser range finder. The
Page 15 and 16: To Be or Not To Be... A Driver Abou
Page 17 and 18: When the autonomous vehicle complet
Page 19 and 20: ultrasonic sensors, etc. provide vi
Page 21 and 22: Scientist Profile Sebastian Thrun S
Page 23 and 24: Seeing Through Sensors About the Au
Page 25 and 26: Figure 1: A robotic Volkswagen Pass
Page 27 and 28: Figure 4: Infrared image of a stree
Page 29 and 30: Bringing Vision to Life About the A
Page 31 and 32: Radar needs an attention, there exi
Page 33 and 34: Sr. No. Table 1: List of patents fi
Page 35 and 36: Drive-By-Wire : A KPIT Case Study A
Page 37: the operational accuracy, it is har
Page 41 and 42: Wired Through Wireless About the Au
Page 43 and 44: FORWARD OBSTACLE DETECTION AND AVOI
Page 45 and 46: Microcontroller Abstraction Layer (
Page 47 and 48: Autonomous Intelligent Vehicles Aut
Page 49 and 50: Inside Connected Vehicle About the
Page 51 and 52: D. Communications security (COMSEC)
Page 53 and 54: security built-in from the very beg
Page 55 and 56: Gazing Through a Crystal Ball About
Page 57 and 58: Thus, from a passenger acceptance a
Page 59 and 60: About KPIT Technologies Limited KPI

Autonomous Vehicles - KPIT

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